CA1115324A - Beam-index line-screen television display systems - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Beam-index line-screen television display systems are disclosed for generating multi-color images throughout the size range from small direct view cathode ray tubes to projection type wall screen configurations. The image in the small screen display is generated by a scanning electron beam whereas the image generated in the large screen configuration is developed by a scanning optical beam. In both cases the excitation of the image producing target screen is synchronized by beam-indexing features which utilize optical index signals transmitted across the target screen.

Description

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BEAM-INDEX LINl~-SCI~I~N TELEVISION DISPL~Y SYSTEMS

This application is a division of Canadian Serial No. 255,869, filed June 28, 1976.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to Canada Serial No. 951,396 filed February 3, 19~6 and now Patent No. 809,293, issued March 25, 1969.
BACKGROUND OF THE INVENTION
(l) Field of the Invention One aspect of the invention disclosed in the above referenc-ed application which is expanded upon in this application is the feature whereby a scanning beam of energy is made to impinge upon a target screen comprising optical fibers or li~ht pipe members which are used to transmit optical radiation across the target screen. Specifically, optical index radiation is transmitted parallel to the target screen generally from its interior regions to its periphery where it is used for beam-indexing purposes to control the generation of multi-color displays.
Another aspect of the above referenced invention which is expanded upon herein relates to the ~eneration of ]ar~o screoll displays wherein a scanning optical beam excites a line-screen target placed at a distance from the source of the optical beam.
In particular, one embodiment is envisaged wherein a screen is placed against or mounted on a wall, as a picture in a frame, to be excited by a scanning optical beam in order to produce a color picture. Index radiation is developed, to synchronize the excitation of the target screen, and is concentrated for trans-mission either through the air or via electrical or optical cables to a color signal processor which modulates the scanning beam. If a cable configuration is used, it is contemplated that the cable may be run across the ceiling of the room as an added convenience.

(2) Description of the Prior Art Beam-index color cathode ray tubes have been proposed by -l- t~

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-many workers, in many countries, and several working prototyyes have been described in the open literature. Generally speaking they have not been characterizecl by high brightness which rules out their use in projection television schemes. As a consequence most low cost, large screen color displays have resorted to the use of three cathode ray tubes, each developing a different color picture which is projected in careful registration upon a viewing screen. Several high cost projection systems have been developed, and some marketed commercially, which rely on phase gratings, and optically deformed surfaces but these are not related to the instant invention except as to the final result achieved, namely, a large screen full color display operati~g in the television mode. See, for example, True U.S. Patent 3,730,992.
Another system for a large screen television type raster scan-ned display is typified by a three beam laser system equivalent to the three CRT combination referred to above. Pinnow et al U.S. Patent 3,652,956 describes a variation of this type of dis-play in which the red color is produced at the target screen.
To applicant's knowledge, there is no prior art which des-cribes the use of a line-screen beam-index display system which generates a large screen full color display by optical scanning as set forth in applicant's above referenced application.
Furthermore, with respect to either direct view or projection displays the prior art of others is silent insofar as applicant's teachings are concerned wherein the index radiation generated at the viewing screen is detected by the scintillation process, thereby to capture a large amount of the index radiation. Light pipe transmission is utilized in conjunction Wit]l the scintillat-ion process and this too is believed to be set forth in television type raster scan color display apparatus solely by applicant in this application, and in his prior teachings.
The search for a successful low cost projection type color apparatus has persisted for a long time. See, for example, Von Ardenne U.S. Patent 2,265,657 which was filed 35 years ago, 1~153~
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in 1939. And then note the recent comment attributed to the representative of a leading international producer of color television receivers which is reproduced here:

The Prime Minister's statement that no import quotas would be placed on colour television sets coming into Australia has been welcomed by the senior managing director of the Sony Corporation of Japan.
* * *
Mr. Yoshie said in ten years consumers would be able to purchase television sets ranging from one inch to wall size.
ABC Newsroom Canberra, A.C.T., Australia 7:00 p.m., 27 April 1974 The instant invention describes a system which can be -manufactured to yield these results immediately.
SUMMARY S~F THE INVENTION
Generally, the invention disclosed pertains to improved methods and means for generating, collecting, and concentrating optical index radiation from cathode ray tubes or projection type display screens. Optical index radiation which denotes the position of the scanning beam of energy is light piped parallel to the image generating display screen to the periphery thereof. Adjacent the periphery is an elongated light pipe-scintillator which responds to the light piped optical index radiation to produce a secondary optical index signal. The secondary optical index signal is concentrated in the elongated light pipe-scintillator to emerge at an exit end thereof in con-centrated form. This arrangement provides a strong optical index signal, of small dimensions. It also provides for a compact assem bly of the index signal concentrator with the display screen so as to efficiently use the space surrounding the display screen. This arrangêment is particularly advantageous for large screen displays More particularly; the invention to which the claims in this divisional application pertains is a beam-index cathode C~ .

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ray tube comprising means for generating a scannable electron beam, a target screen, and index-signal generating means for providing index signals indicative of the position of impact of the electron beam on the target screen. A
first light-pipe scintillator means has a relatively large receiving region disposed to be energized via the electron beam thereby to generate first optical index signals, and is configured to concentrate, via light-piping action, the optical index signals into a relatively small exit 1~ region. A second light-pipe scintillator means has a relatively large receiving region disposed to be energized via the optlcal signals which leave the exit region thereby to generate second optical index signals at a different wave-length from the first optical index signals, and is configured to concentrate, via light piping action, the second optical index signals into a relatively small exit region.
Preferably the first light-plpe scintillator comprises el~ngate optical fibers disposea adjac2nt the target screen.
Further, the target screen may comprise a repeating array of different color-producing strip-like re~ion5, wherein the elongate optical fibers are disposed in register with the array.
As an alternative, the first light-pipe scintillator may comprise a generally planar member disposed adjacent the target screen ~nd having the general shape thereof. Also, the target screen may comprise a C' 153~4 ~ ~

repeating array of different color-producing strip-like regions in register with strip-like index-signal generating means, the index-signal generating means producing optical radiation in response to excitation by the scannable electron beam. The first light-pipe scintillator is responsive to the optical radiation thereby to generate the first optical index signals.

BRIEF DESCRIPTION OF THE DRAWING
Figure 1 illustrates in block diagram format a display system using a projection type cathode ray tube ~CRT) and a refractive lens system for transmitting the image developed by the cathode ray tube to a target screen.
Figure 2 illustrates in block diagram format a display system using a laser as a source of light which is modulated and scanned across a target screen.

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x Figure 3 illustrates in exac~gerated perspective a target screen, for use with the arrangement of Figures 1 and 2, comprising repeating groups of red, blue, and green light emitting strips interspersed with optical light pipes which generate optical index signals.
Figure 4 depicts a CRT arrangement, alternate to Figure 1, wherein the color picture is developed in the cathode ray tube prior to the image being projected on the target screen. The arrangement of Figure 4 can also be used for direct viewing.
Figure 5 illustrates in exaggerated perspective a target screen akin to that in Figure 3 wherein a plurality of optical light pipes, interspersed with the color emitting strips, transmit their optical index signals to impinge upon the side wall of another light pipe whereby diffel-ent inde~ si-~n.ils alc combined into a signal on a common path.
Figure 6 depicts a target screen, akin to that of Figure 5, inside a cathode ray tube. The combining of the index signals takes place inside the tube envelope.
Figure 7, taken in conjunction with Figures 8 - 11, depicts a sectional view of a cathode ray tube akin to Figure 6 but wherein the plurality of optical light pipes are brought through a frit seal joining the faceplate to the funnel of the tube. Means for combining the optical signals in the light pipes are shown disposed outside the envelope of the tube.
Figure 8 is a side view of the faceplate, frit seal, part of the funnel section, and the optical light pipes of Figure 7.
Figure 9 is a side view in scction of the faccpla~c, frit seal, part of the funnel section, and the target screen of Figure 7.
Figure 10 illustrates, in section, an extension of a light pipe being brought through the frit seal.

1~L153Z4 Figure 11 illustrates an ~tical light pipe being brought through the frit seal, and a secondary light pipe which is used to combine optical lndex signals from a plurality of thc optical light pipes.
Figure 12 depicts a display screen wherein a special substrate is used to generate a primary optical index signal.
Figure 13 is a front view of the display scrcen of Figure 12 and illustrates a light pipe collector which is disposed along the edge of the substrate to generate a secondary optical index signal.

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DESCRIPTION Ol~ T~-IE PRE~FE,I~!'E3 El'IBODI~IE~lTS

In Figure 1, projection type cathode ray tube (CRT) 10 has a target screen 12 which is excited by an electron beam emitted by electron gun 14 and whicll is scanned ~y deflec~io means 16. Scanning currents are provided by raster generator 18. High voltage for the target screen typically is introduced at 15. This construction is conventional.
In one embodiment of the instant invention the target screen comprises a layer of P-16 phosphor which, as is well known, radiates in the near ultraviolet peaking at about 3800 Angstroms when excited by the scanning electron beam.
Modulator 20 controls the intensity of the scanning electron beam as it scans a raster across the target screen. The inputs to the modulator 20 are the luminance signal Y and outputs from color signal processor 22. The processor 22 receives R, B, and G color signals or color difference signals R-~, B-Y, and G-Y.
These color signals are sampled by pulses derived from the index pulses to provide a sequential train of pulses for modu-lating electrodes of the electron gun 14. Varying amounts of luminance signal Y may be added to the sequential train of pulses to achieve optimum color balance. The color signals and raster scan are synchronized in conventional fashion.
The end result of the arrangement of Figure 1 is that a scanning beam of modulated ultraviolet li~ht is ~rojccted upon display screen 26. To synchronize the excitation of the target screen 12 and thence display screen 26, index signal 24 is depicted as emanating from the display screen to feed into processor 22. The scanning beam thereby is modulated to generate a full color picture on the screen 26 via intermediate screen 12. The details of screen 26 will be described with respect to Figure 3 1~153~

De~ails o~ the electronic l-ircuitry are omitted as they are not necessary for a proper understanding of this invention.
Nevertheless for completeness reference is made to my U. S.
Patent 3,564,121 where beam modulation and index control features are set forth. ~eferellce is also made ~o L!~les~ i.ta et al U. S. Patent 3,715,611 for alternates to the conventional P-16 phosphors.
In the arrangement of Figure 1 just described the scanning electron beam generates on target screen 12 a rapidly decaying synthetic ultraviolet replica of the image to be generated by display screen 26. This feature differs from the conventional -flying spot scanner where the o~tical sca2lnln~ am llom tl-e CRT is of constant intensity. Note also that beam-index control of the replica of the image is derived not from the CRT but from the remote display screen. Color signal processor 40 preferably is situated proximate the CRT 10 but may be placed near screen 26 if desired.
In Figure 2 an alternate and conventional arrangement is shown for developing the synchronized and modulate~ scanning light beam. Thus, instead of CRT 10 which generates an intermediate monochrome "image" there is a laser light source 30 modulated by means 32 with color signals furnished by processor 40. The raster generator 38 is synchronized with the color signals R, B, G or R-Y, B-Y, G-Y. Scanner 34 deflects the laser light beam to trace out a raster pattern. PreferaLl~
the scanning beam is in the ultraviolet. Index signal 42 is derived from target screen 36 as will be described next.
In Figure 3 an enlarged perspective is illustrated of a target screen 50 with strip-like members 51, 52, and 53 which produce red, blue and green light, respectively, in response to excitation by the scanning beam of optical energy~ In the _ g _ L153~

preferred en~oclimcnt scanning tIkes place across tllc target screen to excite in sequence an index strip 54, and then 51, 52, 53 followed by index strip 56, etc.
Index strip 54 (and 56, 58, 60) is made of a plastic scintillator such as NE-102 supplied by Nuclear Enterprises in San Carlos, Calif. In response to excitation by the ultraviolet scanning beam, it generates an optical index signal which is light piped, as depicted at 63, to exit terminal 62. At the other end of the index strip 54 it is light piped along length 55- `
- The target screen 50 may be thin, and rollable, in W]liC
case the index strips are filamentary in nature. The~ may ;
also be square as depicted at 55 or round as at 57. The target screen may be rigid, and self-sùpporting, in which case rectangular ribbons o~ light pipe-scintillator 59 and G0 may be preferred.
The optical index signals may be preserved in op~ical form as illustrated at 55, 57, 59 of Figurc 3 or tl~cy m.ly be convor~e-l to electrical signals by photo-detectors illustrated at 62, 64, 66 and 68. The photo-detectors may be spaced from the light pipes as at 64, 66, and 68 or they may be positioned on the exit terminal as at 62. Power supply 70 furnishes bias for the photo-detectors. Conventional P-22 phosphors are suitable materials for the color producing strips 51, 52, 53.
Photo-detectors 62, 64, 66 and 68 may be conventional hig~
speed photo-diodes.
It will be readily appreciated by those skilled in beam-index technology that the screen 50 of Figure 3 providQs all that is needed to fulfill the requirements of screen 26 of Figure 1 and screen 36 of Figure 2. It will also be appreciated that the structure 50 of Figure 3 can be modified for incorpora-tion into a CRT as depicted in Figure 4 where optical index , ~L1532~
siynal 25 is ligtlt pi~ed within the CT~ as set forth i31 more detail in tl~e previously re~erellce~ patellt. ~ec also ~ rnel U. S. Patent 3,311,773 for reference to a material suitable for the index strips in a CRT. Electrical index signal 24 may be derived from the faceplate. Also, optical inde~ 2~' m~y be derived at the faceplate as will be described. The numeration ,-of the other elements in Figure 4 correspond to like elements in Figure l.
The optical index signals in Figure 3 are combilled ~y physically bringing together the exit terminals of the light pipes. A superior arrangement is shown in Figure 5 where the plurality of optical index signals are combined via the scintillation process. Thus, in Figure 5, index strips 71, 72, 73, typically are made of NE-102 which generates a blue-white index radiation in response to excitation by ultraviolet light.
This blue-white radiation is piped up the target screen to impinge upon light pipe-scintillator 74. Typically, element 74 is made of NE-103 also manufactured by Nuclear Entcrprises.
This scintillator has the property of responding to the blue-white excitation of NE-102 thereby to generate longer wavelength optical radiation which is l;ght piped to exit terminals 75 and 76.
Thus, before and after the scanning beam traverses color producing strips 51, 52, 53 it will excite index strips 71, 72, 73 which in turn will excite strip 74. By this proccss a combined optical index signal emerges at 75 and 76 in the form of a series or train of pulses separated in time. It is these pulses which are then used to effect proper registration of the colors on the display screen.
At the bottom of Figure 5, secondary light pipe-scintillator 77 is depicted feeding its output into photo-detector 78. Bias ' . ..
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for the photo-detector is provi~led by power source 79, and electrical output is at 80. Co~lparison of Figure 5 with Figure

3 shows clearly the reduction in electrical connections which are brought about by using the secondary scintillator ~o collect and concentrate the output from the index strips.
Note also the reduction in photo-detectors from four to one.
In practice, the reduction in complexity is much more striking because a typical multi-color display will contain m~ny more than the mere four t4) strips used here for illustration and explanation.
In Figure 6, a target screen a~in to tllat of Figurc 5 is inserted in a CRT. Faceplate 84 is shown joined to funnel - section 82 via frit seal 86. The index signal con~inel 74 is passed through the frit seal to bring the combined optical index signal to the outside of the CRT envelope. Element 74 in this embodiment should withstand CRT processing temperatures.
To comply with this requirement, element 74 can be made of suitable glass tubing to be filled with a liqui~ scintillator after the C~T is completed.
Alternate construction of the CRT of Eigure 6 is illustrated in Figures 7 - 11. Red, blue, and green emitting phosphor strips 51, 52, 53 are deposited on the inside of faceplate 84.
In register therewith are index signal producing strips 71 such as light pipe-scintillators as set forth in my alrlie7~ n. ~ ton~-809,293. Paceplate 84 is joined to funnel section 82 via frit seal 86. F'our of the liaht ~ipes 71 are sl-own bringing tl-eir inde~:
radiation to the outside of the tube through the frit seal 86.
At the bottom of Figure 7, inclex signal com~iner 95 is shown.
It may be made of either NE-102 or NE-103 as both will respond to the excitation of the ultraviolet index radiation light piped through 71. Element 95 is shown to b~ recessed sliglltly , -in Figures 7, 8, and 9 wl-ich is a convenicllce alld not a necessity. ~t the top of Figure 7, the index signal combiner 93 is spaced slightly away from the ~aceplate. Note also from Figure 10 that index light pipe 71 may be coupled to anotl~er light pipe section 97 which may be chosen to be more compatible .-with the frit seal 86.
Note also in Figure 9 that the conventional aluminum layer, desi~nated 91, is situ~ted on top of both the color producing phosphors 51, 52, 53 and the index strips 71, 97.
This simplifies considerably the construction of the CRT
because the complicated and relatively intricate step of laying the index strip on top of the thin and fragile aluminum layer is dispensed with.
Two other ways of eliminating this important step in the manufacture of a color CRT have been set forth previously.
- One way makes use of the light pipe action in the faceplate and funnel section of the C~T to transmit and concentrate the index signal. with frit seal 86 this b~com~s difficult. The other way is to surround the front exterior of the faceplate 84 with a smooth and continuous transparent scintillator 85, such as NE-102, which responds to the index radiation (generated by index strips 71, 97, etc.) transmitted through faceplate~ 84.
The optical index signals developed within the transpare~t scintillator equivalent to 85 are collected and conccntrate~ in a funnel shaped extension surrounding the CRT envelope. In this specification, an elongated additional scintillator 87, such as NE-103, is used to collect and concentrate the index radiation.
See also Figures 12 and 13 which teach in the alternative that faceplate 84 may be made of a transparent scintillator (see Turner 3,311,773) which responds to electron beam .. . ..

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excitation. In this configura~:ion, for a CI~T, the color producing strips 51, 52, 53 are relatively thick to absorb the electron beam and the index strips 71, 97, etc., are supplied by narrow strip-like o}~enillys in ~he color ~ro(~ s~t.~ 9.
Secondary scintillator 89 may be a strip of NE-102 to collect and concentrate the index radiation.
Returning to the wall screen structure, the teachings of Figure 7 are applied in modified form to the structure of Figures 12 and 13. An ultraviolet scanning beam is depicted at 107. Fluorescent materials 51, 52, and 53 emit red, blue, and green light, respectively, in rcsuonse to e~cit~tio~ ~y scanning beam 107. A rectangular block of scintillator 102 supports the color emitting strips 51, 52, 53. A reflective layer 104 such as aluminum may separate the fluorescent strips from the backing of scintillator 102. A clearance passage 100 permits the scanning beam to excite the scintillator 102.
Passage 100 thus becomes the index marker in that material 102 will scintillate when it is impinged upon by the scallnit-y ~e.~
Scintillations generated in the interior of 102 are light piped to its periphery. Positioned adjacent the periphery is secondary scintillator 106 which responds to the optical radiation produced by scintillator 102 thereby to generate the secondary or output optical index signal. Element 106 is shown to surround the rectangular block 102 ~ut it may be ~ositionc~
less than full way around and still function effectively.
Also, filter element 101 is shown if it is desired to reduce the effects of ambient illumination. This filter is narrow band, selected to pass primarily the wavelengths of the ~ptical scanning beam. And, lastly, reflective or blocking member 108 surrounds the remainder of the target screen to prevent excess ambient illumination from exciting the scintillators.
Scintillator 102 may be NE-102 and scintillator 106 may be NE-103, as previously identified. -~

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Attention is drawn to the compact arrangement which results from this config~ration and that of Figures 7 - 10. See Canada Patent 743,198 wllich discusses ~he desir.l~ility of volumetric efficiency.
For detailed information on scintillators which may be used with this invention, reference is made to Organic Scintillation Detectors by E. Schram, Elsevier Publishing Co., 1963. See also Hyman U. S. Patent 2,710,284. For details on frit sealing reference is made to Claypoole U. S. Patent 2,889,952.
Conventional P-22 phosphors are cited previously in this disclosure. Alternatively, common fluorescent paints may be used. It is also possible to use R, G, and B filter elements in combination with white color emitting phosphors as a substitute configuration for the target screen. The light pipe-scintillators may be made of a single material or they may consist of a core and `'cladding" and still ~lOVi~C th~
eatures set forth in this specification.
Although the optical scanning beam preferably is in the ultraviolet region of the spectrum, other wavelengths may be substituted with appropriate changes in strips 51, 52, and 53.
For example, a short-wave blue scanning beam may be used with a blue-to-blue converter selected for color producing strip 52 and with NE-103 used for the index strips 54,56, and 58 of Figure 3.
Whether the display screen is front or rear projection, note that all three colors result from emitted light rather then reflected light. This type of "living" screen provides a wide viewing angle.
Lastly, it was mentioned at the outset of t]liS ~!ccifica-tion that one of the reasons for not employing a beam-index S3~
color CRT as the primary source of the image in a projection television apparatus ~as the inability of the prior art to develop a sufficiently brigllt color picture. Another long standing difficulty in prior art direct view beam-index kinescopes has been that of extracting an index signal with a good signal to noise ratio. Accordingly, it is fair to state that not only does this invention provide a good, crisp index signal for kinescopes but it also solves an even more intense problem, namely, the derivation of a good index signal from a wall screen display.

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A beam-index cathode ray tube comprising means for generating a scannable electron beam, a target screen, and index-signal generating means for providing index signals indicative of the position of impact of the electron beam on the target screen, in combination with first light-pipe scintillator means having a relatively large receiving region disposed to be energized via said electron beam thereby to generate first optical index signals, and being configured to concentrate via light-piping action said optical index signals into a relatively small exit region; and second light-pipe scintillator means having a relatively large receiving region disposed to be energized via the optical signals which leave said exit region thereby to generate second optical index signals at a different wavelength from said first optical index signals, and being configured to concentrate via light piping action said second optical index signals into a relatively small exit region.

2. The combination of Claim 1, wherein said first ' light-pipe scintillator comprises elongate optical fibers disposed adjacent the target screen.

3. The combination of Claim 1, wherein said first light-pipe scintillator comprises a generally planar member disposed adjacent the target screen and having the general shape thereof.

4. The combination of Claim 2, wherein the target screen comprises a repeating array of different color-producing strip-like regions, and wherein said elongate optical fibers are disposed in register with said array.

5. The combination of Claim 3, wherein the target screen comprises a repeating array of different color-producing strip-like regions in register with strip-like index-signal generating means, said index-signal generating means producing optical radiation in response to excitation by the scannable electron beam, and wherein said first light-pipe scintillator is responsive to said optical radiation thereby to generate said first optical index signals.