JPH0329354B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention generates an electron beam for each division when a screen on a screen is vertically divided into a plurality of divisions, and generates an electron beam for each division. The present invention relates to an apparatus for displaying a plurality of lines by vertically deflecting a beam to display a television image as a whole.

Conventional configurations and their problems Traditionally, cathode ray tubes have been mainly used as display elements for displaying color television images, but conventional cathode ray tubes are extremely long and thin compared to the screen size. It would have been impossible to create a 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 display, and have not yet been put into practical use.

Therefore, in order to construct a flat display device using electron beams, the present applicant filed a patent application in 1983-
No. 20618 (Japanese Unexamined Patent Publication No. 135590/1983) proposed a new display device.

This method generates an electron beam for each section when the screen is vertically divided into multiple sections, and displays multiple lines by deflecting each electron beam vertically for each section. However, something was invented that displayed a television image as a whole.

First, a basic configuration of the image display element used here will be explained with reference to FIG. This display element includes, in order from the back to the front, a back electrode 1,
Line cathode 2 as a beam source, vertical focusing electrode 3,
3', a vertical deflection electrode 4, a beam flow control electrode 5, a horizontal focusing electrode 6, a horizontal deflection electrode 7, a beam acceleration electrode 8, and a screen 9. ) is housed inside a vacuum chamber. A line cathode 2 serving as a beam source is stretched horizontally so as to generate an electron beam distributed linearly in the horizontal direction. Only four (2a to 2d are shown) are provided. In this example, it is assumed that 15 are provided. Let them be 2a to 2o.
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 2o are heated so as to generate a thermionic electron beam when a current is passed through them.
As will be described later, the electron beams are controlled to be emitted sequentially from the line cathode 2a for a fixed period of time. The back electrode 1 suppresses generation of electron beams from line cathodes other than the line cathode controlled to emit electron beams for a certain period of time, and pushes out the generated electron beams only in the forward direction. act. 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. Further, instead of the back electrode 1 and the linear cathode 2, a planar electron beam emitting cathode may be used.

The vertical focusing electrode 3 is a conductive plate 11 having a horizontally long slit 10 facing each of the line cathodes 2a to 2o. Focus. An electron beam for one horizontal line (360 pixels) is extracted at the same time. In the figure, only one section in the horizontal direction is shown. The slit 10 may be provided with crosspieces at appropriate intervals in the middle, or may be substantially formed as a slit by an example of a large number of through holes arranged side by side at small intervals (almost touching each other) in the horizontal direction. may be done. 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 embodiment, the electron beam from one line cathode 2 is vertically deflected to positions corresponding to 16 lines by a pair of conductors 13, 13'. The 16 vertical deflection electrodes 4 constitute 15 pairs of conductors corresponding to each of the 15 line cathodes 2, and in the end, the electron beams are emitted so as to draw 240 horizontal lines on the screen 9. deflect.

Next, the control electrodes 5 are composed of conductive plates 15 each having a vertically long slit 14, and a plurality of control electrodes 5 are arranged in parallel in the horizontal direction at a predetermined interval. In this example, 180 control electrode conductive plates 15
-1 to 15-n are provided. (Only 9 lines are shown in the figure). Each of the control electrodes 5 extracts the electron beam by dividing it into two picture elements in the horizontal direction, and controls the amount of electron beam passing therethrough in accordance with a video signal for displaying each picture element. Therefore, the conductive plates 15-1 to 15-n for the control electrode 5 are
If 180 lines are provided, 360 pixels can be displayed per horizontal line. In addition, in order to display images in color, each picture element is displayed with phosphors of three colors R, G, and B, and each control electrode 5 has each of R, G, and B for two picture elements. Video signals are added sequentially. In addition, 180 conductive plates 15-1 to 15 for control electrodes 5
-n, 180 sets of video signals for one line (two picture elements per set) are simultaneously applied, 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 (180 slits 16) facing the slits 14 of the control electrode 5, and collects electrons for each picture element divided in the horizontal direction. Each beam is focused horizontally into a narrow electron beam.

The horizontal deflection electrode 7 is made up of a plurality of conductive plates 18, 18' arranged vertically on both sides of the slit 16, and each electrode 18, 18' has six levels of horizontal deflection. A voltage is applied to horizontally deflect the electron beam for each pixel, and on the screen 9 two sets of R,
The G and B phosphors are sequentially irradiated to emit light. In this example, the deflection range is two picture elements wide 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 has R,
Two pairs 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 of FIG. 2, in one section partitioned by these two, there are R, G, and B phosphors 20 for two picture elements in the horizontal direction.
It has a width of 16 lines in the vertical direction. The size of one section is, for example, 1 mm in the horizontal direction,
The vertical direction is 9 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 example, one control electrode 5, that is, one
For the electron beam of the book, R, G, B phosphor 2
Only one pair of 0's for two picture elements is provided, but of course, one picture element or three or more picture elements may be provided, and in that case, the control electrode 5 has one picture element or three or more picture elements. R, G, and B video signals are sequentially added to the image signal, and horizontal deflection is performed in synchronization with the R, G, and B video signals.

Next, the basic configuration and waveforms of each part 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 deflection drive circuit 40 includes a vertical deflection counter 25, a memory 27 for storing vertical deflection signals, and a digital-to-analog converter 39 (hereinafter referred to as a DA converter). Vertical deflection drive circuit 4
As the zero input pulse, the vertical synchronizing signal V and horizontal synchronizing signal H shown in FIG. 4 are used. The vertical deflection counter 25 (8 bits) is reset by the vertical synchronizing signal V and counts the horizontal synchronizing signal H. This vertical deflection counter 25 counts an effective scanning period (here, a period of 240H) excluding the vertical retrace period of the vertical period, and this count output is supplied to the address of the memory 27. Vertical deflection signal data (here, 8 bits) corresponding to each address is output from the memory 27, and the data is sent to the D-A converter 39 as shown in Fig. 4 (Fig. 3 b and D).
It is converted into the vertical deflection signals v and v' shown in FIG. This circuit has memory addresses that store vertical deflection signals corresponding to each line for 240H.
By storing regular data in the memory every 16 hours, a 16-step vertical deflection signal can be obtained.

On the other hand, the line cathode drive circuit 26 uses the vertical synchronization signal V and the output of the vertical deflection counter 25 to create line cathode drive pulses a to o. FIG. 5a shows the relationship between the vertical synchronizing signal V, the horizontal synchronizing signal H, and the lower five bits of the vertical deflection counter 25. FIG. 5b shows a method of creating line cathode drive pulses a' to o' every 16H using these signals. In FIG. 5, LSB indicates the lowest bit, and (LSB+1) means the bit one higher than the LSB.

The first line cathode drive pulse a' can be created by an R-S flip-flop using the vertical synchronization signal V and the output (LSB+4) of the vertical deflection counter 25, and the line cathode drive pulses b' to o' are shifted. This can be obtained by using a register to transfer the line cathode drive pulse a' using the inverted version of the output (LSB+3) of the vertical deflection counter 25 as a clock. These drive pulses a' to o' are inverted so that the potential is low only during each pulse period, and the line cathode drive pulse a is set at a high potential of about 20 volts during other periods.
~ o (Fig. 3 b and E), and each line cathode 2a
~2o added.

Each line cathode 2a to 2o is heated by a prolonged current during the high potential period of the drive pulses a to o, and the heated state is maintained so that electrons can be emitted during the low potential period of the drive pulses a to o. Ru. As a result, electrons are emitted from the 15 linear cathodes 2a to 2o only during the 16H period when low potential drive pulses a to o are applied to each of them. During the period when a high potential is applied, the potential applied to the line cathodes 2a to 2o is higher 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 higher potential is positive, no electrons are emitted from the line cathodes 2a to 2o. Thus, in the line cathode 2, electrons are sequentially emitted from the upper line cathode 2a toward the lower line cathode 2o for each 16H period during the effective vertical scanning period. The emitted electrons are pushed forward by the back electrode 1, and the emitted electrons are pushed forward by the back electrode 1, and the slits 1 facing each other in the vertical focusing electrode 3
0 and is focused in the vertical direction to form a flat electron beam.

Next, the relationship between the line cathode drive pulses a to o and the vertical deflection signals v and v' will be explained with reference to FIG. FIG. 6a is a waveform diagram of a line cathode drive pulse, b is a waveform diagram of a vertical deflection signal, and FIG. 6c is a waveform diagram of a horizontal deflection signal. The vertical deflection signals v, v' in FIG.
During the 16H period of each line cathode pulse a to o in figure a
Changes in 16-step increments of 1 hour. The vertical deflection signals v and v′ both have a center voltage of V ₄ ,
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 respectively applied to the electrodes 13 and 13' of the vertical deflection electrode 4, and as a result, the electron beams generated from the respective line cathodes 2a to 2o are deflected in 16 steps in the vertical direction. As mentioned earlier, on screen 9, one electron beam produces 16
The raster is deflected so as to draw one line at a time from the top.

As a result of the above, electron beams are emitted from the 15 line cathodes 2a to 2o for a period of 16 hours in order from those above them.
In addition, each electron beam is deflected one line at a time from the top to the bottom within the 15 vertical divisions, so that on the screen 9, one line is deflected from the 1st line at the top to the 240th line at the bottom. The electron beam is vertically deflected minute by minute, creating a raster of 240 lines in total.

The electron beam thus vertically deflected is horizontally deflected by 180 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 light is then deflected in six steps in the horizontal direction, and is sequentially irradiated onto each of the R, G, and B phosphors 20 for two picture elements on the screen 9. FIG. 2 shows the vertical and horizontal divisions. The phosphors corresponding to 15-1 to 15-n of the control electrode 5 are R, G, and B for two picture elements, but for convenience of explanation, one picture element is R ₁ , G ₁ , and B _{1 and the other is R 1 , G 1 , and B 1} . Let R ₂ , G ₂ , and B ₂ .

Next, the horizontal deflection drive circuit 41 is composed of a horizontal deflection counter 28 (11 bits), a memory 29 storing horizontal deflection signals, and a DA converter 38. The input pulse to the horizontal deflection drive circuit 41 is synchronized with the vertical synchronizing signal V and the horizontal synchronizing signal H, as shown in FIG. 7, and uses a pulse 6H having a repetition frequency six times that of the horizontal synchronizing signal H. The horizontal deflection counter 28 is reset by the vertical synchronizing signal V and counts horizontal six times the pulse 6H. This horizontal deflection counter 28 counts 6 times during 1H and 240H×6/H=1440 times during 1V, and this count output is supplied to the address of the memory 29.
The memory 29 outputs horizontal deflection signal data (here, 8 bits) according to the address, and the D-
The A converter 38 converts it into horizontal deflection signals such as h and h' shown in FIG. 7 (FIGS. 3B and 3C). This circuit has memory addresses that store horizontal deflection signals corresponding to each of 6 x 240 lines.
By storing six pieces of regular data in the memory for each line, a horizontal deflection signal with six step waves can be obtained in a 1H period.

This horizontal deflection signal is a pair of horizontal deflection signals h and h' that change in 6 steps as shown in FIG. 7, both have a center voltage of V ₇ , and h gradually decreases.
h' increases in sequence and changes in opposite directions. 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 transmitted to the R, G, B,
The light is horizontally deflected so that R, G, and B (R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ ) phosphors are sequentially irradiated for H/6 periods. Thus, in each line raster, the electron beam is divided into 180 sections in the horizontal direction.
Each phosphor 20 of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ is sequentially irradiated with light.

Therefore, an electron beam is applied to each horizontal section of each line.
A color television image can be displayed on the screen 9 by modulating with _the video signals R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , and B 2 .

Next, the modulation control portion of the electron beam will be explained. First, the television signal input terminal 23
The composite video signal added to Combined with signal Y,
R, G, and 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 180 sample and hold circuits 31-
1 to 31-n. Each sample hold circuit 31-1 to 31-n is for _R1 , _G1 ,
It has six sample and hold paths for _B1 , _R2 , _G2 , and _B2 . These sample and hold outputs are respectively applied to holding memories 32-1 to 32-n.

On the other hand, the reference clock oscillator 33 is constituted by a PLL (phase locked loop) circuit, etc., and in this example generates a reference clock 6sc of six times the color subcarrier sc and a reference clock 2sc of twice the color subcarrier sc.
The reference clock is controlled to always have a constant phase with respect to the horizontal synchronizing signal H. The reference clock 2sc is added to the deflection pulse generation circuit 42, and the signals 6H and H/6, which are six times the horizontal synchronizing signal H, are
The signal switching pulses r ₁ , g ₁ , b ₁ , r ₂ , g ₂ , b ₂ (Fig. 3b and B) are obtained for each signal switching pulse. On the other hand, the reference clock 6sc is applied to the sampling pulse generation circuit 34, where it is delayed by one clock cycle by a shift register, and is then delayed for an effective horizontal scanning period (approximately
1080 sampling pulses during 50μsec)
R ₁₁ , G ₁₁ , B ₁₁ , R ₁₂ , G ₁₂ , B ₁₂ , R ₂₁ , G ₂₁ ,
B ₂₁ , R ₂₂ , G ₂₂ , B ₂₂ ~ _{Rn 1} , Gn ₁ , Bn ₁ , Rn ₂ ,
Gn ₂ and Bn ₂ (FIG. 3b and A) are generated in sequence, and then one transfer pulse t is generated. This sampling pulse R ₁₁ ~Bn ₂ is one of the images to be displayed.
It corresponds to each picture element when a line is divided into 360 picture elements in the horizontal direction, and its position is controlled so that it is always constant with respect to the horizontal synchronizing signal H.

These 1080 sampling pulses R ₁₁ to Bn ₂ each form 180 sets of sample hold circuits 31-1.
~ 31-n, and thereby each sample hold circuit 31-1 ~ 31-n has 1
When the line is divided into 180 lines, the video signals of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ for each two picture elements are individually sampled and held. The sample-held 180 pairs of R ₁ , G ₁ , B ₁ , R ₂ ,
The video signals of G ₂ and B ₂ are stored in 180 sets of memories 32-1 to 32-n after completing the sample hold for one line.
are transferred all at once by a transfer pulse t, and held here for the next horizontal period. This held
The signals R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ are applied to switching circuits 35-1 to 35-n. The switching circuits 35-1 to 35-n each have R ₁ ,
It is composed of a tri-state or analog gate having individual input terminals for G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ and a common output terminal for sequentially switching and outputting them.

The output of each switching circuit 35-1 to 35-n is 180 sets of pulse width modulation (PWM) circuits 37-1.
~37-n, where the reference pulse signal is pulse width modulated according to the magnitude of the sampled and held R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ video signal and output. be done. The repetition period of the reference pulse signal is the above signal switching pulse r ₁ , g ₁ , b ₁ , r ₂ , g ₂ ,
It is desirable that the pulse width be sufficiently smaller than the pulse width of b ₂ , for example, a pulse width of about 1:10 to 1:100 is used.

The outputs of the pulse width modulation circuits 37-1 to 37-n are used as control signals for modulating the electron beam to the 180 conductive plates 15-1 of the control electrode 5 of the display element.
~15-n, respectively. The switching circuits 35-1 to 35-n are simultaneously controlled by switching pulses _r1 , _g1 , _b1 , _r2 , _g2 , _b2 applied from the switching pulse generating circuit 36. Switching pulse generation circuit 36
is controlled by the signal switching pulses r ₁ , g ₁ , b ₁ , r ₂ , g ₂ , b ₂ from the deflection pulse generation circuit 42 described above, and each horizontal period is divided into 6 and divided into H/6. Switch the switching circuits 35-1 to 35-n one by one,
Each video signal of R ₁ , G ₁ , B ₁ , R ₂ , G ₂ , B ₂ is time-divided and outputted sequentially, and the pulse width modulation circuits 37-1 to 3
Switching signals r ₁ , g ₁ , b ₁ ,
Generate r ₂ , g ₂ , b ₂ .

What should be noted here is that the switching circuit 3
R ₁ , G ₁ , B ₁ , R ₂ in 5-1 to 35-n,
G ₂ , B ₂ video signal supply switching and electron beams R ₁ , G ₁ , B ₁ , R ₂ ,
The horizontal deflection for switching the irradiation of G ₂ and B ₂ to the phosphor is
They are synchronously controlled to completely match both timing and order. As a result, when the electron beam is irradiating the R ₁ phosphor, the irradiation amount of the electron beam is controlled by the R ₁ video signal, and the same applies to G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ R ₁ , G ₁ , B ₁ , of each picture element are controlled by
R ₂ , G ₂ , B ₂ The emission of each phosphor is R ₁ ,
Each picture element is controlled by the video signals of G ₁ , B ₁ , R ₂ , G ₂ , and B ₂ , and each picture element is displayed by emitting light according to the input video signal. Such control is performed simultaneously for 180 sets of one line (2 picture elements each), so that an image of 360 picture elements per line is displayed, and then sequentially for 240 H of lines starting from the upper line. One image will be displayed.

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 problem with the image display device configured as described above is that since the wire cathode 2 is used in a vacuum, the wire cathode 2 tends to vibrate, and furthermore, because the damping coefficient is small, the wire cathode 2 suddenly starts to vibrate. is the point where it takes several minutes to several tens of minutes for the vibration to stop. As is clear from the structure of the image display device, when the position of the line cathode 2 changes due to vibration, the position and brightness of the electron beam reaching the screen 9 change, significantly degrading the image quality.

Purpose of the Invention The present invention aims to prevent the vibration of the line cathode itself in order to prevent image quality deterioration due to the vibration of the line cathode.

Structure of the invention The invention has a screen coated with a phosphor, a line cathode suspended in vacuum as an electron source, and an electrode group for deflecting, focusing, and controlling the electron beam generated from the line cathode, A means for electrically detecting the stretching position of the wire cathode and changes in position due to vibration as the amount of electrons flowing in from the wire cathode and its changes, and changing the phase of the signal of the detected change in position by 90 degrees. a phase conversion circuit for converting the signal into a signal corresponding to the vibration speed of the wire cathode, and a means for applying a signal corresponding to the vibration speed of the wire cathode as a voltage to the wire cathode itself; The means are operated in a time-division manner.

The basic method for preventing vibration of a wire cathode is explained using the following equation. In general, linear vibration phenomena are expressed by equation (1).

d ² / dt ² + γd / dt + ω ² = F … (1) where is the displacement, γ is the damping constant, ω is the natural frequency, and F is the term proportional to the external force. In the above equation (1), the second term on the left side is proportional to the speed of vibration of the line cathode, and the larger the damping constant γ, the faster the damping, and the smaller the vibration amplitude itself. In the present invention, in the electric field created by the back electrode and the vertical focusing electrode that sandwich the wire cathode, the wire cathode is fixed so that the electric force received by the wire cathode changes as shown in the second term on the right side of equation (2) below. This changes the voltage in proportion to the speed of vibration.

d ² /dt ² +γd/dt+ω ² =F−Ad/dt…(2
) Here, A is a proportionality constant, and Ad/dt is the electric force applied to the line cathode.As a result, the reduction constant γ becomes equivalently larger as shown in the following equation (3), and image quality deterioration due to the vibration of the line cathode is reduced. It is preventable.

d ² /dt ² +(γ+A)d/dt+ω ² =F (3) Note that equation (3) is a modification of equation (2), and the attenuation constant is increased to (γ+A).

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. In FIG. 8, 50 is a current-voltage conversion circuit that detects the vibration of the line cathode 2 as a current flowing into the vertical focusing electrode 3 and converts the current value into a voltage;
1 is a sample and hold circuit for interpolating the output voltage of the current-voltage conversion circuit 50 using horizontal pulses, and 52 is a phase conversion for making the output of the sample and hold circuit 51 proportional to the vibration speed of the line cathode 2. The circuit 53 is a line cathode drive output circuit for applying a voltage proportional to the vibration speed of the line cathode 2 to the line cathode 2, and has output terminals corresponding to the number of line cathodes 2.

Next, the operation will be further explained using FIGS. 9 and 10. Here, as an example, the line cathode 2
A case will be described in which the vibration of a is detected and the vibration is suppressed. The line cathode drive output circuit 53 outputs a pulse signal that is at a low level during the horizontal retrace period based on the horizontal pulse. This output pulse signal is
It is applied to an integrator (not shown) together with the line cathode drive pulse a from the line cathode drive circuit 26 shown in the figure, and its output is applied to the line cathode 2a. At this time, the line cathode drive pulse A applied to the line cathode 2a becomes as shown in FIG. 9A, and is at the same low level as the line cathode drive pulse a from the line cathode drive circuit 26 during the electron beam emission period. However, during the line cathode heating period, the horizontal retrace period is modulated to a low level. Therefore, an electron beam is emitted from the line cathode 2a during each low-level horizontal retrace period during the heating period. In this way, an electron beam is emitted from the line cathode 2a during each horizontal retrace period during the line cathode heating period, and the electron beam flow at this time is detected as a current by the vertical focusing electrode 3, which causes the line cathode 2a to vibrate. Based on this detection signal, the line cathode 2a is detected in the subsequent circuit.
treated to prevent vibration. In addition, with respect to this line cathode drive pulse A (FIG. 9A), the drive pulses applied to the other line cathodes 2b to 2o are created such that they become high level during the horizontal retrace period in the electron beam emission period. However, during the electron beam emission period, the electron beam is not emitted during the horizontal retrace period, that is, the detection period. The waveforms of the drive pulses B and C applied to the line cathodes 2b and 2c in this case are shown in FIGS. 9B and 9C.

The waveform of the current flowing through the vertical focusing electrode 3 based on the linear cathode driving pulse A (FIG. 9A) is shown in FIG. 10A. This current value is converted into a voltage value in a current-voltage conversion circuit 50, and further interpolated using a horizontal pulse in a sample-and-hold circuit 51, and the output voltage shown in FIG. 10B is outputted at its output terminal.
This voltage waveform (FIG. 10B) corresponds to the positional change due to vibration of the wire cathode 2a. That is, when the line cathode 2a is displaced toward the back electrode 1 side, the current flowing through the vertical focusing electrode 3 in FIG. 10A becomes smaller,
On the other hand, when it is displaced toward the vertical focusing electrode 3 side, the current shown in FIG. 10A increases. Therefore, the voltage waveform shown in FIG. 10B also corresponds to the position of the linear cathode 2a.

Next, the phase of the voltage shown in FIG. 10 (b) is rotated by 90 degrees by the phase conversion circuit 52, and converted into a voltage waveform (FIG. 10 (c)) corresponding to the vibration speed of the line cathode 2a, thereby driving the line cathode. It is added to the output circuit 53. Then, the line cathode drive output circuit 53 applies the drive pulse A (FIG. 9A) that becomes low level during the horizontal retrace period of the line cathode heating period as described above to the line cathode 2a, and other line cathodes 2b, 2c~
Drive pulses B and C are at high level during the horizontal retrace period of the electron beam emission period (Fig. 9 B and C).
At the same time, while the drive pulse A is at a high level, the voltage waveform shown in FIG.
A pulse signal is generated to apply an electric force corresponding to the voltage waveform of FIG. 10C to the wire cathode 2a in the electric field created by Accordingly, the waveform of the driving pulse A changes as shown in FIG. 9A, and the linear cathode 2a
vibrations will be suppressed.

The vibrations of linear cathodes other than the linear cathode 2a can also be suppressed in a time-sharing manner by the same method as described above.

As another embodiment, a circuit that simultaneously suppresses the vibration of two or more line cathodes will be described. For the sake of simplicity, a circuit for simultaneously suppressing the vibrations of the linear cathodes 2a and 2b will be described with reference to FIGS. 11 and 12. Pulse A (first
In Figure 2A), even during the electron beam emission period, the pulse is such that the high level and low level are alternately repeated every horizontal retrace period, and the line cathode 2
The pulse B (FIG. 12B) that drives the drive pulse A (FIG. 12B) is the same as the drive pulse A (the first
The line cathode drive pulse C (Figure 12C) and the following pulses are driven during the electron beam emission period. Pulse A, B
During the horizontal retrace period, which is at a low level during the line cathode heating period, the pulse becomes high level and is applied to the line cathodes 2a, 2b and each of the other line cathodes 2c to 2o. At this time, the current flowing through the vertical focusing electrode 3 alternately appears as the current emitted from the line cathodes 2a and 2b during the horizontal retrace period.

The current flowing through the vertical focusing electrode 3 during the horizontal retrace period is converted into a voltage value by a current-voltage conversion circuit 50, and two sample and hold circuits 51a and 5 are driven alternately by a T-type flip-flop 54.
The current input to line cathode 1b and emitted from line cathodes 2a and 2b is independently interpolated.

Similarly, voltages corresponding to the vibrations of the two wire cathodes 2a and 2b are converted to two series of phase conversion circuits 52a and 52.
After independently converting the phase by 90° by b,
The voltage is applied to the line cathode drive output circuit 53.

Effects of the Invention As described above, the present invention prevents the vibration of the wire cathode by detecting the vibration of the wire cathode and applying forced damping to the wire cathode electrically using the detection signal. 1 (1/sec) was obtained. This is an improvement of more than two orders of magnitude compared to the value of 0.001 to 0.01 (1/sec) when no electrical damping is applied, and no deterioration in image quality due to the vibration of the line cathode was observed.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of an image display element used in an image display device to which the present invention is applied, Fig. 2 is an enlarged view of a fluorescent screen of the image display element, and Fig. 3 is an illustration of driving the image display element. A block diagram of the drive circuit and waveform diagrams of each part, Figures 4, 5, 6,
7 is a waveform diagram of each part for explaining the operation of the drive circuit, FIG. 8 is a block diagram of the main part of the image display device in one embodiment of the present invention, and FIG.
10 is a waveform diagram for explaining the operation of the same device, FIG. 11 is a block diagram of the main part of an image display device in another embodiment of the present invention, and FIG. 12 is a waveform diagram for explaining the operation of the same device. FIG. 1... Back electrode, 2,2a-2o... Line cathode, 3...
Vertical focusing electrode, 4... Vertical deflection electrode, 5... Beam flow control electrode, 7... Horizontal deflection electrode, 9... Screen,
50... Current voltage conversion circuit, 51... Sample hold circuit, 52... Phase conversion circuit, 53... Line cathode drive output circuit.

Claims (1)

[Claims] 1 A screen coated with phosphor, a line cathode suspended in vacuum as an electron source, and a group of electrodes for deflecting, focusing, and controlling the electron beam generated from the line cathode, and the line cathode means for electrically detecting the stretching position and the change in position due to vibration as the amount of electron inflow from the line cathode and the change thereof;
A phase conversion circuit changes the phase of the detected position change signal by 90 degrees to convert it into a signal corresponding to the vibration speed of the wire cathode, and a voltage is applied to the wire cathode itself to convert the signal corresponding to the vibration speed of the wire cathode into a signal corresponding to the vibration speed of the wire cathode. What is claimed is: 1. An image display device comprising: means for applying a voltage to the line cathode;