JP2553739B2 - Image display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to generate an electron beam for each section when a screen on a screen is divided into a plurality of sections in the vertical direction, and to generate an electron beam for each section. The present invention relates to an image display device that deflects a beam in a vertical direction to display a plurality of lines and displays an image as a whole.

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

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

A line cathode 2 as a beam source is stretched in the horizontal direction so as to generate an electron beam linearly distributed in the horizontal direction, and the line cathodes 2 are further arranged at intervals in the vertical direction. Only 7 of 2 g are shown.) Provided. In this configuration, the line cathode spacing is 3 mm and the number is 30.
The line cathodes are provided in the form of 2a to 2m. The distance between the line cathodes cannot be set freely, and is regulated by the distance between the vertical deflection electrode 7 and the screen 8 which will be described later. As the structure of these line cathodes 10,
An oxide wire cathode material is applied to the surface of a tungsten rod having a diameter of -30 μm. As will be described later, the above-mentioned line cathode is controlled so as to sequentially emit an electron beam from the upper line cathode 2a to the lower line cathode for a predetermined time. The back electrode 1 not only prevents the generation of electron beams from the other line cathodes but also pushes out the electron beams only in the direction of the anode. Although the vacuum container is not shown in FIG. 4, it is also possible to use the back electrode 1 to form a structure integrated with the vacuum container.

The beam extraction electrode 3 is a conductive plate 11 having a plurality of through holes 10 which are arranged in a row in the horizontal direction facing each of the line cathodes 2a to 2m and are arranged at regular intervals. It is taken out through the through hole 10.

Next, the control electrode 4 has a through hole 14 at a position facing each of the line cathodes 2a to 2m, and a conductive plate 15 which is long in the vertical direction.
And a plurality of them are arranged side by side in the horizontal direction at predetermined intervals. In this configuration, 120 conductive plates for control electrodes 1
5a to 15n are provided (only eight are shown in FIG. 4). The control electrode 4 controls the passing amount of each of the electron beams divided in the horizontal direction by the beam extraction electrode 3 in correspondence with the picture element of the video signal and in synchronization with the later-described horizontal deflection timing. .

The focusing electrode 5 is a conductive plate 17 having a through hole 16 at a position facing each through hole 14 provided in the control electrode 4, and focuses the electron beam. The horizontal deflection electrode 6 is composed of a plurality of conductive plates 18 and 18 'vertically arranged along both sides of the through hole 16 in the horizontal direction. Each of the conductive plates has a horizontal deflection voltage. Is being applied. The electron beam for each picture element is deflected in the horizontal direction, and the R, G, B phosphors are sequentially irradiated on the screen 8 to emit light. In this configuration, each electron beam is deflected by 2 trio.

The vertical deflection electrode 7 has a plurality of conductive plates 19, 1 horizontally arranged at the intermediate positions of the through holes 16 in the vertical direction.
9 ', a vertical deflection voltage is applied to deflect the electron beam in the vertical direction. In this structure, the electron beam generated from one line cathode is deflected by eight lines in the vertical direction by the pair of electrodes 19 and 19 '. The 31 vertical deflection electrodes 7 constitute 30 pairs of vertical deflection conductors corresponding to each of the 30 line cathodes, and 240 horizontal scanning lines are drawn vertically on the screen 8. ing.

As described above, in this configuration, the horizontal deflection electrodes 6 and the 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, it becomes possible to irradiate the screen 8 with the electron beam with a small deflection amount. As a result, horizontal and vertical co-deflection distortion can be reduced.

As shown in FIG. 5, the screen 8 is formed by coating the back surface of the glass plate 21 with the phosphor 20 in a stripe shape.
Although not shown, metal back and carbon are also applied. The phosphor 20 horizontally deflects the electron beam passing through one through hole 14 of the control electrode 4 to generate R, G,
The phosphor pairs of three colors B are provided so as to irradiate two trios, and are applied in stripes in the vertical direction.

In FIG. 4, broken lines on the screen 8 indicate vertical divisions corresponding to the plurality of line cathodes 2, and two-dot chain lines correspond to the plurality of control electrodes 4. Indicates the horizontal division that is displayed. An enlarged view of one section partitioned by a broken line and a two-dot chain line is shown in FIG.
As shown in Fig. 5, two trios of R, G, B in the horizontal direction
The phosphor has a width of 8 lines in the vertical direction.
The size of one section is 1 mm in the horizontal direction and 3 mm in the vertical direction in this example. Although the phosphors of three colors R, G and B are shown in stripes in FIG. 5, they may be arranged in a delta shape.
However, when they are arranged in a delta shape, it is necessary to apply horizontal deflection and vertical deflection waveforms suitable for them. It should be noted that in FIG. 4, the vertical and horizontal dimensional ratios are different from the actual image displayed on the screen for the sake of explanation. Further, in this configuration, two trio of R, G, and B phosphors are provided for one through hole 14 of the control electrode 4, but one trio or three trio or more may be configured. . However, R, G, and B video signals of 1 trio or 3 trios or more are sequentially applied to the control electrode 4, and horizontal deflection is required to be performed in synchronization with it.

Next, the operation of the drive circuit for driving this display element will be described with reference to FIG. First, the drive part that irradiates the screen 8 with the electron beam to display the electron beam will be described. The power supply circuit 22 is a circuit for applying a predetermined bias voltage to each electrode of the display element. The back electrode 1 is V1, the beam emitting electrode 3 is V3, the focusing electrode 5 is V5, and the screen 8 is V8. Apply DC voltage. The pulse generating circuit 39 uses the vertical synchronizing signal V and the horizontal synchronizing signal H to drive the line cathode drive pulse (a to
Create).

The timing chart is shown in FIG. 7, and the circuit diagram of the line cathode drive circuit is shown in FIG. Each of the wire cathodes 2a to 2m is shown in FIG.
As shown in (a), the line cathode drive circuit 26 is switched to the H side during the period when the drive pulse has a high potential, and the line cathode heating power source is turned on.
An electric current flows by 46 to heat it. At this time, the line cathode 2
The cut-off power supply 47 raises a to 2a to a potential at which electrons are not emitted. While the drive pulse (i-ma) is at a low potential, the line cathode drive circuit 26 is switched to the L side and the emission power supply 45 keeps the line cathodes 2a-2m at the emission potential and emits electrons. This gives 30
Electrons are emitted from the line cathodes 2a-2m of the book only during the 8 horizontal scanning periods in which low potential drive pulses (i-ma) are applied. During the period when the high potential is applied, the potential is applied to the line cathodes 2a to 2m more than the potential around the line cathode 2 determined by the bias voltage applied to the back electrode 1 and the beam extraction electrode 3. Electrons are not emitted from the line cathode because the potential is higher. In order to form one screen, it is sufficient to sequentially switch the potentials from the upper line cathode 2a to the lower line cathode 2m by every 8 scanning periods.

Next, the deflection part will be described. The deflection voltage generation circuit 40 is
It is composed of a direct memory access controller (hereinafter referred to as DAM controller) 41, a deflection voltage waveform storage memory (hereinafter referred to as deflection memory) 42, a horizontal deflection signal generator 43h, a vertical deflection signal generator 43v, etc.
v, v 'and horizontal deflection signals h, h' are generated.

In this configuration, the vertical deflection signal is displayed in one field for 240 horizontal scanning periods in consideration of overscan. Further, the memory address area storing the vertical deflection position information corresponding to each line is divided into a first field and a second field, and each has a set of memory capacity. When displaying, the corresponding deflection memory
Data is read from 42, converted into an analog signal by the vertical deflection signal generator 43v, and added to the vertical deflection electrode 7.
The vertical deflection position information stored in the deflection memory 42 is 8
Each horizontal scanning period is composed of substantially regular data, and the waveform converted into the deflection signal is also a vertical deflection signal of approximately eight stages, but as described above, it has a memory capacity for two fields. Thus, the position can be finely adjusted for each horizontal scanning line.

Further, with respect to the horizontal deflection signal, it is necessary to horizontally deflect the electron beam in six steps in one horizontal scanning period, and a memory is provided so that the deflection position can be finely adjusted for each horizontal scanning. Therefore, assuming that 480 horizontal scanning periods are displayed during one frame, 4
Although 80 × 6 = 2880 bytes of memory is required, 1440 bytes of memory are actually used because the data of the first field and the second field are shared. At the time of display, the deflection information corresponding to each horizontal scanning line is read from the deflection memory 42, converted into an analog signal by the vertical deflection signal generator 43h, and added to the horizontal deflection electrode 6.
In summary, the electron beam emitted from the line cathode applying the low-potential drive pulse of the line cathodes 2a to 2m during the display period excluding the vertical blanking period of the vertical cycle is as follows.
The beam extraction electrode 3 divides it into 120 sections in the horizontal direction to form 120 electron beam arrays. As will be described later, the control electrode 4 controls the beam passage amount of each electron beam, and after the electron beam is focused by the focusing electrode 5, it is changed into approximately six stages as shown in FIG. Horizontal deflection electrodes 18,1 to which deflection signals h, h 'are added
8 ', R1, G1, B on the screen 8 during each horizontal display period
1 and phosphors such as R2, G2, and B2 are sequentially irradiated in the horizontal display period / 6 each. Thus, each horizontal line has 12 rasters
R1, G1, B1 and R2, G2, B2 electron beams for each of 0 sections
A color image can be displayed on the screen 8 by modulating with a video signal corresponding to.

 Next, the modulation control part of the electron beam will be described.

First, in FIG. 6, the respective R, G, B video signals applied to the signal input terminals 23R, 23G, 23B are applied to 120 sample hold circuit groups 31a to 31n. Each sample and hold group 31a to 31n is for R1, G1, B1 and R2, G2
It consists of 6 sample and hold circuits for B2 and B2. The sampling loop pulse generation circuit 34 has a horizontal cycle (6
3.5μsec) horizontal display period (about 50μsec)
, Each of the 120 pairs of sample and hold circuits 31a to 31n
720 (120 × 6) sampling pulses Ra1 to Rn2 corresponding to the sample hold circuits for 1, G1, B1, and R2, G2, R2 are sequentially issued. Each of the 720 sampling pulses is 120 sets of sample and hold circuit groups 31a-
Six pieces are added to 31n, so that each sample and hold circuit group divides one line into 120 pieces, and each of the R1, G1, B1, R2, G2, and B2 video signals of two picture elements. Are sampled and held individually. 120 sets of sampled and held video signals of R1, G1, B1, R2, G2 and B2 are stored in 120 sets of memory 32a after sample and hold for one line is completed.
The data are simultaneously transferred to 32n by the transfer pulse t, and are held here for the next one horizontal scanning period. The held signal is applied to 120 switching circuits 35a to 35n. Each of the switching circuits 35a to 35n is composed of 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 a switching pulse generating circuit 36 Switching pulse applied from
Switching control is performed simultaneously by r1, g1, b1, r2, g2, and b2. The switching pulses r1, g1, b1, r2, g2, b2 divide each horizontal display period into 6 and switch the switching circuits 35a to 35n by 6 in each horizontal display period R1, G1, B1, R2, G2, B2. Each of the video signals in
a to 37n. The outputs of the switching circuits 35a to 35n are 120 sets of pulse width modulation (hereinafter referred to as PWM) circuits 37a.
˜37n, pulse width modulated according to the magnitude of each video signal of R1, G1, B1, R2, G2, B2, and output. The outputs of the pulse width modulation circuits 37a to 37n are individually applied to the 120 conductive plates 15a to 15n of the control electrode 4 of the display element as control signals for modulating the electron beam.

Next, the timing of horizontal deflection and display will be described.
R1, G1, B1, R2, G2, B2 in switching circuits 35a-35n
Of the video signal and the horizontal deflection drive circuit 41 are synchronously controlled so that the timing of switching the horizontal deflection of the electron beams R1, G1, B1, R2, G2, B2 to the phosphors is completely the same. . As a result, when the R1 phosphor is irradiated with the electron beam, the irradiation amount of the electron beam is controlled by the R1 control signal, and the following G1, B1, R2, G2, and B2 are similarly controlled, and each pixel is controlled. The emission of each R1, G1, B1, R2, G2, B2 phosphor is controlled by the image signals of R1, G1, B1, R2, G2, B2 of that pixel, and each pixel is The light is displayed according to the video signal. This control is simultaneously executed for 120 sets of 1 line (2 picture elements each), and 240 line picture images of 1 line are displayed.
An image is displayed on the screen 8 by sequentially performing the 240 lines in the field from the upper line. Further, the above-described operations are repeated for each field of the input video signal, and the television signal or the like is displayed on the screen 8.

The basic clock required for this configuration is supplied from the pulse generating circuit 39 shown in FIG. 6, and the timing is controlled by the horizontal synchronizing signal H and the vertical synchronizing signal V.

However, in the above-described configuration, in the operation at the time of power-on, electrons are emitted from the line cathode before the vertical deflection signal or the horizontal deflection signal reaches a prescribed voltage, so that the screen plate is dotted. There is a problem that a horizontal line is displayed to give a feeling of strangeness and the life of the phosphor is shortened.

In view of the above problems, the present invention provides an image display device that eliminates the discomfort of the screen and reduces the life of the phosphor when the power is turned on.

Means for Solving the Problems In order to solve the above problems, the image display device of the present invention is
A screen on which a phosphor that emits light when irradiated with an electron beam is coated with a phosphor, a plurality of line cathodes that vertically divide the screen on the screen, and generate an electron beam for each vertical segment, and the cathode A pulse generating circuit for generating a line cathode drive pulse that alternately gives a line cathode heating period for heating and an electron emission period for emitting electrons, a counter for counting a vertical synchronizing signal, and a counter for holding the counted signal. A self-holding circuit, a gate circuit for logically ANDing the held vertical synchronizing signal with the line cathode drive pulse, and a circuit for heating the line cathode and for emitting an electron, respectively connected to each of the line cathodes. A line cathode drive circuit that switches, a diode that conducts only during the line cathode heating period, and a diode that is connected to the diode and that heats the line cathode only during the line cathode heating period. The gate circuit includes: a line cathode heating power source; a cutoff power source that applies a cutoff potential so that electrons are not emitted from the line cathode during the line cathode heating period; and an emission power source that determines the potential of the line cathode during the electron emission period. On the basis of the output of, the line cathode drive circuit is controlled so as to heat the line cathode until the deflection signal settles to a specified voltage.

Action The present invention has the above-described configuration and obtains the time for the deflection signal to settle to the specified voltage after power-on by counting the vertical synchronization signal and holding it by itself. By logically ANDing the signal and the line cathode drive pulse in the gate circuit, the line cathode is heated and electrons are not emitted until the deflection signal settles to the specified voltage after the power is turned on.
Horizontal dots are not displayed on the screen plate so that the screen does not feel uncomfortable and the life of the phosphor is not shortened.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a line cathode drive circuit of an image display device according to an embodiment of the present invention.

In FIG. 1, 26 is a line cathode drive circuit, 39 is a pulse generation circuit, 45 is an emission power supply, 46 is a line cathode heating power supply,
47 is a cut-off power supply, 48 is a diode, 50 is an inverter that inverts the vertical synchronizing signal V, 51 is a counter that counts the vertical synchronizing signal V, 52 is a self-holding circuit that holds the counted signal, 53 is a line cathode The inverter 54 that inverts the drive pulse is a NAND gate that receives the output of the self-holding circuit 52 and the output of the inverter 53. The output of the NAND gate 54 controls the line cathode drive circuit 26.

The operation of the line cathode drive circuit of the image display device configured as described above will be described below with reference to the waveform diagrams of FIGS. 1 and 2.

The pulse generating circuit 39 uses the vertical synchronizing signal V and the horizontal synchronizing signal H to create a line cathode drive pulse. The timing is the same as in the conventional example. The inverter 53 inverts the line cathode drive pulse.

The inverter 50 inverts the vertical synchronizing signal V, and the counter 51 counts the vertical synchronizing signal V up to the set number. Counter 51
The output of is held by the self-holding circuit 52. The counted and self-held signals and the inverted line cathode drive pulse are ANDed by the NAND gate 54 and inverted to be input to the line cathode drive circuit 26.
The operation of the line cathode drive circuit 26 is the same as that of the conventional example. Therefore, the time t for the deflection signal to settle to the specified voltage after power-on is obtained by counting the vertical synchronizing signal by the counter 51 and holding it by the self-holding circuit 52. The signal (the output of the self-holding circuit 52) and the inverted line cathode drive pulse (the output of the inverter 53) are ANDed and inverted by the NAND gate 54 until the deflection signal settles to the specified voltage after the power is turned on. The line cathode drive circuit 26 is connected to the side of the line cathode heating power supply 46, and the line cathodes 2a to 2m are heated and no electrons are emitted.

As described above, according to the present embodiment, the line cathode is heated and no electrons are emitted until the deflection signal settles to the specified voltage after the power is turned on, and dotted horizontal lines are displayed on the screen plate. There is no such thing.

As described above, according to the present invention, a screen coated with a phosphor that emits light when irradiated with an electron beam and an electron beam for each vertical section obtained by vertically partitioning the screen on the screen are provided. A plurality of line cathodes that are generated, a pulse generation circuit that generates a line cathode drive pulse that alternately gives a line cathode heating period for heating the line cathode and an electron emission period for emitting electrons, and a vertical synchronization signal are counted. Counter, a self-holding circuit for holding the counted signal, a gate circuit for ANDing the line cathode drive pulse and the counted and held vertical synchronizing signal, and a line cathode connected to each of the line cathodes. A line cathode drive circuit that switches the circuit to heat or emit electrons, a diode that conducts only during the line cathode heating period, and is connected to the diode. A line cathode heating power source that heats the line cathode only during the line cathode heating period, a cutoff power source that gives a cutoff potential to prevent electrons from being emitted from the line cathode during the line cathode heating period, and a line cathode potential during the electron emission period. By providing an emission power supply that determines, the line cathode is heated and electrons are not emitted until the deflection signal settles to the specified voltage after power-on, and dotted horizontal lines are not displayed on the screen plate, making it feel uncomfortable. It is possible to realize an image display device which does not give rise to the above-mentioned problem and which does not cause a decrease in the life of the phosphor.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a line cathode drive circuit of an image display device according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the line cathode drive circuit of the present invention, and FIG. 3 is a conventional image. FIG. 4 is an exploded perspective view of the image display device used in the present invention, FIG. 5 is an enlarged view of the phosphor screen of the same screen display element, and FIG. 6 is the same image display. FIG. 7 is a block diagram of a drive circuit of the device, and FIG. 7 is a waveform diagram for explaining the operation of the image display device. 26 …… Line cathode drive circuit, 39 …… Pulse generation circuit, 45 ……
Emission power supply, 46 ... Wire cathode heating power supply, 47 ... Cut-off power supply, 48 ... Diode, 50 ... Inverter, 51
...... Counter, 52 …… Self-holding circuit, 53 …… Inverter, 54 …… NAND gate.

Claims (1)

(57) [Claims] 1. A screen coated with a phosphor that emits light when irradiated with an electron beam, and a plurality of line cathodes that divide the screen on the screen in the vertical direction and generate an electron beam for each vertical segment. A pulse generation circuit that generates a line cathode drive pulse that alternately gives a line cathode heating period for heating the cathode and an electron emission period for emitting electrons, a counter for counting a vertical synchronization signal, and a counted signal. A self-holding circuit for holding, a gate circuit for logically ANDing the held and vertical synchronizing signals counted and held by the line cathode drive pulse, and connected to each of the line cathodes,
A line cathode drive circuit that switches circuits to heat the line cathode or emit electrons, a diode that conducts only during the line cathode heating period, and a line cathode that is connected to the diode and that heats the line cathode only during the line cathode heating period. A heating power supply, a cutoff power supply that gives a cutoff potential so as not to emit electrons from the line cathode during the heating period of the line cathode, a cutoff power supply that gives a potential of the line cathode during the electron emission period, and a cutoff power supply of the line cathode during the electron emission period. An emission power source for determining a potential is provided, and based on the output of the gate circuit, the line cathode drive circuit is controlled so as to heat the line cathode until the deflection signal settles to a specified voltage. Image display device.