US2173476A - Television system - Google Patents

Description

Sept. 19, 1939. C D K 2,173,476

TELEVISION SYSTEM Filed Oct. 26, 1935 2 Sheets-Sheet 1 MIRROR DRUM Fla. 5

mvsn'roh PETER c. OOLDMARK Sept. 19, 1939.

P.C.GOLDMARK TELEVISION SYSTEM 2 She Filed 061;. 26, 1935 i Y if \v PETER ets-Sheet 2 FIG. 9

INVENTOR OGOLDMARK ATTORNEY Patented 5...... 19, 1939 2,173,47

UNITED STATES PATENT OFFICE ranavrsron srs'mm Peter C. Goldmark, Brooklyn, N. Y., asslgnor to Markia Corporation, New York, N. Y., a corporation of New York Application mm 26, 1935. Serial No. 48,919

I 19 Claims. (01. 178-71) This invention relates to television, and parincreasing enlargement, the observing angle beticularly relates to an improved method and apcomes rapidly restricted. In addition to this paratus for scanning an object field of view and disadvantage, the size of the enlarged image is reproducing pictures corresponding thereto. limited by the dimensions of the lens or lensb'- An object of the invention is to provide an system. In the case oi. method B (2), which 5 improved system whereby the brilliancy oi the remethod is optically identical with the projection produced picture is increased in a simple and of motion picture films and is capable of produceconomical manner. Also, it is an object 0! the ing pictures unlimited in size, the inherent limiinvention to enable the use of relatively small tation resides in the fact that the images must 0 cathode ray tubes at the transmitter and rehave a great initial brilliance in order to permit ceiver, while preserving the quality, size and large enough projection.

brilliancy of the reproduced picture. Further ob- The television system, method and apparatus, jects of the invention will appear from the deof the present invention are predicated upon a scription given hereinafter. combination of the two previously known methods 1 The invention is applicable not only to so- A and Bin conjunction with certain new prin- 16 called direct transmission" systems but also for ciples, so that a new system is created possessing transmitting films. Also, a modification is demany of the advantages of the two known methscribed for televising pictures in natural color. ods but in which new system many of the dis- The methods heretofore carried out for the advantages of such known methods have been I0 projection of television images may be grouped eliminated. I s 20 into two general classes, as follows: In accordance with the present invention, a ,A. The method of directly producing an image televised picture of the desired dimensions and on a screen by a moving light beam, proportions is produced with a single transmitter,

B. The method of optically enlarging an image transmitting channel and receiver, by building up of limited size, either (1) by directly viewing the a plurality of narrowcomponent picture zones 25 image through a lens or lens system; or"(2) by by Scanning 511011 Zones a ly' t ne projecting the image through a lens combinaso that the desired televised picture is constituted tion onto a screen. of such individually scanned picture zones. The

In method A, the size of the image secured is method of the invention also contemplates the 80 limited only by the loss of brilliance. This methuse of a moving'optical element for scanning the or! makes use of most of the so-called scanning picture zones in one directtion, such for instance, systems, working with rotating or oscillating opas a rotating drum provided with a plurality of tical elements such as lenses, prisms, etc. The mirror surfaces, while scanning in a direction brilliance and size of pictures produced by method transverse to the first direction is eiIected by an a". A, assuming constant intensity of the light electronic scanning device. source and constant area of the optical elements, In order to practicably enlarge cathode ray depends upon the distance between the screen and television images, the cathode ray tube, which the moving optical elements, and also'upon the serves as the image producer, must have small angle between those two positions of these eledimensions and must be simple in construction.

40 ments which represent the maximum deflection These factors are paramount for making possible 40 on the screen. The inherent limitations of meinexpensive quantity production of such tubes. chanical systems for high definition pictures are Furthermore, the light efliciency of the enlarging well recognized, the two most outstanding being systemmust be great. extremely low light efficiency and the necessity In accordance with the particular embodiment of using complicated mechanical structural eleoi the television receiver, hereinafter more fully 45 ments. to be described, a small cathode ray tube, about In method B, enlargement of complete teleone inch in diameter, may be used. The deflecvision pictures is capable oi attainment almost tions on its fluorescent screen are projected to a exclusively by means of lenses. This method in viewing screen and are used to build up a picture eludes the use of moving shutters, Nipkow discs, which consists of a plurality of picture strips or drums, slotted discs and drums, etc. and also the zones. These strips or zones. joined together, use of cathode ray images. In the case of method form a complete frame. The optical magnifica- B (l), the directly enlarged and viewed image tion of the projecting lens only enlarges the dedoes not lose its brilliance (glass absorption and fiections (on the end of the cathode ray tube) other minor losses being disregarded), yet, with as many times as the width of one zone compares with the amount of electron-beam deflection. Consequently; the fluorescent spot can be as many times larger as there are number of zones, if compared with a complete picture produced at the end of the cathode ray tube.

The building up of the complete picture from zones in accordance with the system of the present invention, and the production of such zones from the deflections on the tube are accomplished by means or a mirror drum which has at least the same, or a multiple of the number of mirrors as there are zones. Each mirror is tilted, so that while the drum rotates, the deflections at the end of the cathode ray tube are spread apart on the viewing screen, each mirror thereby producing one of the component zones of the complete frame.

- After a complete revolution of the drum, the zones adjoining each other (or distributed otherwise, as it is not necessary to have them in consecutive arrangement) form one or more complete pictures.

The embodiment of the invention just described and the principles upon which it is based, are illustrated in the accompanying drawings, forming part of this specification, and in which:

Fig. 1 shows a picture scanned in two directions in accordance with the invention, the picture 11- lustrated being scanned in five vertical zones, thus actually consisting of five separate narrow pic tures, each of which is scanned by the samenumber of lines;

Fig. 2 illustrates, schematically, the projection of the image in accordance with the present invention;

Fig. 3 shows how "spreading is applied to reduce the necessary deflecting angle;

Fig. 4 shows a top view of the deflected rays, forming the zones, and the complete picture;

Fig. 5 shows the actual size and shape of a spread scanning pattern, while Fig. 5a shows scanning along one line only;

Fig. 6 is a schematic drawing of the optical enlargement and projection;

Fig. 7 is a schematic outline of the transmitter arrangement;

Fig. 8 shows the rotating drum with mirrors arranged thereon for the transmission of motion pictures; and I Fig. 9 shows the successive positions of the film and the zones produced by the mirrors arranged, as shown in Fig. 8, upon the rotating drum.

Referringto Fig. 1, this figure shows a picture area scanned in a plurality of component zones, zl, a2, 23, a4 and 2:5. The picture area shown may be considered to be either a field oi view which it is desired to transmit, or a picture which is be-' ing reproduced at the receiver. For convenience, the receiver will be described firs As shown, each zone is scanned in two directions, from topto bottom (or vice versa) and from left to right (or vice versa). Thus each zone consists of a series of vertically separated horizontal lines, as in conventional scanning, but the length of the lines is equal to the width of only a zone. The complete picture width is obtained by joining a suflicient number of zones next to each other. Thus the length of the picture area in the direction of the lines includes a plurality of zones. The number of lines and zones are independent from each other, and the picture can be broken up into vertical lines and horizontal zones instead of vertical zones and horizontal lines. Figure 1 shows how a picture scanned in 5 vertical zones actually consists of 5 separate narrow pictures each of which is scanned Each mirror is tilted about 5%".

- cathode ray tube and by the same amount of lines. The number of picture elements of such a picture is, of course, the same as that of an ordinary television picture, with the same number of lines as in one zone,since the length of one line is as many times smaller as there are zones.

In the receiving apparatus shown in Fig. 2, the horizontal lines inthe zones on the screen are produced by an extremely small cathode ray tube where the fluorescent spot is deflected only in one direction. The intensity of the fluorescent spot is modulated in the usual way. A lens projects the moving spot (for instance, horizontally deflected) through a rotating mirror drum onto a screen, the rotation of the drum eilecting the vertical deflection. The as many mirrors as there are zones in the picture. diflerently with respect to so that successive mirrors thereby forming the picthe axis of the drum form successive zones, ture shown in Figure 1.

A 5 zone picture can be produced by a drum with mirrors so that 3 complete pictures result from one revolution of the drum. At a rate of 24 complete pictures per second the drum, therefore, has to make 8 revolutions per second or 480 R. P. M. With one mirror centimeters square in area. the drum will have a diameter of The physical dimensions and speed of rotation of the only moving part of this system are, therefore, very small. The cathode ray projector tube is extremely small in size producing a light spot of reasonable size. For a picture composed of 250 lines built up of 5 zones, 1,250 deflections are necessary to complete one frame. At 24 frames per second, 30,000 deflections per secand are needed in order to produce a continuous efl'ect on-the screen. The cathode ray tube being practically inertialess, easily provides such a scanning frequency while the proiecting'lens and drum enlarges the images to any desirable size at comparatively small loss of light.

From a-consideration of Figs, 1 and 2, it will be understood that the diameter of the scanning spot on the fluorescent screen of the cathode ray tube is determined by the magnification between the the screen and the number of lines forming the vertical length of the picture, assuming vertically adjacent lines to be contiguous without overlapp If vertically adjacent lines are not to be contiguous, a suitable change in spot diameter must be made, as will be understood by those skilled in the art. The amplitude of deflection of the light spot on the fluorescent screen of the cathode ray tube will be determined by the horizontal length of'the complete picture,

the magnification, and the number of zones.

For a given magnification is apparent that the amplitude of deflection of the light spot on the screen of the cathode ray tube can be made smaller by increasing the number of zones. For five zones, the amplitude of deflection is only one-fifth the amplitude required for a picture projected in the conventional manner without zones. Thus by using the zoning method of the invention a much smaller cathode ray tube may be employed without changing the diameter of the light tube, and thus without sacrificing briiliancy. Or, .if it desired to use the same size cathode ray tube, by using the zoning'method the diameter of the light spot may be increased (with a corresponding reduction in magnification so as to prevent adjacent lines from overlapping), thus increasing the brilliance of the reproduced picture. In genmirror drum has at least and picture width, it

spot on the screen of the eral, for a cathode ray tube of given size, the dimeter of the fluorescent spot for the zorfisgtem may be made 0 times larger than that for ordinary scanning systems, other conditions being the same, where u is the number of zones employed. Since the area of the fluorescent spot varies as the square of the diameter, the light available for use in the zone method is approximately a times that available for use in non-zone methods employing a cathode ray tube of the same size.

The picture ratio has been assumed so far to be 1:1. The more customary size also used in motion picture fllms is 5:6 (height to width). In order to obtain this ratio it is possible to tilt the mirrors of the rotating drum in such a fashion that the desired ratio results or, as appears to be more satisfactory, to introduce the so-called spreading," which means that the deflections on the screen of the projector tube are spread in a direction at right angles to the original deflections by means of an additional pair of electrodes or. rather, deflecting plates. The necessary deflecting potential is obtained from saw-tooth shape oscillators, the same way as generated for the line-frequency deflections. The amount .of spreading depends upon the required pic'ture ratio primarily, and is controlled by the amplitude of the deflecting potentialas well as by the magniflcation of the optical projection system. The frequency of the deflecting voltage, producing spreading, is equal to the zone frequency which is equal to the number of complete frames per second multiplied by the number of zones. flow the line frequency and zone frequency are kept in step with each other will be shown later under Synchronization.

The general principles of spreading" may be understood by reference to Fig. 3. The optical magnification of the lens-system is denoted g.

If lines are considered to be drawn in a plane' perpendicular to the axis of the drum and normal to the respective lines of intersections of the mirrors with the plane, the angle between adjacent normals is:

21' u- 7 up The angle a will in general be equal to one-half the angle through which a beam of light from the cathode ray tube is deflected by one mirror before the next succeeding mirror comes into operation, as will be understood by those skilledin the art. This angle a is shown in Fig. 3. The

' letter w in the above formula is the number of zones and the letter "9" is the number of complete pictures reproduced in one revolution of the drum. Thus up is the total number of mirrors in the drum.

A spread scanning pattern on the fluorescent screen of the cathode ray. tube is shown in Fig. 5. The amount of spreading (perpendicular to the direction of the lines) will be denoted 0. Since the magnification is e. the height of the spreading produced at the projection screen is 12. Thus Fig. 3 indicates half of this spreading at the top of the projection screen, and the other half at the bottom. It will be understood tha this spreading eflfectspart of the vertical scanning of each zone, the other part being effected by the rotating mirror drum. Thus the deflection angle is produced by the mirror drum without spreading should be reduced to :1, when spreading is employed, in order that the total height H of the reproduced picture may. remain the same. This reduction .may be effected by inarcane .are plane. mirrors (of small curvature, large focal length) creasing the number of mirrors on the mirror drum as is apparent from the formula for a given above. It is ofcourse possible to keep the angle of deflection produced by the mirror drum unchanged, in which case the spreading may be employed to increase the height of the reproduced picture. In such case the diameter of the fluorescent spot may be increased to correspond with the increased picture height.

Fig; 4 illustrates the formation of zones at. :2, an by the tilting of the mirrors with respect to the axis of the drum, this flgure being a top view of the drum and projection screen. As previously stated, the number of mirrors on the drum is equal to at least the number of zones to be produced. Thus each mirror produces one zone, and different mirrors produce diflerent zones. The orientation ofthe mirrors on the drum necessary to produce the zones in their correct positions will be readily apparent to those skilled in the art. The width of the picture (W) is equal to the number of zones (W) multiplied by the width of each zone (Z).

height.

In practice a great advantage of "spreading is that the fluorescent spot is not produced across one single line only but is distributed on a larger area of the screen. Thereby the life of the fluorescent screen is greatly increased and undue overheating of the tube by electron bombardment on a relatively small space is prevented. Figure 5 shows the actual size and shape of a spread scanning pattern, while 5a shows scanning along one line only.

The schematic drawing of the optical enlargement and projection is'shown in Figure 6. In order to use the largest possible part of the light beam collected by the projector lens L, the latter is placed nearly at its focal length from the fluorescent screen and the deflecting mirrors of the drum, therefore, are in the path of an almost parallel beam of light, its diameter D being practically identical with that of lens L.

The image of the moving fluorescent spot is reproduced on the screen thus: first by the lens L. then either by the mirrors M these being concave, representing a positive lens, or by a second lens placed after the mirrors, in which case these The flrst alternative using concave is more favorable, giving a greater light eiflciency and eliminating a second lens which, due to the large angle between mirrors, is bound to introduce distortion. In Figure 6 the mirrors are used as concave projectors having a focal length I: while the focus of lens L is fr. The distance between fluorescent screen and lens L is in while the distance between concave mirror M and screen 8 is be. The'image produced by lens L (imaginary) is at a distance In from the lens and the dEtance between this image (also being the object for mirror M) and the mirror is an.

The diameter of the fluorescent spot is an, and the diameter of its image on the projection screen 8 is m. The ratio Ila/xi therefore, is the magnification of the system, called previously 5.

Following relations can be obtained from the lens equations which for the present case are:

/di+ /bi=1/h and 1'/Ga+ /b:= /f2 further I ri/ir1=a1/bi and rs/y:=az/b:, where b1-a2=s, distance between lens L and mirror M.

The magnification of the entire system then is:

and the distance between projecting mirrors and screen S is:

For instance, lens L has adiameter D=10 cm., focal length fi=20 cm. s=10 cm., a1=20.5 cm. Focal length of mirrors f2=50 cm.

' From Formulae 2 and 1 it follows that ba=77.0

system, substantially the same elements, in similar relationships, are employed, the operation of the transmitter being basedupon thesame principles.

For so-called direct pick-up" transmission, shown in Fig. 7, the scene to be transmitted is projected through an objective lens onto a mirror-drum of substantially the same construction as that used in the receiver. The rotating drum moves the picture, one zone after the other, across a photoelectric slit which is located inside a small cathode-ray tube, thus vertically scanning the zones. This tube, like the receiver projector tube, has an electron gun, concentrating electrodes, and one pair of deflecting plates which move an electron beam in saw-tooth wave oscillations across the photoelectric surface. Since the scanning in this tube occurs in only one direction, (vertical motion of the image carried out by the rotating mirrors) the photoelectric surface is a 'narrow light-sensitive band, of' similar dimensions as the scanning line at the screen of the projector tube in the receiver. This light-sensitive strip consists of a great number of small.

particles of photosensitive material precipitated on a dielectric surface (mica), which is spread over a metal plate. The photosensitive particles, together with the dielectricum and the common metal plate on the other side, form a quantity of small condensers, which are charged by decreasing amounts of electrons due to the photoelectric influence of the projected picture, and are discharged through the moving electron beam. The discharge current varies with the amount of light falling on each condenser; the so varying current, suitably ,amplified, modulates a wireless transmitter. Thus the tube is like the so-called Iconoscope, except that only one set of deflecting plates need be employed.

In Fig. 7, the dotted lines indicate the outline of the entire picture and zones into which the picture is broken up after reflection from the rotating drum. The zones are marked ae and the corresponding mirrors A-E. The same optical calculations and formulae used with the receiver are applicable to the transmitter just described.

For the transmission of moving picture films, the same transmitter scanning tube as is used in the direct pick-up is employed. The rotating mirror drum, however, must be replaced by a different one. Since it is desirable, and as a matter of fact, necessary, to keep the film in steady uniform motion, in order to break up the picture into zones, the tilted mirrors producing the zones must necessarily impart, to each successive zone, an additional movement compensating for the forward movement of the film. I have solved this problem by arranging the mirrors as shown in Fig. 8, wherein the drum-scans, at one revolution, two complete pictures, five zones building up one picture, although, obviously, any number of zones may be used. The anglesv of the mirrors to the axis of rotation of the drum are the same as those used at the receiver drum; each mirror is tilted a small amount more than the preceding one, thus producing the zones. The angle between adjacent mirrors, measured in a plane at right angles to the axis of rotation, is not the same at each mirror, as was true at the receiving drum, but increases gradually from mirror to mirror, each mirror increasing its angle by the same amount. The result is that when the moving film projected through the objective lens onto the drum, is reflected by the latter onto the photosensitive surface, and is moved onefifth of its width forward, the additional angle on the corresponding mirror (first zone) throws the picture backwards simultaneously with the forward movement of the film, thereby neutralizing this movement and producing on the photosensitive surface a picture which is moved the same way as in direct pick-up.

Fig. 9 shows five successive positions of a film frame (corresponding to flve zones) and also the actual zones scanned by successive mirrors on the rotating drum, in conjunction with the scanning tube. It has to be kept in mind that the length of one zone at the film (ordinarily equal to the height of the picture) is equal to one-fifth less than the picture height due to the movement of the fihn during the scanning of a zone. If there are zones and the picture is H inches high, the distance between mirror drum and photoelectric surface has to be chosen so that for given optical system the length of each zone will be:

where his the length of a zone at the plane of the film. This reduction in the length of the zones is what compensates for the forward movement of the film.

It will thus be seen that for the transmission of outdoor scenes (direct pick-up) as well as of motion picture films, the same electron-transmitting tubeis used, this tube having a narrow strip of photosensitive mosaic surface. However, two different mirror 'drums are necessary. For direct pick-up, a drum identical with the receiver drum first described, in which the angles between the mirrors along the circumference are equal may be employed; while for film transmission, a drum is used in which these angles increase the same amount from mirror to mirror, thereby accelerating the scanning from zone to zone so as to obtain a compensation for the forward move: ment of the film.

The television system and'apparatus just described is also suitable for transmitting and receiving images in natural colors, with only slight modifications. The mirror drum is constructed with as many sets of mirrors as there are basic colors used. For a three color system, and z number of zones, 3.2 mirrors are placed on the drum and the drum is rotated three times as fast as with one set of mirrors. Breaking up a picture into five zones, the drum would have fifteen mirrors and would still be rotated at only '72 revolutions persecond for pictures transmitted at the rate of 24 pictures per second.

Each group of mirrors upon the drum is stained with one of the three basic colors, so that after: one revolution of the drum, the picture is scanned three times with three colors within fith of a second. I

Since the picture is produced actually at a rate of 3x24=72 frames per second, the picture frequency can easily be reduced to one-half of this amount, so that each color builds up one complete picture in firth second. No flicker will be noticeable since the actual picture frequency is 36. In such case the electron beam of the projector tube must be deflected at a rate yielding 36 frames per second. Experiment may be resorted to in order to determine whether this frequency can be still further reduced.

At the transmitter of the color system, a similar three-colored mirror-drum projects the scene or picture to be transmitted onto the photoeleotrical surface of the transmitter electron-tube. The photoelectrical particles on the light-sensitive Surface of the tube are produced by a mixture of.

three different photoelectric substances, each of these three being extremely sensitive to only one of the three basic colors used in the system. The light-sensitive mosaic thus composed will accumulate an electric charge only when the rotating three-color drum projects such part of the picture onto the surface of the photoelectric strip which will'free photons of that particular color. The filtering of light in three components is done by the three groups of stained mirrors.

The three different photoelectric substances must be mixed thoroughly enough so that on an area equal to the diameter of the scanning electron beam, the distribution of the three independent substances will be uniform within certain limits. v The problem of synchronization in the present system is comparatively simple. ,The motor driving the mirror drum at the transmitter has on the same shaft a perforated disc, the holes rep- ,resenting a certain group of lines. A light beam directed through these holes acts on a photoelectric cell and produces strong impulses which are transmitted simultaneously with the picture signals. For instance, a picture of 250 lines and 5 zones is to be synchronized. The total amount of lines is 5 times 250 equal to 1,250 lines. At a rate of 24 complete pictures per-second, 30,000 lines are produced per second. The number of pictures per revolution of the drum is 2, the drum having, therefore, mirrors, since 5- zones are used. The drum and the synchronizing disc make 12 revolutions per' second, or per revolution there are 30,000 /12=2,500 lines scanned. Provided a synchronizing impulse is produced at every 10th line, the disc has to have 250 holes. Considering the high synchronizing frequency (3,000 signals per second), it is sufllcient to produce signals after every 10th line only. At the receiver the saw-tooth shape oscillators, working at line frequency, are easily kept in step by the lower (1 6th) frequency.

At the end of each zone, that is, ten times in one revolution of the mirror drum and synchronizing disc, a stronger signal is given. This means that every th hole in the disc is larger by being slotted longer, so that it lets a greater amount of light fall through onto the photocell.

These zone frequency signals constitute what in other systems is called the frame frequency. In-

stead of giving one stronger signal after completion of the entire picture, the present system gives after each zone (in this example 5 zones) a strongimpulse, thereby insuring good synchronization. For the example here calculated, the line frequency of the synchronizing signal will be 3,000 per second, and the zone frequency (framing) signal 24 times the number of zones (5) that is, 120 impulses per second.

The above signals at the receiver act partly on the cathode-ray tube projector oscillator as a frequency divider system (1:10) and partly on a phonic wheel or phonic motor, which drives the mirror drum. The strongzone frequency signals are filtered from the line frequency and, after being suitably amplified, drive the mirror drum.

impulses per second. The motor should make 12 revolutions per second. known relation:

R. P. second=f/t (4) where 7 is signal frequency and t the number of poles on the phonicmotor; for the present example the phonic motor will have 120/12=10 teeth or poles. A self-starting arrangement will start the drum off at the same time that the line frequency oscillator is switched on, and the framing Referring. to a well of the picture is accomplished by rotating the 40 armature of the motor.

I claim:

1. The method of televising an image of a field of view which comprises successively scanning a plurality of component zones of said field 5 of view, each zone, being scanned in a plurality of lines and the length of the scanned field of view in the direction of the lines including a plurality of said zones, transmitting signals derived by said scanning, and reproducing from the transmitted signalsvisual images of the com.- ponent zones in their original relative positions so that the scanned field of view may be viewed in its entirety.

2. The method of televising images of a field of view which comprises repeatedly scanning said field of view in a succession of substantially contiguous component zones, each zone being scanned in a plurality of lines and the length of the scanned field of view in the direction of the lines including a plurality of said zones, transmitting signals derived by said scanning, and reproducing repeated images of said field of view from the transmitted signals at substantially the same area of a selected surface with the component zones in substantially the same relative positions as in the original field of view.

3. The method of televising images of a field of view which comprises repeatedly scanning said field of view in a succession of substantially contiguous substantially stationary component zones, each zone being scanned in a plurality of lines and the length of the scanned field of view in the direction of the lines including a plurality of said zones, transmitting signals derived by said scanning over a single transmission channel, and 'reproducing'repeated images of said field of viewfrom the transmitted signals at substantially the same area of a selected surface with the component zones in substantially the same relative positions as in the original field of view.

4. In the art of television, apparatus which comprises means for repeatedly scanning an object field of view in a succession of component zones, each zone being scanned in a plurality of lines and the length of the scanned field of view in the direction of the lines comprising a plurality of said zones, means for transmitting signals derived by said scanning, and means for receiving said signals and reproducing therefrom repeated visual images of said field of view at substantially the same area of a selected surface by successively reproducing visual images of the successively scanned component zones on said surface, said receiving and reproducing means including means for causing the reproduced visual images of the component zones of the repeatedly scanned field of view to be reproduced at positions separated in the direction of the lines of the reproduced visual images of the component zones andv corresponding to the original relative positions of the zones;

5. In the art of television, apparatus which comprises a scanning device constructed and arranged to repeatedly scan a field of view in a succession of substantially contiguous component zones, each zone being scanned in a plurality of lines and the length of the scanned field of view in the direction of the lines comprising a plurality of said zones, means for transmitting signals derived by said. scanning, and a receiver constructed and arranged to receive said signals and reproduce therefrom repeated visual images of said field of view at substantially the same area of a selected surface by successively reproducing visual images of the successively scanned component zones on said surface by means of a scanning beam, said receiver including means for deflecting said scanning beam to cause the reproduced visual images of the component zones of the repeatedly scanned field of view to be reproduced at positions separated in the direction of the lines of the reproduced visual images of the component zones and corresponding to the original relative positions of the zones.

6. In television transmitters and receivers, apparatus for scanning an area in a plurality of component zones, each zone being scanned in a plurality of lines and the length of the scanned area in the direction of the lines including a plurality of zones, which comprises a line scanning device adapted to scan lines of a component zone, and a. rotating device having a plurality of lightdiverting elements cooperating with said scanning device and constructed and arranged to scan said zones in a direction substantially perpendicular to said lines, said light-diverting elements being positioned and constructed-to cyclically scan zones of said area separated in the direction of said lines.

7. In television transmitters and receivers, ap-

paratus for scanning an area in a plurality of component zones, each zone being scanned in a plurality of lines and the length of the scanned area in the direction of the lines including a plurality of zones, which comprises a line scanning device adapted to scan lines of a component zone, and a rotating device having a plurality of mirrors cooperating with said scanning device and constructed and arranged to scan said zones in a direction substantially perpendicular to said lines, said mirrors being constructed and oriented area in the direction of the lines including a plurality of zones, which comprises a line scanning device and a continuously rotating mirror drum cooperating therewith to successively scan said zones, said mirror drum being constructed and arranged to scan said zones in a direction substantially perpendicular to the direction of scanning of said line scanning device, the mirrors of said mirror drum being oriented to cyclically scan zones of said area separated in the direction of said lines.

9. In television transmitters and receivers, apparatus for scanning an area in a plurality of substantially contiguous component zones, each zone being scanned in a plurality of lines and the length of the scanned area in the direction of the lines including a plurality of zones, which comprises an electronic line scanning device adapted to provide a substantially stationary line scanning pattern for scanning a component zone, and a uniformly rotating mirror drum cooperating therewith to scan said zones in a direction substantially perpendicular to said lines, the mirrors of said mirror drum being canted with respect to the axis of the drum at such angles as to cyclically scan zones of said area separated in the direction of said lines, said angles and the width of said lines being selected so that adjacent scanned zones will be substantially contiguous.

10. In television receivers for reproducing images of a field of view from received signals representing a plurality of component zones of said field of view, each zone having a plurality of lines and the length of the field of view in the direction of the lines including a plurality of zones, apparatus which comprises a cathode-ray tube adapted to provide a luminous line scanning pattern modulated in accordance with the received signals for reproducing lines of said zones, and means for projecting said luminous line scanning pattern onto a reproducing surface including a rotating mirror drum having a plurality of mirrors thereon adapted to deflect the projected lines in a direction substantially perpendicular to the direction of said lines for reproducing component zones, said inirrors being so canted with respect to each other as to project lines corresponding to said plurality of zones to different areas of said reproducing surface separated in the direction of said lines.

11. In television receivers for reproducing images of a field of view from received signals representing a plurality of substantially contiguous component zones of said field of view, each zone having a plurality of lines and the length of the field of view in the direction of the lines including a plurality of zones, apparatus which comprises a cathode-ray receiving tube, means for oscillating the cathode-ray 'beam in said tube to reproduce luminous lines of said zones on the luminous screen thereof, the ,lengths of said lines being substantially constant, and means for projecting said luminous lines onto a reproducing surface including a continuously rotating mirror drum having a plurality of mirrors thereon adaptedto deflect the projected plurality of lines and the length of the scanned I lines in a direction substantially perpendicular to the direction of said lines for reproducing component zones, said mirrors being so canted with respect to eachother as to project lines corresponding to the zones originally separated in the direction of the lines to different areas of said reproducing surface separated in the direction of said lines, the cantlng of the mirrors and the width of the projected lines being selected so that adjacent projected zones will be substantially contiguous.

12. In television receivers for reproducing images of a field of view from received signals representing a plurality of component zones of said field of view, each zone having a plurality of lines and the length of the field of view in the direction of the lines including a plurality of zones, apparatus which comprises a cathode-ray receiving tube, means for oscillating and modulatlng the cathode-ray beam in said tube to reproduce luminous lines of said zones on the luminous screen thereoi, the lengths of said lines being substantially constant, means for projecting said luminous lines onto a stationaryreproducing screen including a uniformly rotating mirror .drum having a plurality for mirrors thereon adapted to deflect the projected luminous lines in a direction substantially perpendicular to the direction of said lines for reproducing component zones, the mirrors of said drum being canted with respect to the axis of the drum at such angles as to project lines corresponding to the zones originally separated in the direction of the lines to areas of said stationary reproducing screen separated in the direction of the lines, and means for slightly deflecting the luminous lines on the screen of the cathode-ray tube which are projected to said reproducing screen in a direction perpendicular to said luminous lines in an amount insufilcient of itself to produce the required deflection of the projected lines at the reproducing screen.

13. In television receivers, apparatus for re-,

producing images from received signals which comprises a cathode-ray receiving tube, means for oscillating and modulating the cathode-ray beam in said tube to reproduce luminous lines on the luminescent screen thereof corresponding to the received signals, means positioned to receive light rays from said luminous lines and adapted to deflect rays forming said lines in a direction substantially perpendicular to said lines so as to produce a two-dimensional image from said lines, means for deflecting said cathode-ray beam in a direction substantially perpendicular to the direction of the luminous lines so that successive luminous lines will be formed on slightly different lines of said luminescent screen, the last-mentioned deflection being insufiicient by itself to produce the desired deflection of the lines in that direction for producing said twodimensional image.

14. In television receivers, apparatusifor reproducing images from received signals which comprises a cathode-ray receiving tube, means for oscillating and modulating the cathode-ray beam in said tube to reproduce luminous lines on the luminescent screen thereof corresponding to the received signals, a rotating light-deflecting element positioned to receive light rays from said luminous lines and adapted to deflect rays forming said lines in a direction substantially perpendicular to said lines so as to produce a twodimensional image from said lines, means for deflecting said cathode-ray beam in a direction substantially perpendicular to the direction of the luminous lines so that successive luminous lines will be formed on slightly difierent lines of 'said luminescent screen, the last-mentioned deflection being insufllcient by itself to produce the desired deflection of the lines in that direction for producing said two-dlmentional image.

15. In television transmitters and receivers,

apparatus -for scanning an area of a moving film in a plurality of successive groups of lines, said lines extending substantially transverse of the direction of film movement, which comprises means for feeding a film with continuous motion, a line scanning device adapted to scan lines of said film in a direction transverse of the film movement, and a rotating device having light-diverting elements cooperating with said line scanning device to repeatedly scan said film in a direction substantially perpendicular to said lines, thereby scanning groups of lines of said film, said light-diverting elements being oriented so that the scanning pattern at the film for scanning successive groups of lines comprising a selected area of the film is displaced between the scansions of the successive groups of lines both transversely and longitudinally ,of the film movement, said longitudinal displacement being such that the scansion of each group of lines begins substantially at a single line extending transversely of said film.

16. In television transmitters and receivers, apparatus for scanning an area of a moving film in a plurality of successive groups of lines, said lines extending substantially transverse of the direction of film movement, which comprises means for feeding a film with continuous motion, a line scanning device adapted to scan lines of said film in a direction transverse of. the film movement, and a rotating device having a plurality of mirrors thereon cooperating with said line scanning device and adapted to repeatedly scan said film while in motion in a direction substantially perpendicular to said lines, thereby scanning groups of lines of said film, said mirrors being oriented so that the scanning pattern at the film for scanning successive groups of lines comprising a selected area of the film is displaced between scansions of the successive groups both transversely and longitudinally of the film move ment, said longitudinal displacement being such that the scansion of each group of lines will begin substantially at a single line extending transversely of said film.

1'7. In-television transmitters and receivers, apparatus for scanning an area of a moving film in a plurality of successive groups of lines, said lines extending substantially transverse of the direction of film movement, which comprises means for feeding a film with continuous uniformv motion, a line scanning device adapted to scan lines of said film in a direction transverse of the film movement, and a rotating device having a plurality of mirrors thereon cooperating with said line scanning device and adapted to repeatedly scan said film while in motion in a direction substantially perpendicular to said lines, thereby scanning groups of lines of said film, said mirrors being tilted in the direction of the path of movement of said film and transversely thereof at such angles as to displace the scanning pattern at the stantially at a single line extending transversely of said film, and said transverse displacement being correlated with the length of the scanning lines at the film so that transversely adjacent receive images of an object field and scan lines of a component zone thereof, said photoelectric surgroups or lines are substantially contiguous. A

18. The method of scanning a uniformly moving film which comprises scanning each of successiveareas of said uniformly moving film in a plurality of successive groups of lines, each of said groups extending longitudinally and transversely of the film movement and the lines of each group extending transversely thereof, said groups being separated in the direction of said lines, and displacing the scanning pattern at said film between the scansions of the successive groups of lines in a direction substantially perpendicular to said lines so that the scansion of each group of lines will begin substantially at a single line extending transversely'of said film.

19. In the art of television, apparatus for televislng a view of an object field of view in natural colors and in a plurality of component zones, each zone being scanned in a plurality of lines and arvaavs the length'of the scanned area in the direction of the lines including a plurality of zones, which comprises an electronic line scanning device having a photoelectric surface therein adapted to face being a mixture of different photo-sensitive materials, said diflerent materials being sensitive to difierent primary colors, and a uniformly rotating mirror drum cooperating therewith to scan said zones in a direction substantially perpendicular to said lines, said mirror drum having a plurality of groups of mirrors thereon, the mir-' ,rors of a single group being adapted to repeatedly scan a single zone and the mirrors of diflerent groups being canted with respect to the axis of the drumat such angles as to scan zones of the field of view separated in the direction of said lines, difi'erent mirrors in a single group being selective to the different primary colors to which said diii'erent photoe ectric materials are responsive.

PETER C. GOLDMARK.

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