JPS5873281A - Correction circuit for screen distortion - Google Patents

Abstract

PURPOSE:To correct pin-cushion distortion and a parallelogram distortion, by modulating a horizontal saw tooth signal with a vertical saw tooth signal, summing the result to a horizontal parabola signal and applying the summing output modulated with the vertical saw tooth signal to a vertical output circuit. CONSTITUTION:An input video signal Si is converted into a horizontal saw tooth signal TH and a vertical saw tooth siganal TV via synchronizing separation circuits 2, 3, variable phase shifter 4, and saw tooth generating circuits 5, 6. A balanced modulator 7 modulates the signal TH with the signal TV. The signal TH is applied to an integration circuit 8, where a horizontal parabola signal CP is formed. An output CE of an adder 9 and the signal TV are applied to a balanced modulator 11 to form a correction signal CA. The signal CA is summed with the signal TV at an adder 12, and a synthesized output CO is applied to a vertical output circuit 13.

Description

[Detailed Description of the Invention] Generally, vertical and horizontal pincushion distortion occurs in television receivers, so a circuit is provided to correct these screen distortions. According to John, the accuracy of installing the horizontal and vertical deflection coils, that is, the orthogonality of both deflection coils, was poor.
If there is an influence of the earth's magnetism, for example, as shown in FIG. 1, asymmetrical screen distortion with respect to the X-X axis, such as a pacific quadrilateral shape, will occur.

In ordinary television receivers, even in such cases, there is no practical effect, so correction of this asymmetric screen distortion is rarely done. In a high-grade television receiver such as a television receiver, it is necessary to correct even the above-mentioned Ili plane distortion.

Therefore, in the past, screen distortion was corrected by adjusting the mechanical positions of the horizontal deflection coil and vertical deflection coil while looking at the screen before shipping. Therefore, in this conventional method, 111m distortion was corrected. In addition to being troublesome and time-consuming to adjust, it also had the disadvantage that it could not be adjusted correctly.

Therefore, in the present invention, even such asymmetric screen distortion can be corrected purely electronically, thereby eliminating the above-mentioned drawbacks. Hereinafter, an example of the present invention will be described with reference to FIG. 2 and below for a case in which both screen distortions, ie, parallelogram distortion, which is asymmetrical screen distortion, and upper and lower bin cushion distortion, which is symmetrical screen distortion, are simultaneously corrected with a simple configuration. I will explain.

That is, the screen distortion to be corrected in this invention is the distortion shown in FIG. 2, and this screen distortion S is a combination of the top and bottom pin Currayon distortion SC shown in FIG. 3 and the parallelogram distortion SB shown in FIG. It is a synthetic product.

Therefore, in order to correct the screen distortion SA, it is sufficient to correct the upper and lower bin cushion distortions 8c and the parallelogram distortions 8B at the same time.

The upper and lower bin cushion distortion 8C is obtained by supplying a signal CC obtained by modulating a horizontally periodic parabolic wave signal (horizontal parabolic wave signal) CP with a vertical sawtooth signal TV as a correction signal to the image direct output circuit as shown in Fig. 5AK. Furthermore, the parallelogram distortion sB can be corrected by applying the concept of correcting the trapezoidal distortion (screen distortion symmetrical to the X-X axis) SD shown in FIG. In other words, the trapezoidal distortion 80 can be corrected by the correction signal CD obtained by balanced modulating the horizontal sawtooth signal TH with the vertical sawtooth signal TV, as shown in Iss diagram BK, so this correction signal CD is changed and corrected to meet the purpose. Just use it.

Figure @6 is a specific example for correcting the ll1i box distortion SA, in which the input video signal S1 supplied to the terminal 111 is supplied to the synchronization separation circuits (2) and (3)K, and the horizontal synchronization pulse is output from one side. PH is separated, and the vertical synchronization pulse PV is divided from the other. The horizontal synchronizing pulse PH is controlled by a variable phase shifter (
(described later) (4) to the sawtooth signal forming circuit (5).
)K is supplied to form a horizontal sawtooth signal TH with a horizontal period. The output of the AFC circuit may be used as the horizontal synchronizing pulse PH.

The vertical synchronization pulse pH is also a vertical sawtooth signal forming circuit (6
) is supplied to the vertical sawtooth signal TV (Figure 7D)
is formed, and this and the horizontal sawtooth signal TH are supplied to the first balanced modulator (7), from which the horizontal sawtooth signal TH is balanced-modulated with the vertical sawtooth signal TV. A first signal CD shown in FIG. 7A is output.

When the horizontal sawtooth signal T)I is balanced-modulated, the phase of the horizontal sawtooth signal TH is reversed between the first half and the second half of the vertical deflection center point (X-X41MIK: corresponding). Note that since this first signal CD is the correcting signal itself shown in FIG. 5B, the parallelogram distortion 8B shown in FIG. 1 cannot be corrected by this first signal CD.

The horizontal sawtooth signal TH is further supplied to an integrating circuit (8) to form a horizontal parabolic wave signal CP (Fig. 7B), and this horizontal parabolic wave signal CP and the iris signal CD are sent to an operational amplifier for addition ( 9) and is processed with the polarity shown in the figure. Therefore, this addition output cE is a composite signal CDI containing a horizontal parabolic wave component and a horizontal sawtooth wave component as shown in FIG. (the maximum vertical deflection point in each horizontal period) is shifted to the right side of the normal case, ie, to the rear of the horizontal period, and in the second half of the vertical period, conversely, it is shifted to the left side, ie, to the first half of the horizontal period.

However, since the phases of the horizontal parabolic wave signal Cp and the horizontal sawtooth wave signal CD included in this addition output CEK do not change even after addition, they are the same as the phases of people and B in FIG. If they are in the same phase, the upper and lower bin cushions 48C in Fig. 3 cannot be corrected depending on the horizontal parabolic wave signal CPK, and the parallelogram distortion in Fig. 1 cannot be corrected depending on the horizontal parabolic wave signal tILg1 CD. Can not. Therefore, the present invention further includes the following configuration.

That is, this addition output C, is the vertical sawtooth signal TV
The added output CE is also supplied to the second balanced modulator αυ, and the added output CE is balanced-modulated with the vertical sawtooth signal TV to form the correction signal Cm shown in FIG. 7B#c.

As a result of balanced modulation, the phase of the second half of the addition output CE is inverted, so the phase of the horizontal parabolic wave signal C in the addition output Cl is inverted between the first half and the second half of the vertical period, and the horizontal sawtooth signal CD becomes vertical. The phase remains the same during the period.

Since the upper and lower pinion distortion 8c is symmetrical with respect to the X-X axis, K for correcting this distortion 8c requires that the rear distortion correction signal has an opposite phase to the first half of the vertical period. Looking at the above correction signal Cm, the horizontal parabolic wave signal c for vertical bin cushion distortion correction included in the composite signal cDg #PK
Since the phase of p is inverted between the first half and the second half of the vertical period, first, the vertical bin cushion distortion in FIG. 2 can be corrected by this correction signal CAK.

Since the parallelogram ji1s is equivalent to a distortion in which only the second half of the trapezoidal distortion SD in FIG. 4 is inverted, in order to correct this distortion SB, the second half of the vertical period is It is necessary to invert the phase. That is, the phases of the horizontal sawtooth signals CD must be in phase. Looking at the above correction signal C, since the slope of the composite signal CDI is the same in the first half and the second half of the vertical period, the horizontal sawtooth wave signal C for parallelogram distortion correction included in the composite signal "Dlii"
The phase of D does not change during the vertical period. Therefore, since the parallelogram distortion shown in FIG. 2 can also be corrected with this correction signal CA, both the upper and lower bin cushion distortions and the parallelogram distortion can be corrected simultaneously with this correction signal CA.

This correction signal CA is applied to the adder IJ3 as shown in FIG.
It is superimposed on the vertical sawtooth signal TV at Vc, and its combined output Co (FIG. 7F) is supplied to the vertical output circuit.

The variable phase shifter (4J) mentioned above is mainly used to adjust the amount of correction of the parallelogram distortion SB.

Adjustment of the correction lid is generally performed by controlling the amplitude of the horizontal sawtooth signal TH, but when correcting the upper and lower bottle cushion distortions 8c at the same time as in the present invention, by adjusting the amplitude. 17IX71ii1
The peak point of the composite signal CDI indicating 1CK is shifted to the left or right. This shift of the peak point can also be performed by learning the phase of the horizontal sawtooth signal TH, so in this example, the correction amount is adjusted by adjusting the trap phase instead of the amplitude. .

Correction amount of upper and lower bottle cushion distortion 8c and parallelogram distortion sB
When it is desired to adjust the correction amount of k independently, k can be manually adjusted externally, for example, by the addition ratio of the operational amplifier (9).

That’s all! According to this statement 1jljK, X-
Upper and lower bin cushion distortion S, which is screen distortion symmetrical about the X axis
C and the parallelogram distortion 8B, which is an asymmetrical screen distortion, can be corrected purely electronically at the same time, so you can install the horizontal and vertical deflection coils! # Even if the degree of distortion is poor and there is no orthogonality, the distortion can be corrected by Kitir surface distortion without mechanical adjustment. Therefore, it is easy to correct the screen distortion, and
The adjustment can be made in a short time, and the accuracy of the adjustment is high.

Furthermore, when configured as shown in FIG. 6, the circuit configuration can be simpler than when configured in principle.

That is, K for correcting the screen distortion sB shown in Fig. 2 is obtained by first forming a correction signal CD using a balanced modulator to correct the trapezoidal distortion 8D shown in Fig. 4, and then applying this signal to the parallelogram distortion sB t. Therefore, this correction signal CD is further balanced-modulated to form a correction signal in which the phase of the horizontal sawtooth signal TH is constant. Then, in order to correct the vertical bottle cushion distortion 8c in Fig. 3, a correction signal Cc (Fig. 5) is formed by balanced modulation gsK, and the correction signal Cc (Fig. 5) is synthesized with the previous correction signal to obtain the A correction signal CA shown in FIG. 7E is formed.

Therefore, while this basic configuration requires at least three balanced modulators, the configuration shown in FIG. 6 can achieve the same effect by using only two balanced modulators.
The configuration can be simplified.

[Brief explanation of drawings]

1 to 4 are explanatory diagrams of screen distortion, FIG. 5 is an explanatory diagram of a one-plane distortion correction signal, FIG. 6 is a system diagram showing an example of one-plane distortion correction circuit according to the present invention, and FIG. It is a technique diagram for explaining the movement. (5), (6) are sawtooth wave signal 'ryH, TV forming circuit, 17), Oυ is a balanced modulator, (8) is an integrating circuit, (9) is an adder, 03 is a vertical output circuit, and C module. is a correction signal, and Op is a horizontal parabolic wave signal.

Claims (1)

[Claims] The horizontal sawtooth signal is balanced modulated with the vertical sawtooth signal and then added to the horizontal parabolic wave signal, and the added output is balanced modulated with the vertical sawtooth signal and supplied to the vertical output circuit to generate upper and lower bin cushion distortion. Screen distortion correction circuit designed to correct parallelogram distortion at the same time.