JPH0376074B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention vertically divides a screen into a plurality of sections, generates an electron beam from a line cathode in each section, and This invention relates to a device that displays a plurality of lines by vertically deflecting an electron beam to display a television image as a whole, and is intended to prevent the adverse effects of vibration of the line cathodes in the field where each line cathode is driven in pulses. The purpose is to provide a device that can do this.

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 are extremely long and thin compared to the screen size. It was impossible to create a full-sized television receiver. In addition, 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 reproducibility of color display, and have not yet been put into practical use.

Therefore, the aim was to create a device that could display television images on a flat display device using electron beams, and the screen was divided vertically into multiple sections. generates an electron beam, deflects each electron beam in the vertical direction for each section to display multiple lines, and further controls the amount of electron beam irradiation to the phosphor using a video signal. The present inventors have devised a device that displays a television image as a whole in this manner.

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

This display element is arranged in order from the back to the front.
Back electrode 1, line cathode 2 as an electron beam source, vertical focusing electrode 3, 3' vertical deflection electrode 4, electron beam flow control electrode 5, horizontal focusing electrode 6, horizontal deflection electrode 7, electron beam accelerating electrode 8, and screen plate. 9
are arranged and configured, and this is housed inside a flat glass pulp (not shown) which is evacuated.

A line cathode 2 serving as an electron beam source is stretched horizontally so as to generate an electron beam distributed linearly in the horizontal direction. In the figure, only four wires 2A to 2D are shown.) In this embodiment, it is assumed that 15 pieces are provided. Let's call them 2i~2yo. These wire cathodes 2 are constructed by coating the surface of a tungsten wire with a diameter of 10 to 20 μΦ with an oxide cathode material for thermionic emission. These line cathodes 2A to 2Y are heated so as to generate a thermionic electron beam by passing an electric current through them, and as will be described later, the electron beams are generated sequentially for a certain period of time starting from the upper line cathode 2A. The pulse is controlled to emit .

The back electrode 1 creates a potential gradient with a vertical focusing electrode 3, which will be described later, and prevents the generation of electron beams from other line cathodes 2 other than the line cathode 2 which is controlled to emit electron beams for a certain period of time. It has the function of suppressing the electron beam and pushing the generated electron beam forward only. The back electrode 1 may be formed by a coating of a conductive material applied to the inner surface of the rear wall of the glass bulb.

The vertical focusing electrode 3 is a conductive plate 11 having a horizontally long slit 10 facing each of the line cathodes 2I to 2Y, and extracts the electron beam emitted from the line cathode 2 through the slit 10, and focus in a direction. This slit 10 actually takes out electron beams for one horizontal line (320 picture elements) in a planar form at the same time, but the figure shows only one section of the electron beam in the horizontal direction. The slit 10 may be provided with crosspieces at appropriate intervals in the middle, or may be substantially configured as a slit by a row of many through holes arranged horizontally at small intervals (nearly touching intervals). may have been done. The vertical focusing electrode 3' is also similar.

A plurality of vertical deflection electrodes 4 are arranged horizontally in the middle of each of the slits 10, and are each composed of conductors 13 and 13' provided on the upper and lower surfaces of an insulating substrate 12. has been done. And the opposing conductors 13, 13'
A vertical deflection voltage is applied between them to deflect the electron beam in the vertical direction. In this configuration example, the pair of conductors 13, 13' deflects the electron beam from one line cathode 2 to positions corresponding to 16 lines in the vertical direction. The 16 vertical deflection electrodes 4 constitute 15 conductor pairs corresponding to each of the 15 line cathodes 2, and in the end, 240 conductor pairs are formed on the screen 9.
The electron beam is deflected to draw a raster of horizontal lines on the book.

Next, the control electrodes 5 are composed of conductive plates 15 each having a vertically long slit 14, and a plurality of control electrodes 15 are arranged in parallel in the horizontal direction at predetermined intervals. In this configuration example, 320 control electrode conductive plates 15a to 15n are provided (only 10 are shown in the figure). Conductive plate 15 of this control electrode 5
Each of a to 15n extracts the electron beam horizontally by dividing it into one picture element at a time, and controls the amount of electron beam passing therethrough in accordance with a video signal for displaying each picture element. Therefore, if 320 conductive plates 15a to 15n of the control electrode 5 are provided, 320 picture elements can be displayed per horizontal line.

In addition, in order to display images in color, each picture element is displayed using phosphors of three colors, R, G, and B, and each control electrode conductive plate 15a to 15n is provided with the R, G, and B phosphors. Each video signal is added sequentially. Furthermore, 320 sets of video signals for one line are simultaneously applied to the 320 conductive plates 15a to 15n for control electrodes, and the video for one line is displayed at one time.

The horizontal focusing electrode 6 is composed of a conductive plate 17 having a plurality of vertically long slits 16 (320 slits 16) opposite to the slits 14 of the control electrode 5. Each beam is focused horizontally into a narrow electron beam.

The horizontal deflection electrode 7 is composed of a plurality of conductive plates 18 arranged vertically in the middle of each of the slits 16, and a horizontal deflection voltage is applied between each conductive plate 18 for each picture element. The electron beams are each deflected in parallel directions, and the R, G, and B phosphors are sequentially irradiated on the screen 9 to cause them to emit light. In this embodiment, the deflection range is the width of one picture element for each electron beam.

The accelerating electrode 8 is composed of a plurality of conductive plates 19 provided horizontally at the same position as the vertical deflection electrode 4, and accelerates the electron beam so that it collides with the screen 9 with sufficient energy.

The screen 9 is constructed by coating the back surface of a glass plate 21 with a phosphor 20 that emits light when irradiated with an electron beam, and adding a metal back layer (not shown). The phosphor 20 is arranged for each slit 14 of the control electrode 5, that is, for each horizontally divided electron beam.
One set each of three color phosphors, R, G, and B, are provided and are coated in stripes in the vertical direction. In FIG. 1, the broken lines drawn on the screen 9 indicate divisions in the vertical direction that are displayed corresponding to each of the plurality of line cathodes 2, and the two-dot chain lines correspond to each of the plurality of control electrodes 5. Indicates the horizontal division displayed. As shown in an enlarged view in FIG. 2, one section partitioned by these two has R, G, and B phosphors 20 for one pixel in the horizontal direction, and 16 lines in the vertical direction. It has a width of The size of one section is, for example, 1 mm in the horizontal direction and 16 mm in the vertical direction.

Note that in FIG. 1, the length in the horizontal direction is greatly enlarged relative to the length in the vertical direction for clarity.

Further, in this embodiment, only one set of R, G, and B phosphors 20 for one picture element is provided for one control electrode conductive plate 15a to 15n, that is, for one electron beam. Of course, two or more picture elements, that is, two or more sets may be provided, and in that case, R, G, and B video signals for two or more picture elements are sequentially applied to the control electrode conductive plates 15a to 15n. and the horizontal direction is done in synchronization with it.

Next, the basic configuration of a drive circuit for displaying television images on this display element will be explained with reference to FIG. First, a driving portion for irradiating the screen 9 with an electron beam to cause the phosphor to emit light and generate a raster will be described.

The power supply circuit 22 is a circuit for applying a predetermined bias voltage (operating voltage) to each electrode of the display element,
-V ₁ to the back electrode 1, and to the vertical focusing electrodes 3 and 3'
V ₃ , V ₃ ' A DC voltage of V6 is applied to the horizontal focusing electrode 6, _V8 is applied to the accelerating electrode 8, and V9 is applied to the screen ₉ .

Next, a composite video signal of a television signal is applied to the input terminal 23, and a synchronization separation circuit 24 separates and extracts a vertical synchronization signal V and a horizontal synchronization signal H. The vertical drive pulse generation circuit 25 is composed of a counter that is reset by a vertical retrace pulse and counts horizontal pulses, and is configured to operate over an effective vertical operation period (here, 240H) excluding the vertical retrace period of the vertical period. 15 drive pulses [A, B...Y] each having a length of 16H are sequentially generated during each 16H period. These drive pulses [I to Y] are applied to the line cathode drive circuit 26, where they are inverted and brought to a low potential only during each pulse period, and at approximately
It is converted into line cathode drive pulses [A', B'...Yo'] made at a high potential of 10 volts, and each line cathode 2A,
2ro, ... will be added to 2yo. Each line cathode 2-2
A current is passed during the high potential of the drive pulse [A' to Yo'], and the heating state is maintained so that electrons can be emitted even during the low potential period of the drive pulse [A' to Yo']. Retained. As a result, 15 wire cathodes 2~
From 2nd onwards, a low potential drive pulse [I'
Electrons are emitted only during the 16H period when ~yo′] is added. During the period when 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 determined by the bias voltage applied to the back electrode 1 and the vertical focusing electrode 3. Since the applied high potential becomes positive, no electrons are emitted from the line cathodes 2I to 2Y. Thus, in the line cathode 2, electrons are sequentially emitted from the upper line cathode 2a toward the lower line cathode 2y every 16H period during the effective vertical scanning period. The emitted electrons are pushed forward by the back electrode 1, pass through the opposing slits 10 of the vertical focusing electrode 3, and are focused in the vertical direction to form a planar electron beam.

Next, the vertical deflection drive circuit 27 includes a counter that counts the horizontal synchronization signal while being reset by each of the vertical drive pulses [I to Y], a conversion circuit that converts the count output from D/A, etc. Each vertical drive pulse [I~Yo]
During the 16H period, a pair of vertical deflection signals V and V' which change in 16 steps by 1H are generated. Both vertical deflection signals V and V' have a center voltage of V ₄ , and V
so that V′ increases sequentially and V′ decreases sequentially,
They are designed to change in opposite directions. These vertical deflection signals V and V' are applied to electrodes 13 and 13' of the vertical deflection electrode 4, respectively, so that
The electron beams generated from each of the line cathodes 2i to 2yo are vertically deflected in 16 steps, and as mentioned earlier, one electron beam is displayed on the screen 9.
The raster is deflected to draw 16 lines of raster one line at a time from the top.

As a result of the above, electron beams are emitted for a period of 16 hours from the top of the 15 line cathodes 2A to 2Y, and each electron beam is sequentially emitted for one line from the top to the bottom within the 15 sections in the vertical direction. By being deflected, the electron beam is vertically deflected one line at a time on the screen 9 from the first line at the top end to the 240th line at the bottom end, thereby drawing a raster of 240 lines in total.

The electron beam thus vertically deflected is horizontally deflected by 320 degrees by the control electrode 5 and the horizontal focusing electrode 6.
It is divided into sections and taken out. Figure 1 shows one of these categories. The amount of electron beam passing through each section is controlled by a control electrode 5, and is focused horizontally by a horizontal focusing electrode 6 into a single narrow electron beam, which is then controlled by horizontal deflection means described below. The R, G, and B phosphors 2 on the screen 9 are deflected horizontally in three steps.
0 is sequentially irradiated.

That is, the horizontal drive pulse generation circuit 28 is composed of three cascade-connected monostable multivibrators, etc., and is triggered by a horizontal synchronization signal to generate three horizontal drives with equal pulse widths within one horizontal period. Generate pulses r, g, b. Here, as an example, each pulse width is approximately 17 μsec.
3 during the effective horizontal scanning period of 50μsec.
Three pulses r, g, and b are generated. These horizontal drive pulses r, g, and b are applied to the horizontal deflection drive circuit 29. The horizontal deflection drive circuit 29 generates a pair of horizontal deflection signals h and h' that change in three stages by being switched by the horizontal drive pulses r, g, and b. Unexpected deflection signal h,
Both h' have a center voltage of V ₇ , and change in opposite directions such that h increases sequentially and h' decreases sequentially. These horizontal deflection signals h, h' are applied to electrodes 18 and 18' of the horizontal deflection electrode 7, respectively.

As a result, each horizontally divided electron beam is horizontally deflected so as to sequentially irradiate the R, G, and B phosphors of the screen 9 for 17 μsec during each horizontal period. However, in the display element of FIG. 1, one conductor 18 or one conductor in the horizontal deflection electrode 7
8' is shared for deflecting the electron beams of two adjacent sections, and is designed to produce deflection effects in opposite directions on the adjacent electron beams, so the electron beam of 320 sections is ,
If the odd-numbered sections are deflected in the order of R→G→B, the even-numbered sections are deflected from B→G.
→R is deflected in the opposite direction every other section.

Thus, in each line raster, the electron beam is divided into R, G,
Each phosphor 20 of B is sequentially irradiated.

Therefore, a color television image can be displayed on the screen 9 by modulating the electron beam with R, G, and B video signals for each horizontal section of each line.

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

First, the composite video signal applied to the television signal input terminal 23 is applied to the color demodulation circuit 30,
Here, the color difference signals of R-Y and B-Y are demodulated,
The G-Y color difference signals are matrix-synthesized, and further, they are combined with the luminance signal Y to generate 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 processed by 320 sample and hold circuit sets 31a to 3.
Added to 1n. Each sample hold circuit group 3
1a to 31n each have three sample and hold circuits for R, G, and B. The sample and hold outputs of these sample and hold circuit sets 31a to 31n are held by memory sets 32a to 32n, respectively.
32n.

On the other hand, the sampling reference clock oscillator 33
is composed of a PLL (phase locked loop) circuit, etc., and generates a reference clock of about 6.4 MHz in this embodiment. The reference clock is controlled to always have a constant phase with respect to the horizontal synchronizing signal H. This reference clock is applied to the sampling pulse generation circuit 34, where it is delayed by one clock period by a shift register, etc., so that during the effective horizontal operation period (approximately 50 μsec) of the horizontal period (63.5 μsec), 320 sampling pulses a to n are generated in sequence, followed by one transfer pulse. These sampling pulses a to n correspond to each picture element when one line of the video to be displayed is divided into 320 picture elements in the horizontal direction, and their positions are always constant with respect to the horizontal synchronizing signal H. controlled by.

These 320 sampling pulses a to n correspond to the above 320 sample and hold circuit sets 31.
a to 31n, thereby adding one line to each sample and hold circuit set 31a to 31n.
When divided into 320 picture elements, the R, G, and B video signals of each picture element are individually sampled and held. The sample-held 320 sets of R, G, B video signals are stored in 320 sets of memory 32a~
32n all at once by a transfer pulse t,
Here, it is held for the next one horizontal scanning period.

One line of R, G, and B video signals held in the memories 32a to 32n are applied to 320 switching circuits 35a to 35n, respectively. The switching circuits 35a to 35n each have R, G,
B individual input terminals and a common output terminal that sequentially switches and outputs them, and the output of each switching circuit 35a to 35n is sent to the control electrode 5 of the display element as a control signal for modulating the electron beam.
are individually applied to each of the 320 conductive plates 15a to 15n. Each switching circuit 35a to 35
n are simultaneously switched and controlled by a switching pulse applied from a switching pulse generating circuit 36. The switching pulse generation circuit 36 receives pulses r,
g and b, and the switching circuits 35a to 35n are switched by dividing the effective horizontal scanning period of about 50 μsec in each horizontal period into three and switching the switching circuits 35a to 35n for about 17 μsec each.
The R, G, and B video signals are outputted alternately and sequentially in a time-division manner, and converted signals r, g, and b are generated to be supplied to the control electrode conductive plates 15a to 15n. However, in the switching circuits 35a to 35n,
Odd numbered switching circuits 35a, 35c...
are switched in the order of R→G→B, and the even numbered switching circuits 35b, 35d, . . . 35n are switched in the order of B→G→R.

What should be noted here is that the switching circuit 3
The switching of the supply of R, G, and B video signals in 5a to 35n and the horizontal deflection of the horizontal deflection of the electron beam to the R, G, and B phosphors by the horizontal deflection drive circuit 29 are carried out in a timely and convenient manner. They are also synchronously controlled so that they match perfectly. As a result, when the electron beam is irradiating the R phosphor, the irradiation amount of the electron beam is controlled by the R video signal, and the G and B are similarly controlled, so that the R and G of each picture element are controlled in the same manner. , B phosphors are respectively controlled by the R, G, and B video signals of the picture elements, and each picture element is displayed by emitting light in accordance with the input video signal. Such control is performed simultaneously on 320 pixels for one line to display one line of video, and then sequentially performed for 240 minutes from the upper line to display one video on screen 9. That will happen.

The above operations are repeated for each field of the input television signal, and as a result,
The screen 9 is similar to a normal television receiver.
The television footage of the video is shown above.

As described above, television images are displayed on this display device.

Note that the terms "horizontal direction" and "vertical direction" in the above explanation refer to the horizontal direction, which is the direction in which line units are displayed when an image is projected, and the vertical direction, which is the direction in which the lines are stacked. It is used in this sense, and is not directly related to the vertical and horizontal directions on the actual screen.

Next, a means for driving a plurality of line cathodes in an image display element using the image display element as described above will be described in detail.

First, an example of a circuit devised by the present inventors prior to the present invention will be described with reference to FIG.

FIG. 4 shows a basic configuration example of the vertical drive pulse generation circuit 25 and the line cathode drive circuit 26. The vertical drive pulse generation circuit 25 is first provided with a counter/decoder 38 for generating vertical drive pulses. This counter decoder 38 counts horizontal pulses such as horizontal synchronizing signals and sequentially generates 16H width drive pulses [I to Y] every 16H period.

In order to control the drive pulse generation in this counter decode 38, the monostable multivibrator 39 is triggered by the vertical synchronization signal V obtained from the synchronization separation circuit to create a pulse Vd up to just before the effective vertical scanning period. The trailing edge sets flip-flop 40 to terminate the vertical blanking pulse VBL. flipflop 4
The vertical blanking pulse VBL with an output of 0 is applied to the counter decoder 38 as a reset signal, and the counter decoder 38 receives this pulse.
Counter decode operation is performed only when VBL is high. Therefore, by controlling with the pulse VBL as described above, the counter decode 38 can always start its operation from the start of the effective vertical scanning period, and the vertical pulse [ [I~Yo] can be generated. The trailing edge of the last drive pulse [Y] then resets the flip-flop 40, bringing the pulse VBL to a low level and keeping the counter current until the beginning of the next valid vertical scan period.
The decoder 38 is controlled so that no output is generated.

In addition, in this circuit, two switching elements of PNP type and NPN type are used as a pair of switching elements that alternately and differentially switch each division in the vertical direction, that is, each of line cathodes 2A to 2Y. Transistors 41i to 41yo, 42i to 4
A push-pull circuit is provided in which the terminals 2 and 4 are push-pull connected through resistors 43 and 43. Then, vertical drive pulses [I to YO] are applied to the bases of transistors 41A to 41Y and 42I to 42Y of each push-pull circuit, and one transistor 41
The emitters of the transistors 42A to 41Y are connected to the positive first power supply (+B) which is the power source for passing heating current through the line cathodes 2A to 2Y, and the emitters of the other transistors 42A to 42Y are connected The collector is connected to a negative second power supply (-B) for cutting off the current flowing through the line cathodes 2I to 2Y and bringing the potential to such a level that an electron beam can be emitted. Also, those two transistors 41
The midpoint between I~41yo and 42I~42yo (however,
Transistor 41i is better than resistor 43i to 43yo.
Connect one end of the series circuit of line cathodes 2-2 and diodes 44-1 to 42-4 for each section, and connect the other end to the point between the first power source and the second power source. It is connected to the voltage point (here, the ground point).

Next, the operation of such a configuration will be explained.
Transistor 41 of each push-pull circuit
When a vertical drive pulse [I to YO] is applied to the bases of A to 41Yo and 42I to 42Yo, during the low level period of the pulse, that is, the heating period, transistors 42A to 42Yo are cut off, and one of the transistors is cut off. Only transistors 41a to 41y are conductive, and the first power supply (+
The heating current from _B1 ) is passed through resistors 43a to 43y to each wire cathode 2y to 2y and diode 44.
The wire cathodes 2A to 2Y are heated sufficiently to a temperature at which they can emit electrons. However, during this high potential period, the potential at the line cathodes 2I to 2Y is higher than the potential at the positions of the line cathodes 2I to 2Y determined by the bias voltage applied to the back electrode 1 and the vertical focusing electrode 3. Since the high potential applied to is higher, no electrons are emitted.

On the other hand, during the period when the vertical drive pulses [I to Y] are at a high level, that is, during the period when an electron beam is to be generated in each division, one of the transistors 41 is
41 y is cut off, and the other transistor 42 y ~ 4
Only 2Yo is conductive, causing diodes 44A to 44Y to be cut off by the second power supply ( _-B2 ). Therefore, at this time, no current from the heating power source flows through the line cathodes 2A to 2Y that should generate the electron beam, but the heating state up to that point is maintained.
As the potential becomes low and the potential of the line cathodes 2i to 2yo becomes lower than the surrounding potential, an electron beam uniformly distributed in the length direction is emitted regardless of the resistance value of each line cathode 2i to 2yo. be done.

In this way, the line cathodes 2I to 2Y are driven by pulses, and during the effective vertical scanning period, electrons are sequentially emitted from the upper line cathode 2I to the lower line cathode 2Y for a period of 16 hours, and the electrons are irradiated onto the screen. Ru.

However, since these wire cathodes 2-2-2 are suspended over glass bulbs, they vibrate when external force is applied to them, and they also heat up when heating current is passed through them. The period when the heating current is cut off and the electrons are emitted are repeated in a 1/60 second cycle, and the length changes due to repeated heating and cooling. causing mechanical vibrations,
There is a disadvantage that the amount of emitted electrons varies over time, which may adversely affect the displayed image on the screen.

That is, as shown in FIG. 5, the wire cathodes 2I to 2Y have one end fixed to the support members 45I to 45Y, and the other end fixed to the elastic members 46I to 46Y for applying tension.
The structure is fixed and stretched horizontally, which of course causes vibrations when an external force is applied to it, and also causes a heating current to flow during the heating period, increasing the temperature, and conversely, during the electron emission period, the heating current is cut off, the temperature decreases, and the total length l of the wire cathodes 2i to 2yo expands and contracts in a 1/60 second cycle, and the bending angle of the elastic members 46i to 46yo changes according to the expansion and contraction. Due to the change in θ, mechanical displacement is applied to the linear cathodes 2i to 2yo, causing mechanical vibrations in the linear cathodes 2i to 2yo. However, line cathode 2-2
There is a mechanical change in the back electrode 1 and the focusing electrode 3.
When the relative position between
Since the DC potential at the positions A to 2Y changes accordingly, the amount of electrons emitted from the line cathodes 2A to 2Y changes, and on the screen 9, the displayed image in each vertical section changes. This results in an adverse effect that appears as a change in brightness.

Purpose of the Invention The present invention solves the above-mentioned conventional disadvantages, and provides display by mechanical vibration of the line cathode even when using an image display element in which a line cathode is stretched and pulse-driven to emit electrons. An object of the present invention is to provide an image display device that can prevent adverse effects on images.

Structure of the Invention In the present invention, in an apparatus using an image display element in which line cathodes are stretched in each of a plurality of vertical sections on a screen and are driven in pulses, emitted light is emitted from each line cathode. The amount of emitted electron beam is detected, and if the amount of emitted electron beam changes due to vibration of each line cathode,
During the electron emission period, the amount of emitted electron beam is always maintained constant by controlling the magnitude of the voltage applied to each line cathode from the second power supply via the second switching element according to its detection output. It is characterized by what it did.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 6 to 8. Figure 6 shows 15 line cathodes 2-2 in the image display element as described above.
Only the circuit used for any one of y is shown.
Therefore, the overall configuration is made up of 15 sets of similar circuits. Here, only one set shown in the figure will be explained.

In this device, one switching transistor 47i to 47y, which is constructed by connecting two transistors in Darlington, and the other switching transistor 48i to 48y, are connected to a heating current limiting resistor 4.
The collectors of transistors 47i to 47yo are connected to the positive first power supply (+B ₁ ), and the transistors 48
Connect the emitters of A to 48Y to the negative second power supply (-B ₂ ) via resistors 50A to 50Y, and connect a wire to the connection point between transistors 48A to 48Y and resistors 49I to 49Y. Cathode 2i~2yo and diode 51i~
Connect one end of the series circuit with 51 yo, and connect the other end with the first
The second power source (+B ₁ ) and the second power source (-B ₂ ) are connected to a voltage point (here, the ground point) between the two. On the other hand, these transistors 47i~47yo and 48i~
In order to control switching between 48 and 48, resistor 5
A series circuit of 2i to 52yo, diodes 53i to 53yo, transistors 54i to 54yo, and resistors 55i to 55yo is connected to the first power supply (+B ₁ ) and the second power supply (-B ₂ ). and its resistors 52i to 52
Vertical drive pulses [I to YO] from the counter decoder 38 of the vertical drive pulse generation circuit are applied to the connection points between Y and diodes 53I to 53Y via diodes 56I to 56Y. Then, pulses with inverted polarity are taken out from the collectors of transistors 54a-54yo and applied to the bases of transistors 48a-48yo, and the pulses are applied to the bases of transistors 48a-48yo.
Add to the base of 57 yo. This transistor 57
I ~ 57 Yo, connect the emitter to the second power supply (-B ₂ )
and connect the collector to transistor 4.
Resistors 58i to 58 are also connected to the intermediate terminals of variable resistors 57i to 57yo, which are connected to the bases of 7i to 47yo and between the first power supply (+B ₁ ) and the ground point.
It is connected via 8yo.

With this configuration, when the vertical drive pulses [I to YO] are applied to the diodes 56I to 56Y, level-converted pulses are output to the collectors of the transistors 54I to 54Y, and the level-converted pulses are output to the collectors of the transistors 54I to 54Y.
The inverted pulse is output to the collector of 57 y, and transistors 48 y to 48 yo and 47
It is added to the base of I~47Yo. As a result, during the low level period of the vertical drive pulse [I to YO], that is, during the heating period, the transistors 48I to 48Y are cut off, and the transistors 47I to 47Y are conductive.
Current I ₁ from the first power supply (+B ₁ ) flows through transistors 47a to 47yo → resistors 49a to 49yo → wire cathode 2
It flows through the diodes 51i to 51yo and heats the line cathodes 2i to 2yo. At this time, since the line cathodes 2i to 2yo have a positive potential, no electron beam is generated from them.

On the other hand, during the period when the vertical drive pulses [I to YO] are at a high level, that is, during the period when an electron beam is to be generated in each vertical section, transistors 48I to 48Y are conductive, and transistors 47I to 47Y are cut off. Therefore, at this time, the negative second power supply (-B ₂ ) is applied to the line cathodes 2i to 2yo via the resistors 50i to 50yo and the transistors 48i to 48yo,
Diodes 51i to 51yo are cut off.
As a result, at this time, each of the line cathodes 2I to 2Y becomes at a low potential of (-B ₂ ) during the pulse period, and no heating current flows, so that the resistance of each line cathode 2I to 2Y decreases. An electron beam is generated with a uniform distribution regardless of the

Then, during the period in which the transistors 47i to 47y are conductive, that is, the heating period, the transistors 47i to 47y are turned on.
The magnitude of the heating current flowing to the line cathodes 2A to 2Y through 47Y is determined by the variable resistors 57A to 57Y connected to the base circuits of the transistors 47A to 47Y. It can be adjusted individually for each position. That is, by adjusting the variable resistors 57a to 57y, the base voltage of the transistors 47a to 47y during the heating period can be changed, thereby controlling the magnitude of the heating current of the line cathodes 2i to 2y. It can be changed.

FIG. 7 shows how electron beams are emitted from the line cathodes 2a to 2y due to such an operation. Here, A is in the heating period, and a heating current is passed through the wire cathodes 2i to 2yo to heat them, so thermoelectrons e are generated from the wire cathodes 2i to 2yo. A positive voltage is applied to the cathodes 2i to 2yo, and the potential at the position where the cathodes 2i to 2yo are placed is more positive than the potential formed by the back electrode 1 and the vertical focusing electrode 3. Therefore, the generated thermoelectrons e exist only around the line cathodes 2i to 2y and are not emitted as an electron beam.

On the other hand, FIG. 7B shows the state of the electron emission period. During this period, a negative voltage is applied to the line cathodes 2a to 2o to bring them to a low potential, so the thermionic electrons e generated by residual heat are vertically emitted. The electron beam is drawn out toward the focusing electrodes 2a-2y and passes through the slit 10, and is used as an electron beam. However, line cathode 2-2
Some of the thermoelectrons generated in y) cannot pass through the slit 10 and are captured by the vertical focusing electrodes 2a to 2y.

In this way, electron beams are emitted from the line cathodes 2i to 2yo, but when the line cathodes 2i to 2yo vibrate for some reason as mentioned above, they are vertically focused with the back electrode 1, as can be seen from FIG. Since the position of the line cathodes 2i to 2y with respect to the electrode 3 changes, and therefore the potential around them changes, the amount of emitted thermoelectrons changes. FIG. 8 shows an example of this state, and A is a line from the connection point between the resistors 49a to 49y and the transistors 48i to 48y to the line cathodes 2i to 2.
B represents the voltage waveform of the drive pulses [A' to Y'] applied to Y and B represents the amount of electron beam emitted and taken out from the slit 10. The 8th line cathode 2i~2yo
If a rectangular waveform drive pulse [A' to Y'] as shown by the solid line in Figure A is added, the electron beam would normally be emitted during the electron emission period as shown in the rectangular waveform shown by the solid line in Figure 8B. The inside is emitted in a constant amount without changing.
If there is a vibration like y, the amount of emitted thermionic electrons itself changes, so the amount of electron beam taken out from the slit 10 also changes as shown by the broken line in FIG. This will cause brightness changes in the displayed image.

Therefore, in this device, as shown in FIG.
and the amount of protection is the line cathode 2
By detecting the change in the amount of captured electrons in the vertical focusing electrode 3, the linear cathodes 2a to 2 The change in the amount of thermionic electrons emitted from y is detected, and based on the detection output, the driving pulses [a' to y] are applied to the line cathodes 2 to 2 during the electron emission period.
By controlling the voltage value of y'], the amount of electron beam extracted is stabilized.

Next, the circuit and operation for stabilization will be explained in detail. First, in FIG. 6, a detection resistor 59 is connected between the V ₃ power supply (+B ₃ ) for the vertical focusing electrode 3 and its conductive plate 11, and its detection output is connected to capacitors 60i to 60y. It is added to the bases of transistors 61-1 through 61-6. Transistors 62i to 62yo are connected in series to the collector sides of these transistors 61i to 61yo, and vertical drive pulses from transistors 54i to 54yo are applied to their bases. And transistors 61-6
The amplified detection output is taken out from the collector of 1, and is added to the bases of transistors 64, 64, 64 through capacitors 63, 63, and then taken out from the emitters and connected to transistors 48, 48, and resistors 50, 50, and 50. Add to the connection point. Variable resistors 65i to 65yo for amplitude adjustment are connected to the bases of the transistors 64i to 64yo.

With this configuration, the conductive plate 1 of the vertical focusing electrode 3
A detection output that detects the amount of electron emission is taken out from the connection point between 1 and the resistor 59. That is, the line cathode 2i~
When the amount of thermionic electrons emitted from the conductive plate 11 is constant, the amount of electrons e' captured by the conductive plate 11 is also constant, so the detection output is also constant as shown by the solid line in Figure 8C. However, when the amount of electrons emitted from the wire cathodes 2I to 2Y changes as shown by the broken line in FIG. 8B due to the vibrations mentioned above, the conductive plate 1 changes accordingly.
Since the amount of captured electrons in No. 1 also changes, the detection output changes to No. 8.
As shown by the broken line in Figure C, it changes according to the amount of electron emission. This detection output is amplified by transistors 61i to 61y. However, the conductive plate 11
As shown in the figure, since it is commonly used for all line cathodes 2A to 2Y, the vertical drive pulses [A to 2Y] are used during the electron emission period. The vertical drive pulse causes transistors 62a to 62y to conduct, so that only the circuit of FIG. 6 for line cathodes 2a to 2y is operated. In this way, the transistor 6
The detection outputs taken out from the collectors of 1A to 61Y are polarity inverted versions of those in FIG. Transistor 48 converts it into a low impedance control signal.
Add to I to 48 Yo.

As a result, the magnitude of the voltage applied from the second power supply (-B ₂ ) to the line cathodes 2i to 2yo during the electron emission period when the transistors 48a to 48yo are conductive is shown by the broken line in FIG. 8A. It can be changed according to the detection output as shown in FIG.
It is possible to control the amount of thermionic electrons emitted from Y. At this time, the polarity of the change in the drive voltage is set to be a polarity that compensates for the change in the amount of electron emission due to vibration of the line cathodes 2-2, etc., and the variable resistors 65-65 are set so that the amount of compensation is equal to the amount of change. By adjusting 65 y, the amount of thermionic electrons emitted from the wire cathodes 2 y to 2 y can be kept constant regardless of their vibrations, etc., and as shown by the solid line in FIG. The amount of beam emitted can always be kept constant.

In this way, by detecting the amount of electron emission from the wire cathodes 2I to 2Y and controlling it to be constant, when using the stretched wire cathodes 2I to 2Y, it is possible to prevent external vibrations. is added or line cathode 2-2
Even if the linear cathodes 2i to 2yo vibrate due to pulse drive, etc., a constant amount of electron beam can always be extracted from the linear cathodes 2i to 2yo, resulting in a good image with no change in brightness etc. can be displayed.

In the above embodiment, the control signal created based on the detection output of the amount of emitted electrons is applied to the emitter side of the transistors 48a to 48y, but even if the control signal is applied to the collector side of the transistors 48a to 48y, Alternatively, a control signal of opposite polarity may be applied on the base side. In addition, line cathodes 2-2
It may be added at the terminals on the side of the diodes 51A to 51Y.

Further, any circuit other than the one in the illustrated embodiment may be used as a circuit for pulse-driving the line cathodes 2a to 2y.

Further, in the above embodiment, the amount of electrons emitted is detected at the conductive plate 11 of the vertical focusing electrode 3, but it goes without saying that the amount of captured electrons may be detected at other electrodes. do not have.

Effects of the Invention As described above, according to the present invention, when a line cathode is used as an electron beam source for each vertical section in an image display element, the line cathode vibrates to change the amount of electron beam emitted. Even in such cases, a fixed amount of electron beam can always be extracted from the line cathode by detecting the amount of electrons emitted from the line cathode and automatically controlling the voltage applied to the line cathode during the electron emission period. Good images with no brightness changes can be displayed.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of an image display element that can be used in the image display device of the present invention, FIG. 2 is an enlarged front view of its screen surface, and FIG. 3 is a block diagram of the basic configuration of its drive circuit. FIG. 4 is a circuit diagram of the basic configuration of the linear cathode drive circuit, FIG. 5 is a sectional plan view of the linear cathode in a stretched state, and FIG. 6 is a diagram showing the driving of the linear cathode of an image display device according to an embodiment of the present invention. 7A and 7B are enlarged sectional views of a part of the device, and FIG. 8 is a waveform diagram illustrating the operation of the device. 2, 2 I to 2 Y... Line cathode as an electron beam source, 3, 3'... Vertical focusing electrode, 4... Vertical deflection electrode, 5... Electron beam flow control electrode, 6... Horizontal focusing electrode, 7... Horizontal deflection electrode, 8... Electron beam acceleration electrode, 9... Screen, 10... Slit, 11... Conductive plate, 20... Fluorescent material, 23...
Input terminal, 24... Synchronization separation circuit, 25... Vertical drive pulse generation circuit, 26... Line cathode drive circuit,
27...Vertical deflection drive circuit, 28...Horizontal drive pulse generation circuit, 29...Horizontal deflection drive circuit, 30
...Color demodulation circuit, 31a to 31n...Sample and hold circuit group, 32a to 32n...Memory group, 3
4...Sampling pulse generation circuit, 35a-3
5n...Switching circuit, 36...Switching pulse generation circuit, 38...Counter decoder, 47i-47yo, 48i-48yo...switching transistor, 49i-49yo...resistor,
50i~50yo...Resistance, 54i~54yo, 57
I ~ 57 Yo... Transistor, 59... Resistor, 6
0i~60yo, 63i~63yo...capacitor,
61i~61yo, 62i~62yo, 63i~63
Yo...transistor, 65i~65yo...variable resistor.

Claims (1)

[Claims] 1. A screen coated with a phosphor, a plurality of line cathodes arranged horizontally so as to generate electron beams in each section when the screen is vertically divided into a plurality of sections, and each of the above line cathodes. a deflection device that deflects the electron beam generated from the line cathode in the vertical direction and irradiates the screen so as to display a plurality of lines of raster on the screen in each vertical section; a control device for controlling the luminous intensity of the screen by controlling the amount of irradiation to the screen, and a pair of switching elements provided for each line cathode and alternately and differentially switching each line cathode to drive each line cathode individually. , a first power source for passing a heating current through each of the linear cathodes, and a second power source for cutting off the heating current of each of the linear cathodes and bringing the potential of each of the linear cathodes to a potential at which an electron beam can be emitted. one end of each switching element of the pair of switching elements is connected to each line cathode, one switching element of the pair of switching elements is connected to the first power supply, and the other switching element is connected to the second power supply. means for connecting to a power supply of the plurality of vertical sections, and a switching element for a line cathode corresponding to the vertical section during a period when an image is to be displayed in each of the plurality of vertical sections. a switching control circuit that applies a switching signal that causes conduction; a detection means that detects the amount of electron beam emitted from each of the line cathodes for each line cathode; and control means for controlling the voltage value from the second power supply based on the detection output from the detection means so as to keep the amount of electron beams emitted from each of the line cathodes constant.