JP2003219202A - Device and method for correcting image distortion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide low-cost image distortion correcting device and image distortion correcting method capable of correcting image distortion without increasing power consumption in a reciprocating deflection system. <P>SOLUTION: A writing side PLL circuit 2 generates a write clock WCK for writing a video signal VDI to a line memory 1. A reading side PLL circuit 3 generates a read clock RCK for reading a video signal VDO stored in the line memory 1. An inner pin cushion distortion correction voltage generation circuit 4 generates an inner pin cushion distortion correction waveform by modulating a correction waveform of a horizontal rate with a correction waveform of a vertical rate, adds a direct current component correction pulse and outputs the inner pin cushion distortion correction waveform added with the direct current component correction pulse as an inner pin cushion distortion correction voltage VA. A capacitive coupling system circuit 5 superimposes the inner pin cushion distortion correction voltage VA upon an output voltage of a loop filter 32 of the reading side PLL circuit 3 and gives the inner pin cushion distortion correction voltage VA as a control voltage VC to a VCO 33. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image distortion correction device and an image distortion correction method for correcting distortion in an image displayed on a screen by a reciprocal deflection method based on a video signal.

[0002]

2. Description of the Related Art In a CRT (cathode ray tube), an image is displayed on a screen by deflecting an electron beam by a deflection magnetic field and irradiating it on a fluorescent screen. Since the radius of the phosphor screen of the CRT is larger than the radius from the deflection center point of the electron beam to the phosphor screen, the movement amount of the electron beam in the peripheral portion of the screen for the same deflection amount is the same as that of the electron beam in the center portion of the screen. It becomes larger than the amount of movement. As a result, when the cross hatch patterns that are originally equally spaced are displayed on the screen, a phenomenon occurs in which the intervals of the cross hatch patterns widen from the central portion of the screen toward the peripheral portion.

Such a phenomenon occurs both in the horizontal scanning direction and in the vertical direction of the screen, but in the horizontal scanning direction, since the deflection difference is larger than that in the vertical direction, the image distortion appears remarkably. Such image distortion is called left and right pincushion distortion. Therefore, normally, the left and right pincushion distortion is corrected by flowing a deflection current so as to reduce the deflection amount in the peripheral portion of the screen.

[0004]

However, when the left and right pincushion distortion correction is performed so that the vertical lines at the left and right ends of the image on the screen become straight lines, a straight line is formed at the intermediate portion between the center of the screen and the left and right ends. The phenomenon that the vertical line that should be curved inwardly occurs. Such a phenomenon is called inner pincushion distortion.

The inner pincushion distortion increases as the CRT becomes thinner and flatter. In order to correct the inner pincushion distortion thus increased, it is necessary to increase the correction amount.

In the CRT, as described above, the electron beam is deflected by the deflection magnetic field to display an image on the screen. In this case, in order to generate a deflection magnetic field, a deflection current of several App (ampere peak peak) is passed through the deflection yoke in the deflection system. When the inner pincushion distortion is corrected in the deflection system, the deflection current is modulated. However, since the current amount is large, the larger the correction amount, the larger the power consumption in units of several W (watt). Therefore, it is difficult to correct the inner pincushion distortion by adjusting the deflection current in the deflection system while suppressing the power consumption.

Further, when the inner pincushion distortion is corrected in the deflection system, the circuit structure becomes complicated and the cost reduction is hindered.

On the other hand, in recent years, a reciprocating deflection method has been proposed in order to improve image quality. In the reciprocal deflection method, a horizontal deflection current that changes in a triangular wave shape is supplied to the horizontal deflection coil to scan the electron beam bidirectionally. The odd scan lines are scanned from the left side to the right side of the screen, and the even scan lines are scanned from the right side to the left side of the screen. Since the scanning line density in the vertical direction is twice as high as that in the normal one-direction deflection method, the resolution is increased and the brightness is improved.

However, in the reciprocating deflection method, since the horizontal deflection coil equivalently has an inductance component and a resistance component connected in series to it, the horizontal deflection current supplied to the horizontal deflection coil is distorted. . As a result, the pixel position in the forward scan (hereinafter referred to as trace) and the pixel position in the backward scan (hereinafter referred to as retrace) are displaced in the horizontal scanning direction.

FIG. 35 (a) is a diagram showing an ideal reciprocating deflection display screen, and FIG. 35 (b) is a diagram showing a reciprocating deflection display screen in which a deviation has occurred. In FIG. 35, the position of the screen in the horizontal scanning direction is represented by the x coordinate, and the position of the screen in the vertical direction is represented by the y coordinate.

In the ideal reciprocal deflection, as shown in FIG. 35 (a), pixels that should be vertically aligned are displayed at the same x coordinate during tracing and retracing. For example, in trace and retrace, the display positions of the pixels e1 and e2 at the center of the screen in the horizontal scanning direction have the same x coordinate.

On the other hand, in actual reciprocal deflection, since the horizontal deflection coil equivalently has an inductance component and a resistance component connected in series to it, as shown in FIG. Pixels that should be lined up are shifted in the horizontal scanning direction between tracing and retracing. As a result, the vertical lines that should be originally displayed in a straight line are displayed in a zigzag pattern. For example, at the time of tracing and retracing, the display positions of the central pixels e1 and e2 in the horizontal scanning direction of the screen have different x coordinates.

Therefore, in the reciprocating deflection type image display device, it is necessary to correct the inner pincushion distortion and also the image shift at the time of tracing and retracing.

An object of the present invention is to provide a low-cost image distortion correction apparatus and image distortion correction method capable of correcting image distortion and image deviation without increasing power consumption in the reciprocating deflection method. is there.

[0015]

(1) First invention An image distortion correction device according to a first invention is an image for correcting distortion of an image displayed on a screen by a reciprocal deflection method based on a video signal. A distortion correction device, comprising storage means for storing a video signal, write clock generation means for generating a write clock for writing an input video signal in the storage means, and a video signal stored in the storage means. Read clock generating means for generating a read clock for reading, and a distortion correction waveform for generating a distortion correction waveform for correcting the image distortion by moving the position of the pixel displayed on the screen based on the video signal. The frequency of the read clock generated by the read clock generation means is controlled based on the distortion correction waveform generated by the generation means and the distortion correction waveform generation means. That a read clock control means, the distortion correction waveform generating means, the movement amount of the pixel at the ends and center of the image in the horizontal scanning direction becomes 0,
Further, the distortion correction waveform is set so that the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction.

In the image distortion correction device according to the present invention,
The video signal input in response to the write clock generated by the write clock generation means is written in the storage means, and the video signal stored in the storage means is read in response to the read clock generated by the read clock generation means. Be done. At this time, the frequency of the read clock is controlled by the read clock control means on the basis of the distortion correction waveform generated by the distortion correction waveform generation means,
The read cycle of the video signal from the storage means changes. As a result, the positions of the pixels displayed on the screen are moved by the reciprocal deflection method based on the video signal, and the image distortion is corrected.

In this case, the amount of pixel movement is 0 at both ends and the center of the image in the horizontal scanning direction, and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. Since the distortion correction waveform is set so as not to shift in the horizontal scanning direction, the positions of both ends and the center of the image do not shift, and the shift of the image does not occur in the forward scan and the backward scan.

As described above, the image distortion can be corrected by changing the read clock using the distortion correction waveform without changing the deflection current in the deflection system, so that the power consumption does not increase. Further, since it is possible to correct the image distortion by providing the distortion correction waveform generation means and the read clock control means without improving the deflection system, the circuit configuration does not become complicated and the cost reduction is hindered. I can't.

(2) Second Aspect of the Invention An image distortion correcting apparatus according to a second aspect of the present invention is the image distortion correcting apparatus according to the first aspect of the present invention, wherein the distortion correction waveform generating means has a length equal to twice the horizontal scanning period. A first correction waveform generating means for generating a first correction waveform having a first portion which changes in a cycle and corresponds to a forward scan and a second portion which corresponds to a backward scan; Second correction waveform generating means for generating a changing second correction waveform, first correction waveform generated by the first correction waveform generating means, and second correction waveform generating means for generating the second correction waveform generating means. The first portion and the second portion have symmetry on the time axis, including a modulation means for obtaining a distortion correction waveform by modulating with the correction waveform.

In this case, the vertical scanning is performed with the first correction waveform which changes at a period twice the horizontal scanning period and has the first portion corresponding to the forward scanning and the second portion corresponding to the backward scanning. A distortion correction waveform is obtained by modulating with a second correction waveform that changes in a cycle. As a result, when the deviation in the horizontal scanning direction between the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan is corrected in the reciprocating deflection type deflection system, it is displayed on the screen. The image distortion can be corrected over the entire image that is displayed.

(3) Third Aspect of the Invention An image distortion correcting apparatus according to a third aspect of the present invention is the image distortion correcting apparatus according to the first aspect of the present invention, wherein the distortion correction waveform generating means has a length equal to twice the horizontal scanning period. A first correction waveform generating means for generating a first correction waveform having a first portion which changes in a cycle and corresponds to a forward scan and a second portion which corresponds to a backward scan; Second correction waveform generating means for generating a changing second correction waveform, first correction waveform generated by the first correction waveform generating means, and second correction waveform generating means for generating the second correction waveform generating means. A third modulating waveform is generated to modulate the modulating means and a deviation in the horizontal scanning direction between the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. The third correction waveform generating means and the modulating means The first correction waveform generation means includes a synthesis means for obtaining a distortion correction waveform by synthesizing the modulated first correction waveform and the third correction waveform generated by the third correction waveform generation means. The first correction waveform generated has the pixel movement amount of 0 at both ends and the center of the image in the horizontal scanning direction, and is displayed on the screen by the forward scan and the image displayed on the screen by the forward scan. The corrected image is corrected on the basis of the third correction waveform generated by the third correction waveform generating means so as not to shift in the horizontal scanning direction.

In this case, the vertical scanning is performed with the first correction waveform which changes at a period twice the horizontal scanning period and has the first portion corresponding to the forward scanning and the second portion corresponding to the backward scanning. A distortion correction waveform is obtained by modulating with a second correction waveform that changes in a cycle. As a result, distortion occurs in the horizontal deflection current generated in the reciprocating deflection type deflection system, and the horizontal scanning direction of the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. Even if a shift occurs, the image distortion can be corrected over the entire image displayed on the screen.

(4) Fourth Aspect of the Invention An image distortion correcting apparatus according to a fourth aspect of the present invention is the image distortion correcting apparatus according to the third aspect of the present invention, wherein the distortion correction waveform generating means is a third aspect based on temperature fluctuation. Correction waveform generating means for correcting the third correction waveform generated by the correction waveform generating means, wherein the first correction waveform generating means is based on the third correction waveform corrected by the correction waveform correcting means. , The pixel movement amount is 0 at both ends and the center of the image in the horizontal scanning direction, and the image displayed on the screen by the forward scanning and the image displayed on the screen by the backward scanning are in the horizontal scanning direction. The first correction waveform is corrected so as not to shift.

In this case, the third correction waveform is corrected based on the temperature fluctuation, and the pixel movement amount becomes 0 at both ends and the center of the image in the horizontal scanning direction based on the corrected third correction waveform. The first correction waveform is corrected so that the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction.

As a result, even if the temperature fluctuates,
The image distortion is corrected without causing the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan to shift in the horizontal scanning direction.

(5) Fifth Invention An image distortion correction device according to a fifth invention is the image distortion correction device according to any one of the second to fourth inventions, wherein the modulation means has the first correction. First generated by the waveform generating means
And a multiplying unit for multiplying the corrected waveform of No. 2 by the second corrected waveform generated by the second corrected waveform generating unit.

In this case, the first correction waveform is modulated with the second correction waveform by multiplying the first correction waveform and the second correction waveform, and the distortion correction waveform is obtained.

(6) Sixth Invention An image distortion correction device according to a sixth invention is the image distortion correction device according to any one of the second to fourth inventions, wherein the modulation means has the first correction. First generated by the waveform generating means
The amplifier means is provided with an input terminal for receiving the correction waveform of 1 and a gain control terminal for receiving the second correction waveform generated by the second correction waveform generating means.

In this case, by amplifying the first correction waveform with a gain corresponding to the second correction waveform, the first correction waveform is modulated into the second correction waveform, and the distortion correction waveform is obtained.

(7) Seventh Invention An image distortion correction apparatus according to a seventh invention is the image distortion correction apparatus according to any one of the second to sixth inventions, wherein
The correction waveform of corresponds to the change in the frequency of the read clock, and when the scanning direction is a positive pixel movement amount on the screen at the time of the forward scan in which the scanning is performed from left to right, the left edge of the screen is
The pixel movement amount becomes 0 at the center and the right end, the pixel movement amount changes in the order of 0, positive, 0, negative, and 0 between the left end and the center, and the pixel movement amount becomes between the center and the right end. 0, negative,
0, positive, and 0, and when the scan direction on the screen is positive when the pixel movement amount is positive when scanning in the backward direction in which the scanning is performed from right to left, the pixel movement amount at the right edge, center, and left edge of the screen. Becomes 0, and the amount of pixel movement between the right end and the center is 0,
It is set to change in the order of positive, 0, negative and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive and 0, and the second correction waveform is The upper and lower ends in the vertical direction are set to have a larger amplitude than the central part.

When the inner pincushion distortion is generated by the left and right pincushion distortion correction, among the plurality of vertical lines displayed on the screen, the vertical line in the middle portion between the left and right ends and the center is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the positions of the pixels above and below the vertical line in the middle part inward.

(8) Eighth Invention An image distortion correction device according to an eighth invention is the image distortion correction device according to any one of the second to sixth inventions, wherein
The correction waveform of corresponds to the change in the frequency of the read clock, and when the scanning direction is a positive pixel movement amount on the screen at the time of the forward scan in which the scanning is performed from left to right, the left edge of the screen is
The pixel movement amount becomes 0 at the center and the right end, the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and the pixel movement amount becomes between the center and the right end. 0, positive,
When the scan direction on the screen is positive with respect to the pixel movement amount during the backward scan in which the scanning direction changes from 0, negative, and 0, and the scanning is performed from right to left, the pixel movement amount at the right edge, center, and left edge of the screen. Becomes 0, and the amount of pixel movement between the right end and the center is 0,
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0. The amplitude is set to be larger at the central portion in the vertical direction than that at the upper and lower ends.

When the inner pincushion distortion occurs due to the left and right pincushion distortion correction, the vertical line in the middle portion between the left and right ends and the center among the plurality of vertical lines displayed on the screen is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the position of the pixel at the center of the vertical line in the middle part to the outside.

(9) Ninth Invention An image distortion correcting apparatus according to a ninth invention is the image distortion correcting apparatus according to any one of the first to eighth inventions, wherein the read clock generating means is a read clock. A distortion-corrected waveform generating means outputs the distortion-corrected waveform as a distortion-corrected voltage, and a read clock control means controls the distortion-corrected waveform generated by the distortion-corrected waveform generating means. The voltage is superimposed on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop.

In this case, the distortion correction voltage is superimposed on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop, so that the frequency of the read clock changes. As a result, the read cycle of the video signal read from the storage means changes, and the position of the pixel displayed on the screen moves based on the video signal, whereby the image distortion is corrected.

(10) Tenth Invention An image distortion correction apparatus according to a tenth invention is the image distortion correction apparatus according to any one of the second to sixth inventions, wherein the first correction waveform is read. Corresponding to the change of the clock cycle, when the scanning direction on the screen is positive when the pixel movement amount is positive at the time of the forward scan that is performed from left to right, the pixel movement amounts at the left edge, center, and right edge of the screen are 0, the pixel movement amount changes in the order of 0, positive, 0, negative, and 0 between the left end and the center, and the pixel movement amount is 0, negative, 0, positive, and 0 between the center and the right end. If the pixel movement amount is positive in the scanning direction on the screen during the backward scan in which the scanning is performed from right to left, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen.
The pixel movement amount between the right end and the center is 0, positive,
It is set in the order of 0, negative and 0, and the pixel movement amount between the center and the left end is set to change in the order of 0, negative, 0, positive and 0, and the second correction waveform is the vertical direction of the screen. The amplitude is set to be larger at the upper and lower ends in the direction as compared with the central part.

When the inner pincushion distortion occurs due to the left and right pincushion distortion correction, the vertical line in the middle portion between the left and right ends and the center among the plurality of vertical lines displayed on the screen is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the positions of the pixels above and below the vertical line in the middle part inward.

(11) Eleventh Invention An image distortion correction apparatus according to an eleventh invention is the image distortion correction apparatus according to any one of the second to sixth inventions, wherein the first correction waveform is read. Corresponding to the change of the clock cycle, when the scanning direction on the screen is positive when the pixel movement amount is positive at the time of the forward scan that is performed from left to right, the pixel movement amounts at the left edge, center, and right edge of the screen are 0, the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and the pixel movement amount is 0, positive, 0, negative and 0 between the center and the right end. If the pixel movement amount is positive in the scanning direction on the screen during the backward scan in which the scanning is performed from right to left, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen.
The pixel movement amount between the right end and the center is 0, negative,
It is set to change in the order of 0, positive, and 0, and the pixel movement amount between the center and the left end is set to change in the order of 0, positive, 0, negative, and 0. The amplitude is set to be larger at the center of the direction than at the upper and lower ends.

When the inner pincushion distortion is generated by the left and right pincushion distortion correction, the vertical line in the middle portion between the left and right ends and the center among the plurality of vertical lines displayed on the screen is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the position of the pixel at the center of the vertical line in the middle part to the outside.

(12) Twelfth Invention An image distortion correction device according to a twelfth invention is the image distortion correction device according to the tenth or eleventh invention, wherein the read clock generating means generates a read clock. The phase-locked loop having a voltage controlled oscillator is included, and the distortion correction waveform generation means further includes conversion means for converting the distortion correction waveform obtained by the modulation means into a distortion correction voltage corresponding to a change in the frequency of the read clock. The read clock control means superimposes the distortion correction voltage output by the distortion correction waveform generation means on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop.

In this case, the distortion correction voltage is superimposed on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop, so that the frequency of the read clock changes. As a result, the read cycle of the video signal read from the storage means changes, and the position of the pixel displayed on the screen moves based on the video signal, whereby the image distortion is corrected.

(13) Thirteenth Invention An image distortion correction apparatus according to a thirteenth invention is the image distortion correction apparatus according to the ninth invention, wherein the average value of the distortion correction voltage in each horizontal scanning period of the video signal is obtained. Is further provided with a correction pulse adding means for adding a correction pulse to the distortion correction voltage during the horizontal blanking period so that?

In this case, since the average value of the oscillation frequency control voltage of the voltage controlled oscillator becomes a predetermined value in each horizontal scanning period of the video signal, the average value of the frequency of the read clock generated by the voltage controlled oscillator is constant. Becomes In this way, the operation of the phase locked loop does not change by preventing the average value of the oscillation frequency control voltage of the voltage controlled oscillator from changing before and after the distortion correction voltage is superimposed.

(14) Fourteenth Invention An image distortion correction apparatus according to a fourteenth invention is the image distortion correction apparatus according to the twelfth invention, wherein the average value of the distortion correction voltage in each horizontal scanning period of the video signal is obtained. Is further provided with a correction pulse adding means for adding a correction pulse to the distortion correction voltage obtained by the converting means in the horizontal blanking period so that the value becomes a predetermined value.

In this case, since the average value of the oscillation frequency control voltage of the voltage controlled oscillator becomes a predetermined value in each horizontal scanning period of the video signal, the average value of the frequency of the read clock generated by the voltage controlled oscillator is constant. Becomes In this way, the operation of the phase locked loop does not change by preventing the average value of the oscillation frequency control voltage of the voltage controlled oscillator from changing before and after the distortion correction voltage is superimposed.

(15) Fifteenth Invention An image distortion correcting apparatus according to a fifteenth invention is the image distortion correcting apparatus according to the thirteenth or fourteenth invention, wherein the correction pulse adding means is arranged for every horizontal scanning period. In addition, a correction pulse is added to the distortion correction voltage before the phase comparison time of the phase locked loop in the horizontal blanking period so that the average value of the distortion correction voltage becomes a predetermined value.

(16) Sixteenth Invention An image distortion correction device according to the sixteenth invention is the ninth and twelfth inventions.
In the configuration of the image distortion correction device according to any one of the fifteenth invention, the phase-locked loop divides a read clock output from the voltage-controlled oscillator, and a phase of an output signal of the divider. The read clock control circuit further includes a phase comparator that compares the phases of predetermined reference signals and a loop filter that smoothes the output voltage of the phase comparator and inputs the voltage to the voltage controlled oscillator through the output node. An emitter follower transistor having a base for receiving the distortion correction voltage output by the correction waveform generating means, and a capacitance means provided between the emitter of the transistor and the output node of the loop filter of the phase locked loop.

In this case, the distortion correction voltage is superimposed on the oscillation frequency control voltage of the voltage controlled oscillator by the emitter follower type transistor and the capacitance means. Thereby, the frequency of the read clock can be controlled based on the distortion correction waveform with a simple circuit configuration.

(17) Seventeenth Invention An image distortion correction device according to a seventeenth invention is a ninth, a twelfth invention.
In the configuration of the image distortion correction device according to any one of the fifteenth invention, the phase-locked loop divides a read clock output from the voltage-controlled oscillator, and a phase of an output signal of the divider. The read clock control means further includes a phase comparator that compares the phases of predetermined reference signals, and a loop filter that smoothes the output voltage of the phase comparator.
The addition means includes addition means for adding the distortion correction voltage output by the distortion correction waveform generation means and the output voltage of the loop filter of the phase locked loop and giving it to the voltage controlled oscillator.

In this case, the distortion correction voltage and the output voltage of the loop filter of the phase locked loop are added and given to the voltage controlled oscillator. Since the adding means is interposed between the distortion correction voltage and the loop filter, the distortion correction waveform is superimposed on the read clock without being distorted by the effect of the loop filter. Thereby, the frequency of the read clock can be controlled based on the distortion correction waveform.

(18) Eighteenth invention An image distortion correction method according to an eighteenth invention is an image distortion correction method for correcting distortion of an image displayed on a screen by a reciprocal deflection method based on a video signal. , A step of generating a write clock for writing the input video signal to the storage means, a step of generating a read clock for reading the video signal stored in the storage means, and displaying on a screen based on the video signal Generating a distortion correction waveform for correcting the distortion of the image by moving the position of the pixel, the step of controlling the frequency of the read clock based on the generated distortion correction waveform, and the horizontal scanning direction. The amount of pixel movement becomes zero at both ends and the center of the image, and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan And images are those comprising the step of setting the distortion correction waveform so as not to shift in the horizontal scanning direction.

In the image distortion correction method according to the present invention,
The video signal input in response to the write clock is written in the storage means, and the video signal stored in the storage means is read in response to the read clock. At this time, the frequency of the read clock is controlled based on the distortion correction waveform, and the read cycle of the video signal from the storage means changes. As a result, the positions of the pixels displayed on the screen are moved by the reciprocal deflection method based on the video signal, and the image distortion is corrected.

In this case, the amount of pixel movement is 0 at both ends and the center of the image in the horizontal scanning direction, and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. Since the distortion correction waveform is set so as not to shift in the horizontal scanning direction, the positions of both ends and the center of the image do not shift, and the shift of the image does not occur in the forward scan and the backward scan.

As described above, the image distortion can be corrected by changing the read clock using the distortion correction waveform without changing the deflection current in the deflection system, so that the power consumption does not increase. Further, since it is possible to correct the image distortion by generating the distortion correction waveform and controlling the read clock based on the distortion correction waveform without improving the deflection system, the circuit configuration does not become complicated and the cost is reduced. Is not disturbed.

(19) 19th Invention The image distortion correction method according to the 19th invention is the image distortion correction method according to the 18th invention, wherein the step of generating the distortion correction waveform is twice the horizontal scanning period. Generating a first correction waveform having a first portion which changes in a cycle and corresponds to a forward scan and a second portion which corresponds to a backward scan, and a second correction which changes in a vertical scanning cycle. A waveform generating step; and a step of obtaining a distortion correction waveform by modulating the first correction waveform with a second correction waveform,
The part and the second part have symmetry on the time axis.

In this case, the first correction waveform having the first portion corresponding to the forward scanning and the second portion corresponding to the backward scanning, which changes at a period twice the horizontal scanning period, is vertically scanned. A distortion correction waveform is obtained by modulating with a second correction waveform that changes in a cycle. As a result, when the deviation in the horizontal scanning direction between the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan is corrected in the reciprocating deflection type deflection system, it is displayed on the screen. The image distortion can be corrected over the entire image that is displayed.

(20) Twentieth Invention The image distortion correction method according to the twentieth invention is the image distortion correction method according to the eighteenth invention, wherein the step of generating the distortion correction waveform is twice the horizontal scanning period. Generating a first correction waveform having a first portion which changes in a cycle and corresponds to a forward scan and a second portion which corresponds to a backward scan, and a second correction which changes in a vertical scanning cycle. A step of generating a waveform, a step of modulating the first correction waveform with a second correction waveform, and a horizontal direction between the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. And a step of generating a third correction waveform for correcting the shift in the scanning direction, and a step of obtaining a distortion correction waveform by combining the modulated first correction waveform and the generated third correction waveform. , Generated first The correction waveform,
The amount of pixel movement is 0 at both ends and the center of the image in the horizontal scanning direction, and the image displayed on the screen by the forward scanning and the image displayed on the screen by the backward scanning are displaced in the horizontal scanning direction. It is corrected based on the third correction waveform so as not to exist.

In this case, the vertical scanning is performed with the first correction waveform which changes at a period twice the horizontal scanning period and has the first portion corresponding to the forward scanning and the second portion corresponding to the backward scanning. A distortion correction waveform is obtained by modulating with a second correction waveform that changes in a cycle. As a result, distortion occurs in the horizontal deflection current generated in the reciprocating deflection type deflection system, and the horizontal scanning direction of the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. Even if a shift occurs, the image distortion can be corrected over the entire image displayed on the screen.

(21) Twenty-first Invention An image distortion correction method according to a twenty-first invention is the image distortion correction method according to the twentieth invention, wherein the third method is based on temperature fluctuation.
Based on the step of correcting the third correction waveform generated by the correction waveform generating means, and the corrected third correction waveform, the pixel movement amount becomes 0 at both ends and the center of the image in the horizontal scanning direction. And a step of correcting the first correction waveform so that the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction. It is a thing.

In this case, the third correction waveform is corrected based on the temperature fluctuation, and the pixel movement amount becomes 0 at both ends and the center of the image in the horizontal scanning direction based on the corrected third correction waveform. The first correction waveform is corrected so that the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction.

As a result, even if the temperature fluctuates,
The image distortion is corrected without causing the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan to shift in the horizontal scanning direction.

(22) 22nd Invention The image distortion correction method according to the 22nd invention is the 19th to 21st inventions.
In the image distortion correction method according to any one of the inventions,
The correction waveform of corresponds to the change in the frequency of the read clock, and when the scanning direction is a positive pixel movement amount on the screen at the time of the forward scan in which the scanning is performed from left to right, the left edge of the screen is
The pixel movement amount becomes 0 at the center and the right end, the pixel movement amount changes in the order of 0, positive, 0, negative, and 0 between the left end and the center, and the pixel movement amount becomes between the center and the right end. 0, negative,
0, positive, and 0, and when the scan direction on the screen is positive when the pixel movement amount is positive when scanning in the backward direction in which the scanning is performed from right to left, the pixel movement amount at the right edge, center, and left edge of the screen. Becomes 0, and the amount of pixel movement between the right end and the center is 0,
It is set to change in the order of positive, 0, negative and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive and 0, and the second correction waveform is The upper and lower ends in the vertical direction are set to have a larger amplitude than the central part.

When the inner pincushion distortion is generated by the left and right pincushion distortion correction, a vertical line at an intermediate portion between the left and right ends and the center of the plurality of vertical lines displayed on the screen is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the positions of the pixels above and below the vertical line in the middle part inward.

(23) 23rd Invention The image distortion correction method according to the 23rd invention is the 19th to 21st inventions.
In the image distortion correction method according to any one of the inventions,
The correction waveform of corresponds to the change in the frequency of the read clock, and when the scanning direction is a positive pixel movement amount on the screen at the time of the forward scan in which the scanning is performed from left to right, the left edge of the screen is
The pixel movement amount becomes 0 at the center and the right end, the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and the pixel movement amount becomes between the center and the right end. 0, positive,
When the scan direction on the screen is positive with respect to the pixel movement amount during the backward scan in which the scanning direction changes from 0, negative, and 0, and the scanning is performed from right to left, the pixel movement amount at the right edge, center, and left edge of the screen. Becomes 0, and the amount of pixel movement between the right end and the center is 0,
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0. The amplitude is set to be larger at the central portion in the vertical direction than that at the upper and lower ends.

When the inner pincushion distortion is generated by the left and right pincushion distortion correction, among the plurality of vertical lines displayed on the screen, the vertical line in the middle between the left and right ends and the center is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the position of the pixel at the center of the vertical line in the middle part to the outside.

(24) 24th Invention An image distortion correcting method according to a 24th invention is the 18th to 23rd inventions.
In the image distortion correction method according to any one of the present inventions, the step of generating a read clock includes the step of generating a read clock by a phase locked loop having a voltage controlled oscillator, and the step of generating a distortion correction waveform The step of controlling the frequency of the read clock includes the step of outputting the distortion correction waveform as a distortion correction voltage, and the step of superposing the output distortion correction voltage on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop. It includes.

In this case, the distortion correction voltage is superimposed on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop, so that the frequency of the read clock changes. As a result, the read cycle of the video signal read from the storage means changes, and the position of the pixel displayed on the screen moves based on the video signal, whereby the image distortion is corrected.

(25) 25th Invention An image distortion correction method according to the 25th invention is the 19th to 21st inventions.
An image distortion correction method according to any one of the inventions,
The correction waveform of corresponds to the change in the cycle of the read clock, and when the scanning direction is a positive pixel movement amount on the screen at the time of the forward scanning in which the scanning is performed from the left to the right,
The pixel movement amount becomes 0 at the center and the right end, the pixel movement amount changes in the order of 0, positive, 0, negative, and 0 between the left end and the center, and the pixel movement amount becomes between the center and the right end. 0, negative,
0, positive, and 0, and when the scan direction on the screen is positive when the pixel movement amount is positive when scanning in the backward direction in which the scanning is performed from right to left, the pixel movement amount at the right edge, center, and left edge of the screen. Becomes 0, and the amount of pixel movement between the right end and the center is 0,
It is set to change in the order of positive, 0, negative and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive and 0, and the second correction waveform is The upper and lower ends in the vertical direction are set to have a larger amplitude than the central part.

When the inner pincushion distortion is generated by the left and right pincushion distortion correction, the vertical line in the middle portion between the left and right ends and the center among the plurality of vertical lines displayed on the screen is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the positions of the pixels above and below the vertical line in the middle part inward.

(26) 26th Invention An image distortion correction method according to the 26th invention is the 19th to 21st inventions.
An image distortion correction method according to any one of the inventions,
The correction waveform of corresponds to the change in the cycle of the read clock, and when the scanning direction is a positive pixel movement amount on the screen at the time of the forward scanning in which the scanning is performed from left to right, the left edge of the screen is
The pixel movement amount becomes 0 at the center and the right end, the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and the pixel movement amount becomes between the center and the right end. 0, positive,
When the scan direction on the screen is positive with respect to the pixel movement amount during the backward scan in which the scanning direction changes from 0, negative, and 0, and the scanning is performed from right to left, the pixel movement amount at the right edge, center, and left edge of the screen. Becomes 0, and the amount of pixel movement between the right end and the center is 0,
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0. The amplitude is set to be larger at the central portion in the vertical direction than that at the upper and lower ends.

When the inner pincushion distortion is generated by the left and right pincushion distortion correction, the vertical line in the middle portion between the left and right ends and the center among the plurality of vertical lines displayed on the screen is curved inward. In this case, it is possible to correct the inner pincushion distortion by moving the position of the pixel at the center of the vertical line in the middle part to the outside.

(27) 27th Invention The image distortion correction method according to the 27th invention is the image distortion correction method according to the 25th or 26th invention, wherein the step of generating a read clock is a voltage control type. A step of generating a read clock by a phase locked loop having an oscillator, and a step of generating a distortion correction waveform includes a step of converting the distortion correction waveform into a distortion correction voltage corresponding to a change in the frequency of the read clock and outputting the voltage. The step of controlling the frequency of the read clock includes the step of superposing the output distortion correction voltage on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop.

In this case, the distortion correction voltage is superimposed on the oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop, so that the frequency of the read clock changes. As a result, the read cycle of the video signal read from the storage means changes, and the position of the pixel displayed on the screen moves based on the video signal, whereby the image distortion is corrected.

(28) 28th Invention An image distortion correction method according to a 28th invention is the image distortion correction method according to the 24th or 27th invention, wherein the distortion correction voltage in each horizontal scanning period of the video signal is corrected. The method further comprises the step of adding a correction pulse to the distortion correction voltage in the horizontal blanking period so that the average value of (1) becomes a predetermined value.

In this case, since the average value of the oscillation frequency control voltage of the voltage controlled oscillator becomes a predetermined value in each horizontal scanning period of the video signal, the average value of the frequency of the read clock generated by the voltage controlled oscillator is constant. Becomes In this way, the operation of the phase locked loop does not change by preventing the average value of the oscillation frequency control voltage of the voltage controlled oscillator from changing before and after the distortion correction voltage is superimposed.

(29) Twenty-ninth Invention An image distortion correction method according to a twenty-ninth invention is the image distortion correction method according to the twenty-eighth invention, wherein the step of adding a correction pulse is performed every horizontal scanning period. It includes a step of adding a correction pulse to the distortion correction voltage before the phase comparison time of the phase locked loop in the horizontal blanking period so that the average value of the distortion correction voltage becomes a predetermined value.

[0077]

BEST MODE FOR CARRYING OUT THE INVENTION (1) First Embodiment FIG. 1 is a block diagram showing the configuration of an image display device according to a first embodiment of the present invention.

The image display device shown in FIG. 1 includes a video signal processing circuit 100, a color signal reproducing circuit 200, and a sync signal separating circuit 30.
0, CRT (cathode ray tube) 400, horizontal deflection circuit 500, and vertical deflection circuit 600. A horizontal deflection coil LH and a vertical deflection coil LV are attached to the CRT 400.

The video signal processing circuit 100 separates the luminance signal and the color difference signal from the video signal and outputs the video signal and supplies the video signal to the sync signal separation circuit 300. The color signal reproduction circuit 200 reproduces a color signal from the luminance signal and the color difference signal output from the video signal processing circuit 100, and the CRT 4
00 as a display signal C. Sync signal separation circuit 30
0 extracts the horizontal synchronizing signal HD and the vertical synchronizing signal VD from the video signal supplied from the video signal processing circuit 100.

As will be described later, the video signal processing circuit 100
Includes an image distortion correction device that corrects inner pincushion distortion.

The horizontal deflection circuit 500 synchronizes with the CR in synchronization with the horizontal synchronizing signal HD output from the video signal processing circuit 100.
At T400, a triangular wave-shaped horizontal deflection current IH is supplied to the horizontal deflection coil LH to reciprocally deflect the electron beam in the horizontal scanning direction.

As described above, in the reciprocating deflection method, since the horizontal deflection coil LH equivalently has an inductance component and a resistance component connected in series to it, the forward scan (hereinafter referred to as trace). The position of the pixel in and the position of the pixel in the backward scan (hereinafter referred to as retrace) shift in the horizontal scanning direction. In the present embodiment, as will be described later, the horizontal deflection circuit 500 has a function of correcting the positional deviation of pixels in the horizontal scanning direction during tracing and retracing.

Hereinafter, the positional deviation of pixels in the horizontal scanning direction during tracing and retrace will be referred to as T / R deviation.

The vertical deflection circuit 600 synchronizes with the vertical synchronization signal VD and the horizontal synchronization signal HD output from the video signal processing circuit 100, and a stepwise vertical deflection current IV for vertically deflecting the electron beam in the CRT 400. To the vertical deflection coil LV.

In the following description, tracing is performed by moving the electron beam from left to right on the screen,
Retrace shall be performed by moving the electron beam from right to left on the screen.

FIG. 2A is a waveform diagram of the vertical deflection current IV supplied to the vertical deflection coil LV by the vertical deflection circuit 600, and FIG. 2B is a horizontal deflection current supplied to the horizontal deflection coil LH by the horizontal deflection circuit 500. It is a wave form diagram of deflection current IH. In FIG. 2, 1V indicates 1 vertical scanning period, and 1H
Indicates one horizontal scanning period.

As shown in FIG. 2A, the vertical deflection current I
V changes stepwise within one vertical scanning period. Figure 2
As shown in (b), the horizontal deflection current IH changes in a triangular wave shape at a cycle twice as long as one horizontal scanning period.

FIG. 3 shows T / R in the horizontal deflection circuit 500.
FIG. 4 is an equivalent circuit diagram for explaining the deviation correction method, and FIG. 4 is a waveform diagram showing the operation of the equivalent circuit of FIG.

As shown in FIG. 3, the horizontal deflection coil LH
Includes an inductance component Lh and a resistance component Rh. A square wave voltage V1 is applied to one end 501 of the horizontal deflection coil LH. A negative resistor 503 is connected to the other end 502 of the horizontal deflection coil LH. The negative resistance 503 has a negative resistance component -Rh that cancels the resistance component Rh of the horizontal deflection coil LH. Since the inductance component Lh of the horizontal deflection coil LH is large, the horizontal deflection current IH flowing through the other end 502 has a triangular waveform.

When the negative resistance 503 is not provided, the resistance component Rh of the horizontal deflection coil LH causes distortion in the horizontal deflection current having a triangular waveform, as shown in FIG. 4B. As a result, the time point t3 when the horizontal deflection current becomes 0 during tracing deviates from the midpoint of the trace period, and the time point t4 when the horizontal deflection current becomes 0 during retrace deviates from the midpoint of the retrace period. As a result, T / R shift occurs.

In the example of FIG. 3, the negative resistance component -Rh of the negative resistance 503 cancels out the resistance component Rh of the horizontal deflection coil LH, and as shown in FIG. Electric current is obtained. As a result, the time t1 when the horizontal deflection current becomes 0 during tracing coincides with the midpoint of the trace period, and the time t2 when the horizontal deflection current becomes 0 during retrace coincides with the midpoint of the retrace period. Also,
The horizontal deflection current changes linearly during tracing and retrace, and the change during trace and the change during retrace are symmetrical to each other. As a result, no T / R shift occurs.

The T / R in the horizontal deflection circuit 500
The method of correcting the deviation is not limited to the example of FIG.
Other methods that can obtain the horizontal deflection current of

FIG. 5 is a block diagram showing an example of the configuration of an image distortion correction device included in the video signal processing circuit of the image display device of FIG.

The image distortion correction device of FIG. 5 includes a line memory 1, a write side PLL (phase locked loop) circuit 2, a read side PLL circuit 3, an inner pincushion distortion correction voltage generation circuit 4 and an addition coupling method circuit 6. . The write side PLL circuit 2 includes a phase comparator 21, a loop filter 22, a VCO (voltage controlled oscillator) 23, and a frequency divider 24. Similarly, the read side PLL circuit 3 includes a phase comparator 31, a loop filter 32, a VCO 33, and a frequency divider 34.

Phase comparator 21 of write-side PLL circuit 2
Is supplied with a horizontal synchronizing signal HD synchronized with the video signal VDI. The phase comparator 21 gives a voltage according to the phase difference between the horizontal synchronizing signal HD and the output signal of the frequency divider 24 to the VCO 23 as a control voltage via the loop filter 22. V
The CO 23 gives an output signal having a frequency according to the control voltage to the line memory 1, the frequency divider 24 and the inner pincushion distortion correction voltage generating circuit 4 as a write clock WCK. The frequency divider 24 uses the write clock WCK.
And the output signal is given to the phase comparator 21 as a phase comparison signal with the horizontal synchronizing signal HD, and the phase comparator 31 and the inner pincushion distortion correction voltage of the reading side PLL circuit 3 are used as the reading side reference signal CKS. It is given to the generation circuit 4.

The inner pincushion distortion correction voltage generating circuit 4 operates to write the write clock WCK and the reference signal CKS.
The inner pincushion distortion correction voltage VA is generated based on

Phase comparator 31 of PLL circuit 3 on the reading side
Gives a voltage according to the phase difference between the reference signal CKS and the output signal of the frequency divider 34 to the loop filter 32. The loop filter 32 smoothes the voltage given from the phase comparator 31. The output voltage of the loop filter 32 is given to the summing coupling type circuit 6. The addition coupling system circuit 6 superimposes the inner pincushion distortion correction voltage VA generated by the inner pincushion distortion correction voltage generation circuit 4 on the output voltage of the loop filter 32, and sets it as VC as a control voltage VC.
Give to O33. The VCO 33 supplies the read clock RCK having a frequency according to the control voltage VC to the line memory 1 and the frequency divider 34. The frequency divider 34 frequency-divides the read clock RCK and supplies the output signal to the phase comparator 31.

The line memory 1 has a write clock W.
The digital video signal VDI is written in response to CK. The digital video signal VDO is read from the line memory 1 in response to the read clock RCK.

During the trace period, the video signals stored in the line memory 1 are read out in the same order as when writing,
During the retrace period, the video signals stored in the line memory 1 are read out in the reverse order of the writing.

In the image distortion correction device of the present embodiment, as will be described later, the oscillation frequency of the VCO 33 is superposed by superimposing the inner pincushion distortion correction voltage VA on the control voltage of the VCO 33 in the feedback loop of the reading side PLL circuit 3. (The frequency of the read clock RCK) is modulated. Thereby, the read cycle of the video signal VDO from the line memory 1 is changed and the width of the pixel is changed. As a result, the pixel can be moved in the horizontal scanning direction, and the inner pincushion distortion can be corrected.

The output voltage of the loop filter 32 is given to the addition coupling system circuit 6, and the output voltage of the addition coupling system circuit 6 is given to the VCO 33 as the control voltage VC.

In this embodiment, the line memory 1 corresponds to the storage means, the write side PLL circuit 2 corresponds to the write clock generation means, the read side PLL circuit 3 corresponds to the read clock generation means, and the inner pin cushion. The distortion correction voltage generation circuit 4 corresponds to the distortion correction waveform generation means, and the addition coupling method circuit 6 corresponds to the distortion correction waveform superposition means.

Here, the basic principle of inner pincushion distortion correction in this embodiment will be described.

FIG. 6 is a schematic diagram for explaining the inner pincushion distortion. When vertical lines at equal intervals are displayed on the screen with left and right pincushion distortion correction by the deflection system,
As shown in FIG. 6, the vertical line at the center of the screen and the vertical lines at the left and right ends are straight lines, and the vertical lines that should be at the middle between the center of the screen and the left and right ends are curved inward. The inner pincushion distortion amount IP is the difference between the position of each pixel forming the vertical line that should be originally displayed and the position of each pixel of the curved vertical line.

As shown by the arrow x1, the inner pincushion distortion can be corrected by moving the pixels in the upper and lower parts of the vertical line on the screen inward in the horizontal scanning direction with reference to the vertical center. it can. On the contrary, it is also possible to correct the inner pincushion distortion by moving the central pixel toward the outside in the horizontal scanning direction with reference to the upper and lower ends of the vertical line.

In the following description, unless otherwise stated,
A case will be described in which the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts of the vertical line on the screen inward in the horizontal scanning direction with reference to the central part in the vertical direction.

FIG. 7 is a diagram showing an example of inner pincushion distortion correction due to movement of pixels on the screen. Figure 7
7A shows pixels on one line before the inner pincushion distortion correction, and FIG. 7B shows pixels on one line after the inner pincushion distortion correction. The cycle of the read clock RCK in FIG. 5 corresponds to the width of one pixel. FIG. 7 shows pixel movement during tracing. At the time of retrace, the horizontal time axis direction is opposite to that in the case of FIG.

In FIG. 7, pixels forming vertical lines are indicated by diagonal lines. In this case, if the cycle of the read clock RCK is increased, as shown in FIG. 7, the width of the pixel forming the vertical line changes and the pixel position changes in the horizontal time axis direction. On the screen of the CRT, since the time axis of the video signal is converted into the space axis, the pixel position changes in the horizontal scanning direction. At this time, the change in the width of the pixel is offset by the deflection distortion, and approaches the width of the pixel in the absence of the deflection distortion. In the example of FIG. 7, the width and the position are changed with 6 pixels as one unit.

FIG. 8 is a diagram showing the relationship between the amount of pixel movement in the horizontal scanning direction of the screen and the vertical position of the screen. As shown in FIG. 8, since the vertical line that should be a straight line is curved inward in the middle portion between the center and the left and right edges of the screen, the pixel movement amount is set to the minimum in the vertical center portion of the screen. , The vertical line can be corrected into a straight line by increasing the height as it approaches the upper and lower ends of the screen.

Therefore, the correction of the inner pincushion distortion consists of the correction at the horizontal rate (horizontal scanning period) and the correction at the vertical rate (vertical scanning period). That is, the inner pincushion distortion of the image can be corrected by changing the amount of change at the horizontal rate (the amount of movement of the pixels forming the vertical line) at the vertical rate.

In the image distortion correction device of FIG. 5, the read side P
The inner pincushion distortion correction voltage VA is superimposed on the control voltage applied to the VCO 33 of the LL circuit 3 to change the frequency of the read clock RCK, thereby changing the width and position of the pixel. The inner pincushion distortion correction voltage VA is obtained by modulating a horizontal rate correction waveform with a vertical rate correction waveform.

FIG. 9 shows V of the read side PLL circuit 3 of FIG.
It is a figure which shows an example of the frequency-voltage characteristic of CO33. In FIG. 9, the center voltage Vc is a voltage determined by the feedback loop of the reading side PLL circuit 3, and V
When the control voltage VC of the CO 33 is the center voltage Vc, the oscillation frequency becomes the center frequency Fc. Therefore, the frequency of the read clock RCK can be changed from the center frequency Fc by changing the control voltage VC applied to the VCO 33 of the read side PLL circuit 3 from the center voltage Vc.

For example, when the control voltage VC becomes lower than the central voltage Vc, the oscillation frequency of the VCO 33 (frequency of the read clock RCK) becomes lower than the central frequency Fc, and the width of one pixel becomes large. As a result, the displayed pixels move to the right during the trace period during which scanning is performed from left to right. In the retrace period in which scanning is performed from right to left, the displayed pixels move to the left.

FIG. 10 (a) is a waveform diagram showing an example of a horizontal rate correction waveform based on a frequency change, and FIG. 10 (b) is a waveform diagram showing an example of a pixel movement amount by the horizontal rate correction waveform. (C) is a figure which shows an example of an inner pincushion distortion amount. In FIG. 10, 1H on the horizontal axis indicates one horizontal scanning period or one horizontal scanning distance. Also,
The movement amount on the vertical axis represents the movement distance of each pixel. At this time, the movement to the right of the screen is positive.

Here, the correction waveform of the horizontal rate based on the frequency change has a waveform that changes corresponding to the frequency of the read clock RCK.

FIG. 10 shows a correction waveform of the horizontal rate based on the frequency change for one horizontal scanning period at the time of tracing. Also, the inner pincushion distortion is not always symmetrical between the left side and the right side of the screen, but in FIG.
The case where the inner pincushion distortion is symmetrical between the left side and the right side of the screen is illustrated.

In the correction at the time of tracing, in the range from the start point (the left end of the image) of the horizontal video period in the video signal to the center of the image, the cycle of the read clock RCK after correction is changed with respect to the cycle of the read clock RCK before correction. The integrated value of the amount is set to 0. This corresponds to that the pixel movement amount at the image center becomes 0 (image center does not shift).

Further, within the range from the start point (the left end of the image) to the end point (the right end of the image) of the horizontal video period in the video signal, the cycle of the read clock RCK after the correction with respect to the cycle of the read clock RCK before the correction The integrated value of the change amount of is set to 0. This corresponds to the amount of pixel movement at the right end of the image becoming 0 (the final point of the image does not shift).

However, in the above description, the period of the read clock RCK is not corrected during the horizontal blanking period (horizontal blanking period).

Therefore, as shown in FIG.
The correction waveform of the horizontal rate based on the frequency change has the center voltage Vc at the center of the image and the left and right ends. In the middle part between the left end and the center of the image, the correction waveform of the horizontal rate decreases to below the center voltage Vc and then rises, and rises above the center voltage Vc and then falls to the center voltage Vc. In the middle portion between the center of the image and the right end, the horizontal rate correction waveform rises above the center voltage Vc and then falls, and falls below the center voltage Vc and rises to the center voltage Vc. At this time, FIG.
The amount of pixel movement due to the horizontal rate correction waveform in (a) is
As shown in FIG. 10B, it becomes 0 at the center and the left and right edges of the image. By moving the pixel as shown in FIG. 10B, the inner pincushion distortion as shown in FIG. 10C can be corrected.

Next, the conditions for realizing the inner pincushion distortion correction in the reciprocating deflection method will be described.
FIG. 11 is a diagram for explaining the conditions for realizing the inner pincushion distortion correction in the reciprocating deflection method.

The upper diagram of FIG. 11 is a waveform diagram showing an example of a horizontal rate correction waveform based on the frequency change at the time of tracing and retrace, and the lower diagram is a diagram showing scanning of the screen at the time of tracing and retrace.

FIG. 11 shows a case where the inner pincushion distortion is asymmetric between the left side and the right side of the screen.

Here, in FIG. 11, the trace period is divided into four parts, and the four parts are time-sequentially A1 part, B1 part, C1.
Part and D1 part. In addition, the retrace period is divided into four, and the four parts are chronologically divided into A2 part, B2 part, C2 part, and D2 part.

In the first half of the trace period, the frequency of the read clock RCK is lowered by lowering the voltage of the correction waveform in the A1 portion below the center voltage Vc, and the read speed of the video signal from the line memory 1 is slowed down. .
This causes the pixels to move inward in the left half area of the screen. In the latter half of the trace period, the frequency of the read clock RCK is increased by increasing the voltage of the correction waveform in the C1 portion above the center voltage Vc, and the read speed of the video signal from the line memory 1 is increased. This causes the pixels to move inward in the right half area of the screen.

In the first half of the retrace period, the voltage of the correction waveform is made lower than the center voltage Vc in the A2 section, so that the frequency of the read clock RCK becomes lower and the read speed of the video signal from the line memory 1 becomes slower. . This causes the pixels to move inward in the right half area of the screen. In the second half of the retrace period, the voltage of the correction waveform is made higher than the center voltage Vc in the C2 portion, so that the frequency of the read clock RCK becomes high and the read speed of the video signal from the line memory 1 becomes fast.
This causes the pixels to move inward in the left half area of the screen.

Here, the amount of movement of each pixel on the screen due to the difference between the pre-correction period and the post-correction period of the read clock RCK is called the movement amount of each pixel. When the moving direction of each pixel by the correction is the same as the scanning direction, the moving amount of each pixel is expressed by a positive value, and when the moving direction of each pixel by the correction is opposite to the scanning direction, the moving amount of each pixel is negative. It is represented by.

In the example of FIG. 11, part A1 of the trace period,
The amount of movement of each pixel in the B1, C1, and D1 portions is positive, negative, negative, and positive, respectively. In addition, the movement amount of each pixel in the A2 portion, B2 portion, C2 portion, and D2 portion during the retrace period is positive, negative, negative, and positive, respectively.

The conditions for realizing the correction of the inner pincushion distortion in the reciprocating deflection method are as follows.

(Condition 1) The amount of pixel movement at the left and right edges of the screen due to the frequency change of the read clock RCK within one horizontal scanning period becomes zero.

(Condition 2) The pixel movement amount at the center of the screen due to the frequency change of the read clock RCK within the 1/2 horizontal scanning period becomes zero.

(Condition 3) The positions of pixels in the horizontal scanning direction are not displaced during tracing and retracing.

In order to satisfy the condition 1, the total amount of pixel movement due to the frequency change of the read clock RCK in the A1, B1, C1, and D1 portions during the trace period becomes 0, and A2 during the retrace period. Section, B2 section, C2
It is necessary that the total movement amount of the pixels due to the frequency change of the read clock RCK in the D section and the D2 section becomes zero.

In order to satisfy the condition 2, the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the A1 portion during the trace period and the pixel movement due to the frequency change of the read clock RCK in the B1 portion. And the absolute value of the total amount of movement of the pixels due to the frequency change of the read clock RCK in the C1 portion and the total amount of movement of the pixel due to the frequency change of the read clock RCK in the D1 portion Must be equal to the absolute value of. Also, the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the A2 portion during the retrace period becomes equal to the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the B2 portion. In addition, the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the C2 portion and the total absolute value of the pixel movement amount due to the frequency change of the read clock RCK in the D2 portion need to be equal. .

In order to satisfy the condition 3, the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the portion A1 in the trace period and C2 in the retrace period.
And the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the trace period becomes equal to the total absolute value of the pixel movement amount due to the frequency change of the read clock RCK It is necessary that the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the A2 portion of the period be equal. Alternatively, the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the B1 portion during the trace period and the read clock R in the D2 portion during the retrace period.
The absolute value of the total pixel movement amount due to the frequency change of CK becomes equal, and the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the trace period D1 portion and the B2 portion during the retrace period. It is necessary that the absolute value of the total amount of movement of pixels due to the frequency change of the read clock RCK is equal to.

FIG. 12 is a waveform diagram for explaining the correction waveform of the horizontal rate based on the frequency change generated in the inner pincushion distortion correction voltage generating circuit 4 of FIG. 5, and (a) shows the horizontal synchronizing signal. , (B) show horizontal rate correction waveforms based on frequency changes. 1H indicates one horizontal scanning period.

FIG. 12 shows the case where the inner pincushion distortion is asymmetric between the left side and the right side of the screen.

As shown in FIG. 12, the inner pincushion distortion correction voltage generating circuit 4 generates a correction waveform for two horizontal scanning periods including a trace period and a retrace period. The correction waveforms in the trace video period and the retrace video period satisfy the above conditions 1 and 2, respectively. Further, in order to satisfy the condition 3, the correction waveform in the trace video period and the correction waveform in the retrace video period have a bilaterally symmetric relationship on the time axis.

FIG. 13 is a waveform diagram for explaining an example of the DC component correction pulse. FIG. 13 shows a correction waveform of the horizontal rate based on the frequency change.

It should be noted that FIG. 13 and FIGS.
7 shows a correction waveform for one horizontal scanning period at the time of tracing or retrace when the inner pincushion distortion is symmetrical between the left side and the right side of the screen.

As shown in FIG. 13, the DC component of the horizontal rate correction waveform is converted into the VCO of the reading side PLL circuit 3 of FIG.
In order to match the center voltage Vc of 33, the DC component correction pulse AP is inserted in the horizontal blanking period. The polarity and level of the DC component correction pulse AP are calculated in real time based on the integrated result of the correction waveform of the horizontal rate within 1H. This DC component correction pulse AP is used for the read side P
It is inserted before the phase comparison point PC by the phase comparator 31 of the LL circuit 3 and at an arbitrary position within the horizontal blanking period.

In this case, the DC component correction pulse A is obtained by the waveforms above and below the horizontal rate correction waveform with respect to the center voltage Vc.
The correction amount to be corrected changes depending on P. The correction amount by the DC component correction pulse AP is determined by the following equation.

Correction amount = pulse width × pulse level When the pulse level of the DC component correction pulse AP is limited by the control voltage allowed in the VCO 33, it is necessary to secure the correction amount by the pulse width. Therefore, the pulse width of the DC component correction pulse AP can be set arbitrarily.
The wider the pulse width of the DC component correction pulse AP, the larger the error in the correction amount. Therefore, it is preferable to set the pulse width as narrow as possible.

Although FIG. 13 illustrates the case where the DC component correction pulse AP is inserted into the horizontal rate correction waveform based on the frequency change, the reading side is also included in the horizontal rate correction waveform based on the cycle change described later. A similar DC component correction pulse is inserted before the phase comparison point by the phase comparator 31 of the PLL circuit 3 and at an arbitrary position within the horizontal blanking period. Here, the horizontal rate correction waveform based on the cycle change has a waveform that changes corresponding to the cycle of the read clock RCK.

FIG. 14 (a) is a waveform diagram showing an example of a horizontal rate correction waveform based on a frequency change, FIG. 14 (b) is a waveform diagram showing an example of a vertical rate correction waveform, and FIG. 14 (c).
FIG. 6 is a waveform diagram showing an example of an inner pincushion distortion correction waveform based on a frequency change. FIG. 14 shows a case where the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the central part of the vertical line on the screen. However, the DC component correction pulse AP shown in FIG. 13 is not shown in FIG. In FIG. 14 (b),
1V represents one vertical scanning period.

As shown in FIG. 14A, the correction waveform of the horizontal rate based on the frequency change changes at 1H.
As shown in (b), the correction waveform of the vertical rate changes at 1V. FIG. 14 shows the correction waveform of the horizontal rate of FIG.
By modulating with the correction waveform of the vertical rate of (b), the inner pincushion distortion correction waveform based on the frequency change of FIG. 14C is obtained.

FIG. 14 (c) schematically shows the inner pincushion distortion correction waveform, and more precisely, FIG. 14 (a).
14B is amplitude-modulated by the vertical rate correction waveform of FIG. 14B.

In the vertical blanking period,
The correction waveform of the vertical rate in FIG. 14B may be a constant value. Further, the correction waveform of the horizontal rate in FIG. 14A may be a constant value near the center of the screen.

When the inner pincushion distortion is corrected by moving the central portion with the upper and lower ends of the vertical lines on the screen as a reference, the correction waveform of the horizontal rate based on the frequency change is shown in FIG. 15 (a). As described above, the waveform is opposite to that of the case of FIG. 14A with respect to the center voltage Vc. Further, as shown in FIG. 15B, the correction waveform of the vertical rate has a maximum in the central portion and becomes smaller as it gets closer to both ends. Further, as shown in FIG. 15C, the inner pincushion distortion correction waveform based on the frequency change is a waveform in which the central portion swells and converges toward both ends.

FIG. 15 (c) schematically shows the inner pincushion distortion correction waveform, and more precisely, FIG. 15 (a).
The vertical-rate correction waveform of (1) is amplitude-modulated by the vertical-rate correction waveform of FIG.

In the vertical blanking period,
The correction waveform of the vertical rate in FIG. 15B may be a constant value. Further, the correction waveform of the horizontal rate in FIG. 15A may be a constant value near the center of the screen.

FIG. 16A is a waveform diagram showing an example of a horizontal rate correction waveform based on a cycle change, FIG. 16B is a waveform diagram showing an example of a vertical rate correction waveform, and FIG. 16C is a period. It is a waveform diagram which shows an example of the inner pincushion distortion correction waveform based on a change. FIG. 16 shows a case where the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the central part of the vertical line on the screen.
However, the DC component correction pulse AP shown in FIG. 13 is not shown in FIG.

As shown in FIG. 16 (a), the horizontal rate correction waveform changes at 1H, and as shown in FIG. 16 (b),
The vertical rate correction waveform changes at 1V. Figure 16 (a)
By modulating the horizontal rate correction waveform with the vertical rate correction waveform of FIG. 16B, the inner pincushion distortion correction waveform based on the periodic change of FIG. 16C is obtained.

FIG. 16 (c) schematically shows the inner pincushion distortion correction waveform, and more precisely, FIG. 16 (a).
16B is amplitude-modulated by the vertical rate correction waveform of FIG. 16B.

In the vertical blanking period,
The vertical rate correction waveform in FIG. 16B may be a constant value. Further, the correction waveform of the horizontal rate in FIG. 16A may be set to a constant value near the center of the screen.

When the inner pincushion distortion is corrected by moving the central portion with the upper and lower ends of the vertical lines on the screen as a reference, the horizontal rate correction waveform based on the periodic change is shown in FIG. 17 (a). As described above, the waveform has an upside down waveform with respect to the center voltage Vc as compared with the case of FIG. Also,
The correction waveform of the vertical rate is as shown in FIG.
The waveform becomes maximum at the center and becomes smaller toward both ends. Further, as shown in FIG. 17C, the inner pincushion distortion correction waveform based on the periodic change is a waveform in which the central portion swells and converges toward both ends.

FIG. 17 (c) schematically shows the inner pincushion distortion correction waveform, and more precisely, FIG. 17 (a).
17B is amplitude-modulated with the correction waveform of the vertical rate shown in FIG. 17B.

In the vertical blanking period,
The correction waveform of the vertical rate in FIG. 17 (b) may be a constant value. Further, the correction waveform of the horizontal rate in FIG. 17A may be set to a constant value near the center of the screen.

When the horizontal rate correction waveform based on the periodic change shown in FIG. 16A or FIG. 17A is used, the inner pincushion distortion correction waveform based on the periodic change is used as the frequency as described later. Convert to inner pincushion distortion correction waveform based on changes.

In the examples of FIGS. 14 to 17, the inner pincushion distortion is corrected by moving the upper and lower parts with the center of the vertical line on the screen as a reference and the upper and lower ends of the screen as a reference. The case where the inner pincushion distortion is corrected by moving the center part is explained, but the inner pincushion distortion is corrected by moving the other part based on the arbitrary position of the vertical line on the screen. Good. In that case, as shown in FIG. 24, the correction waveform of the vertical rate is set so that the voltage becomes 0 at the time corresponding to the reference portion on the screen.
4, the correction waveform of the vertical rate in FIG. 15, FIG. 16 or FIG. 17 is shifted in the vertical direction, and is further folded back at the portion where the voltage becomes 0 as a boundary.

FIG. 18 is a block diagram showing a first example of the configuration of the inner pincushion distortion correction voltage generating circuit 4 of FIG.

The inner pincushion distortion correction voltage generation circuit 4 of FIG. 18 includes a horizontal rate correction waveform generation circuit 41, a vertical rate correction waveform generation circuit 42, a multiplier 43 and a DC component correction pulse superposition circuit 44.

The horizontal rate correction waveform generation circuit 41 shown in FIG.
The correction waveform VHD of the horizontal rate based on the frequency change shown in FIG. 4 (a) is generated. In this case, the horizontal rate correction waveform VHD corresponds to a change in the frequency of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3. The vertical rate correction waveform generation circuit 42 generates the vertical rate correction waveform VVD shown in FIG.

The multiplier 43 multiplies the horizontal rate correction waveform VHD generated by the horizontal rate correction waveform generation circuit 41 by the vertical rate correction waveform VVD generated by the vertical rate correction waveform generation circuit 42, and FIG. The inner pincushion distortion correction waveform VAD based on the frequency change shown in (c) is output. DC component correction pulse superposition circuit 4
Reference numeral 4 superimposes a DC component correction pulse on the inner pincushion distortion correction waveform VAD output from the multiplier 43 and outputs an inner pincushion distortion correction voltage VA. In this case, the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the center of the vertical line on the screen.

The horizontal rate correction waveform generation circuit 41 generates the horizontal rate correction waveform based on the frequency change shown in FIG. 15A, and the vertical rate correction waveform generation circuit 42 shows the horizontal rate correction waveform generation circuit 42 shown in FIG. 15B. Generate vertical rate correction waveform,
The multiplier 43 may generate the inner pincushion distortion correction waveform based on the frequency change shown in FIG.

In this case, the inner pincushion distortion is corrected by moving the central pixel with reference to the upper and lower ends of the vertical line on the screen.

In this example, the horizontal rate correction waveform generation circuit 4
1 corresponds to the first correction waveform generating means, the vertical rate correction waveform generating circuit 42 corresponds to the second correction waveform generating means,
The multiplier 43 corresponds to the modulation means or the multiplication means, and the DC component correction pulse superposition circuit 44 corresponds to the correction pulse addition means.

In the example of FIG. 18, the processing with an analog signal is described, but it is also possible to perform some or all of the circuit blocks by processing with a digital signal.

FIG. 19 is a block diagram showing a second example of the configuration of the inner pincushion distortion correction voltage generating circuit 4 of FIG.

The inner pincushion distortion correction voltage generating circuit 4 of FIG. 19 includes a horizontal rate correction waveform generating circuit 41, a vertical rate correction waveform generating circuit 42, and a variable gain amplifier 46.
And a DC component correction pulse superposition circuit 44.

The horizontal rate correction waveform generation circuit 41 shown in FIG.
The correction waveform VHD of the horizontal rate based on the frequency change shown in 4 (a) is generated and given to the input terminal of the amplifier 46.
In this case, the horizontal rate correction waveform VHD corresponds to a change in the frequency of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3. The vertical rate correction waveform generation circuit 42 generates the vertical rate correction waveform VVD shown in FIG. 14B and supplies it to the gain control terminal of the amplifier 46. As a result, the amplifier 46 becomes
The inner pincushion distortion correction waveform VAD based on the frequency change shown in (c) is output.

The DC component correction pulse superimposing circuit 44 superimposes the DC component correction pulse on the inner pincushion distortion correction waveform VAD output from the multiplier 43, and outputs the inner pincushion distortion correction voltage VA. In this case, the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the center of the vertical line on the screen.

The horizontal rate correction waveform generation circuit 41 generates the horizontal rate correction waveform based on the frequency change shown in FIG. 15A, and the vertical rate correction waveform generation circuit 42 shows the horizontal rate correction waveform. Generate vertical rate correction waveform,
The amplifier 46 may generate the inner pincushion distortion correction waveform based on the frequency change shown in FIG.

In this case, the inner pincushion distortion is corrected by moving the pixel in the center with reference to the upper and lower ends of the vertical line on the screen.

In this example, the horizontal rate correction waveform generation circuit 4
1 corresponds to the first correction waveform generating means, the vertical rate correction waveform generating circuit 42 corresponds to the second correction waveform generating means,
The amplifier 46 corresponds to the modulation means or the amplification means, and the DC component correction pulse superposition circuit 44 corresponds to the correction pulse addition means.

In the example of FIG. 19, the processing with the analog signal is described, but it is also possible to perform some or all of the circuit blocks by the processing with the digital signal.

FIG. 20 is a block diagram showing a third example of the configuration of the inner pincushion distortion correction voltage generating circuit 4 of FIG.

The inner pincushion distortion correction voltage generating circuit 4 shown in FIG. 20 includes a horizontal rate correction waveform generation circuit 47, a vertical rate correction waveform generation circuit 48, a multiplier 49, a period-frequency conversion circuit 50 and a DC component correction pulse superposition circuit. 5
Including 1.

The horizontal rate correction waveform generating circuit 47 is shown in FIG.
A horizontal rate correction waveform VHT is generated based on the cycle change shown in 6 (a). The horizontal rate correction waveform VHT is
This corresponds to a change in the cycle of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3.
The vertical rate correction waveform generation circuit 48 generates the vertical rate correction waveform VVD shown in FIG.

The multiplier 49 multiplies the horizontal rate correction waveform VHT generated by the horizontal rate correction waveform generation circuit 47 by the vertical rate correction waveform VVD generated by the vertical rate correction waveform generation circuit 48, Figure 1
The inner pincushion distortion correction waveform VAT based on the cycle change shown in 6 (c) is output.

The cycle-frequency conversion circuit 50 converts the inner pincushion distortion correction waveform VAT based on the cycle change into the inner pincushion distortion correction waveform VA based on the frequency change.
Convert to F. The DC component correction pulse superposition circuit 51 superimposes the DC component correction pulse on the inner pincushion distortion correction waveform VAF based on the frequency change obtained by the cycle-frequency conversion circuit 50, and outputs the inner pincushion distortion correction voltage VA. In this case, the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the center of the vertical line on the screen.

The horizontal rate correction waveform generation circuit 47 generates the horizontal rate correction waveform based on the period change shown in FIG. 17A, and the vertical rate correction waveform generation circuit 48 is shown in FIG. 17B. The vertical rate correction waveform may be generated, and the multiplier 49 may generate the inner pincushion distortion correction waveform based on the periodic change shown in FIG.

In this case, the inner pincushion distortion is corrected by moving the pixel in the center with reference to the upper and lower ends of the vertical line on the screen.

In this example, the horizontal rate correction waveform generation circuit 4
7 corresponds to the first correction waveform generating means, the vertical rate correction waveform generating circuit 48 corresponds to the second correction waveform generating means,
The multiplier 49 corresponds to the modulation means and the multiplication means, and the DC component correction pulse superposition circuit 51 corresponds to the correction pulse addition means.

Note that FIG. 20 describes the processing with an analog signal, but it is also possible to perform some or all of the circuit blocks by processing with a digital signal. Further, in the example of FIG. 14, instead of the multiplier 49,
An amplifier may be used, as in the example of 9.

In the inner pincushion distortion correction voltage generation circuit 4 of FIG. 20, the horizontal rate correction waveform generation circuit 4
The horizontal rate correction waveform VHT based on the cycle change generated by 7 corresponds to the change of the cycle of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3, and the cycle is proportional to the moving amount of the pixel. . Therefore, when the inner pincushion distortion correction voltage VA in each horizontal scanning line is obtained by modulating the horizontal rate correction waveform VHT with the vertical rate correction waveform VVD,
The inner pincushion distortion amount and the correction amount by the inner pincushion distortion correction voltage VA are equal in all the horizontal scanning lines, and the inner pincushion distortion can be accurately corrected over the entire screen.

On the other hand, the horizontal rate correction waveform VHD generated by the horizontal rate correction waveform generation circuit 41 of FIGS. 18 and 19 is the read clock generated by the VCO 33 of the read side PLL circuit 3. Corresponding to the frequency of RCK, the frequency is inversely proportional to the moving amount of the pixel. Therefore, the horizontal rate correction waveform VHD
When the inner pincushion distortion correction voltage VA for each horizontal scanning line is obtained by modulating the vertical rate correction waveform VVD, the inner pincushion distortion amount and the inner pincushion distortion correction voltage VA are used depending on the horizontal scanning line. A slight error occurs with the correction amount.

Therefore, when the inner pincushion distortion correction voltage generating circuit 4 of FIG. 20 is used, higher image quality can be achieved. On the other hand, when the inner pincushion distortion correction voltage generating circuit 4 of FIGS. 18 and 19 is used,
It is possible to reduce the circuit scale and cost.

The above horizontal rate correction waveform generation circuit 41,
47 and the vertical rate correction waveform generation circuits 42 and 48,
It can be composed of a memory and a D / A converter,
Alternatively, a waveform generation circuit using a waveform generation function and D /
It can also be configured by an A converter. The waveform generating circuit can be realized by hardware using a logic circuit or the like or software using a microcomputer or the like. Further, the horizontal rate correction waveform generation circuits 41 and 47 or the vertical rate correction waveform generation circuits 42 and 48 can be realized by combining these configurations.

When the inner pincushion distortion correction voltage generation circuit 4 is realized by digital processing, the horizontal rate correction waveform generation circuits 41 and 47 and the vertical rate correction waveform generation circuits 42 and 48 can be constituted by memories, or It can also be configured by a waveform generation circuit using a waveform generation function. Also in this case, the waveform generating circuit can be realized by hardware using a logic circuit or the like or software using a microcomputer or the like. Further, the horizontal rate correction waveform generation circuits 41 and 47 or the vertical rate correction waveform generation circuits 42 and 48 can be realized by combining these configurations.

FIG. 21 is a circuit diagram showing an example of the configuration of the read side PLL circuit 3 and the addition coupling system circuit 6 of FIG.

In FIG. 21, the addition coupling system circuit 6 is
Inverting adder 64, inverting amplifier 65 and non-inverting amplifier
(Voltage follower) 66 is included.

The loop filter 32 of the PLL circuit 3 on the read side has resistors 321 and 322 and capacitors 323.
It is composed of 324 and 325. In FIG. 21, the loop filter is a Lag-lead filter, but L
Other filters such as an ag filter and an active filter may be used. The loop filter 32 smoothes the output voltage of the phase comparator 31 and outputs the smoothed voltage to the node N1.

The inner pincushion distortion correction voltage VA generated by the inner pincushion distortion correction voltage generating circuit 4 of FIG. 5 is applied to one input terminal of the inverting adder 64. The output voltage of the node N1 of the loop filter 32 is given to the other input terminal of the inverting adder 64 via the non-inverting amplifier 66. The output voltage of the output terminal of the inverting adder 64 is applied to the VCO 33 as the control voltage VC via the inverting amplifier 65.

The inner pincushion distortion correction voltage VA and the output voltage of the loop filter 32 are added and inverted by the inverting adder 64, inverted by the inverting amplifier 65, and given to the VCO 33.

In the addition coupling system circuit 6 of FIG. 21,
The other input terminal of the inverting adder 64 and the loop filter 32
Since the non-inverting amplifier 66 is connected between the output node N1 and the output node N1, the inner pincushion distortion correction voltage VA is prevented from being distorted by the influence of the loop filter 32.

FIG. 22 is a block diagram showing another example of the configuration of the image distortion correction device included in the video signal processing circuit of the image display device of FIG.

The image distortion correction apparatus of FIG. 22 differs from the image distortion correction apparatus of FIG. 5 in that a capacitive coupling method circuit 5 is provided instead of the addition coupling method circuit 6 of FIG. The capacitive coupling system circuit 5 superimposes the inner pincushion distortion correction voltage VA generated by the inner pincushion distortion correction voltage generation circuit 4 on the output voltage of the loop filter 32, and gives it as a control voltage VC to the VCO 33. In the present embodiment, the capacitive coupling circuit 5 corresponds to the distortion correction waveform superimposing means.

FIG. 23 shows the PLL circuit 3 on the read side of FIG.
3 is a circuit diagram showing an example of the configuration of a capacitive coupling circuit 5; FIG.

As shown in FIG. 23, the configuration of the loop filter 32 of the read side PLL circuit 3 is similar to that shown in FIG. In FIG. 23, the loop filter is set to Lag.
Although the -lead filter is used, other filters such as a Lag filter and an active filter may be used. The loop filter 32 smoothes the output voltage of the phase comparator 31 and outputs the smoothed voltage to the VCO 33 via the node N1.
Give to.

The capacitive coupling type circuit 5 is composed of an emitter follower transistor 61, a resistor 62 and a capacitor 63. The base of the transistor 61 is supplied with the inner pincushion distortion correction voltage VA generated by the inner pincushion distortion correction voltage generating circuit 4 of FIG. 22, the collector is supplied with the power supply voltage Vcc, and the emitter is connected through the resistor 62. Grounded and capacitor 6
3 is connected to the node N1 of the loop filter 32.

In response to the inner pincushion distortion correction voltage VA, the emitter voltage of the transistor 61 changes and is applied to the node N1 via the capacitor 63. As a result, the inner pincushion distortion correction voltage VA is superimposed on the output voltage of the phase comparator 31.

Since the capacitive coupling circuit 5 of FIG. 23 is composed of a small number of parts, the cost can be reduced.

(2) Second Embodiment FIG. 25 is a block diagram showing the arrangement of an image display device according to the second embodiment of the present invention.

The image display device shown in FIG. 25 has a video signal processing circuit 100a, a color signal reproducing circuit 200, a synchronizing signal separating circuit 300, a CRT (cathode ray tube) 400, and a horizontal deflection circuit 50.
0a and vertical deflection circuit 600. A horizontal deflection coil LH and a vertical deflection coil LV are attached to the CRT 400.

The video signal processing circuit 100a includes an image distortion correction device for correcting inner pincushion distortion and T / R deviation, as described later. The horizontal deflection circuit 500a is different from the horizontal deflection circuit 500 of FIG. 1 in that it does not have a function of correcting the positional deviation of pixels in the horizontal scanning direction during tracing and retracing. Therefore, the T / R shift occurs due to the resistance component included in the horizontal deflection coil LH. In the present embodiment, the inner pincushion distortion and the T / R shift are corrected by clock modulation by the image distortion correction device included in the video signal processing circuit 100a.

The operations of the color signal reproduction circuit 200, the synchronization signal separation circuit 300 and the vertical deflection circuit 600 are the same as the operations of the color signal reproduction circuit 200, the synchronization signal separation circuit 300 and the vertical deflection circuit 600 of FIG.

FIG. 26 is a block diagram showing an example of the configuration of an image distortion correction device included in the video signal processing circuit of the image display device of FIG.

The image distortion correction device of FIG. 26 differs from the image distortion correction device of FIG. 5 in that instead of the inner pincushion distortion correction voltage generation circuit 4, a T / R deviation / inner pincushion distortion correction voltage generation circuit (hereinafter , Abbreviated as a correction voltage generating circuit) 4a. Correction voltage generation circuit 4a
Generates a T / R deviation / inner pincushion distortion correction voltage (hereinafter abbreviated as correction voltage) VA2 based on the write clock WCK and the reference signal CKS. The addition coupling system circuit 6 superimposes the inner pincushion distortion correction voltage VA2 generated by the correction voltage generation circuit 4a on the output voltage of the loop filter 32, and supplies it as the control voltage VC to the VCO 33.

The configuration of the other part of the image distortion correction device of FIG. 26 is similar to that of the image distortion correction device of FIG.

In the image distortion correction device of this embodiment, as will be described later, the oscillation frequency of the VCO 33 (read clock RCK is determined by superimposing the correction voltage VA2 on the control voltage of the VCO 33 in the feedback loop of the read side PLL circuit 3. Frequency). Thereby, the read cycle of the video signal VDO from the line memory 1 is changed and the width of the pixel is changed. as a result,
The pixel can be moved in the horizontal scanning direction, and the T / R shift and the inner pincushion distortion can be corrected.

In this embodiment, the line memory 1 corresponds to the storage means, the write side PLL circuit 2 corresponds to the write clock generation means, the read side PLL circuit 3 corresponds to the read clock generation means, and the correction voltage generation is performed. Circuit 4a
Corresponds to the distortion correction waveform generating means, and the addition coupling circuit 6 corresponds to the distortion correction waveform superposing means.

First, the basic principle of T / R deviation correction by clock modulation in this embodiment will be described. Figure 2
7 is a schematic diagram for explaining T / R deviation correction. In FIG. 27, (a) shows T for correcting the T / R shift.
/ R deviation correction waveform, (b) shows a crosshatch pattern at the time of tracing and retrace before T / R deviation correction, and (c) shows a pattern obtained by inverting the crosshatch pattern at the time of retrace on the time axis. Shown, (d) is T / R
7 shows a crosshatch combination pattern obtained by combining a crosshatch pattern at the time of tracing (b) and an inverted crosshatch pattern at the time of retracing (c) after deviation correction.

The left side of the crosshatch pattern at the time of tracing in FIG. 27B corresponds to the left side of the screen, and the right side corresponds to the right side of the screen. On the other hand, the left side of the crosshatch pattern during retrace corresponds to the right side of the screen, and the right side corresponds to the left side of the screen. Therefore, as shown in FIG. 27C, by inverting the crosshatch pattern during retrace on the time axis, the left side of the inverted crosshatch pattern corresponds to the left side of the screen and the right side corresponds to the right side of the screen. Correspond.

The horizontal deflection circuit 4 of the image distortion correction device of FIG.
00a does not have the function of correcting the T / R deviation,
Due to the resistance component of the horizontal deflection coil LH, distortion occurs in the triangular deflection horizontal deflection current as shown in FIG.

As a result, at the time of tracing, FIG.
As shown in (b), the crosshatch pattern shifts to the right on the screen. Moreover, at the time of retrace, FIG.
As shown in (c), the crosshatch pattern shifts to the left on the screen.

Therefore, as shown in FIG. 27A, the frequency of the read clock RCK is modulated by using the T / R deviation correction waveform that gradually decreases from the start time to the end time of the trace period and the retrace period. . As a result, during tracing, the crosshatch pattern is moved to the left on the screen as indicated by the arrow in FIG. 27 (b), and during retrace, the crosshatch pattern is indicated as indicated by the arrow in FIG. 27 (c). Move to the right on the screen. As a result, as shown in FIG. 27D, the crosshatch pattern at the time of tracing and the crosshatch pattern at the time of retracing match in the horizontal scanning direction.

The correction of the T / R deviation and the inner pincushion distortion consists of the correction at the horizontal rate (horizontal scanning period) and the correction at the vertical rate (vertical scanning period). That is, it is possible to correct the T / R shift of the image and the inner pincushion distortion by changing the amount of change at the horizontal rate at the vertical rate. Further, the horizontal rate correction waveform is a combination of the T / R deviation correction waveform for correcting the T / R deviation and the inner pincushion distortion correction waveform for correcting the inner pincushion distortion, and the condition described below. Is obtained by modifying the combined correction waveform so as to satisfy

Next, the conditions for realizing the correction of the T / R deviation and the inner pincushion distortion in the reciprocating deflection method will be described. FIG. 28 shows T / R in the reciprocating deflection method.
It is a figure for demonstrating the conditions 1-3 for implement | achieving correction | amendment and an inner pincushion distortion correction.

The upper part of FIG. 28 is a waveform diagram showing an example of the horizontal rate correction waveform based on the frequency change at the time of tracing and retrace, and the lower part is a diagram showing the scanning of the screen at the time of tracing and retrace.

FIG. 28 shows the case where the inner pincushion distortion is asymmetric between the left side and the right side of the screen.

Here, in FIG. 28, the trace period is divided into four parts, and the four parts are time-sequentially A1 part, B1 part, C1.
Part and D1 part. In addition, the retrace period is divided into four, and the four parts are chronologically divided into A2 part, B2 part, C2 part, and D2 part.

In the first half of the trace period, the frequency of the read clock RCK is lowered by lowering the voltage of the correction waveform in the A1 portion below the T / R shift correction waveform, and the read speed of the video signal from the line memory 1 is reduced. Will be late. This causes the pixels to move inward in the left half area of the screen. In the latter half of the trace period, the voltage of the correction waveform is made higher than that of the T / R shift correction waveform in the C1 portion, so that the frequency of the read clock RCK becomes high and the read speed of the video signal from the line memory 1 becomes high. . This causes the pixels to move inward in the right half area of the screen.

In the first half of the retrace period, the voltage of the correction waveform is made lower than that of the T / R shift correction waveform in the A2 section, so that the frequency of the read clock RCK becomes lower and the read speed of the video signal from the line memory 1 becomes faster. Will be late. This causes the pixels to move inward in the right half area of the screen. In the latter half of the retrace period, the voltage of the correction waveform is made higher than that of the T / R deviation correction waveform at the C2 portion, so that the frequency of the read clock RCK becomes high and the read speed of the video signal from the line memory 1 becomes fast. . This causes the pixels to move inward in the left half area of the screen.

Here, the amount of movement of each pixel on the screen due to the difference between the pre-correction period and the post-correction period of the read clock RCK is called the movement amount of each pixel. When the moving direction of each pixel by the correction is the same as the scanning direction, the moving amount of each pixel is expressed by a positive value, and when the moving direction of each pixel by the correction is opposite to the scanning direction, the moving amount of each pixel is negative. It is represented by.

In the example of FIG. 11, part A1 of the trace period,
The amount of movement of each pixel in the B1, C1, and D1 portions is positive, negative, negative, and positive, respectively. In addition, the movement amount of each pixel in the A2 portion, B2 portion, C2 portion, and D2 portion during the retrace period is positive, negative, negative, and positive, respectively.

Condition 1 for realizing the correction of the T / R shift and the inner pincushion distortion in the reciprocating deflection method.
~ 3 are as follows.

(Condition 1) The amount of pixel movement at the left and right edges of the screen due to the frequency change of the read clock RCK within one horizontal scanning period becomes zero.

(Condition 2) The pixel movement amount at the center of the screen due to the frequency change of the read clock RCK within the 1/2 horizontal scanning period becomes 0.

(Condition 3) The positions of pixels in the horizontal scanning direction do not shift during tracing and retracing.

In order to satisfy the condition 1, the total pixel movement amount due to the frequency change of the read clock RCK in the A1, B1, C1, and D1 portions of the trace period becomes 0, and A2 of the retrace period becomes A2. Section, B2 section, C2
It is necessary that the total movement amount of the pixels due to the frequency change of the read clock RCK in the D section and the D2 section becomes zero.

In order to satisfy the condition 2, the absolute value of the total amount of movement of the pixel due to the frequency change of the read clock RCK in the A1 portion during the trace period and the pixel value due to the frequency change of the read clock RCK in the B1 portion. The absolute value of the total movement amount becomes equal to the absolute value of the total movement amount of the pixel due to the frequency change of the read clock RCK in the C1 portion and the absolute movement amount of the pixel due to the frequency change of the read clock RCK in the D1 portion. The absolute value of the sum must be equal. Also, the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the A2 portion during the retrace period becomes equal to the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the B2 portion. ,
In addition, the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the C2 portion and the total absolute value of the pixel movement amount due to the frequency change of the read clock RCK in the D2 portion need to be equal.

In order to satisfy the condition 3, the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the portion A1 of the trace period and C2 of the retrace period.
And the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the trace period becomes equal to the total absolute value of the pixel movement amount due to the frequency change of the read clock RCK It is necessary that the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the A2 portion of the period be equal. Alternatively, the absolute value of the total amount of pixel movement due to the frequency change of the read clock RCK in the B1 portion during the trace period and the read clock R in the D2 portion during the retrace period.
The absolute value of the total pixel movement amount due to the frequency change of CK becomes equal, and the absolute value of the total pixel movement amount due to the frequency change of the read clock RCK in the trace period D1 portion and the B2 portion during the retrace period. It is necessary that the absolute value of the total amount of movement of pixels due to the frequency change of the read clock RCK is equal to.

(Condition 4) FIG. 29 is a diagram for explaining Condition 4 for realizing correction of T / R deviation and inner pincushion distortion in the reciprocating deflection method. In addition,
In FIG. 29, the T / R deviation correction waveform is shown in a simplified form.

Here, the T / R deviation correction waveform is Va (t)
And the inner pincushion distortion correction waveform is Vb (t)
Let V (t) be the combined waveform obtained by adding the T / R deviation correction waveform and the inner pincushion distortion correction waveform. Here, the T / R deviation correction waveform Va (t), the inner pincushion distortion correction waveform Vb (t), and the composite waveform V (t) are functions of the temperature t.

FIG. 29A shows the T / R deviation correction waveform Va.
(T) and inner pincushion distortion correction waveform Vb (t)
2 shows a composite waveform V (t) obtained by addition of
9 (b) is an inner pincushion distortion correction waveform Vb
(T) is shown.

As described below, the T / R deviation correction waveform Va (t) and the inner pincushion distortion correction waveform Vb
The effect of correcting the inner pincushion distortion in the combined waveform V (t) obtained by addition with (t) is not equal to the effect of correcting the inner pincushion distortion in the inner pincushion distortion correcting waveform Vb (t).

Therefore, in order to correct the T / R shift and the inner pincushion distortion, the T / R shift correction waveform Va (t) and the inner pincushion distortion correction waveform Vb.
When adding (t), it is necessary to correct the inner pincushion distortion correction waveform Vb (t) based on the T / R shift correction waveform Va (t).

The oscillation frequencies when the control voltages applied to the VCO 33 of FIG. 26 are Va (t), Vb (t), V (t) and Vc are Fa (t), Fb (t) and Fc, respectively.
(T) and Fc, the cycles of the read clock RCK are 1 / Fa (t), 1 / Fb (t) and 1 / Fa (t), respectively.
F (t) and 1 / Fc.

The reference for the inner pincushion distortion correction in the composite waveform V (t) is the T / R deviation correction waveform Va.
Since the oscillation frequency is Fa (t) corresponding to (t), the moving distance (moving amount) L (t) of the pixel by the inner pincushion distortion correction in the composite waveform V (t) is given by the following equation.

L (t) = K · {1 / F (t) −1 / Fa (t)} (1) In the above formula (1), K is a coefficient. On the other hand, since the reference for the inner pincushion distortion correction in the inner pincushion distortion correction waveform Vb (t) is the center frequency Fc of the VCO 33, the pixel of the inner pincushion distortion correction in the inner pincushion distortion correction waveform Vb (t) is corrected. The moving distance (moving amount) Lb (t) is given by the following equation.

Lb (t) = K · {1 / Fb (t) −1 / Fa (t)} (2) In the above equation (2), K is a coefficient. 1 / F (t) ≠
Since it is 1 / Fb (t), from the above equations (1) and (2), L
(T) ≠ Lb (t). That is, the composite waveform V
The pixel movement amount L (t) by the inner pincushion distortion correction at (t) is different from the pixel movement amount Lb (t) by the inner pincushion distortion correction waveform Vb (t).

Therefore, the T / R deviation correction waveform Va
(T) and inner pincushion distortion correction waveform Vb (t)
When adding and, the combined waveform V (t) becomes
The inner pincushion distortion correction waveform Vb (t) is corrected based on the T / R deviation correction waveform Va (t) so as to satisfy 3.

(Condition 5) FIG. 30 is a diagram for explaining Condition 5 for realizing the correction of T / R deviation and inner pincushion distortion in the reciprocating deflection method. In addition,
In FIG. 30, the T / R deviation correction waveform is shown in a simplified form.

FIG. 30 (a) shows the composite waveform V (t) before the level change of the T / R deviation correction waveform, and FIG. 30 (b) shows the composite waveform V (t) after the level change of the T / R deviation correction waveform. V '
(T) is shown.

Here, the T / R deviation correction waveform is Va (t)
And the inner pincushion distortion correction waveform is Vb (t)
Let V (t) be the combined waveform obtained by adding the T / R deviation correction waveform and the inner pincushion distortion correction waveform. T / R deviation correction waveform Va (t), inner pincushion distortion correction waveform Vb (t), and composite waveform V (t)
Is a function of temperature t.

When the control voltages applied to the VCO 33 in FIG. 26 are Va (t), Vb (t), V (t) and Vc, the oscillation frequencies are Fa (t), Fb (t) and Fc, respectively.
(T) and Fc, the cycles of the read clock RCK are 1 / Fa (t), 1 / Fb (t) and 1 / Fa (t), respectively.
F (t) and 1 / Fc.

The reference for the inner pincushion distortion correction in the composite waveform V (t) is the T / R deviation correction waveform Va.
Since the oscillation frequency is Fa (t) corresponding to (t), the moving distance (moving amount) L (t) of the pixel by the inner pincushion distortion correction in the composite waveform V (t) is given by the following equation.

[0249]   L (t) = K · {1 / F (t) -1 / Fa (t)} (3) In the above equation (3), K is a coefficient.

On the other hand, since the T / R deviation correction waveform Va (t) is a function of the temperature t, the level of the T / R deviation correction waveform Va (t) changes when the temperature t changes. When the level of the T / R deviation correction waveform Va (t) changes, the combined waveform V
The oscillation frequency Fa (t), which is the reference for the inner pincushion distortion correction at (t), changes. Therefore, T /
After changing the level of the R deviation correction waveform Va (t), T / R
In order to obtain the effect of correcting the inner pincushion distortion in the composite waveform V (t) as before the level of the deviation correction waveform Va (t) is changed, the inner pincushion distortion correction waveform Vb (t) is shifted by T / R. It is necessary to make corrections based on the correction waveform Va (t).

Here, the T / R deviation correction waveform after the level change is Va ′ (t), and the inner pincushion distortion correction waveform after the level change of the T / R deviation correction waveform is V ′ (t).
Let b ′ (t) be the composite waveform obtained by adding the T / R deviation correction waveform and the inner pincushion distortion correction waveform after the level change of the T / R deviation correction waveform is V ′ (t).
And

The control voltages applied to the VCO 33 shown in FIG. 26 are Va '(t), Vb' (t), V '(t) and V'.
The oscillation frequencies in the case of c ′ are Fa ′ (t) and F, respectively.
Assuming that b ′ (t), F ′ (t) and Fc ′, the cycle of the read clock RCK is 1 / Fa ′ (t),
1 / Fb '(t), 1 / F' (t) and 1 / Fc '.

The reference for the inner pincushion distortion correction in the composite waveform V '(t) is the T / R deviation correction waveform Va'.
Since the oscillation frequency Fa ′ (t) corresponds to (t),
The moving distance (moving amount) L ′ (t) of the pixel by the inner pincushion distortion correction in the composite waveform V ′ (t) is given by the following equation.

[0254]   L ′ (t) = K · {1 / F ′ (t) −1 / Fa ′ (t)} (4) In the above equation (4), K is a coefficient.

That is, in order to obtain the effect of correcting the inner pincushion distortion after the level change of the T / R deviation correction waveform, as in the case before the level change of the T / R deviation correction waveform,
It is necessary that (t) = L '(t). Therefore, it is necessary to satisfy the following expression (5) from the above expressions (3) and (4).

1 / F ′ (t) = 1 / F (t) −1 / Fa (t) + 1 / Fa ′ (t) (5) The inner pincushion distortion is satisfied so as to satisfy the above expression (5). The correction waveform Vb '(t) is corrected.

FIG. 31 is a waveform diagram for explaining the correction waveform of the horizontal rate based on the frequency change generated in the correction voltage generating circuit 4a of FIG. 26, (a) showing a horizontal synchronizing signal, and (b). Indicates a T / R deviation correction waveform,
(C) shows a horizontal rate inner pincushion distortion correction waveform based on a frequency change, and (d) is obtained by adding a T / R deviation correction waveform and a horizontal rate inner pincushion distortion correction waveform based on a frequency change. A composite waveform is shown. 1H indicates one horizontal scanning period.

FIG. 31 shows the case where the inner pincushion distortion is asymmetric between the left side and the right side of the screen.

As shown in FIG. 31, the correction voltage generating circuit 4
a generates a composite waveform for two horizontal scanning periods including a trace period and a retrace period. The horizontal rate inner pincushion distortion correction waveform in FIG. 31C is shown in FIG.
Based on the T / R shift correction waveform of (b), the combined waveform of the trace video period and the retrace video period of FIG. 31 (c) is modified so as to satisfy the above conditions 1 to 3.

FIG. 32 is a block diagram showing a first example of the configuration of the correction voltage generating circuit 4a of FIG.

The correction voltage generation circuit 4a shown in FIG. 32 includes a horizontal rate correction waveform generation circuit 41a, a vertical rate correction waveform generation circuit 42, a multiplier 43, and a DC component correction pulse superposition circuit 4
4, a T / R deviation correction waveform generation circuit 52, a T / R temperature deviation correction signal generation circuit 53, a multiplier 54 and an adder 55.

The T / R deviation correction waveform generating circuit 52 is shown in FIG.
The T / R deviation correction waveform VTR shown in 1 is generated. T /
The R temperature deviation correction signal generation circuit 53 is a T / R for correcting a deviation (T / R temperature deviation) of pixels in the horizontal scanning direction during the trace period and the retrace period due to ambient temperature fluctuations.
An R temperature deviation correction signal VVT is generated. The T / R temperature deviation correction signal VVT changes according to the ambient temperature fluctuation.
The multiplier 54 uses the T / R deviation correction waveform VTR generated by the T / R deviation correction waveform generation circuit 52 and the T / R temperature deviation correction signal VVT generated by the T / R temperature deviation correction signal generation circuit 53. Multiply the temperature-corrected T / R deviation correction waveform VTA and output it.

The horizontal rate correction waveform generation circuit 41a generates the horizontal rate correction waveform VHD based on the frequency change shown in FIG. 31C based on the temperature-corrected T / R deviation correction waveform VTA. In this case, the horizontal rate correction waveform VHD corresponds to a change in the frequency of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3. This horizontal rate correction waveform VHD is
It is corrected based on the temperature-corrected T / R deviation correction waveform VTA. The vertical rate correction waveform generation circuit 42 is shown in FIG.
The correction waveform VVD having the vertical rate shown in (b) is generated.

The multiplier 43 outputs the horizontal rate correction waveform VHD generated by the horizontal rate correction waveform generation circuit 41a.
And the vertical rate correction waveform VVD generated by the vertical rate correction waveform generation circuit 42 are multiplied to output the inner pincushion distortion correction waveform VAD based on the frequency change. The DC component correction pulse superimposing circuit 44 outputs the inner pincushion distortion correction waveform VAD output from the multiplier 43.
The DC component correction pulse is superposed on and the inner pincushion distortion correction voltage VA1 is output. The adder 55 adds the temperature-corrected T / R deviation correction waveform VTA output from the multiplier 54 and the inner pincushion distortion correction voltage VA1 output from the DC component correction pulse superimposing circuit 44, and FIG. correction voltage VA2 corresponding to the composite waveform of d)
Is output.

In this case, the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the central part of the vertical line on the screen.

The horizontal rate correction waveform generation circuit 41a
Generates a horizontal rate correction waveform similar to the horizontal rate correction waveform based on the frequency change shown in FIG. 15A, and the vertical rate correction waveform generation circuit 42 corrects the vertical rate correction waveform shown in FIG. 15B. The waveform is generated, and the multiplier 43 outputs the waveform shown in FIG.
An inner pincushion distortion correction waveform similar to the inner pincushion distortion correction waveform based on the frequency change shown in (c) may be generated.

In this case, the inner pincushion distortion is corrected by moving the pixel at the center with reference to the upper and lower ends of the vertical line on the screen.

In this example, the horizontal rate correction waveform generating circuit 4
1a corresponds to the first correction waveform generating means, the vertical rate correction waveform generating circuit 42 corresponds to the second correction waveform generating means, the multiplier 43 corresponds to the modulating means or the multiplying means, and the DC component correction pulse superimposition is performed. The circuit 44 corresponds to the correction pulse adding means. The T / R deviation correction waveform generation circuit 52 corresponds to the third correction waveform generation means, and the T / R temperature deviation correction signal generation circuit 53 and the multiplier 54 correspond to the correction waveform correction means.

In the example of FIG. 32, the processing with an analog signal is described, but it is also possible to perform some or all of the circuit blocks by processing with a digital signal.

FIG. 33 is a block diagram showing a second example of the configuration of the correction voltage generating circuit 4a shown in FIG.

The correction voltage generation circuit 4a of FIG. 33 includes a horizontal rate correction waveform generation circuit 41a, a vertical rate correction waveform generation circuit 42, a variable gain amplifier 46, a DC component correction pulse superposition circuit 44, and a T / R deviation correction waveform generation. Circuit 52, T /
An R temperature deviation correction signal generation circuit 53, a multiplier 54 and an adder 55 are included.

T / R deviation correction waveform generating circuit 52, T / R
The operations of the temperature shift correction signal generation circuit 53 and the multiplier 54 are the same as those of the T / R shift correction waveform generation circuit 52 and T / R of FIG.
The operation is the same as that of the temperature deviation correction signal generating circuit 53 and the multiplier 54.

The horizontal rate correction waveform generation circuit 41a generates the horizontal rate correction waveform VHD based on the frequency change shown in FIG. 31C based on the temperature-corrected T / R deviation correction waveform VTA, and the amplifier It is given to the input terminal of 46. In this case, the horizontal rate correction waveform VHD corresponds to a change in the frequency of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3. This horizontal rate correction waveform VHD is the temperature-corrected T / R.
It is corrected based on the shift correction waveform VTA.

The vertical rate correction waveform generation circuit 42 shown in FIG.
The correction waveform VVD having the vertical rate shown in FIG. 4B is generated and given to the gain control terminal of the amplifier 46. Thereby,
The amplifier 46 outputs the inner pincushion distortion correction waveform VAD based on the frequency change.

The DC component correction pulse superposition circuit 44 superimposes the DC component correction pulse on the inner pincushion distortion correction waveform VAD output from the amplifier 46, and outputs the inner pincushion distortion correction voltage VA1. Adder 55
Is the temperature-corrected T / R deviation correction waveform VTA output from the multiplier 54 and the inner pincushion distortion correction voltage VA1 output from the DC component correction pulse superposition circuit 44.
And are added, and the correction voltage VA2 corresponding to the combined waveform of FIG.

The horizontal rate correction waveform generation circuit 41a
Generates a horizontal rate correction waveform similar to the horizontal rate correction waveform based on the frequency change shown in FIG. 15A, and the vertical rate correction waveform generation circuit 42 corrects the vertical rate correction waveform shown in FIG. 15B. The waveform is generated and the amplifier 46 is shown in FIG.
An inner pincushion distortion correction waveform similar to the inner pincushion distortion correction waveform based on the frequency change shown in (c) may be generated.

In this case, the inner pincushion distortion is corrected by moving the pixel in the center with reference to the upper and lower ends of the vertical line on the screen.

In this example, the horizontal rate correction waveform generation circuit 4
1a corresponds to the first correction waveform generating means, the vertical rate correction waveform generating circuit 42 corresponds to the second correction waveform generating means, the amplifier 46 corresponds to the modulating means or the amplifying means, and the DC component correction pulse superimposing circuit. Reference numeral 44 corresponds to the correction pulse adding means. The T / R deviation correction waveform generation circuit 52 corresponds to the third correction waveform generation means, and the T / R temperature deviation correction signal generation circuit 53 and the multiplier 54 correspond to the correction waveform correction means.

Although the example of FIG. 33 describes processing with an analog signal, it is also possible to perform a part or all of the circuit block by processing with a digital signal.

FIG. 34 is a block diagram showing a third example of the configuration of the correction voltage generating circuit 4a of FIG.

The correction voltage generating circuit 4a of FIG. 34 includes a horizontal rate correction waveform generating circuit 47a, a vertical rate correction waveform generating circuit 48, a multiplier 49, a period-frequency conversion circuit 50, a DC component correction pulse superimposing circuit 51, and T / T. An R deviation correction waveform generation circuit 52, a T / R temperature deviation correction signal generation circuit 53, a multiplier 54 and an adder 55 are included.

T / R deviation correction waveform generating circuit 52, T / R
The operations of the temperature shift correction signal generation circuit 53 and the multiplier 54 are the same as those of the T / R shift correction waveform generation circuit 52 and T / R of FIG.
The operation is the same as that of the temperature deviation correction signal generating circuit 53 and the multiplier 54.

The horizontal rate correction waveform generation circuit 47a generates a horizontal rate correction waveform VHT based on the periodic change shown in FIG. 16 (a). Horizontal rate correction waveform VHT
Corresponds to a change in the cycle of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3. However, the correction waveform VHT of the horizontal rate is corrected based on the temperature-corrected T / R deviation correction waveform VTA. The vertical rate correction waveform generation circuit 48 is shown in FIG.
The correction waveform VVD having the vertical rate shown in (b) is generated.

The multiplier 49 has a horizontal rate correction waveform VHT generated by the horizontal rate correction waveform generation circuit 47a.
And the vertical rate correction waveform VVD generated by the vertical rate correction waveform generation circuit 48 are multiplied to obtain the inner pincushion distortion correction waveform VA based on the periodic change.
Output T.

The period-frequency conversion circuit 50 converts the inner pincushion distortion correction waveform VAT based on the period change into the inner pincushion distortion correction waveform VA based on the frequency change.
Convert to F. The DC component correction pulse superposition circuit 51 superimposes the DC component correction pulse on the inner pincushion distortion correction waveform VAF based on the frequency change obtained by the cycle-frequency conversion circuit 50, and outputs the inner pincushion distortion correction voltage VA1. The adder 55 adds the temperature-corrected T / R deviation correction waveform VTA output from the multiplier 54 and the inner pincushion distortion correction voltage VA1 output from the DC component correction pulse superimposing circuit 44 to form a combined waveform. The corresponding correction voltage VA2 is output.

In this case, the inner pincushion distortion is corrected by moving the pixels in the upper and lower parts with reference to the central part of the vertical line on the screen.

The horizontal rate correction waveform generating circuit 47a
Generates a horizontal rate correction waveform similar to the horizontal rate correction waveform based on the periodic change shown in FIG. 17A, and the vertical rate correction waveform generation circuit 48 corrects the vertical rate correction waveform shown in FIG. 17B. The waveform is generated and the multiplier 49 is shown in FIG.
An inner pincushion distortion correction waveform similar to the inner pincushion distortion correction waveform based on the periodic change shown in (c) may be generated.

In this case, the inner pincushion distortion is corrected by moving the pixel in the center with reference to the upper and lower ends of the vertical line on the screen.

In this example, the horizontal rate correction waveform generation circuit 4
7a corresponds to the first correction waveform generating means, the vertical rate correction waveform generating circuit 48 corresponds to the second correction waveform generating means, the multiplier 49 corresponds to the modulating means and the multiplying means, and the DC component correction pulse superimposition is performed. The circuit 51 corresponds to the correction pulse adding means. The T / R deviation correction waveform generation circuit 52 corresponds to the third correction waveform generation means, and the T / R temperature deviation correction signal generation circuit 53 and the multiplier 54 correspond to the correction waveform correction means.

Although FIG. 34 describes the processing with an analog signal, it is also possible to perform some or all of the circuit blocks by processing with a digital signal. Further, in the example of FIG. 34, instead of the multiplier 49,
An amplifier may be used as in the third example.

In the correction voltage generating circuit 4a of FIG. 34,
The horizontal rate correction waveform VHT based on the cycle change generated by the horizontal rate correction waveform generation circuit 47a corresponds to the change in the cycle of the read clock RCK generated by the VCO 33 of the read side PLL circuit 3, and the cycle is the pixel. Proportional to the amount of movement. Therefore, when the inner pincushion distortion correction voltage VA1 in each horizontal scanning line is obtained by modulating the horizontal rate correction waveform VHT with the vertical rate correction waveform VVD, the inner pincushion distortion amount in all the horizontal scanning lines. And the correction amount by the inner pincushion distortion correction voltage VA1 become equal, and the inner pincushion distortion can be accurately corrected over the entire screen.

On the other hand, the horizontal rate correction waveform VHD based on the frequency change generated by the horizontal rate correction waveform generation circuit 41a shown in FIGS. 32 and 33 is the read clock generated by the VCO 33 of the read side PLL circuit 3. Corresponding to the frequency of RCK, the frequency is inversely proportional to the moving amount of the pixel. Therefore, the horizontal rate correction waveform VH
When the inner pincushion distortion correction voltage VA1 for each horizontal scanning line is obtained by modulating D with the vertical rate correction waveform VVD, the inner pincushion distortion amount and the inner pincushion distortion correction voltage VA1 may be obtained depending on the horizontal scanning line. A slight error occurs between the correction amount and the correction amount.

Therefore, the correction voltage generating circuit 4 of FIG.
When a is used, higher image quality can be achieved. On the other hand, when the correction voltage generating circuit 4a shown in FIGS. 32 and 33 is used, the circuit scale can be reduced and the cost can be reduced.

The above horizontal rate correction waveform generation circuit 41
a, 47a and vertical rate correction waveform generation circuits 42, 4
8 can be composed of a memory and a D / A converter, or can be composed of a waveform generating circuit using a waveform generating function and a D / A converter. The waveform generating circuit can be realized by hardware using a logic circuit or the like or software using a microcomputer or the like. Further, the horizontal rate correction waveform generation circuits 41a and 47a or the vertical rate correction waveform generation circuits 42 and 48 can be realized by combining these configurations.

When the correction voltage generation circuit 4a is realized by digital processing, the horizontal rate correction waveform generation circuit 41a,
47a and vertical rate correction waveform generation circuits 42 and 48
Can be configured by a memory, or can be configured by a waveform generation circuit using a waveform generation function. Also in this case, the waveform generating circuit can be realized by hardware using a logic circuit or the like or software using a microcomputer or the like. Further, the horizontal rate correction waveform generation circuits 41a and 47a or the vertical rate correction waveform generation circuits 42 and 48 can be realized by combining these configurations.

Incidentally, in the image distortion correction device of FIG.
Similar to the image distortion correction device of FIG.
Instead of the above, the capacitive coupling type circuit 5 shown in FIG. 21 may be used.

In the above embodiments, the present invention is applied to the case of correcting the inner pincushion distortion, but the present invention is also applicable to the case of performing horizontal linearity correction.

[0298]

According to the present invention, the frequency of the read clock is controlled based on the distortion correction waveform to change the read cycle of the video signal from the storage means. As a result, the positions of the pixels displayed on the screen are moved by the reciprocal deflection method based on the video signal, and the image distortion is corrected. In this case, since the distortion correction waveform is set so that the pixel movement amount is 0 at both ends and the center of the image in the horizontal scanning direction, the positions of both ends and the center of the image do not shift, and the forward scan and No image shift occurs in the backward scan.

As described above, the image distortion can be corrected by changing the read clock using the distortion correction waveform without changing the deflection current in the deflection system, so that the power consumption does not increase. Further, since it is possible to correct the image distortion by providing the distortion correction waveform generation means and the read clock control means without improving the deflection system, the circuit configuration is not complicated and the cost can be reduced. To be

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image display device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a vertical deflection current supplied to a vertical deflection coil by a vertical deflection circuit and a waveform diagram of a horizontal deflection current supplied to a horizontal deflection coil by a horizontal deflection circuit.

FIG. 3 is an equivalent circuit diagram for explaining a method of correcting T / R deviation in a horizontal deflection circuit.

FIG. 4 is a waveform diagram showing the operation of the equivalent circuit of FIG.

5 is a block diagram showing an example of a configuration of an image distortion correction device included in a video signal processing circuit of the image display device of FIG.

FIG. 6 is a schematic diagram for explaining inner pincushion distortion.

FIG. 7 is a diagram showing an example of inner pincushion distortion correction due to movement of pixels on the screen.

FIG. 8 is a diagram showing the relationship between the amount of pixel movement in the horizontal scanning direction of the screen and the vertical position of the screen.

9 is a diagram showing an example of a frequency-voltage characteristic of a VCO of the read side PLL circuit of FIG.

FIG. 10 is a waveform diagram showing a horizontal rate correction waveform based on a frequency change used for inner pincushion distortion correction with reference to the center of the screen, a waveform diagram showing a pixel movement amount by the horizontal rate correction waveform, and an inner pin. Diagram showing cushion strain amount

FIG. 11 is a diagram for explaining conditions for realizing inner pincushion distortion correction in the reciprocating deflection method.

12 is a waveform chart for explaining a horizontal rate correction waveform based on a frequency change generated in the inner pincushion distortion correction voltage generation circuit of FIG.

FIG. 13 is a waveform diagram for explaining an example of a DC component correction pulse.

FIG. 14 is a waveform diagram showing an example of a horizontal rate correction waveform, a vertical rate correction waveform, and an inner pincushion distortion correction voltage based on a frequency change used for inner pincushion distortion correction with the center of the screen as a reference.

FIG. 15 is a waveform diagram showing an example of a horizontal rate correction waveform, a vertical rate correction waveform, and an inner pincushion distortion correction voltage based on a frequency change used for inner pincushion distortion correction with the upper and lower edges of the screen as a reference.

FIG. 16 is a waveform diagram showing an example of a horizontal rate correction waveform, a vertical rate correction waveform, and an inner pincushion distortion correction voltage based on a periodic change used for inner pincushion distortion correction with the center of the screen as a reference.

FIG. 17 is a waveform diagram showing an example of a horizontal rate correction waveform, a vertical rate correction waveform, and an inner pincushion distortion correction voltage based on a cycle change used for inner pincushion distortion correction with the upper and lower edges of the screen as a reference.

FIG. 18 is a block diagram showing a first example of the configuration of the inner pincushion distortion correction voltage generating circuit of FIG.

FIG. 19 is a block diagram showing a second example of the configuration of the inner pincushion distortion correction voltage generating circuit in FIG.

20 is a block diagram showing a third example of the configuration of the inner pincushion distortion correction voltage generating circuit in FIG.

FIG. 21 is a circuit diagram showing an example of the configurations of the read side PLL circuit and the addition coupling system circuit of FIG.

22 is a block diagram showing another example of the configuration of the image distortion correction device included in the video signal processing circuit of the image display device of FIG.

FIG. 23 is a circuit diagram showing an example of the configuration of a read side PLL circuit and a capacitive coupling method circuit of FIG. 22.

FIG. 24 is a waveform diagram showing an example of a vertical rate correction waveform used for inner pincushion distortion correction based on the position between the center and the upper and lower ends of the vertical line on the screen.

FIG. 25 is a block diagram showing a configuration of an image display device according to a second embodiment of the present invention.

26 is a block diagram showing an example of the configuration of an image distortion correction device included in the video signal processing circuit of the image display device of FIG. 25.

FIG. 27 is a diagram for explaining T / R deviation correction.

28] Conditions 1 to 1 for realizing correction of T / R deviation and inner pincushion distortion in the reciprocating deflection method.
Figure for explaining 3

FIG. 29 is a diagram for explaining Condition 4 for realizing the correction of T / R deviation and inner pincushion distortion in the reciprocating deflection method.

FIG. 30 is a diagram for explaining Condition 5 for realizing the correction of the T / R shift and the inner pincushion distortion in the reciprocating deflection method.

31 is a waveform chart for explaining a correction waveform of a horizontal rate based on a frequency change generated in the correction voltage generation circuit of FIG.

32 is a block diagram showing a first example of the configuration of the correction voltage generation circuit of FIG. 26.

FIG. 33 is a block diagram showing a second example of the configuration of the correction voltage generation circuit of FIG. 26.

34 is a block diagram showing a third example of the configuration of the correction voltage generation circuit in FIG.

FIG. 35 is a diagram showing an ideal display screen of reciprocating deflection and a diagram showing a display screen of reciprocating deflection with deviation.

[Explanation of symbols]

1 line memory 2 write side PLL circuit 3 read side PLL circuit 4 inner pincushion distortion correction voltage generation circuit 4a correction voltage generation circuit 5 capacitive coupling method circuit 6 summing coupling method circuit 21, 31 phase comparator 22, 32 loop filter 23, 33 VCO 24, 34 Frequency divider 41, 47, 41a, 47a Horizontal rate correction waveform generation circuit 42, 48 Vertical rate correction waveform generation circuit 43, 49 Multiplier 44, 51 DC component correction pulse superposition circuit 46 Amplifier 52 T / R Deviation correction waveform generation circuit 53 T / R temperature deviation correction signal generation circuit 54 Multiplication circuit 55 Adder 61 Transistors 62, 321, 322 Resistors 63, 323, 324, 325 Capacitor 64 Inversion adder 65 Inversion amplifier 66 Non-inversion amplifier VDI, VDO Video signal WCK Write clock RCK Read Clocks VA, VA1 Inner pincushion distortion correction voltage VA2 Correction voltage VC Control voltage CKS Reference signal HD Horizontal sync signals VHD, VHT Horizontal rate correction waveforms VVD, VVT Vertical rate correction waveforms VAD, VAT, VAF Inner pincushion distortion correction waveforms VTR, VTT T / R deviation correction waveform VTT T / R temperature deviation correction signal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideyo Kamihata             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5C021 PA18 PA31 PA54 PA82 RA13                       SA01 SA02 YC03                 5C068 AA06 BA08 BA16 HB02 JA01                       JA03 LA20

Claims (29)

[Claims] 1. An image distortion correction device for correcting the distortion of an image displayed on a screen by a reciprocal deflection method based on a video signal, the storage device storing the video signal, and the input video signal. Write clock generating means for generating a write clock for writing the data into the storage means, a read clock generating means for generating a read clock for reading the video signal stored in the storage means, and an on-screen display based on the video signal. Based on the distortion correction waveform generated by the distortion correction waveform generating means, and a distortion correction waveform generating means for generating a distortion correction waveform for correcting the distortion of the image by moving the position of the pixel displayed in A read clock control unit that controls the frequency of the read clock generated by the read clock generation unit, In the distortion correction waveform generating means, the amount of pixel movement is 0 at both ends and the center of the image in the horizontal scanning direction, and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan. An image distortion correction apparatus, wherein the distortion correction waveform is set so that and are not displaced in the horizontal scanning direction. 2. The distortion correction waveform generating means has a first portion that changes at a period twice the horizontal scanning period and that corresponds to a forward scan and a second portion that corresponds to a backward scan. A first correction waveform generating means for generating one correction waveform, and a second correction waveform generating means for generating a second correction waveform changing in a vertical scanning cycle.
Correction waveform generating means, and the first correction waveform generating means generated by the first correction waveform generating means.
Modulation means for obtaining the distortion correction waveform by modulating the correction waveform of 1. with the second correction waveform generated by the second correction waveform generating means, the first portion and the second portion. 2. The image distortion correction device according to claim 1, wherein and have symmetry on the time axis. 3. The distortion correction waveform generating means has a first portion that changes at a period twice the horizontal scanning period and that corresponds to forward scanning, and a second portion that corresponds to backward scanning. A first correction waveform generating means for generating one correction waveform, and a second correction waveform generating means for generating a second correction waveform changing in a vertical scanning cycle.
Correction waveform generating means, and the first correction waveform generating means generated by the first correction waveform generating means.
Modulation means for modulating the correction waveform of No. 2 with the second correction waveform generated by the second correction waveform generation means, and an image displayed on the screen by the forward scan and an image displayed on the screen by the backward scan. Third correction waveform generating means for generating a third correction waveform for correcting a shift in the horizontal scanning direction from the image to be displayed, the first correction waveform modulated by the modulating means, and the third correction waveform generating means. And a synthesizing unit for obtaining the distortion correction waveform by synthesizing the third correction waveform generated by the first correction waveform generation unit, the first correction waveform generated by the first correction waveform generation unit in the horizontal scanning direction. The pixel movement amount becomes 0 at both ends and the center of the image, and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction. Previous Third
2. The image distortion correction device according to claim 1, wherein the correction is made based on the third correction waveform generated by the correction waveform generating means. 4. The distortion correction waveform generation means further includes a correction waveform correction means for correcting the third correction waveform generated by the third correction waveform generation means based on a temperature variation, and the first correction waveform correction means. The correction waveform generation means, based on the third correction waveform corrected by the correction waveform correction means, has zero pixel movement amounts at both ends and the center of the image in the horizontal scanning direction.
In addition, the first correction waveform is corrected so that the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction. The image distortion correction device according to claim 3. 5. The modulating means includes the first correction waveform and the second correction waveform generated by the first correction waveform generating means.
5. The image distortion correction apparatus according to claim 2, further comprising: a multiplication unit that multiplies the second correction waveform generated by the correction waveform generation unit of 1. 6. The modulation means includes an input terminal for receiving the first correction waveform generated by the first correction waveform generation means and the second correction generated by the second correction waveform generation means. The image distortion correction device according to any one of claims 2 to 4, further comprising an amplification means having a gain control terminal for receiving a waveform. 7. The first correction waveform corresponds to a change in the frequency of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of forward scanning in which scanning is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, positive, 0, negative and 0 between the left end and the center. The pixel moving amount changes in the order of 0, negative, 0, positive and 0 between the right end and the positive direction of the moving amount of the pixel in the scanning direction on the screen at the time of the backward scan in which the scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of positive, 0, negative, and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive, and 0. 7. The image distortion correction device according to claim 2, wherein the amplitude is set to be larger at the upper and lower ends in the vertical direction of the screen as compared with the central part. 8. The first correction waveform corresponds to a change in the frequency of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of forward scanning in which scanning is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and The pixel shift amount changes in the order of 0, positive, 0, negative, and 0 between the right end and the positive direction of the pixel shift amount in the scanning direction on the screen at the time of the backward scan in which scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0, and the second correction waveform The image distortion correction device according to any one of claims 2 to 6, characterized in that the amplitude is set to be larger at the central portion of the screen in the vertical direction than at the upper and lower ends. 9. The read clock generating means includes a phase locked loop having a voltage controlled oscillator for generating the read clock, and the distortion correction waveform generating means outputs the distortion correction waveform as a distortion correction voltage, 9. The read clock control means superimposes the distortion correction voltage output by the distortion correction waveform generating means on an oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop. The image distortion correction device according to any one of 1. 10. The first correction waveform corresponds to a change in the cycle of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of forward scanning in which scanning is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, positive, 0, negative and 0 between the left end and the center. The pixel moving amount changes in the order of 0, negative, 0, positive and 0 between the right end and the positive direction of the moving amount of the pixel in the scanning direction on the screen at the time of the backward scan in which the scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of positive, 0, negative, and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive, and 0. 7. The image distortion correction device according to claim 2, wherein the amplitude is set to be larger at the upper and lower ends in the vertical direction of the screen as compared with the central part. 11. The first correction waveform corresponds to a change in the cycle of the read clock, and the forward scanning direction in which the scanning is performed from left to right makes the scanning direction a positive pixel movement amount on the screen. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and The pixel shift amount changes in the order of 0, positive, 0, negative, and 0 between the right end and the positive direction of the pixel shift amount in the scanning direction on the screen at the time of the backward scan in which scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0, and the second correction waveform The image distortion correction device according to any one of claims 2 to 6, characterized in that the amplitude is set to be larger at the central portion of the screen in the vertical direction than at the upper and lower ends. 12. The read clock generating means includes a phase locked loop having a voltage controlled oscillator for generating the read clock, and the distortion correction waveform generating means outputs the distortion correction waveform obtained by the modulating means. The read clock generation means further includes conversion means for converting into a distortion correction voltage corresponding to a change in the frequency of the read clock, wherein the read clock generation means outputs the distortion correction voltage output from the distortion correction waveform generation means to the voltage of the phase locked loop. The image distortion correction device according to claim 10 or 11, wherein the image distortion correction device is superimposed on an oscillation frequency control voltage of a controlled oscillator. 13. A correction pulse adding means for adding a correction pulse to the distortion correction voltage in the horizontal blanking period so that the average value of the distortion correction voltage in each horizontal scanning period of the video signal becomes a predetermined value. The image distortion correction device according to claim 9. 14. A correction pulse for adding a correction pulse to the distortion correction voltage obtained by the conversion means in the horizontal blanking period so that the average value of the distortion correction voltage in each horizontal scanning period of the video signal becomes a predetermined value. The image distortion correction device according to claim 12, further comprising an addition unit. 15. The correction pulse adding means is configured to perform the distortion before the phase comparison time of the phase locked loop in the horizontal blanking period so that the average value of the distortion correction voltage becomes a predetermined value for each horizontal scanning period. 15. The image distortion correction device according to claim 13, wherein the correction pulse is added to a correction voltage. 16. The phase-locked loop compares a frequency divider for dividing a read clock output from the voltage controlled oscillator with a phase of an output signal of the frequency divider and a phase of a predetermined reference signal. Further comprising a phase comparator and a loop filter for smoothing the output voltage of the phase comparator and inputting it to the voltage controlled oscillator via an output node, wherein the read clock control means is configured by the distortion correction waveform generating means. An emitter follower transistor having a base for receiving the output distortion correction voltage, and a capacitance means provided between the emitter of the transistor and the output node of the loop filter of the phase locked loop. The image distortion correction device according to any one of claims 9 and 12 to 15. 17. The phase-locked loop compares the frequency of a read clock output from the voltage-controlled oscillator with a frequency divider and the phase of the output signal of the frequency divider and the phase of a predetermined reference signal. It further comprises a phase comparator and a loop filter for smoothing the output voltage of the phase comparator, wherein the read clock control means is the distortion correction voltage output by the distortion correction waveform generating means and the phase locked loop. 16. The image distortion correction apparatus according to claim 9, further comprising: an addition unit that adds the output voltage of the loop filter to the voltage-controlled oscillator. 18. An image distortion correction method for correcting distortion of an image displayed on a screen by a reciprocating deflection method based on a video signal, wherein a write clock for generating an input video signal in a storage means is generated. The step of generating a read clock for reading the video signal stored in the storage means, and correcting the image distortion by moving the position of the pixel displayed on the screen based on the video signal. Generating a distortion correction waveform for controlling the frequency of the read clock based on the generated distortion correction waveform, and the pixel movement amount becomes 0 at both ends and the center of the image in the horizontal scanning direction. Also, the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction. Image distortion correction method characterized by comprising the step of setting the distortion correction waveform. 19. The step of generating the distortion correction waveform includes a first portion that changes at a period twice the horizontal scanning period and that corresponds to a forward scan and a second portion that corresponds to a backward scan. Generating a first correction waveform, a step of generating a second correction waveform that changes in a vertical scanning cycle, and the distortion correction by modulating the first correction waveform with the second correction waveform. 19. The method according to claim 18, further comprising: obtaining a waveform, wherein the first portion and the second portion have symmetry on a time axis. 20. The step of generating the distortion correction waveform comprises a first portion that changes at a cycle twice the horizontal scanning cycle and corresponds to a forward scan and a second portion that corresponds to a backward scan. A step of generating a first correction waveform that has, a step of generating a second correction waveform that changes in a vertical scanning cycle, a step of modulating the first correction waveform with the second correction waveform, and Generating a third correction waveform for correcting a deviation in the horizontal scanning direction between an image displayed on the screen by scanning and an image displayed on the screen by backward scanning, and the modulated first correction A step of obtaining the distortion correction waveform by synthesizing a waveform and the generated third correction waveform, wherein the generated first correction waveform includes pixels at both ends and a center of an image in a horizontal scanning direction. of Based on the third correction waveform, the movement amount becomes 0 and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction. 19. The image distortion correction method according to claim 18, wherein the image distortion correction method is performed by correcting the image distortion. 21. A step of correcting the generated third correction waveform on the basis of temperature fluctuations, and a step of correcting pixels at both ends and a center of an image in a horizontal scanning direction on the basis of the corrected third correction waveform. The first correction waveform is corrected so that the movement amount becomes 0 and the image displayed on the screen by the forward scan and the image displayed on the screen by the backward scan do not shift in the horizontal scanning direction. The image distortion correction method according to claim 20, further comprising a step. 22. The first correction waveform corresponds to a change in the frequency of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of forward scanning in which scanning is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, positive, 0, negative and 0 between the left end and the center. The pixel moving amount changes in the order of 0, negative, 0, positive and 0 between the right end and the positive direction of the moving amount of the pixel in the scanning direction on the screen at the time of the backward scan in which the scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of positive, 0, negative, and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive, and 0. 22. The image distortion correction method according to claim 19, wherein the amplitude is set to be larger at the upper and lower ends in the vertical direction of the screen as compared with the central part. 23. The first correction waveform corresponds to a change in the frequency of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of forward scanning in which scanning is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and The pixel shift amount changes in the order of 0, positive, 0, negative, and 0 between the right end and the positive direction of the pixel shift amount in the scanning direction on the screen at the time of the backward scan in which scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0, and the second correction waveform The image distortion correction method according to any one of claims 19 to 21, wherein the amplitude is set to be larger at the central portion of the screen in the vertical direction than at the upper and lower ends. 24. The step of generating the read clock includes the step of generating the read clock by a phase locked loop having a voltage controlled oscillator, and the step of generating the distortion correction waveform distorts the distortion correction waveform. Comprising the step of outputting as a correction voltage, the step of controlling the frequency of the read clock,
24. The image distortion correction method according to claim 18, further comprising the step of superimposing the output distortion correction voltage on an oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop. . 25. The first correction waveform corresponds to a change in the cycle of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of the forward scanning in which the scanning is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, positive, 0, negative and 0 between the left end and the center. The pixel moving amount changes in the order of 0, negative, 0, positive and 0 between the right end and the positive direction of the moving amount of the pixel in the scanning direction on the screen at the time of the backward scan in which the scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of positive, 0, negative, and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, negative, 0, positive, and 0. 22. The image distortion correction method according to claim 19, wherein the amplitude is set to be larger at the upper and lower ends in the vertical direction of the screen as compared with the central part. 26. The first correction waveform corresponds to a change in the cycle of the read clock, and the scanning direction is a positive pixel movement amount on the screen at the time of the forward scan in which the scan is performed from left to right. In this case, the pixel movement amount becomes 0 at the left end, the center and the right end of the screen, and the pixel movement amount changes in the order of 0, negative, 0, positive and 0 between the left end and the center, and The pixel shift amount changes in the order of 0, positive, 0, negative, and 0 between the right end and the positive direction of the pixel shift amount in the scanning direction on the screen at the time of the backward scan in which scanning is performed from right to left. In this case, the pixel movement amount is 0 at the right edge, the center, and the left edge of the screen, and the pixel movement amount is 0 between the right edge and the center.
It is set to change in the order of negative, 0, positive and 0, and the amount of pixel movement between the center and the left end is set to change in the order of 0, positive, 0, negative and 0, and the second correction waveform The image distortion correction method according to any one of claims 19 to 21, wherein the amplitude is set to be larger at the central portion of the screen in the vertical direction than at the upper and lower ends. 27. The step of generating the read clock includes the step of generating the read clock by a phase-locked loop having a voltage controlled oscillator, and the step of generating the distortion correction waveform includes converting the distortion correction waveform to the distortion correction waveform. The step of converting to a distortion correction voltage corresponding to the change of the frequency of the read clock and outputting the distortion correction voltage, the step of controlling the frequency of the read clock,
27. A step of superposing the output distortion correction voltage on an oscillation frequency control voltage of the voltage controlled oscillator of the phase locked loop.
The image distortion correction method described. 28. The method further comprising the step of adding a correction pulse to the distortion correction voltage in the horizontal blanking period so that the average value of the distortion correction voltage in each horizontal scanning period of the video signal becomes a predetermined value. The image distortion correction method according to claim 24 or 27. 29. The step of adding the correction pulse is performed before the phase comparison time of the phase locked loop in the horizontal blanking period so that the average value of the distortion correction voltage becomes a predetermined value for each horizontal scanning period. 29. The image distortion correction method according to claim 28, further comprising the step of adding the correction pulse to the distortion correction voltage.