JPS61269571A - Pincushion distortion correction circuit - Google Patents

Abstract

PURPOSE:To correct pincushion distortion over the entire raster by synthesizing a vertical parabolic wave on a vertical sawtooth wave superimposed on a horizontal parabolic wave through an adjustment variable resistor. CONSTITUTION:A variable resistor R11 of a raster horizontal pincushion distortion correction wave generating circuit is connected in parallel and a vertical parabolic wave input terminal 4 is connected to a slider of the variable resistor R11 via a capacitor C4. Thus, a waveform synthesizing a vertical sawtooth wave and a vertical parabolic wave is inputted between bases of differential amplifiers TR 1, TR 4 and TR 2, TR 3. Thus, an output waveform outputted from a terminal 3 is corrected linearly in the entire raster by adjusting the variable resistor R11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a raster horizontal pincushion distortion correction circuit that can be used in a large projection type television receiver.

2. Description of the Related Art A conventional horizontal pincushion distortion correction circuit uses a double-balanced connection differential amplifier circuit mainly composed of transistors Tr to Tr6 as shown in FIG. Input a vertical sawtooth wave to input terminal 2 and a horizontal parabolic wave to input terminal 2.
) A vertical sawtooth waveform on which a parabolic wave with a horizontal period is superimposed is generated at the output terminal 3, and this waveform is input to the convergence output circuit on the left (not shown), and the voltage and current are converted and the waveform shown in the figure is Figure 6 (
A current with a waveform like &) is applied to correct raster horizontal pincushion distortion. Bald, Figure 6 (b)
is an enlarged view of the main part of the same figure (&).

Problems to be Solved by the Invention However, in the conventional technology, since the correction wave is symmetrical between the first half and the second half of the vertical scanning period as shown in FIG. 5 (IL), the current flowing through the vertical deflection coil is also symmetrical. , the correction amounts for the first half and the second half of the vertical deflection are the same. Therefore, Fig. 3 (2)),
As shown in the upper figure of (b), if the raster horizontal pincushion distortion is vertically asymmetrical, even after correction, Fig. 3 (a), Φ)
As shown in the figure below, if either the top or bottom of the raster is insufficiently corrected and distortion remains, the problem is 3 bedes.

The present invention corrects the remaining raster horizontal pincushion distortion in this way, and provides a correction circuit that can obtain a straight front horizontal line over the entire rask after correction.

Means for Solving the Problems In order to achieve the above object, the pincushion distortion correction circuit according to the present invention combines a vertical parabolic wave through a volume into a vertical sawtooth wave that is superimposed on a horizontal parabolic wave. Features.

According to the present invention, by synthesizing a vertical parabolic wave with a vertical sawtooth wave through a volume, the peak value of the horizontal parabolic wave can be changed between the first half and the second half of the vertical scanning period by adjusting the volume. , it is possible to accurately correct pincushion distortion over the entire raster.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1, 2, and 3.

The difference between FIG. 1 and FIG. 4 is that a volume R11 is connected in parallel to both ends of the volume R1 of the conventional raster horizontal pincushion distortion correction wave generation circuit shown in FIG. The vertical parabolic wave input terminal 4 is connected through the capacitor C4, and the vertical parabolic wave is input from this input terminal 4 through the capacitor C4. As a result, the differential amplifier Tr1
．． Tr4,! : A waveform that is a combination of a vertical sawtooth wave and a vertical parabolic wave will be input between the bases of Tr 2 + Trs, and the waveform that is input from input terminal 2 in the first half and second half of the vertical scanning period will be input to output terminal 3. A waveform with different wave heights of horizontal parabolic waves is output. For this output waveform, the level ratio of the peak values of the horizontal parabolic waves in the first half and the second half of the vertical scanning period can be adjusted with the volume R11, as shown in Fig. 1 e).
Three types of waveforms shown in (b) and (c) are obtained.

If raster horizontal pincushion distortion is corrected using non-symmetrical waveforms in the first and second half of the vertical scanning period shown in Figure 1(b) as in the past, the 5th page shown in Figure 3(a) , when the latter half of vertical scanning is insufficiently corrected and distortion remains,
Adjust the output waveform output from terminal 3 in Figure 1 to the volume R.
By adjusting 11 to create a waveform in which the peak value is low in the first half of the vertical scanning period and high in the second half as shown in Figure 2 ((1), and by increasing the amount of vertical deflection in the latter half of the vertical scanning period than in the first half, Using the same procedure, if the first half of the vertical scan is insufficiently corrected and potash distortion remains, as shown in Figure 3 (b), change the output waveform of output terminal 3 in Figure 1 to the one shown in Figure 2 (IL). By creating a waveform with a larger vertical deflection amount in the first half than in the second half of the vertical scan, it is possible to correct the entire raster area to a straight horizontal line.

In fact, the raster horizontal pincushion distortion correction wave taken out from the output terminal 3 shown in FIG. 1 is input to a convergence output circuit (none of which is shown) for passing a deflection current to the vertical deflection coil.

A current having the same waveform as the voltage waveform generated at the output terminal 3 is passed through the vertical deflection coil.

Effect of the invention As described above, according to the present invention, a vertical parabolic wave.

By using a vertical sawtooth wave and a horizontal parabolic wave, raster horizontal pincushion distortion can be corrected to a straight horizontal line over the entire raster area.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a pincushion distortion correction circuit in an embodiment of the present invention, and Fig. 2 (!L), (b), (
C) is an output waveform diagram for explaining the operation in Figure 1, Figure 3 is a diagram showing the change in Lascou when raster horizontal pincushion distortion is corrected, Figure 4 is a circuit diagram of the conventional example, and Figure 5 (
+! L) and (b) are waveform diagrams for explaining the operation of FIG. 4. 1... Vertical sawtooth wave input terminal, 2...
・Horizontal parabolic wave input terminal, 4...Vertical parabolic wave input terminal, R1+ R21R11''...Volume 7r, , Tr2 +'rr, , Tr4・
Tr5/Tr6...Transistor. Name of agent: Patent attorney Toshi Nakao and 1 other person C07 '3 <:r S Ward ---~ Ryo

Claims (1)

[Claims] A vertical parabola wave voltage is input to the movable terminal of the adjustment volume via a capacitor, and the vertical parabola wave voltage obtained from both ends of the adjustment volume is added to the superimposed waveform of the vertical sawtooth voltage and the horizontal parabola wave voltage. A pincushion distortion correction circuit configured so that the peak value of the horizontal parabolic wave voltage can be changed between the first half and the second half of the vertical scanning period by adjusting the adjustment volume.