JPS61183856A - Image display device - Google Patents

Abstract

PURPOSE:To achieve improved image quality by making an electron beam to be constantly irradiated upon a normal position in a normally focused state by detecting the amount of light emitted by vertical stripes of phosphors applied to the screen. CONSTITUTION:An image display device is constituted by placing a back electrode 1, a linear cathode 2, vertically focusing and deflecting electrodes 3, 3' and 4, a beam-current-controlling electrode 5, horizontally focusing and deflecting electrodes 6 and 7, an accelerating electrode 8 and a screen 9 in that order. A set of vertical phosphor stripes 50 are applied to the area of the screen 9 outside the effective picture screen and the amount of light emitted by the phosphor stripes 50 is detected by light-receiving elements 51-53. Signals for the horizontal landing position and the focused state during operation are compared with signals stored in a memory circuit and the results of the comparison are fed back to a driving circuit. Consequently, it is possible to constantly maintain the horizontal landing position and the focused state of the electron beam at normal levels.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention generates an electron beam for each division when a screen on a screen is vertically divided into a plurality of divisions, and generates an electron beam for each division. The present invention relates to an apparatus for displaying a plurality of lines by vertically deflecting a beam and for displaying a television image as a whole.

Conventional technology Conventionally, cathode ray tubes have been mainly used as display elements for displaying color television images, but conventional cathode ray tubes have a very long depth compared to the screen size, making it difficult to receive thin television images. It was impossible to set up a machine. Further, although ELi display devices, plasma display devices, liquid crystal display devices, and the like have recently been developed as flat display devices, all of them are insufficient in terms of performance such as brightness, contrast, and color display.

Therefore, in order to achieve a flat display device using electron beams, the present applicant filed Japanese Patent Application No. 66-20618 (
A novel display device was proposed in Japanese Patent Application Laid-Open No. 57-135590.

This method generates an electron beam for each section when the screen is vertically divided into multiple sections, and displays multiple lines by deflecting each electron beam vertically for each section. However, it displays a television image as a whole.

First, a basic configuration example of the image display element used here will be explained with reference to FIG.

This display element includes, in order from the back to the front, a back electrode 1, a line cathode 2 as a beam source, and vertical focusing electrodes 3, 3'.
, a vertical deflection electrode 4, a beam flow control electrode 5, a horizontal focusing electrode 6, a horizontal deflection electrode 7, a beam acceleration electrode 8 and a screen 9, which are placed in a vacuum on a flat glass pulp (not shown). Made inside.

If necessary, an auxiliary electrode 3' may be arranged between the vertical deflection electrode 4 and the beam current control electrode 6 as a second vertical focusing electrode or a front horizontal focusing electrode. The line cathode 2 as a beam source is stretched horizontally so as to generate an electron beam distributed linearly in the horizontal direction. In the figure, only four wires 2-2 are shown). In this embodiment, it is assumed that 16 pieces are provided. Those? -2i~2yo. These line cathodes 2 are, for example, 1
An oxide cathode material for thermionic emission is coated on the surface of a tungsten wire with a diameter of 0 to 20 μφ. and,
These line cathodes 2A to 2Y are heated so as to generate a thermionic electron beam by passing an electric current through them, and as described later, the line cathodes 2A and 2Y emit electron beams sequentially for a certain period of time. controlled to do so. The back electrode 1 is
It acts to suppress the generation of electron beams from other line cathodes 2 other than the line cathode 2 that is controlled to emit electron beams for a certain period of time, and to push out the generated electron beams only in the forward direction. . This back electrode 1 may be formed by a coating film of a conductive material adhered to the inner surface of the rear wall of the glass pulp. Further, instead of the back electrode 1 and the linear cathode 2, a planar electron beam emitting cathode may be used.

The vertical focusing electrode 3 is a conductive plate 11 having a horizontally long slit 10'i facing each of the cathodes 2a to 2y, and allows the electron beam emitted from the line cathode 2 to pass through its slit 10. Take out and focus vertically. Electron beams for one horizontal line (36 picture elements) are taken out at the same time.

In the figure, only one section in the horizontal direction is shown. The slit 10 may be provided with crosspieces at appropriate intervals in the middle, or it may be a row of through holes arranged horizontally at small intervals (ohm intervals to the extent that they almost touch each other). It may also be configured as a slit.

When the auxiliary electrode 3' is arranged as a second vertical focusing electrode, its shape is similar to that of the vertical focusing electrode 3' described above, and when it is arranged as a front horizontal focusing electrode, it has the same structure as the horizontal focusing electrode described later. The structure is similar to 6.

A plurality of vertical deflection electrodes 4 are arranged horizontally at intermediate positions of the slits 10, and conductors 13, 13' are provided on the upper and lower surfaces of the insulating substrate 12, respectively.
A vertical deflection voltage is applied between the opposing conductors 13 and 13' to deflect the electron beam in the vertical direction. In this embodiment, one wire cathode 2 is formed by a pair of conductors 13 and 13'.
The electron beam is deflected vertically to a position corresponding to 16 lines.

The 16 vertical deflection electrodes 4 constitute 16 pairs of conductors corresponding to each of the 16 line cathodes 2, and in the end, the electron beam is deflected to draw 240 horizontal lines on the screen 9. do.

Next, each of the control electrodes 6 is composed of a conductive plate 16 having a vertically long slit 14, and a plurality of control electrodes 6 are arranged in parallel in the horizontal direction at predetermined intervals. In this embodiment, 180 conductive plates 15a to 15n for control electrodes are provided (only nine are shown in the figure). Each of the control electrodes 6 separates the electron beam into two picture elements in the horizontal direction and extracts the electron beam, and controls the amount of electron beam passing therethrough in accordance with a video signal for displaying each picture element.

Therefore, if 180 conductive plates 15a to 15n for the control electrodes 5 are provided, 360 pixels can be displayed per horizontal line. In addition, in order to display images in color, each picture element is displayed with phosphors of three colors R, G, and B, and each control electrode 6 has two picture elements of R, G, and H. Each video signal is applied sequentially.

In addition, 180 sets of video signals for one line (2 pixels per set) are simultaneously applied to each of the 180 conductive plates 156 to 15H for the control electrode 6, and the video for one line is simultaneously applied. Displayed.

The horizontal focusing electrode e has a plurality of vertically long slits 16 (180) facing the slits 14 of the control electrode 6 .
The electron beam is composed of a conductive plate 17 having a conductive plate 17, and focuses electron beams for each picture element divided in the horizontal direction into a narrow electron beam.

A plurality of horizontal deflection electrodes 7 are electrically conductive plates 18 arranged vertically on both sides of the slit 16,
18', each electrode 18.18'
A six-step horizontal deflection voltage is applied to horizontally deflect the electron beam for each pixel, and the two sets of R, G, and B phosphors are sequentially irradiated on the screen 9. Make it emit light.

In this embodiment, the deflection range is two picture elements wide for each electron beam.

The accelerating electrode '8 is composed of a plurality of conductive plates 19 provided horizontally at the same position as the vertical deflection electrode 4, and accelerates the electron beam with sufficient energy so that it collides with the screen e.

The screen 9 is constructed by applying a phosphor 20 that emits light when irradiated with an electron beam to the back surface of a glass plate 21, and adding a metal back layer (not shown).

The phosphors 20 are provided with two pairs of phosphors of three colors RoG and B for each slit 14 of the control electrode 60, that is, for each one horizontally divided electron beam. It is applied in vertical stripes.

In FIG. 2, the broken lines drawn on the screen 9 indicate divisions in the vertical direction that are displayed corresponding to each of the plurality of line cathodes 2, and the two-dot chain lines correspond to each of the plurality of control electrodes 5. Indicates the horizontal division displayed. As shown in the enlarged view in Fig. 3, one section partitioned by these two has two R, G, and H phosphors for two picture elements in the horizontal direction.
For example, the size of one block 01, which has a width of 16 lines in the vertical direction, is 1 square block in the horizontal direction,
The vertical direction is 10 mm.

Note that in FIG. 4, the length in the horizontal direction is greatly expanded relative to the length in the vertical direction for clarity.

Further, in this embodiment, only one pair of R, G, and B phosphors 20 for two picture elements are provided for one control electrode 5, that is, for one electron beam. The control electric fence 5 may have R, G, B for 1 picture element or 3 picture elements or more.
Video signals are applied sequentially, and horizontal deflection is performed in synchronization with the video signals.

Next, the basic structure 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 beam to cause the Lasku to emit light 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, and it applies -v1 to the back electrode 1, vv' to the vertical focusing electrode 3.3', and voltage to the horizontal focusing electrode 6. A DC voltage of v6 is applied to the acceleration electrode 3'38, a DC voltage of v8 is applied to the accelerating electrode 3'38, and a DC voltage of ■9 is applied to the screen 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 (2) and a horizontal synchronization signal (H).

The vertical deflection drive circuit 40 includes a vertical deflection counter 25,
As an input cover for the vertical deflection drive circuit 4o, which is composed of a memory 27 for storing vertical deflection signals and a digital-to-analog converter 39 (hereinafter referred to as a DA converter),
The 0 vertical deflection counter 26 (8 pits) using the vertical synchronizing signal V and the horizontal synchronizing signal Hi shown in FIG. 7 is reset by the vertical synchronizing signal V and counts the horizontal synchronizing signal Hi. This vertical deflection counter 26 is counted during an effective scanning period (in this case, 24
The count output is supplied to the address of the memory 27. The memory 27 outputs vertical deflection signal data (here, 10 bits) corresponding to each address, and the p-A converter 39 converts the data to V as shown in FIG.

V' is converted into a vertical deflection signal. In this circuit 240
There is a memory address for storing the vertical deflection signal corresponding to each line of H minutes, and by storing regular data in the memory every 16H minutes, it is possible to obtain a 16-step vertical deflection signal. .

On the other hand, the line cathode drive circuit 26 generates line cathode drive pulses using the vertical synchronization signal V and the output of the vertical deflection counter 26.
I~Yo]. FIG. 8 (a+ is the vertical synchronization signal V,
The relationship between the horizontal synchronizing signal H and the lower six pits of the vertical deflection counter 25 is shown.

Fig. 8 (bl shows the method of creating line cathode drive pulses [A' to Y'] every 16H using these signals.
In the figure, LSB indicates the lowest pitch ()f, and (I, SB+1) means one level above the LSB.

The first line cathode drive pulse [A'] can be created using an R-S flip-flop or the like using the vertical synchronization signal V and the output (LSB+4) of the vertical deflection counter 26.
The line cathode drive pulses [A' to 'Y'] can be obtained by using a shift register to transfer the line cathode drive pulse [A'] using the inverted version of the output (LSB+3) of the vertical deflection counter 26 as a clock. I can do it. This drive pulse [A' to Yo'] is inverted and converted into a line cathode drive pulse [I to Yo], which has a low potential only during each pulse period, and a high potential of about 20 volts during other periods. , are added to each line cathode 2i to 2yo.

Each line cathode 2i to 2yo is heated by a current flowing through it during the high potential of the driving pulse [i to yo].
The heated state is maintained so that electrons can be emitted during the low potential period (I to Y). Accordingly, 15 wire cathodes 2-2
From Y to Y, electrons are emitted only during the 16H period when a low potential drive pulse [I to Y] is applied to each of them. During the period when a high potential is applied, the back electrode 1 and the vertical focusing electrode 3
Since the high potential applied to the linear cathodes 2i to 2yo is more positive than the potential at the position of the linear cathodes 2 determined by the bias voltage applied to the linear cathodes 2i to 2yo, Thus, in the line cathode 2, electrons are emitted sequentially from the upper line cathode 2a to the lower line cathode 2y every 16H period during the effective vertical scanning period.

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 vertically focused to form a flat electron beam.

Next, the line cathode drive pulses [I to Y] and the vertical deflection signal v,
The 0 vertical deflection signals v and v' will be explained using FIG. 9 regarding the relationship between v' and v'. The zero vertical deflection signals v and v' change in steps of 1H by 1H during the 16H period of each line cathode node [I to Y]. 0 vertical deflection signal v,! : Both v' and V' have a center voltage of v4, and are configured to change in opposite directions so that V increases sequentially and V' decreases sequentially. These vertical deflection signals V and V' are applied to the electrodes 13 and 13' of the vertical deflection electrode 4, respectively, and as a result, the electron beams generated from the respective line cathodes 2I to 2Y are deflected in 16 steps in the vertical direction. As mentioned above, on the screen 9, the electron beam is emitted for 16H periods in order from the biased one so that one electron beam draws 16 lines of raster one line at a time from the top, and each electron The beam is deflected one line at a time from top to bottom within 16 vertical sections, so that it can be applied to the screen 9.
At the top, the electron beam is vertically deflected one line at a time from the first line at the top to the 240th line at the bottom, and a total of 240 lines of raster are drawn.

The electron beam thus vertically deflected is horizontally divided into 180 sections and extracted by the control electrode 5 and the horizontal focusing electrode L6. Figure 4 shows one of these categories. The amount of electron beam passing through each section is controlled by the control electrode 6, and the beam is horizontally focused by the horizontal focusing electrode 6 into a single narrow electron beam. The light is deflected as follows, and is sequentially irradiated onto the R, G, and B light beams 20 corresponding to two picture elements on the screen 9. FIG. 3 shows the vertical and horizontal divisions. Each of the control electrodes 5 15a~
The phosphors corresponding to 15n are R, G, B for two picture elements, but for convenience of explanation, one picture element is R1, G1... B1 and the other one is R2, G2. Let's call it B2.

Next, the horizontal deflection drive circuit 41 is composed of a horizontal deflection counter (11 pits), a memory 29 storing horizontal deflection signals, and a DA converter 38. As shown in FIG. 7, the input pulses of the horizontal deflection drive circuit 41 are synchronized with the vertical synchronizing signal V and the horizontal synchronizing signal H, and a pulse 6H having a repetition frequency six times that of the horizontal synchronizing signal H is used.

The horizontal deflection counter 28 is reset by the vertical synchronizing signal V and counts the horizontal six-fold pulse 6H. This horizontal deflection counter 28 is Ic 8 times during 1H, 1■
During this period, the count is counted 240H×6/I (=1440 times), and this count output is supplied to the address of the memory 29.

The memory 29 outputs horizontal deflection signal data (here, 8 bits) according to the address, and the data is sent to the D-A converter 38.
Then, it is converted into horizontal deflection signals such as h and h/ shown in FIG.

This circuit has a memory address for storing horizontal deflection signals corresponding to each of 6 x 240 lines, and by storing 6 pieces of regular data for each line in the memory, it is possible to generate 6 step waves in 1H period. horizontal deflection signals can be obtained.

As shown in Fig. 10, this horizontal deflection signal is a pair of horizontal deflection signals li and hl that change in 6 steps, both of which have a center voltage of v7, h decreases sequentially, and h' increases sequentially. As they progress, they change in opposite directions. These horizontal deflection signals, h/, are respectively applied to electrodes 18 and 18' of horizontal deflection electrode 7, so that each horizontally segmented electron beam is transmitted to
G, B, R.

It is horizontally deflected so that the phosphors of G and B (R1, G1.B1.R2, G2.B2) are sequentially irradiated with H/6.

Thus, in each line raster, the horizontal direction 18
For each section of 0, the electron beam is R,,G1°B1. R2
, G2. Each phosphor 2o of B2 is sequentially irradiated with light.

Therefore, the electron beam is set to R1, G for each horizontal section of each line.
1. B1. R2, G2. By modulating the B2 video signal, a color television image ti can be displayed on the screen 9.

Next, the modulation control portion of the electron beam will be explained.

First, the composite video signal applied to the television signal input terminal 23 is applied to the color demodulation circuit 30, where the R-Y
The G-Y color difference signals are demodulated, the G-Y color difference signals are matrix-based, and these are further combined with the luminance signal Y to form the R, G, and B primary color signals (hereinafter R, G, and B). , B video signal) are output. These R, G, and B video signals are processed by 180 sample and hold circuit sets 31a to 31.
Added to H. Each sample and hold circuit group 318-3
1n is for R1, G1, B1, and R2, respectively.

It has six sample and hold circuits for G2 and B2. These sample and hold outputs are respectively applied to holding memory sets 32a-32n.

On the other hand, the reference clock oscillator 33 is constituted by a PLL (needs-locked Druze) circuit, etc., and in this embodiment, the reference clock 6fsc is six times the color subcarrier fIIO.
It generates a reference clock 2 f8° which is double the reference clock. The reference clock is controlled to always have a constant phase with respect to the horizontal synchronizing signal H. The reference clock 2'BC is applied to the deflection pulse generation circuit 42, and is a signal 6H which is six times as large as the horizontal synchronizing signal H.

Signal switching pulse r1 ""1, bl" for H and i
2'q2. I am getting a B2 pulse. On the other hand, the reference clock 6f is applied to the sampling pulse generation circuit 34, where it is delayed by one clock period by a shift register, and is converted into a horizontal period (63,5μ5ec).
During the effective horizontal scanning period (approximately 60 μ5 ec), 1080 sampling pulses Ra1 to Bn2 are sequentially generated, and then one transfer pulse t is generated.

These sampling pulses Ra1 to Bn2 correspond to each picture element when one line of the video to be displayed is divided into 360 picture elements in the horizontal direction, and their positions are determined by the horizontal synchronizing signal H.
is controlled so that it is always constant.

These 1080 sampling pulses Ra1 to Bn2 correspond to 180 sample and hold circuit sets 31a to 3, respectively.
1n, six pixels each are added to R1, G1 . B1
．． R2, G2. Each video No. 2 of B2 is individually sampled and held.

The sample held 180 pairs of R1, G1゜B
1. R2, G2. After the B2 video signal is sampled and held for one line, 180 sets of memo IJ 32 a to 3 are stored.
At 2H, the signals are transferred all at once by the transfer pulse t, and are held here for the next horizontal period. This retained R1. G
1. B1. I't2. G2. The B2 signal is applied to switching circuits 35a-35n. Switching circuit 3
5a to 35n are R1, G1°B1. R2, G2
．． It is constructed of a tri-state or analog gate having individual input terminals of B2 and a common output terminal that sequentially switches and outputs them.

The output of each switching circuit 35a-35n is applied to 180 sets of pulse width modulation (PWM) circuits 37a-37n, where R1. G1. B1.
R2, G2. The reference pulse signal is pulse width modulated according to the magnitude of the B2 video signal and output. The repeating period of the reference pulse signal is the above signal switching path/l/sr1*
It is desirable that the pulse width of q1 +b1 e B21q2 'b2 is sufficiently small, for example, 1
:10 to about 1:100 is used.

The outputs of the pulse width modulation circuits 37a to 37n are individually applied to the 180 conductive plates 15a to 15n of the control electrode 6 of the display element as control signals for modulating the electron beam. Each of the switching circuits 35a to 35n receives a switching pulse r1+91m''1+B2+ applied from the switching pulse generating circuit 36.
The switching is controlled simultaneously by 92 ml) 2 . The switching pulse generation circuit 36 receives the signal switching pulse r11q1 +b from the deflection pulse generation circuit 42 described above.
1+r2eq2 eb2, each horizontal period is divided into 6 and the switching circuit 35 is divided into H/6.
a ~35ni switching, R1, G1°B1. R2, G2
．． The switching signal r1 is configured to time-divide and sequentially output each video signal of B2 and supply it to the pulse width modulation circuits 37a to 37n.
*q1el)1 e B2 +q2 +1)2 is generated.

What should be noted here is that the switching circuit 35a-3
R1 in 5n. G1. B1. R2, G2°B2 video signal supply switching and electron beam R1, G1 . B1. The horizontal deflection of R2, G2 and B2 for switching the irradiation to the phosphor is synchronously controlled so that they completely match both in timing and order. As a result, when the R1 phosphor is irradiated with the electron beam, the irradiation amount of the electron beam is controlled by the R1 video signal, and the G1. B1. R2, G2. B
2 is controlled in the same way, and R1, G,
, B1. R2・G2. R2 The light emission of each party light is R1, G1°B4. R2, G2. Each picture element is controlled by the B2 video signal, and each picture element is displayed by emitting light according to the input video signal. Such control is 1
This is done simultaneously for 180 lines (2 pixels each), and an image of 360 pixels per line is displayed, and 2
One video is displayed on the screen 9 by sequentially performing the 40-minute lines starting from the upper line.

The above operations are performed on one input television signal.
This is repeated for each field, and as a result, a moving television image is displayed on the screen 9 in the same way as a normal television receiver.

Problems to be Solved by the Invention In the image display device as described above, the landing position of each electron beam on the screen is strictly determined.
Furthermore, although the focus diameter is narrowed down to an appropriate size, horizontal positional deviation and defocus impair brightness uniformity and color reproducibility. It is thought that such deviations and defocusing phenomena in the electron beam landing device are caused by changes over time in drive circuit characteristics such as the horizontal deflection waveform, or by expansion and contraction over time of each electrode that makes up the display element. In order to keep the landing position and focus diameter constant, it is necessary to make the deflection waveform amplification circuit extremely precise, and to use electrode materials that have very little expansion and contraction. This is not practical as it leads to an increase in power consumption and cost.

Means for Solving the Problems In the present invention, outside the effective screen on the screen surface of the display element,
For example, phosphors of multiple colors such as three colors R, G, and B are applied in vertical stripes with the same pitch as the effective screen.
When the electron beam is irradiated on the correct position on the screen, the light emitting amount of the three colors of phosphors is detected by the light receiving element, the signal is stored in the memory circuit, and the signal from each light receiving element is transmitted during actual operation. The signal stored in the memory circuit is compared with the signal stored in the memory circuit, and the difference is fed back to a part of the drive circuit.

The image display device of the present invention has a light receiving element that detects the horizontal landing position and horizontal focus state of the electron beam on the screen, and has means for feeding back position signals and focus signals during actual operation. By providing this, it is possible to control the horizontal landing position and horizontal focus of the electron beam so that they are always maintained in a normal state.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. As shown in FIG. 1, in addition to the phosphors 20 on the effective screen of the screen 9, a set of phosphors B0. R1, G1. B1°R72, G2. B2
．． Apply R3 (50") in vertical stripes. The phosphor 50 is coated with R1 (R3) using the same driving waveform as the phosphor 2o.
), G4. B1. R2, G2. B2 (Bo) is scanned with an electron beam in order and emits light. The amount of light emitted by the phosphor 6
Three light receiving elements 51 . 52.53
(e.g. phototransistor) when detecting
If the light-receiving element 61 is filtered to have high sensitivity in the red band, 52 in the absolute color band, and 63 in the blue band, Bo, R1°G, , B1 . R2, G2. B2. R3
The amount of light emitted from each can be obtained in a time-division manner.

FIG. 2 is a block diagram of the feedback control system of the present invention, and the light receiving elements 51, 52.
The signals from 53 are converted into digital signals by A/D converters 56 after passing through multiplexers 54 and stored in memory 56. Comparing this signal with a signal stored in another address of the memory 56 when the electron beam irradiates each of the RlG and B of the phosphor 5o in the correct focus state using ftcpas'y,
It is stored again in the memory 66 as appropriate control data to be fed back. By adding this data with the horizontal deflection data read from the memory 29 every 1 period of horizontal deflection, that is, every 1H by an adder 68 and outputting the result, the horizontal landing position and horizontal focus of the electron beam are in a normal state. It will be controlled.

By the way, the horizontal landing position shift of the electron beam, the horizontal defocus state, and the CPU 57
The relationship between the comparison operations within will be explained in detail with reference to FIG. First, if the electron beam is irradiated at a regular position with a regular focus, at the timing when R1 is irradiated, there is almost no amount of light emitted from other than R1, as shown by the solid line in Figure 3 (al). Therefore, the signals from other than the light receiving element 51 are zero.If a signal appeared at the light receiving element 62 at this time, the electron beam would also irradiate a part of G1, as shown by the broken line in the same figure (al). Therefore, it is assumed that the landing position has shifted in the direction of 01, and the CPU 57 converts it into data that increases the amount of deflection of R4 and stores it in the memory 56.
If a signal appears on the light receiving element 63 at the same timing as above, it is assumed that the landing position has shifted in the direction of Bo as shown by the broken line in the figure [bl], and CP tys 7.
is converted into data that reduces the amount of deflection of R1 and is stored in the memory 66.

Furthermore, if signals appear on both light receiving elements 51 and 52 at the same timing, the focus diameter becomes larger (defocused) as shown by the broken line in the figure (cl).
Considering this, the CPU 57 converts the data to reduce the focus diameter of R1 and stores it in the memory 66. The above comparison operation is performed in G1. B1. R2, G2. B2
It is sufficient to perform each of the steps in turn.

Effects of the Invention As described above, according to the present invention, a vertical striped phosphor coated on a screen and means for detecting the amount of light emitted by the phosphor when irradiated with an electron beam using a light receiving element are provided. When the electron beam is irradiated at the correct position on the screen with the correct focus state, the signal from the photodetector stored in memory is compared with the signal from the photodetector during actual operation, and the difference is calculated. By feeding back to a part of the display element drive circuit, it is possible to control the electron beam so that it is always irradiated at the correct position on the screen with the correct focus state, and it is possible to control the change over time of the drive circuit characteristics or the display It is possible to provide an image display device that does not suffer from horizontal landing position shifts caused by expansion and contraction of electrodes constituting elements over time, screen brightness changes due to horizontal defocus, and color shifts.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the coating state of the phosphor on the screen of an image display element used in an image display device according to an embodiment of the present invention, and FIG. 2 is a front view of a feedback control system of the same image display device. 3 is a front view illustrating the landing position shift and defocus state of the electron beam; FIG. 4 is an exploded perspective view of an example of an image display element used in the conventional image display apparatus and the present invention; FIG. The figure is an enlarged front view of the fluorescent surface of the image display element, Figure 6 is a block diagram showing the basic configuration of the drive circuit of the image display element, and Figure 7 is a waveform diagram for explaining the operation of the vertical deflection drive circuit. , FIG. 8 is a waveform diagram for explaining the operation of the line cathode drive circuit, FIG. 9 is a waveform diagram for each drive signal, and FIG. 10 is a waveform diagram for explaining the operation of the horizontal deflection drive circuit. 2.2 I~2 Y... Line cathode, 4... Vertical deflection electric fence, 5... Beam flow control electrode, 7...
...Horizontal deflection electrode, 9...Screen, 1
Q...Slit, 2゜...Fluorescent material, 2
3...Input terminal, 24...Synchronization separation circuit, 25...Vertical deflection counter, 26...
... Line cathode drive circuit, 27 ... Memory, 2
8...Horizontal deflection counter, 29...
・Memory, 3o... Color demodulation circuit, 31a to 31
n...Sample hold circuit, 32a to 32n
... Memory, 33 ... Reference clock oscillator, 34 ... Sampling pulse generation circuit,
35a-35n...Switching circuit, 36.
...Switching pulse generation circuit, 37a to 37
n...PWM circuit, 38...D/A converter, 39...D/A converter, 40...
・Vertical deflection drive circuit, 41...Horizontal deflection drive circuit, 42...Deflection pulse generation circuit, 60...
...Fluorescent body, 51, 52゜63... Light receiving element, 66... A/D converter, 66...
Memory, 57...CPU, 58...Adder. Name of agent: Patent attorney Toshio Nakao and 1 other person21
Figure 12 Figure 3 (a-2 Cb) Figure 5 Figure 6 Figure 7 Figure 8 (a) LSB ÷ 4 16M (b Noho'"

Claims (2)

[Claims] (1) a plurality of line cathode electron beam sources, a screen having a phosphor that emits light when irradiated with the electron beam, and a focusing electrode that focuses the electron beam generated by the electron beam source; The display element includes an electrostatic deflection electrode that deflects the electron beam on the way to the screen, and a control electrode that controls the emission intensity by controlling the amount of the electron beam irradiated onto the screen. On the screen surface of this display element, phosphors of multiple colors are applied in vertical stripes at the same pitch as the pitch within the effective screen, and the amount of light emitted by each of these phosphors is detected by a light-receiving element. An image display device characterized in that the horizontal landing position and horizontal focus state of the electron beam on the screen are detected. (2) The signals from each light receiving element when the electron beam is irradiated on the screen at the correct position in the normal focus state are stored in the memory circuit, and the signals from each light receiving element and the memory circuit are stored in the memory circuit during actual operation. It is characterized by controlling the electron beam so that it irradiates the correct position on the screen with the correct focus state by comparing the signals and feeding back the difference to a part of the drive circuit. An image display device according to claim 1.