Flat CRT display apparatus

A flat CRT apparatus has a set of vertical scanning deflection electrodes arrayed down one flat inner face of the CRT, spaced apart from an opposing face having a photo-emissive layer formed thereon, and an electron gun for emitting a single flat electron beam or a row of narrow line electron beams into the space between the scanning electrodes and the photo-emissive layer. Vertical scanning of a raster display is executed by scanning voltages sucessively applied to the scanning electrodes, with the deflected electron beams thus obtained being then horizontally swept in common by a horizontal deflection electrode, so that each electron beam is utilized to display a large number of picture elements of each horizontal scanning line of the display picture.

BACKGROUND OF THE INVENTION 
The present invention relates to a cathode ray tube display apparatus 
having a flat configuration, for use in a television receiver, computer 
display terminal, etc. 
The cathode ray tube (hereinafter designated as CRT) type of display is 
widely utilized for displaying images, characters, etc. in various 
applications. Various proposals have been made in the prior art for making 
such a CRT display apparatus more compact than has been possible hitherto, 
by making the overall shape of the apparatus substantially thin and flat. 
One such proposal is made in U.S. Pat. No. 3,723,786. The general 
configuration of this proposed apparatus is as shown in FIG. 1A. A 
photo-emissive layer 2 is formed in an inner surface of a flat transparent 
front portion 1 of an evacuated envelope. A vertically extending array of 
horizontally elongated vertical scanning deflection electrodes 3 is formed 
on an inner face of a rear portion 4 of the evacuated envelope, which is 
disposed parallel to the front portion 1 with a narrow space left between 
the portions 1 and 4, the vertical scanning deflection electrodes 3 being 
arrayed with a fixed pitch in the vertical direction. An electron gun is 
formed by a line cathode 5, a first grid 6, a modulation electrode 7, and 
a shield electrode 8, with the modulation electrode 7 being positioned 
between the electrodes 6 and 8 as shown. The line cathode 5, grid 
electrodes 6 and 8 and modulation electrode 7 are shown separately in plan 
views in FIG. 1B. The line cathode 5 has electron-emitting segments 5a 
formed at regular spacings along its length, while the electrodes 6 to 7 
have respective rows of apertures 6a, 7a, 8a formed therein with a common 
pitch which is identical to that of the electron-emitting portions 5a of 
the line cathode 5. The electrodes 6 and 8 are electrically conductive, 
and are connected to respective fixed potentials, while the modulation 
electrode 7 is formed of an electrically non-conductive material and has 
an "eyelet" of conducting material formed around the periphery of each 
aperture 7a, with respective modulation signlas being applied to these 
eyelets. The picture element 2 is connected to a high voltage V.sub.D, so 
that a horizontally extending set of vertically directed electron beams 
are emitted through the apertures in the electrodes 6 to 8 and into the 
space between the picture element 2 and the vertical scanning deflection 
electrodes 3, as indicated by the upwardly extending broken line in FIG. 
1A. By applying the voltage V.sub.D to a lower set of the vertical 
scanning deflection electrodes 3 and a more negative voltage (V.sub.D 
-V.sub.C) to an upper set of the vertical scanning deflection electrodes 
as shown, all of the electron beams are deflected towards the picture 
element 2, when they reach the first vertical scanning deflection 
electrode which is connected to the (V.sub.D -V.sub.C) potential. Thus, 
raster scanning of such a display device can be performed applying 
sequential scanning voltages to the vertical scanning deflection 
electrodes 3 while modulating the respective intensities of the electron 
beams, so that an image such as a television picture can be displayed, if 
the number of the vertical scanning deflection electrodes is made 
substantially equal to the number of horizontal scanning lines of the 
display picture and the number of apertures of each of the electrodes 6 to 
8 is made substantially equal to the number of picture elements of the 
display picture. 
However such a display apparatus has some serious disadvantages. Firstly, 
since the number of electron beams that must be produced by the electron 
gun is equal to the number of picture elements in each horizontal scanning 
line of the display image, a very large number of electron beams must be 
produced which are positioned with very close mutual spacings. In the case 
of a usual CRT display television receiver, the pitch of the picture 
elements along the horizontal direction is approximately 0.1 to 0.2 mm. In 
order to generate a set of electron beams which are separated by such a 
small pitch, and to modulate these beams, it is necessary to execute very 
precise machining operations to form the components of the electron gun, 
while in addition practical problems will arise with forming electrical 
connections to the modulation electrode 7, for applying modulation signals 
for the respective electron beams. 
Furthermore, since a substantial distance is traversed by each electron 
beam from the point of leaving the electron gun (in which beam focusing 
and directing is implemented) to the point of incidence upon the picture 
element 2, it is difficult to avoid errors in the respective positions at 
which the beams fall upon the picture element 2. In addition, it is 
difficult to ensure that emitted-light spots of uniform diameter are 
produced by the electron beams over the entire display area. Variations in 
spot diameter will result in corresponding variations in display 
luminance, while in the case of a color television display, variations in 
spot size or errors in beam landing position will result in color errors 
in the displayed image. Thus, considerable problems would result if it 
were attempted to use such a prior art display apparatus to display 
characters or images with a normally acceptable level of display 
resolution. 
Another problem arises with such a prior art display apparatus, which is 
not significant when the display area is small. That is, in the case of a 
large display area, the length of the cathode of the electron gun will be 
of substantial length. In general, such a cathode is formed as a line 
cathode, which is supported under tension by springs at each end such as 
to be supported in a free-floating condition. Thus, such a cathode is very 
susceptible to the effects of vibration, which can result in instability 
of the level of electrons emitted from the cathode. This produces visible 
noise on the display, and also varies the electron beam landing positions, 
so that a reliably clear display cannot be ensured. 
SUMMARY OF THE INVENTION 
It is an objective of the present invention to provide a flat cathode ray 
tube display apparatus which overcomes the problems of the prior art set 
out hereinabove. More specifically, it is an objective of the present 
invention to provide a flat cathode ray tube display apparatus by the 
accuracy of control of electron beam trajectories is increased over the 
prior art, and whereby a uniform beam spot diameter can be produced over 
the entire display area of the apparatus. 
It is a further objective of the present invention to provide a flat 
cathode ray tube display apparatus having a single electron gun, whereby 
each of a plurality of commonly deflected electron beams is utilized to 
display a plurality of picture elements in a horizontal scanning line of a 
display picture. 
It is moreover an objective of the present invention to provide a flat 
cathode ray tube display apparatus having an electron gun including a line 
cathode, whereby vibration of the line cathode can be suppressed and 
display image stability thereby enhanced. 
To achieve the above objectives, a display apparatus according to one 
embodiment of the present invention includes means for generating and 
successively vertically deflecting a plurality of electron beams aligned 
as a horizontal row at intervals with a fixed pitch, and means for 
modulating the beams and for periodic horizontal deflection of the 
electron beams in common to sweep the beams across respective portions of 
a photo-emissive layer, such that each of the electron beams functions to 
display a plurality of picture elements of each horizontal scanning line 
of a display picture produced by the apparatus. Alternatively, a single 
electron beam is first produced in the shape of a thin sheet beam from an 
electron gun, and this beam is then successively vertically deflected, 
with the deflected beam being then converted to a plurality of thin line 
electron beams which are respectively modulated and periodically 
horizontally deflected to execute respective horizontal sweeps across a 
photo-emissive surface. 
More specifically, a first embodiment of a flat cathode ray tube display 
apparatus according to the present invention comprises: 
an evacuated envelope having flat mutually opposing first and second 
portions, with at least the first envelope portion being optically 
transparent and having a photo-emissive layer of a fluoroescent material 
formed over a rectangular region of an inner surface of the first envelope 
portion, the rectangular region having respective sides thereof extending 
in a horizontal and a vertical direction, and with a set of vertical 
scanning deflection electrodes formed as elongated conductive strips 
arrayed with a fixed pitch upon an inner surface of the second envelope 
portion; 
an electron gun disposed within the envelope, extending between the first 
and second envelope portions, for emitting an electron beam into a region 
between the vertical scanning deflection electrodes and photo-emissive 
layer and for forming the electron beam as a thin flat sheet aligned 
substantially parallel to the photo-emissive layer; 
means for applying scanning voltages to the vertical scanning deflection 
electrodes for producing deflection of the electron beam towards the 
photo-emissive layer by successive ones of the vertical scanning 
deflection electrodes; 
shield electrode means disposed between the vertical scanning deflection 
electrodes and photo-emissive layer, for converting the thin sheet 
electron beam to a corresponding plurality of thin line electron beams 
directed towards the photo-emissive layer, subsequent to deflection by the 
vertical scanning deflection electrodes; 
modulation electrode means for modulating respective ones of the plurality 
of electron beams; and, 
deflection electrode means for periodically deflecting the plurality of 
electron beams together, following modulation by the modulation electrode 
means. 
According to another embodiment, a flat cathode ray tube display apparatus 
according to the present invention comprises; 
an evacuated envelope having flat mutually opposing first and second 
portions, with at least the first envelope portion being optically 
transparent and having a photo-emissive layer of a fluoroescent material 
formed over a rectangular region of an inner surface of the first envelope 
portion, the rectangular region having respective sides thereof extending 
in a horizontal and a vertical direction, and with a set of vertical 
scanning deflection electrodes formed as elongated conductive strips 
successively arrayed with a fixed pitch upon an inner surface of the 
second envelope portion; 
an electron gun disposed within the envelope, extending between the first 
and second envelope portions for emitting a plurality of electron beams, 
each of thin linear shape, into a region between the vertical scanning 
deflection electrodes and photo-emissive layer the electron beams being 
each aligned in the vertical direction and successively arrayed along the 
horizontal direction with a fixed pitch; 
means for applying scanning voltages to the vertical scanning deflection 
electrodes for producing a common deflection of the electron beams towards 
the photo-emissive layer by successive ones of the vertical scanning 
deflection electrodes; 
modulation electrode means for modulating respective ones of the plurality 
of electron beams; and, 
deflection electrode means for periodically deflecting the plurality of 
electron beams together, following deflection by the vertical scanning 
deflection electrodes. 
In addition, an electron gun of a display apparatus according to the 
present invention preferably includes a line cathode which is held in 
contact with a surface of a supporting member, the surface having a convex 
curved contour which is an arc of a circle.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 2A shows an oblique partial view of the general configuration of a 
first embodiment of a flat CRT display apparatus according to the present 
invention. Numeral 9 denotes a flat transparent front portion of an 
evacuated envelope of the CRT, with the envelope being formed of glass in 
this embodiment. A photo-emissive layer 10 formed of a fluorescent 
material is formed over an inner face of the portion 9, this layer being 
shaped as a rectangle having sides aligned along a horizontal direction 
and a vertical direction, which respectively define horizontal and 
vertical directions of a raster-scan picture displayed by the apparatus. 
For high display brightness, a metallic back layer is preferably formed on 
the photo-emissive layer 10. In the case of a color display apparatus, the 
photo-emissive layer 10 is preferably formed as successive sets of red, 
green and blue-emission stripes which are vertically aligned with a fixed 
pitch. A set of vertical scanning deflection electrodes 11 are disposed 
immediately opposite the photo-emissive layer 10, spaced apart from the 
photo-emissive layer 10 by a fixed distance, and formed as a vertically 
extending array of horizontally extending elongated metallic strips upon 
an inner face of a flat rear portion 12 of the evacuated envelope of the 
CRT. It should be noted that in this specification and the appended 
claims, the designations "vertical" and "horizontal" respectively signify 
the aforementioned vertical and horizontal directions. Between the 
vertical scanning deflection electrodes 11 and the photo-emissive layer 10 
are successively disposed three vertically aligned electrodes, each of a 
substantially flat shape and positioned parallel to the photo-emissive 
layer 10, i.e. a shield electrode 13, a modulation electrode 14 and a 
horizontal deflection electrode 15. These are mutually separated and 
separated from the vertical scanning deflection electrodes 11 and the 
photo-emissive layer 10 by fixed spacings, and are shown in respective 
elevation views in FIG. 2B. 
An electron gun 23 which is of elongated form is positioned directly below 
the space formed between the vertical scanning deflection electrodes 11 
and photo-emissive layer 10, extending in the horizontal direction. The 
components of the electron gun 23, shown in respective plan view in FIG. 
2C, are a focus electrode 20 which functions to focus an electron beam 
produced from the electron gun 23 and for adjusting the position of the 
electron beam by movement of the beam in a direction perpendicular to the 
photo-emissive layer 10, a G2 electrode 19 for shaping and directing the 
electron beam outward through the focus electrode 20, an G1 electrode 18 
for controlling the electron beam, a line cathode 17 for generating 
electrons for the electron beam, and a back electrode 16. In FIG. 2C, the 
arrows indicate the direction of electron flow from the line cathode 17. 
As shown, the G1 electrode 18 and G2 electrode 19 have respective 
elongated apertures 18A, 19A formed therein, and these apertures in 
conjunction with the focus electrode 20 and respective fixed potentials 
applied to the electrodes 18 to 20 and the shield electrode 13 result in 
an electron beam having the form of a vertically extending thin sheet 
being projected from the focus electrode 20 into the space between the 
vertical scanning deflection electrodes 11 and the photo-emissive layer 
10, this thin sheet beam being oriented substantially parallel to the 
photo-emissive layer 10. The line cathode 17 is formed of a length of 
tungsten wire which is coated with a layer of an oxide material suitable 
for electrode emission (i.e. a "cathode oxide"), and is held fixedly 
attached in a state of tension, by means of supporting members including a 
spring. The back electrode 16 is positioned below and closely adjacent to 
the line cathode 17, and functions to direct electrons, emitted from the 
line cathode 17 by heating, towards the electrodes 18 to 10 and hence 
towards the vertical scanning deflection electrodes 11. The G1 electrode 
18 is positioned immediately above and closely adjacent to the line 
cathode 17. The focus electrode 20 is formed of two mutually parallel 
vertical plates which are elongated in the horizontal direction. In 
addition to performing focusing of the electron beam produced from the 
aperture of the G2 electrode 19, position adjustment of this electron beam 
in a direction perpendicular to the plane of photoemissive layer 10 is 
executed by varying a voltage difference applied between these two 
sections of the focus electrode 20. Although not shown in the drawings, 
the electrodes 16 and 18 to 20 are fixedly mounted by electrically 
insulating spacer members, which establish predetermined mutual spacings 
between these electrodes and between these electrodes and the line cathode 
17 and vertical scanning deflection electrodes 11. 
For simplicity of description, the configurations of the electrodes 11 to 
15 are shown in FIG. 2B for the case of only three electron beams being 
generated and with only three vertical scanning deflection electrodes 11 
being utilized. As shown, the shield electrode 13 has vertically elongated 
apertures formed therein for electron beam transfer which define 
respective narrow line beams that are emitted from these apertures (i.e. 
derived from the aforementioned "thin sheet" electron beam after 
deflection by the vertical scanning deflection electrodes 11). The 
modulation electrode 14 is formed of a plurality of sections which are 
mutually electrically isolated and coupled to receive respective 
modulation signals for the electron beams which pass through each of 
vertically elongated electron beam transfer apertures that are formed in 
the modulation electrode 14 as shown, these apertures being positioned in 
correspondence with those of the shield electrode 13. The resultant 
modulated electron beams then pass through respective elongated regions 
which are formed by the horizontal deflection electrode 15. As shown, the 
horizontal deflection electrode 15 consists of two comb-shaped sections 
15a and 15b, having vertically extending teeth which intermesh but which 
have a mutual offset in the horizontal direction, thereby forming the 
aforementioned vertically elongated regions, having respective central 
axes indicated by the chain lines. The central axes of the apertures of 
the shield electrode 13 and modulation electrode 14 are similarly 
indicated by chain lines, and it can be understood that these central axes 
are positioned to be mutually superimposed in the CRT, as viewed in a 
direction perpendicular to the screen. These central axes are positioned 
with a fixed pitch along the horizontal direction. Although not shown in 
the drawings, the electrodes 13 to 15 are fixedly mounted within the CRT 
by electrically insulating spacer members, which establish predetermined 
mutual spacings between these electrodes and between these electrodes and 
the vertical scanning deflection electrodes 11 and photoemissive layer 10. 
The vertical scanning deflection electrodes 11 can be formed on the inner 
face of the evacuated envelope portion 12 by a process such as hot etching 
or screen printing of a thin film of electrically conductive material such 
as aluminum, silver paste, etc. In general, the number of the vertical 
scanning deflection electrodes 11 is substantially identical to 1/n times 
the number of horizontal scanning lines of a display picture, where n is 
an integer. 
Typical values of operating voltages applied to the various electrodes 
described above are: -5 V for the back electrode 16, 0 V for the line 
cathode 17, 0 V for the G1 electrode 18, +100 V to +200 V for the G2 
electrode 19, 0 V for the focus electrode 20, 0 to 100 V for the vertical 
scanning deflection electrodes 11, +100 V for the shield electrode 13, -5 
to +30 V for the modulation electrode 14, +150 V (with 200 V peak-to-peak 
horizontal scanning voltage superimposed) for the horizontal deflection 
electrode 15, and +10 kV for the photo-emissive layer 10. 
The operation of this embodiment is as follows. Vertical scanning voltages 
are sequentially applied to the vertical scanning deflection electrodes 
11, as described in detail hereinafter, such that at any particular 
instant there will be a potential applied to at least one of the vertical 
scanning deflection electrodes 11 that is lower than the potential applied 
to the shield electrode 13, while a potential that is identical to that of 
the shield electrode 13 is applied to all of the vertical scanning 
deflection electrodes 11 that are positioned below the "low potential" one 
of the vertical scanning deflection electrodes 11. Thus, the thin sheet 
electron beam that is emitted from the focus electrode 20 proceeds 
vertically upward between the vertical scanning deflection electrodes 11 
and the shield electrode 13 until the aforementioned "low potential" one 
of the vertical scanning deflection electrodes 11 is reached, whereupon 
the beam is deflected towards the shield electrode 13. The electron beam 
then passes through the apertures in the shield electrode 13, thereby 
being formed into a horizontally extending row of thin line electron beams 
each of which is directed perpendicular to the photo-emissive layer 10. 
These electron beams then pass through respectively corresponding 
apertures in the modulation electrode 14, are modulated thereby, and the 
modulated electron beams then pass through corresponding ones of the 
aforementioned vertically elongated regions defined by the horizontal 
deflection electrode 15. 
A periodic horizontal scanning voltage, e.g. having a ramp or a staircase 
waveform and a period which is equal to one horizontal scanning interval, 
is applied between the two sections 15a, 15b of the horizontal deflection 
electrode 15. Each of the electron beams is thereby swept across a 
specific corresponding portion of a horizontal scanning line of the 
display picture during each horizontal scanning interval. The timings of 
the respective modulation signals applied to the modulation electrode 14 
are synchronized with the scanning voltage applied to the horizontal 
deflection electrode 15 such that, in each horizontal scanning interval of 
the display picture, modulation levels for respective picture elements are 
applied at correct timings during horizontal scanning of the electron 
beams. Circuits for implementing such synchronization of modulation and 
scanning signals, based upon digital signal processing of a video signal 
are already known in the art, and a detailed description of this will 
therefore be omitted. 
If the number of the vertical scanning deflection electrodes 11 is made 
substantially equal to the total number of horizontal scanning lines of 
the display picture, then scanning by the vertical scanning deflection 
electrodes 11 can be performed by applying the sequential drive voltages 
to the electrodes 11a to 11n shown in the waveform diagram of FIG. 5A. In 
FIG. 5A, 1 H indicates the duration of one horizontal scanning interval, 
while 1 V indicates on vertical scanning interval. As shown, the uppermost 
one of the vertical scanning deflection electrodes 11, i.e. electrode 11a, 
is fixedly connected to a potential E.sub.BO, which is lower than the 
potential E.sub.BP applied to the shield electrode 13. During the first 
horizontal scanning interval of a field, the voltage applied to the 
next-lowest electrode 11b is held at the E.sub.BP level, and is held at 
the E.sub.BO level for the remainder of the 1 V interval. During the first 
two horizontal scanning intervals of a field, the next electrode 11c is 
held at the E.sub.BP level, and at the E.sub.BO level for the remainder of 
the 1 V interval, and so on successively for the remaining vertical 
scanning deflection electrodes 11. In this example, the lowest of the 
vertical scanning deflection electrodes 11, i.e. e. 11n, is fixedly 
connected to the E.sub.BP potential, and does not execute scanning, but 
functions in conjunction with the shield electrode 13 to contribute to 
directing the electron beam emitted from the focus electrode 20 into the 
space between the vertical scanning deflection electrodes 11 and shield 
electrode 13. As a result of applying successive scanning voltages to the 
vertical scanning deflection electrodes 11 as described above, the 
electron beam 21 which is emitted from the focus electrode 20 is 
successively deflected into sequentially lower trajectories as illustrated 
by 21a, 21b, 21c in FIG. 3, remaining at each trajectory during one 
horizontal scanning interval. 
It is however possible to apply scanning voltages to the vertical scanning 
deflection electrodes 11 such that each of the vertical scanning 
deflection electrodes 11 is utilized for sequentially positioning the row 
of electron beams on the screen at each of a plurality of successive 
horizontal scanning lines. This will be illustrated for the case in which 
each of the vertical scanning deflection electrodes 11 controls 
positioning of two horizontal scanning lines of a field, referring to the 
waveform diagram of FIG. 5B. In this case the scanning voltage applied to 
the uppermost electrode 11a of the vertical scanning deflection electrodes 
11 is held at the E.sub.BO level during the first 1 H interval of a 1 V 
interval, and during this 1 H interval the uppermost horizontal scanning 
line of a of a field is displayed. During the succeeding 1 H interval, the 
electrode 11a is subjected to a potential E.sub.BQ which is slightly more 
negative than E.sub.BO, so that the trajectory of the electron beams is 
modified (e.g. from the trajectory 21a to the trajectory 21a' shown in 
FIG. 3) such that the landing positions of the row of electron beams on 
the photo-emissive layer 10 is slightly lowered. As a result, a horizontal 
scanning line is displayed, as the second line of the field, which is 
positioned immediately below the first-mentioned horizontal scanning line. 
The scanning voltage applied to the next-lowest electrode 11b is held at 
the E.sub.BP level during the first two horizontal scanning intervals of 
the 1 V interval, is set to the E.sub.BO level during the next 1 H 
interval, and to the E.sub.BQ level during the succeeding 1 H interval. In 
this way, the third and fourth lines of the field can be successively 
displayed during these two 1 H intervals. Similar sequences of scanning 
voltage are successively applied to the remaining vertical scanning 
deflection electrodes 11. 
It should be noted that although each of the scanning voltages applied to 
the vertical scanning deflection electrodes 11 is shown as returning to 
the E.sub.BO level when the next-lower one of the vertical scanning 
deflection electrodes 11 begins to be driven by the E.sub.BO potential, 
this is not essential. 
In the example of FIG. 5B, the scanning voltage waveforms applied to the 
vertical scanning deflection electrodes 11 are varied such that the number 
of the vertical scanning deflection electrodes 11 is equal to 1/2 the 
number of horizontal scanning lines of a field of the display picture. 
Thus, the number of of the vertical scanning deflection electrodes 11 can 
be halved, and their requisite width and pitch can be increased, thereby 
easing manufacture of such a CRT. In general, such modification of the 
trajectory of the electron beam 21 by sequentially varying the level of 
scanning voltage applied to each vertical scanning deflection electrodes 
11 could be utilized such that the number of the vertical scanning 
deflection electrodes 11 need only be 1/n times the total number of 
horizontal scanning lines of the display picture, where n is an integer. 
Generally, each frame of a television picture consists of two successive 
interlaced fields. A second example of scanning drive voltages for the 
vertical scanning deflection electrodes 11 of the first embodiment will 
now be described, whereby frame interlace operation can be implemented by 
utilizing each of the vertical scanning deflection electrodes 11 to for 
vertical deflection between two adjacent horizontal scanning lines, 
referring to FIG. 5C. In this case, during a first field interval (i.e. 
vertical scanning interval 1 V), the E.sub.BO potential described above is 
fixedly applied to the uppermost electrode 11a of the vertical scanning 
deflection electrodes 11, while during the succeeding field interval the 
lower potential E.sub.BQ is applied to electrode 11a. During the first 1 H 
interval of the first field, the E.sub.BP potential is applied to the 11b 
electrode of the vertical scanning deflection electrodes 11, and the 
E.sub.BO potential during the remainder of that field interval. During the 
first 1 H interval of the next field interval, the E.sub.BP potential is 
applied to electrode 11b, and the E.sub.BQ potential is applied thereto 
during the remainder of that field. Similarly, the E.sub.BP potential is 
applied to electrode 11c during the first two 1 H intervals of the first 
field, then the E.sub.BO potential, and so on. It can thus be understood 
that during the first interlace field of a frame each of the beam 
trajectories will be for example as indicated by 21a, 21b, 21c, . . . in 
FIG. 3, while during the second field of the frame these trajectories will 
be lowered, e.g. to the position 21a'. In this way, frame interlace 
operation of two fields per frame is achieved, although the number of the 
vertical scanning deflection electrodes 11 is substantially equal to the 
number of horizontal scanning lines in one field. 
It is also possible to change the trajectory of the electron beam 21 by 
applying a voltage difference between the the opposing sections of the 
focus electrode 20, to thereby move the electron beam 21 in a direction 
perpendicular to the photo-emissive layer 10. It will be apparent from 
FIG. 3 that such a position shift of the electron beam will result in a 
raising or lowering of the landing positions on the photo-emissive layer 
10 of the row of electron beams emitted from the horizontal deflection 
electrode 15. This is due to the fact that the electron beam 21 is not in 
fact deflected in a direction which is precisely perpendicular to the 
photo-emissive layer 10 by the action of the vertical scanning deflection 
electrodes 11, but instead attains an upwardly-sloping trajectory. It can 
thus be understood that beam position modification to execute interlace 
scanning or to utilize each of the vertical scanning deflection electrodes 
11 to position two successive display lines as described above, can also 
be performed by periodically varying a level of voltage difference applied 
between the two sections of the focus electrode 20. It has been found that 
similar results can be obtained by this method to those obtained with the 
scanning voltage modification method of FIG. 5B. 
FIG. 15 is a block diagram showing the general configuration of circuits 
for producing modulation signals and, vertical scanning voltages and 
horizontal deflection voltages for the first embodiment described above, 
for the case in which the embodiment is utilized to display a television 
picture based on a composite video signal. The composite video signal is 
applied to a sync separator circuit 30, which derives horizontal and 
vertical synchronizing signals S.sub.V and S.sub.H. The composite video 
signal is also applied, together with the S.sub.V and S.sub.H signals, to 
a video signal processing circuit 31. The video signal processing circuit 
31 contains circuits for converting the composite video signal to digital 
signal form, and for thereby producing modulation signals to be supplied 
to the respective sections of the modulation electrode 14, to modulate 
respective electron beams. These modulation signals are synchronized by 
the S.sub.V and S.sub.H signals such that at the start of each horizontal 
scanning interval, a modulation signal level for the first picture element 
of the line portion to be scanned by the leftmost one of the electron 
beams is produced from the video signal processing circuit 31, in parallel 
with a modulation signal level for the first picture element of the second 
line portion, which is scanned by the next one of the electron beams, and 
so on, i.e., then a modulation signal level for the second picture element 
of the first line portion, the second picture element of the second line 
portion, and so on, are outputted in parallel from the video signal 
processing circuit 31. In this way, modulation signal data are produced 
from the video signal processing circuit 31 at appropriate timings during 
each vertical and horizontal scanning interval for each of the sections of 
the modulation electrode 14. Circuits for implementing the functions of 
the video signal processing circuit 31 are now well known in the art, and 
detailed description will therefore be omitted. The horizontal deflection 
voltage generating circuit 32 is also synchronized by the S.sub.V and 
S.sub.H signals from the sync separator circuit 30, to produce a 
horizontal deflection drive voltage to implement a horizontal sweep by 
each of the electron beams in common, for the duration of each horizontal 
scanning interval. 
Vertical scanning voltages, having respective waveforms as illustrated for 
example in FIGS. 5A, 5B or 5C, are generated by a vertical scanning 
voltage generating circuit 33, these scanning voltages being generated in 
synchronism with the modulation signals and the horizontal deflection 
drive voltages by means of the synchronizing signals S.sub.V and S.sub.H 
from the sync separator circuit 30. 
It should be noted that various modifications to the embodiment described 
above could be envisaged. For example, although the shield electrode 13, 
modulation electrode 14, and horizontal deflection electrode 15 of the 
embodiment have been described as each having a thin flat configuration, 
each substantially positioned in a single vertical plane, it would also be 
possible to form each of these electrodes as a plurality of flat elements 
which are successively positioned along a direction perpendicular to the 
photo-emissive layer 10. In addition, although it is assumed in the above 
that each of these electrodes is formed from flat metal plate, it has been 
found that these can equally be formed by depositing metallic film 
patterns upon glass plate members. Thus the vertically extending "teeth" 
of the two comb-shaped sections of the horizontal deflection electrode 15 
can be formed simply as an array of vertically elongated film portions 
formed on a glass plate, with these being appropriately interconnected by 
connecting lead portions, and with vertical elongated apertures being 
formed in the glass plate between these elongated metallic film portions, 
to allow passage of the electron beams. A more rigid and easily 
manufactured structure can thereby be achieved. In addition, the "teeth" 
portions of the comb-shaped sections of the horizontal deflection 
electrode 15 can have a triangular rather than an elongated rectangular 
shape. 
A second embodiment of a flat CRT display apparatus according to the 
present invention will now be described, referring first to FIGS. 7A, 7B 
and 8. FIG. 7A shows an oblique partial view of the apparatus. This is 
basically similar to the first embodiment of FIG. 2A described above, but 
differs in further including a vertical deflection electrode 22, which is 
disposed between the horizontal deflection electrode 15 and the 
photo-emissive layer 10 as shown. As illustrated in the plan view of FIG. 
7B, the vertical deflection electrode 22 is formed of two intermeshed 
comb-shaped sections, as for the horizontal deflection electrode 15, with 
these intermeshing sections defining a plurality of horizontally elongated 
regions within which an electric field is produced by deflection voltages 
applied between the two sections. The electron beams, after passing 
through the horizontal deflection electrode 15, pass through these 
elongated regions defined by the vertical deflection electrode 22, to 
execute vertical deflection. The central axes of these elongated regions 
are indicated by the horizontal chain lines in the plan view of the 
vertical deflection electrode 22, and it can be understood that in the 
absence of any scanning voltages applied to the horizontal deflection 
electrode 15 and the vertical deflection electrode 22, the electron beams 
will pass through a row of points which are defined by the intersections 
of the vertical axes of the elongated regions defined by the horizontal 
deflection electrode 15 with one the horizontal axes of one of the 
elongated regions defined by the vertical deflection electrode 22. 
The structure of the electron gun 23 of this embodiment is identical to 
that of the first embodiment described above, and further description will 
be omitted. 
Due to the capability for vertical deflection of the electron beams by the 
vertical deflection electrode 22, this second embodiment enables each of 
the vertical scanning deflection electrodes 11 to be utilized for vertical 
scanning of a plurality of horizontal scanning lines of the display 
picture, without requiring modification of the scanning voltage waveforms 
applied to the vertical scanning deflection electrodes 11 as described 
hereinabove referring to FIGS. 5B and 5C. This operation will be described 
referring to the cross-sectional view in elevation of FIG. 8, the waveform 
diagram of FIG. 9A which shows scanning voltages sequentially applied to 
the vertical scanning deflection electrodes 11, and the waveform diagram 
of FIG. 9B which shows a scanning voltage applied between the two sections 
of the vertical deflection electrode 22, for the case in which each of the 
vertical scanning deflection electrodes 11 corresponds to three horizontal 
scanning lines of the display. A potential E.sub.BO, which is 
substantially more negative than the potential E.sub.BP applied to the 
shield electrode 13, is continuously applied to the uppermost electrode 
11. The potential E.sub.BP is applied to the next-lower electrode 11b of 
the vertical scanning deflection electrodes 11 during the first horizontal 
scanning interval of each field interval 1 V, and the E.sub.BO potential 
is applied for the remainder of that 1 V interval. Similarly, the E.sub.BP 
potential is applied for successively longer durations at the start of a f 
that 1 V interval. Similarly, the E.sub.BP potential is applied for 
successively longer durations at the start of a field interval, to the 
remaining successively lower-positioned ones of the vertical scanning 
deflection electrodes 11. Thus, referring to the cross-sectional view of 
FIG. 8, the electron beam 21 which emerges from the focus electrode 20 is 
deflected to the trajectory 21a for the duration of the first three 
horizontal scanning intervals of a field, due to the E.sub.BO potential 
which is applied to electrode 11a of the vertical scanning deflection 
electrodes 11. During the first of these horizontal scanning intervals, 
each of the electron beams thus emitted from the horizontal deflection 
electrode 15 is deflected to the trajectory 21aa by an electric field 
produced within the uppermost of the aforementioned elongated regions 
defined by the vertical deflection electrode 22, this electric field 
resulting from a potential +E.sub.SA which is applied between the two 
sections of the vertical deflection electrode 22. During the second 
horizontal scanning interval, the potential applied between the two 
sections of the vertical deflection electrode 22 is held at zero, so that 
the electron beams are not deflected by the vertical deflection electrode 
22, and so take the trajectory 21ab. During the third horizontal scanning 
interval of the field, the potential applied between the two sections of 
the vertical deflection electrode 22 is held at a value of -E.sub.SA. The 
electron beams are thereby deflected to the trajectory 21ac in FIG. 8. 
During the succeeding three horizontal scanning intervals, a similar 
deflection sequence is applied, with the electron beam produced from the 
focus electrode 20 having been first deflected to the trajectory 21b by 
the potential applied to the second electrode 11b of the vertical scanning 
deflection electrodes 11. 
In this way, the number of the vertical scanning deflection electrodes 11 
need only be 1/3 of the total number of horizontal scanning lines of the 
display picture. In general, this vertical deflection operation using the 
vertical deflection electrode 22 can be applied such that the number of 
the vertical scanning deflection electrodes 11 is 1/m times the total 
number of horizontal scanning lines of the display picture, where m is an 
integer. 
The above vertical deflection control by means of the vertical deflection 
electrode 22 can of course also be used to implement field interlace 
operation, in the case of an interlace display. This could be done, for 
example, by utilizing the deflection trajectories 21aa, 21ba, 21ca, etc 
during a first field of a frame, then utilizing the trajectories 21ab, 
21bb, 21cb, etc during the second field. In that case, the number of the 
vertical scanning deflection electrodes 11 would be 1/2 of the total 
number of horizontal scanning lines, and the E.sub.BP potential shown in 
FIG. 9B would be applied to the electrode 11b during two horizontal 
scanning intervals at the start of a field, to the electrode 11c during 
four horizontal scanning intervals at the start of the field, and so on. 
It can be understood from the above that in general the potential E.sub.BP 
shown in FIG. 8 is applied to electrode 11b for m horizontal scanning 
intervals in each field, to the electrode 11c for 2 m horizontal scanning 
intervals in each field, to the electrode 11d for 3 m horizontal scanning 
intervals, and so on, where m is the integer defined hereinabove. The 
levels of the deflection voltage sequentially applied to the vertical 
deflection electrode 22 must of course be determined in accordance with 
the number of different trajectories which are to be established by the 
vertical deflection electrode 22 (this number being 3, in the above 
example). 
In the embodiments described above, electron beam modulation is executed by 
a modulation electrode 14, which is of basically flat form, aligned 
parallel and close to the photo-emissive layer 10. However the invention 
is not limited to such a method of modulation, as will be described with 
reference to a third embodiment of a flat CRT display apparatus, shown in 
partial oblique view in FIG. 10A. With the first two embodiments described 
above, a single thin sheet electron beam is produced from the electron gun 
23, which is subsequently converted to a row of thin line electron beams 
by the electrodes 13, etc, after deflection by the action of the vertical 
scanning deflection electrodes 11, with this row of beams then being 
modulated. However with the third embodiment, a row of thin line electron 
beams is produced and also modulated by the electron gun, which includes 
an array of modulation electrodes. In this embodiment, a shield electrode 
13 and a horizontal deflection electrode 15 are disposed in the space 
between the vertical scanning deflection electrodes 11 and photo-emissive 
layer 10, together with a vertical deflection electrode 22, whose general 
configurations are illustrated in FIG. 10B. However it will be apparent 
that the embodiment could be modified by omitting the vertical deflection 
electrode 22, with vertical deflection control being executed as described 
for the first embodiment hereinabove. 
The components of the electron gun of this embodiment are separately shown 
in plan views in FIG. 10c. A modulation electrode 24 is formed of a set of 
electrode sections 24a, 24b, . . . consisting of respective electrically 
conductive layer portions which are formed upon a flat portion 25 of the 
outer envelope of the CRT, this envelope consisting of of an electrically 
insulating material such as glass, these electrode sections being spaced 
apart with a fixed pitch. The number of these layer portions of the 
modulation electrode 24 is identical to the number of electron beams 
emitted from the electron gun. The modulation electrode 24 is positioned 
below and closely adjacent to the line cathode 17, which is identical to 
that of the first two embodiments described above. A G1 electrode 18', a 
G2 electrode 19' and a focus electrode 20 are successively positioned 
above the line cathode 17, and perform similar functions to the electrodes 
18, 19 and 20 of the first two embodiments. However in addition, as shown 
in FIG. 10C, the G1 electrode 18' and the G2 electrode 19' are each 
provided with a line array of small apertures, rather than a single 
elongated aperture as in the first two embodiments. These small apertures 
extend horizontally, parallel to the photo-emissive layer 10, at regular 
intervals with a pitch which is identical to that of the sections 24a, 
24b, . . . of the modulation electrode 24. A set of thin line electron 
beams is thereby emitted from the focus electrode 20, this set extending 
along the horizontal direction of the display and with each of the beams 
being vertically oriented and each being modulated in intensity in 
accordance with a level of modulation voltage applied to a corresponding 
one of the electrode sections of the modulation electrode 24. The pitch of 
the apertures in the G1 electrode 18' and the G2 electrode 19' is 
identical to that of the elongated apertures formed in the shield 
electrode 13 and the elongated regions defined by the horizontal 
deflection electrode 15, so that as illustrated in the cross-sectional 
view in elevation of FIG. 11 and the partial cross-sectional view in plan 
of FIG. 12, after deflection by the vertical scanning deflection 
electrodes 11 in the same way as described hereinabove for the case of a 
single flat sheet electron beam, the electron beams emitted through the 
aforementioned apertures of the electron gun electrodes then pass through 
these apertures and regions of the shield electrode 13 and horizontal 
deflection electrode 15, and are horizontally and vertically deflected by 
electric field produced by the horizontal deflection electrode 15 and the 
vertical deflection electrode 22 in a similar manner to that described 
above for the second embodiment. 
It can thus be understood that in all respects other than the manner of 
generating and modulating the row of electron beams which are directed 
onto the photo-emissive layer 10, the operation of this third embodiment 
is essentially similar to that of the second embodiment described above. 
It should be noted that this embodiment is not limited to the form of 
modulation electrode described. For example, a modulation electrode could 
be disposed within the electron gun for modulating the electron beams 
after they have been emitted. This electrode could consists of a set of 
mutually electrically isolated sections each having an aperture to allow 
passage of a corresponding electron beam. Alternatively, an electrode 
which is used to form the beams, such as the G1 electrode 18' could be 
formed as a set of mutually electrically isolated sections with respective 
apertures, and used in common for both modulation and beam shaping. 
It should also be noted that the present invention is not limited to the 
use of a line cathode of the form utilized in the above embodiments. It is 
conceivable that one or more cathodes of the form utilized in a 
conventional CRT could be adapted as an electron source for a flat CRT 
display apparatus according to the present invention, for example. 
Furthermore, although in the second and third embodiments described above 
the vertical deflection electrode 22 is positioned between the horizontal 
deflection electrode 15 and the photo-emissive layer 10, it would be 
equally possible to position the electrode 22 between the horizontal 
deflection electrode 15 and the shield electrode 13. 
It would also be possible to position the electron gun along the upper part 
of the apparatus, rather than along the lower part as in the described 
embodiments. This would of course require appropriate modification of the 
scanning voltage waveforms applied to the vertical scanning deflection 
electrodes 11. 
From the above description it can be understood that with the first 
embodiment, control of the landing positions of the electron beams on the 
photo-emissive layer of the screen, in the horizontal direction, is 
controlled by a set of electrodes 13 to 15 positioned closely adjacent to 
that screen layer, and in particular by the horizontal deflection 
electrode 15. Thus, much more precise position control of the beams can be 
achieved than is possible with the prior art apparatus of FIG. 1, making 
it practicable to apply such a display apparatus to color television 
display. Furthermore with the second and third embodiments, control of the 
landing positions with respect to the vertical direction is performed by 
the vertical deflection electrode 22, which also is positioned closely 
adjacent to the photo-emissive layer of the screen. Since the distance 
which each electron beam travels after exiting from each of these 
deflection electrodes to the screen is extremely small, highly accurate 
position control can be achieved of the respective light spots which are 
formed by the beams, so that it becomes possible to utilize such a display 
apparatus to produce a picture of much higher resolution than has been 
possible hitherto, with uniform spot size over the entire display area and 
(in the case of a color display) with freedom from display color 
deviations which can result from errors in spot position or spot size. 
In the embodiments described above, the line cathode 17 is supported by 
retaining elements (not shown in the drawings) which include at least one 
spring for retaining the line cathode 17 in a state of tension. However 
with such a structure, the line cathode 17 is extremely susceptible to the 
effects of any mechanical vibration applied to the display apparatus. 
Resultant vibration of the line cathode 17 can result in various types of 
disturbance in the display picture, and color deviations in a color 
display, due to position deviations of the electron beams. FIG. 13 is a 
view in elevation of a supporting structure for the line cathode 17, which 
has the objective of substantially overcoming this problem of vibration of 
a line cathode. Numeral 26 denotes a supporting member, preferably formed 
of an electrically insulating ceramic material such as alumina, and has an 
upper surface having a contour in the shape of an arc of a circle. An 
attachment member 27 which is fixedly attached to the cathode supporting 
member 26 and to the line cathode 17, and a spring 28 which is also 
fixedly attached to the cathode supporting member 26 and line cathode 17, 
are positioned at opposite ends of the cathode supporting member 26, such 
as to retain the line cathode 17 in a state of tension, stretched over and 
in contact with the arc-contour surface of the cathode supporting member 
26. 
The arc-contour surface of the cathode supporting member 26 can be formed 
by grinding machining. Each of the attachment member 27 and spring 28 is 
preferably formed of metal, and these are respectively attached by screws 
or an adhesive agent such as low melting-point glass to the cathode 
supporting member 26. The line cathode 17 is formed of tungsten wire 
having a diameter of 10 to 13 micronmeters, which is coated along a part 
of its length with a layer 17a of an electron-emissive oxide material 
(generally referred to as a cathode oxide). 
It has been found that such a structure can substantially eliminate the 
problems of vibration of the line cathode 17 described above. 
Preferably, the layer of cathode oxide is formed only over an upper region 
of the line cathode 17, such that the part of the line cathode 17 which is 
held in contact with the surface of the cathode supporting member 26 is 
left uncoated by the cathode oxide. This has been found to effectively 
prevent the cathode oxide from flaking off from the line cathode 17. 
FIG. 14 shows a second embodiment of a supporting structure for the line 
cathode 17. Here, the line cathode 17 is supported on a cathode supporting 
member 26 as in the example of FIG. 13, with the the line cathode 17 being 
retained in contact with the surface of the cathode supporting member 26 
having a basically arc-contour shape. However in this embodiment, this 
arc-contour surface is further machined (e.g. by grinding using a grinding 
material formed of fine abrasive particles, preferably 500 mesh or less), 
such as to form small-amplitude convex and concave undulations on this 
arc-contour face. Grinding to form these undulations is preferably 
executed after the face has been machined to the contour of an arc of a 
circle, and finished to a high degree of polish. 
An alternative method of forming these undulations on the arc-contour 
surface is to execute selective hot etching of portions of that surface 
after it has been machined to a mirror finish. Alternatively, it is 
possible to simply form scratches in the machined surface of the 
arc-contour face, by mechanical machining (e.g. using a dicing tool). 
The line cathode 17 is supported in the same manner as the embodiment of 
FIG. 13, such as to be held in a state of tension, in contact with the 
arc-contour surface having these surface undulations formed therein. 
The embodiment of FIG. 14 has the advantage that the area of contact 
between the line cathode 17 and the cathode supporting member 26 can be 
reduced, by comparison with the embodiment of FIG. 13, so that heat loss 
from the line cathode 17 to the cathode supporting member 26 is reduced. 
The embodiments of FIGS. 13 and 14 have been described for the case in 
which the line cathode 17 is in direct contact with the cathode supporting 
member 26. However in order to prevent an accumulation of electric charge 
on the surface of the cathode supporting member 26, it is preferable to 
form a thin film of electrically conducting material (not shown in the 
drawings) over the surface of the cathode supporting member 26 which is 
contacted by the line cathode 17, i.e. so that the line cathode 17 comes 
into contact with this conductive surface film. Alternatively, such a film 
of electrically conductive material can be formed over a region of the 
arc-contour surface of the cathode supporting member 26 which is close to 
a surface region that is directly contacted by the cathode supporting 
member 26, without the conducting film being directly contacted by the 
line cathode 17. 
Although the embodiments of FIGS. 13 and 14 have been described for the 
case in which the cathode supporting member 26 is formed of an 
electrically insulating material, this is not essential. It is possible to 
form the cathode supporting member 26 from a metal, shaped as described 
above, and to then form a film of electrically insulating material (such 
as alumina) over a surface region of the cathode supporting member 26 that 
is contacted by the line cathode 17. This surface film can be formed by a 
method such as vacuum evaporative deposition, chemical vapor deposition, 
etc.