JPS5927436A - Picture display apparatus - Google Patents

Abstract

PURPOSE:To reduce change of focusing condition of flowing electrons due to vertical deflection even in case a flat type display element is used by changing a voltage to be applied to the electrodes of rear side during release of flowing electrons in accordance with vertical deflection of said electrons. CONSTITUTION:It is necessary to eliminate difference of angle of incident electrons to the slit 10 of vertical focusing electrode 3 and uniform the direction in order to eliminate aberration during vertical deflection of flowing electrons and obtain good focusing condition. Therefore, a potential of rear side electrode 1 is deeply biased in the negative direction. Thereby, the flowing electrons in the rear side released from the cathode 2a-2d can be squeezed and the flow of electrons having the uniform vector component to the front side can be input to the slit 10. When considering a picture display element from both application rate of flow of electrons and enhancement of brightness, electrons as many as possible should pass. For this purpose, such both conditions are satisfied by modulating a voltage applied to the electrode 1 in the rear side in accordance with deflection in the vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a flat image display device for displaying television images.

Conventional configurations and their problems Traditionally, cathode ray tubes have been mainly used as display elements for displaying color television images, but conventional cathode ray tubes are extremely long and thin compared to the screen size. It was impossible to create a shaped television receiver. In addition, although EL display elements, plasma display devices, liquid crystal display elements, etc. have recently been developed as flat display elements, all of them have drawbacks in terms of performance such as brightness, contrast, and color reproducibility. This is insufficient and has not yet been put into practical use.

Therefore, we aimed to achieve a device that can display color television images on a flat display device using electron beams, and we divided the second screen vertically into multiple sections. An electron beam is generated for each section, each electron beam is deflected vertically for each section to display a plurality of lines, and is further divided horizontally into a plurality of sections to display a plurality of lines for each section. The R, G, B, etc. phosphors are caused to emit light in sequence, and the amount of electron beam irradiation to the R, G, B, etc. phosphors is controlled by a color video signal.
A device was devised that displayed a television image as a whole. An example of a basic configuration of an image display element used here will be described with reference to FIG. 1.

This display element includes, in order from the back to the front, a back electrode 1, a line cathode 2 as a line thermionic electron source, a vertical focusing electrode 3,
3', a vertical deflection electrode 4, an electron beam flow control electrode 5, a horizontal focusing electrode 6, a horizontal deflection electrode 7, an electron beam acceleration electrode 8, and a screen plate 9 are arranged, and these are connected to a flat glass bulb ( (not shown) is housed in an evacuated interior.・The line cathode 2 as an electron source is stretched in the horizontal direction so as to generate an electron flow linearly distributed in the horizontal direction. In the figure, only four (2A to 2D are shown) are provided. In this embodiment, it is assumed that 16 pieces are provided. Let's say 2i~2yo. These wire cathodes 2 are constructed by applying an oxide cathode material to the surface of a tungsten wire of 1Q=20 μΦ, for example. Then, as will be described later, the electron beams are controlled to be emitted sequentially from the upper line cathode 2a for a fixed period of time. Back N
The pole 1 creates a potential gradient with a vertical focusing electrode 3, which will be described later, and suppresses the generation of electron flow from other wire cathodes 2 other than the wire cathode 2, which is controlled to emit an electron flow for a certain period of time. It also functions to push out the generated electron flow only in the forward direction. This back electrode 1 may be formed by a coating of electrically conductive material applied to the inner surface of the rear wall of the glass bulb. However, instead of the back electrode 1 and the linear cathode 2, a planar electron current emitting cathode may be used.

The vertical focusing electrode 3 is a conductive plate 11 having a horizontally long slit 10 facing each of the line cathodes 2i to 2yo, and directs the electron flow emitted from the line cathode 2 through the slit 1o.
Take out the paper through the paper and focus the 5 pages vertically. The slits 10 may be provided with crosspieces at appropriate intervals in the middle, or may be substantially a row of through holes arranged horizontally at small intervals (nearly touching intervals). It may also be configured as a slit. The vertical focusing electrode 3' is also similar.

A plurality of vertical deflection electrodes 4 are arranged horizontally at intermediate positions of the slits 1o, and conductors 13 and 13' are provided on the two surfaces and the bottom surface of the insulating substrate 12, respectively.
It consists of a set of A vertical deflection voltage is then applied between the opposing conductors 13+13' to deflect the electron flow in the vertical direction. In this configuration example, the pair of conductors 13° and 13' deflect the electron flow from one line cathode 2 to positions corresponding to 16 lines in the vertical direction. Then, 15 line cathodes 2 are formed by 16 vertical deflection electrodes 4.
15 pairs of conductor rows corresponding to each one are constructed, and ultimately deflect the electron flow so as to draw 240 horizontal lines on the screen 9.

Next, the control electrodes 6 are constituted by conductive plates 16 each having six vertically long slits 14, and a plurality of control electrodes 16 are arranged in parallel in the horizontal direction at predetermined intervals. In this configuration example, 320 control electrode conductive plates 1511 to 16
n (only 10 are shown in the figure).

Each of the control electrodes 5 extracts the electron current by dividing it into one picture element in the horizontal direction, and controls the amount of the electron flow passing therethrough in accordance with the video signal for displaying each picture element. Therefore, if 32020 control electrodes 6 are provided, 320 picture elements can be displayed per horizontal line. In addition, in order to display images in color, each picture element is R, G, B.
Display is performed using phosphors of three colors, and the R, e, and B video signals are sequentially applied to each control electrode 6. In addition, 320 sets of video signals for one line are simultaneously applied to the 320 control electrodes 6, and the video for one line is displayed at one time. .

The horizontal focusing electrode 6 has a plurality of vertically long slits 16 (320 slits) facing the slits 1-14 of the control electrode 6.
The electron flow for each picture element divided in the horizontal direction is focused in the horizontal direction for each of the seven pages to form a narrow electron flow.

The horizontal deflection electrode 7 is the same as above! A plurality of conductive plates 1 are arranged vertically in the middle of each of I-16.
8, a horizontal deflection voltage is applied between each of them to deflect the electron flow of each picture element in the horizontal direction, and to light each of the R, G, and H phosphors on the screen 9. Sequential irradiation 17 is performed to emit light. The deflection range is
In this embodiment, each electron stream is one pixel wide.

The acceleration electrode 8 is composed of a plurality of conductive plates 19 provided horizontally at the same position as the vertical deflection electrode 4.
The electron stream is accelerated to impact the screen 9 with sufficient energy.

The NuClean 9 is constructed by coating the back surface of a glass plate 21 with a phosphor 2o that emits light when irradiated with an electron flow, and a metal bank layer (not shown) is added thereto. A pair of phosphors 20 of three colors R, G, and B is provided for each beam 14 of the control electrode 5, that is, for each horizontally divided electron flow. It is applied in stripes in the vertical direction. 1st
In the figure, the broken lines drawn on the screen 9 are multiple line cathodes 2.
The two-dot chain line indicates a horizontal division displayed corresponding to each of the plurality of control electrodes 6. As shown in the enlarged view in Fig. 2, one section partitioned by these two has R, G, and B phosphors 20 for one pixel in the horizontal direction, and 16 lines in the vertical direction. It has a width of The size of one section is, for example, one word in the horizontal direction and 16 words in the vertical direction.

Note that in FIG. 1, the horizontal lengths are lined up in the vertical direction and are drawn extremely enlarged for clarity.

In addition, in this embodiment, only one pair of R, G, and B phosphors 2° for one picture element is provided for one control electrode 5, that is, for one electron flow. Of course, even if two or more pairs of parts are provided, in that case, the control room f
R, G, and B video signals for two or more picture elements are sequentially applied to M5, and horizontal deflection is performed in synchronization with this for nine pages.

Next, the basic configuration of a drive circuit for displaying television images on this display element will be explained with reference to FIG. First, a driving portion for irradiating the screen 9 with an electron stream to cause the phosphor to emit light and generate a raster will be described.

The power supply circuit 22 is a circuit for applying a predetermined bias voltage (operating voltage) to each electrode of the display element, -v1 to the back electrode 1, Vs, V3', V3' to the vertical focusing electrodes 3 and 3'.
A DC voltage of V6 is applied to the horizontal focusing electrode 6, V8 is applied to the accelerating electrode 8, and DC voltage V9 is applied to the NuClean 9.

Next, a composite video signal of a television signal is applied to the input terminal 23, and a synchronization separation circuit 24 separates and extracts a vertical synchronization signal V and a horizontal synchronization signal H.

The vertical drive pulse generation circuit 25 is composed of a counter that is reset by a vertical retrace pulse and counts horizontal pulses, and the effective vertical scanning period (here, 240H) excluding the vertical retrace period of the vertical period. 16 drive pulses (42 pulses, etc.) having a length of 10 pages are generated sequentially during each 16H period. This drive pulse [42 pulses...Y] is applied to the line cathode drive circuit 26, where it is inverted so that it is at a low potential only during each pulse period, and at a high potential of approximately 20 volts during the other periods. Line cathode driven parnu [4
72 ports'...Yo'], each wire cathode 2i, 20. ...Added to 2yo. Each line cathode 2a,
・・・・・・2Yo is that current is flowing during the high potential period of the driving pulse [A' to YO'], and electrons are emitted even during the low potential period of the driving pulse [A' to YO']. The heated state is maintained as long as possible. As a result, electrons are emitted from the 15 line cathodes 2i to 2yo only during the 16H period when low potential drive pulses [a' to yo'] are applied to each of them. During the period when a high potential is applied, the potential at the position of the line cathode 2 determined by the bias voltage applied to the back electrode 1 and the vertical focusing electrode 3 is also added to the line cathodes 2I to 2Y. Electrons are not emitted from the line cathodes 2I to 2Y unless the high potential applied to them becomes positive.

Thus, at the line cathode 2, the effective vertical scanning period 11
Between pages, electrons are sequentially emitted from the upper linear cathode 2a to the lower linear cathode 2yo for 16H periods. The emitted electrons are pushed forward by the back electrode 1, pass through the opposing slits 10 of the vertical focusing electrode 3, and are focused in the vertical direction to form a −C1 flat electron flow.

Next, the vertical deflection drive circuit 27 is composed of a counter that is reset by each of the vertical drive pulses [I to Y] and counts the horizontal synchronization signal, a conversion circuit that converts the count output from D/A, and the like. During the 16H period of each vertical drive pulse [I to Y], a pair of vertical deflection signals v and v' are generated that change in 16 steps by 1H. The vertical deflection signals V and V' both have a center voltage of v4, and are configured to change in opposite directions such that V increases sequentially and V' decreases sequentially. These vertical deflection signals V and V' are applied to the electrode 13 of the vertical deflection electrode 4, respectively.
and 13', and as a result, the electron streams generated from each of the line cathodes 2i to 2yo are vertically deflected in 16 steps, and as mentioned earlier, one electron stream is applied to the screen 9. The raster is deflected so that 16 lines of raster are drawn one line at a time, starting from 1-.

As a result of the above, electron streams are emitted sequentially from the two 150-line cathodes 2A to 2Y for 16H periods, and each electron stream is sequentially distributed for one line from top to bottom within 15 sections in the vertical direction. As a result, on the screen 9''2, the electron flow is vertically deflected one line at a time from the 1st line at the top to the 240th line at the bottom, resulting in a total of 240 lines.
A raster of lines is drawn.

The electron stream thus vertically deflected is horizontally divided into 320 sections by the control electrode 6 and the horizontal focusing electrode 6 and extracted. Figure 1 shows one of these categories. The amount of electron flow passing through each section is controlled by the control electrode 6, and horizontally focused by the horizontal focusing electrode 6 into a single thin electron stream, which is then horizontally moved in three stages by the horizontal deflection means described below. The light is deflected to the R, G, and H phosphors 20 on the screen 9 in sequence.
Shoot 3 pages.

That is, the horizontal drive pulse generation circuit 28 is composed of three cascaded monostable multivibrators, etc.
Triggered by a horizontal synchronization signal, three horizontal drive pulses r, g, with equal pulse widths are generated within one horizontal period.
generate b. Here, by way of example, three pulses r, g, b are generated during an effective horizontal scanning period of 60 microns, each with a pulse width of about 17 microns. Those horizontal drive pulses r, g,
b is applied to the horizontal deflection drive circuit 29. This horizontal deflection drive circuit 29 is switched by horizontal drive pulses r, g, and b to generate a pair of horizontal deflection signals ri and h' that change in three stages. Horizontal deflection signal, h
’ both have a center voltage of v7, h increases sequentially, and h
' change in opposite directions so that they decrease sequentially. These horizontal deflection signals h' are applied to electrodes 18 and 18' of horizontal deflection electrode 7, respectively. As a result, each electron stream divided in the horizontal direction is horizontally deflected so as to sequentially irradiate the R, G, and B lights of the screen 9 by 17 μm during the horizontal period. However, in the display element of FIG. 1, in the horizontal deflection electrode 7, one conductor 18 or 18' is used for deflecting the electron streams of two adjacent sections. Since the electron currents in the 320 sections are deflected in opposite directions, if the electrons in the odd-numbered sections are deflected in the order of hill -+G-+H, then the electron flows in the even-numbered sections are Conversely, it is deflected in the opposite direction every other section, such as in the order of B-+G-+H.

Thus, in each line raster, the horizontal 3
An electron stream is sequentially irradiated onto each of the R, G, and H phosphors 20 for each of the 20 sections.

Therefore, for each horizontal section of each line, the electron flow is divided into R, G,
By modulating the H video signal, the entire color television image can be displayed on the screen 9.

Next, we will explain the modulation control part of the electron flow.

Page 15 First, the composite video signal applied to the television signal input terminal 23 is not applied to the color demodulation circuit 3o, where R-Y
and B-Y color difference signals are demodulated, the G-Y color difference signals are matrix-synthesized, and further, they are combined with the luminance signal Y to obtain the R, G, and B primary color signals (hereinafter referred to as R, (r
, B video signal) is output. Those R,
Each G and B video signal has 320 sets of sample hold times Ki.
A Added to 311L-31n. Each sample hold circuit group 311L to 31n has three sample hold circuits for R, G, and B, respectively. The sample and hold outputs of the sample and hold circuit set 31a and 31n are respectively applied to holding memory sets 321L to 32n.

On the other hand, the sampling reference clock oscillator 33 is a PLL.
(phase-locked loop) circuit, etc., and generates a reference clock of approximately 6.4 MIIz in this embodiment. The reference clock is controlled to always have a constant phase with respect to the horizontal synchronizing signal H. This reference clock is applied to the sampling pulse generation circuit 34, where it is delayed by one clock period by a shift register, etc. As a result, the horizontal period (63,5μ5ec)
3 during the effective horizontal scanning period (approximately 50μ5ec)
20 sampling pulses a-n are generated sequentially,
One transfer pulse is then generated. These sampling pulses a - n correspond to each picture element when one line of the video to be displayed is divided into 320 picture elements in the horizontal direction, and their positions are always constant with respect to the horizontal synchronizing signal H. controlled by.

These 320 sampling pulses a-n correspond to the 320 sample-and-hold circuit sets 31a to 31n, respectively.
is added to each sample-and-hold circuit set 3.
1&~32n, when one line is divided into 320 picture elements, each picture element R, (,, B) video signals are individually sampled and held. 320 sample-held sets R, G, B video signals are 1
After completing the sample hold for the line, all 320 sets of memories 3.2a to 32H are transferred 17 at once by a transfer pulse t.
The page is advanced and is now held for the next horizontal scanning period.

One line of R, G stored in the memories 32a to 32n
, B video signals are applied to 320 switching circuits 35a to 35n, respectively. switching circuit 35
1L to 35n are R and G, respectively.

Each switching circuit 35a has individual input terminals of B and a common output terminal that sequentially switches and outputs them.
The output of ~35n is used as a control signal for modulating the electron flow and is sent to the 320 conductive plates 15a~1 of the control electrode 5 of the display element.
5n separately. The switching circuits 35a to 35n are simultaneously controlled by switching pulses applied from the switching pulse generating circuit 36. The switching pulse generation circuit 36 is controlled by the pulse r+(J+b) from the horizontal driving pulse generation circuit 28 mentioned above, and divides the effective horizontal scanning period of each horizontal period of about 50μ into three, and divides the effective horizontal scanning period of about 17μ into three switching circuits 351L to 351L. 35n, the R, G, and B video signals are time-divided and outputted alternately in 18 pages, and the switching signals r, g, and b are generated to be supplied to the control ti15a to 15n.However, the switching circuit 35&~35n, the odd numbered switching circuits 36L, 350... are switched in the order of R-+G→B, and the even numbered switching circuits 35b
, 35d-=.35n are reversely switched in the order of B-+G-+H.

What should be noted here is that the switching circuits 35a to 3
The switching of the supply of R, G, and B video signals at 5n and the horizontal deflection of the horizontal deflection of the electron flow to the R, G, and B phosphors by the horizontal deflection drive circuit 29 are completely performed in both timing and order. They are synchronously controlled to match.

As a result, when the electron flow is irradiating the R phosphor, the irradiation amount of the electron flow is controlled by the R video signal,
G and B are similarly controlled, and R and B of each picture element are controlled in the same way.
The light emission of each G and B phosphor corresponds to the R, G, and B of that picture element.
Each picture element is controlled by a video signal and is displayed by emitting light according to the input video signal.

Such control is performed simultaneously for 320 picture elements on 19 pages for 1 line to display 1 line of video, and then sequentially for 240 minutes of video, starting from the two lines, to display one image on screen 9. The image will be displayed.

The following operations are repeated for each field of the input television signal, and as a result, a moving television image is displayed on the screen 9 as in a normal television receiver.

As described above, television images are displayed on this display device.

Note that the terms horizontal direction and vertical direction in the above explanation refer to the direction in which line units are displayed when displaying an image is the horizontal direction, and the direction in which the lines are stacked is the vertical direction. It is used in the sense that it is not directly related to the vertical direction and horizontal direction on an actual screen.3 However, in the above-mentioned image display device, the electron flow changes depending on the vertical deflection of the electron flow. It was found that the focusing state of the electron flow changes.

For example, the electron stream emitted from the line cathode 20 in FIG. 1 is vertically deflected by the vertical focusing electrode 4 to form 16 rasters in one vertical section of the 7-clean 9 as shown in FIG. do. At this time, as shown in FIG. 4, the vertical focusing state of the beam spot deteriorates near the dividing line.

The reason for this will be explained using FIG. 6.

Arrow X indicates the emission state of electron flow. In FIG. 4a, a deflection voltage is applied to the vertical deflection electrode 4 so that the electron flow proceeds straight forward without being deflected, but the vertical focusing electrode 3
The incident angle of the electron flow entering the slit 10 is different in the part, middle, and bottom of the slit 10, as shown by vectors 1-)vB+, B2, and B3 at the right end. Then, the electron flow
progresses. On the other hand, in FIG. 4, a deflection voltage for vertically deflecting downward is applied to the vertical deflection electrode 4, and a vector having an incident angle to the slit 1o of the vertical focusing electrode 3, as in the case of a, is applied to the vertical deflection electrode 4. Each electron flow X advances in the direction of B+, B2, B3 and deflection vector l-Pagetor sum C+, C2, C3.

In case a, as the electron flow progresses, B1. The incident angle of B3 loses its influence as AO remains constant, but
In case b, as the electron beam advances, the vector directions of the upper, middle, and lower electron streams differ at each deflection position, and the speed at which the electron beam approaches the electrode also differs. Therefore, in this case, the upper and lower electron flows are directed to the vertical deflection electrode 4.
As shown in FIG. 4, the electron flow spreads outward in a belt shape near the edges of vertical sections such as B1 and Ba6, causing aberrations at the exits of the electron beams.

OBJECTS OF THE INVENTION The present invention eliminates such conventional drawbacks, and even when using a planar image display element as described above, changes in the focusing state due to vertical deflection of the electron flow can be reduced, and the overall improvement is achieved. It is an object of the present invention to provide a device that can achieve a good focusing state.

, Structure of the Invention, Page 22 In the present invention, in the planar image display element having the above-mentioned structure, the voltage applied to the back electrode is changed during the emission period of the electron flow in accordance with the vertical deflection of the electron flow. By doing so, when deflecting near the edge of the vertical section, each part of the electron flow at the slit is The angular difference between the two electron beams is reduced, thereby reducing the aberration of the electron flow and improving the focusing state.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 6 and 7.

As mentioned above, in order to improve the focusing state by eliminating aberrations when the electron stream is vertically deflected, it is necessary to eliminate the angular difference in the electron stream X entering the slit 10 of the vertical focusing electrode 3 and align the directions. There is.

For this purpose, the electron flow that is emitted from the line cathodes 2I to 2Y in the rear direction and then changed direction in the front direction to reduce the flow of electrons that enter the slit 10 is reduced.

Page 23 In order to achieve this, the potential of the back electrode 1 should be brought deeply to the negative side.
It is possible to particularly focus and confine the back side of the electron flow emitted from Y, and the electron flow
0 can be input. However, in order to improve the utilization rate and brightness of the electron flow as an image display element, it is necessary to allow as much electron flow as possible to pass through the slit 10. Therefore, this device satisfies both conditions by modulating the voltage applied to the back electrode 1 according to the deflection in the vertical direction.

To explain this using FIG. 6, a is the emission period of the electron stream from any of the line cathodes 2a to 2yo, and b is the vertical deflection applied to the vertical deflection electrode 4 for vertical deflection of the electron stream. The voltage waveform, C is the conventional waveform of the voltage applied to the back electrode 1, d is the waveform of the voltage applied to the back electrode 1 by the dynamic focus circuit that is a feature of this device, and e is the waveform of each deflection position (line). This is the waveform of the pulse. Figure 6d
At the deflection points (B1.B16) at both ends of the vertical section, the voltage d1. applied to the back electrode 1 is applied. By setting d16 in a deeply negative direction, the electron flow emitted from the line cathodes 2i to 2yo in the back direction is suppressed, and the sulin 1-10 of the electrode 3 is
The spread of the incident angle of the electron flow incident on the screen 9 can be reduced, and the electron flow B for each raster display on the screen 9 can be reduced.
1 to B16 can have uniform spot diameters.

FIG. 7 shows a circuit for creating a voltage to be applied to the back electrode having a waveform as shown in FIG. 6d. The voltage d for applying the back and surface electrodes in FIG. 6 is determined by the voltage setting variable resistor group 37 in FIG.
each level) vd1 to d16 are set. On the other hand, from the counter 38 which is reset by the vertical drive pulses [I to Y] and counts the horizontal pulses H, 16 switching pulses with different phases are sequentially input in synchronization with each deflection point such as 61 to θ16 in Fig. 6. do. These switching pulses 81 to θ16 are inverted by the input group 39 and then applied to the analog switch group 40, and the voltage set by each variable resistor is taken out sequentially through the analog switch group 40, and the operational 25
The page amplifier 41 amplifies the voltage to obtain a voltage having a modulated waveform as shown in FIG. 6d. By superimposing the voltage d thus formed on the fixed voltage v1 of the back electrode 1 and applying it to the back electrode 1, a circuit having the above-mentioned die nanofocus effect is realized.

Effects of the Invention As described above, according to the present invention, when a planar image display element is used, it is possible to prevent the deterioration of the focused state of the island electron flow due to vertical deflection, and to maintain the focused state over the entire screen. A good left image can be displayed.

[Brief explanation of the drawing]

Figure 1 is an exploded perspective view showing the basic configuration of a planar image display element, Figure 2 is an enlarged front view of its screen, Figure 3 is a block diagram showing the basic configuration of its drive circuit, and Figure 4 is its Enlarged front view showing the focused state on the screen, No. 6
The figure shows a cross-sectional view and a vector diagram to explain the focusing operation of the electron flow, FIG. 6 is a waveform diagram to explain the operation of the image display device in an embodiment of the present invention, and FIG. 7 shows the main points. FIG. 2... Line cathode, 3, 3... Vertical focusing electrode, 4... Vertical deflection electrode, 5... Electron flow control electrode, 6... ...Horizontal focusing electrode, completed...
...Horizontal deflection electrode, 8...Electron flow acceleration electrode,
9... Screen, 10... Slit, 20... Fluorescent material, 37... Variable resistor group, 38... Counter, 39...Inverter group, 4゜...Analog switch group, 4
1...Operational amplifier. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 6
Figure BIBx Ha B4-----------------------1--B
6B+6(C) 17;□ 1.1.4---------ts
dtl figure 7

Claims (1)

[Claims] A plurality of linear thermionic sources, a back electrode provided on the back side of the thermionic sources so as to regulate the electron flow toward the front side; an electrode provided to extract and focus the electron flow in a vertical direction; an electrode provided to deflect the electron flow in the vertical direction; an electrode provided to focus the electron flow in the horizontal direction; an electrode provided to perform brightness modulation by controlling the amount of the electron flow; an electrode provided to deflect the electron flow in the horizontal direction; an electrode provided to accelerate the electron flow; By forming a phosphor surface in a vacuum container so as to generate light, and modulating the voltage applied to the back electrode in accordance with the vertical deflection during the electron current emission period of the linear thermionic electron source. An image display device characterized by being provided with a dynamic focus circuit that controls a vertical focusing state of an electron flow. 2 beige