JPH0199376A - Picture distortion correction circuit - Google Patents

Abstract

PURPOSE:To obtain accurate side pin cushion distortion correcting effect by forming a distortion correction waveform while a sliced waveform passes through an integration circuit. CONSTITUTION:Upper/lower edge of vertical sawtooth wave voltage Vst is sliced by a waveform slicing circuit 7 to be a sawtooth waveform voltage Vst' and when it is given to an integration circuit 5, it is converted into a pseudo hiperbolic waveform Vhp of vertical period and the result is fed to a horizontal amplitude modulation circuit 6. Thus, a 1st slice diode 11 is conductive during a time T1 near the start point of vertical scanning period Tv and a 2nd slice diode 14 is conductive during a time T2 near the end point of the vertical scanning period Tv. The ratio of the conduction time of the diodes 11, 14 is set freely depending on the value of resistors 9, 10, 13. As a result, nearly linear change is attained near the start and end point of the vertical scanning period and the curve is close to a hiperbolic curve and accurate SPC distortion correction is applied.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is an image distortion correction circuit that corrects shape distortion of an image of a television receiver or the like using a picture tube. The present invention relates to an image distortion correction circuit that corrects so-called side pincushion distortion (hereinafter abbreviated as S2O distortion) that does not form a straight line.

(Prior art) Conventionally, in a normal picture tube, a simple saw was used for the horizontal and vertical image deflection coils! If an attempt is made to form a raster by flowing the ripple wave tPi, the raster may not be properly rectangular, and a so-called pincushion distortion may occur, as shown by the solid line in FIG. This is noticeable when the curvature of the image receiving surface is small although the deflection angle of the picture tube is relatively large.

Let's consider what the waveform of the horizontal deflection current should be when trying to make this distortion straight, especially at the left and right ends, as shown by the broken line in FIG.

The shape of the curves at the left and right ends before this correction was already based on Fink's Te1evision Enaineeri in 1957.
ngHandbook, the distance from the deflection center of the picture tube to the image receiving surface is 11, and the distance from the center of the image receiving surface to the edge in the left and right direction is a, and assuming that the image receiving surface is a plane, the following equation is obtained. is expressed in (The horizontal direction of the picture tube surface is the X axis, and the vertical direction is the y axis) x2 /a2- y
2/l' = 1 - (1) Since this is a hyperbola, the desired correction can be achieved by modulating the horizontal deflection current in accordance with this waveform. Actually, in the case of electromagnetic deflection, the deflection current and the deflection angle are not exactly proportional, so strictly speaking, there will be some error, but the r)-p (peak-to-peak) value of the horizontal deflection sawtooth current is If modulation is performed using a hyperbola of the deflection period, the SPC distortion will be corrected to a straight line as shown by the broken line in FIG.

However, it is difficult to easily generate a hyperbolic waveform electrically. Therefore, in the past, parabolic waves, which can be easily obtained by integrating a simple sawtooth wave once, were often substituted for modulation.

For example, FIG. 9 shows such an example in the form of a Bucock diagram.

Here, 1 is a horizontal deflection output circuit, 2 is a horizontal deflection coil,
3 is a vertical deflection output circuit, 4 is a vertical deflection coil, 5 is an integration circuit, 6 is a horizontal amplitude modulation circuit, and 2.4 is attached to the neck of the picture tube (not shown), and the electron beams of the picture tube are horizontally controlled. and shall be deflected vertically.

In this way, the horizontal deflection output circuit 1 has a horizontal deflection period of 1! Ri-wave current (horizontal deflection saw 1! Ri-wave current) Iyh
is applied to the horizontal deflection coil 2, and also to the vertical deflection output circuit 3.
is the vertical deflection period saw 1! A wave current (vertical deflection sawtooth wave current) lyv is passed through the vertical deflection coil 4 to form a rectangular raster on the picture tube surface.

Furthermore, at the same time, a reference sawtooth wave voltage (vertical sawtooth wave voltage) yst with a vertical deflection period is obtained from the vertical deflection output circuit 3, and this becomes a parabolic wave voltage Vpb with a vertical period in the next integrating circuit 5.

This parabolic wave voltage Vpb is applied to a horizontal amplitude modulation circuit 6, and this horizontal amplitude modulation circuit 6 is adapted to act on the horizontal deflection output circuit 1, and the horizontal deflection sawtooth wave '7fi current Iyh is −p value is parabolic wave voltage Vpb
Modulate according to the waveform of

The method of the horizontal amplitude modulation circuit 6 includes a method in which a saturable reactor is inserted substantially in series with the horizontal deflection coil 2, and its inductance value is controlled by a parabolic wave voltage Vpb, and a method in which the horizontal amplitude modulation circuit 6 is used. Various other methods have been considered in the past, such as a method in which the circuit 6 is used as a voltage control circuit to modulate the operating power supply voltage supplied to the horizontal deflection output circuit 1 according to the waveform of the parabolic wave voltage ■pb.

(Problem to be solved by the invention) However, in any case, the parabolic wave voltage Vp
As long as the horizontal deflection sawtooth wave current Iyh is modulated with the waveform b, unlike when modulating with a hyperbola, ideal correction as shown by the broken line in FIG. 8 cannot be expected. In other words, in the case of parabolic wave modulation, even if the optimum correction result (modulation degree of deflection current) is made,
In the end, image distortion as shown by the solid line in FIG. 10 remains due to the difference from the ideal hyperbola.

This is not a serious problem in general television reception** that uses overskilling, but in recent years,
A picture tube is often used as a terminal display device for computer equipment (in such cases, even the slightest undulation of a straight line would be very unsightly, so it is much more difficult to use than a normal television receiver, etc.). Even more accurate SP
C-distortion correction is required, which poses a small problem in terms of performance in the conventional method as illustrated.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and includes a horizontal deflection circuit for horizontally deflecting a picture tube;
Also comprising a vertical deflection circuit for vertical deflection, a modulation circuit for modulating the horizontal deflection current generated by the horizontal deflection circuit, and a waveform generation circuit for generating a waveform for correcting side pincushion distortion of the vertical deflection period, In the image distortion correction circuit that applies the output waveform of the waveform generation circuit to the modulation circuit, the waveform generation circuit uses a voltage nonlinear element such as a diode, and a charging/discharging circuit of a resistor and a capacitor. After slicing only the front end part or both the front end part and the rear end part of the vertical scanning of the sawtooth voltage waveform with the vertical deflection period, the sliced waveform is passed through an integrating circuit to obtain a distortion that approximates a hyperbola. By creating a correction waveform, an image distortion correction circuit is provided in which a more accurate nid-bink distortion correction effect can be obtained.

(Embodiment) FIG. 1 shows an embodiment of an image distortion correction circuit according to the present invention.

Here, it is assumed that the parts numbered 1 to 6 have the same function as the same number 0 part in FIG. 9 above.

Moreover, 7 newly added here is a waveform slicing circuit.

In this way, the upper and lower ends of the vertical sawtooth wave voltage yst are sliced by the waveform slicing circuit 1 path 7 to become the sawtooth wave voltage V st', and this sliced sawtooth voltage yst!
When the wave voltage y st' is passed through the integrating circuit 5, it is converted into a pseudo-hyperbolic waveform Vhp with a vertical period and is applied to the horizontal amplitude modulation circuit 6.

An example of an actual circuit of this waveform slicing circuit 7 is shown in FIG.

Here, 8 is a first DC blocking capacitor, 9°, 10 is a charging/discharging resistor of the first DC blocking capacitor 8, and 11 is a first slice diode.

Further, 12 is a second DC blocking capacitor, and 13
is its discharge resistance, and 14 is a second slice diode. Further, 15 is a coupling capacitor with the next stage.

In this way, the first slice diode 11 becomes conductive for a time T1 near the start point of the vertical scanning period 7v, and the second slice diode 14 becomes conductive for a time T2 near the end point of the vertical scanning period Tv. Conduct. The conduction time ratio of each diode 11.14 is the resistance 9.10
．． It can be set freely depending on the value of 13.

That is, if the value of the resistor 9 is increased to increase the charging time constant, both times TI and T2 will increase, and if the value of the resistor 10 is decreased to increase the charging time constant during the cut-off period of the first slice diode 11, When the discharge 1u current of the DC blocking capacitor 8 is increased, the charging time T1 is also increased accordingly. Similarly, if the value of the resistor 13 is made smaller, the charging time T2 becomes longer.

As a result, as shown in FIG. 3a, the vertical sawtooth wave voltage Vat has its upper and lower ends sliced into a waveform (sawtooth wave voltage) ■st' not shown by the solid line.

And this waveform (sliced sawtooth voltage)■
st' is first passed through the integrating circuit 5 in the figure, as shown in Figure 3, when integrating the waveform of the simple vertical sawtooth voltage yst, the waveform of the parabolic wave voltage is integrated as Vpb in the same figure. A waveform is obtained, but the sliced sawtooth wave voltage v s
Integrating t' gives the waveform (pseudo-hyperbolic voltage) Vhp in the figure.
The curve changes almost linearly near the start and end points of the vertical scanning period Tv, resulting in a shape more similar to a hyperbola.

In this case, the waveform shown in Figure 3a is integrated to obtain the waveform shown in Figure 3A, so the question of the curve section at the center of the waveform (pseudo-hyperbolic voltage) Vhp and the straight section at both ends is as follows. The gradients always connect smoothly, and the waveform does not become discontinuous at this point.

By the way, if the input is a completely linear sawtooth wave and the integrating circuit operates ideally, the slicing time TI will naturally be the same.

T2 must be equal.

However, depending on how the input sawtooth wave is generated, if the slope is not a straight line and an exponential component is included, or if the integration time constant of the integrator circuit is insufficient, slicing may not occur. The output parabolic wave is distorted, resulting in a waveform with a steeper slope in the first half and a gentler slope in the second half.

In such a case, better results can be obtained by making the length of time (2) shorter than the length of time (2) during IIi. At times like this, the second
In the circuit shown in the figure, the value of time T2 can be easily reduced by increasing the value of resistor 13.

Furthermore, for this reason, depending on the conditions, even if time T2 is zero, the waveform of the sawtooth voltage VSt", which is sliced only on one side of FIG. 4 and sliced properly even at time T1, can sufficiently achieve the purpose. In such cases, only one slice circuit is required as shown in Figure 4.
The circuit configuration can be greatly simplified.

゛ As described above, when the waveform is passed through the waveform slicing circuit 7 and then integrated, the waveform near both ends of the vertical deflection period TV resembles the waveform of the parabolic wave voltage Vpb, as shown in the waveform (pseudo-hyperbolic voltage) Vhp in Figure 3. Instead of curved, it changes linearly, approaching the ideal hyperbola.

Therefore, when this waveform (pseudo-hyperbolic voltage) VhEl is applied to the horizontal amplitude modulation circuit 6, the horizontal deflection sawtooth wave current 1y
The envelope of h takes the form of a pseudo-hyperbolic voltage Vhp, and the horizontal deflection amplitude changes accordingly.

Considering this in Figure 10 above, in the case of the conventional correction using the waveform of the parabolic wave voltage Vpb, the vertical upper and lower ends are over-corrected and curve inward in the horizontal direction, but the correction waveform is transformed into a pseudo-hyperbolic curve. If the voltage Vhp is made into a pseudo-hyperbola and the changes at the ends of the vertical period are relaxed, the shape of the left and right ends of the raster will approach a correct straight line.

FIG. 5 is a block diagram showing an example of a specific circuit of the present invention. Here, the numbers 1 to 5 and 7 function similarly to the parts with the same numbers in FIG. 9 and FIG. 1, and their explanation will be omitted.

Here, 16 is a saturable reactor, and its controlled winding 16b is connected in series with the horizontal deflection coil 2. Further, the control winding 16a is supplied with a parabolic wave current of 1 hp from the voltage-current conversion circuit 17, and the voltage-current conversion circuit 1
7 is connected to the integrating circuit 5 and receives the aforementioned pseudo-hyperbolic voltage Vh.
Driven by p.

In this way, a parabolic wave current 1hp similar to the pseudo-hyperbolic voltage Vhp flows from the voltage-current conversion circuit 17 to the control winding 16a. Then, the inductance of the controlled winding 16b changes according to the waveform of the parabolic current Ihp,
Further, the peak value of the horizontal deflection sawtooth wave current 1yh flowing through the horizontal deflection coil 2 is modulated according to the change in (.

Therefore, if you do this, the horizontal deflection amplitude, as described above,
That is, the right and left ends of the raster are corrected as specified, and a correct rectangular raster is obtained.

In addition, in the case of this figure, the change in the inductance of the control a winding 16a must be correctly proportional to the waveform of the parabolic wave current 1hp. However, even if the characteristics of the saturable reactor 16 are not sufficient,
Horizontal deflection saw 1: Accurately converts the waveform Iyh into the desired waveform (pseudo-hyperbolic voltage) Vh by the means disclosed in No. 70.
It is also possible to modulate with fl.

Furthermore, FIG. 6 shows an example of another specific circuit of the present invention. Again, the parts marked with M, such as 1 to 5°7, function in the same manner as the parts with the same numbers in FIGS. 1 and 5, and their explanation will be omitted.

A characteristic feature of FIG. 6 is that a power supply voltage control circuit 18 using a transistor is employed as a means for horizontal amplitude modulation.

Here, to explain the internal circuit of this power supply voltage control circuit 18, first, 19 is a control 1NPH transistor, 20 is its base bias resistor, and 21 is a smoothing capacitor. It is modulated according to the input modulation signal (here, the modulation voltage vhp'>) and becomes a power supply voltage Eb' having a ripple of voltage Vhp', and this power supply voltage Eb' becomes the operating power supply voltage of the horizontal deflection output circuit 1.

Further, another control circuit 22 may be added to the base electrode of the control transistor 19 if necessary. this is,? By feeding back the 1tWA voltage Eb' and adjusting the base current of the υjtll transistor 19 according to this value, the DC component of the power supply voltage Eb' is made constant.

By the way, in this example, the waveform of the power supply voltage Eb', that is, the waveform of the modified pseudo-hyperbolic voltage Vhp', does not necessarily correspond to the waveform of the horizontal deflection saw 1! flowing to the horizontal deflection coil 2! Riwa type flow 1y
This does not mean that it is sufficient to match the shape of the envelope of h.

This is due to the fact that the horizontal deflection coil 2 consists of an inductance portion and a resistance valve R, as shown in FIG. In other words, when a vertically periodic current i is caused to flow through the series circuit of the inductance portion and the resistance valve R shown in FIG. On the L side, a VL waveform obtained by differentiating this with respect to time t is generated.

Therefore, if you want to flow a current with a vertical period like i through this series circuit consisting of the inductance [and the resistance R], you will have to apply a voltage of VL + VR here. The adder circuit 24 in FIG. 6 is for this purpose, and in order to add a voltage corresponding to this VL, by adding the vertical sawtooth r wave voltage VSt at an appropriate ratio, the pseudo hyperbolic voltage HP
is transformed into a voltage V hp' which is then applied through the coupling capacitor 23 to the base of the control transistor 19. As a result, the DC power supply voltage Eb is modulated by the waveform of the pseudo-hyperbolic voltage Vhp, and the voltage #Q voltage Eb
' is generated.

Therefore, as in FIG. 5, the horizontal deflection sawtooth wave current 1yh can be modulated by the pseudo-hyperbolic voltage VhD, and the SPC distortion correction which is the object of the present invention can be achieved.

(Effects of the Invention) As is clear from the above detailed explanation, according to the image distortion correction circuit of the present invention, accurate horizontal deflection SPC distortion correction can be performed with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an image distortion correction circuit according to the present invention, and FIG. 2 is a diagram showing a part of the internal circuit.
FIG. 3 is a waveform diagram in the circuit, and FIG. 4 is an example of a circuit different from FIG. 2 related to FIG. 1. FIG. 1, FIG. 5, and FIG. Block diagram for illustrating, No. 7
The figure shows the equivalent circuit of the horizontal deflection coil in the present invention and the waveform generated therein. Figure 8 is a diagram explaining the S2O distortion to be corrected by the present invention. Figure 9 is a conventional example for SPC distortion correction. 10 is a block diagram of S according to the conventional example.
It is a figure which shows the example of PC distortion correction. 1... Horizontal deflection output circuit, 2... Horizontal deflection coil,
3... Vertical i+f deflection output circuit, 4... Vertical deflection coil, 5... Integrating circuit, 6... Horizontal amplitude modulation circuit, 7
...Waveform slice circuit, 8.12...DC blocking capacitor, 9.10...Charge/discharge resistor, 11, 14...Slice diode, 13...Discharge resistor, 15, 21...Smoothing Capacitor, 1G... Saturable reactor, 17... Voltage-current conversion circuit, 18.
...Power supply voltage control circuit, 19...Control NPN transistor, 20...Base bias resistor, 22...Control circuit,
23...Coupling capacitor, 24...Additional circuit, IE
b...DC power supply voltage, Eb'...Modulated power supply voltage, Iyh...Horizontal deflection sawtooth wave current, Iyv...Vertical deflection sawtooth wave current, lpb...Parabola wave current, i...・Vertical component current of horizontal deflection coil, VSt...
Vertical sawtooth voltage, y st'...sliced saw 1! wave voltage,
v st”... Sawtooth wave voltage sliced on only one side, Vpb... Parabolic wave voltage, Vhp... Pseudo-hyperbolic voltage, V ha'... Modulation voltage (transformed pseudo-hyperbolic l111 voltage) Figure 1 Figure 2 Figure 3 Figure 5 yh

Claims (1)

[Claims] A horizontal deflection circuit for horizontally deflecting the picture tube, a vertical deflection circuit for vertically deflecting the picture tube, a modulation circuit for modulating the horizontal deflection current generated by the horizontal deflection circuit, and a side pincushion distortion of the vertical deflection period. A waveform generation circuit that generates a correction waveform, and an image distortion correction circuit that applies an output waveform of the waveform generation circuit to the modulation circuit, wherein the waveform generation circuit uses a voltage nonlinear element. , after slicing only the front end part or both the front end part and the rear end part of the vertical scanning of the sawtooth voltage waveform with the vertical deflection period, the sliced waveform is passed through an integrating circuit to approximate a hyperbola. An image distortion correction circuit characterized by generating a waveform for distortion correction.