JPH0586114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is an image distortion correction circuit for correcting 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 pink distortion (hereinafter abbreviated as SPC distortion) that does not occur.

(Prior Art) Conventionally, in an ordinary picture tube, when an attempt was made to form a raster by passing a simple sawtooth wave current through both the horizontal and vertical deflection coils, the raster was not formed into a correct rectangular raster, as shown by the solid line in Figure 3. may exhibit so-called pincushion distortion. 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 curve at the left and right ends before this correction is already
1957 Fink's Television Engineering Hadbook
Assuming that the distance from the deflection center of the picture tube to the image receiving surface is l, the distance from the center of the image receiving surface to the end in the left and right direction is a, and the image receiving surface is a flat surface, the following equation is obtained. (The horizontal direction of the picture tube surface is the X-axis, and ^{the vertical direction} is the y ^- axis.) The desired correction can be achieved by modulating the horizontal deflection current. 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 errors, but the peak-to-peak (p-p) value of the horizontal deflection sawtooth current is used for the vertical deflection. If the modulation is performed using a hyperbolic period, the SPC distortion will be corrected to a nearly straight line as shown by the broken line in Figure 3.

An example of such a circuit configuration is shown in FIG. 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 a hyperbolic waveform generation circuit, 6 is a horizontal amplitude modulation circuit, and the horizontal deflection coil 2 , a vertical deflection coil 4 is attached to the neck of the picture tube (not shown),
It is assumed that the electron beam of the picture tube is deflected in the horizontal and vertical directions, respectively.

In this way, the horizontal deflection output circuit 1 causes the sawtooth wave current (horizontal deflection sawtooth wave current) Iyh with the horizontal deflection period to flow through the horizontal deflection coil 2, and the vertical deflection output circuit 3 causes the sawtooth wave current (horizontal deflection sawtooth wave current) with the vertical deflection period to flow through the horizontal deflection coil 2. A vertical deflection sawtooth wave current (Iyv) is passed through the vertical deflection coil 4 to form a substantially rectangular raster on the picture tube surface. Furthermore, at the same time, a hyperbolic waveform voltage Vhp of the vertical deflection period is obtained from the vertical deflection output circuit 3 through the hyperbolic generating circuit 5, and is applied to the horizontal amplitude modulation circuit 6. Further, the horizontal amplitude modulation circuit 6 acts on the horizontal deflection output circuit 1 to modulate the pp value of the horizontal deflection sawtooth wave current Iyh in accordance with the value of the hyperbolic waveform voltage Vhp.

FIG. 5 illustrates a more specific circuit example of the conventional example.

Here, it is assumed that the parts numbered 1 to 6 function similarly to the parts with the same numbers in FIG. 4 above.
Then, the horizontal amplitude modulation circuit 6 receives the DC power supply voltage Eb
By obtaining a DC power supply voltage Eb' with a predetermined ripple from
This is a type of modulation in which the pp value of Iyh is modulated according to the purpose.

Here, 7 is a voltage controlled NPN type transistor,
8 is its base bias resistor, 9 is a smoothing capacitor for flowing the ripple current of the horizontal deflection frequency component exclusively, and 10 is a coupling capacitor, and when a modulation voltage (here, hyperbolic waveform voltage Vhp') is applied to one end of the capacitor, The DC power supply voltage Eb' is modulated according to this voltage (waveform).

In addition, a control circuit 11 may be added at the same time, and by varying the control current is flowing here with a variable resistor 12 attached to the circuit, the base voltage of the voltage control transistor 7, and by extension the DC power supply. The voltage value of voltage Eb' can also be adjusted.

Further, the control circuit 11 changes its operating state according to the average voltage value of the DC power supply voltage Eb'. For example, if the voltage Eb' increases, the control circuit 11 works to increase the control current is and lower the voltage Eb'. A negative tape feedback characteristic may be provided, and as a result, the average voltage value of the voltage Eb' and the value of the horizontal deflection sawtooth wave current Iyh flowing through the horizontal deflection coil 2 are stabilized.

By the way, in order to make the shape of the envelope of the horizontal deflection sawtooth wave current Iyh a hyperbola, it is not necessary to just make the modulation voltage (waveform) of the voltage Eb' into a hyperbola.

That is, here, in addition to the hyperbolic waveform voltage Vhp, the correction voltage waveform generated by the correction waveform generation circuit 13 is used.
Vaux must be combined with the hyperbolic waveform voltage Vhp in the adder circuit 14 to form a composite waveform (hyperbolic waveform voltage) Vhp', and then added to the base of the voltage control transistor 7 through the coupling capacitor 10.
The envelope of the horizontal deflection sawtooth current Iyh does not have a correct hyperbolic waveform.

This is the horizontal deflection coil 2 as shown in FIG.
This is because it consists of an inductance component L and a DC resistance component R. That is, when a ripple current i with a vertical deflection period is caused to flow through the series circuit of the inductance L and the DC resistance R shown in FIG. 6, a waveform V _R similar to the waveform of the current i appears at both ends of the DC resistance R. However, in the inductance L, a waveform V _L is generated by differentiating this with respect to time t.

Therefore, if you want to flow a current like i through a series circuit of inductance L and DC resistance R like this horizontal deflection coil 2, you will have to apply a voltage of V _L + V _R here. Become.

The correction waveform generation circuit 13 and the _addition circuit 14 shown in FIG. 14, combine it with the original hyperbolic waveform voltage Vhp to obtain the modulation voltage (hyperbolic waveform voltage) Vhp' of the device, and add this to the voltage control transistor 7 through the coupling capacitor 10 to modulate the DC power supply voltage Eb'. The envelope of the deflection sawtooth wave current Iyh can be correctly determined as the hyperbolic waveform voltage Vhp.

(Problem to be solved by the invention) By the way, it is difficult to create the hyperbolic waveform voltage Vhp and the auxiliary voltage (waveform) Vaux shown in FIG. The only way to create it is by using a polygonal line approximation using non-linear elements. In any case, in this way,
Creating these two waveforms has the problem that the circuit becomes extremely complicated.

Also, when it is necessary to change the deflection amplitude like overscan/underscan, it is natural to change the constants of both the hyperbolic waveform generation circuit 5 and the correction waveform generation circuit 13 at the same time to generate a hyperbolic waveform voltage.
The amplitude of Vhp and the auxiliary voltage (waveform) Vaux had to be changed in proportion to the horizontal deflection sawtooth wave current Iyh, which resulted in a problem that the circuit configuration became extremely complicated.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and includes a horizontal deflection circuit for horizontally deflecting a picture tube and a vertical deflection circuit for vertically deflecting a picture tube. There is a deflection circuit and a power supply voltage modulation circuit that modulates the power supply voltage of the horizontal deflection circuit, and the deflection correction waveform of the vertical deflection period obtained from the vertical deflection circuit is added to the power supply voltage modulation circuit to the right and left ends of the raster. In the image distortion correction circuit that corrects the shape of the deflection correction waveform, a sawtooth voltage waveform with a vertical deflection period is passed through a waveform shaping circuit to shape the shape of the voltage waveform near its peak value and/or bottom value. By adding the first signal obtained through the above-mentioned first signal and the second signal obtained by passing the first signal through an integrating circuit, the horizontal deflection saw can be obtained with a simple configuration. The envelope of the wave current is made to correctly match the output waveform of the integrating circuit, and it is possible to more accurately and easily correct the shape of the left and right edges of the raster, especially for side pink tension distortion correction. The present invention provides an effective image distortion correction circuit.

(Embodiment) FIG. 1 illustrates an embodiment of an image distortion correction circuit according to the present invention. Here, numbers 1 to 4,
6 and 14 function in the same manner as the portions with the same numbers in FIG. 5 above. Newly added 1 here
5 is a waveform shaping circuit, and 16 is an integrating circuit.

In this way, first, the vertical deflection period sawtooth voltage Vst can be easily obtained from the vertical deflection output circuit 3, and this is applied to the waveform shaping circuit 15. This waveform shaping circuit 15 compresses the vertical deflection period sawtooth wave voltage Vst, so that its slope is almost horizontal near the start point of the scan period, becomes steeper toward the center of the scan, and becomes less sloped toward the end point of the scan.ゞA vertical deflection periodic sawtooth wave voltage Vst′ that becomes horizontal can be obtained.

Then, when this vertical deflection periodic sawtooth wave voltage Vst' is applied to the next integrating circuit 16, a hyperbolic waveform voltage Vhp that closely approximates a hyperbola is obtained as its output.

On the other hand, this hyperbolic waveform voltage Vhp and the previous vertical deflection periodic sawtooth wave voltage Vst' are combined in an adder circuit 14 to obtain a hyperbolic waveform voltage Vhp', and according to this hyperbolic waveform voltage Vhp', the DC power supply voltage Eb is The modulated DC power supply voltage Eb' becomes the operating power supply voltage of the horizontal deflection output circuit 1, so that the pp value of the horizontal deflection sawtooth wave current Iyh is modulated according to the purpose.

As previously explained in Fig. 2, when trying to obtain a predetermined waveform in the envelope of the horizontal deflection sawtooth current Iyh, the waveform of the DC power supply voltage Eb' of the circuit, that is, the hyperbolic waveform voltage Vhp' is Horizontal deflection sawtooth current
All you have to do is synthesize the Iyh envelope waveform as it is and its differential waveform at an appropriate ratio.

However, since the hyperbolic waveform voltage Vhp is a waveform obtained by integrating the vertical deflection periodic sawtooth wave voltage Vst', the differential form of the voltage Vhp is always the voltage Vst'. If they are combined in proportion (according to the L and R ratios of the deflection coils), the shape of the envelope of the horizontal deflection sawtooth wave current Iyh will be the same as that of the hyperbolic waveform voltage Vhp.

From this, if you want to make the envelope of the horizontal deflection sawtooth wave current Iyh correctly hyperbolic for SPC distortion correction, first create the voltage Vst' that becomes a hyperbola by integrating it, and then What is necessary is to synthesize the integrated waveform and modulate the power supply voltage of the horizontal deflection output circuit 1.

In this way, for example, when changing the deflection amplitude, the amplitude of the modulation envelope must be changed in accordance with the change in the amplitude of the horizontal deflection sawtooth current Iyh. If only the amplitude is changed, the voltage Vst'Vhp will also change proportionally at the same time, so the envelope of the horizontal deflection sawtooth wave current Iyh can also be changed while keeping its shape.

In addition, due to fine adjustment of the envelope waveform, even if the waveform of the voltage Vst′ is slightly deformed, the hyperbolic waveform voltage Vhp is always
The waveform of and the waveform of the envelope of the horizontal deflection sawtooth current Iyh match, making adjustment extremely easy.

FIG. 2 is also a circuit diagram for explaining the present invention in more detail, and it is assumed that the same numbered parts as in FIG. 1 have the same functions.

An example of the internal circuit configuration of the waveform shaping circuit 15 will be described here. First, 17 is a first DC blocking capacitor, 18 is a charging/discharging resistor, 19 is a first slice diode, 20 is a first discharging resistor, 21 2 is a second DC blocking capacitor, 22 is a second slice diode, and 23 is a second discharge resistor/variable resistor for adjusting the correction amplitude.

Also, regarding the inside of the integrating circuit 16, first 2
4 is the first operational amplifier, 25 is a coupling capacitor from the previous stage, 26 is an input resistance of the first operational amplifier 24, 27 and 28 are resistors for determining the DC operating point of the first operational amplifier 24, and 29 is for integration. The time constant capacitor 30 is a DC gain limiting resistor.

Furthermore, regarding the inside of the adder circuit 14, 3
1 is the second operational amplifier, 32 is the input capacitor, 33 is the input resistance of the operational amplifier 31, 34, 3
5 is a resistor for determining the DC operating point of the operational amplifier 31;
6 is an input coupling capacitor for auxiliary voltage (waveform), 3
7 is an input resistor for limiting the amplitude of the auxiliary voltage (waveform), and 38 is a negative feedback resistor for determining the gain of the operational amplifier 31.

Further, reference numeral 6 is a horizontal amplitude modulation circuit using power supply voltage modulation as previously explained with reference to FIG. 5, and since the individual internal configurations are also the same, the explanation thereof will be omitted.

If the configuration is as shown in Fig. 2, first the waveform shaping circuit 1
5, the first slice diode 19 conducts for a time t1 near the positive peak of the vertical periodic sawtooth wave voltage Vst (near the scanning front end), and the voltage (waveform) Vst
Slice off the top. Further, the second slicing diode 22 becomes conductive for a time t2 near the end of the scan, slicing the lower end of the voltage (waveform) Vst.
The lengths of both slice times t1 and t2 are as follows: DC blocking capacitors 17, 21, charging/discharging resistor 18,
Depending on the constants of the discharge resistor 20 and variable resistor 23,
They can each decide independently.

And if these constants do not change, time t
1, t2 remains constant even if the amplitude of the input vertical periodic sawtooth wave voltage Vst changes, and the voltage Vst' does not change. Further, this voltage VSt' is adjusted in magnitude by a variable resistor 23 and is applied to the next stage.

In the next integrating circuit 16, the voltage VSt' has its DC component cut off by a coupling capacitor 25, and then the input resistor 26
is applied to the inverting input terminal of operational amplifier 24 through the input terminal. Then, with the value of the product of the capacitor 29 and the resistor 30 as an integration time constant, a voltage (waveform) -Vhp obtained by inverting and integrating the voltage (waveform) VSt' is obtained at the output terminal of the operational amplifier 24.

Also, one end of the resistor 27 is connected to the DC power supply (voltage) +E
and the value of resistors 27 and 28 is the output voltage - Vhp
The voltage level is set so as to be sufficiently within the dynamic range of the operational amplifier 24.

The voltage obtained here - Vhp is the capacitor 3
2. It is applied to the inverting input terminal of the next operational amplifier 31 through a resistor 33. Then, the voltage -Vhp appears at the output terminal of the operational amplifier 31 after being inverted and amplified according to the ratio of the resistors 38 and 33, while the voltage Vst' appears at the non-inverting input of the operational amplifier 31 through the coupling capacitor 36 and the resistor 37. Since it is applied to the terminal, the voltage Vst' is divided by the resistors 37, 34, and 35, and then amplified by the operational amplifier 31. Eventually, the output of the operational amplifier 31 is the voltage (waveform) Vhp and the voltage (waveform) VSt. ′ composite waveform (hyperbolic waveform voltage)
It appears as Vhp′. The voltage peak value of this composite waveform Vhp′ and the ratio of the Vhp component to the Vst′ component are:
As is clear from the explanation so far, the resistance 33,3
It can be freely set to values such as 8, 37, 34, 35, etc.

Also, like the operational amplifier 24, one end of the resistor 34 is connected to the DC power supply +E, but the ratio between the resistors 34 and 35 is such that the voltage level of the output Vhp' of the operational amplifier 31 is just the same as the dynamic voltage level of the operational amplifier 31. Just set it so that it stays within the range.

The composite waveform Vhp' thus obtained is applied to the base of the voltage control transistor 7 via the coupling capacitor 10, as in the case of FIG. 5 above. Then, the modulation voltage (waveform) of the DC power supply voltage Eb' supplied to the horizontal deflection output circuit 1 becomes the same as the composite waveform Vhp', and the shape of the envelope of the horizontal deflection sawtooth wave current Iyh flowing through the horizontal deflection coil 2 is explained first. Due to this principle, the voltage (waveform) Vhp will match.

Note that when integrating the voltage (waveform) st′ obtained by slicing the upper and lower ends of the sawtooth wave in this way, it does not become a perfect hyperbola, but rather a straight line at both ends of the scan and a parabola at the center. It becomes a waveform.

However, this can be sufficiently approximated to a hyperbola, and the raster SPC distortion can be corrected much better than modulating the horizontal deflection sawtooth wave current Iyh with only a simple parabola, as is often seen in the past.

Also, when generating the original sawtooth wave voltage Vst,
The sloped part may not be a straight line but may be curved due to an exponential component.

In such cases, it is often better to make the slice time t2 at the rear end of the scan even shorter than time t1, resulting in a pseudo-hyperbola with better symmetry, and slicing only at time t1 may be sufficient for practical use. be.

Further, depending on the characteristics of the horizontal deflection coil and the shape of the picture tube image receiving surface, it may be better to slightly deviate the shape of the envelope of the horizontal deflection sawtooth wave current from a perfect hyperbola.

Examples of circuits in such a case are not shown one by one, but for example, a suitable impedance is inserted into the slice diodes 19 and 22 to create a half clamp, or a small capacitance is added in parallel to the charging/discharging resistor 18. There is a method of finely modifying the waveform of the hyperbolic waveform voltage Vhp, that is, the waveform of the envelope of the horizontal deflection sawtooth wave current Iyh, by adding a differential waveform.

In such a case, no matter how the waveform of the hyperbolic waveform voltage Vhp is modified, the modulation voltage (waveform) of the DC power supply voltage Eb' as the power supply voltage of the horizontal deflection output circuit 1 will always be the original target voltage Vhp. The resulting waveform is a composite waveform of the voltage (waveform) VSt′ obtained by differentiating it at a constant ratio, and the horizontal deflection sawtooth wave current is correctly calculated.
Iyh can be modulated with hyperbolic waveform voltage Vhp.

(Effects of the Invention) As described above, according to the image distortion correction circuit of the present invention, it is possible to modulate the horizontal deflection sawtooth wave current (Iyh) with the same waveform as the hyperbolic waveform voltage (Vhp). It is extremely easy to modulate the horizontal deflection sawtooth wave current with the desired waveform.
It is possible to correct the shape of the left and right ends of the picture tube raster, and is particularly effective when performing SPC distortion correction more precisely.

[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, FIG. 2 is a diagram showing an example of a more specific circuit according to the present invention, and FIG. 3 is a block diagram showing an example of an image distortion correction circuit according to the present invention. FIG. 4 is a block diagram of a conventional example for correcting SPC distortion, FIG. 5 is a diagram showing an example of a more specific circuit of the conventional example, and FIG. The figure is a diagram showing an equivalent circuit of a horizontal deflection coil and waveforms generated therein according to the present invention. 1...Horizontal deflection output circuit, 2...Horizontal deflection coil,
3... Vertical deflection output circuit, 4... Vertical deflection coil, 5
...Hyperbolic waveform generation circuit, 6...Horizontal amplitude modulation circuit,
7... Voltage control NPN type transistor, 8... Base bias resistor, 9... Smoothing capacitor, 10, 25
...Coupling capacitor, 11...Control circuit, 12, 23
...variable resistor, 13...correction waveform generation circuit, 14...addition circuit, 15...waveform shaping circuit, 16...integrator circuit,
17, 21... DC blocking capacitor, 18... Charging/discharging resistor, 20... Discharging resistor, 19, 22... Slice diode, 24, 31... Operational amplifier, Eb... DC power supply voltage, Eb'... Modulated DC power supply voltage, Iyh
...Horizontal deflection sawtooth wave current, Iyv...Vertical deflection sawtooth wave current, i...Vertical cycle ripple current flowing through the horizontal deflection coil, is...Control current, L...Inductance of the horizontal deflection coil, R...DC resistance of the horizontal deflection coil Minutes, Vaux…corrected voltage (waveform), Vhp…
Hyperbolic waveform voltage, Vhb′...Hyperbolic waveform voltage with correction waveform added, Vst...Vertical periodic sawtooth wave voltage,
Vst′…Sliced vertical periodic sawtooth wave voltage.

Claims (1)

[Claims] 1. A horizontal deflection circuit for horizontally deflecting the picture tube, and a vertical deflection circuit for vertically deflecting the picture tube,
A power supply voltage modulation circuit modulates the power supply voltage of the horizontal deflection circuit, and a deflection correction waveform of the vertical deflection period obtained from the vertical deflection circuit is added to the power supply voltage modulation circuit to correct the shape of the left and right ends of the raster. In the image distortion correction circuit, the deflection correction waveform is obtained by passing a sawtooth voltage waveform of a vertical deflection period through a waveform shaping circuit and shaping the shape of the voltage waveform near its peak value and/or bottom value. An image distortion correction circuit characterized in that the image distortion correction circuit is obtained by adding a first signal and a second signal obtained by passing the first signal through an integrating circuit.