U.S. patent number 3,624,273 [Application Number 04/778,194] was granted by the patent office on 1971-11-30 for flat screen display devices using an array of charged particle sources.
Invention is credited to Alfred J. Gale.
United States Patent |
3,624,273 |
Gale |
November 30, 1971 |
FLAT SCREEN DISPLAY DEVICES USING AN ARRAY OF CHARGED PARTICLE
SOURCES
Abstract
A display device utilizing an array of electron-emitting sources
insulatively supported opposite a screen member so that each
emitting source is in register with a selected area element of such
screen member. Means are provided for sequentially controlling the
emission of electrons from such sources so that the emitted
electrons impinge in an appropriate sequence upon the selected area
elements of the screen member to produce an image thereon. An
appropriate stereoscopic display of such image may be provided by
using optical filters adjacent each selected area element so that
certain selected portions of the visible spectrum are transmitted
to the receiver from each such element as a result of the
impingement of electrons thereon.
Inventors: |
Gale; Alfred J. (Lexington,
MA) |
Family
ID: |
25112568 |
Appl.
No.: |
04/778,194 |
Filed: |
November 22, 1968 |
Current U.S.
Class: |
348/796;
348/E9.012; 315/169.1; 345/74.1 |
Current CPC
Class: |
H04N
9/12 (20130101); H01J 29/32 (20130101); H01J
1/3042 (20130101); H05B 33/12 (20130101); H01J
31/20 (20130101); H01J 31/22 (20130101); H01J
31/201 (20130101) |
Current International
Class: |
H01J
31/22 (20060101); H01J 29/32 (20060101); H01J
31/10 (20060101); H01J 29/18 (20060101); H01J
1/30 (20060101); H01J 1/304 (20060101); H05B
33/12 (20060101); H04N 9/12 (20060101); H01J
31/20 (20060101); H04n 003/14 (); H04n
009/30 () |
Field of
Search: |
;178/5.4EL,7.3D,7.5D,5.4,5.2,5.4H,5.4F
;313/108,18BC,346,92,103,105,70,71,69 ;315/169TV,94,169 ;340/166EL
;317/234 ;250/213 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Griffin; Robert L.
Assistant Examiner: Martin; John C.
Claims
What is claimed is:
1. A display device comprising
a two-dimensional array of charged-particle emitting sources;
a screen member responsive to the impingement of charged particles
thereon for producing an image;
means for insulatively supporting said array and said screen member
opposite each other so that each of said charged particle emitting
sources is in register with a selected area element of said screen
member; and
means for sequentially controlling the emission of charged
particles from said emitting sources whereby said emitted charged
particles sequentially impinge upon said area elements of said
screen member with which each of said sources is in register so as
to produce an image on said screen member.
2. A display device in accordance with claim 1 wherein said charged
particles are electrons and said screen member is luminescent.
3. A display device in accordance with claim 2 wherein said
supporting means includes an insulative lattice structure disposed
between said array of sources and said screen member for producing
an array of channels, at least one emitting source being oppositely
disposed at one end of each said channels in register with a
selected area element of said luminescent screen member at the
other end of said channel.
4. A display device in accordance with claim 2 wherein each of said
emitting sources is a thin-film device which comprises
a first conductor deposited on an insulating base;
an insulating layer deposited on said base and on said first
conductor;
a second conductor being deposited on said insulating layer at a
region thereof opposite said first conductor; and
means for providing a voltage potential across said first and
second conductors thereby causing electrons to be emitted from said
thin-film device.
5. A display device in accordance with claim 4 wherein said first
conductor is aluminum, said second conductor is gold, and said
insulating layer is silicon dioxide.
6. A display device in accordance with claim 4 wherein
said insulating layer between said first conductor and the region
of said second conductor opposite thereto has a thickness within
the range from approximately 0.03 micrometers to 0.3 micrometers;
and
the region of said second conductor opposite said first conductor
has a thickness within the range from approximately 0.01
micrometers to 0.1 micrometers.
7. A display device in accordance with claim 4 wherein
the thickness of said insulating layer in the region between said
first conductor and the region of said second conductor opposite
thereto has a thickness of approximately 0.1 micrometer; and
said voltage potential is approximately 200 volts.
8. A display device in accordance with claim 2 wherein each of said
emitting sources comprises
a first conductor deposited on an insulator base;
a film of semiconductor compound deposited over a first portion of
said first conductor;
a second conductor deposited on and projecting from a second
portion of said first conductor adjacent said semiconductor
film;
a third conductor deposited on a portion of said semiconductor
compound; and
means for supplying operating voltage potentials to said conductors
for causing electrons to be emitted from said emitting source.
9. A display device in accordance with claim 8 wherein
said first, second and third conductors are formed of material
taken from the group consisting of gold, silver and aluminum;
and
said film of semiconductor compound is formed of tin oxide.
10. A display device in accordance with claim 8 wherein said
voltage potential supplying means includes
means for supplying a voltage potential between said first and said
second conductor of approximately 200 volts; and
means for supplying a modulating voltage potential to said third
conductor.
11. A display device in accordance with claim 2 wherein each of
said emitting sources comprises
a metal film having optically reflective characteristics deposited
on an insulator base;
a first layer of transparent high-temperature insulating material
deposited on said reflective film;
a thin-film heater element deposited on a portion of said
high-temperature insulating layer;
interconnecting means deposited on said insulating layer for
connecting the thin-film heater elements of each of said emitting
sources in series in rows upon said first high-temperature
insulating layer;
a second layer of high-temperature insulating material deposited on
said heaters and said heater interconnections;
a low work function cathode material deposited on a portion of said
second high temperature insulating layer at a region opposite each
of said thin-film heater elements;
means for supplying a heater voltage potential to said thin film
heater elements to heat said elements to a temperature
approximately at or below the threshold temperature required for
significant emission of electrons, and
means for supplying a modulating voltage potential to said low work
function cathode material for causing electrons to be emitted from
said emitting source.
12. A display device in accordance with claim 11 wherein said first
layer of transparent high-temperature insulating material is chosen
to provide maximum transparency in the red and infrared portions of
the frequency spectrum.
13. A display device in accordance with claim 12 wherein
said first and second layers of high-temperature insulating
material are aluminum oxide;
Said thin-film heater elements are made of a material taken from
the class consisting of carbon and tungsten; and
said low work function cathode material is lanthanum
hexaboride.
14. A display device in accordance with claim 11 and further
including a layer of carbon is deposited between said second
insulating layer and said low work function material to prevent
chemical reaction between said layer and said material and to
provide maximum radiatron absorption from said thin-film heater
elements.
15. A display device in accordance with claim 11 and further
including an apertured grid structure mounted adjacent said
emitting source whereby electrons emitted from said source pass
through the aperture of said grid structure.
16. A display device in accordance with claim 15 and further
including
means for supplying a substantially constant voltage potential to
said thin-film heater element whereby said emitting sources are
elevated to a temperature approximately at or below the threshold
temperature required for significant electron emission; and
means for supplying a modulating voltage potential to said low work
cathode material to cause electrons to be emitted from said
emitting source to pass through the aperture of said grid
structure.
17. A display device in accordance with claim 2 wherein each of
said emitting sources comprises
a first layer of insulative material deposited on an insulator
base;
a first conductor deposited on a portion of said first insulative
layer;
a second layer of insulative material deposited on said first
conductor and on a portion of said first insulative layer;
a second conductor forming a layer deposited on said second layer
of insulative material;
an opening etched in said second conductor and said second layer of
insulative material at a region opposite said first conductor
whereby at least a portion of said first conductor is thereby
exposed;
a third conductor forming a cone of conductive material deposited
on said first conductor in said exposed region thereof, the apex of
said cone thereby forming a field emission point; and
means for supplying operating voltage potentials to said first,
second and third conductors for causing electron emission from said
emitting source.
18. A display device in accordance with claim 17 wherein
said first and second layers of insulating material are aluminum
oxide; and
said first, second and third conductors are molybdenum.
19. A display device in accordance with claim 17 wherein
said first conductor is approximately 0.2 micrometers thick;
said second layer of insulating material is approximately 1.0
micrometers thick;
said second conductor layer is approximately 0.2 micrometers thick;
and
said etched opening is circular and has a diameter of approximately
2.0 micrometers.
20. A display device in accordance with claim 17 wherein said
operating voltage potential supplying means includes means for
supplying a voltage potential between said second and said first
conductor the value of which is in the range from approximately 50
volts to approximately 500 volts, the potential at said second
conductor being positive relative to that of said first conductor,
whereby electrons are caused to flow from said field emission point
of said conductor cone through said etched opening.
21. A display device in accordance with claim 17 wherein said
operating voltage potential supplying means includes
means for providing a voltage potential to said first conductor to
maintain said emitting source at a threshold voltage for electron
emission from said field emission point of said conductor cone;
and
means for supplying a modulation voltage potential to said second
conductor.
22. A display device in accordance with claim 17 and further
including
an apertured electrode mounted adjacent said electron-emitting
source between said source and said screen member;
means for supplying a positive voltage potential the value of which
is in the range from approximately 50 volts to approximately 500
volts to said apertured electrode for isolating said emitting
source from said screen member and for preventing charge
accumulation on said second insulating layer.
23. A display device in accordance with claim 4 and further
including a first apertured grid structure mounted adjacent said
emitting source between said source and said screen member the
aperture of said grid structure being opposite said emitting
source.
24. A display device in accordance with claim 23 and further
including a second apertured grid structure mounted adjacent said
first apertured grid structure between said first grid structure
and said screen member, the aperture of said second grid structure
being opposite the aperture of said first grid structure.
25. A display device in accordance with claim 8 and further
including a first apertured grid structure mounted adjacent said
emitting source between said source and said screen member the
aperture of said grid structure being opposite said emitting
source.
26. A display device in accordance with claim 25 and further
including a second apertured grid structure mounted adjacent said
first apertured grid structure between said first grid structure
and said screen member, the aperture of said second grid structure
being opposite to the aperture of said first grid structure.
27. A display device in accordance with claim 2 wherein
said luminescent screen member has a height h and a width w;
and
the distance from said emitting source to said screen member is
substantially less than said width w of said screen member.
28. A display device in accordance with claim 27 wherein said
distance is approximately one-tenth of said width w.
29. A display device in accordance with claim 4 and adapted for
displaying a color image wherein said controlling means for
sequentially controlling electron emission includes
line and frame sequencing control means comprising
first switching means connected to a line voltage potential for
switchably applying said line voltage potential to adjacent pairs
of said first conductors of said emitting sources in a controlled
sequence during a first plurality of frames and for applying said
line voltage potential to interlaced adjacent pairs of said first
conductors during a second plurality of alternate frames; and
modulation sequencing control means comprising
a plurality of second switching means each connected to a second
conductor of said emitting sources;
third switching means connected to said second switching means for
controlling the operation of said second switching means in
response to a luminance signal whereby said luminance signal is
sequentially switched to adjacent groups of three switches of said
second switch means;
means for applying chrominance signals to said second switching
means in synchronism with said sequentially applied luminance
signals;
whereby the operation of said line sequencing control means and
said modulation sequencing control means provides for the
luminescence of said area elements of said screen member to produce
a color image.
30. A display device in accordance with claim 29 wherein each of
said switching means comprises semiconductor switching
elements.
31. A display device in accordance with claim 1 wherein said screen
member includes
an array of optical filter means, one of each of said optical
filter means positioned adjacent to one of each said area elements,
whereby each said area element is adapted to transmit a selected
color portion of the optical spectrum, said area elements thereby
being caused to transmit said selected color portions sequentially
to produce said image.
32. A display device in accordance with claim 31 wherein alternate
lines of said area elements are adapted to transmit the complete
red, green and blue portions of the optical spectrum in sequence
across the width of said screen member; and
intermediate lines are adapted to transmit selected regions of said
complete red, green, and blue portions of said optical
spectrum.
33. A display device in accordance with claim 32 and further
including
a plurality of neutral filters mounted adjacent each of those
filters which are adapted to transmit the complete red, blue and
green portions of the optical spectrum, said neutral filters
arranged to provide approximately 50 percent attenuation of the
optical signal transmitted there through.
34. A display device in accordance with claim 31 wherein
alternate lines of said area elements are adapted to transmit first
selected regions of said complete red, green and blue portions of
said optical spectrum; and
intermediate lines are adapted to transmit second selected regions
of said complete red, green, and blue portions of said optical
spectrum.
Description
This invention pertains generally to display devices and, more
particularly, to a device adapted to provide a substantially flat
screen display for use in television receivers, for example,
wherein the depth of such device is substantially less than the
width of the display screen.
In conventional television receivers the display component is in
the form of a cathode-ray tube, the image being formed on the
phosphor screen thereof. A normal characteristic of such a display
tube is that the distance from the screen to the electron source,
or gun, is approximately equal to the width of the picture which is
presented on the screen. Consequently, relatively bulky cabinets,
or housings, are required for such tubes, particularly in the
larger picture sizes and particularly since the voltage potentials
required to operate such tubes may be as high as 20,000volts or
more.
One method which has been developed in an effort to reduce the
size, and particularly the depth, of such display components has
been to utilize a projection tube system wherein the image is
formed on the phosphor screen of a relatively small cathode-ray
tube and is thereupon optically amplified and projected onto a
larger screen area. In a practical sense, however, such an approach
does not measurably reduce the overall size and bulk of the display
system and, moreover, the picture quality and brightness are
degraded. Further, even higher voltage potentials are generally
necessary for operating such a projection cathode-ray tube
system.
Other attempts to reduce the size of the display component and to
provide a substantially flat screen display system have included
systems for causing an electron beam to travel essentially parallel
to, rather than perpendicular to, the picture plane, the beam being
deflected onto the picture plane only over the last portion of its
path of travel. Such an approach does not measurably reduce the
size of the electron beam tube involved and materially adds to the
complexity of an already complicated system, particularly when such
an approach is used for color television display.
This invention provides a system in which the depth of the display
device is substantially less than the dimensions of the display
screen on which the image is presented, such depth being
approximately an order of magnitude less than the picture width,
for example. Moreover, the overall display device of the invention
is relatively lighter in weight than presently used display
devices. A cathode-ray tube, for example, utilizes relatively heavy
and thick glass, or other materials in order to safely support the
evacuated tube against the external air pressure thereon. Such
extreme glass weight and thickness is not required in the display
device of the invention.
Moreover, in present day cathode-ray tubes the screen is generally
curved, that is it can be represented as a portion of a sphere,
particularly in large size cathode-ray tubes. This invention,
however, provides a substantially planar, or flat, screen on which
the image is presented and does not require excessively thick or
heavy glass as is usually needed to support flat surfaces so as to
prevent collapse due to external air pressure. Consequently, the
internal reflections, which normally arise in thick glass systems,
are avoided and the picture contrast is not degraded thereby.
Further, the voltage potentials used in operating the display
device of the invention are relatively low in comparison to those
potentials needed for cathode-ray tube structures. Thus, not only
are electrical hazards avoided but also hazards due to X-radiation,
which have been found to exist in present day cathode-ray tubes,
are also eliminated.
The display device of the invention achieves these advantages by
utilizing an array, or matrix, of charged-particle emitting
sources, such as electron-emitting cathode structures, and a
luminescent screen member, such as a phosphor screen, which
responds to the impingement of such charged particles to produce an
image thereon. Such sources and screen member are supported at
either end of an appropriate insulative lattice structure so that
each emitting source is oppositely disposed from and in register
with a selected area of the luminescent screen. By appropriately
controlling the emission of electrons from the emitting source in a
desired sequence in accordance with a transmitted picture, for
example, such electrons are caused to impinge in a suitable
corresponding sequence upon the screen to produce the desired image
thereon.
In the invention the distance from the emitting sources to the
screen is substantially less than the dimensions of the screen,
particularly being in the order of one-tenth, or less, of the
screen width. Moreover, the voltage potentials required to energize
the sources and to accelerate the electrons toward the luminescent
screen are relatively small in comparison with present cathode-ray
tube operating voltage potentials. The electron-emitting sources
may be of various types, such as thin-film devices or other solid
state structures, thermally emitting cathode structures, and field
emission cathode structures, and the like.
The specific details of particular embodiments of the invention can
be described more easily with the aid of the accompanying drawings
wherein:
FIG. 1 shows generally a perspective outline drawing of the display
device of the invention depicting the dimensional relationships
therein;
FIG. 2 shows a sectional view along the direction of line 2--2 of
FIG. 1 showing a portion of one embodiment of the array of emitting
sources;
FIG. 3 shows a sectional view along the direction of line 3--3 of
FIG. 1 showing a portion of one embodiment of an array of screen
elements;
FIG. 4 shows a sectional view along the direction of line 4--4 of
FIG. 1 showing the relationships between the emitting sources, the
luminescent screen of FIGS. 2 and 3 and the support structures
therefor;
FIG. 5 shows a more detailed view of one portion of the structure
shown in FIG. 4;
FIG. 6 shows a sectional view of an alternative embodiment of the
structure shown in FIG. 4;
FIG. 7 shows a sectional view of another alternative embodiment of
the structure of FIG. 4;
FIG. 8 shows a sectional view of an alternative embodiment of the
structure of FIG. 4 using a different form of emitting sources;
FIG. 9 shows another alternative embodiment of the structure of
FIG. 4 utilizing another different form of emitting sources;
FIG. 10 shows another alternative embodiment of the structure shown
in FIG. 4 utilizing still another different form of emitting
sources;
FIG. 11 shows a more detailed view of one of the emitting sources
shown in FIG. 10;
FIG. 12 shows a schematic diagram of a portion of the circuitry
used to energize the emitting sources and adapted to be used with
such sources as shown in FIG. 4 or the alternative embodiments of
such sources as shown in FIGS. 8, 9 and 10;
FIG. 13 is a schematic diagram of an alternative arrangement of the
circuitry of FIG. 10 adapted to be used for energizing the emitting
sources of FIGS. 4, 8. 9 and 10;
FIG. 14 is a graph of the visible portion of the frequency spectrum
which graph is useful in describing the application of the
invention to stereoscopic displays;
FIG. 15 is a diagram illustrating one arrangement of the array of
display area elements useful for stereoscopic displays; and
FIG. 16 is a diagram showing an alternative arrangement of the
array of display area elements of FIG. 15.
FIG. 1 shows an outline perspective drawing depicting the
relationships among the height, width and depth dimensions of a
typical display device of the invention. As shown therein, the
front planar surface 20 represents generally the plane of a
luminescent display screen on which an image is presented. Such
screen has a height h and width w , as shown. An array of
charged-particle emitting sources is mounted generally at the rear
planar surface 21 of the device. The thickness, or depth, of the
device, shown in the drawing as dimension d , is substantially less
than, and preferably of an order of magnitude approximately
one-tenth of, the width w of the display screen at surface 20. The
detailed structure of one particular embodiment of a display device
conforming to the general outline configuration shown in FIG. 1 is
discussed first with reference to FIGS. 2, 3 and 4.
FIG. 2 shows a view of a portion of the charged-particle emitting
sources in the direction of the line 2--2 of FIG. 1 looking toward
rear surface 21 thereof. An insulative lattice structure 22 forms
an array of evacuated channels 23, as shown most clearly in FIG. 4.
The rhombic cross section of each such channels conforms generally
in its dimensions to the conventional width:height ratio of the
display screen at surface 20 of FIG. 1, such dimensions in
accordance with normal television standards having a 4:3 ratio.
Each channel is in register at one end with a specific area element
of a luminescent display screen. More particularly, for color
display purposes each channel is in register with a specific color
area element thereof. For example, as shown in FIG. 2, channel 23a
may be associated with the red content of a transmitted picture,
channel 23b may be associated with the green content, thereof, and
channel 23c may be associated with the blue content, thereof.
Although shown in rhombic cross section, the evacuated channels may
be of other convenient configurations such as circular, for
example.
Each evacuated channel 23 is in register at the other end with a
separate electron-emitting source. Thus, the lattice structure
provides for electrical and mechanical separation of the emitting
sources at the cathode end as well as of the display screen area
elements at the anode end, as described more clearly with reference
to the subsequent figures.
For the particular embodiment described with reference to FIGS. 2,
3 and 4, a separate channel is shown as associated with each color
element. However, since the electrons emitted from the cathode
source end travel to the anode screen end with relatively small
angular dispersion, such separate channels may not necessarily be
required and each channel may be in register with more than one
cathode source and corresponding anode display screen element.
Enough insulative support material must be utilized, however, to
withstand reliably the external air pressure on the substantially
flat display and cathode surface planes of the device. In order to
describe the operation of the device in a clearest manner, the
discussion which follows considers an embodiment utilizing separate
channels for each cathode and corresponding anode element
combination, the overall device being described for use in
generating a color picture.
As shown in FIGS. 2, 3 and 4, at the emitting or cathode end 24 of
the display device, a plurality of conductors 26 form the upper
electrodes of a suitable thin-film cathode structure 30 and a
plurality of conductors 27 form the lower electrodes thereof. As
seen in FIG. 2, conductor 26a is associated with channel 23a,
conductor 26b is associated with channel 23b and conductor 26c is
associated with channel 23c, such triad sequence being repeated
across the entire array. When a trio of adjacent conductors 26
(e.g., 26a, 26b and 26c) and a pair of adjacent conductors 27 are
energized to cause electron flow, a specific triad of emitting
sources, one source corresponding to each color, and only one
specific triad is activated.
FIG. 3 shows the anode end 25 of the display device oppositely
disposed with respect to the cathode end at the other end of
insulative lattice structure 22. At such anode end an array of
phosphor area elements 28 is shown associated with each channel 23.
Each phosphor element is associated, as described below, with a
specific color. Thus, phosphor element 28a, for example,
corresponds with the red content, phosphor element 28b with the
green content, and phosphor element 28c with the blue content.
FIGS. 4 and 5 show in more detail the overall cathode and anode
structures. In such figures, each of the thin-film cathodes 30 is
formed on an insulator plate 29. Conductors 27, typically made of
aluminum, form the lower electrodes of each of the rows of
electron-emitting cathodes 30. An insulating compound layer 31,
typically made of silicon dioxide, is formed over conductors 27. In
the region 32 of each cathode proper the thickness of the
insulating compound layer 31 is less than that of the intervening
regions 33. In a preferred embodiment, for example, the thickness
of layer 31 in region 32 lies in the range from 0.03 to 0.3
micrometers and may typically be 0.1 micrometer. In the intervening
regions 33 the insulating layer, for example, may be on the order
of 1.0 micrometers thick, or greater.
Columns of conductors 26 are formed over silicon dioxide layer 31
such conductors being, for example, made of gold and formed in
relatively thick layers, on the order of 0.1 micrometer or greater,
adjacent the region 33 where the insulator layer 31 is at its
thickest. Conductors 26 are relatively thin where they are formed
adjacent regions 32 of insulator layer 31. In such regions,
conductors 26 may be a few hundredths of a micrometer thick, and
typically may be 0.03 micrometer.
At the opposite end of insulative lattice structure 22 are the
phosphor elements, or dots, 28 which elements are interconnected by
a conductive film 34, both the phosphor elements and the
interconnecting conductive film adhering to a transparent face
plate 35. An array of multidielectric filters 36, the purpose and
more detailed description of which is discussed below, may
optionally be interposed between the face plate 35 and the layer of
phosphor elements and conductive films as shown in FIG. 4.
When a positive potential difference exists from the relevant
conductor 26 to a corresponding relevant conductor 27, a particular
cathode structure will emit electrons into a corresponding vacuum
channel 23, the value of the potential difference needed for this
purpose being dependent on the dimensions of the cathode structure.
Typically for a silicon dioxide layer 31 of approximately 0.1
micrometer this potential difference is in the order of 200 volts.
In the quiescent, or nonemitting, state conductors 26 and 27 are
held at approximately equal potentials relatively close to ground.
In synchronism with the transmitted picture information each
conductor 27 (or conductor pair in the case of a color display) is
sequentially switched to a negative potential equal to the
threshold for electron emission between it and the quiescent
conductor 26. Depending on the brightness content, or luminance, of
the picture of the transmitted picture information, positive
potentials are applied sequentially, and in synchronism with the
transmitted picture, to conductors 26 so that each cathode
structure is caused to emit electrons in short bursts, the number
of electrons being determined by the luminance information of the
transmitted picture element. In the case of a color display, the
conductors 26 are arranged in triads, each member of the triad
receiving a voltage potential determined by the luminance (or
brightness) and chrominance (or color) information in the
transmitted signal. In a typical operation the switching signals
applied to conductors 27 may be in the range of -50 to -500 volts
and the modulating signals applied to conductors 26 may lie in the
range from 0 to 100 volts.
The electrons so emitted by each cathode structure during such
operation are accelerated with a relatively small angular
dispersion toward the anode plane 25 which for such purposes may be
held at a voltage potential in the order of 5,000 volts or higher.
The electrons accelerated from each cathode structure 30 impinge
upon the corresponding oppositely disposed phosphor dot 28 exciting
it to luminescence. For monochrome display a substantially white
light emitting phosphor element is selected for each phosphor dot.
Alternatively, the dot configuration for monochrome operation may
be preferably and more economically replaced by a continuous thin
layer of phosphor material, in which case each evacuated channel
lies opposite to and in register with a selected area element
thereof.
In the case of a color display, the materials of each of the
phosphor dots 28 are selected to emit the appropriate hues.
Alternatively, for color operation the phosphor may be selected to
emit substantially white light, either a continuous thin layer of
phosphor material or as a dot configuration, which white light upon
luminescence is filtered through appropriate multilayer dielectric,
or other, filters 36, as optionally shown for this purpose. The
filters are appropriately designed to transmit the desired color
portions (i.e., red, green, or blue) of the visible spectrum
through transparent face plate 35.
Embodiments of the circuitry required to provide the appropriate
sequence of operations for reproducing an overall image on the
phosphor display screen are discussed below with reference to FIGS.
12 and 13. Before describing such circuitry, however, alternative
embodiments of the electron emitting sources are first described
with reference to FIGS. 6-11.
In FIG. 6 a structure similar to that shown in FIG. 4 is
illustrated, with like reference numerals referring to like
portions thereof. In FIG. 6, however, the insulative lattice
structure 22 is replaced by two insulative lattice structures 37
and 38 between which are placed a plurality of apertured vertical
conductors, or grids, 39 having apertures 40. The overall structure
shown in FIG. 6 is, therefore, in the nature of a triode
configuration, several modes of operation of which are possible.
For example, in one mode conductors 26 are all connected together,
preferably to a ground potential, and conductors 27 (or appropriate
conductor pairs for color display as discussed above) are
sequentially switched in the manner described above with reference
to FIG. 4 to a voltage which provides a sufficiently high potential
difference between conductors 26 and 27 to permit maximum electron
emission and flow therefrom. Thus, the potential difference applied
thereto is greater than that discussed with reference to FIG. 4
wherein a potential difference related to the threshold value of
electron emission was used.
A modulating bias voltage is thereupon sequentially applied to the
grid structure 39 in appropriate synchronism with the transmitted
picture information thereby permitting a suitable fractional
portion (or all, if necessary) of the electrons emitted from the
cathode structures 30 to flow through aperture 40 and thereby be
accelerated to the anode plane 25. An advantage of utilizing such a
grid or triode configuration over the diode configuration in FIG. 4
is that the capacitance of the individual grids 39 to other parts
of the system is considerably less than that of the conductors 26
of FIG. 4. The system of grids can therefore be driven with
considerably less power, and thus, more economically than the
system utilizing merely the thin-film cathode 30 in the previous
figure.
In FIG. 7 a structure similar to those shown in FIGS. 4 and 6 is
illustrated, with like reference numerals referring to like
portions thereof. In FIG. 7 the insulative lattice structure is
formed in three sections 41, 42 and 43. A plurality of apertured
horizontal conductors, or grids, 44 having apertures 45 is mounted
between sections 41 and 42, such grids being arranged in rows in a
horizontal configuration. A plurality of vertically oriented grids
46 having apertures 47 are placed between sections 42 and 43, such
grids being substantially the same as grids 39 described above with
reference to FIG. 6. Several alternative modes of operation of the
configuration shown in FIG. 7 are possible. In one such mode, all
of the conductors 26 of cathode 30 are connected together to a
common voltage potential so that all of the cathodes continuously
emit electrons. Conductors, or grids, 44 are normally held at a
voltage potential which prevents electron flow through apertures 45
and are sequentially switched in synchronism with the transmitted
picture signal information to permit a substantial fraction of the
electrons from each cathode to be accelerated through apertures 45.
The grids 46 are sequentially biased in synchronism with such
transmitted picture signal information to modulate the quantity of
electrons which are ultimately accelerated to the anode end for
impingement upon phosphor elements 28. An advantage of the
arrangement in FIG. 7 is that the capacitance associated with the
individual conductors 44 is considerably less than that associated
with the individual conductors 27.
Having thus described various particular embodiments of the
invention utilizing the cathode structure of FIG. 5, either in
diode configuration, triode configuration, or tetrode configuration
as in FIGS. 4, 6 and 7, respectively, FIGS. 8-11 are now used to
describe similar structures utilizing other forms of cathode
structures. In comparing FIGS. 8-11 with FIGS. 2-7, it should be
noted that like reference numerals refer to like elements
thereof.
In FIG. 8 an alternative form of a solid state cathode 48 is shown.
The array of cathodes used therein comprises a set of vertical
conductors 49 contiguous to the insulative structure 29 together
with a set of horizontal conductors 50. Typically, conductors 49
and 50 are of metal of which gold, silver, and aluminum have been
found suitable. Between conductors 49 and 50, in the region of each
cathode source 48, a film of semiconductor compound 51 is placed,
such compound, for example, typically being composed of tin oxide.
Projections 52 placed on a portion of conductors 49 rise to the
surface of the semiconductor film 51. Electrons are emitted from
the metal semiconductor junctions when a voltage potential
difference is applied from conductor 50 to conductor 49 across
semiconductor film 51. In operation, conductors 50 are sequentially
switched in synchronism with the transmitted picture signal
information to a voltage potential, relative to the quiescent
condition of conductors 49, which is the threshold voltage for
electron emission. Typically such voltage potential is in the order
of 200 volts. Additional modulating voltage potentials are
sequentially applied to the vertical conductors 49 to control the
number of electrons emitted from each cathode in accordance with
the point-by-point luminance and chrominance values of the
transmitted picture content. The remaining details of the image
formation at the anode plane are substantially similar to those
described in conjunction with FIG. 4, for example, and such details
are not repeated here.
As with the thin-film cathodes of FIGS. 4-7, a triode configuration
similar to that described in conjunction with FIG. 6 and a
multielectrode configuration similar to that described with
reference to FIG. 7 can be used as further alternative embodiments
to the diode configuration of FIG. 8. Consequently, such structures
are not further illustrated in detail here.
FIG. 9 shows an alternative embodiment utilizing different
electron-emitting sources. In such figure a reflective film 53 of
silver, or other metal chosen for maximum reflectivity in the red
and infrared portions of the optical spectrum, is deposited on
insulator 29. A layer 54 of transparent insulating material,
typically aluminum oxide, or other high-temperature insulator
chosen for maximum transparency in the red and infrared portions of
the optical spectrum, is deposited over reflective film 53. Layer
54 is in the order of a few micrometers thick, typically being
approximately 2.0 micrometers. A plurality of thin-film heaters 55,
typically of carbon or tungsten or other high-temperature
conductive material, are deposited on insulating layer 54,
interconnections between the heaters being also deposited on
insulating layer 54 so that the heaters are connected in series in
rows. A further layer 56 of high-temperature insulative materials,
such as aluminum oxide, is deposited over the heaters and heater
interconnections as well as portions of layer 54. Electron-emitting
cathodes 57, typically of lanthanum hexaboride or other low work
function material, are deposited on high-temperature insulative
layer 56. Cathodes 57 are interconnected in columns, or
alternatively in rows, depending on the electrical functions
associated with the apertured grid structures 58 as discussed
below. To prevent chemical reactions between the cathodes 57 and
the insulative layer 56, and also to provide maximum radiation
absorption from the heaters 55, thin layers of carbon (not shown)
may be deposited on the insulating layer 56 prior to the deposition
of cathodes 57.
A grid structure 58 is mounted between two insulative lattice
structures 59 and 60 in a manner similar to that described above
with reference to FIG. 6, such grids 58 having apertures 61 as
shown.
In one mode of operation of the embodiment shown in FIG. 9, the
grid structures 58 are held at a constant potential and the
cathodes 57 are interconnected in columns. The rows of heaters 55
are sequentially switched in synchronism with the transmitted
picture signal information. The thermal inertia of such
heater/cathode structures is so low that sufficiently fast
switching times are obtainable, particularly when bias power is
applied to the heater rows elevating all of cathodes 57 to a
temperature just below the threshold for significant electron
emission in the quiescent condition. Modulating voltage potentials
in conformity and synchronism with the transmitted picture
information are sequentially applied to the columns of cathodes 57
so that the quantities of electron flow through the apertures 61 of
grids 58 are controlled by the point-to-point luminance (and
chrominance) content of the picture. The further details of picture
formation are substantially similar to that discussed with respect
to the descriptions of the previous embodiments described
above.
In another mode of operation of the particular embodiment shown in
FIG. 9, cathodes 57 are interconnected in rows and the grid
structures 58 are arranged in columns substantially similar to
grids 39 of FIG. 6. In such arrangement, fast switching of the
heater rows is not required. In the quiescent condition the cathode
rows are held at a positive voltage potential relative to the grid
structure 58 thereby preventing electron flow through the aperture
61. The rows of cathodes are sequentially switched in synchronism
with the transmitted picture information to a threshold voltage
potential for electron flow through aperture 61 of grid structure
58. Modulation potentials are sequentially applied to the grid
columns in accordance with the luminance (and chrominance) content
of the picture.
FIGS. 10 and 11 show an alternative embodiment of the invention
utilizing a different form of cathode electron emitting structure.
In such figures a film 62 of aluminum oxide is deposited on
insulator 29. A plurality of conductors 63, typically made of
molybdenum, are deposited in a set of rows on aluminum oxide film
62. In a preferred embodiment the thickness of conductors 63 may be
in the order of 0.2 micrometers. Over the rows of conductors 63 a
further layer 64 of aluminum oxide, in a preferred embodiment being
approximately 1.0 micrometer thick, is further deposited. A set of
conductors 65 arranged in columns, such conductors being typically
made of molybdenum, are then deposited on layer 64. Conductors 65
in a preferred embodiment are typically on the order of 0.2
micrometers thick. At each cathode 68 an opening, or hole 67 which
in a preferred embodiment may be circular and have a diameter in
the order of 2.0 micrometers is etched into conductors 65 and film
64 so as to provide a suitable aperture in conductors 65 and to
remove a portion of the aluminum oxide film 64 in the region
immediately beneath such aperture. A cone 66 of molybdenum is
deposited on conductors 63 within the etched hole as shown. A
voltage potential in the range of 50 to 500 volts between conductor
65 and conductor 63, with conductor 65 being positive relative to
conductor 63, produces an electron flow from the field emission
point of cone 66. Electrons flow through opening 67 and are further
accelerated to the phosphor anode screen structure at the other end
of channels 23.
In operation, the horizontal conductors 63 are sequentially
switched synchronously with the transmitted picture information to
a threshold voltage potential for electron emission from the field
emission points of cones 66. Additional modulation voltage
potentials are sequentially applied to the conductors 65
synchronously and in accordance with the luminance (and
chrominance) content of the transmitted picture information.
In an alternative arrangement of the embodiment in FIG. 10, an
additional apertured electrode, similar to the apertured grid
electrodes shown in FIGS. 6 and 9, may be situated between field
emission cathodes 68 and the anode/phosphor screen structure in the
neighborhood of cathodes 68. Such apertured electrode may be held
at a positive voltage potential in the range from about 50 to about
500 volts, a primary purpose of such electrode being to isolate the
somewhat critical field emission cathodes from variations in the
anode potential and to prevent possible charge accumulation on the
adjacent insulator.
FIGS. 4-11 have described various embodiments of the cathode
structures and FIGS. 12 and 13 are now used to show a portion of
the switching circuitry utilized to operate such previously
described structures. The circuitry of FIG. 12 is depicted as used
with the cathode structure of FIG. 4, for example, and in FIG. 12
the vertical conductors 26 and horizontal conductors 27 of thin
film cathodes 30 are shown. For line sequencing each horizontal
conductor 27 is connected to one of a plurality of semiconductor
switches, such as 69a, 69b, 69c, and each trio of semiconductor
switches is connected to a single terminal point. For example,
switches 69a, and 69b and 69c are each connected to terminal point
70a and subsequent trios of switches are connected to terminals
70b, 70c, etc. The terminals 70a, 70b, 70c, etc. are sequentially
switched in synchronism with the transmitted picture information
through additional semiconductor switches (not shown) to a voltage
potential providing the threshold voltage for electron emission
from thin-film cathodes 30. In alternate frames, either all the
switches 69b or all the switches 69c are held open thereby
preventing emission from the connected cathodes 30 and providing
for the interlacing of alternate frames. In either state switches
69a remain closed in such interlacing process. Although switches
69a may be omitted they are preferably included to provide matched
impedance elements in the switching circuitry associated with each
of the conductors 27.
One conductor of each trio of adjacent vertical conductors 26 is
connected as shown to one of a trio of transistors 71a, 71b and 71c
which may be, for example, well-known metal oxide semiconductor
field effect transistors, although other switching or modulating
semiconductor devices may alternatively be used. All gates of
transistors 71a are connected together to a terminal 72a.
Similarly, all gates of transistors 71b are connected to terminal
72b and all gates of transistors 71c are connected to terminal 72c.
Chrominance signals are applied to the terminals 72a, 72b and 72c.
The emitters of transistors 71a, 71b and 71c are connected as shown
to the collectors of another set of transistors 73a, 73b, and 73c
arranged in sets of three as shown. The emitters of all transistors
73 are connected together via terminal 74 to a common voltage
potential which is positive relative to that which is switchably
applied to terminals 70a, 70b, 70c, etc. The gates of transistors
73a, 73band 73c are connected together in triplets as shown to
terminals 75a, 75b and 75c. Normally, transistors 73 are
nonconducting. A signal proportional to the luminance content of
the transmitted picture is sequentially applied in synchronism with
the transmitted picture information to terminals 75a, 75b, 75c,
etc., causing each of the sets of transistors 73a, 73b, 73c, etc.
to conduct in turn. This current flow is divided through
transistors 72a, 72b, and 72c, etc. in accordance with the
chrominance signal applied to the gates of those transistors.
The arrangement of FIG. 12, though somewhat complex with respect to
the switching circuitry, is utilized to minimize the total number
of cathode structures required in the array of emitting structures
utilized in the invention while at the same time retaining the full
transmitted picture definition. As presently envisioned with
respect to the known state of the art relative to the elements
utilized in the invention, such arrangement appears to give the
greatest overall economy.
A simpler arrangement of switching circuitry is shown in FIG. 13,
such arrangement requiring somewhat more cathode structures than
that shown in FIG. 12. In the modulation sequencing switching
arrangement of FIG. 13 each triplet of transistors 73a, 73b and 73c
of FIG. 12 is replaced by a single transistor 76a, 76b, 76c, etc.
the collectors of which are connected as shown to transistors 71a,
71b and 71c. The emitters of transistors 76 are connected together
and to terminal 74 while the gates of transistors 76a, 76b, 76c,
etc. are connected to the modulating terminals 75a, 75b, 75c, etc.
Closer inspection of FIGS. 12 and 13 shows that approximately 50
percent more vertical conductors 26 are required for the switching
circuitry of FIG. 13 than for that shown in FIG. 12.
In FIG. 13 an alternative arrangement for the line sequencing is
also shown with respect to the horizontal conductors 27. Each
conductor 27 is connected to a separate switching transistor 79 and
through it only to one of the terminals 70a, 70b, 70c, etc. The
operation of switching transistors 79 for providing the interlacing
of alternate frames is substantially the same as that described
with reference to switching transistors 69 in FIG. 12. The degree
of overlap between adjacent lines of succeeding frames is thereby
reduced at the expense of an additional 50 percent more conductors
27. Therefore, for FIG. 13 approximately 125 percent more cathode
structures 30 are required than for FIG. 12. The line sequencing
arrangement of FIG. 12 may alternatively be used with the
modulation sequencing arrangement of FIG. 13 and vice versa.
Moreover, the alternative overall sequencing arrangements shown and
discussed above with reference to both figures may be used also
with each of the different cathode structures, such as are shown in
FIGS. 8, 9 and 10.
As discussed above, particular embodiments of the invention may
employ multidielectric, or other type, filters 36 discussed above
as being optionally useful and shown in the anode portions of the
display device of FIGS. 4, 6, 7, 8, 9 and 10. Such embodiments are
particularly adaptable to stereoscopic display presentation. The
principles of such stereoscopic displays are explained with
reference to FIGS. 14, 15 and 16 and, although described in
relation to the particular embodiments of the invention discussed
above, such principles are also adaptable to other forms of
television display devices, including conventional cathode-ray
tubes.
FIG. 14 is a representation of the visible spectrum indicating
visibility as a function of wavelength. In such figure, the visible
spectrum 80 is arbitrarily divided into six regions labeled
R.sub.R, R.sub.B, G.sub.R, G.sub.B, B.sub.R, and B.sub.B. Each
filter of the array of filters 36 is arranged either to transmit
one of these six regions of the spectrum or the complete red,
green, and blue portions, (R.sub.R + R.sub.B), (G.sub.R + G.sub.B),
and (B.sub.R + B.sub.B), respectively, of the spectrum in a manner
to be described in conjunction with FIG. 15, for example. FIG. 15
is a schematic representation of the display screen of a display
device of the invention, or other conventional cathode-ray tube,
with the transmission band of the filter associated with each area
element of the screen indicated by the appropriate reference
letters. In the figure, R indicates that the filter transmits the
complete red portion (R.sub.R + R.sub.B), G indicates transmission
of the complete green portion (G.sub.R + G.sub.B) and B indicates
transmission of the complete blue portion (B.sub.R + B.sub.B). With
reference to FIG. 12 it will be observed that in the line
sequencing switching arrangement the lines are scanned in pairs. In
FIG. 15 a line pair arbitrarily designated as lines L1 scans over
the filters R.sub.B, G.sub.B, and B.sub.B as well as the set of
filters immediately above them identified as R, B, and G. Line pair
L2 scans over the filters R.sub.R, G.sub.R, and B.sub.R and the
filters R, B, and G immediately above it. Similarly, alternate
frame line pair AL1 scans over filters R.sub.B, G.sub.B, and
B.sub.B and the filters R, B, and G immediately below it, while
alternate frame line pair AL2 scans over the filters R.sub.R,
G.sub.R, and B.sub.R and the filters R, B, and G immediately below
it. When line pairs denoted by odd numbers (i.e., L1, L3, etc. and
AL1, AL3, etc.) are taken from one camera and the line pairs
denoted by even numbers (i.e., L2, L4, etc. and AL2, AL4, etc.) are
taken from an adjacent camera focused on the same scene,
stereoscopic information is conveyed to the viewer in the display.
The stereoscopic scene is viewed through filters R.sub.B, G.sub.B,
and B.sub.B for the one eye and filters R.sub.R, G.sub.R, and
B.sub.R for the other eye. Preferably a neutral filter of
approximately 50 percent light attenuation is associated with each
of the filters R, G, and B on the display tube so that the light
flux transmitted through them is approximately equal to that
through the filters, R.sub.B, G.sub.B, B.sub.B, R.sub.R, G.sub.R,
and B.sub.R. Such an arrangement makes the stereoscopic light flux
dominant when the display is observed through the appropriate
filters and the light flux uniform when the display is directly
observed. Thus, this stereoscopic system is compatible with
existing monochrome and color transmission systems and
standards.
The arrangement of FIG. 15 in conjunction with the switching
circuitry shown in FIG. 12 minimizes the number of elements
required in the display tube. Alternative arrangements requiring
more picture tube elements may also be devised. One example thereof
is given in FIG. 16 wherein line pairs L1, L2, etc. and alternating
frame line pairs AL1, AL2, etc. scan only filters R.sub.R, G.sub.R,
B.sub.R for the odd numeral lines (i.e., L1, L3, etc. and AL1, AL3,
etc.) and only R.sub.B, G.sub.B, B.sub.B for the even numbered
lines (i.e., L2, L4, etc. and AL2, AL4, etc.) The circuitry of FIG.
13 may be used in conjunction with the display arrangement of FIG.
16. Other alternative arrangements may occur to those in the art
wherein, for example, the optical spectrum is divided into more
than six regions, such as an arrangement utilizing nine arbitrarily
divided regions, each color being divided into three regions, the
outer portions of which are scanned for presentation to one eye and
the central portion of which is scanned for presentation to the
other eye.
The invention, therefore, is not to be construed as limited to the
particular embodiments described herein except as defined by the
appended claims.
* * * * *