JP2652386B2 - Image display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention generates an electron beam for each section when a screen on a screen is divided into a plurality of sections in a vertical direction, and for each section, The present invention relates to a device for displaying a plurality of lines by deflecting an electron beam in a vertical direction and displaying a television image as a whole.

(Prior Art) Conventionally, a cathode ray tube is mainly used as a display element for displaying a color television image. However, the conventional cathode ray tube has a very long depth compared to the screen size, and is a thin television. It was impossible to make a John receiver. Recently, EL display devices, plasma display devices, liquid crystal display devices, and the like have been developed as flat display devices, but all of them are insufficient in terms of performance such as luminance, contrast, and color display, and are practically used. Has not been reached.

Accordingly, the present applicant has proposed a novel display device in Japanese Patent Application No. 56-20618 (Japanese Patent Application Laid-Open No. 57-135590) as a device for achieving a flat display device using an electron beam.

This is because when the screen on the screen is vertically divided into multiple sections, an electron beam is generated for each section, and each line is deflected vertically for each section to display multiple lines Then, a television image is displayed as a whole.

First, an example of a basic configuration of the image display element used here will be described with reference to FIG. The display element comprises a back electrode 1, a linear cathode 2 as a beam source, vertical focusing electrodes 3, 3 ', a vertical deflection electrode 4, a beam flow control electrode 5, a horizontal focusing electrode 6, a horizontal A deflecting electrode 7, a beam accelerating electrode 8, and a screen 9 are arranged and configured, and these are housed in a evacuated flat glass bulb (not shown). Line cathode 2 as beam source
Are stretched in the horizontal direction so as to generate electron beams distributed linearly in the horizontal direction. A plurality of such linear cathodes 2 (four in this case, 2a to 2d in this case) are provided at appropriate intervals. Only shown). In this embodiment, it is assumed that 15 are provided. Let them be 2a to 2o. These line cathodes 2 are formed by coating an oxide cathode material for emitting thermoelectrons on the surface of, for example, a tungsten wire of 10 to 20 μφ. These linear cathodes 2a to 2o are heated so as to be able to generate a thermionic beam by passing a current, and emit an electron beam from the linear cathode 2a in order for a predetermined time as described later. Is controlled. The back electrode 1 suppresses the generation of an electron beam from another linear cathode 2 other than the linear cathode 2 controlled to emit the electron beam for a certain period of time, and directs the generated electron beam only in the forward direction. And push it out. This back electrode 1 may be formed by a coating film of a conductive material attached to the inner surface of the rear wall of the glass bulb. 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 facing each of the linear cathodes 2a to 2o. The electron beam emitted from the linear cathode 2 is extracted through the slit 10 and focused in the vertical direction. Let it. Horizontal direction 1
Simultaneously extract the electron beam of the line (360 picture elements).
In the figure, only one of the horizontal sections is shown. The slit 10 may be provided with a crosspiece at an appropriate interval in the middle, or may be substantially formed as a slit by a row of through holes provided in a large number at a small horizontal interval (interval of almost contact). May be.
The vertical focusing electrode 3 'is similar.

A plurality of vertical deflection electrodes 4 are horizontally arranged at intermediate positions of the slits 10, each having a conductor 13, 13 'provided on the upper and lower surfaces of an insulating substrate 12. ing. Then, the opposing conductor 1
A vertical deflection voltage is applied between 3, 13 'to deflect the electron beam in the vertical direction. In this embodiment, a pair of conductors 1
3, 13 'deflects the electron beam from one linear cathode 2 to a position corresponding to 16 lines in the vertical direction. Then, fifteen conductor pairs corresponding to each of the fifteen linear cathodes 2 are formed by the sixteen vertical deflection electrodes 4, and eventually the electron beam is deflected so as to draw 240 horizontal lines on the screen 9. I do.

Next, the control electrodes 5 are each formed of a conductive plate 15 having a slit 14 that is long in the vertical direction, and a plurality of the control electrodes 5 are arranged side by side at a predetermined interval in the horizontal direction. In this embodiment, 180 control electrode conductive plates 15-1 to 15-n are provided (only nine are shown in the figure). Each of the control electrodes 5 takes out the electron beam by dividing it into two picture elements in the horizontal direction, and controls the passing amount according to a video signal for displaying each picture element. Therefore, if 180 conductive plates 15-1 to 15-n for the control electrode 5 are provided, 360 picture elements can be displayed per horizontal line. In order to display images in color, each picture element
R, G, and B phosphors are used for display, and R, G, and B video signals for two picture elements are sequentially applied to each control electrode 5. Also, 180 conductive plates 15-1 to 15-n for the control electrode 5 are used.
Are simultaneously applied with 180 sets of video signals for one line (two picture elements per set), and one line of video is displayed at a time.

The horizontal focusing electrode 6 is composed of a conductive plate 17 having a plurality of vertically long (180) slits 16 opposed to the slits 14 of the control electrode 5, and the electrons for each picture element divided in the horizontal direction are provided. The beams are each focused in the horizontal direction to form a thin electron beam.

A plurality of horizontal deflection electrodes 7 are provided at a position on both sides of the slit 16 in a vertical direction.
A six-stage horizontal deflection voltage is applied to each of the electrodes 18 and 18 'to deflect the electron beam for each picture element in the horizontal direction.
The G and B phosphors are sequentially irradiated to emit light.
In this embodiment, the deflection range is the width of two picture elements for each electron beam.

The beam acceleration electrode 8 is composed of a plurality of conductive plates 19 provided at the same position as the vertical deflection electrode 4 in the horizontal direction, and accelerates the electron beam so as to collide with the screen 9 with sufficient energy.

The screen 9 is configured such that a phosphor 20 that emits light when irradiated with an electron beam is applied to the back surface of a glass plate 21 and a metal back layer (not shown) is added. The phosphor 20 is provided with two pairs of phosphors of three colors of R, G, and B for one slit 14 of the control electrode 5, that is, for each electron beam divided in the horizontal direction. And
It is applied in stripes in the vertical direction. In FIG. 4, the dashed lines drawn on the screen 9 indicate the vertical divisions 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. In one section partitioned by these two, there are two picture elements of R, G, B phosphors 20 in the horizontal direction as shown in an enlarged view in FIG.
It has a width of 16 lines in the vertical direction. The size of one section is, for example, 1 mm in the horizontal direction and 9 mm in the vertical direction.

It should be noted that, in FIG. 4, the length in the horizontal direction is greatly extended in the vertical direction for easy understanding.

Further, in this embodiment, one control electrode 5, that is, one control electrode 5,
Only one pair of R, G, B phosphors 20 for two picture elements is provided for each electron beam. Of course, one or three or more picture elements may be provided. First, R, G, B video signals for one picture element or more than three picture elements are sequentially applied to the control electrode 5, and horizontal deflection is performed in synchronism therewith.

Next, the basic configuration of a drive circuit for displaying a television image on this display element and the waveforms of each part will be described with reference to FIG. First, a driving portion for irradiating the screen 9 with an electron beam to emit a raster will be described.

A circuit for the power supply circuit 22 for applying a predetermined bias voltage (operating voltage) to the electrodes of the display element, the back electrode 1 -V _1, the vertical focusing electrode 3,3 'V ₃ in, V _3' , Horizontal focusing electrode 6
V ₆ The, V ₈ in beam accelerating electrode 8, the screen 9 V ₉
Is applied.

Next, a composite video signal of a television signal is applied to an input terminal 23, and a vertical synchronizing signal V and a horizontal synchronizing signal H are separated and extracted by a sync separation circuit 24.

The vertical deflection driving circuit 40 includes a vertical deflection counter 25, a memory 27 for storing horizontal deflection signals, and a digital-analog converter 39 (hereinafter, referred to as a DA converter). As an input pulse of the vertical deflection drive circuit 40, a vertical synchronization signal V and a horizontal synchronization signal H shown in FIG. 5 are used. The vertical deflection counter 25 (8 bits) is reset by the vertical synchronization signal V and counts the horizontal synchronization signal H.
The vertical deflection counter 25 counts an effective scanning period (a period of 240H in this case) excluding the vertical blanking period in the vertical cycle, and the count output is supplied to an address of the memory 27. The vertical deflection signal data (8 bits in this case) corresponding to each address is output from the memory 27, and the DA converter 39 outputs the data of υ and υ ′ shown in FIG. 7 {D in FIG. 6 (b)}. It is converted to a vertical deflection signal. In this circuit
There is a memory address for storing a vertical deflection signal corresponding to each line of 240H. By storing regular data in the memory every 16H, 16 levels of vertical deflection signals can be obtained.

On the other hand, the line cathode drive circuit 26 uses the vertical synchronization signal V and the output of the vertical deflection counter 25 to output the line cathode drive pulses a to
Create o. FIG. 8A shows the relationship among the vertical synchronization signal V, the horizontal synchronization signal H, and the lower 5 bits of the vertical deflection counter 25. FIG. 8 (b) shows that these signals are used for 16H.
A method for generating the linear cathode drive pulses a 'to o' for each of the following will be described.
In FIG. 8, LSB indicates the least significant bit, and (LSB + 1) indicates LSB.
Means the next higher bit.

The first line cathode driving pulse a 'is generated by using the vertical synchronizing signal V and the output (LSB + 4) of the vertical deflection counter 25 as R-
An S flip-flop can be used to generate the linear cathode driving pulses b 'to o'. The linear cathode driving pulse a 'is output from the vertical deflection counter 25 (LSB
It can be obtained by transferring the inverted version of +3) as a clock. The driving pulses a 'to o' are inverted to be at a low potential only during each pulse period, and are set to a high potential of about 20 volts during other periods.
And converted into .omega.o (FIG. 6 (b) E) and added to each of the line cathodes 2a to 2o.

Each of the line cathodes 2a to 2o is heated by increasing the current during the high potential of the drive pulse a to o, and the heating state is maintained so that electrons can be emitted during the low potential period of the drive pulse a to o. You. As a result, electrons are emitted from the fifteen line cathodes 2a to 2o only during the 16H period in which the low-potential drive pulses a to o are applied. During the period when high potential is applied,
Since the high potential applied to the line cathodes 2a to 2o is more positive than 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, No electrons are emitted from the linear cathodes 2a to 2o. Thus, in the linear cathode 2, during the effective vertical scanning period, electricity is sequentially emitted from the upper linear cathode 2a toward the lower linear cathode 2o for 16H periods. The emitted electrons are pushed forward by the back electrode 1 and are focused on the vertical focusing electrode 3.
Pass through the opposing slit 10 and are converged in the vertical direction to become a flat electron beam.

Next, the linear cathode driving pulses a to o and the vertical deflection signals υ,
The relationship with υ 'will be described with reference to FIG. Ninth
7A is a waveform chart of a linear cathode drive pulse, FIG. 7B is a waveform chart of a vertical deflection signal, and FIG. 7C is a waveform chart of a horizontal deflection signal. The vertical deflection signals υ and υ ′ in FIG. 9 (b) change by 1H during the 16H period of each line cathode pulse a to o in FIG. 9 (a) and change in 16 steps. Vertical deflection signals υ and υ ′
Than both those centers voltage is V _4, upsilon is sequentially increased, upsilon '
Are changed in directions opposite to each other so as to gradually decrease. These vertical deflection signals υ and υ ′ are applied to the electrodes 13 and 13 ′ of the vertical deflection electrode 4, respectively. As a result, the electron beams generated from the respective linear cathodes 2a to 2o are vertically deflected in 16 steps. As described above, on the screen 9, one electron beam is deflected so as to sequentially draw 16 lines of raster from the top one line at a time.

As a result, the electron beams are emitted for 16 H periods in order from the upper one of the fifteen line cathodes 2a to 2o, and each electron beam is one line at a time from top to bottom in 15 vertical sections. By being deflected, the electron beam is vertically deflected one line at a time from the first line at the upper end to the 240th line at the lower end on the screen 9, and a raster of 240 lines in total is drawn.

The electron beam vertically deflected in this manner is applied to the control electrode 5
And the horizontal focusing electrode 6 is divided into 180 sections in the horizontal direction and taken out. FIG. 5 shows one of them. The passing amount of this electron beam is controlled by the control electrode 5 for each section, and the electron beam is focused in the horizontal direction by the horizontal focusing electrode 6 to form one thin electron beam.
R, G, B phosphors 2 corresponding to two picture elements on the screen 9 are deflected in six stages in the horizontal direction by horizontal deflection means described below.
Irradiated sequentially to 0. FIG. 5 shows vertical and horizontal divisions. Each phosphor corresponding to 151 to 15-n is 2 pixels worth R of the control electrode 5, G, becomes is B, for convenience of explanation, the one pixel and R _1, G _1, B _1, Let the other be R ₂ , G ₂ , B ₂ .

Next, the horizontal deflection driving circuit 41 includes the horizontal deflection counter 28.
(11 bits), memory 29, D for storing horizontal deflection signal
-A converter 38. Horizontal deflection drive circuit 41
Of the vertical synchronizing signal V as shown in FIG.
, And a pulse 6H having a repetition frequency six times that of the horizontal synchronization signal H is used. Horizontal deflection counter
28 is reset by the vertical synchronizing signal V,
Count double pulse 6H. This horizontal deflection counter
28 counts 6 times during 1H and 240H × 6 / H = 1440 times during 1V, and this count output is supplied to the address of the memory 29. The horizontal deflection signal data (8 bits in this case) corresponding to the address is output from the memory 29, and the DA converter 38 outputs h, h 'shown in FIG. 10 (FIG. 6 (b) C). Is converted into such a horizontal deflection signal. In this circuit, 6 × 240
There is a memory address for storing a horizontal deflection signal corresponding to each line, and there is a regular 6 for each line.
By storing this data in the memory, a horizontal deflection signal of a six-step wave can be obtained in the 1H period.

The horizontal deflection signal, as shown in FIG. 10, a pair of horizontal deflection signals h and h that varies six stages 'is, in both those centers voltage is V _7, h is sequentially decreased, h' is They change in opposite directions so as to increase sequentially. These horizontal deflection signals h and h 'are respectively applied to the electrodes 18 and 1 of the horizontal deflection electrode 7.
8 '. As a result, each electron beam divided in the horizontal direction is applied to the R, G, and R of the screen 9 during each horizontal period.
The phosphors of B, R, G, and B (R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ ) are horizontally deflected so as to be sequentially irradiated with H / 6 at a time. Thus, in the raster of each line, the electron beams are sequentially applied to the respective phosphors 20 of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ every 180 horizontal sections.

Therefore, the electron beam is applied to each horizontal section of each line by R ₁ , G
_A color television image can be displayed on the screen 9 by modulating with the video signals of ₁ , B ₁ , R ₂ , G ₂ , and B ₂ .

Next, the modulation control portion of the electron beam will be described. First, the composite video signal applied to the television signal input terminal 23 is applied to a color demodulation circuit 30, where the RY and BY color difference signals are demodulated and the GY color difference signals are matrix-combined. Further, they are combined with the luminance signal Y to produce R, G, B primary color signals (hereinafter referred to as R, G, B video signals).
Is output. The R, G, and B video signals are applied to 180 sample-and-hold circuit sets 31-1 to 31-n. Each of the sample-and-hold circuit sets 31-1 to 31-n is connected to R ₁
Use has for G _1, for B _1, for R _2, for G _2, six sample and hold circuits for B _2. These sample hold outputs are applied to holding memory sets 32-1 to 32-n, respectively.

On the other hand, the reference clock oscillator 33 is constituted by a PLL (phase-locked loop) circuit or the like, in this embodiment, to generate the color subcarrier f 6 times the reference clock 6f _sc twice the reference clock 2f _sc in _sc . The reference clock is controlled so as to always have a constant phase with respect to the horizontal synchronization signal H. The reference clock 2f _sc is applied to the deflection pulse generation circuit 42, and the signals 6H and H / 6, which are six times the horizontal synchronization signal H, are used.
The signal switching pulses r ₁ , g ₁ , b ₁ , r ₂ , g ₂ , b ₂ {FIG. 6 (b)} are obtained. On the other hand, reference clock 6f
_{The sc} is applied to the sampling pulse generation circuit 34, where it is delayed by one cycle of the clock by the shift register, for example, so that 1080 pieces of the horizontal cycle (63.5 μsec) are output during the effective horizontal scanning period (about 50 μsec). Sampling pulse R
_{11, G 11, B 11,} R 12, G 12, B 12, R 21, G 21, B 21, R 22, G 22, B 22 ~R
_n1 , _Gn1 , _Bn1 , _Rn2 , _Gn2 , _Bn2 {FIG. 6 (b)} are sequentially generated, and thereafter, one transfer pulse t is generated. The sampling pulse R ₁₁ .about.B _n2 correspond to the respective picture elements when dividing one line of the image to be displayed on the picture elements in the horizontal direction 360, its position is always constant with respect to the horizontal synchronizing signal H Is controlled so that

The 1080 sampling pulses R ₁₁ .about.B _n2 respectively
Six are added to each of the 180 sample-and-hold circuit sets 31-1 to 31-n, whereby each of the sample-and-hold circuit sets 31-1 to 31-n has one line when divided into 180 pieces. The video signals of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ for the two picture elements are individually sampled and held. The 180 sets of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ video signals sampled and held are stored in the 180 sets of memory sets 32-1 to 32-n Are transferred all at once by the transfer pulse t, and are held here for the next one horizontal period. The held signals of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ are applied to the switching circuits 35-1 to 35 -n. Switching circuit
35-1 through 35-n, the tri-state or analog, each having a _{R 1, G 1, B 1} , R 2, G 2, the common output terminal B ₂ of the individual input and sequentially switched them outputs It is constituted by a gate.

The output of each switching circuit 35-1 to 35-n is applied to 180 sets of pulse width modulation (PWM) 37-1 to 37-n, where R ₁ , G ₁ , B ₁ , The reference pulse signal is pulse width modulated according to the magnitude of the R ₂ , G ₂ , B ₂ video signal and output. The repetition period of the reference pulse signal is desirably sufficiently smaller than the pulse width of the above-described signal switching pulses r ₁ , g ₁ , b ₁ , r ₂ , g ₂ , b ₂ , for example,
About 1:10 to 1: 100 is used.

The outputs of the pulse width modulation circuits 37-1 to 37-n are individually applied to the 180 conductive plates 15-1 to 15-n of the control electrode 5 of the display element as control signals for modulating the electron beam. Added. Each switching circuit 35-1 to 35-n
Are simultaneously controlled by the switching pulses r ₁ , g ₁ , b ₁ , r ₂ , g ₂ , b ₂ applied from the switching pulse generating circuit 36. The switching pulse generation circuit 36 is a signal switching pulse r ₁ , g ₁ ,
b ₁ , r ₂ , g ₂ , b ₂ , and each horizontal period is 6
Divided by switching the switching circuits 35-1 through 35-n by H / 6, sequentially outputs the time division of each video signal of _{R 1, G 1, B 1} , R 2, G 2, B 2, pulses width modulation circuit 37-1 to 37-n switching signal to supply to _{r 1, g 1, b 1} , r 2, g 2, b 2 generates.

It should be noted here that the switching circuits 35-1 to 35-1
Switching of supply of video signals of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ in 35-n, and electron beams R ₁ , G ₁ ,
The horizontal control of the switching of the irradiation of the phosphors B ₁ , R ₂ , G ₂ , and B _{2 to} the phosphors is synchronously controlled such that the timings and the order completely match. Thereby, when the electron beam is irradiated on the R ₁ phosphor, the irradiation amount of the electron beam is controlled by the R ₁ image signal, and G ₁ , B ₁ ,
R ₂ , G ₂ , and B ₂ are similarly controlled, and R ₁ , G ₁ ,
The light emission of each of the phosphors B ₁ , R ₂ , G ₂ , B _{2 corresponds} to R ₁ , G ₁ , B ₁ , R ₂ , G
_2, will be respectively controlled by B ₂ of the video signal is the respective picture element is a light emitting display according to the video signal input. This control is performed simultaneously for 180 sets of one line (each of two picture elements) to display an image of 360 picture elements for one line, and further for the 240H line, it is sequentially performed from the upper line, Will be displayed on the screen.

The above operations are performed when the input television signal 1
This is repeated for each field, and as a result, a moving image of a moving image is displayed on the screen 9 in the same manner as in a normal television receiver.

(Problems to be Solved by the Invention) However, in the above configuration, the linear cathode 2 is stretched in the horizontal direction, and both ends thereof are not easily heated.
The amount of the emitted electron beam becomes smaller toward the end. Therefore, there has been a problem that the horizontal ends of the entire screen are darker than the center. In addition, since a potential gradient is created by the flow of an electron beam such as a vertical focusing electrode, there is also a problem that brightness unevenness occurs at both upper and lower ends in the vertical direction.

Further, since the electron beam is irradiated from one linear cathode 2 to the screen 9 for each vertical section, the distance from the linear cathode 2 to the screen 9 is located at the center and both upper and lower ends in one vertical section. Therefore, there is a problem that lightness and darkness in the vertical direction appear in one section in each vertical direction.

The present invention has been made in view of the above problems, and has as its object to provide an image display device that can display an image with uniform brightness over the entire screen.

(Means for Solving the Problems) In order to achieve the above object, an image display device of the present invention includes a screen coated with a phosphor that emits light by being irradiated with an electron beam, and a screen of the screen. An electron beam source for generating an electron beam for each vertical section obtained by dividing the screen vertically into a plurality of sections, and a horizontal section obtained by dividing an electron beam generated by the electron beam source into a plurality of screens on the screen in the horizontal direction. Separating means for irradiating the screen with the electron beam, a deflection electrode for deflecting the electron beam in a plurality of stages in the vertical and horizontal directions until reaching the screen, and an electron separated for each of the horizontal sections. A beam flow control electrode that controls the amount of light emitted from the screen onto the screen to control the amount of light emitted from each of the picture elements on the screen of the screen; An image display device comprising a focusing electrode for controlling the emission size on the phosphor surface, a back electrode for controlling the amount of the electron beam from the electron beam source, and an accelerating electrode for accelerating the irradiation of the electron beam to the screen. And an A / D converter for A / D conversion of the video primary color signals (R, G, B signals) for driving the beam flow control electrodes. A uniform signal is applied to the reference voltage of the A / D converter. By using a luminance correction signal that has a waveform similar to the luminance distribution of the screen when the image is input and is repeated for each horizontal deflection period, vertical deflection period, or each vertical section, the luminance and the luminance of the image reproduced on the screen surface can be improved. It has a configuration in which the hue can be arbitrarily changed.

(Operation) According to the above-described configuration, the present invention provides a configuration in which a video primary color signal corresponding to a dark portion of the entire screen, that is, upper and lower left and right edges of the screen and upper and lower ends of each vertical section is input. By narrowing the width of the reference voltage of the A / D converter, it is possible to indirectly amplify the video primary color signal and obtain uniform brightness over the entire screen.

Hereinafter, an image display device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1A is a configuration diagram of a luminance correction circuit of an image display device according to an embodiment of the present invention, and FIG. 1B is a schematic diagram of an input waveform thereof. In FIG. 1, reference numeral 23 denotes a composite video signal input terminal, and reference numeral 30 denotes a color demodulation circuit for demodulating the above-mentioned signals into video primary color signals (R, G, B signals). Reference numeral 50 denotes a luminance correction signal input terminal.
By setting the reference voltage (upper limit) of the D converters 51A to 51C, it is possible to indirectly modulate the video primary color signal.

Now, let us consider a case where a waveform as shown in (a) is used as the luminance correction signal. The waveform (a) is an inverted parabola waveform (horizontal near the center of the waveform, and low output at both ends of the waveform) which repeats the horizontal synchronization signal H (or the vertical synchronization signal V) in synchronization. Is indirectly modulated to compensate for the characteristics of the conventional image display element in which both ends in the horizontal direction (or both upper and lower ends in the vertical direction) are dark as a whole screen.

In addition, when the waveform shown in (a) is considered, it is possible to compensate for the characteristic of the image display element that the upper and lower ends in one vertical section (16 horizontal lines) are dark, as in the above example.

Further, by using a waveform (C) in which the two waveforms are superimposed, the two effects can be obtained simultaneously.

FIG. 2 is an example of a luminance correction circuit that indirectly modulates a video primary color signal with a parabola waveform that repeats in a horizontal synchronization cycle. In the figure, reference numeral 60 denotes a flip-flop for generating a sine wave having a frequency of 2H from the horizontal synchronizing signal H, and reference numeral 61 denotes an AD converter for indirectly modulating a video primary color signal by a luminance correction signal. Although not shown, this A-
The digital video signal output from the D converter 61 is stored in an image memory for each picture element, the digital video signal is read out from this image memory to each picture element, modulated into a pulse width modulation signal, and then applied to the beam flow control electrode. I do.

FIG. 3 is a waveform diagram at each point of the brightness correction circuit.

Now, the luminance correction circuit will be described by dividing it into four blocks A to D. A is a block for inputting the horizontal synchronizing signal a to the flip-flop 60 and forming a sine wave b through a filter of a half frequency-divided waveform. B is a block for generating two half-waves (c, d) based on the sine wave b, and a block C at the next stage adds these two signals and generates a diode D1.
To obtain a desired luminance correction signal e. Here, the degree of blunting of the waveform is adjusted by setting the voltage clipped by the diode D1 by adjusting the resistor R16. The block D includes the luminance correction signal e
Is used as the reference voltage (upper limit) of the A / D converter 61 to indirectly modulate the video primary color signal f, as if g
The same effect as when the video primary color signal is used can be obtained. Here, the amplitude of the waveform is adjusted by the resistor R17 so that the luminance of the entire screen becomes uniform when a uniform signal (for example, a 100% white signal) is applied over the entire surface.
It is set by adjusting the degree of blunting by 16.

That is, modulation is applied in a direction in which the luminance at both ends of the linear cathode decreases, the difference in the distance between the vicinity of the center of the linear cathode and both ends, or a direction in which these potential gradients are eliminated, and a flat luminance can be obtained. .

In this embodiment, the luminance correction signal is applied to the reference voltage (upper limit) and the video primary color signal is indirectly amplitude-modulated. However, the luminance correction signals having the same amplitude and different DC levels are applied to the upper and lower limits of the reference voltage. By using this, it is also possible to perform black level modulation.

In the above, the case of correcting the luminance of the horizontal synchronizing signal has been described. However, the correction of the vertical synchronizing signal or the case of correcting the horizontal and vertical synchronizing signals simultaneously can be performed in substantially the same manner.

(Effects of the Invention) As described above, according to the present invention, video primary color signals corresponding to dark portions of the entire screen, that is, upper, lower, left, and right edges of the screen, and upper and lower ends of each section in the vertical direction are input. By narrowing the width of the reference voltage of the A / D converter at that time, the video primary color signal is indirectly amplified, and uniform brightness is obtained over the entire screen without affecting the deflection sensitivity or beam diameter. be able to.

In addition, the present invention is also applicable to the case where the coating thickness of the phosphor applied on the screen is different on the left and right due to mechanical accuracy, and the like, by modulating the signal with the sawtooth waveform by the above method, so that the entire screen is uniform. Brightness can be obtained.

Further, according to the present invention, since the modulation of the video primary color signal can be performed indirectly, a great effect can be easily obtained without destroying the characteristics of the original signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) and 1 (b) are a configuration diagram of a luminance correction circuit of an image display device and a schematic diagram of an input waveform thereof according to an embodiment of the present invention, and FIG. Specific circuit diagram of correction circuit, third
2 (a) to 2 (g) are waveform diagrams for explaining the operation of FIG. 2, FIG. 4 is an exploded perspective view of an image display element used in a conventional image display device, and FIG. FIGS. 6 (a) and 6 (b) are an enlarged view of the fluorescent screen of the display element, FIGS. 6 (a) and 6 (b) are a block diagram and an operation waveform diagram showing a basic configuration of a drive circuit of the same image display element, and FIG. FIG. 8 is a waveform diagram for explaining the operation of the linear cathode drive circuit, FIG. 9 is a waveform diagram of each drive signal, and FIG. 10 is an explanation of the operation of the horizontal deflection drive circuit. FIG. 1 ... Back electrode, 2,2a ~ 2o ... Line cathode, 3,3 '... Vertical focusing electrode, 4 ... Vertical deflection electrode, 5 ... Beam flow control electrode, 7 ... Horizontal deflection electrode, 9 ... ... Screen, 10 ... Slit, 20 ... Phosphor, 23 ... Composite video signal input terminal,
30: color demodulation circuit, 50: luminance correction signal input terminal, 51A
.About.51C, 61... AD converter, 60... Flip-flop.

Claims (2)

(57) [Claims] 1. A screen coated with a phosphor that emits light by being irradiated with an electron beam, an electron beam source for each of a plurality of vertical divisions of the screen on the screen, Separating means for separating the electron beam generated by the beam source into a plurality of horizontal sections obtained by dividing the screen on the screen into a plurality of sections in the horizontal direction and irradiating the screen with the electron beam; and A deflection electrode that deflects in a plurality of stages in the vertical and horizontal directions, and controls the amount of irradiation of the screen with the electron beam separated for each horizontal direction to control the light emission amount of each picture element on the screen of the screen. A beam flow control electrode for controlling, a focusing electrode for controlling a light emission size on the phosphor surface by an electron beam in each picture element, and an electron beam amount from the electron beam source. In an image display device having a back electrode for controlling the electron beam to the screen and an accelerating electrode for irradiating the electron beam to the screen, an analog-digital conversion of video primary color signals (R, G, B signals) for driving the beam flow control electrode is performed. An analog-to-digital converter is provided which has a waveform similar to the luminance distribution of the screen when a uniform signal is applied to the entire surface of the reference voltage of the analog-to-digital converter. An image display device wherein the luminance and the hue of an image reproduced on the screen surface can be arbitrarily varied by using a luminance correction signal repeated for each section. 2. The luminance correction signal is generated by blunting a sine wave obtained from a synchronization signal, and the center of the signal waveform is substantially flat, and both ends have lower output than the center. The image display device according to claim 1, wherein: