JP2822664B2 - White balance adjustment method for image display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube for displaying an image by irradiating a phosphor with electrons generated at a cathode in a vacuum vessel, and more particularly to a cathode ray tube having a large electron density. The present invention relates to an image display device used.

2. Description of the Related Art A basic structure of a conventional image display device will be described with reference to FIG.

This display element consists of a back electrode 1, a line cathode 2 as a beam source, and a beam extraction electrode in order from the rear to the anode side.
3, a beam flow control electrode 4, a focusing electrode 5, a horizontal deflection electrode 6, a vertical deflection electrode 7, a screen plate 8, and the like are arranged, and these are housed in a vacuum vessel.

The linear cathode 2 as a beam source is stretched in the horizontal direction so as to generate an electron beam distributed linearly in the horizontal direction, and a plurality of linear cathodes 2 are arranged at intervals in the vertical direction (2 to 2 in this description). (Only two of them are shown). In this configuration, the distance between the line cathodes is 3 mm, and the number of the line cathodes is 30. The distance between the line cathodes cannot be freely increased, and is regulated by the distance between a vertical deflection electrode 7 and a screen 8 described later. The configuration of these linear cathodes 2 is 10 to
An oxide cathode material is applied to the surface of a 30 μmφ tungsten rod. As described later, the line cathode is controlled so as to emit an electron beam from the upper line cathode 2a to the lower 2 cathodes in order for a predetermined time. The back electrode 1 not only suppresses the generation of electron beams from the line cathodes other than the corresponding line cathode, but also pushes out the electron beams only in the anode direction. Although the vacuum vessel is not shown in FIG. 3,
It is also possible to adopt a structure in which the back electrode 1 is integrated with the vacuum vessel. The beam extraction electrode 3 is a conductive plate 11 having a plurality of through-holes 10 provided at predetermined intervals in the horizontal direction facing each of the linear cathodes 2a and 2b,
The electron beam emitted from the linear cathode 2 is extracted through the through hole 10. Next, the control electrode 4 is constituted by a vertically long conductive plate 15 having a through hole 14 at a position facing each of the linear cathodes 2a to 2b, and a plurality of the control electrodes 4 are juxtaposed in a horizontal direction at a predetermined interval. Have been. In this configuration, 120 control electrode conductive plates 15a to 15n are provided (only eight are shown in FIG. 3). The control electrode 4 controls the amount of passage of each of the electron beams divided in the horizontal direction by the beam extraction electrode 3 in accordance with the picture element of the video signal and in synchronization with the later-described horizontal deflection timing. .
The focusing electrode 5 focuses an electron beam on a conductive plate 17 having a through hole 16 at a position facing each through hole 14 provided in the control electrode 4.

A plurality of horizontal deflection electrodes 6 are provided on each of the conductive plates vertically arranged along both sides of the through hole 16 in the horizontal direction.
The horizontal deflection voltage is applied to each conductive plate. The electron beam for each picture element is deflected in the horizontal direction, and R, G,
Each phosphor B is sequentially irradiated to emit light. In this configuration, each electron beam is deflected by two trios. The vertical deflection electrode 7 is composed of a plurality of conductive plates 19 and 19 ′ arranged in the horizontal direction at intermediate positions in the vertical direction of the through-holes 16, respectively. Deflected vertically. In this configuration, a pair of electrodes 1
The electron beam generated from one linear cathode is deflected by 8 lines in the vertical direction by 9, 19 '. Then, 30 vertical deflection conductor pairs corresponding to each of the 30 line cathodes are constituted by the 31 vertical deflection electrodes 7 and 240 horizontal scanning lines are drawn on the screen 8 in the vertical direction. ing.

As described above, in the present configuration, a plurality of horizontal deflection electrodes 6 and a plurality of vertical deflection electrodes 7 are arranged in a comb shape. Further, by setting the distance to the screen 8 longer than the distance between the horizontal and vertical deflection electrodes, the screen 8 can be irradiated with an electron beam with a small deflection amount. Thereby, horizontal and vertical co-deflection distortion can be reduced.

As shown in FIG. 3, the screen 8 is formed by applying a phosphor 20 on the back surface of a glass plate 21 in a stripe shape.
Although not shown, an aluminum layer is also applied. The phosphor 20 deflects the electron beam passing through one through-hole 14 of the control electrode 4 in the horizontal direction, thereby forming three R, G, and B electrodes.
The color phosphor pairs are provided so as to irradiate two trios, and are applied in the form of stripes in the vertical direction.

In FIG. 3, broken lines drawn on the screen 8 indicate vertical divisions displayed corresponding to the plurality of line cathodes 2, and two-dot chain lines correspond to each of the plurality of control electrodes 4. Indicates the horizontal division to be displayed. FIG. 4 shows an enlarged view of one section separated by a broken line and a two-dot chain line. As shown in FIG. 4, the phosphor has R, G, B phosphors for two trios in the horizontal direction and a width for eight lines in the vertical direction. 1
The size of the section is 1 mm in the horizontal direction and 3 mm in the vertical direction in this example.

In FIG. 4, the phosphors of the three colors R, G, and B are shown in a stripe shape, but may be arranged in a delta shape. However, when they are arranged in a delta shape, it is necessary to apply a horizontal deflection and vertical deflection waveform suitable for the delta shape.

In FIG. 4, the vertical and horizontal dimensional ratios for the sake of explanation are different from the image displayed on the actual screen. Further, in the present configuration, the R, G, and
The phosphor of B is provided for two trios, but may be composed of one trio or three or more trios. However, the control electrode 4 has one trio or three or more trio of R,
The G and B video signals are sequentially applied, and it is necessary to perform horizontal deflection in synchronization with them.

Next, the operation of the drive circuit for driving the display element will be described with reference to FIG. First, a driving portion for irradiating the screen 8 with an electron beam for display will be described.
The power supply circuit 22 is a circuit for applying a predetermined bias voltage to each electrode of the display element. V1 is applied to the back electrode 1, V3 is applied to the beam emitting electrode 3, V5 is applied to the focusing electrode 5, and V8 is applied to the screen 8.
Is applied. The line-cathode drive circuit 26 generates a line-cathode drive pulse (image) using the vertical synchronizing signal V and the horizontal synchronizing signal H. FIG. 6 shows the timing chart.
As shown in FIG. 5 (i-ma), each line cathode 2a-2ma
The current is heated by the current flowing while the drive pulse is at a high potential, and the heating state is maintained so that the drive pulse (i to m) emits electrons during the period of a low potential. As a result, electrons are emitted from the 30 line cathodes 2a to 2m only during the 8 horizontal scanning periods to which low-potential drive pulses (a to m) are applied. During the period in which the high potential is applied, the line cathode 2 is lower than the potential around the line electrode 2 determined by the bias voltage applied to the back electrode 1 and the beam extraction electrode 3.
It has been added to b. Since the potential is higher, no electrons are emitted from the linear cathode. In order to configure one screen, the potential may be switched from the upper line cathode 2a to the lower line cathode 2a in sequence for eight scanning periods.

Next, the deflection portion will be described. Deflection voltage generation circuit 40
Are a direct memory access controller 41 (hereinafter referred to as a DMA controller), a deflection voltage waveform storage memory 42 (hereinafter referred to as a deflection memory), a digital-analog converter 43h,
43v (hereinafter referred to as a D / A converter) and the like, and generates a vertical deflection signal v, v 'and a horizontal deflection signal h, h'.

In this configuration, the vertical deflection signal is displayed in one field for 240 horizontal scanning periods in consideration of overscan. Further, a memory address area storing vertical deflection position information corresponding to each line is divided into a first field and a second field, each having one set of memory capacity. When displaying, the data is read from the corresponding deflection memory 42, converted into an analog signal by the D / A converter 43v, and applied to the vertical deflection electrode 7. The vertical deflection position information stored in the deflection memory 42 is composed of substantially regular data every eight horizontal scanning periods, and the D / A-converted waveform becomes a vertical deflection signal of approximately eight stages. However, as described above, a memory capacity for two fields is provided, and the position can be finely adjusted for each horizontal scanning line.

In addition, for the horizontal deflection signal, it is necessary to horizontally deflect the electron beam in six stages during one horizontal scanning period, and a memory is provided so that the deflection position can be finely adjusted for each horizontal scanning. Therefore, to display 480 horizontal scanning periods in one frame, a memory of 480 × 6 = 2880 bytes is required.
Since the data of the first field and the data of the second field are shared, a memory of 1440 bytes is actually used. At the time of display, deflection information corresponding to each horizontal scanning line is read from the deflection memory 42, converted into an analog signal by a D / A converter 43v, and applied to the horizontal deflection electrode 6. In summary, during the display period excluding the vertical blanking period in the vertical period, the electron beam emitted from the line cathode applying a low-potential driving pulse among the line cathodes 2a to 2b is a beam. It is divided into 120 sections in the horizontal direction by the extraction electrode 3 to form a row of 120 electron beams. The electron beam is controlled by the control electrode 4 for each section as described later, and the amount of beam passage is controlled by the control electrode 4. After being converged by the converging electrode 5, the pair of horizontal beams change in approximately six steps as shown in FIG. Horizontal deflection electrodes 18, 18 'to which deflection signals h, h' are added.
Thus, phosphors such as R1, G1, B1 and R2, G2, B2 of the screen 8 are sequentially irradiated in each horizontal display period by a horizontal display period / 6. Thus, the raster of each horizontal line displays a color image on the screen 8 by modulating the electron beam by the video signals corresponding to R1, G1, B1 and R2, G2, B2 for each of the 120 sections. be able to.

Next, the modulation control portion of the electron beam will be described.
First, in FIG. 5, the R, G, and B video signals applied to the signal input terminals 23R, 23G, and 23B are applied to 120 sample-hold circuit groups, 31a to 31n. Each sample hold group 31a to 31n is for R1, G1, B1, and R2, G2
, And six sample-and-hold circuits for B2. The sampling pulse generation circuit 34 has a horizontal period (63.5
μs) during the horizontal display period (about 50 μs).
A set of sample and hold circuits 31a to 31n for R1, G1, B1
(120 × 6) sampling pulses Ra1 to Rn2 corresponding to the sample and hold circuits for R2, G2, and B2
Are sequentially generated. Each of the 720 sampling pulses is applied to 120 sample-hold circuit sets 31a to 31n, each of which has 6 samples, whereby each sample-hold circuit set has two lines when one line is divided into 120 lines.
Each video signal of picture elements R1, G1, B1, R2, G2, B2 is individually sampled and held. Sample held
The video signals of 120 sets of R1, G1, B1, R2, G2, B2 are simultaneously transferred to the 120 sets of memories 32a to 32n by the transfer pulse t after the sample and hold of one line is completed, where the next one horizontal scan is performed. Retained for a period. The held signal is applied to 120 switching circuits 35a to 35n. Switching circuit 35a
3535n are each constituted by a circuit having individual input terminals of R1, G1, B1, R2, G2, B2 and a common output terminal for sequentially switching and outputting them, and are added from the switching pulse generation circuit 36. Switching pulse r1, g1, b1, r
Switching control is simultaneously performed by 2, g2 and b2.

The switching pulses r1, g1, b1, r2, g2, b2 divide each horizontal display period into six, and switch the switching circuits 35a to 35n in units of a horizontal display period / 6, and R1, G1, B1, R2, G2, B2 Time-divisionally and sequentially output each video signal, and pulse width modulation circuit 37a
~ 37n.

The outputs of the switching circuits 35a to 35n are applied to 120 sets of pulse width modulation (hereinafter referred to as PWM) circuits 37a to 37n,
Pulse width modulation is performed according to the magnitude of each video signal of 1, G1, B1, R2, G2, and B2 and output. These pulse width modulation circuits 37a to 37n
Are individually applied as control signals for modulating the electron beam to the 120 conductive plates 15a to 15n of the control electrode 4 of the display element.

Next, the timing of horizontal deflection and display will be described. R1, G1, B1, R2, G in the switching circuits 35a to 35n
Synchronous control so that the switching timing of the switching of the video signals of 2 and B2 and the switching of the horizontal deflection of the electron beams R1, G1, B1, R2, G2, and B2 to the phosphors by the horizontal deflection drive circuit 41 completely match Have been. Thus, when the electron beam is irradiated on the R1 phosphor, the irradiation amount of the electron beam is R1
R1, G1, B1, R2, G2, B2 are controlled in the same manner, and R1, G1, B1, R2, G2, B
2 The light emission of each phosphor is controlled by the video signal of R1, G1, B1, R2, G2, B2 of the picture element, and each picture element is illuminated and displayed according to the input video signal .
This control is simultaneously executed for 120 sets of one line (two picture elements each), and a picture of 240 picture elements per line is displayed.
Further, the processing is sequentially performed from the upper line for 240 lines in one field, and an image is displayed on the screen 8. Further, the above operations are repeated for each field of the input video signal, and the television signal and the like are displayed on the screen 8.
Will be displayed.

The base clock required for this configuration is supplied from the pulse generation circuit 39 shown in FIG. 5, and the timing is controlled by the horizontal synchronizing signal H and the vertical synchronizing signal V.

However, in the above-described configuration, since the distance from the line cathode as a beam source to the anode is short, a large voltage cannot be applied to the anode. Get the brightness.

In this case, the deterioration of the phosphor is remarkable in proportion to the current density. In particular, since the degree of deterioration differs depending on the type of the phosphor, the white balance shifts and the reddish white increases as the cumulative image display time increases. Become.

The above problem will be described below with reference to the drawings.

FIG. 2 is a luminance temporal characteristic diagram of each of the RGB phosphors of the image display element. In the figure, the horizontal axis is the total video display time,
The vertical axis is the relative luminance. As shown in the figure, R (Y ₂ O ₂ S: E
u) shows less degradation of the phosphor than G (ZnS: Cu, Al) and B (ZnS: Ag). It becomes just white.

The present invention is intended to reduce the deviation of the white balance due to the deterioration of the phosphor.

Means for Solving the Problems In order to solve the above problems, the white balance adjusting method of the present invention is to adjust the white balance higher than the target color temperature by 1000 K or more at the beginning.

Function The present invention takes into account the deterioration of each of the RGB phosphors predicted in advance by the method described above, and the color temperature changes slightly even when the image is displayed for a long time while the color temperature is slightly high at the beginning. It is possible to realize an image display device capable of expressing beautiful images forever without feeling.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a chromaticity diagram showing the deviation of the white balance with respect to the total video display time. In the figure,
The mark ● is the change after 1000 hours and 10,000 hours when the white balance is adjusted to the target color temperature of 9500K, and the mark ○ is 1000 hours when the white balance is adjusted to 11000K which is 1500K higher than the above target. This is the change after 10,000 hours.

Now, Table 1 shows the chromaticity and luminance ratio of each of the RGB phosphors for obtaining the above white balance. From the luminance ratio of the above-mentioned phosphors, each of the RGB phosphors undergoes luminance degradation according to the luminance aging characteristic diagram shown in FIG. 2, and the color temperature changes as shown in FIG. If you normally target 9500K here, 7
000K is fairly reddish white, resulting in an overall blurred image. Therefore, 1500K than the target color temperature
If you make initial adjustments to a high 11000K, you can realize an image display device that can display beautiful images forever without feeling extreme color temperature changes even if you display images for a long time, although the color temperature is slightly high at the beginning. it can.

Effect of the Invention As described above, the present invention is to adjust the white balance higher than the target color temperature by 1000K or more initially,
Although the color temperature is slightly high at the beginning, even if an image is displayed for a long time, an image display device that can express a beautiful image forever without realizing an extreme change in color temperature can be realized.

[Brief description of the drawings]

FIG. 1 is a chromaticity diagram showing the shift of the white balance with respect to the total video display time, FIG. 2 is a luminance aging characteristic diagram of each of the RGB phosphors of the image display device using the white balance adjusting method of the present invention, and FIG. Is an exploded perspective view of the image display element, and FIG.
FIG. 5 is an enlarged front view of the screen, FIG. 5 is a circuit diagram of a driving circuit, and FIG. 6 is a waveform diagram of each part for explaining the operation of FIG. 2 ... line cathode, 3 ... beam extraction electrode, 4 ... beam flow control electrode, 5 ... focusing electrode, 6 ... horizontal deflection electrode, 7
... vertical deflection electrode, 8 ... screen plate, 20 ... phosphor, 21 ... glass plate.

Claims (1)

(57) [Claims] 1. A screen coated with a phosphor that emits light by being irradiated with an electron beam, and an electron beam that generates an electron beam for each vertical section obtained by vertically dividing the screen on the screen into a plurality of sections. A separating means for separating the electron beam generated by the electron beam source into horizontal sections which are divided in a horizontal direction and irradiating the screen with the electron beam, and a vertical direction until the electron beam reaches the screen. A deflection electrode for deflecting the screen in a plurality of stages in the horizontal direction; and a beam for controlling the amount of irradiation of the screen with the electron beam separated for each of the horizontal sections and controlling the light emission amount of each picture element on the screen of the screen. A flow control electrode; a focusing electrode that controls the size of light emission on the phosphor surface by an electron beam in each picture element; a back electrode that controls the amount of the electron beam; An image display device comprising: a beam extraction electrode for controlling the total amount of a beam;
A white balance adjustment method for an image display device, characterized in that the white balance is initially adjusted to be 1000K or more higher than a target color temperature in an image display device of μA / cm ² or more.