JPS60191572A - Picture display device - Google Patents

Abstract

PURPOSE:To reproduce a white level with good quality by passing through an electron beam including a guard band part when a white peak part of a video signal is displayed. CONSTITUTION:An electron beam is shut off tmporarily by providing a guard band of a width PW1 between R, G, B signals in the output of a pulse width modulation (PWM) circuit in general during the period. Since the PWM output width takes a maximum value PW2 all R, G, B outputs when a display output is at white peak, no guard band is required in this case. Then the passing of the electron beam is increased and the luminance of a white peak display part is increased by bringing the level to the H level also during the period of PW1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention generates an electron beam for each division when the screen L is divided into a plurality of divisions in the vertical direction, 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 to display a television image as a whole.

Conventional configurations and their problems Traditionally, cathode ray tubes have been mainly used as display elements for displaying color television images, but conventional cathode ray tubes have a very long depth compared to the screen size. It has been impossible to create thin television receivers. In addition, although EL display elements, plasma display devices, liquid crystal display elements, etc. have recently been developed as flat display elements, all of them are insufficient in terms of performance such as brightness, contrast, and color display, so they cannot be put into practical use. The one person who is expected to do so has not yet reached it.

Therefore, in order to achieve a flat display device using electron beams, the present applicant proposed a new display device in Japanese Patent Application No. 56-20618 (Japanese Unexamined Patent Publication No. 57-185590).

In this method, when the screen t is vertically divided into multiple sections, an electron beam is generated for each section, and each electron beam is deflected vertically for each section to display multiple lines. , which 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 panel consists of, in order from the back to the front: a back electrode (1), a line cathode (2) as a beam source, a vertical focusing electrode (3) (8'), a vertical deflection electrode (4), Beam flow control electrode (5), horizontal focusing electrode (6), horizontal deflection electrode (7), beam acceleration electrode (8)
) and a screen plate (9), which are housed in the evacuated interior of a flat glass bulb (not shown). The line cathode (2) as a beam source is stretched horizontally so as to generate an electron beam distributed in a horizontal direction. multiple books (in the figure)
Only four of them (2a) to (2d) are shown) are provided. In this embodiment, it is assumed that 15 pieces are provided.

Let them be (2a) to (2o). These line cathodes (
2) is constructed by coating the surface of a tungsten wire with a thickness of 10 to 20 .mu.y with an oxide cathode material for emitting heat particles. And these line cathodes (2a) to (2o)
When a current is passed through the electrode, it generates a thermal electron beam and is heated up, and as described later, the electron beam is controlled to be emitted sequentially from the line cathode (2a) for a certain period of time. be done. The back electrode (1) suppresses the generation of electron beams from line cathodes other than the line cathode that is controlled to emit the electron beam for a certain period of time, and also directs the generated electron beam only once in the forward direction. It has the effect of pushing out toward the target.

This back electrode (1) may be formed by a coating of electrically conductive material applied to the inner surface of the rear wall of the glass bulb.

Further, a planar electron beam emitting cathode may be used to replace the back electrode (1) and the line cathode (2).

The vertical focusing electrode (3) is a conductive plate αυ having a horizontally long slit QO facing each of the line cathodes (2a) to (20), and directs the electron beam emitted from the line cathode (2) through the slit. (The electron beam is taken out through II and focused in the vertical direction. One horizontal line worth of electron beams (360 picture elements) is taken out at the same time. The figure shows only one horizontal section of the electron beam. The slit C1O may be provided with crosspieces at appropriate intervals in the middle, or may be a row of through holes arranged horizontally at small intervals (nearly touching each other). It may be composed of a slit and a vertical focusing electrode (
8') is also similar.

A plurality of vertical deflection electrodes (4) are arranged horizontally in the middle of each of the L slits Q1, and conductors Q, 3 (1
8'). Then, a vertical deflection voltage is applied between the opposing conductors α:1 (18') to deflect the electron beam in the vertical direction. In this embodiment, the electron beam from one line cathode (2) is vertically deflected to positions corresponding to 16 lines by a pair of conductors (Qa'). and 16 vertical deflection electrodes (
4) 1 Thus, 15 pairs of conductors corresponding to each pair of 15 line cathodes (2) are constructed, and the electron beam is eventually deflected to draw 240 horizontal lines on the screen (9). .

Next, the control electrodes (5) are composed of conductive plates (6) each forming a long slit QJ in the vertical direction, and a plurality of control electrodes (5) are arranged in parallel in the horizontal direction at predetermined intervals. In this example, 180 control electrode conductive plates (15-1) to
(15-n) (only nine are shown in the figure). Each of the control electrodes (5) divides the electron beam into two picture elements in the horizontal direction and takes out the electron beam, and controls the path of the electron beam in accordance with a video signal for displaying each picture element. Therefore, the conductive plate (15) for the control electrode (5)
-1) to (15-n) are provided, 860 picture elements can be displayed for one horizontal line. In addition, in order to display images in color, each picture element is displayed with 8-color phosphors of R, G, and B, and each control electrode (5) has two picture elements of R, G, and Each video signal of B is added sequentially.

In addition, a conductive plate (15-1) for 180 d control electrodes (5)
~(15-n) each has 180 pairs for one line (
Two picture elements per set of video signals are applied at the same time, and one line of video is displayed at one time.

The horizontal focusing electrode (6) is composed of a conductive plate (17) having a plurality of vertically elongated (180) long slits facing the slit α of the control electrode (5). The electron beams for each picture element thus produced are focused in the horizontal direction to form a narrow beam.

The horizontal deflection dragon (+i (7)) is composed of a plurality of conductive plates 01 (18') arranged vertically on both sides of the slit 0119, and each electrode (g) (18' ) A six-step horizontal deflection voltage is applied to horizontally deflect the electron beam for each picture element, and sequentially illuminate two sets of R, G, and B phosphors on the screen (9). The deflection range is the width of two picture elements for each electron beam in this embodiment.

The accelerating electrode (8) consists of a plurality of conductive plates (10) placed horizontally in the same position as the vertical deflection electrode (4), and screens (9) the electron beam with sufficient energy. Accelerate by 1 so that it collides with

The screen (9) is constructed by coating the back surface of a glass plate eυ with a phosphor emitted by electron beam irradiation 1, and adding a metal back layer (not shown). The phosphor (7) has three colors of R, G, and H phosphors for one slit α◆ of the control electrode (5), that is, for each one electron beam divided in the horizontal direction. 2
They are provided in pairs and coated in stripes in the vertical direction. In FIG. 1, the broken lines drawn on the screen (9) indicate vertical divisions displayed corresponding to the plurality of line cathodes (2), and the two-dot chain lines indicate the divisions in the vertical direction that are displayed corresponding to the plurality of line cathodes (2). ) indicates the corresponding horizontal division.

As shown in the enlarged view in Figure 2, one section partitioned by these two has I, R, G, and B pixels for two picture elements in the horizontal direction.
phosphor (7), and has a width of 16 lines in the vertical direction. The size of one compartment is, for example, 1 gate in the horizontal direction and 9 gates in the vertical direction.

Note that in FIG. 1 I, the length in the horizontal direction is drawn much larger than the length in the direction f of the frame m for the sake of clarity.

In addition, in this embodiment, one control electrode (5), i.e. one
For the electron beam of the book, R, G, B phosphors (7) are 2
Only one pair for each picture element is provided, but of course, it is also possible to provide one picture element or more than 8 picture elements. R, G, and B video signals for t are sequentially applied, and horizontal deflection is performed in synchronization with them.

Next, the basic configuration and waveforms of each part of the drive circuit for displaying television images on this display element 1 will be explained with reference to FIG. 8. First, the driving part for irradiating the screen (9) with an electron beam to emit raster light will be explained.

The power supply circuit (A) has one predetermined via for each electrode of the display element, V for the horizontal focusing electrode (6), and V8 for the I acceleration electrode (8).
- Apply a DC voltage of V to the screen (9).

Next, a composite video signal of the Ten Vision signal is added to the input terminal LA1, and a vertical synchronization signal V is applied to the synchronization separation circuit (c).
and the horizontal synchronizing signal H are separated and extracted.

The vertical deflection drive circuit θQ includes a vertical deflection counter (c),
It is composed of a memory (5) for storing vertical deflection signals, and a digital-to-analog converter (hereinafter referred to as a DA converter). As input pulses to the vertical deflection drive circuit (to), a vertical synchronizing signal V and a horizontal synchronizing signal H shown in Figure 4 are used. The vertical deflection counter (c) (8 bits) is reset by the vertical synchronizing signal V and counts the horizontal synchronizing signal H. This vertical deflection counter (2) counts the effective scanning period (in this case, a period of 240H) excluding the vertical blanking period of the vertical period, and this count output is supplied to the memory address. be done. memory(
(b) to vertical deflection signal data (
Here, 10 bits) are output, and the D-A converter (to)
Then, it is converted into a vertical deflection signal of v, t+' shown in FIG. 4 (FIG. 3(b)D). In this circuit, the memory address for storing the vertical deflection signal corresponding to each line for 240H is stored in memory, and regular data is stored in the memory every 16H. can be obtained.

On the other hand, the line cathode drive circuit (c) uses the vertical synchronization signal ■ and the output of the vertical deflection counter (c) to generate the line cathode drive pulse a.
-Create o. FIG. 5(a) shows the relationship among the vertical synchronizing signal (2), the horizontal synchronizing signal (H), and the lower six bits of the vertical deflection counter (c). FIG. 5(b) shows a method of creating line cathode drive pulses a' to 0' for each 16E (16E) using each of these signals. In FIG. 6, L and SB indicate the lowest pits,
(LSB+1) means the third bit one bit above the LSB. , the first line cathode drive pulse a' is a vertically synchronized other-phase ■
It can be created with an R-S flip-flop U etc. using the output (LSB+4) of the direct deflection counter (c), and by transferring the line cathode drive pulses b' to 0' as a clock. 1, this drive pulse a'~0' is inverted and is brought to a low potential only during each pulse period, and during the other periods 1, a line cathode separation pulse a-0' is brought to a high potential of about 20 volts. o (Fig. 3(b) E
), are added to each line cathode (2a) to (2o). .

Each line cathode (2a) to (20) is heated by a current flowing through it during the high potential period of the driving pulses a to 0, and is heated as if emitting electrons during the low potential period of the driving pulse a to 0. State is preserved. As a result, 15 wire cathodes (2a)
From ~(2o), drive pulses a~ with i low potential are respectively
During the 16H period I in which 0 is added, electrons are emitted.

During the period 1 during which a high potential is applied, the potential at the line cathode (2) is lower than the potential at the position of the line cathode (2), which is determined by the bias voltage applied to the line cathode (1) and the vertical focusing electrode (3). When the high potential applied to (2a) to (20) becomes positive, the wire cathodes (2a) to (20)
No electrons are emitted from. Thus, in the line cathode (2), during the effective vertical scanning period IFtl, 1
61 (Electrons are emitted for each period. The emitted electrons are pushed forward from the back electrode (1), pass through the opposing slit aCt of the vertical focusing electrode (3), and are focused in the vertical direction. As a result, it becomes a flat electron beam.

Next, line cathode drive pulses a~0 and vertical deflection signals υ, υ′
The relationship between the two will be explained using FIG. The vertical deflection signals υ, υ' are each line cathode pulse a-.

During the 1.6H period, the IH changes in steps of 16. The vertical deflection signals V and υ' both have a center voltage of v4, and are configured to change in opposite directions so that υ increases sequentially and υ' sequentially decreases. These vertical deflection signals υ and 2' are respectively added to 04 and (13') of the vertical deflection type V8i (4),
As a result, the electron beams generated from each line cathode (2a) to (20) are vertically deflected in 16 steps, and as mentioned above, one electron beam is The beam is deflected by one point so that 16 lines of rasku are drawn one line at a time starting from L.

Result on V, 15 line negative iis (2a)-(2o)
Electron beams are emitted sequentially for 1614 periods starting from the top, and each electron beam is deflected one line from top to bottom within 15 sections in the vertical direction. h&ia
(Sequentially 1 from the 1st line D to the 240th line at the bottom)
The electron beam is vertically deflected line by line, and a total of 240 raster lines are drawn.

The electron beam vertically deflected in this way is directed to the control electrode (5
) and horizontal focusing electrode (6).
It is divided into 80 sections and taken out. Figure 1 shows one of these categories. The degree of passage of this electron beam is controlled by a control electrode (5) for each section, and the horizontal focusing electrode (6) focuses the electron beam into a single thin electron beam. The screen is deflected horizontally in six steps by the deflection means (
9) The combined R, G, and B light body (4) for two picture elements of 7 is sequentially irradiated. FIG. 2 shows the vertical and horizontal divisions. Control g Each of the poles (5) (15-1) - (x5
-n) corresponds to R2G and B for two picture elements, but for convenience of explanation 41. Let one picture element be R1, G4 + B1 and the other picture element R2*G2 + Bl.

Next, the horizontal deflection drive circuit θ1) is composed of a horizontal deflection counter @ (11 bits), a memory C4 storing a horizontal synchronizing signal, and a DA conversion type can. As shown in FIG. 7, the input pulses of the horizontal deflection drive circuit (b) are pulses 6H synchronized with the vertical synchronizing signal V and the horizontal synchronizing signal 1, and having a repeating frequency six times that of the horizontal synchronizing signal H. The horizontal deflection counter (to) is reset by the vertical synchronizing signal VIζ and counts the horizontal 6 times pulse 6H.This horizontal deflection counter (to) counts 6 times during IH and 240'X during IV. 6/H = i440 counts, and this count output is supplied to the address of the memory wire.The horizontal deflection signal data (
Here, 8 bits) are output and sent to D, -A conversion 83)
Then, it is converted into a horizontal deflection signal as shown in FIG. 7 (FIG. 8(b) C). In this circuit 6
There is a memory address for storing one horizontal deflection signal corresponding to each of 240 lines, and by storing six pieces of regular data for each line in the memory, horizontal deflection of 6 step waves during the IH off period can be achieved. I can get a signal.

These horizontal deflection signals are a pair of horizontal deflection signals ri and h' that change from 1 to 6 steps as shown in FIG. They change in opposite directions as they increase. These horizontal deflection signals h' are applied to electrodes (2) and (18') of the horizontal deflection electrode (7), respectively. As a result, each horizontally segmented electron beam has one screen (9) R, G, B, R, G, B (R
t.

G1. B1. R2, G2. B2) phosphor was sequentially coated with [(/
It is horizontally deflected so that 6 rays are irradiated. Thus, in each line of Rask 1, the electron beam is divided into R1, Gl, Bt * R2, G for each of the 180 sections in the horizontal direction.
2 + each phosphor of B2 - is sequentially irradiated.

Therefore, for each horizontal section of each line, one electron beam is
, Gt , Bl , R2 , G2 , and B2 are used to modulate the video signals 1 and 7 of the screen (9).
11 that can display color television images
Next, the electron beam modulation control section 1 will be explained. First, the composite video signal applied to the television signal input terminal (c) is applied to the color demodulation circuit (I), where the R-Y and B-Y color difference signals are demodulated, and the G-Y color difference signal is demodulated. The signals are matrix-synthesized, and then they are combined into luminance signals@
Synthesized with Y, R, G.

B primary color signals (hereinafter referred to as R, G, and B video signals) are output. These R, G, and B video signals are applied to 180 sets of sample and hold circuits (81-1) to (81-n). Each sample hold circuit (81-1・) ~
(81-n) are for R1, Gl, Bl, R
It has six sample and hold circuits for G2, G2, and B2. These sample and hold outputs are respectively added to holding memories (82-1) to (82-n).

On the other hand, the reference clock oscillator (2) is composed of a PLL (phase-locked loop) circuit or the like, and in this embodiment, the reference clock 6f is six times as large as the color subcarrier fsc.
A reference clock 2fsc'e, which is twice as much as the reference clock 2fsc'e, is generated. The reference clock is controlled to always have a constant phase with respect to the horizontal synchronization signal [(1).

Reference clock 2 fsc is the deflection pulse generation circuit (9)
A signal 6H which is 6 times the horizontal synchronization (notation f) and a signal switching pulse for each stone r11gl t 1)l +
A pulse of r21 R2' B2 (FIG. 8 (1)) B) is obtained. On the other hand, the reference clock 6 fsc is applied to the sampling pulse generation circuit (b), where it is transferred to a shift register and delayed by one clock period, so that the effective horizontal scanning within the horizontal period (63.5 μsec) is applied. 1080 sampling pulses R1□, GII*BB, eRI3 during the period (approximately 50.7<5ec)
+ Gl2 r B12 ・R2+ + G21 *
B21 * R22+ G22 + B22-Rn1
:GnIBnl, Rn2 * Gn2, Rn2
(Fig. 8(b) A) is generated sequentially, and in the vicinity of this, a reverse pulse t is generated At1, and this sampling pulse R11Rn2 corresponds to 860 picture elements in the horizontal direction for one line of the image to be displayed.) One picture element corresponds to each divided picture element, and its position is controlled so that it is always constant with respect to the horizontal synchronizing signal H.

Each of these 1080 sampling pulses R11 to Bnz is connected to 180 sets of sample hold circuits (81-1).
~(81-n) are added 6 times, and as a result, each sample hold circuit (81-1) ~(at-n) has 1
When the line is divided into 180 lines, the video signals of Rt, Gt, Bt, R2, G2*B2 for each two picture elements are individually sampled and held. The sample held 180 pairs of R1, Gl, B1
．． The video signals of R2, G2 and B2 are stored in 180 sets of memories (82-1) to (
82-n), one transfer pulse t1 is transferred all at once and held here for the next horizontal period. This retained R4 + G1. B1*R2G2. The signal B2 is applied to switching circuits (85-1) to (85-11). Switching circuits (85-1) to (85-n
) are respectively R4, Gle Bl r R2r G2
, B2, and a common output terminal for sequentially switching and outputting these input terminals.

The output of each switching circuit W5 (85-1) (85-n) is the output of 180 sets of pulse width modulation (PWM) circuits (87-1).
) to (B7-n), and here, the reference pulse signal is pulse width modulated and output according to the magnitude of the sampled and held R1゜G+, B+, R2, G2, B2 low signal. Ru.

The repeating period of the reference pulse signal is the signal switching pulse rH+ g(t bHr r2 * B2 r B
It is desirable that the pulse width of 2 is also sufficiently small, and for example, a pulse width of about 1:10 to 1:100 is used.

The outputs of the pulse width modulation circuits (87-1) to (87-n) are used as control signals for modulating the electron beam to the 180 conductive plates (15-1) to the control electrode (5) of the display element.
(15-n) respectively. Each switching circuit (85-1) to (85-n) receives a switching pulse r1*gIrbN, r2+B2. Switching is controlled simultaneously by B2.

The switching pulse generation circuit is the signal switching pulse rl9gl, bl from the deflection pulse generation circuit (b) described above.

r2 , B2 r B21 is controlled by υ,
Divide each horizontal period into 6 and switch the switching circuits (85-1) to (B5-n) by 1(/6), R1r Gl
mB1+R2* G2, B2 video signals are time-divided and sequentially outputted to the pulse width modulation circuits (1-1) to (8).
7-n), the switching signal r1+g1・b!・
What should be noted here is that Rt, G+, B+, R2, G2 + B in the switching circuit (85-1)-(85-n) t.
2 video signal supply switching and horizontal deflection drive circuit θ01
Soaring electron beam R1・G1・, Bl, R2*G2
- The horizontal deflection for switching the irradiation to the phosphor of B2 is synchronously controlled so that it completely matches both the timing 1 and the order. As a result, when the electron beam is irradiating the R1 phosphor, the irradiation claw of the electron beam is controlled by the R1 image signal, and the Gl, Gl,
Bl lR21G21B2 is similarly controlled, and R1*G1*Bl, R2+G2 of each picture element
+ B2 The light emission of each polymer is the R of that picture element, Gt *
Each picture element is controlled by the video signals Bt, R2, G2, and B2, respectively, and is displayed by emitting light according to the input video signal I. Such control is performed simultaneously for 180 sets (2 picture elements each) for one line, and an image of 860 picture elements for one line is displayed, and an additional 24 picture elements are displayed.
This is done sequentially from the t-side line on the 0 minute line,
The screen (9) becomes a screen on which one image is displayed.

Then, the following operations are performed on the input television colored one.
Each field is returned, and as a result, the television image of the moving image is displayed on the 1st screen (9), similar to the A% television reception.

By the way, in the image display device 1 described below, the brightness displayed on the screen L is controlled by the pulse width applied to the control electrode (5), and since the maximum pulse width is finite, the average brightness part When attempting to improve the gradation of the image, the white peak portion of the image was limited, and there was a problem in that the contrast between the white and the white was often impaired compared to that of an energized cathode ray tube.

OBJECTS OF THE INVENTION The present invention eliminates such conventional drawbacks, and at the time of the white peak of the video signal, the passing path of the electron beam FtPl is changed to the left again within the time period for which the pulse width modulation is applied.

An object of the present invention is to provide an image display device capable of reproducing high-quality white by reducing the brightness of a white peak part.

Structure of the Invention In general, when controlling a multiplex beam using PWM as shown in FIG. In contrast, the image display device according to the present invention uses a guard band for a certain period of time between outputs to temporarily block the electron beam during this period, when the brightness level of the video signal is near the white peak.

Focusing on the point that the R, G, and B signal outputs all pass the electron beam during the entire pulse width modulation period of +1'LI, when the video signal is close to the white peak, it becomes even more intense. The guard band also allows the electron beam to pass through it, and as a result, the brightness of the white beak of Shingetsu Aki is increased. .

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 8th
The figure shows a specific example of the circuit, and FIG. 9 is a waveform diagram for explaining its operation. In FIG. 81, the same parts as in FIG. 3 are numbered the same. In Figure 8 (
Figure 3) is a circuit for increasing the brightness when a white peak is displayed according to the present invention, which is newly added to the drive circuit shown in Fig. 3. The white peak part with high level is sliced.
), there is a white peak signal at the very beginning of the nH-th video signal, and when this is sliced at the level indicated by the dashed-dotted line, a pulse like the one shown in Figure 9(b) is obtained as the output of the white peak detection circuit. It will be done. The white peak detection circuit can be easily constructed using a differential amplifier or the like that uses a slice level voltage as one input voltage. White peak detection circuit (
The output pulse of (b) is an AND gate (45-11) (45
-12) (45-21) (45-22) ~ (45-
nl) (45-n2) and output from the sampling pulse generation circuit (c) G1+ -G12 + G
21- sampled at G22~Gnl + Ga4. In FIG. 9(a), it is assumed that the white peak signal is at the very beginning of the video signal, so the sampling pulse Gl
sampled at l. FIG. 9(C) is the sampling pulse Gll, and FIG. 9(d) is the output pulse of the AND gate (45-1). AND gate (45
The outputs of -11) to (45-h2) are input to mono-multivibrators (46-11) to (46-n2) and converted into pulses with a width of approximately IHI. In Figure 9, A
Since there is an output (d) of the ND gate (45-11), a pulse as shown in FIG. 9(e) can be obtained as the output of the monomulti-by-break (46-11). The outputs of the mono multivibrators (46-11) to (4,6-n2) are latched by D latches (47-11) to (47-n2) using the horizontal output pulses of the synchronous separation circuit (c) as sampling pulses. FIG. 9(f) shows a +lI horizontal sampling pulse, in which the horizontal output pulse of the synchronization separation circuit Q4 is inverted by an inverter (g) and used. In Figure 9, the output of the mono multivibrator (46-11) is
The pulse is latched during the H period and a pulse as shown in FIG. 9(g) is obtained as the output of the D latch (47-11). Figure 9(h)C
i) is the OR of rl+g1 y bl in Figure 8, respectively.
ORL, output and r2 +g2+ b
This is the output obtained by ORLing l with the OR gate (7). Then, depending on the output lζ of the D latch (47-11) to (47-n2), (h) or (i) is connected to the AND gate (51
-11) ~ (51-r12) and their outputs are OR gates (52-11) - (52-n2)
The respective outputs are further connected to a PWM circuit (37
-1) (87-n) output and OR gate (58-1) ~
(58-n) is ORed. Its output is 1゛00 to modulate the electron beam, and the control electrode of the display element (5
) are individually applied to the 180 conductive plates (15-1) to (15-n). By the way, generally, the output of the PWM circuit (87-1) (87-n) is provided with a guard band with a width of 1 P W 1 for each R, G, and B signal output amount, as shown in FIG. 9 (j). During this period, the electron beam is temporarily cut off to absorb the transient response when the R, G, and B signals are switched, and the correct PW2 is obtained, so the L guard band is not really necessary at this time. Therefore, if the PWl period is also set to the "H" level, the amount of electron beam passing through will increase accordingly, and the brightness of the white peak display area will increase.

Therefore, the output of the OR gate (58-1) is as shown in FIG. 9(k), and for the period W, as shown in FIG. 9(h) and (
The OR of j), that is, the pulse of FIG. 9(h) is output. The brightness is increased for a period corresponding to eight PWI periods.

In Fig. 89, it is assumed that the white peak signal is at the very beginning of the video signal, so Ru*G11. of the phosphor corresponding to the electrode (15-1). Electron beam irradiation Q'm to Bn.

has increased, but the location of the white peak has also increased (15
It is clear from the above explanation that any one of the electrodes -1) to (15-n) can be selected to increase the white peak brightness of that part.

According to the present invention, when the white peak portion of the video signal is displayed, the electron beam is passed through the guard band portion as well, so that the brightness increase is not required compared to the conventional method. can. This leads to the reproduction of a more natural white in terms of the quality of the displayed image.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of an image display element used in an image display device according to one embodiment of the present invention, FIG. 2 is an enlarged view of the phosphor screen of the image expansion display element, and FIG. A block diagram of a drive circuit devised prior to the present invention and waveform diagrams of each part, Figures 4 and 5, @6
FIG. 7 is a detailed waveform diagram of each part for explaining the operation of the drive circuit, FIG. 8 is a block diagram showing a specific circuit example of an image display device according to an embodiment of the present invention, and FIG.
The figure is a waveform diagram for explaining the operation. (2) (2a) to (2o)... line cathode, (4)...
・Vertical deflection electrode, (5)...Beam flow control electrode, (7
)...Horizontal deflection electrode, (9)...Screen plate, 4...
...Slit, (4)...Phosphor, (2)...Power supply circuit, (C)...Synchronization separation circuit, (C)...Vertical deflection counter, (C)...Line 1f J pole drive Drive, ψ)...
Memory, (2)...Horizontal deflection counter, (4)...Memory, (7)...Color demodulation circuit, (81-1)-C81
-n)-sample hold circuit, (,92-1) to (8
2-n)...Memory, So...Reference clock oscillator, ■-...Sampling pulse generation circuit, (85-1
) ~ (85-n)...Switching circuit, (a)...
・Switching pulse generation circuit, (87-1) (87-
n) -PWM circuit, M -D/A converter, Zeng...D
/A degree converter, to)...vertical, deflection drive circuit, G11)
...Horizontal deflection drive circuit, (6)...Deflection pulse generation circuit, (2)...White peak brightness up circuit, ■...
White peak detection circuit, (46-11) to (46-n2)・
・Mono multi-bi break, (47-11) ~ (4?
-n2) -D latch circuit. Agent Yoshihiro Morimoto Figure 2 E-tra direction 19 minutes Figure 3 (b) A B c 1) Figure 4 +--11 L-. L.し-１１ 噸j L-col hi] ] J Fig. 5 (t2) Cb) e・; Fig. 7 Fig. 3

Claims (1)

[Claims] (1) The electron beam extracted from the electron beam source is blocked during a guard band period of a certain time, and the brightness level of the projection signal is controlled during periods other than the guard band. An image display device comprising a cathode ray tube and a circuit for controlling the guard band period to allow electron beams to pass through when the luminance level of a video signal approaches a white peak.