US3815094A

US3815094A - Electron beam type computer output on microfilm printer

Info

Publication number: US3815094A
Application number: US00098259A
Authority: US
Inventors: D Smith
Original assignee: Micro-Bit Corp
Current assignee: Micro-Bit Corp
Priority date: 1970-12-15
Filing date: 1970-12-15
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04

Abstract

An electron beam type computer output on microfilm printer employing an electron beam writing apparatus having an evacuated housing closed by a Lenard window fabricated from a differentially etched bulk supporting member through which the electron beam is directed for permitting egress out of the evacuated housing into a higher pressure ambient atmosphere surrounding the housing with a minimum of beam scattering while maintaining the integrity of the evacuated space within the housing. The thin window portion consists of a material different than the bulk supporting member and not susceptible to the etchant employed to form the window in the supporting bulky member and may be formed by chemical reaction with the bulk supporting member from the class of materials consisting of SiSiO2; Al-Al2O3; Ta-TaO; Ti-TiO; Si-SiC; Si-SiN; Al2O3 on Si; and the like. The thin SiO2, Al2O3, TaO, TiO, etc window layer preferably first is formed to a desired thickness on the surface of a bulk supporting member by chemical reaction with the thin elongated window then being etched in the bulk supporting member by an etchant which does not react on the thin window layer. The electron beam type computer output on microfilm printer further includes an electron sensitive microfilm recording medium and transport means supporting the microfilm recording medium immediately adjacent the thin window portion of the electron beam recording apparatus. Printer control circuit means are coupled to the electron beam writing apparatus and the transport means for controlling the operation thereof. A character generator supplied from a buffer memory unit and controlled by the printer control circuit controls deflection and beam blanking of the electron beam recording apparatus. Use of the buffer memory allows the EBeam COM printer to be easily interfaced with any computer system as a standard plug compatible peripheral equipment.

Description

United States Patent [191. Smith 1 June 4, 1974 ELECTRON BEAM TYPE COMPUTER OUTPUT ON MICROFILM PRINTER Donald 0. Smith, Lexington. Mass.

22 Filed: Dec.15,l970

211 App]. No.: 98,259

[75] Inventor:

[52] U.S. Cl 340/l72.5, 340/173 CR [5 I] Int. Cl. l-lOlj 37/22 [58] Field of Search 340/l72.5, 173, 173.2, 340/173 'TP; 95/45 1561 References Cited UNITED STATES PATENTS 3.041.930 7/1962 Davidson. Jr. 95/45 R X 3.047.871 7/1962 Hider et a1. 95/45 R X 3.121.216 2/1964 Wolfe et a1. 340/173 TP 3.167.747 1/1965 Hughes et a1. 340/173 TP 3.184.753 5/1965 Koster 95/45 R X 3.195.112 7/1965 Hughes et a1.... 340/173 TP 3.278.683 10/1966 Ashby et a1. 95/45 R X 3.324.457 6/1967 Ogle et a1. 340/1725 3.501.235 3/1970 Anton et al 340/173 TP 3.534.338 10/1970 Christensen et al. 340/1725 3.540.361 11/1970 Schira 95/45 R 3.710.352 1/1973 Smith et a1 340/1732 Primary Examiner-Paul J. Henon Assistant Examiner-Paul R. Woods Attorney, Agent. or Firm-Charles W. Helzer [57] ABSTRACT An electron beam type computer output on microfilm printer employing an electron beam writing apparatus having an evacuated housing closed by a Lenard window fabricated from a differentially etched bulk supporting member through which the electron beam is directed for permitting egress out of the evacuated housing into a higher pressure ambient atmosphere surrounding the housing with a minimum of beam scattering while maintaining the integrity of the evacuated space within the housing. The thin window portion consists of a material different than the bulk supporting member and not susceptible to the etchant employed to form the window in the supporting bulky member and may be formed by chemical reaction with the bulk supporting member from the class of materials consisting of Si-SiO AlAl,O;,; Ta-TaO; Ti- TiO', Si-SiC; Si-SiN; A1 0 on Si; and the like. The thin SiO A1 0 TaO, TiO. etc window layer preferably first is formed to a desired thickness on the surface of a bulk supporting member by chemical re action with the thin elongated window then being etched in the bulk supporting member by an etchant which does not react on the thin window layer. The electron beam type computer output on microfilm printer further includes an electron sensitive microfilm recording medium and transport means supporting the microfilm recording medium immediately adjacent the thin window portion of the electron beam recording apparatus. Printer control circuit means are coupled to the electron beam writing apparatus and the transport means for controlling the operation thereof. A character generator supplied from a buffer memory unit and controlled by the printer control circuit controls deflection and beam blanking of the electron beam recording apparatus. Use of the buffer memory allows the E-Beam COM printer to be easily interfaced with any computer system as a standard plug compatible peripheral equipment.

38 Claims, 9 Drawing Figures 49 a FER /Q{ 03mm" a '05 5mm streams F a [ll m svsral was REGISTER m 48 gm cumt t mm cuscx T0 00mm COITROL accent 1 EL must I T STATUS m men were PATENTEDJuu 4- m4 3.8151394 SHEET 2 0F 4 LENSB DEFLECTOR CHARACTER GENERATOR FLECTOR A CHARACTER POSlTION INV Enron DONALD 0. SMITH ABCDEFGH IJKLMNOP QRSTUVWX YZI23456 7890') [II FIG 3A In fld/zs ATTORNEY PATENTEDJUII 4 m4 3.815094 SHEET w 4 FIG. 4B

FROM FIG. 4A

CRT

POWER SUPPLY RAMP GENERATOR I ONTAL IL VER GRID DRIVER IOI | 8 l FROM $3? 0000 P76. 46

t 1 O O O O O O O o 7 0000 0000 2 :3 2 z L 0000 0000 IHVENTOR g DONALD 0. SMITH C JOOO 3 8 00 0 amt/es Q} feez ATTORNEY ELECTRON BEAM TYPE COMPUTER OUTPUT ON MICROFILM PRINTER BACKGROUND OF THE INVENTION 1. Field of invention This invention relates to a new and improved electron beam type of computer output on microfilm printer.

More particularly, the invention relates to a computer output printer of the type which records data to be printed-out from a computer system on a microfilm recording medium and which employs an electron beam recording apparatus having a novel Lenard window which allows the electron beam to be brought out into ambient atmospheric conditions for direct recording of electron images on the microfilm without undue scattering of the beam and while maintaining the integrity of the evacuated electron beam source.

2. Prior Art Situation The end product of most computer systems traditionally has been hard copy print-outs which are usually in human readable form. These hard copy print-outs traditionally have been obtained from impact line printers such as drum printers, chain printers and oscillating bar printers. In all of these devices, the printing technique employed involves an on-the-fly" approach in which high print speeds are achieved by extremely rapid hammer action against continuously moving type elements. The print cycle is the time required to load a buffer storage servicing the printer, decode its contents, print one line including hammer action and recoil, and space the paper. In this process, all characters move past the print hammers, the character to be printed is selected by decoding, and a fast action hammer, controlled by an actuator, presses the paper against the type slugs at the exact moment the required character is in correct position. The limiting factors on printing speed with impact type printers. tend to be mechanical in nature and are associated with paper handling and paper motion. Hence, current impact printers approach the upper limit of the fastest printing speed of which impact type printers inherently are capable and this is on the order of 2.000 alphanumeric character lines per minute.

Computer systems generally consist of three basic components: input devices for entering data into the system, a processing unit for processing the data, and output devices for recording the process results. The throughput of a computer system is governed by the slowest component. In most computer system applications, the processing unit and the input device transfer rates are sufficiently fast so that the output device of the system is the limiting factor in the overall system speed.

Output devices can consist of card punches, paper tape punches, magnetic tape unit, or line printers. All of these units can accept information transmitted from the processing unit and record the information as directed by the programmed instructions. However, only the line printer has the capability of rendering the information human readable. The other type of output devices require separate off line" stations to transcribe the data to human readable form. Such stations are expensive and perform only a single function; hence, most "off line" stations have been replaced by small computing stations comprising buffer storage and peripheral control units. The buffer storage unit is placed between the input-output devices and the processing unit and data is transferred on command from the processing unit to the bufier storage. and then from the buffer storage to the printer. The time required for transfer of data between the processing unit and the buffer storage is only a fraction of the time that otherwise would be required to transfer the data directly from the processing unit to the printer. Hence. the line printer can be directed to record the contents of the buffer storage while the processing unit is free to continue with the processing for the next data manipulatron.

The prime prerequisites for a good printer are a high transfer rate or speed expressed as lines per minute and print quality. As stated above, impact printers using some kind of mechanically driven type bar currently are used extensively where human readable print-out is required. Because impact printers require mechaincal movement and are therefore speed limited, non-impact printers which require no mechanical movement to achieve print-out have come into wide spread use. Since speed is the major consideration as discussed above, non-impact printers have become quite popular.

Non-impact printers usually employ techniques such as photographic, xerograpic and cathode-ray tube methods where the final copy normally is in the form of microfilm or specially treated paper. Where a hard copy is required, the microfilm image normally is transferred to specially treated paper. This is a maor disadvantage of known non-impact printers in that the specially treated paper is expensive and often of unknown consistency. In addition. the known non-impact printers are incapable of producing more than one copy of the print-out. However, non-impact printers offer the potential of extremely high printing speeds at comparatively low costs. It is this high speed low cost factor that has caused a recent spin of activity in computeroutput to microfilm printing.

Recently, computer-output microfilmers (COM) have come into widespread use becaue of their high speed low cost factor and due to the fact that they convert machine readable data directly to eye-legible information on microfilm through the medium of an appropriate microfilm reader. These COM printers constitute a new class of peripheral output devices for use with computer systems,

The COM printing process can be briefly summarized as follows:

I. The COM printer sends a signal to the central processing unit of the computer system when it is ready to print. Alternatively, the COM printer could be used with a magnetic tape unit to print out results previously recorded on a magnetic tape. However, for the purposes of the present discussion, it will be assumed that the COM printer is on line and printing results supplied thereto directly from the central processing unit of the computer. The information transmitted by the processing unit contains instructions interspersed with the data concerning procesures for frame advance, retrieval code, forms projections and the like.

2. The output data to be printed out is fed into a character generator where it is converted into deflection voltages for controlling an electron beam for a cathode ray tube (CRT), a photo-diode matrix or the like.

3. The controlled electron beam is used to construct the desired character on the face of a CRT or directly onto a film.

4. The image if not written directly into the microfilm recording medium, is displayed on the fluorescent face of a CRT and photographed.

5. The microfilm subsequently is developed and distributed for copying, printing or viewing in a microfilm reader.

In general, the most interesting aspect of COM has been the revelation to the electronic data processing industry that microfilm can be the heart of a sophisticated information storage and retrieval system that can be and is used on day-to-day active records. rather than dead storage. In addition, COM is the first practical device that can produce original data at a lower price than it could be produced on paper.

The two basic techniques employed by known COM printer systems are optics and electron beams. Most of the known systems use an electron beam in a CRT to produce a light image that then is focused on the microfilm. Currently. there are approximately 24 commercially available COM printer systems of this general type. Another known COM printer system writes directly into the microfilm with an electron beam while yet another employs fiber optic devices responsive to a photo-diode matrix to achieve recording on the microfilm. At least one of these devices operates like a standard plug compatible peripheral equipment for use with known computer systems.

In the past, microfilm information sotrage systems were limited by their incapacity to record information on film at high speed and their inability to easily restructure, reorganize and update information. COM has given to microfilm these abilities. However, with respect to existing COM printer systems, these known systems all have certain deficiencies in one respect or another. Those systems employing CRTs for convertmg the data to light images that then are focused on the microfilm produce poor quality images due to low resolution. insufficient intensity and the like. While one known electron beam COM printer system which records directly on microfilm with electron images, over comes certain of these problems, because of its nature and design to bring the electron beam directly to the microfilm recording medium, it is difficult and costly to maintain. This is due to the fact that the microfilm is brought into the electron beam recording space through seals which also of necessity lowers the evacuation of the space. This in turn results in the burning out of cathode sources for the electron beam because of the poor vacuum in which they operate. Others of the devices are incapable of producing good quality images because of limited intensity or limited resolution.

SUMMARY OF THE lNVENTlON It is therefore a primary object of the present invention to provide a new and improved electron beam type computer output on microfilm printer (hereinafter referred to as an EBCOM printer) and electron beam recording apparatus having high speed printing capabilities together with good resolution and high intensity to provide good quality microfilm prints, and which possesses long cathode life for its electron beam source.

Another object of the invention is to provide an EBCOM printer having the above characteristics which is adapted for use with a wide variety of character formation techinques and is usable with a large number of different microfilm recording mediums both as to composition (i.e., wet silver. dry silver. etc.) and form (i.e.. tape. card. drum. disk. etc.).

A further object of the invention is the provision of an EBCOM printer employing a new recording techinque involving the partial recording of a character with each individual scan of a recording electron beam while mechanically moving the microfilm recording medium transversely to the direction of the scanning electron beam to accomplish raster recording of characters in a line after a series of repetitive scans.

A still further object of the invention is the provision of an EBCOM printer as set forth above which in actuality comprises a combined controller-EBCOM printer having a buffer memory that allows it to be easily interfaced with any known computer system as a standard, plug-in compatible peripheral equipment and having a print-out speed on the order of 10,000 to 25.000 lines per minute so that it places little or no constraints on the high speed processing capability of a computer system with which it is used as a printout device.

In practicing the invention, the EBCOM printer system is provided employing an electron beam apparaus having a source of electrons disposed within an evacuated housing together with means for directing the electrons in the form of a beam toward one of the walls of the housing. A Lenard window fabricated from a differentially etched bulk supporting member is secured to the wall of the evacuated housing and has an extremely thin window portion through which the electron beam is directed for permitting egress of the electron beam out of the evacuated housing into higher pressure ambient conditions surrounding the housing with a minimum of beam scattering while maintaining the integrity of the evacuated space within the housing. The thin window portion consists of a material different than the bulk supporting member and is not susceptible to the etchant employed to form the window in the supporting bulk member. Preferably, the thin window ortion is formed by chemical reaction with the bulk supporting member. lt should be noted at this point in the description that the terms thin window portion" and window" are considered to be synonymous while the bulk supporting member forms the window frame. The bulk supporting member and thin window portion maybe from the class of materials comprising Si-SiO AlAl,O TaTaO, Tl-TiO, Si-SiC, Si-SiN. A1 0 on Si and the like. In a preferred embodiment of the invention, the differentially etched bulk supporting member is silicon (Si) and the thin window portion is comprised by a thin layer of silicon dioxide (SiO previously formed to a desired thickness on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein.

The electron beam apparatus is of the type including deflecting means for deflecting the electron beam along at least one axis of movement and the this window portion comprises an elongated thin slit having its long axis extending in the direction of deflection of the electron beam. The EBCOM printer system is further comprised by transport means for supporting a mic rofilm recording medium immediately adjacent the elongated thin slit window portion and is designed to move the microfilm recording medium in a direction transverse to the longitudinal axis of the elongated thin slit window. A printer control circuit is coupled to and controls the electron beam apparatus and the transport means together with a character generator which also is coupled to the electron beam apparatus. The arrangement is such that the electron beam is caused to repetitively scan along the longitudinal axis of the elongated thin slit window while the character generator blanks the beam at appropriate points to provide character formatting and spacing. If desired. X-Y deflection of the electron beam can be provided whereby an entire character is written out as the electron beam is scanned across the width of the microfilm recording tape.

In a preferred form of an EBCOM printer constructed in accordance with the invention, each character recorded on the microfilm tape recording medium is comprised of a matrix of horizontal co-extending and vertical transversely placed dots measured with respect to the longitudinal axis of the elongated tin slit window and with the equivalent of a predetermined number of dot spacings between characters in each line and between each line of characters. Placement of a dot in the formation of a character in a line of characters and the spacing thereof with respect to other dots comprising each character and line of characters is controlled by appropriate manipulation of the beam deflection means and the beam blanking means of the electron beam recording apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and many of the attendant advantages of this invention will be appreciated more readily as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference character, and wherein:

FIG. 1 is an overall functional block diagram of a EBC OM printer system constructed in accordance with the invention;

FIGS. 1A and 1B are partial cross-sectional views of novel Lenard window constructions used with the EBCOM printer system of FIG. 1, and constructed in accordance with the invention;

FIG. 2 is a schematic functional diagram of one form of electron beam recording apparatus constructed in accordance with the teachings of the present invention and usable in the EB COM printer system of FIG. 1;

FIG. 3 is a functional schematic diagram of still a different form of E-beam recording apparatus constructed in accordance with the invention and usable with the EB COM printer system of FIG. 1;

FIG. 3A illustrates a character mask employed in the embodiment of the invention shown in F IG. 3; and

FIGS. 4A and 4B are functional block diagrams of still a different form of EB COM printer system constructed in accordance with the invention and providing a novel recording technique employing partial character recording during each individual scan of an electron beam writing apparatus employing the novel Lenard window structure of the invention as depicted in FIG. 4C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 1. Electron Beam Recording Apparatus FIG. I is a functional block diagram of a new and improved EB COM printer constructed in accordance with the invention. The heart of the EB COM printer is comprised by an electron beam recording apparatus 10 contained within an evacuated housing indicated by the dotted lines 11 and including an electron beam source comprised by the cathode 12, control grid 13, and anode l4, maintained at suitable potentials supplied thereto from a power supply 15. Electrons produced by sources 12-14 are formed in the shape of a beam indicated by 16, by a suitable focusing lens arrangement l7, and directed towards a wall of the evacuated housing 11.

The wall of evacuated housing 11 against which the electron beam 16 is directed has a new and improved Lenard window structure shown generally at 18 secured thereto. FIG. 1A of the drawings is an enlarged cross-sectional view of the Lenard window structure 18 and illustrates its construction in greater detail. The Lenard window structure is fabricated from a differentially etched bulk supporting member 19, which may be formed from one of the class of materials comprising silicon (Si), aluminum (Al), tantalum (Ta) and titanium (Ti). The differentially etched bulk supporting member 19, is secured to the wall of the evacuated housing 11 in a vacuum tight manner, and includes a window area or opening 21 etched therein over which an extremely thin window portion 22 extends. The window portion 22 is formed from the class of materials comprising silicon dioxide Si0 aluminum oxide (Al- O Tantalum oxide (TaO), titanium oxide (TiO) silicon nitride (SiN), silicon carbide (SiC) or the like porperly mated to the characteristics of the particular material used to form the bulk supporting member 19. The electron beam 16, is directed against and through the thin window portion 22, for permitting egress of the electron beam out of the evacuated housing 11 into a higher pressure ambient space surrounding the housing. Because of the particular nature and construction of the novel Lenard window structure 18, this is achieved with a minimum of electron beam scattering while at the same time maintaining the integrity of the evacuated space within the housing 11. As a consequence of this arrangement, the electron beam may be used to directly record electron images on a microfilm recording medium shown at 23 without substantial impairment of the degree of vacuum of the evacuated space within housing 11. This in turn results in greatly extended cathode life for the electron beam sources 12-14.

From a consideration of the materials listed in the above description of the construction of Lenard window 18, it will be appreciated that the thin window portion 22 consists of a material different than the bulk supporting member 19 which serves as a frame for holding the window portion 22 and defines the window opening 21 through which the electron beam passes in order to impinge upon and pass through the thin window portion 22 without undue scattering or attenuation. A further desirable characteristic of the material of the thin window portion 22, is that it can be previously formed on the thick bulk supporting member 19 to a predetermined thickness preferably through an appropriate chemical reaction process involving the surface of the bulk supporting member so as to result in a material which is not susceptible to an etchant employed to fonn the window area 21 in the bulk supporting member 19. For this purpose, it is desirable that the differentially etched bulk supporting member 19 and thin window portion 22, be from the class of materials comprising silicon-silicon dioxide (Si-$02); aluminum-aluminum oxide (AlAl O;,); tantalum-tantalum oxide (Ta-TaO); titanium-titanium oxide (TiTiO); Si--SiN; Si--SiC; M or Si; or the like. While any of these materials may be suitable the preferred construction is for the differentially etched bulk supporting member to be comprised of silicon and the thin window portion 22 be comprised of a thin layer of silicon dioxide (SiO previously formed to a desired thickness of the surface of the bulk supporting silicon member I9 by chemical reaction prior to the etching of the window area 21 in the bulk supporting member 19. For a more detailed description of suitable SiO layer growing techniques and subsequent selective etching to form thin SiO windows that could be employed in the manner taught by the instant invention, reference is made to an article entitled Film Stripping Techniques for Making Thin Silicon Window" by E. Tannenbaum, of the Bell Telephone Laboratories, Inc., appearing in the Journal of Applied Physics Vol 3l, pg. 940 I960) and to an article entitled Gas Permeation Study and lmperfection Detection of Thermally Grown and Deposited Thin Silicon Dioxide Films" by S. W. Ing, R. E. Morrison and J. E. Sandor of the Semiconductor Products Department, General Electric Company, Syracuse, N.Y., reported in the Journal of the Electro Chemical Society, Mar. I962, pg. 221 through 226. Still other suitable microcircuit techniques suitable for use with the present invention are reported in unclassilied Report No. AD6037 l S entitled Integrated Silicon Device Technology, Vol. III Photo Engraving by J. J. Wortman et al., prepared by the Research Triangle Institute of Durham, NC, dated January 1964 and available through the Defense Documentation Center of the Defense Supply Agency of the US. Government.

From a consideration of the above-noted references, it will be appreciated that the production of the Lenard window structure 18 can be achieved with well known and established micro-circuit masking and etching techniques employed in the semiconductor industry. It should be noted that only the window area 21, is required to be etched to form the thin window portion 22 of SiO leaving the rest of the wafer as a bulk supporting chamber that can be used as a sturdy mounting or window frame for securing the window to the evacuated housing I I. The thinness of the window portion 22 is subject to excellent control during the SiO layer growing operation by controlling the extent of thermal oxidation, etc so as to produce an SiO layer on the order of l micron or less down to the order of 500 angstrom units in thickness. The etchant used to form the window area 21, which may be hot chlorine, then will not attack the underlying thin window portion 22 of SiO;. Thus, it will be seen that control of the thickness of the resulting window portion 22 is separately performed in one operation and the subsequent etching operation need not be the subject of fine control to result in a desired thickness window layer 22 since the etchant used in forming the window area 21 through the bulk supporting member 19, does not attack the window portion 22, that is. it is differential in its action. The other materials listed above are also known to possess differential etching characteristics and can be employed in a similar manner to form suitable Lenard window structures for use in practicing the invention.

Where silicon or other similar semiconductor materials are used as the bulk supporting member 19. it may be desirable to include a thin conducting layer shown as phantom at 19A to keep the Lenard window struc' ture at substantial ground or other potential. This is particularly required if the sides of the bulk supporting member defining the thin window area are to be used for blanking part of a fan-shaped beam that is deflected along the longitudinal axis of the window, and with respect to which the sides of the window intercept and blank part of the beam as will be described more fully hereinafter. The conductive coating 19A may extend completely over the back or electron source side of the supporting member 19 including the thin window portion 22. If desired this conductive layer could be formed of chromium by vaporization to a thickness on the order of 3,000-l0,000 angstrom thick, and could have an even smaller window area shown at 21A etched therein by a suitable etchant which does not attack the underlying layer of SiO or other similar material from which the window portion 22 is formed. Alternatively, the conductive layer 19A could be made sufficiently thin so that it does not unduly attenuate or scatter the electron beam and could cover the entire back surface of the thin window portion 22.

Another considerable advantage to the Lenard window constructed in the above described manner from a monocrystaline supporting member such as silicon, is provided by the uniformly straight lines and sloping sides that are characteristic of the window aperture or opening 21 and that are formed during the etching operation due to the planes of the monocrystaline body. As a consequence, extremely fine, straight uniformly shaped window openings can be fabricated in accordance with this technique which are particularly advantageous for use with electron optic recording systems of the type herein disclosed.

FIG. 1B is a partial cross-sectional view of an alternative form of Lenard window constructed in accordance with the invention. In FIG. 1B the thin window portion 22a is recessed a few microns (on the order of Z-IO microns) below the surface of the supporting bulk member of silicon 19. By constructing the Lenard window in this manner, the thin target window portion 22 can be protected from abrasion and damage from the microfilm recording medium 23 which is allowed to contact and ride along the lower surface of the supporting bulk member 19 in order to minimize the space between the microfilm 23 and target window portion 22. In fabricating the structure of FIG. 1B, the lower recession is first introduced by suitably etching for only a short period of time the bottom surface of the supporting bulk member 19. Thereafter the entire bottom surface is oxidized to form a layer of SiO of about I,()OO5,000 angstrom units thick but may be even as low as 500 angstrom units in thickness. A thin layer of long wearing, low friction conductive material such as chromium (Cr) then is deposited by evaporation, sputtering, etc over the layer of SiO, to a thickness of about 3,000-l0,000 angstrom units thick. The function of this layer 198 is to provide a good wearing interface between the Lenard window structure and the recording microfilm tape 23 and also to act as a lubricating or low friction surface for engaging the microfilm.

An extremely fine exit opening shown at 218 maybe provided in the protective layer 198 by etching this layer through to the underlying SiO thin window layer 22 with an etchant that does not attack the SiO;, layer 22. This opening could be made on the order of lmicrons wide, and can act as a limiting one-dimensional aperture fo the electron beam 16. This very thin exit aperture 218 can be etched in the layer 198 with equal or better precision and with greater ease than if one tried to form the narrow recession in the supporting bulk member of silicon 19 with equal precision. The thin slit 21B thus obtained can then act as the limiting one-dimensional aperture for the electron beam thereby allowing for greater recording resolution. Furthermore, it is not too difficult to produce an electron beam having a pinched l shape beam and align the beam so that the center of the pinched l is focussed on the thin window portion 22. ln this manner an extremely fine electron beam spot of comparatively high intensity can be obtained for providing high resolution recordings on the microfilm recording medium 23.

An alternative method for forming the Lenard target window structure shown in FIG. 18 would be first to apply an overlaying film such as 19 of chromium completely over the bottom surface of the supporting bulk member of silicon 19 which previously has been oxidized to a thickness of the order of two microns. Then a thin recession is etched in the overlaying layer 198 and through the underlying oxidized layer to expose the surface of the supporting bulk member of silicon. At this point the structure is re-oxidized to form a new SiO layer to the desired thickness for the thin window portion 22. Subsequently, the back or upper side of the bulk supporting member of silicon is differentially etched through to the last mentioned SiO, layer and the conductive layer 19A then formed in the manner shown. The conductive layer 19A should be sufficiently thin so that it does not attenuate or scatter the electron beam 16. if desired. an opening such as that shown at 21A in FIG. 1A could be formed in the conductive layer 19A of the structure shown in FIG. ]B.

it is desirable that the thickness of the window portion 22. be maintained as thin as possible to minimize both beam attenuation due to the window and scattering effects of the window on the beam. Accordingly, it is desirable that the window portion 22 have a thick ness on the order of 500 to 2,000 angstrom units and possibly even less if the window area 21 can be made sufficiently thin. The transmittance of SiO is excellent for a thickness even as high as 2.000 angstrom units for a kilovolt electron beam. Of course for a kilovolt beam or some higher value than [0 kilovolts, the transmittance would be that much better. However a more serious problem exists due to the scattering of the beam by the window portion. A rough value estimated from the published literature indicates that :1 l0 kilovolt electron beam is scattered on the order of 18 when transmitted through a 2,000 angstrom unit thick SiO film. This can be translated into meaning that a beam spot size on the order of 3 to 5 microns impinging on the SiO, Lenard window, would be double that size due to scattering at a distance of about 1 l microns away from the window. Again, of course, a higher energy beam such as a 20 kilovolt beam would experience much less scattering. In either event, however, there is little or no problem to control the spacing between the microfilm recording medium 23 and the Si0 window 22 so as not to exceed 10 to 15 microns. With a spacing on this order. the transmittance of the electron beam through the air presents no problem whatsoever since the representative figure obtained from the literature indicates that a 10 kv beam loses about l0 percent of its energy after travelling a distance of 300 microns in air. To avoid even this kind of a loss, it would be possible to include the portion of the microfilm recording medium 23 on which the electron beam impinges in a partially evacuated space or enclosure indicated by the dotted lines 25 which can be evacuated by a vacuum pump 26, an d allow the microfilm recording medium in the form of a tape to be brought into the space through suitable sealed openings indicated at 27 and 28. The provision of the partially evacuated space within housing 25 would also tend to alleviate somewhat the stresses on the thin SiO Lenard window portion 22 in comparison to the stresses that would be obtained ifthe beam were brought directly out into ambient atmospheric conditions. This would be particularly advantageous for those applications where it is desired to have a quite wide target window portion 22. Alternatively, the window structure of FIG. 18 could be employed to minimize spacing between film 23 and the target window 22.

With respect to the microfilm recording medium 23, any known microfilm recording material can be em ployed which is electron sensitive. For example. the conventional silver halide photographic film composition requiring wet development processes could be employed. A dry silver recording microfilm employing thermal processing for development purposes is preferred, however, because of the relative simplicity and speed with which dry silver can be heated and developed. It is also possible to use diazo, vesicular and Kalvar R film recording mediums, or for that matter any other known high resolution recording film which is electron sensitive. For the purpose of the instant disclosure, it will be assumed however that a dry silver, diazo or vesicular recording film is employed using thermal processing. The form of the recording microfilm medium 23 is unimportant and may comprise tape, cards. drums, disk or any other known structural arrangement whereby unexposed areas of the recording medium sequentially may be brought under the electron beam 16 emanating from the Lenard window portion 22. In the instant disclosure, the microfilm recording medium 23 is in the form of a tape transported between a take-up spool 31 and a play-out spool 32, driven by suitable drive motors and clutch arrangements controlled by a motor controller in the conventional manner. It is preferred that the take-up and drive spool have at least two forward speeds, one for recording and the other for fast advance to a desired area on the tape as well as a reverse, although the latter capability is not required. The take-up and play-out of the mocrofilm tape 23 may be either continuous at a desired recording speed related to the number of lines per minute to be recorded, or it may be stepped in nature through the use of suitable stepping motors. However, if the microfilm 23 is to be moved and stopped between each sweep of the electron beam (as described hereinafter), printing speed will probably be reduced by about l,500 lines per minute which may be unacceptable depending upon the type of recording technique employed. if such a stepping motor arrangement is used. however, the printer should be capable of buffering several lines of data to be printed in order not to place a constraint on the computer system read-out.

2. Character Genration and Beam Deflection The alphanumeric characters to be recorded on the mocrofilm tape 23, can be generated in a number of different ways. There are three commonly employed techniques now being used in known COM printers. These employ a shaped beam. a dot matrix and a stroke. Other known techniques not so widely used include generation of symbols by a programmed Control of the electron beam deflection, the use of Lissajous techniques, dot generation, line generation and the television type raster technique. Generation of characters is most generally done by the application of a computer-originated signal to a character generator module which decodes the signal and cooperates with a printer controller to control operation of the deflection and blanking circuit of a CRT. By such arrangements, the electron beam is moved to a proper location and then intensified to cause a visual output to be generated.

The following list of known character generation techniques is not considered to be exhaustive but is merely set forth as explanatory of a number of known character generation techniques usable with the present invention by appropriate design of the printer controller and character generator circuitry.

FIXED STROKE GENERATOR With this technique the electron beam is caused to follow a predetermined path composed of a number of PROGRAMMED STROKE GENERATOR With this technique, each stroke of the electron beam is characterized by 7 bits of data. Three bits con trol the X component of the stroke, 3 bits control the Y component and one bit controls the blanking. Of the 3 bits for each component, one controls the sign and two control the amplitude. Thus. each stroke describes a motion of the beam. Several strokes are connected to form characters. This method is capable of generating quite good characters, but at least 16 strokes or ll2 bits of space are required in the character generator memory for each character to be recorded. Hence. the electronic circuitry required to implement this technique becomes elaborate and somewhat expensive.

SlMPLE DOT MATRlX In this technique. the electron beam scans a raster either horizontal or vertical covering an area of the recording medium where a character is to be formed. The character is generated by gating the electron beam (i.e. intensifying it at the appropriate points in the matrix where dots are to be formed. A 5 X 7 matrix is the minimum required and a 7 X 9 matrix would be preferred for good quality character recording. Again, as the number of dots is increased, cost and trace time likewise is increased.

MOVABLE DOT MATRIX This method is similar to the dot matrix but allows more freedom in the dot location. In addition to blanking information. position information is supplied for each dot to be recorded. The scan of the electron beam then no longer is a simple raster. The technique is more expensive but generates quite good quality characters and requires little scan time. For dry-process film recording mediums. the use of this technique may be advantageous.

MONOSCOPE OR SHAPED BEAM A monoscope is a tube which contains a character mask. A coarse deflection system mask deflects the electron beam to the desired character and a fine deflection system scans the character. By passing the electron beam through the mask having various symbols and characters cut into it, the electron beam is shaped" into a desired symbol. The beam is then deflected to a desired position by normal deflection techniques. The computer requirements for such a system are simply positional information stored in memory for each symbol. Data is the form ofa symbol code and XY position are required. A limit of 64 symbols requiring a character mask containing 8 X 8 array of characters can be used with each character being identified by a 6 bit 3 bits for the X position and 3 bits for the Y position) signal.

3. Printer-Controller Control Circuitry Suitable printer-controller control circuitry for operating the electron beam recording apparatus in accor' dance with any of the above-listed as well as other known techniques, is shown generally in block diagram form to the left of the evacuated housing. The control circuitry is comprised by a printer control logic module 41 supplied from a buffer memory 42 which may comprise a MOS dynamic shift register having a storage capacity on the order of words with each word comprising 9 bits. The buffer memory 42 is supplied with output data from a computer system central processing unit which data is to be printed out by the EBCOM printer. For this purpose. the memory 42 will be supplied an edited line of data plus a few control characters from the computer. The control characters will operate through the control logic module 41 to advance the microfilm tape 23 through the medium of the film advance control subcircuit 43, project and print forms through the medium of a form selector and projector 44 under the control of a forms projection control subcircuit 45; develop the recorded images on the microfilm tape 23 by a heat source or other suitable development system 46 under the control of a heat control subcircuit 47 together with controlling the performance of other necessary functions under the central control of the control logic module 41. The output from the buffer memory 42 is supplied to the control logic module 41 through a parity checker and control decode section 48. The output from the buffer memory 42 also is supplied to a character generator module 49 that may comprise a MOS read only memory or core read only memory having a capacity on the order of 10,000 hits such as the TMS 2400 integrated read-only memory circuit chip manufactured and sold by the Texas Instrument Co. The character generator 49 also is under the control of the control logic module 41 which serves to clock appropriate character forming signals out of the character generator 49 for supply to the electron beam recording apparatus 11. Control logic module 41 therefore serves as a central control employing a relatively simple set of logic elements for developing the necessary clocks and control signals to be used as command signals for the various components of the E COM printer system and also for communicating with the computer system central processing unit to inform it when additional lines of data are to be supplied. detection of errors, etc.

Depending upon the particular character formation techniques employed, the printer-controller control circuitry would be structured appropriately to implement the desired technique. For the purpose of the present disclosure, it will be assumed that the EB COM printer system shown in FIG. I will record a line of full characters across the width of the microfilm recording type 23 one line at a time for each scan of the electron beam. Hence. it will be necessary that the target window portion 22 by sufficiently wide to accommodate the height of a character. In FIG. 1 it is assumed that the longitudinal dimension of tape 23 extends between the

spools

31 and 32 and the width of the tape extends into the plane of the paper. Accordingly, it will be appreciated that as shown in FIG. I, the viewer is looking at a cross sectional view of the target window portion 22 and that this target window portion will be in the form of an elongated thin slit extending into the plane of the paper.

With the electron beam recording apparatus structured in the manner described in the preceding paragraph. the apparatus would be designed to include deflecting means shown generally at for deflecting the electron beam along at least the longitudinal axis of the elongated thin slit target window 22. Further. since the target window is sufficiently wide to accommodate the height of a character, additional means shown in FIG. I as comprising a micro deflection system 51 are pro vided for deflecting the beam 16 along XY axes to cause it to trace out the character patterns to be recorded. This coupled with appropriate blanking (enhancement) of the electron beam by the application of suitable control signals to the control grid 13, will result in the formation of electron images on the surfaces of the microfilm recording type 23 in accordance with the characters desired to be recorded. For this purpose fine X and Y control voltages are supplied to the micro deflection system 51 from a fine X and Y deflection control voltage subcircuit 52 that in turn is controlled from the character generator 49. For certain of the techniques it would be possible to control the fine deflection control circuit 52 directly from the control logic module 41 depending of course upon the writing technique employed. For either arrangement. the control logic module 41 supplies the required slow trace. fast retrace (reset) deflection signals required to cause the electron beam I6 to be scanned back and forth across the entire length of the elongated thin slit target window portion 22. These voltages are supplied through a course deflection control subcircuit 53 to the course deflection means 20 which may comprise electromagnetic deflection coils. I t is of course possible to employ eleectrostatic deflection plates in place of the electro-magnetic coils illustrated in FIG. 1. Beam blanking (enhancement) control signals are supplied to the control grid I3 of the electron beam recording apparatus from a suitable CRT gate driver control subcircuit 54 that in turn is supplied from the character generator circuit 49. For a more detailed description of suitable circuitry for the construction of the CRT gate driver, deflection circuits. stepping motor control. digital-analog conversion circuitry, buffer memories and the like, reference is made to a number of issued United States patents and publications relating to the electron beam recording art such as U.S. Pat. No. 3,195,112 W. C. Hughes. et al.. issued .luly l3. I965; U.S. Pat. No. 3,167,747 W. C. Hughes. et al.. issued Jan. 26. 1965; and U.S. Pat. No. 3.l2l.2l6 J. D. Wolf. et al.. issued Feb. 1 l. 1964. All of these patents include detailed descriptions of the construction and interconnection of a number of elemental subcircuits illustrated in block diagram form in the present disclosure and readily could be utilized by one skilled in the art to fabricate an EBCOM printer system according to the present invention.

FIG. 2 is a schematic. sectional view of an electron beam recording apparatus suitable for use with the EB COM printer system of FIG. I where it is desired to perform character writing in accordance with the movable dot matrix technique described briefly above. For this purpose, the electron beam recording apparatus 11 shown diagramatically in FIG. 2 includes all of the elements listed in connection with the electron beam recording apparatus ll of FIG. 1. In FIG. 2 however the electron beam recording apparatus is shown in a different plane so that in effect the viewer is looking at a cross sectional view of the microfilm recording medium 23. Thus. it will be appreciated that the view shown in FIG. 2 has been rotated substantially with respect to the view shown in FIG. 1. Also in FIG. 2 the construction of the micro-deflection system 51 has been illustrated in greater detail.

The micro-deflection system 51 is comprised by a linear array of 22 micro-deflection lenslets which are arranged along the longitudinal axis of the elongated Lenard target window portion 22. The construction of the micro-deflection lenslets has been described in detail in a number of published articles, and hence has not been illustrated in constructional detail. Briefly. however, the micro-deflection lenslets (sometimes referred to in the art as fly's eye lenslets) are fabricated from a serial array of planar members 51A, 51B. 51C and 51D. These planar members are stacked pancake fashion tranverse to the path of the electron beam 16 and have appropriate openings or apertures therein through which the electron beam 16 passes. The plate 51A comprises an aperture plate having a potential of about l5 kilo volts applied thereto and through which the electron beam 16 is sequentially scanned by means of appropriate deflection signals supplied to the course deflection coil 20A and 208. In this manner, the electron beam 16 can be caused sequentially to scan across each of the 22 micro deflection lenslets which in turn extend across the length of the elongated thin target window 22 and the width of the microfilm recording tape 23. The plate SIB also has a potential of about l5 kilo volts supplied to it and serves as an accelerating micro deflection lens for accelerating the electron beam past the two micro deflecting plates 51C having the fine horizontal or Y deflecting control signals supplied thereto from the control subcircuit 52 in FIG. 1. Within the area of view of each micro-deflection lenslet, the electron beam can be deflected along the longitudinal axis of the elongated thin target window 22 to some 6 character sites spaced along the width of the microfilm recording tape 23. ln conjunction with the horizontal or fine Y placement of electron beam 16, the fine vertical or X control potentials are supplied to the plate 51D for deflecting the electron beam vertically (transverse to the longitudinal axis of the elongated thin window 22) to provide dot placement in the character formation technique envisioned. Concurrently with deflection of the beam in accordance with the character position controlling signals supplied to the respective X and Y micro deflecting lenslets formed on plates 51C and 51D. beam blanking (enhancement) is accomplished by provision of suitable control signals to the control grid 13 from the gate driver control subcircuit 54 in FIG. 1 that in turn is supplied from the character generator circuit 49. It is anticipated that with such a structure the appropriate energizing potentials would be supplied to the aperture plate 51A and accelerating plate 518 from the power supply circuit 15 with the cathode 12 being maintained at a potential of -20 kilo volts and anode 14 maintained at a potential of about l kilo volts corresponding to the potential of the plates 51A and 518. The

conductive film

19A or 19B of the Lenard window is grounded to prevent build up of charge on this element. This should provide an electron beam having a current density of about 50 amperes per square centimeter formed into a focused beam of about 5 microns spot diamter by the coarse and fine focussing lens assemblies 17 and 518. A more detailed description of a suitable electron beam write-read apparatus employing a microdeflection lens assembly and similar to that shown at (1-1) in FIG. 1, is set forth in US. Pat. No. 3.7l0,352 Smith. et aL, issued Jan. 9, l973, the disclosure of which is hereby incorporated by reference.

In operation it will be appreciated that as the electron beam 16 is caused to scan say from left to right across the width of the microfilm recording tape 23 by coarse deflection lens 20A and 2013. it will proceed sequentially along the serially arrayed micro deflection lenslets 5|. Each individual micro deflection lenslet 51 will in turn cause the beam to be deflected horizontally across the width of the tape corresponding to six character sites. Since there are 22 lenslets this will allow 132 characters to be recorded in a line across the width of the microfilm recording tape 23. Within each of the micro deflection lenslets, the X deflection voltage will cause the focused electron beam 16 to be deflected in the vertical X (transverse to the longitudinal axis of elongated thin slit window 22) direction by an amount corresponding to the height of the characters to be recorded so as to scan or write out in conjunction with appropriate beam blanking (enhancement) the characters to be formed at each of the six character sites within the field of operation of each lenslet. Upon completion of a recorded line of characters the transport mechanism causes the microfilm recorded tape to move a distance corresponding to the spacing of each line of characters during the intervals that the electron beam 16 is retraced back to its starting point to initiate a new writing cycle.

FIG. 3 is a diagramatic view of a different form of an electron beam writing apparatus structured to provide character generation in accordance with a modified monoscope technique as outlined briefly above. With the arrangement shown in H0. 3 an array of four character generator and micro deflection and focusing lens structures 51' are arranged linearly across the width of the microfilm tape 23 in the manner shown. Each of the character generator micro deflection structures 5] includes a character mask (shown in FIG. 3A of the drawings) having an 8X8 array of alphanumeric characters formed therein. Coarse selection of one of the structures 51' is achieved by appropriate energization of the coarse deflection coils 20A and fine selection of desired character within the array of characters formed on the character mask disposed within the selected structure 51' is achieved through appropriate energization of fine deflection means comprised by a fine Y deflection coil 20B and a fine X deflection coil 20C. The structures 51' also include appropriate focusing lens arrangements for focusing the resultant character shaped electron beam and directing it through the associated character position deflector micro structure 51 arranged immediately below the character generator structure 51'. The fine deflectors in micro structure 51' are designed to deflect the electron beam to anyone of 33 different character site locations along the width of the microfilm tape 23 within its view in accordance with fine horizontal or Y position control signals supplied thereto. If desired in place of the character mask arrangement used in conjunction with fine deflection control signals supplied to the deflection coils 20B and 20C, the micro deflection structure 51 could be provided with transversely disposed X and Y deflection plates. and character generation could be performed by these deflecting plates under the character generator control using for example a raster scan with appropriate beam blanking (enhancement) to form a dot matrix. With such an arrangement, character positioning of the beam would be done with the last set 51 of deflection electrodes each of which would access 33 character positions, The actual number of micro deflection structures required with such an arrangment would depend upon the ease of manufacturing and spot size re quirements. With a fan shaped beam and at the cost of an extra character generator memory. it would be possible to generate more than one character at different positions on the line simultaneously, thus achieving a greater printing speed. Such modifications would require greater beam current from the cathode however and might impair cathode life. To overcome this problem it is feasible to provide an electron beam recording apparatus having a replaceable cathode. For example the electron source and relatively inexpensive electrostatic focusing electrodes could be fabricated within a removeable envelope or housing including a Lenard window and would be arranged to slip within a second housing containing the more expensive and microdeflection electromagnetic lens assemblies. For a detailed description of comparable electron beam recording devices employing character masks, reference is made to US. Pat. No. 3,382,392 Corpew, issued May 7, l968 and US. Pat. No. 3.299,4l8 Treseder, issued Jan. l7, 1967.

From the preceding description of FIGS. 1-3 of the drawings, it will be appreciated that the invention makes available a novel EB COM printer system capable of high speed, high resolution and high intensity printing on microfilm at ambient pressure. In addition, the printer includes the ability to print out graphics and forms by reason the inclusion of the buffer memory and the forms projection system. The EB COM printer comprises a combined printer-controller that can be easily interfaced with any known computer system and because of its high printing speed on the order of between l0,000 lines per minute to 25,000 lines per minute it places little or no constraints on the through-put of the computer system. Because of these characteristics, the EB COM printer can be used as an on-line COM printer device operable as a standard plug-in compatible peripheral equipment for use with computer systems. It makes available a new and improved electron beam apparatus having a Lenard window fabricated from a differentially etched bulk supporting member of silicon and silicon dioxide or the like with the Lenard window portion having a thickness on the order of 5005,000 angstrom units thick. If desired the electron beam apparatus can include both electrostatic and electromagnetic deflection lens structure with a removable electron source whereby the source can be replaced after a number of hours of use without requiring the complete electron beam recording apparatus be replaced or rebuilt. By appropriate fabrication of the Lenard window, the size of the window can be used for blanking the electron beam by the use of appropriate beam blanking deflection potentials provided to the deflection lens of the structure. The microfilm recording medium used with the EB COM printer may comprise wet silver requiring a wet developing process. dry silver, diazo, vesicular calvar or some other dry recording medium and/or technique using thermal processing for development. The recording medium may be in the form of a tape, card. drum, disk, or any other form presently known in the art for transporting the recording medium past the Lenard window portion of the electron beam recording apparatus.

4. High Speed Multiple Scan/Character EB COM Printer System FIG. 4A and 48 comprise a functional block diagram of a new and improved high speed multiple scan per character EB COM printer system made available by the invention. This system differs from the previously described EB COM systems in that it employs a very fine elongated thin slit SiO Lenard window along which the electron beam is traced repetitively for a predetermined number of scans. Each individual scan of the electron beam is used in conjunction with suitable beam blanking (enhancement) and results in the recording of a partial character at each character site along a line of characters. Concurrently with the microfilm tape wide scanning and partial character recording. the microfilm tape is moved transversely to the longitudinal axis of the elongated thin slit window so that repetitive scanning of the electron beam for a predetermined number of scans results in the raster recording of a line of complete characters across the width of the tape. For recording in this manner, a continuous speed tape drive is desired whose speed of movement is related to the scanning frequency of the electron beam as will be described more fully hereinafter.

In the embodiment of the invention shown in FIG. 4B the electron beam recording apparatus is somewhat different in construction from that employed in previously described embodiments. The electron beam recording apparatus 10 shown in FIG. 4B is comprised by an evacuated housing ll having an electron source shown generally at l2l 4 including a cathode, control grid and anode which are not shown individually. The electron source 12-14 is mounted at one end of the evacuated housing II and a Lenard target window shown at 18 is mounted at the other for permitting egress of the electron beam 16 out of the evacuated housing 11 and onto the recording microfilm tape 23. The lenard target window I8 is fabricated in the manner previously described in connection with FIG. 1A of the drawing and hence will not again be described in detail. There is one difference however. in the construction of the Lenard target window which is important to note. Because of the capability of forming very fine straight cuts or openings defining the target window using well known micro circuit etching techniques on a crystalline semiconductor body such as silicons the target window 18 employed in the electron beam apparatus in FIG. 4 is made to be a very fine thin slit whose width is on the order of the diameter of the electron beam I6 produced by the electron beam recording apparatus. This slit may be as small as 5 microns in width and conceivably could extend to as much as a ten or 50 micron wide slit or larger, but preferably is as small as possible to provide good resolution. The length of the target window is of course determined by the length of line of characters to be recorded and should be sufficiently long to accommodate a scanning trace of the electron beam sufficiently wide to record 132 alphanumeric characters in a line.

Similar to FIG. 1, FIG. 4 illustrates the electron beam apparatus arranged in a manner such that its electron beam is scanned back and forth along an axis extending into the plane of the paper. The microfilm tape take up and play out spools are arranged to transport the microfilm tape 23 in a direction transverse to the longitudinal axis of the elongated thin slit window 18. The electrons produced by the source 12-14 are accelerated through an apertured anode plate 61 and directed through a spray aperture plate 62 mounted on one end of a four fold electrostatic deflector element 63. The spray aperture 62 operates as a beam defining aperture to limit the beam current and also serves to shape the electrons in the form of a pencil-like beam. The four fold electrostatic deflecting plates 63 then operate to deflect or displace the beam so as to align it along a central axis extending between the source I2l4 and the Lenard target window 18. The beam of electrons then is directed through an electrostatic focusing lens arrangement I7 and through a second beam defining aperture 64 which may be adjustable if desired, and thence through a second focusing lens structure 65. The first focusing lens 17, the second aperture 64 and the second focusing lens 65, which may be either electro magnetic or electrostatic in nature, are included in the electron beam recording apparatus to provide further shaping of the electron beam so as to result in an extremely fine pencil-like electron beam writing probe having a diameter on the order of 5 microns. This finely shaped electron beam then travels through an electromagnetic deflecting lens 66 for deflecting the electron beam across the longitudinal axis of the elongated thin slit Lenard target window 18 in the manner described above.

FIG. 4C of the drawings is a diagrammatic sketch illustrating how the multiple scan characters are built up or recorded on the surface of the microfilm tape 23 as a result of the partial character recording achieved during each individual scan of the electron writing probe accompanied by appropriate beam blanking (enhancement). In FIG. 4C the arrows associated with the numerals l and 7 extend in the direction of the longitudi nal axis of the microfilm recording tape (and hence in the direction of movement thereof) and the arrows associated with the numerals and 8 extend in a direction across the width of microfilm tape 23. Each line of characters to be recorded is transmitted in the form of pulsed, coded, digital electric signals to a character generator to be described herein after which converts the signals to appropriate beam blanking (enhancement) signals that are supplied to the control grid of the electron beam recording apparatus 11. Placement of a dot at a particular point along the width of the microfilm recording tape 23 will of course be determined by this signal in conjunction with the deflection potentials supplied to the deflecting lens arrangement 66. As illustrated in FIG. 4C a line of characters is printed by splitting each character in the line into a matrix of 5 X 7 dots with the equivalent of a three dot spacing being interposed between each character in a line and the equivalent of three dot spacing being interposed between each line of characters in a frame. It is presumed that the now generally accepted format of 66 lines in a frame and 132 characters per line is used in carrying out the recording process. The technique is in no way restricted to this specific format however and it is cited only as exemplary of one mode in which the novel EB COM system of FIG. 4 can be operated. From a consideration of HG. 4C it will be appreciated therefor that some ten horizontal scans of the electron beam is required in order to complete the recording of a complete line of characters including appropriate line spacing and seven of these scans will be productive in producing the character to be recorded in a particular character site along the width of the microfilm tape 23. Similarly, only five vertically placed dots are required to construct the character for each horizontally placed character site along the axis of scan of the electron beam. Which dots in the five by seven dot matrix are blanked and which are enhanced to result in the production of a dot recording on the surface of the microfilm tape 23, is determined by the character control signal supplied to the control grid of source 12-14. Accordingly. at any given point along the microfilm tape 23 the electron beam 16 will be scanned across its width and appropriately blanked or enhanced to produce a partial character dot pattern which when accumulated over a predetermined number of l0 scans measured from the initiation of a new line of characters recording cycle. results in a recording such as the BB shown in FIG. 4C.

Suitable control circuitry for controlling operation of the electron beam writing apparatus in the above briefly described manner is illustrated in FIG. 4A. This control circuitry is comprised basically by a printercontroller 41. a character generator 49 and buffer memory means 42. The heart of the printer-controller 41 is comprised by a dot clock and control circuit 71 that sets up the timing sequence with which the electron beam will be blanked. The output from the dot clock and control circuit 71 is supplied to a modulo-8 horizontal dot position-in-a-character counter 72 which determines which dots in a character extending in the horizontal (co-extending with the longitudinal axis of elongated thin slit target window 18) direction are to be printed. Modulo-eight dot counter 72 supplies its output over a conductor 73 to the input to a modulo- 132 horizontal characters-in-a-line counter 74 whose output in turn controls a ramp generator supplying a horizontal coil driver amplifier 76 that in turn supplies deflection potentials to the deflecting lens arrangement 66. The ramp generator 75 develops a substantially linear saw tooth wave-shaped excitation potential that is amplified in the horizontal coil driver amplifier 76 and serves to deflect the finely focused electron beam probe width-wise across the microfilm recording tape 23 in a continuous linear manner. At the end of a line of 132 characters represented by 8 X 132 dot clock pulses from the dot clock and control circuit 71, the ramp generator 75 produces a retrace potential that causes the electron beam deflecting lens 66 quickly to retrace the beam back to its initial starting point while being blanked by an appropriate potential supplied to its control grid. During this retrace portion. intermediate each line scan of the recording electron beam, a retrace. inhibit potential is supplied back over a conductor 77 to inhibit operation of the dot clock and control circuit 71. This retrace inhibit potential is supplied from the output of the modulo 132 characters-ina-line counter 74 whose output is also supplied to a modulo 66 lines-in-a-frame counter 78 whose output in turn is supplied over a conductor 79 to control the operation of a page and film advance and develop control circuit 8] controlling operation of the take up and pay out

spools

31 and 32 through a motor driver control circuit 82. The page and film advance and develop control 81 also controls operation of a heat source 83 which serves to develop the electron image written on the microfilm tape 23 during earlier writing cycles.

The dot clock and control circuit 71 is in turn controlled from the output of a buffer control circuit 85 contained within the buffer memory means 42 and which further controls operation of a three line buffer memory 86. Additionally. the buffer control 85 communicates via line 87 with the central processing unit 88 of a computer system with which the EB COM printer is used as a print out device. The computer system normally will include a working memory such as the core memory 89 under the control of the central processing unit. The central processing unit 88 on request from the buffer control 85 will operate to transfer from the core memory 89 one page or frame of 66 lines of character into a disc memory unit 91 comprising a part of the overall EB COM printer system memory 42 which further includes the three line buffer memory unit 86. The buffer control on direction from the central processing unit indicating that the disc memory 91 is full will initiate read out of the disc memory 91 three lines at a time into the three line buffer memory 86. The three line buffer memory 86 may comprise a conventional MOS dynamic counter using integrated circuit multi vibrator units, or it may comprise a memory tube such as the Lithicon or other similar small memory means Similarly, the disc memory 91 could be replaced with a small ferrite core memory, a MOS dynamic counter memory. a Lithicon memory. or the like. The disc memory 91 serves as an interface between the three line buffer memory 86 of the EB COM printer system and the central processing unit of the computer system with which the EB COM printer system is being used.

The three line buffer memory 86 stores three lines of characters and transmits them serially one line at a time over conductor 92 to a MOS read only memory 93 that comprises a part of a character generator 49 and may comprise a TMS 2400 integrated read-only memory circuit chip manufactured and sold by Texas Instruments Co. Read out of each line of characters stored in the buffer 86 into the read only memory 93 is under the control of buffer control 85. In order to inform the buffer control 85 of the completion of one scanning line by the electron recording beam, the output of the modulo I32 characters-in-a-line counter 74 is supplied over

conductor

94 and 95 to a control input of the buffer control 85. The output characters-in-a-line counter 74 also is supplied to the input of a modulo l vertical dot position-in-a character counter 96 that supplies its output over line 97 to the read only memory 93. The output from the vertical dot position-in-a char acter counter 96 in conjunction with the character indicating signals supplied from buffer 96 and the horizontal in-a-character count signal supplied from counter 72 over a conductor 98 to a digital multiplexer 99 connected to the output of read only memory unit 93, operates to establish which dot in any given character matrix corresponding to a desired character site across the width of the microfilm tape is to be intensified, and hence recorded on the microfilm tape. The resultant is an intensifying control signal supplied at the output of the five position digital electronic multiplexer switch 99, and is supplied through a grid driver l0] to the control grid of the electron beam controlling apparatus 10. For a more detailed description of suitable component subcircuits usable in the above-described EBCOM printer system, reference is made to the above-cited U.S. Pat. Nos. 3,l95,l l2; 3,l67,747; 3,l 2l,2l6; and to such text books as The Source Book of Electronic Circuits published by the McGraw-Hill Co., John Markus, Ed., Copyrighted 1968, Library of Congress Catalog Card Number 67-l5037. Any of the known subcircuits described in these prior art reference texts and patents, or their integrated circuit counterparts, readily could be employed by one skilled in the art to fabricate the above-briefly-described EBCOM printer system in the light of the present disclosure.

Having described the construction of the multiple scan/character EB COM printer system shown in FIGS. 4A and 48, its operation is as follows. Information to be printed which is being transferred out of the core memory 89, or alternatively is being generated by the central processing unit 88, is transferred to the disc memory 91 and stored. The disc memory is capable of storing at least one complete page or frame of 66 lines of characters with each line containing a maximum of I32 characters. When a full page or frame has been generated and stored in disc memory 91, the central processing unit signals the buffer control 85 that it is ready to print. Upon sensing that the three line buffer memory unit 86 is full. the buffer control 85 initiates operation of the dot clock and control circuit 71 and printing commences. Upon one line in buffer memory 86 becoming empty the buffer control signals the central processing unit 88 to transfer another line of data which it will do at the next available moment before the disc memory has been emptied. Thus it will be seen that the printing operation is performed on a line of characters" basis.

Upon the dot clock and control circuit 71 being turned on by buffer control 85, a line of characters to be printed is transmitted to read only memory 93 out of the buffer memory 86 through line 92. Concurrently turn on of the dot clock and control will initiate operation of the ramp generator which will start to sweep the electron beam horizontally across the width of the microfilm tape 23. As the electron beam scans across the width of the microfilm tape in a line, the read only memory 93 in conjunction with the digital multiplexer 99 which is under the control of modulo 8 horizontal position-in-a-character dot counter, and the modulo-l0 vertical dot position-in-a-character counter 96. determines which dots are to be intensified and hence recorded on the microfilm tape 23. As stated previously the line of characters are printed by splitting each character in a line into a matrix of five by seven dots with the equivalent of three dot spacing between characters and between each line of characters. To complete a line of characters, l0 scans of the electron beam across the width of tape 23 is required with only selected ones of a five by seven dot matrix within the 132 character positions contained within a line of characters being generated to form the desired character on a given character recording site. During this process the modulo-8 horizontal dot position-in-a-character counter 72 keeps track of the horizontal position of the beam in any given charcter site along the line of characters being recorded while the modulo 10 vertical dot position-in-a-character counter keeps track of the particular scan line being scanned of the ten scan lines required to form a line of characters. As the electron beam is being scanned across the full width of the microfilm tape 23, the modulo 132 character-in-a-line counter 74 keeps track of which particular character is being partially printed during any particular portion of a scan of the electron beam.

Once the printing of a line of characters is completed, this fact will be signaled to the buffer control by the characters in a line counter 74 which will then operate to read into the read only memory 93 another line of characters to be printed out. Concurrently the central processing unit 88 will be signaled that the printer system is ready to receive another line of data to be printed. This process is repeated until a complete page or frame of 66 lines of characters is printed. The number of character lines printed in a frame is controlled by modulo 66 character lines counter 78 which signals the page and film advance and develop control circuitry 88 when a frame is completed. It should be noted that while the instant system is described as including substantially simultaneous development of the recorded electron image following printing of the image in the above described manner, it is entirely feasible for the electron image to be stored on the micro film and developed subsequently at a more convenient time and under less strenuous conditions. Additionally, while in the system of FIG. 4, beam blanking (enhancement) is employed to achieve dot recording, it is entirely feasible to include an additional deflecting signal for deflecting the recording electron beam probe to one side of the other of the Lenard window so as to achieve beam blanking by interception of the beam by the sides of the Lenard window structures as described earlier with respect to FIG. 1A of the drawings.

With the multiple scan per character EB COM printer system shown in FIGS. 4A and 4B and employing an electron beam spot size of 5 micron diameter, it would be possible to write characters in the aboveidentified fashion having a height of 75 microns, a width of 50 microns and with a spacing of 30 microns between characters and between character lines. With such a system employing 10 scans per character to write a character. a complete line of characters could be traced out in 24,000 microseconds corresponding to 240 microseconds for a one line scan of l32 partial characters or an average of l8 microseconds per character. With a system having the above constraints, the frequency of writing each character would be flcharacter l/l.8 X l 550 kilohertz and the frequency per line would f/line of characters V2.40 X l0 4 kilohertz. At these writing rates, the microfilm tape take-up and pay-out spools can be driven by continuous drive motors whose speed of advance during a recording operation would be correlated to the inhibit period provided at the end of each line scan of the recording electron beam so that the tape advances a distance on the order of 10 microns during this interval before again initiating a write cycle on the part of the dot clock and control circuit 71. it should be noted however that the systems specifications listed above are only exemplary and can be varied widely to meet the needs of any particular installation. For example the recording beam spot diameter can be varied from the 5 microns indicated up to a 75 micron diameter spot to provide a required amount of energy to accomplish high speed recordings having good resolution and high intensity. Other variation and modifications to meet the requirements of different high speed printer installations will be suggested to those skilled in the art.

From the foregoing description, it will be appreciated that the invention provides a new and improved EB COM printer system and electron beam recording apparatus therefor having high speed printing capabilities together with good resolution and high intensity to provide good quality microfilm prints. The electron beam recording apparatus possesses long cathode life for its electron beam source due to the novel construction of a Lenard window structure. The EB COM printer system can be adapted for use with a wide variety of character formation techniques using a large number of microfilm recording mediums having different compositions such as wet silver. dry silver. diazo, Kalvar, etc and having widely different forms such as tape, card, drum, disc, etc. The invention also makes available to the art a novel recording technique employing partial electron beam recording with each individual scan of the recording electron beam while moving the record medium transversely to the direction of scan of the electron beam to accomplish raster recording of characters in a line over a predetermined number of scans. The EB COM printer system incorporating the above characteristics actually comprises a combined controller-EB COM printer having a buffer memory that allows it to be easily interfaced with any known computer system as a standard. plug compatible peripheral equipment having print-out speeds on the order of 10,000 to 25,000 lines per minute and even higher so that it places little or no constraints on the high speed processing capabilities of the computer system with which it is used.

While the electron beam recording apparatus described herein has been disclosed as primarily intended for use in an EB COM printer system, it is believed obvious to those skilled in the art that the novel electron beam apparatus can find application in a wide variety of uses wherein it is desired to impart the energy of an electron beam to a medium exteriorily of an evacuated space. Such applications as electron beam analog recording on microfilm and television picture recording are believed to be logical uses for the new and improved electron beam apparatus made available by this invention. Accordingly it will be seen that the novel electron beam apparatus can be used in a wide variety of applications in addition to those detailed above.

Having described several embodiments of a new and improved electron beam type computer output on microfilm printer and electron beam apparatus therefor. constructed in accordance with the invention, it is believed obvious that other modifications and variations of the invention are possible in the light of the above teachings. It is therefor to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.

What is claimed is:

l. in an electron beam apparatus of the type including a source of electrons disposed within an evacuated housing and means for directing the electrons in the form of a beam toward one of the walls of the housing, the improvement comprising a Lenard window fabricated from a differentially etched bulk supporting member secured to the wall of the evacuated housing and having an extremely thin window portion through which the electron beam is directed for permitting egress of the electron beam of the evacuated housing into a higher pressure space surrounding the housing with a minimum of beam scattering while maintaining the integrity of the evacuated space within the housing, said thin window portion consisting of a material different than the bulk supporting member and not susceptible to be etchant employed to form the window in the supporting bulk member.

2. thin electron beam apparatus according to claim 1, wherein the think window portion is formed by chemical reaction with the bulk supporting member and the differentially etched bulk supporting member and thin window portion are from the class of materials consisting essentially of silicon silicon dioxide (Si- SiO2); aluminum-aluminum oxide (AL-A1 03); tan talum-tantalum oxide (Ta-TaO); titanium-titanium oxide (Ti-TiO); silicon-silicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC) silicon-aluminum oxide (SF-M 0 3. An electron beam apparatus according to claim I, wherein the differentially etched bulk supporting member has a thin conductive layer formed over at least a part of the surface of bulk supporting member exposed to the electron beam and extending over at least part of the thin window portion whereby build-up of a substantial charge on the window can be minimized.

4. An electron beam apparatus according to claim 1, wherein the electron beam apparatus is of the type including deflecting means for deflecting the electron beam along at least one axis of movement and said window portion comprises an elongated thin slit having its long axis extending in the direction of deflection of the electron beam.

5 An electron beam apparatus according to claim 1, wherein said window portion comprises an elongated thin slit having a width which is more narrow than the largest dimension of the cross section of an elongated electron beam produced by the electron beam apparatus.

6. An electron beam apparatus to claim 1, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed to a desired thickness on the surface of the bulk supporting silicon member by controlled chemical reaction prior to etching the window therein and wherein the thin slit window portion as a width on the order of -75 microns and a thickness on the order of SOD-2,000 angstrom units.

7. An electron beam apparatus according to claim 4, wherein the electron beam apparatus further includes additional micro deflecting means for deflecting the electron beam along two transverse axes of movement with respect to a character wide thin slit window portion for writing a line of alphanumeric characters, and beam blanking means for blanking the electron beam at appropriate points along the line of characters to provide for separation and formatting of the written characters.

8. An electron beam apparatus according to claim 4, wherein an array of characters masks having openings there in forming alphanumeric characters are arranged along the longitudinal dimension of the elongated thin slit window portion and the deflecting means serves to deflect the electron beam to a selected character on one of the character masks, and the electron beam apparatus further includes micro deflection means disposed intermediate the array of character masks and the first mentioned deflecting means for focusing and deflecting a desired alphanumeric character-shaped electron beam produced by passage of the electron beam through a selected character opening on one of the character masks to cause the same to be directed through the thin window portion and a desired point along its length.

9. An electron beam apparatus according to claim 4, wherein an extremely fine slit window portion is provided having a width on the order of the diameter of the electron beam whereby partial character recording can be achieved during each scan of the electron beam across the longitudinal direction of the window portion accompanied with appropriate beam blanking at selected points along the path of travel thereof to provide character spacing and formatting and repetitive scans of the electron beam are required for complete character recording.

10. An electron beam apparatus according to claim 9, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed on the surface of the bulk supporting silicon member prior to etching the window therein and the elongated thin slit window portion has a longitudinal dimension on the order of the length of a line of recorded characters and a thin width portion on the order of 5 microns with the thickness of the window portion being on the order of SOD-2,000 angstrom units.

11. An electron beam apparatus according to claim 9, further including means for blanking the beam of electrons at appropriate points along the path of travel thereof during the scanning of the beam in the longitudinal direction of the thin slit window portion.

12. An electron beam apparatus according to claim 11, wherein said electron beam blanking means comprises means for producing suitable on-off blanking signals supplied to the control grid of the electron beam apparatus.

13. An electron beam apparatus according to claim ll, wherein said electron beam blanking means comprises deflecting means for deflecting the electron beam transversely to the longitudinal axis of the elongated thin slit window portion so that the sides of the supporting bulk member intercept and blank the beam at points where beam blanking is desired.

14. An electron beam COM printer system including an electron beam apparatus of the type set forth in claim 1, an electron sensitive microfilm recording medium, transport means for supporting the microfilm recording medium immediately adjacent the thin window portion of the electron beam recording apparatus for recording data thereon, printer control circuit means coupled to said electron beam writing apparatus and the transport means for controlling the operation thereof, and character generator circuit means controlled by the printer control circuit means and coupled to the electron beam writing apparatus for controlling the operation thereof in conjunction with the printer control circuit means, said printer control circuit means and said character generator circuit means being controlled from the output of a computer system with which the COM printer is used as a print-out device.

15. An electron beam COM printer system according to claim 14, further including buffer memory means intercoupled with the printer control circuit means and the character generator means for receiving a predetermined number of lines of data to be printed from a computer system central processing unit plus control data for directing operation of the printer control circuit means, said buffer memory means serving to store temporarily the predetermined number of lines of data while each line of data is being printed out by the COM printer thereby freeing the computer system central processing unit for further operations during printing of the stored lines of data.

16. An electron beam COM printer system according to claim 15, wherein the electron beam recording apparatus is of the type including deflecting means for deflecting the electron beam along at least one axis of movement and the window portion comprises an elongated thin slit having its long axis extending in the direction of deflection of the electron beam, said transport means operates to move the microfilm recording medium in a direction transverse to the longitudinal axis of the elongated thin slit window whereby successive lines of data can be recorded raster fashion, said printer control circuit means is coupled to and controls operation of the deflecting means to cause tracing of the electron beam along the longitudinal dimension of the elongated thin slit window portion, and the character generator circuit means controls beam blanking and character formatting.

17. An electron beam COM printer system according to claim 16, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein and wherein the thin slit window portion has a length on the order of one line of recorded alphanumeric characters on microfilm, a width on the order of 75 microns and a thickness on the order of l,000-5.000 angstrom units.

18. An electron beam COM printer system according to claim 17, further including means enclosing the Lenard window portion of the electron beam apparatus and the microfilm disposed immediately adjacent the Lenard window portion in an enclosed space maintained at a reduced pressure relative to the surrounding ambient atmosphere.

19. An electron beam COM printer system according to claim 16, wherein said window portion comprises an elongated thin slit having its longest dimension approximating the length of a line of microfilm recorded alpha numeric characters and having the thin dimension thereof approximating the height of an individual alphanumeric character recorded on microfilm, and wherein the electron beam recording apparatus further includes additional micro deflecting means for deflecting the electron beam along two transverse axes of movement with respect to the character wide elongated thin slit window portion for writing a line of alphanumeric characters, and beam blanking means for blanking the electron beam at appropriate points along the line of characters to provide for separation and formatting of the written line of characters, said character generator circuit means controlling operation of both said additional micro deflecting means and said beam blanking means.

20. An electron beam COM printer system according to claim 19, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed on the surface of the bulk supporting member by chemical reaction prior to etching the window therein and wherein the thin slit window portion has a width on the order of 75 microns and a thickness on the order of LOGO-5,000 angstom units.

21. An electron beam COM printer system according to claim 16, wherein an array of character masks having openings therein forming alphanumeric characters are arranged along the longitudinal axis of the elongated thin slit window portion and the deflecting means serves to deflect the electron beam to a selected character on one of the character masks, and said electron beam recording apparatus further including micro deflection means disposed intermediate the array of character masks and the first mentioned deflecting means for focusing and deflecting a desired alphanumeric character-shaped electron beam produced by passage of the electron beam through a selected character opening on one of the character masks to cause the same to be directed through the thin window portion at a desired point along its length and thereby record an electron image of the selected character at a desired point on the microfilm recording medium disposed under the thin window portion.

22. An electron beam COM printer system according to claim 16, wherein an extremely fine elongated slit window portion is provided having a width on the order of the diameter of the electron beam and means are provided for repetitively scanning the electron beam in the direction of the longitudinal axis of the elongated window portion together with means for blanking the beam of electrons at appropriate points along the path of travel thereof whereby partial character recording is achieved during each scan of the electron beam. and the transport means moves the microfilm recording medium transverse to the longitudinal dimension of the elongated fine slit window portion intermediate each scan whereby during successive scans of the electron beam raster recording of lines of complete alphanumeric characters is achieved by the accumulation of partial character recordings accomplished during each respective scan of the electronic beam.

23. An electron beam COM printer system according to claim 22 wherein the thin window portion is formed by chemical reaction with the bulk supporting member and the differentially etched bulk supporting member I and thin window portion of the electron beam recording apparatus are from the class of materials consisting essentially of silicon-silicon dioxide (Si-SiOfl; aluminum-aluminum oxide (Al-A1 0 tantalum-tantalum oxide (Ta-TaO); titanium-titanium oxide (Ti-TiO); silicon-silicon nitride (Si-SiN); and silicon-silicon carbide (Si-SiC); silicon-aluminium oxide (Si-M 0 24. An electron beam COM printer system according to claim 22 wherein the differentially etched bulk supporting member comprising a part of the electron beam recording apparatus is silicon and the thin window portion thereof is comprised by a thin layer of silicon dioxide previously formed to a desired thickness on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein and the elongated thin slit window portion has a longitudinal dimension on the order of the length of a line of recorded characters and a width on the order of 5 microns with the thickness of the window portion being on the order of SOD-2,000 angstrom units.

25. An electron beam COM printer system according to claim 24, wherein the means for blanking the beam of electrons at appropriate points during each individual scan thereof comprises on-off blanking signals supplied to the control grid of the electron beam recording apparatus from the character generator circuit means.

26. An electron beam COM printer system according to claim 24, wherein the means for blanking the beam of electrons at appropriate points during each individual scan thereof comprises deflecting means for deflecting the electron beam transversely to the longitudinal axis of the elongated thin slit window portion so that the sides of the supporting bulk member intercept and blank the beam at points where beam blanking is desired.

27. An electron beam COM printer system including in combination an electron beam recording apparatus comprising an evacuated housing having a source of electrons disposed therein and controlled by a control grid, means for directing the electrons in a beam toward one end of the housing, a Lenard window secured to the housing against which the electrons are directed, said Lenard window being fabricated from a differentially etched bulk supporting member secured to the wall of the evacuated housing and having an extremely thin window portion in the form of an elongated thin slit through which the electron beam is directed to permit egress of the electron beam out of the evacuated housing, said elongated slit thin window portion consisting of a material formed on but different than the bulk supporting member and not susceptible to the etchant employed to form the window in the bulk supporting member, deflecting means for deflecting the electron beam along the longitudinal axis of the elongated thin slit window portion, an electron sensitive microfilm tape recording medium, tape transport means for disposing the microfilm tape recording medium immediately adjacent the elongated slit window portion of the electron beam recording apparatus and for transporting the tape past the window portion in a direction transverse to the longitudinal axis of the elongated thin slit window portion, developing means for developing electron images recorded on the microfilm tape recording medium, printer control circuit means coupled to the deflecting means for said electron beam recording apparatus, to said tape transport means and to said developing means for controlling the operation thereof, and character generator circuit means controlled by the printer control circuit means and coupled to the control grid for the electron source of the electron beam recording apparatus for controlling operation of the electron beam recording apparatus in conjunction with the printer control circuit means whereby the electron beam is caused repetitively to scan along the longitudinal axis of the elongated thin slit window portion and is blanked at appropriate points in accordance with characters to be recorded, said printer control circuit means and said character generator circuit means being controlled from the output of an electronic computer system with which the COM printer is used as a print-out device.

28. An electron beam COM printer system according to claim 27, wherein the differentially etched bulk supporting member and thin window portion are from the class of materials consisting essentially of silicon-silicon dioxide (Si-SiO aluminum-aluminum oxide (Al-Al,0;,); tantalum-tan talum oxide (TaTaO); and titanium-titanium oxide (Ti-TiO); siliconsilicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC); and silicon-aluminium oxide (Si-M 29. An electron beam COM printer system according to claim 27, wherein an extremely fine slit window portion is provided having a width on the order of the diameter of the electron beam whereby partial character recording is achieved during each scanning of the electron beam across the longitudinal direction of the window portion accompanied with appropriate beam blanking at selected points along the path of travel thereof to provide character spacing and formatting, and the transport means moves the microfilm recording medium transverse to the longitudinal dimension of the elongated thin slit window portion intermediate each scan whereby during successive scans of the electron beam raster recording of lines of complete alphanumeric characters is achieved by the accumulation of partial character recordings accomplished during each respective scan of the electron beam.

30. An electron beam COM printer system according to claim 27, further including buffer memory means intercoupled with the printer control circuit means and the character generator means for receiving a predetermined number of lines of data to be printed from a computer system central processing unit plus control instructions for directing operations of the printer control circuit means. said buffer memory means serving to store temporarily the predetermined number of lines of data plus control instructions while it is being printed out by the COM printer device thereby freeing the computer system central processing unit for further operations during printing of the stored lines of data.

31. An electron beam COM printer system according to claim 30, wherein each character recorded on the microfilm tape recording medium is comprised of a matrix of horizontal coextending and vertical transversely placed dots measured with respect to the longitudinal axis of the elongated thin slit window and with the equivalent of a predetermined number of dot spacings between characters in each line and between each line of characters, the placement of a dot in the formation of a character in a line of characters and the spacing thereof with respect to other dots comprising the character and line of characters being controlled by appropriate manipulation of the beam deflection means and beam blanking means of the electron beam recording apparatus.

32. An electron beam COM printer system according to claim 31, wherein the printer control circuit means comprises dot clock pulse and control circuit means coupled to and responsive to the buffer memory means for generating the basic dot clock pulse signal, horizontal dot position-in-a-character counter means responsive to the dot clock pulse and control circuit means, horizontal characters-in-a-line counter means responsive to the horizontal dot position-in-a-character counter means and coupled to and controlling a ramp generator means for driving the deflection means for deflecting the electron beam horizontally along the longitudinal axis of the elongated thin slit window portion. means for coupling the output from said characters-ina-line counter means back to the input of the dot clock pulse and control circuit means for inhibiting operation of said dot clock pulse and control circuit means during the retrace portion of the beam deflection means, vertical line-in-a-page counter means coupled to the output from said characters-in-a-line counter means and controllingsaid tape transport and developing means, vertical-dot-position-in-a-character counter means responsive to the output from the characters-in-a-line counter means, said character generator means comprising a read only memory matrix responsive to the buffer memory means and the output of the vertical-dotposition-in-a-character counter means and digital multiplexing circuit means supplied with said dot clock pulses and controlled by read only memory matrix for controlling the grid driving amplifier supplying the control grid of the electron beam recording apparatus for intensifying the electron beam at points where dots are to be recorded.

33. An electron beam COM printer system according to claim 32, wherein an extremely fine elongated slit window portion is provided having a width on the order of the diameter of the electron beam whereby partial character recording is achieved during each individual scan and recording of a complete character is accomplished by a series of successive scans of the electron beam across the longitudinal axis of the elongated thin slit window portion accompanied with appropriate intensification of the electron beam at selected points as determined by the read only memory along the path of travel of the electron beam to provide dot spacing and fonnatting of the characters being printed.

34. An electron beam COM printer system according to claim 33, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed to a desired thickness on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein and the elongated thin slit window portion has a longitudinal dimen-

Claims

2. thin electron beam apparatus according to claim 1, wherein the think window portion is formed by chemical reaction with the bulk supporting member and the differentially etched bulk supporting member and thin window portion are from the class of materials consisting essentially of silicon-silicon dioxide (Si-SiO2); aluminum-aluminum oxide (Al-Al2O3); tantalum-tantalum oxide (Ta-TaO); titanium-titanium oxide (Ti-TiO); silicon-silicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC) silicon-aluminum oxide (Si-Al2O3).
3. An electron beam apparatus according to claim 1, wherein the differentially etched bulk supporting member has a thin conductive layer formed over at least a part of the surface of bulk supporting member exposed to the electron beam and extending over at least part of the thin window portion whereby build-up of a substantial charge on the window can be minimized.
4. An electron beam apparatus according to claim 1, wherein the electron beam apparatus is of the type including deflecting means for deflecting the electron beam along at least one axis of movement and said window portion comprises an elongated thin slit having its long axis extending in the direction of deflection of the electron beam. 5 An electron beam apparatus according to claim 1, wherein said window portion comprises an elongated thin slit having a width which is more narrow than the largest dimension of the cross section of an elongated electron beam produced by the electron beam apparatus.
6. An electron beam apparatus to claim 1, wherein the differentially etched bulk supporting meMber is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed to a desired thickness on the surface of the bulk supporting silicon member by controlled chemical reaction prior to etching the window therein and wherein the thin slit window portion as a width on the order of 5-75 microns and a thickness on the order of 500-2,000 angstrom units.
7. An electron beam apparatus according to claim 4, wherein the electron beam apparatus further includes additional micro deflecting means for deflecting the electron beam along two transverse axes of movement with respect to a character wide thin slit window portion for writing a line of alphanumeric characters, and beam blanking means for blanking the electron beam at appropriate points along the line of characters to provide for separation and formatting of the written characters.
8. An electron beam apparatus according to claim 4, wherein an array of characters masks having openings there in forming alphanumeric characters are arranged along the longitudinal dimension of the elongated thin slit window portion and the deflecting means serves to deflect the electron beam to a selected character on one of the character masks, and the electron beam apparatus further includes micro deflection means disposed intermediate the array of character masks and the first mentioned deflecting means for focusing and deflecting a desired alphanumeric character-shaped electron beam produced by passage of the electron beam through a selected character opening on one of the character masks to cause the same to be directed through the thin window portion and a desired point along its length.
9. An electron beam apparatus according to claim 4, wherein an extremely fine slit window portion is provided having a width on the order of the diameter of the electron beam whereby partial character recording can be achieved during each scan of the electron beam across the longitudinal direction of the window portion accompanied with appropriate beam blanking at selected points along the path of travel thereof to provide character spacing and formatting and repetitive scans of the electron beam are required for complete character recording.
10. An electron beam apparatus according to claim 9, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed on the surface of the bulk supporting silicon member prior to etching the window therein and the elongated thin slit window portion has a longitudinal dimension on the order of the length of a line of recorded characters and a thin width portion on the order of 5 microns with the thickness of the window portion being on the order of 500-2,000 angstrom units.
11. An electron beam apparatus according to claim 9, further including means for blanking the beam of electrons at appropriate points along the path of travel thereof during the scanning of the beam in the longitudinal direction of the thin slit window portion.
12. An electron beam apparatus according to claim 11, wherein said electron beam blanking means comprises means for producing suitable on-off blanking signals supplied to the control grid of the electron beam apparatus.
13. An electron beam apparatus according to claim 11, wherein said electron beam blanking means comprises deflecting means for deflecting the electron beam transversely to the longitudinal axis of the elongated thin slit window portion so that the sides of the supporting bulk member intercept and blank the beam at points where beam blanking is desired.
14. An electron beam COM printer system including an electron beam apparatus of the type set forth in claim 1, an electron sensitive microfilm recording medium, transport means for supporting the microfilm recording medium immediately adjacent the thin window portion of the electron beam recording apparatus for recording data thereon, printer cOntrol circuit means coupled to said electron beam writing apparatus and the transport means for controlling the operation thereof, and character generator circuit means controlled by the printer control circuit means and coupled to the electron beam writing apparatus for controlling the operation thereof in conjunction with the printer control circuit means, said printer control circuit means and said character generator circuit means being controlled from the output of a computer system with which the COM printer is used as a print-out device.
15. An electron beam COM printer system according to claim 14, further including buffer memory means intercoupled with the printer control circuit means and the character generator means for receiving a predetermined number of lines of data to be printed from a computer system central processing unit plus control data for directing operation of the printer control circuit means, said buffer memory means serving to store temporarily the predetermined number of lines of data while each line of data is being printed out by the COM printer thereby freeing the computer system central processing unit for further operations during printing of the stored lines of data.
16. An electron beam COM printer system according to claim 15, wherein the electron beam recording apparatus is of the type including deflecting means for deflecting the electron beam along at least one axis of movement and the window portion comprises an elongated thin slit having its long axis extending in the direction of deflection of the electron beam, said transport means operates to move the microfilm recording medium in a direction transverse to the longitudinal axis of the elongated thin slit window whereby successive lines of data can be recorded raster fashion, said printer control circuit means is coupled to and controls operation of the deflecting means to cause tracing of the electron beam along the longitudinal dimension of the elongated thin slit window portion, and the character generator circuit means controls beam blanking and character formatting.
17. An electron beam COM printer system according to claim 16, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein and wherein the thin slit window portion has a length on the order of one line of recorded alphanumeric characters on microfilm, a width on the order of 75 microns and a thickness on the order of 1,000-5,000 angstrom units.
18. An electron beam COM printer system according to claim 17, further including means enclosing the Lenard window portion of the electron beam apparatus and the microfilm disposed immediately adjacent the Lenard window portion in an enclosed space maintained at a reduced pressure relative to the surrounding ambient atmosphere.
19. An electron beam COM printer system according to claim 16, wherein said window portion comprises an elongated thin slit having its longest dimension approximating the length of a line of microfilm recorded alphanumeric characters and having the thin dimension thereof approximating the height of an individual alphanumeric character recorded on microfilm, and wherein the electron beam recording apparatus further includes additional micro deflecting means for deflecting the electron beam along two transverse axes of movement with respect to the character wide elongated thin slit window portion for writing a line of alphanumeric characters, and beam blanking means for blanking the electron beam at appropriate points along the line of characters to provide for separation and formatting of the written line of characters, said character generator circuit means controlling operation of both said additional micro deflecting means and said beam blanking means.
20. An electron beam COM printer sysTem according to claim 19, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed on the surface of the bulk supporting member by chemical reaction prior to etching the window therein and wherein the thin slit window portion has a width on the order of 75 microns and a thickness on the order of 1,000-5,000 angstom units.
21. An electron beam COM printer system according to claim 16, wherein an array of character masks having openings therein forming alphanumeric characters are arranged along the longitudinal axis of the elongated thin slit window portion and the deflecting means serves to deflect the electron beam to a selected character on one of the character masks, and said electron beam recording apparatus further including micro deflection means disposed intermediate the array of character masks and the first mentioned deflecting means for focusing and deflecting a desired alphanumeric character-shaped electron beam produced by passage of the electron beam through a selected character opening on one of the character masks to cause the same to be directed through the thin window portion at a desired point along its length and thereby record an electron image of the selected character at a desired point on the microfilm recording medium disposed under the thin window portion.
22. An electron beam COM printer system according to claim 16, wherein an extremely fine elongated slit window portion is provided having a width on the order of the diameter of the electron beam and means are provided for repetitively scanning the electron beam in the direction of the longitudinal axis of the elongated window portion together with means for blanking the beam of electrons at appropriate points along the path of travel thereof whereby partial character recording is achieved during each scan of the electron beam, and the transport means moves the microfilm recording medium transverse to the longitudinal dimension of the elongated fine slit window portion intermediate each scan whereby during successive scans of the electron beam raster recording of lines of complete alphanumeric characters is achieved by the accumulation of partial character recordings accomplished during each respective scan of the electronic beam.
23. An electron beam COM printer system according to claim 22 wherein the thin window portion is formed by chemical reaction with the bulk supporting member and the differentially etched bulk supporting member and thin window portion of the electron beam recording apparatus are from the class of materials consisting essentially of silicon-silicon dioxide (Si-SiO2); aluminum-aluminum oxide (Al-Al2O3); tantalum-tantalum oxide (Ta-TaO); titanium-titanium oxide (Ti-TiO); silicon-silicon nitride (Si-SiN); and silicon-silicon carbide (Si-SiC); silicon-aluminium oxide (Si-Al2O3).
24. An electron beam COM printer system according to claim 22 wherein the differentially etched bulk supporting member comprising a part of the electron beam recording apparatus is silicon and the thin window portion thereof is comprised by a thin layer of silicon dioxide previously formed to a desired thickness on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein and the elongated thin slit window portion has a longitudinal dimension on the order of the length of a line of recorded characters and a width on the order of 5 microns with the thickness of the window portion being on the order of 500-2,000 angstrom units.
25. An electron beam COM printer system according to claim 24, wherein the means for blanking the beam of electrons at appropriate points during each individual scan thereof comprises on-off blanking signals supplied to the control grid of the electron beam recording apparatus from the characTer generator circuit means.
26. An electron beam COM printer system according to claim 24, wherein the means for blanking the beam of electrons at appropriate points during each individual scan thereof comprises deflecting means for deflecting the electron beam transversely to the longitudinal axis of the elongated thin slit window portion so that the sides of the supporting bulk member intercept and blank the beam at points where beam blanking is desired.
27. An electron beam COM printer system including in combination an electron beam recording apparatus comprising an evacuated housing having a source of electrons disposed therein and controlled by a control grid, means for directing the electrons in a beam toward one end of the housing, a Lenard window secured to the housing against which the electrons are directed, said Lenard window being fabricated from a differentially etched bulk supporting member secured to the wall of the evacuated housing and having an extremely thin window portion in the form of an elongated thin slit through which the electron beam is directed to permit egress of the electron beam out of the evacuated housing, said elongated slit thin window portion consisting of a material formed on but different than the bulk supporting member and not susceptible to the etchant employed to form the window in the bulk supporting member, deflecting means for deflecting the electron beam along the longitudinal axis of the elongated thin slit window portion, an electron sensitive microfilm tape recording medium, tape transport means for disposing the microfilm tape recording medium immediately adjacent the elongated slit window portion of the electron beam recording apparatus and for transporting the tape past the window portion in a direction transverse to the longitudinal axis of the elongated thin slit window portion, developing means for developing electron images recorded on the microfilm tape recording medium, printer control circuit means coupled to the deflecting means for said electron beam recording apparatus, to said tape transport means and to said developing means for controlling the operation thereof, and character generator circuit means controlled by the printer control circuit means and coupled to the control grid for the electron source of the electron beam recording apparatus for controlling operation of the electron beam recording apparatus in conjunction with the printer control circuit means whereby the electron beam is caused repetitively to scan along the longitudinal axis of the elongated thin slit window portion and is blanked at appropriate points in accordance with characters to be recorded, said printer control circuit means and said character generator circuit means being controlled from the output of an electronic computer system with which the COM printer is used as a print-out device.
28. An electron beam COM printer system according to claim 27, wherein the differentially etched bulk supporting member and thin window portion are from the class of materials consisting essentially of silicon-silicon dioxide (Si-SiO2); aluminum-aluminum oxide (Al-Al2O3); tantalum-tantalum oxide (Ta-TaO); and titanium-titanium oxide (Ti-TiO); silicon-silicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC); and silicon-aluminium oxide (Si-Al2O3).
29. An electron beam COM printer system according to claim 27, wherein an extremely fine slit window portion is provided having a width on the order of the diameter of the electron beam whereby partial character recording is achieved during each scanning of the electron beam across the longitudinal direction of the window portion accompanied with appropriate beam blanking at selected points along the path of travel thereof to provide character spacing and formatting, and the transport means moves the microfilm recording medium transverse to the longitudinal dimension of the elongated thin slit window portion intermediate each scan whereby during successive scans of the electron beam raster recording of lines of complete alphanumeric characters is achieved by the accumulation of partial character recordings accomplished during each respective scan of the electron beam.
30. An electron beam COM printer system according to claim 27, further including buffer memory means intercoupled with the printer control circuit means and the character generator means for receiving a predetermined number of lines of data to be printed from a computer system central processing unit plus control instructions for directing operations of the printer control circuit means, said buffer memory means serving to store temporarily the predetermined number of lines of data plus control instructions while it is being printed out by the COM printer device thereby freeing the computer system central processing unit for further operations during printing of the stored lines of data.
31. An electron beam COM printer system according to claim 30, wherein each character recorded on the microfilm tape recording medium is comprised of a matrix of horizontal coextending and vertical transversely placed dots measured with respect to the longitudinal axis of the elongated thin slit window and with the equivalent of a predetermined number of dot spacings between characters in each line and between each line of characters, the placement of a dot in the formation of a character in a line of characters and the spacing thereof with respect to other dots comprising the character and line of characters being controlled by appropriate manipulation of the beam deflection means and beam blanking means of the electron beam recording apparatus.
32. An electron beam COM printer system according to claim 31, wherein the printer control circuit means comprises dot clock pulse and control circuit means coupled to and responsive to the buffer memory means for generating the basic dot clock pulse signal, horizontal dot position-in-a-character counter means responsive to the dot clock pulse and control circuit means, horizontal characters-in-a-line counter means responsive to the horizontal dot position-in-a-character counter means and coupled to and controlling a ramp generator means for driving the deflection means for deflecting the electron beam horizontally along the longitudinal axis of the elongated thin slit window portion, means for coupling the output from said characters-in-a-line counter means back to the input of the dot clock pulse and control circuit means for inhibiting operation of said dot clock pulse and control circuit means during the retrace portion of the beam deflection means, vertical line-in-a-page counter means coupled to the output from said characters-in-a-line counter means and controlling said tape transport and developing means, vertical-dot-position-in-a-character counter means responsive to the output from the characters-in-a-line counter means, said character generator means comprising a read only memory matrix responsive to the buffer memory means and the output of the vertical-dot-position-in-a-character counter means and digital multiplexing circuit means supplied with said dot clock pulses and controlled by read only memory matrix for controlling the grid driving amplifier supplying the control grid of the electron beam recording apparatus for intensifying the electron beam at points where dots are to be recorded.
33. An electron beam COM printer system according to claim 32, wherein an extremely fine elongated slit window portion is provided having a width on the order of the diameter of the electron beam whereby partial character recording is achieved during each individual scan and recording of a complete character is accomplished by a series of successive scans of the electron beam across the longitudinal axis of the elongated thin slit window portion accompanied with appropriate intensification of the electron beam at selected points as determined by the read onlY memory along the path of travel of the electron beam to provide dot spacing and formatting of the characters being printed.
34. An electron beam COM printer system according to claim 33, wherein the differentially etched bulk supporting member is silicon and the thin window portion is comprised by a thin layer of silicon dioxide previously formed to a desired thickness on the surface of the bulk supporting silicon member by chemical reaction prior to etching the window therein and the elongated thin slit window portion has a longitudinal dimension corresponding to the length of a line of 132 recorded alphanumeric characters plus appropriate spacing between characters and a width on the order of 5 microns with the thickness of the window portion being on the order of 500-2,000 angstrom units.
35. An electron beam COM printer system including in combination an electron beam recording apparatus comprising an evacuated housing having a source of electrons disposed therein and controlled by a control grid, means for directing the electrons in a beam toward one end of the housing, a target window secured to the housing against which the electrons are directed, said target window being capable of emanating radiation exterior of said housing through an extremely thin window portion in the form of an elongated thin slit through which radiation is directed to permit egress out of the evacuated housing, said target windows comprising a bulk supporting portion having a window etched therein and secured to said housing and said thin window portion being formed from a material different from the bulk supporting portion and not susceptible to the etchant employed to form the window in the bulk supporting portion, deflecting means for deflecting the electron beam along the longitudinal axis of the elongated thin slit target window, a microfilm tape recording medium, tape transport means for disposing the microfilm tape recording medium immediately adjacent the elongated slit target window of the electron beam recording apparatus and for transporting the tape past the window in a direction transverse to the longitudinal axis of the elongated thin slit target window developing means for developing images recorded on the microfilm tape recording medium, printer control circuit means coupled to the deflecting means for said electron beam recording apparatus, to said tape transport means and to said developing means for controlling the operation thereof, and character generator circuit means controlled by the printer control circuit means and coupled to the control grid for the electron source of the electron beam recording appartus for controlling operation of the electron beam recording apparatus in conjunction with the printer control circuit means whereby the electron beam is caused repetitively to scan along the longitudinal axis of the elongated thin slit target window and is blanked at appropriate points in accordance with characters to be recorded, said printer control circuit means and said character generator circuit means being controlled from the output of an electronic computer system with which the COM printer is used as a print-out device.
36. An electron beam COM printer system according to claim 35, further including buffer memory means intercoupled with the printer control circuit means and the character generator means for receiving a predetermined number of lines of data to be printed from a computer system central processing unit plus control instructions for directing operation of the printer control circuit means, said buffer memory means serving to store temporarily the predetermined number of lines of data while it is being printed out by the COM printer device thereby freeing the computer system central processing unit for further operations during printing of the stored lines of data.
37. An electron beam COM printer system according to claim 36, wherein each character recorded on the microfilm tape recording medium is comprised Of a matrix of horizontal dots coextensive with the longitudinal axis of the elongated thin slit window and vertical dots disposed transverse to the longitudinal axis of the elongated thin slit window with the equivalent of a predetermined number of dot spacings between characters and each line of characters, the placement of a dot in the formation of a character in a line of characters and the spacing thereof with respect to other dots comprising the character and line of characters being controlled by appropriate manipulation of the beam deflection means and beam blanking means for the electron beam recording apparatus.
38. An electron beam COM printer system according to claim 37, wherein the printer control circuit means comprises dot clock pulse and control circuit means coupled to and responsive to the buffer memory means for generating the basic dot clock pulse signal, horizontal dot position-in-a-character counter means responsive to the dot clock pulse and control circuit means, horizontal characters-in-a-line counter means responsive to the horizontal dot position-in-a-character counter means and coupled to and controlling a ramp generator means for driving the deflection means for deflecting the electron beam horizontally along the longitudinal axis of the elongated thin slit target window, means for coupling the output from said characters-in-a-line counter means back to the input of the dot clock pulse and control circuit means for inhibiting operation of said dot clock pulse and control circuit means during the retrace portion of the beam deflection means, vertical line-in-a-page counter means coupled to the output from said characters-in-a-line counter means and controlling said tape transport and developing means, vertical dot-position-in-a-character counter means responsive to the output from the characters-in-a-line counter means, said character generator means comprising a read only memory matrix responsive to the buffer memory means and the output of the vertical dot position-in-a-character counter means, and digital multiplexing circuit means supplied with said dot clock pulses and controlled by said read only memory matrix for controlling the grid driving amplifier supplying the control grid of the electron beam recording apparatus for intensifying the electron beam at points where dots are to be recorded.