JPH01132282A - Parabola generation circuit and picture quality correction circuit for crt using this circuit - Google Patents

Abstract

PURPOSE:To prevent the generation of phase shift from the faceplate position of a beam by generating the voltage of a parabolic waveform which synchronizes with horizontal deflection and vertical deflection, and comes higher according as it goes to the circumferential part of the faceplate, according to a current to be supplied to a horizontal deflecting coil and a vertical deflecting coil. CONSTITUTION:The voltage of a vertical parabolic waveform is generated by a second voltage generation circuit 2, and at the same time, the voltage of a horizontal parabolic waveform is generated as well by a first voltage generation circuit 1 in a similar way, and those are summed and supplied to a third grid G3. Accordingly, when such a circuit is used for the CRT of a multiscanning system, even if working frequency changes, dynamic focus can be realized without resetting a time constant as leaving it as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a method for achieving uniform image quality on the entire screen of a CRT, for example, for use in computer terminals, which has a relatively high resolution and requires good image quality. The present invention relates to a parabola generation circuit for obtaining a parabola and a CRT image quality correction circuit using this circuit.

[Conventional technology]

Currently, most CRTs in general use, both color and monochrome, have an electron gun structure called a cathode modulation type. In the case of a cathode modulation type electron gun, there are various names for the electron gun depending on its structure. However, basically, if the cathode modulation type is used, the voltage between the first grid G1 and the cando causes the anode current Ib of the CRT to
, that is, the brightness of the screen changes.

Similarly, the spot diameter of the electron beam on the fluorescent screen of the CRT and the anode current Ib change depending on the voltage between the first grid G1 and the second grid G2, and the voltage between the first grid G1 and the third grid 03 changes the spot diameter of the electron beam on the fluorescent screen of the CRT and the anode current Ib. Focus changes.

Currently, TV-grade monitors have 1st to 3rd grid G.
l, G2. G3 is used by applying an appropriate DC bias voltage, and in relatively high-resolution monitors, a dynamic method is used in which horizontal or horizontal and vertical parabolic voltages are superimposed only on the third grid G3 that controls the focus. It was used in a method called focus.

FIG. 8 is a block diagram showing an example of a conventional CRT dynamic focus circuit.

In this figure, 1a and 2a are horizontal.

3a is an adder circuit, 4a is an amplifier circuit, 5 is a CRT, and AMP3a is a differential circuit into which voltages of parabolic waveforms in both horizontal and vertical directions are input. Amplifier R1 is a feedback resistor for the adder of the differential amplifier AMP3a, AMP4
a is the output of the differential amplifier AMP3a on the third grid G.
An amplifier for amplifying up to the driving voltage of 3, R2 is the amplifier A
MP4a gain determining feedback resistor, VR3
A is a variable resistor for adjusting the parabolic waveform voltage required for the third grid G3. G3 is a decoupling capacitor, which transmits only the AC component of the parabolic waveform voltage in the output signal of the amplifier AMP4a to the third grid G3.

El is a DC bias power supply for the third grid G3, R4 is a load resistor for stabilizing the output of the amplifier AMP4a, and R5
is a bias resistor.

[Problem to be solved by the invention]

Previously, CRTs with relatively round tube surfaces were used, but
Recently, FS tubes have been increasingly used to improve the visibility of screens.

In an FS tube, the difference in the distance from the electron gun to the phosphor screen between the center and the periphery is significantly large, so if it is an FS tube CRT for TV grade for general home use, the third grid G
3 can be used satisfactorily by the DC voltage application method (called static focus as opposed to dynamic focus), but for FS tube CRTs for computer terminals, which have higher resolution than TV grade Practical image quality cannot be obtained unless a parabolic voltage is superimposed only on G3.

Particularly in computer terminal displays, etc., the number of display dots increases and multi-windows are increasingly used, but when windows are displayed at the periphery of the screen, compared to when they are displayed at the center, There was a problem that it became difficult to see.

However, since the period of the parabolic waveform signal for correction is set by the time constant of the circuit, it is possible to
When used in a multi-scan CRT that can change the operating frequency within the kHz range, it is necessary to set a time constant according to the operating frequency each time, and since the signal is generated by an integrating circuit, there is a time delay. This caused the problem that the screen position of the beam and the voltage of the parabolic waveform did not match.

The present invention was made to solve such problems, and can be used in multi-scan type CRTs, and also includes a parabola generation circuit and a parabola generation circuit for eliminating the phase shift between the screen position of the beam and the voltage of the parabola waveform. The purpose of this invention is to obtain a CRT image quality correction circuit using the circuit.

[Means to solve the problem]

The parabola generation circuit according to the first invention of the present invention is comprised of CR
a first voltage generation circuit that generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the horizontal deflection based on the current supplied to the horizontal deflection coil of the T;
a second voltage generating circuit that generates a parabolic waveform voltage that increases toward the periphery of the screen in synchronization with the vertical deflection based on the current supplied to the vertical deflection coil;
and an addition circuit that adds the voltages output from the second voltage generation circuit.

The CRT image quality correction circuit according to the second invention of the present invention includes:
A CRT having a first grid that mainly controls brightness, a second grid that controls spot diameter or spot diameter and brightness, and a third grid that controls focus.
A first voltage that generates a parabolic waveform voltage that increases toward the periphery of the screen in synchronization with the horizontal deflection based on the current supplied to the horizontal deflection coil. a second voltage generating circuit that generates a parabolic waveform voltage in which the voltage increases toward the periphery of the screen in synchronization with the vertical deflection based on the current supplied to the vertical deflection coil; and an addition circuit that adds the voltages output from the first and second voltage generation circuits and supplies the result to the third grid.

A CRT image quality correction circuit according to a third aspect of the present invention includes:
Based on the current supplied to the horizontal deflection coil, a first voltage generation circuit generates a voltage with a parabolic waveform that becomes higher toward the periphery of the screen in synchronization with the horizontal deflection, and supplies the voltage to the vertical deflection coil. a second voltage generating circuit that generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the vertical deflection based on the current generated by the screen; This device includes an adding circuit that adds the output voltages and supplies the resultant voltage to the third grid, and a drive circuit that divides the output of the adding circuit and supplies the divided voltage to the second grid.

[Effect]

In the first aspect of the present invention, the phase of the voltage of the horizontal and vertical parabolic waveforms generated based on the currents supplied to the horizontal deflection coil and the vertical deflection coil is independent of the frequency used. Always synchronize with screen position.

In the second aspect of the present invention, horizontal and vertical parabolic waveform voltages generated based on the currents supplied to the horizontal deflection coil and the vertical deflection coil are supplied to the third grid, and the dynamic four-waveform is supplied to the third grid. Kasu is done.

At this time, the screen position of the beam and the phase of the voltage of the parabolic waveform are always synchronized regardless of the frequency used.

Further, in the third aspect of the present invention, in addition to the effect of the second invention, the beam is driven by a parabolic waveform voltage whose phase is synchronized with the screen position of the beam supplied from the drive circuit to the second grid. The closer you go to the periphery, the smaller the spot diameter becomes and the brightness increases.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a parabola generation circuit according to the first invention and a CRT image quality correction circuit according to the second invention.

In this figure, the same symbols as in FIG. 8 indicate the same things,
1.2 are first and second voltage generation circuits that generate horizontal and vertical parabolic waveform voltages, respectively; 3 is an adder circuit;
4 is the amplifier circuit, L r , L 2 is the horizontal deflection coil and vertical deflection coil of the CRT5, C1 is the 3-character correction capacitor for horizontal linearity correction, C2 is the vertical output capacitor, AMPI is the 8-character correction AMP2 is a differential amplifier that picks up the parabolic waveform voltage generated across the capacitor c1, AMP2 is a differential amplifier that picks up the parabolic waveform voltage generated across the output capacitor C2, and VRI is the image quality in the center and left and right directions of the screen. The variable resistor VH2 for adjusting the unevenness correction amount is a variable resistor for adjusting the amount of image quality unevenness correction in the center and up and down directions of the screen.

In this embodiment, differential amplifiers AMPI and AMP2 are configured as shown in FIGS. 2 and 3, respectively. In other words, the input terminal of the inverting amplifier is set as one input terminal,
The output terminal of this inverting amplifier is used as the other input terminal, and the resistance values of the resistors RIO and R20 and the resistance values of the resistors R30 and R4 are
0 and the resistance value of R50 is set appropriately. As a result, the voltage of 200 to 360v applied between the input terminals is
After being converted to about 15V, it will be inverted.

In addition, the differential amplifier AMP3 and the amplifier AMP4 are configured as shown in FIGS. 4 and 5, respectively. In particular, the amplifier AMP4 uses a cascode amplifier that hardly produces a mirror effect to increase the speed and eliminate phase shift. I'm trying to prevent it from happening.

Normally, in the case of a color CRT, left and right binction distortion is corrected using a circuit, and the general method is to generate a parabolic waveform synchronized with the vertical deflection and modulate the horizontal deflection.

In the CRT image quality correction circuit of the present invention, by applying the parabolic waveform generation circuit system for color CRT binction distortion correction, a vertical parabolic waveform voltage is generated in the second voltage generation circuit 2, and a horizontal The parabolic waveform voltage is also generated in the same manner by the first voltage generation circuit 1,
After adding these up, it is supplied to the third grid G3.

Therefore, when used in a multi-scan type CRT or the like, dynamic focus can be achieved without changing the time constant even if the operating frequency changes.

In addition, since the output of the differential amplifier AMP2 can be used as it is as a parabola waveform for binction distortion correction, the vertical parabola generation circuit can be changed from the conventional circuit configured as shown in the block diagram of FIG. 6(a) to one. This makes it possible to omit the configuration shown in the block diagram of FIG. 6(b).

Recently, electron guns with a quadrupole electrode structure in which a negative lens is formed in the vertical direction and the third grid is divided into two directions (horizontal and vertical) to alleviate vertical overfocus, so-called DBS electron guns and DAF Although electron guns have been announced, it is of course possible to apply the present invention to these electron guns.

FIG. 7 is a block diagram showing an embodiment of a CRT image quality correction circuit according to the third aspect of the present invention.

In this figure, the same symbols as in Figure 1 indicate the same parts, 6 is a drive circuit, VH4 is a variable resistor, and amplifier AMP
This is for stabilizing the output of the second grid G2, and at the same time, for obtaining the parabolic voltage required for the second grid G2 by dividing the output of the amplifier AMP4. C4 is the second grid G
The decoupling capacitor E2 for the second grid G2 is a DC bias power supply for the second grid G2.

Generally, the DC bias voltage value of the second grid G2 is
Although it is fixed at 500-800v, which is smaller than 6000v-8000v of grid G3, in this invention, the parabolic modulation component of third grid G3 is connected to variable resistor VR.
4 and is applied to the second grid G2.

That is, the same parabolic waveform as the third grid G3 is superimposed on the second grid G2 as well.

Therefore, the spot diameter of the beam becomes smaller toward the periphery from the center of the screen, and it is possible to make the spot diameter substantially uniform over the entire screen by correcting the voltage of the parabolic waveform, just like dynamic focusing. Also, regarding the brightness, the brightness increases in a parabolic manner from the center of the screen toward the periphery, similar to the change in spot diameter, and correction is performed in the same way as in the case of the beam diameter.

However, since the brightness of the screen is primarily influenced by the voltage between the first grid G1 and the cathode, the second grid G1
The optimum values of the beam diameter correction amount and the brightness correction amount due to the second voltage do not necessarily match, but depend on the structure of the electron gun and the like. However, by applying a voltage with a parabolic waveform to the second grid G2, it is possible to simultaneously correct the beam diameter and brightness, and the effect is large.

Generally, the reason why the beam spot shape becomes larger at the periphery of the screen is not only caused by the CRT's electron gun structure, but also by the deflection yoke. It is distorted into an elliptical shape at the periphery rather than the original.

However, as in this invention, increasing the voltage of the second grid G2 and reducing the beam spot diameter improves visual resolution, resulting in an improvement in image quality similar to spot diameter correction for a round beam. has already been confirmed through experiments.

Furthermore, since the present invention generates a voltage with a parabolic waveform based on the current supplied to the horizontal deflection coil and the vertical deflection coil, it is also applicable to multi-scan type CRTs that can change the operating frequency. It can be used without changing the time constant of the circuit.

Although the above embodiment shows a case in which a parabolic waveform voltage is supplied to the second grid, the third grid, and the horizontal deflection coil, the application of the parabola generation circuit of the present invention is not limited to these. Needless to say, it may be used for supplying to one grid or the like.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

In the parabola generation circuit of the first invention, based on the currents supplied to the horizontal deflection coil and the vertical deflection coil,
Since it generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the horizontal and vertical deflections, the time constant must be reset depending on the frequency used even when using a multi-scan CRT. In addition to eliminating the need for this, it is possible to obtain a voltage with a parabolic waveform that does not cause a phase shift with respect to the screen position of the beam.

In the second invention, a parabolic waveform voltage is supplied to the third grid in synchronization with the horizontal and vertical deflections, and the voltage increases toward the periphery of the screen, making it possible to adjust the frequency to be used with high precision. A dynamic focus circuit that does not require this can be realized.

In the third invention, since the output of the dynamic focus circuit is divided and supplied to the second grid, it is possible to correct unevenness in image quality, and almost uniform image quality can be obtained on the entire screen, especially in FS[-CRT. Great effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the parabola generation circuit of the first invention and the CRT image quality correction circuit of the second invention, and FIGS. 2, 3, and 4 are diagrams showing differential amplifiers, respectively. Figure 5 is a diagram showing the configuration of the amplifier, Figure 6 is a diagram showing the configuration of the amplifier (
a) and (b) are block diagrams showing peripheral circuits of a CRT, FIG. 7 is a diagram showing an embodiment of an image quality correction circuit according to the third aspect of the present invention, and FIG. 8 is a diagram showing an example of a dynamic focus circuit. FIG. In the figure, 1 and 2 are first and second voltage generation circuits, 3 is an adder circuit, 4 is an amplifier circuit, and 6 is a drive circuit.

Claims (3)

[Claims] (1) A first voltage generating circuit (1 ), and a second voltage generating circuit (2) that generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the vertical deflection based on the current supplied to the vertical deflection coil. , and an addition circuit (3) for adding the voltages output from the first and second voltage generation circuits. (2) Image quality of a CRT that has a first grid (G1) that mainly controls brightness, a second grid (G2) that controls spot diameter or spot diameter and brightness, and a third grid (G3) that controls focus. A first voltage generation circuit which is an unevenness correction circuit and generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the horizontal deflection based on the current supplied to the horizontal deflection coil. (
1), and a second voltage generation circuit that generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the vertical deflection based on the current supplied to the vertical deflection coil (
2) and an addition circuit (
3) A CRT image quality correction circuit comprising: (3) Image quality of a CRT that has a first grid (G1) that mainly controls brightness, a second grid (G2) that controls spot diameter or spot diameter and brightness, and a third grid (G3) that controls focus. A first voltage generation circuit which is an unevenness correction circuit and generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the horizontal deflection based on the current supplied to the horizontal deflection coil. (
1), and a second voltage generation circuit that generates a voltage with a parabolic waveform that increases toward the periphery of the screen in synchronization with the vertical deflection based on the current supplied to the vertical deflection coil (
2), an adder circuit (3) that adds the voltages output from the first and second voltage generating circuits and supplies the voltage to the third grid; and an adder circuit (3) that divides the output of the adder circuit and supplies the voltage to the second grid. A CRT image quality correction circuit comprising: a drive circuit (6) for supplying a signal to a CRT;