JPH0459742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for driving a flat panel image display device.

(Conventional configuration and its problems) A basic configuration example of a conventional image display element is shown in the first example.
This will be explained with reference to the diagram. This display element consists of, in order from the back to the front, a back electrode 1, a line cathode 2 as a beam source, vertical focusing electrodes 3, 3', a vertical deflection electrode 4, a beam flow control electrode 5, a horizontal focusing electrode 6, and a horizontal deflection electrode. The structure includes an electrode 7, a beam accelerating electrode 8, and a screen 9, which are housed inside a flat glass bulb (not shown) that is evacuated.

A line cathode 2 serving as a beam source is stretched horizontally so as to generate a band-shaped electron beam distributed linearly in the horizontal direction. Here 2 _a1 ~ 2 _d1
(only four are shown). In this example, it is assumed that there are 15 (2 _a1 ,
2 _p1 ). These line cathodes 2 are, for example, 10~
It consists of an oxide cathode material coated on the surface of a 20 μφ tungsten wire. Then, as will be described later, the electron beams are controlled to be emitted sequentially from the upper line cathode 2 _a1 for a fixed period of time. The back electrode 1 suppresses generation of electron beams from line cathodes 2 other than the line cathode 2 that is controlled to emit electron beams for a certain period of time, and directs the generated electron beams only in the forward direction. It has the effect of pushing out.
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, which serves both as an electron beam extraction means and a vertical focusing means, is a conductive plate 11 having a horizontally long slit 10 facing each of the line cathodes _2a1 to _2p1 . The electron beam is taken out through the slit 10 and focused in the vertical direction (the slit 10 may be provided with bars at appropriate intervals,
Alternatively, it may be a row of a large number of through holes arranged at small intervals in the horizontal direction (so that they almost touch each other), and may be substantially configured as slits. 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. ing. Then, a vertical deflection voltage is applied between the opposing conductors 13 and 13' to deflect the electron beam in the vertical direction. In this embodiment, the electron beam from one line cathode 2 is vertically deflected to 16 lines by a pair of conductors 13, 13'. The 16 vertical deflection electrodes 4 constitute 15 conductor pairs corresponding to each of the 15 line cathodes 2, which ultimately deflect the electron beam to draw 240 horizontal lines on the screen 9. .

Next, the control electrodes 5 (each of these control electrodes 5 divides the electron beam horizontally into one pixel and extracts it, and converts the amount of electron beam passing through the electron beam into a video signal for displaying each pixel). Each conductive plate 15 has a long slit 14 in the vertical direction, and a plurality of conductive plates 15 are arranged in parallel in the horizontal direction at predetermined intervals. In this embodiment, there are 320 conductive plates 15a to 15n for control electrodes.
are provided (only 10 are shown in the figure).
Therefore, if 320 control electrodes 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 with phosphors in three colors, R, G, and B.
The R, G, and B video signals are sequentially applied to each control electrode 5. In addition, 320 sets of video signals for one line are simultaneously applied to the 320 control electrodes 5.
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 320 vertically long slits 16 facing the slits 14 of the control electrode 5, and focuses the electron beam for each pixel divided in the horizontal direction. Each 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 respectively deflected in the horizontal direction, 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 pixel 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 a metal back layer (not shown) is added thereto. The fluorescent substance 20 is one of the control electrodes 5.
For each slit 14, that is, for each horizontally divided electron beam, R,
One pair each of three color phosphors, G and B, are provided and are applied 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 the enlarged view in Fig. 2, one section partitioned by these two has R, G, and B phosphors 20 for one picture element in the horizontal direction, and 16 lines in the vertical direction. It has a width of 30 minutes.
For example, the size of one section is 1 in the horizontal direction.
mm, and the vertical direction is 16 mm.

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 pair of R, G, and B phosphors 20 for one picture element is provided for one control electrode 5, that is, one electron beam, but two
Of course, two or more pairs for more than two picture elements 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 5.
Horizontal deflection is performed in synchronization with this.

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 emit raster light 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 -V 1 to the vertical focusing electrodes 3 and 3'.
DC voltages of V ₃ , V ₃ ', V ₆ to the horizontal focusing electrode 6, V ₈ ' to the accelerating electrode 8, and V ₉ to the screen 9 are applied.

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 pulse and counts horizontal pulses, and is configured to operate during an effective vertical scanning period (here, 240 hours) excluding the vertical retrace period of the vertical period. 15 _driving pulses a ₁ , b ₁ , . These driving pulses a ₁ , b _{1 .}
A line cathode drive pulse a′ ₁ made to a high potential of volts,
b′ ₁ ... o′ ₁ is converted into each line cathode 2 _a1 , 2 _b1 , ...
2 Added to _p1 . Each line cathode 2 _a1 ...2 _p1 is heated by a current flowing through it during the high potential period of the driving pulses a _{' 1} to o' ₁ , and is heated during the low potential period of the driving pulses a' ₁ to o' ₁ . A heated state is maintained so that electrons can be emitted. As a result, electrons are emitted from the 15 line cathodes _2a1 to _2p1 only during the 16H period when low potential drive pulses a′ ₁ to o′ ₁ are applied to each one (during the period when a high voltage potential is applied). , the potential at the line cathode 2 is lower than the potential at the line cathode 2 determined by the bias voltage applied to the back electrode 1 and the vertical focusing electrode 3.
Since the high potential applied to 2 _a1 ~ 2 _p1 becomes positive, no electrons are emitted from the line cathodes 2 _a1 ~ 2 _p1 ). Thus, in the line cathode 2, during the effective vertical scanning period, electrons are sequentially emitted from the upper line cathode 2 _a1 to the lower line cathode 2 _p1 for each 18H period.

The emitted electrons are pushed forward by the conductive surface electrode 1, pass through the opposing slits 10 of the vertical focusing electrode 3, and are vertically focused into a flat electron beam.

Next, the vertical deflection drive circuit 27 generates a vertical drive pulse.
It is composed of a counter that counts horizontal synchronizing signals reset by each of _a1 to _o1 , and a conversion circuit that converts the count output to D/A, and each vertical drive pulse a1 to _o1 . A pair of vertical deflection signals V and V' which change in 16 steps by 1H during _one 16H period are generated. The vertical deflection signals V and V′ both have a center voltage of V ₄ , and V increases sequentially,
V' is configured to change in opposite directions so as to decrease sequentially. These vertical deflection signals V and V' are applied to the conductor 13 of the vertical deflection electrode 4, respectively.
and 13', and as a result, the electron beams generated from each of the line cathodes _2a1 to _2p1 are vertically deflected in 16 steps, and as mentioned earlier, one electron beam is applied to 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 from the top of the 15 line cathodes _2a1 to _2p1 for a period of 16H,
Each electron beam is sequentially deflected one line at a time from above to below within 15 sections in the vertical direction, so that on the screen 9, it is sequentially deflected from the 1st line at the top to the 240th line at the bottom. The electron beam is vertically deflected one line at a time, creating a total of 240 raster lines.

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 horizontally focused 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 20 on the screen 9 are deflected horizontally in three steps.
are irradiated sequentially.

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, three pulses r, g, and b are generated during the active horizontal scanning period of 50 μsec, with each pulse width being approximately 17 μsec.

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.

The horizontal deflection signals h and h' both have a center voltage of _V7 , and change in opposite directions such that h increases sequentially and h' decreases sequentially. These horizontal deflection signals h and h' are applied to the conductive plate 1 of the horizontal deflection electrode 7, respectively.
8 and 18'. 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, in the horizontal deflection electrode 7, one conductive plate 18 or 18' is used for deflecting the electron beams of two adjacent sections. This is because they are designed to produce deflection effects in opposite directions.
In the 320-section electron beam, the odd-numbered one is R→
If the beams are deflected in the order of G→B, then those in even-numbered sections are deflected in the reverse order of B→G→R, and so on, and are 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 then they are combined with the luminance signal Y to generate R, G, B
Each primary color signal (hereinafter referred to as R, G, B video signal) is 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
Each of 1a to 31n has 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 cycle by a shift register, etc., so that the reference clock is applied to the sampling pulse generating circuit 34, where it is delayed by one clock cycle at a time, so that the reference clock is Sampling pulses a to n are sequentially generated, and then one transfer pulse is generated. 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 are respectively connected to the above 320 sample and hold circuit set 31.
a to 31n, thereby providing 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. That sample was held
The 320 R, G, B video signals are stored in 320 sets of memories 32a to 3 after completing the sample hold for one line.
2n, the signals are transferred all at once by a transfer pulse t, and held here for the next one horizontal 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,
The switching circuits 35a-35n are controlled by R, G,
Each video signal of B is time-divided and outputted alternately and sequentially,
Switching signals r, g, and b are generated to supply control power 5 to conductive plates 15a to 15n. However, among the switching circuits 35a to 35n, the odd numbered switching circuits 35a, 35b... are R→
Switching is performed in the order of G→B, and even numbered switching circuits 35b, 35d...35n are switched in the order of B→G.
→R is configured to switch in this order.

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 performed both in timing and order. This means that they are 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 controlled by the R, G, and B video signals of the picture elements, so that each picture element is displayed by emitting light in accordance with the input video signal. Such control is performed simultaneously on 320 picture elements for one line to display one line of video, and then sequentially performed for 240 lines starting from the upper line, so that one video is displayed on screen 9. will be done.

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.

The following problems arose in the flat panel image display device as described above. This problem will be explained below.

The line cathode 2 as a linear beam source is arranged between the back electrode 1 and the vertical focusing electrode 3 which is also an electron beam extraction means, and the width of the band-shaped electron beam taken out from the line cathode 2 is equal to the width of the vertical focusing electrode 3. Electrode 3
By covering the entire surface of a row of electron beam passing holes formed for each line cathode, uniformity of brightness due to the electron beam current in the light emitting means can be ensured. However, the wire cathode 2 is made of a tungsten wire with a diameter of 10 to 20 μm coated with an oxide cathode material, and due to variations in the coating thickness, the band-shaped electron beam width becomes partially narrow. This can be understood by considering the cross section of a wire cathode. That is, for example, if the oxide cathode material is applied evenly over the entire surface, it will form a substantially circular shape, and electron beams will be emitted from everywhere. Due to the electric field formed by the vertical focusing electrode 3 and the vertical focusing electrode 3, there is a 1:1 positional relationship. Therefore, if there is variation in the coating thickness of the oxide cathode material in a part of the line cathode, this will appear as a phenomenon in which the corresponding part reaching the vertical focusing electrode 3 becomes partially narrower than the normal width of the electron beam. That is, local variations occur in the electron beam current passing through the electron beam passage hole. Furthermore, due to variations in the arrangement positions of the line cathodes, the width position of the band-shaped electron beam formed on the surface of the vertical focusing electrode 3 deviates from the position of the electron beam passage hole.
It becomes difficult for the electron beam width to cover the entire hole shape of each electron beam passing hole, and local variations occur in the electron beam current passing through the electron beam passing hole.

There is a problem in that brightness unevenness occurs in images due to such causes.

(Object of the Invention) The present invention solves the above problems by applying a voltage that changes the band-shaped electron beam width so that the electron beam passes over the entire hole shape of a row of electron beam passing holes corresponding to each line cathode. is applied to the back electrode to make the flow of electron beams irradiated onto the light emitting means uniform.

(Structure of the Invention) The structure of the present invention includes a linear beam source arranged in a plurality of rows of a flat panel image display device, a means for extracting the beam, an electron beam control means for controlling the same, and In contrast to the one that uses an electron beam deflection means for deflecting the electron beam and a light emitting means, each line cathode is driven by a line cathode driving pulse.
The electron beam is emitted sequentially for each 16H period in Figure 1, and by adjusting the voltage applied to the back electrode for each electron beam emission period of each line cathode, the electron beam flow irradiated from each line cathode to the light emitting means is made uniform. This is what I am trying to do.

(Description of Embodiment) An embodiment of the present invention will be described using FIG. 4.
The switching circuit 38 has the same number of input terminals as the number of line cathodes 2 _a1 to 2 _a2 and output terminals for sequentially switching and outputting them, and the input terminals a ₁ to o ₁ are connected to the back electrode 1. . Switching circuit 38
is a ₁ output from the vertical drive pulse generation circuit 25
Switched by ~o ₁ . That is, the voltages of the variable power supplies 37 _a1 to 37 _p1 are sequentially applied to the back electrode 1 in a time-divided manner for each 16H period. What should be noted here is that the switching circuit 38 switches the output voltages of the variable power supplies 37 _a1 to 37 _p1 to the back electrode 1, and the line cathode drive circuit 26 controls the electron emission period of each line cathode 2 _a1 to 2 _p1 . The switching is
It is synchronously controlled so that the timings match perfectly. As a result, when the electron beam is irradiated onto the light emitting means by the line cathode _2a1 , the output voltage of the variable power supply _37a1 causes the electron beam to pass over the entire hole shape of the electron beam passage hole of the vertical focusing electrode 3. The width of the band-shaped electron beam emitted from the line cathode 2 is controlled so that the electron beam flow passing through the electron beam passage hole is determined. Similarly, when the electron beam is irradiated to the light emitting means by the line cathodes 2 _{b1 to} 2 _p1 , the variable power sources 37 _b1 to 37 _p1
The electron beam flow is determined by Therefore, by changing the outputs of the variable power supplies 37 _a1 - 37 _p1 , the electron beam flow from each line cathode 2 _a1 - 2 _p1 can be adjusted individually.

As described above, the width of the band-shaped electron beam emitted from the line cathode 2 can be controlled by the voltage applied to the back electrode, and the flow of the electron beam reaching the light emitting means can be made uniform. On the other hand, as described above, the width of the band-shaped electron beam is determined by the electric field formed by the back electrode 1, the line cathode 2, and the vertical focusing electrode 3, which is a vertical focusing means. Therefore, it is also possible to change the width of the band-shaped electron beam by changing the voltage applied to the line cathode 2 or the vertical focusing electrode 3. However, if the voltage applied to the line cathode 2 is changed, the initial potential of the electron beam source changes, and there is a risk that the beam cutoff voltage at the beam flow control electrode 5 will vary. Furthermore, when the voltage applied to the vertical focusing electrode 3 is changed, the focusing action by the electric field formed by the subsequent electrodes, such as the vertical deflection electrode 4 and the beam flow control electrode 5, changes, causing a change in the spot shape of the electron beam. There is a risk.

When the voltage applied to the back electrode is changed, the beam current flowing into the vertical focusing electrode 3 increases or decreases, and at the same time, the band-shaped electron beam width also changes. When the voltage applied to the back electrode is applied in a direction that reduces the voltage difference with respect to the voltage of the vertical focusing electrode, the beam current flowing into the vertical focusing electrode increases and the width of the band-shaped electron beam becomes wider. Become. On the other hand, when a voltage is applied in a direction that increases the voltage difference, the beam current flowing into the vertical focusing electrode decreases and the width of the band-shaped electron beam becomes narrower. Here, when the back electrode voltage is changed so that the electron beam passes through the entire hole shape of the electron beam passing hole formed in the vertical focusing electrode 3, the beam current flowing into the vertical focusing electrode increases. However, the beam current passing through the electron beam passage hole does not change. In other words, it is determined by the size of the hole. However, if the voltage difference is further reduced, the band-shaped electron beam width will expand to the electron beam passing hole corresponding to the adjacent line cathode, deteriorating the image quality, and the beam current flowing into the vertical focusing electrode will increase, resulting in power consumption. Problems that increase will arise. Therefore, the back electrode voltage is set so that the electron beam passes over the entire hole shape of the electron beam passage hole and the beam current flowing into the vertical focusing electrode is minimized.

(Effects of the Invention) With the above configuration, by adjusting the voltage applied to the back electrode for each line cathode, that is, the output of each variable power supply, it is possible to eliminate variations in the spot shape of the electron beam and the cut-off voltage. This has the effect that variations in the beam current caused by the line cathode described above are corrected, and an image can be obtained without variations in brightness caused by the beam current in the light emitting means.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram of a flat panel image display device.
Fig. 2 is an enlarged view of the main part of the phosphor film on the screen in the device, Fig. 3 is a diagram showing the basic driving method of the device, and Fig. 4 is the driving of the flat panel image display device of the present invention. 4 is a basic configuration diagram of a drive circuit for explaining the method, and is a partially modified version of FIG. 3. FIG. DESCRIPTION OF SYMBOLS 1... Back electrode, 2... Line cathode, 3, 3'... Vertical focusing electrode, 4... Vertical deflection electrode (electron beam deflection means), 5... Beam flow control electrode (electron beam control means), 6... Horizontal focusing electrode, 7...Horizontal deflection electrode, 8
... Beam accelerating electrode, 9... Screen (light emitting means),
10...Slit, 11...Conductive plate, 12...Insulating substrate, 13, 13'...Conductor, 14...Slit, 1
5... Conductive plate, 16... Slit, 17, 18, 19
... Conductive plate, 20... Fluorescent material, 22... Power supply circuit, 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 hold circuit, 3
2a-32n...Memory, 33...Sampling reference clock oscillator, 34...Sampling pulse generation circuit, 35a-35n...Switching circuit, 36...
Switching pulse generation circuit, 37 _a1 to 37 _p1 ...
Variable power supply, 38...switching circuit.

[Claims]

1. An electron beam generation source with a plurality of line cathodes, a back electrode provided on the back side of the line cathode, a screen having a phosphor that emits light when irradiated with the electron beam, and an electron beam generated by the electron beam generation source. a focusing electrode that focuses the emitted electron beam; an electrostatic deflection electrode that deflects the emitted electron beam on the way to the screen; It is an image display device equipped with a control electrode for controlling, a resistor circuit that converts changes in electron beam current due to vibration of each line cathode into a voltage and outputs the voltage, and a resistor circuit that detects a DC component voltage of this output voltage. a vibration component detection circuit that inputs the resistance output and the DC component detection output, extracts only the waveform vibration component from the resistance output and outputs it, and a vibration component detection circuit that outputs the vibration component detection output to the back electrode. An image display device comprising a feedback drive circuit that stabilizes the amount of electron beams irradiated onto the screen by providing feedback to the screen.