Note: Descriptions are shown in the official language in which they were submitted.
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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
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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,
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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
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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
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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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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.
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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
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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
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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
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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
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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
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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.
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