US3922581A

US3922581A - Detectors including scintillating means for beam index cathode ray tubes

Info

Publication number: US3922581A
Application number: US386511A
Authority: US
Inventors: David M Goodman
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-03-01
Filing date: 1973-08-08
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25

Abstract

Beam-index cathode ray tubes are depicted in combination with elongated strip-like and coiled light pipe-scintillators. Penetrating radiation which impinges upon the side walls of the elongated light pipe-scintillator creates scintillations in the interior region thereof. These scintillations are in the optical frequency range and are accumulated in strength as they travel through the light pipe. They emerge at exit terminals in concentrated form. The concentrated optical scintillations are used for beam indexing purposes in cathode ray tubes including those with multicolor producing target screens. Single, dual, and triple index signal configurations are described.

Description

United States Patent Goodman 1 Nov. 25, 1975 [5 DETECTORS INCLUDING SCINTILLATING 2,915,659 12/1959 Goodman 313/65 LF MEANS FOR BEAM INDEX CATHODE RAY 3,027,219 3/1962 Bradley t l l l 346/110 TUBES 3,032,659 5/1962 Bacon et al 250/7115 3,081,414 3/1963 Goodman l l t l l t t. 315/10 [76] Inventor: David M. Goodman, 14272 Half 3,567,935 3/1971 dman .7 250/22 X Moon Bay Drive, Del Mar, Calif. 92014 Primary Examiner-Robert Segal [22] Filed: Aug. 8, 1973 ABSTRACT [21] Appl 3865 Beam-index cathode ray tubes are depicted in combi- Related U.S. Application Data Continuation of Ser. No. 119,504, March 1, 1973, abandoned, Division of Ser. No. 562,031, June 2, 1966, Pat. No 3,567,985, which is a continuation of Ser. No. 212,612, July 26, 1962.

U.S. Cl. 313/471; 313/65 LF Int. Cl H01] 31/20; HOlj 29/08 Field of Search 313/471 References Cited UNITED STATES PATENTS 7/1959 Goodman 313/65 LF PLASTlC 28 GLASS 24 INGI INDEX SCINTILLATOR 26 nation with elongated strip-like and coiled light pipescintillators. Penetrating radiation which impinges upon the side walls of the elongated light pipescintillator creates scintillations in the interior region thereof. These scintillations are in the optical frequency range and are accumulated in strength as they travel through the light pipe. They emerge at exit terminals in concentrated form. The concentrated optical scintillations are used for beam indexing purposes in cathode ray tubes including those with multicolor producing target screens. Single, dual, and triple index signal configurations are described.

16 Claims, 14 Drawing Figures US. Patent Nov. 25, 1975 Sheet 1 of2 3,922,581

FIG.I .0 FIG.2 o PIC-3.3

IO l4 l4 PRIOR ART PLASTIC 28 SINGL INDEX SCINTILLATOR 26 -23 METAL 'grsl PLASTIC INVENTOR ATTORNEY DETECTORS INCLUDING SCINTILLATING MEANS FOR BEAM INDEX CATI'IODE RAY TUBES CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of pending application Ser. No. 119,504 filed Mar. 1, 1973 now abandoned.

This application is a division of my co-pending application Ser. No. 562,031 filed June 2, 1966 (now scheduled to issue as U.S. Pat. No. 3,567,985 on Mar. 2, I971 which in turn is a continuation on my application Ser. No. 212,612 filed July 26, 1962.

In my U.S. Pat. No. 3,081,414 granted 12 Mar. 1963, I describe a cathode ray tube which does not require a heated cathode. Instead, use is made of X-rays which are emitted when the target screen of that tube is struck by high energy electrons. These X-rays are detected by scintillators to produce light signals which are transmitted through light pipes to where they impinge upon photon-sensitive surfaces which in turn emit electrons. These electrons then are multiplied, controlled, and focussed to provide a beam of cathode rays. This beam is scanned across the target screen which causes additional X-rays to be generated, thereby to sustain the operation of the circuit. In such an arrangement the cathode ray beam will increase in magnitude until a saturation level is reached. The resultant energization at a given point of the target screen is proportional to this saturation level and is proportional to the duration of excitation. It is possible then to modulate the output of this heaterless tube by varying the saturation level or the duration of excitation. Thus, this arrangement provides a cathode ray tube with a closed loop feedback system which is capable of generating a beam of electrons without requiring the conventional heater-cathode combination.

It becomes desirable in an arrangement such as just described to increase the efficiency of detection of the X-rays. And this is one object of this invention.

Another object of this invention is to provide X-ray detection means of improved sensitivity that may be employed with all types of cathode ray tubes, heaterless or not, having X-ray beam indexing structures.

Still another object of this invention is to provide detection means, responsive to a penetrating radiation, which may be used to increase the sensitivity of beamindex circuitry employed with multi-color cathode ray tubes.

Various other objects and advantages will appear from the following description taken in conjunction with the drawing. The novel features thereof will be particularly pointed out hereinafter in connection with the appended claims. In the drawing:

FIG. 1 represents a cathode ray tube with a scintillator attached to elements of the electron gun of the tube.

FIG. 2 represents a cathode ray tube with a scintillator having a large area of pick-up.

FIG. 3 represents a cathode ray tube with externally disposed X-ray detectors.

FIGS. 1, 2 and 3 represent prior art; they do not form a part of this invention. They are included in the drawing to better illustrate the improvement gained by the instant invention. These three figures are included in the aforesaid U.S. Pat. No. 3,081,414.

FIG. 4 represents a cathode ray tube with a scintillator which is strip-like in form. The scintillator shown is positioned adjacent to the outside surface of the tube envelope.

FIG. 5 represents a cathode ray tube with three separate scintillators which are shown adjacent the inside surface of the tube envelope.

FIG. 6 is a cross-sectional view of the tube in FIG. 5.

FIG. 7 represents a heaterless cathode ray tube where a single scintillator is wrapped around the envelope of the tube.

FIG. 8 represents a heaterless cathode ray tube where two scintillators are provided similar to the construction of FIG. 7 but which are placed adjacent the inside surface of the tube envelope.

FIG. 9 represents a target screen with three different color producing regions. Associated therewith are three different index signals, one for each color producing region.

FIG. 10a illustrates two different levels of excitation of the red strip of the target screen of FIG. 9.

FIG. 10!: illustrates two different periods of excitations of the red strip of the target screen of FIG. 9.

FIG. 11 represents a composite target screen that may be used with a cathode ray tube to provide index signals.

FIG. 11a represents an end view of the target screen of FIG. 11.

FIG. 12 represents various terminations of and a transition for the strip-like scintillators.

Referring now to the drawing in detail, FIGS. 1, 2 and 3, which represent the prior art as previously noted, are similar in that a cathode ray tube has an envelope 10 containing an electron gun 12 which is used to provide an electron beam. Element 14 is common to the three figures in that it picks up electromagnetic radiation generated at the target screen of the tube in response to excitation by the electron beam. In FIG. 1, element 14 is advantageously positioned in that it is located with respect to the target screen so that it picks up substantially equal amounts of radiation from all parts of the screen. In FIG. 2 element 14 advantageously is provided with a large surface for pick-up of the radiation and has a channel provided in its body so that the electron beam may pass from the gun 12 to the target screen. In FIG. 3, elements 14 are positioned outside of the tube and near the plane of the front face of the cathode ray tube.

FIGS. 1-4 represent cathode ray tubes that may be used for color television receivers.

In FIG. 4, the cathode ray tube has an envelope 20 and a target screen 22 positioned on, or near, the from inside surface of the envelope 20. Electromagnetic radiation is shown emanating from the target screen via

paths

36, 34, 32, and 30. In one embodiment of this invention, the target screen 22 is constructed so that this radiation is in the X-ray region of the spectrum. A scintillator 26 associated with rod 24 will be excited by those X-rays which travel along path 36 thereby producing flashes of light. These flashes will be conveyed through rod 24 by a series of internal reflections to an exit termination thereof. It can be seen from the drawing that the area of pick-up of the X-rays is governed by a frontal area of scintillator 26 associated with rod 24. To increase the area of pick-up, and hence the sensitivity of X-ray detection. there is provided in accordance with this invention an elongated scintillating member 28 positioned on the outside of the envelope 20. For

this mode of operation it is to be understood that a horosilicate glass is to be used for the tube envelope, and that high anode voltages are contemplated. Alternatively. ceramic materials such as BeO may be used for the funnel section of the CRT envelope. With this arrangement, X-rays emitted by the screen 22 will strike scintillator 28 along its length. Paths 34, 32, and 30 are shown in FIG. 4 to illustrate this point and to provide a visual comparison with the effect produced by the X- rays travelling along path 36. in effect, the sensitivity of pick-up now is governed by the length of the member 28, (and by the volume) providing a very distinct advantage.

The rod 24 preferably is made of glass since it is placed in the high vacuum region of the cathode ray tube; furthermore the glass rod itself may be the scintillator as can be seen by referring to US Pat. No. 3,032,659 issued to J.F. Bacon, et al., on May l. 1962. On the other hand, the strip-like member 28 may be made of a plastic scintillator since it is placed on the outside of the tube. Plastic scintillators are commercially available which are easy to machine or form; which are sensitive to X-rays; which will respond rapidly to X-ray excitation; and which will provide light flashes which will decay very rapidly after cessation of excitation. One example of such a plastic scintillator is that made by Nuclear Enterprises, Limited, in Winnipeg, Canada under the identification NE-l02. See also Hyman US. Pat No. 2,710,284. For either type of scintillator, the X-rays generated at the target screen 22 will produce the desired result in that they penetrate into the interior of the scintillator where they produce light, and then by the process of internal reflection much ofthe light thus generated is transmitted through the scintillator to an exit termination.

it should be noted that if the radiation to be detected is in the optical frequency range such as in the ultraviolet region then the same general conditions prevail. For example, if a conventional P-16 (or calcium magnesium silicatezcerium activated) phosphor is used for indexing it will generate ultra-violet radiation (centered at approx. 3800 Angstroms) when excited by electrons. This 3800A will be transmitted through most CRT glasses (the coating of carbon or aluminum being removed) and will also create scintillations in the plastic phosphor strip 28. But, if the radiation is not to be detected, but is to be collected and transmitted without change in wavelength, then the advantage gained by penetration and scintillation is no longer available. it is a property of light pipes, or optical fibres, that when radiation of the type it can transmit enters the pipe from a side wall the refraction is such that the radiation emerges from the pipe at the other side. In order for this radiation to be piped it must enter the pipe through entrance terminals, the design requirements for which are well known. The result of such design applied to this case is that the strip 28 can be notched, or serrated, along its length to permit the radiation to enter.

In FIG. 5, a cathode ray tube is illustrated with three strip-

like scintillators

42, 44, and 46 which are symmetrically positioned inside the envelope of the tube. Although not limited thereto, this arrangement is particularly useful for multi-color cathode ray tubes of the beam-index variety. The three scintillators may respond to the same excitation to increase the sensitivity of pick-up by a factor of three. Alternatively, each scintillator may be used to pickup" a different radiation, in which case strips 52, S4, and 56 are used to provide 4 suitable filtering. When the three strips are positioned outside the tube the transmissive qualities of the envelope 40 may also be used to provide filtering. Further elaboration is not considered necessary at this time since the art of filtering X-rays and other radiations is well developed. It is of interest, however. to notice from FIG. 4 that a burst of radiation from screen 22 traverses different paths in striking the scintillation member 28; and after scintillation, the light pulses travel through different lengths in the light pipe. The result is that the pulse oflight created in scintillator 28 will exist for a greater period of time than that of the exciting radiation. in other words, an instantaneous emission of X-rays at screen 22 results in a pulse of light emerging from the exit end of member 28 which exits for a finite time. It also means that the emergent pulse of light is delayed in time. This broadening and delay of the pulse is a function of the length of the member 28, and of the material of which it is constructed. To delay the output pulse of light further, as may be desired in certain applications, alight pipe member 42' may be provided as illustrated in FIG. 5. This additional delay is useful in synchronizing the operation of color cathode ray tubes where radiation from the target is used to provide high speed index signals, High speed, minimum delay circuits generally are required with beam-index tubes intended to provide high resolution multi-color displays.

As an example, consider the index signal being used to provide synchronization of a three color display using presently known vertical strip target screens. For a 20 inch target screen having 250 sets of color triplets there are 750 strips approximately 25 mils in width. The horizontal scanning time, less flyback, is 5 3.5usecs. Then for a linear scanning beam, with a spot size much less than 25 mils, the time spent on each strip is approximately 0.07psecs, or nanoseconds. For a 5 mil beam and a 1 mil index wire an X-ray pulse is fur nished of approximately 17 nanoseconds, a fairly crisp index signal. Plastic scintillator 28 will broaden this index signal; by decay time and by travel time. Typically, the decay time is 4 nanoseconds and is self explanatory, The travel time effect is explained by assuming path lengths 30 and 34 are equal. The radiation via path 34 excites the scintillator, whereupon the light pulse travels to the exit termination near the neck section of the tube. The radiation via path 30 also excites the scintillator, and at the same time, but the light pulse in this case has to travel an additional distance, 33, in the scintillator which takes approximately 2 nanosec onds for a 1 foot length. Thus, the resultant index signal will be lengthened from l7 to 23 nanoseconds, which is still a crisp index pulse. To delay this pulse, member 42' can provide in a 5 foot length approximately 10 nanoseconds of delay which is sufficient to affect vernier control of the overall delay in the index loop. As a matter of comparison, an equal length of co-axial cable with a 500 characteristic impedance, which is frequently used for electrical delay lines, has a delay of approximately 8 nanoseconds. Therefore, the elongated scintillators can greatly increase the sensitivity of detection of the index signal, does so with a tolerable broadening of the signal, and furnishes an optical" signal which may be adjustably delayed in transit.

There is shown in FIG. 6 a sectional view of the tube of FIG. 5 to show the scintillators more clearly. The

scintillators

42, 44, and 46 are shown with

filters

52, 54, and 56. These elements are ribbon-like in shape and, as stated, positioned inside the tube. As an alternative to

elements

42, 44, and 46 plastic scintillator 49 is positioned on the outside of the tube with a filter element 47; and plastic scintillator 51 is shown with a metal jacket 53 for filtering purposes.

With proper design it will be found that the envelope 40 attenuates only slightly the x-rays which are to be detected by these externally positioned scintillators. In contrast thereto, most glasses absorb ultra-violet of wavelength less than 3500A and if such signals are to be detected (or if low energy X-rays are to be detected) then the internal disposition of the strips is preferred. As a practical matter, the choice of tube envelope and the placement of the detector can best be made after the requirements for the CRT are defined. This is so because there are dozens of detectors and a multitude of indexing phosphors that are available; and an almost endless variation in the compositions of glass and ceramics that can be used for CRT envelopes.

In FIG. 7, a heaterless cathode ray tube is illustrated with a scintillating light pipe element 110 wrapped around the envelope of the evacuated tube. This is done to increase still further the quantity of X-rays which are picked up, as should now be clear. The tube operates as follows: at region 100 a particle is ionized, as by some natural cause. The negative ion thus formed, perhaps an electron, is accelerated by a high positive voltage to strike the target screen at point 102. X-rays are produced upon impact and radiate in all directions, typical paths being shown at 104, 106, and 108. Many of these X-rays will create scintillations in member 110 which results in light flashes travelling in both directions as illustrated at 107. The light pipe properties of the scintillator enables these flashes to be transmitted via routes 112 and 114 to eventually impinge upon a suitable photo-sensitive surface 116. Electrons are emitted from 116 and are amplified by secondary emission at dynodes I18 and 120 (voltage connections to the dynodes and to the target screen are not shown) and are forcussed at element 124, which thus provides a stream of electrons which are to be scanned by means symbolized by element 126. Element 124 may be a secondary emission dynode equivalent to

elements

118 and 120. Element 124 may be a transmission type secondary emission dynode. In effect, the latter stages of the secondary emission amplifier and the element 124 comprise an electron lens so that the beam of electrons normally provided by the heated cathode in a conventional electron gun is in this case provided by the element 124. Additional details of construction on the electron-gun-optics are considered conventional, and therefore are omitted. Emanating therefrom is the stream of electrons 128 which is accelerated to strike the target screen at 130. Upon impact, additional X-rays are generated. This process is repeated until a steady state condition is reached; then there is a constant beam current provided at 128. The explanation of the manner in which this electron beam may be modulated will be deferred until the explanation of FIGs. 9, a, and 10b, but at this point it is clear that the requirement for the conventional cathode heater has been dispensed with.

In FIG. 8, another embodiment of a heaterless cathode ray tube is shown. This tube generates two index signals and may be used in a dual index color receiver. This tube provides, in effect, two electron beams which can be modulated. Two spiral shaped scintillators 142 and 144 are intertwined, and positioned adjacent the funnel section of the tube. By means of the scintillation process, these detectors provide two *optical signals, one travelling through light pipe 146 and the other through 148, to impinge upon two photon-

sensitive surfaces

150 and 152. Electrons generated thereby are controlled by

grids

154 and 156, and are subsequently amplified and partially focussed by

dynodes

158 and 160. Then they are further focussed, as at transmission dynode 162, to provide an electron beam 164. Deflection coil 140 provides the scanning action of beam 164. The deflection fields created by coil 140 are separated or shielded from the dynode; 158 and 160 and the focussing means 162 so as not to interact. The drawing is exaggerated to more easily identify the various elements and is not to scale. The shielding, and other design features, of secondary emission multipliers are well known and not described further since they do not assist in the understanding of this invention. It should be noted, however, that the high sensitivity of the scintilla tors provides strong light signals which soon run the secondary emission amplifier section into saturation. Also to be noted is that in this mode of operation if crisp index signals are not required the coils 142 and 144 can be of some length. The operation of this tube is similar to the tube of FIG. 7 except that two different radiations are produced at the target screen. More specifically, there is a first region of the target screen which produces X-rays in a given portion of the spectrum to excite the scintillator 142, and there is a second region which produces X-rays in a different portion of the spectrum to excite the scintillator 144. The beam current that strikes the target screen in the first region produces X-rays, which excites scintillator 142, which causes ejection of electrons from surface 150, etc. The beam current that strikes the target screen in the second region produces different X-rays which excite scintillator 144, which causes ejection of electrons from surface 152, etc. Then, as the beam is deflected from region to region of the target screen the source of the electron beam switches back and forth between the channels represented by

dynodes

154 and 156 thus making it possible to modulate separately the beam currents. This construction would be used to advantage in self-decoding color television receivers. Since the circuits, per se, form no part of this invention, they are not included.

Referring now to FIG. 9 to discuss methods of modulation of the beam of the heaterless CRT there is shown a target screen comprised of phosphor strips capable of emitting red, green, and blue light in response to electron excitation. X-ray producing particles may be admixed with the phosphors or deposited in layers on either side thereof. Alternatively, the chemical elements of the phosphors themselves may be used to generate the X-rays. As an illustration, the red phosphor of F G. 9 with its associated X-ray producing particles, will be considered to constitute the entire target screen of FIG. 7. In this case the electron beam 128 will build up to produce a constant intensity red spot on the face of the tube. This is best explained by referring to FIGS. 9 and 10g taken together. Before proceeding with the description, it is to be noted that each strip of a different color requires its own distinct channel for scintillation detection and for controlled amplification of the electron stream. Thus, a two color tube requires a dual index system, as in FIG. 8. A three color system operating in this mode requires a triple index configuration. As long as the scanning field deflects the electron beam to region 171 to the left of the red strip of FIG. 9 there will be a very small beam current for there are not suit able X-rays generated in this area to sustain the operation of the circuit. Once the electron beam enters the red strip. however. there are X-rays generated, there is color (red) produced, and as illustrated in FIG. "la the beam current builds up. Curves 170 and 172 depict two different levels which the beam can reach. These levels can be governed by controlling the space charges between the dynodes. Typically, a cloud of electrons are allowed to build up in one of the dynode spaces. Then the cloud is released by grid control as is done in other types of electron discharge devices. Alternatively, gain control can be employed in accordance with the teachings of US. Pat. No. 3,036,234 issued to G.C. Dacey on May 22, 1962 to set the saturation level. This patentee describes how semi-conductor detectors may be used in place of the secondary emission dynodes to achieve the same end result, namely a photon generated electron beamv Referring now to FIG. b, there is shown curve I74 which represents a saturated beam current which is gated on for a given period of time. A second curve I76 is shown which represents the same saturated level of beam current but which has a duration larger than that of curve I74. As with the control of the saturation level of FIG. 10a, so the time duration of FIG. 10!) can be controlled by applying suitable potentials (time varying) to the

dynodes

118 and 120 of FIG. 7. For conventional electron guns the results illustrated in FIG. 10a and 10b can be achieved by the use of an aperture and a deflection field in the vicinity of element 124 of FIG. 7; and if further particulars are desired I refer to US Pat. No. 3,038,101 issued to K. Schlesinger on June 5, 1962.

In FIG. 11 a composite target screen is shown which may be used in conjunction with a receiver system employing two different index signals. FIG. 11a is an end view of the composite target screen. Phosphor strips I80, 182, I84, are arranged to be scanned by an electron beam. Aluminum layer 185 is applied over the phosphor strips. Strips I86 and 188 are deposited on the aluminum layer to produce two different index signals. For example, when the electron beam strikes 186, X-rays are produced which are at a given wavelength. And when the beam strikes 188, X-rays are produced which are distinguishable from those produced at 186. Strip 186 may be made of copper particles; strip 188 may be made of nickel. With this construction, the aluminum layer 185 not only provides the conventional function of increasing brightness but it also may serve as a barrier preventing chemical reactions between the index generating strips 186 and I88 and the

light producing strips

180, 182, and 184. A second aluminum layer, 190, is deposited over the index strips to prevent the appearance of an ion spot". Since it need not cover the entire screen this layer is shown terminating in the region 192. In certain modes of deflection, and with certain electron guns, this layer may be omitted. However, when used this layer absorbs the negative ions that are attracted to the target screen. It is chosen of sufficient depth to be opaque to the ions but transparent to the electrons and to the X-rays. This construction reduces the masking effect on the index signals that might otherwise be created by the impact of the negative ions on the

X-ray emitting strips

186 and 188. Alternative construction is indicated by X-ray emitting strips 194 and I98 which are jacketed or surrounded by layers I96 and 199.

ln

FIGv I2 members

200, 204, and 206 represent terminations that may be used with the scintillating strips. Member 200 has a terminal with layer 202 deposited thereupon. This layer, if made of aluminum for exampie, is impinged upon by the light pulses travelling through the scintillator, and is reflected to augment the light emerging from the other end of the scintillator. This layer, if made of an opaque material such as carbon. will absorb the light pulses travelling away from the exit end. This latter arrangement may be desirable when the broadening ofthe light pulses at the output is to be kept at a minumum. Member 204 has an outwardly flared end which may be used at either end of a light pipe, serving to aid the exit of the transmitted light. It may be used. with the coil of FIG. 7 where both ends of the coil are used as exit terminations. The end of member 206 is pinched and may be used to reflect the light from that end. Member 208 is a transition which will convey the light from a circular light pipe to a strip-like light pipe, and vice-versa. Clearly, these terminations may be used with the strips of FIGS. 4, 5, 6, and 8 to obtain the properties desired.

It is believed that the foregoing part of the specification has shown how the primary objects of this invention have been achieved. X-rays. or other penetrating radiations such as ultra-violet radiation, generated by a scanning beam of electrons in a cathode ray tube are detected by providing adjacent to and coextensive with the envelope of said tube a special material which is penetrated by the radiation, which scintillates internally, and which transmits the light generated by scintillation through the material by the process of internal reflection. It has been shown how this feature substantially increases the amount of radiation detected in comparison to an end-on positioning of the detector as disclosed in the prior art. It has shown that this arrangement will provide a greatly enhanced index signal which is sharp and crisp and which can be used for synchronizing the generation of a multi-color display. It has also been shown how such a detector can be used in conjunction with light sensitive means, and the secondary emission process, to provide the electron beam of a cathode ray tube, either monochrome or multi-color.

Having thus described my invention, I claim:

1. In a beam-index color television display apparatus comprising in combination:

1. a cathode ray tube with an envelope containing an image-producing target screen and an electron gun for providing a scannable electron beam;

2. said target screen comprising a repeating array of different color producing strips in register with beam-index strips for generating electromagnetic index radiation indicative of the position of impact of the electron beam on the target screen;

3. means for scanning said electron beam across target screen; thereby to impact said color producing strips and said beam-index strips;

4. detection means responsive to the index radiation thus emitted from said beam-index strips; and

5. means responsive to the output of said detection means for modulating the electron beam thereby to properly excite said color producing strips;

the improvement in said detection means comprising an elongated strip-like scintillator having the properties of a light pipe and being disposed so as to be excited along its length via the index radiation from many of the beam-index strips whereby optical signals gener- 9 ated in its interior region are transmitted via a series of internal reflections to emerge at an exit terminal thereofwhere the optical signals are used to control the modulation of the electron beam.

2. The combination of claim 1 wherein said beamindex strips emit index radiation in the ultraviolet region of the spectrum, and wherein said scintillator is penetrated by and is responsive to the ultraviolet index radiation.

3. The combination of claim I wherein the envelope of the cathode ray tube comprises a faceplate section, a funnel section, and a neck section joined seriatim; and wherein the elongated strip-like scintillator is positioned proximate the funnel section.

4. The combination of claim 3 wherein said elongated scintillator is ring-like in form and positioned near said faceplate.

5. The combination of claim 3 wherein said elongated scintillator is ring-like in form and positioned near said neck section.

6. The combination of claim 1 wherein said elongated scintillator is in the form of a spiral.

7. The combination of claim 1 wherein said elongated scintillator is in the form of a coil.

8. The combination of claim 1 wherein said beamindex strips are comprised of a first series of strips which emit electromagnetic radiation in one region of the spectrum and a second series of strips which emit electromagnetic radiation in a different region of the spectrum, including a first striplike scintillator responsive to the radiation from said first series of strips and a second strip-like scintillator responsive to the radiation from said second series of strips.

9. The combination in claim 8 wherein said first series of strips emit x-radiation and said first scintillator is responsive thereto.

10. The combination of claim 8 wherein said second series of strips emit ultraviolet radiation and said second scintillator is responsive thereto.

11. A beam-index line-screen multi-color cathode ray tube with an envelope having a neck section including an electron gun for providing a scannable electron beam, a faceplate section having associated therewith an electron-sensitive target screen for generating a visible multi-color image in response to the scanning action of the electron beam, and a frusto-conical-like intermediate section which connects the neck section with the faceplate section; said target screen comprising a repeating array of different color producing strips in register with a plurality of spaced apart beam-index strips for generating electromagnetic radiation index signals indicative of the position of impact of the electron beam on the target screen; in combination with beam-index detection means comprising a strip-like light pipe-scintillator which generates signals in the optical frequency range. in its interior region, in response to penetration by the index signals; said light pipe-scintilator having a relatively broad surface disposed adjacent to and coextensive with part of said frusto-conicallike intermediate section of the tube envelope in a radiation receiving relationship with respect to said index signals; said light pipe-scintillator also having at least one relatively narrow surface where said signals in the optical frequency range are concentrated via light pipe action.

12. A beam-index line-screen multi-color cathode ray tube with an envelope containing a faceplate, an image-producing target screen on the interior side of the faceplate, and an electron gun for providing a scannable electron beam; said target screen comprising a repeating array of different color producing strips in register with a plurality of spaced apart electron-sensitive beam-index strips for generating primary index signals, in the optical frequency range, indicative of the position of impact of the electron beam on the target screen; in combination with beam-index detection means responsive to said primary index signals for controlling said electron Beam; the improvement in said detection means comprising a scintillator member disposed in a light receiving relationship with respect to said primary index signals, and characterized in that it yields a secondary optical index signal in response to excitation by the primary optical index signals.

13. The combination of claim 12 wherein said scintillator is in the form ofa light pipe capable of being penetrated by said primary index signals in the optical frequency range, thereby to generate in its interior region said secondary optical index signal.

14. The combination of claim 13 wherein said scintillator is in the form ofa ribbon-like light pipe with a relatively broad surface disposed to receive the index signals and having an exit terminal of relatively small dimensions; and means for receiving and utilizing the secondary optical index signal transmitted, via a series of internal reflections, through the light pipe scintillator to said exit terminal.

15. The combination of claim 12 wherein said spaced apart beam-index strips generate primary index signals in the ultraviolet region of the spectrum. and wherein the scintillator member is responsive thereto.

16. The combination of claim 12 wherein said envelope has a neck section containing the electron gun, and a frusto-conical intermediate section joining said neck section to said faceplate section; and wherein said scintillator member is disposed adjacent to and coextensive with at least part of said intermediate section.

Claims

1. In a beam-index color television display apparatus comprising in combination: 1. a cathode ray tube with an envelope containing an imageproducing target screen and an electron gun for providing a scannable electron beam; 2. said target screen comprising a repeating array of different color producing strips in register with beam-index strips for generating electromagnetic index radiation indicative of the position of impact of the electron beam on the target screen; 3. means for scanning said electron beam across target screen; thereby to impact said color producing strips and said beamindex strips; 4. detection means responsive to the index radiation thus emitted from said beam-index strips; and 5. means responsive to the output of said detection means for modulating the electron beam thereby to properly excite said color producing strips; the improvement in said detection means comprising an elongated strip-like scintillator having the properties of a light pipe and being disposed so as to be excited along its length via the index radiation from many of the beam-index strips whereby optical signals generated in its interior region are transmitted via a series of internal reflections to emerge at an exit terminal thereof where the optical signals are used to control the modulation of the electron beam.

2. The combination of claim 1 wherein said beam-index strips emit index radiation in the ultraviolet region of the spectrum, and wherein said scintillator is penetrated by and is responsive to the ultraviolet index radiation.

3. The combination of claim 1 wherein the envelope of the cathode ray tube comprises a faceplate section, a funnel section, and a neck section joined seriatim; and wherein the elongated strip-like scintillator is positioned proximate the funnel section.

5. means responsive to the output of said detection means for modulating the electron beam thereby to properly excite said color producing strips; the improvement in said detection means comprising an elongated strip-like scintillator having the properties of a light pipe and being disposed so as to be excited along its length via the index radiation from many of the beam-index strips whereby optical signals generated in its interior region are transmitted via a series of internal reflections to emerge at an exit terminal thereof where the optical signals are used to control the modulation of the electron beam.

8. The combination of claim 1 wherein said beam-index strips are comprised of a first series of strips which emit electromagnetic radiation in one region of the spectrum and a second series of strips which emit electromagnetic radiation in a different region of the spectrum, including a first strip-like scintillator responsive to the radiation from said first series of strips and a second strip-like scintillator responsive to the radiation from said second series of strips.

11. A beam-index line-screen multi-color cathode ray tube with an envelope having a neck section including an electron gun for providing a scannable electron beam, a faceplate section having associated therewith an electron-sensitive target screen for generating a visible multi-color image in response to the scanning action of the electron beam, and a frusto-conical-like intermediate section which connects the neck section with the faceplate section; said target screen comprising a repeating array of different color producing strips in register with a plurality of spaced apart beam-index strips for generating electromagnetic radiation index signals indicative of the position of impact of the electron beam on the target screen; in combination with beam-index detection means comprising a strip-like light pipe-scintillator which generates signals in the optical frequency range, in its interior region, in response to penetration by the index signals; said light pipe-scintilator having a relatively broad surface disposed adjacent to and coextensive with part of said frusto-conical-like intermediate section of the tube envelope in a radiation receiving relationship with respect to said index signals; said light pipe-scintillator also having at least one relatively narrow surface where said signals in the optical frequency range are concentrated via light pipe action.

13. The combination of claim 12 wherein said scintillator is in the form of a light pipe capable of being penetrated by said primary index signals in the optical frequency range, thereby to generate in its interior region said secondary optical index signal.

14. The combination of claim 13 wherein said scintillator is in the form of a ribbon-like light pipe with a relatively broad surface disposed to receive the index signals and having an exit terminal of relatively small dimensions; and means for receiving and utilizing the secondary optical index signal transmitted, via a series of internal reflections, through the light pipe scintillator to said exit terminal.

15. The combination of claim 12 wherein said spaced apart beam-index strips generate primary index signals in the ultraviolet region of the spectrum, and wherein the scintillator member is responsive thereto.