JPH0486192A - Picture distortion correcting circuit - Google Patents

Abstract

PURPOSE:To correct the picture distortion in the vertical direction of a screen with a simple circuit constitution by providing a transformer in the succeeding stage of a correction waveform generator and flowing currents, where correction currents having opposite polarities are superposed on a main deflecting current, to respective vertical deflecting yokes of a CRT for red and a CRT for blue and flowing only the main deflecting current to the vertical deflecting yoke of a CRT for green. CONSTITUTION:A picture distortion correcting transformer 16 is provided in the succeeding stage of a correction waveform generator 10, and vertical deflecting yokes 7 and 9 of CRTs 1 and 3 for red and blue are connected to the secondary side, and a vertical deflecting yoke 8 for green is connected to its tap, and currents where correction currents having opposite polarities are superposed on the main deflecting current flow to respective vertical deflecting yokes of CRTs 1 and 2 for red and blue, and only the main deflecting current flows to the vertical deflecting yoke of the CRT for green. Thus, the picture distortion in the vertical direction is corrected without providing convergence coils for R and B and their output circuits by the simple constitution of a drive circuit for picture distortion correcting transformer and the picture distortion correcting transformer.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to screen distortion correction circuits, especially projection TVs.
This invention relates to an improvement of the screen distortion correction circuit.

[Conventional technology]

In general, a projection TV is configured as shown in FIG.
, 4 indicates a screen for projecting the image, and green (G
) CRT 2 is placed in such a position that its projected image is symmetrical with respect to the origin OOy axis of the screen 4.
The red (R) CRTI and the blue (B) CRT 3 are located on both sides of the edge (G) CRT 2, respectively.
The projected image is positioned asymmetrically with respect to the y-axis of the screen 4.

To explain the distortion of the above projected image using Fig. 4, red (R)
(for CRTI or blue CB) from CRT3 to screen 4
The distance to the left side of the screen is different from the right side of the screen. Therefore, regarding the projected image of the CRT1 for red (R), on the right side of the screen 4 it is extended horizontally and vertically, and on the left side it is shrunk horizontally and vertically. Blue (B) CRT
3, a screen distortion occurs in which an opposite image is projected centering on the y-axis.

Incidentally, the above-mentioned screen distortion may be corrected using, for example, a convergence correction circuit as shown in FIG.

In the figure, 5 is a vertical drive circuit that receives a vertical synchronization signal VD as an input and outputs a vertical deflection drive signal, 6 receives a vertical deflection drive signal as an input, and has a vertical deflection yoke for R2O, B? , 8.9; 10 is a correction waveform generator that generates a trapezoidal distortion correction waveform (see FIG. 6) consisting of a multiplication waveform of a horizontal sawtooth wave and a vertical sawtooth wave; 11;
．． 12 inputs the trapezoidal distortion correction waveform, and R convergence coils 13 . Convergence coil 1 for B
These are an R convergence output circuit and a B convergence output circuit that drive 4.

Next, the operation will be explained.

The correction waveform generation circuit 10 generates a trapezoidal distortion correction waveform as shown in FIG.
1 and B convergence output circuit 12 output L, R convergence coil 13°B convergence coil 1
By passing correction currents having opposite polarities through the terminals 4 and 4, screen distortion as shown in FIG. 4 is corrected.

[Problem to be solved by the invention]

Since conventional screen distortion correction circuits are configured as described above, there are problems such as excessive current load to correct screen distortion, increasing the load on each convergence coil, and making the circuit itself complicated. was there.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a waveform distortion correction circuit that can reduce the load on the convergence coil of the screen distortion correction circuit and simplify the circuit configuration. do.

[Means to solve the problem]

The screen distortion correction circuit in this invention is provided with a transformer after the correction waveform generator, and the vertical deflection yokes of the CRT for red and blue are connected to the secondary side of the transformer, and the vertical deflection yoke for green is connected to the tap of the transformer. , a current consisting of the main deflection current and a correction current of opposite polarity is passed through each vertical deflection yoke of the red CRT and blue CRT, and only the main deflection current is passed through the vertical deflection yoke of the peripheral CRT. This is what I did.

[Effect]

In this invention, a current in which a correction current of opposite polarity is superimposed on the main deflection current flows through each vertical deflection yoke of the red CRT and blue CRT, and a main deflection current flows through the vertical deflection yoke of the peripheral CRT. Since only the current is allowed to flow, screen distortion in the vertical direction of the screen can be corrected with a simple circuit configuration without using a convergence coil.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration diagram of a screen distortion correction circuit according to an embodiment of the present invention, where the same reference numerals as in FIG. A screen distortion correction transformer drive circuit 16 is connected to the screen distortion correction drive circuit 15 on the primary side, and a vertical deflection yoke 7 for red (R) and a vertical deflection yoke 7 for blue (B) are connected on both sides of the secondary side, respectively. This is a screen distortion correction transformer in which a vertical deflection yoke 9 is connected and a vertical deflection yoke 8 for green (G) is connected to its tap.

Next, the operation will be explained.

The screen distortion correction transformer drive circuit 15 drives the primary coil of the screen distortion correction transformer 16 with the trapezoidal distortion correction waveform generated by the correction waveform generator 10 and shown in FIG.

On the other hand, the vertical deflection coils 7, 8, 9 for R, G, and B are connected to each other at one end of the coil and driven in parallel by the vertical deflection circuit 6, and the vertical deflection yoke 7 for R and the vertical deflection yoke 7 for B are connected to each other at the other ends. The vertical deflection yoke 9 is connected to both ends of the secondary side of the correction transformer 16, and the vertical deflection yoke 8 for G is connected to the tap of the correction transformer 16, so that the vertical deflection yoke 9 for R is connected to the tap of the correction transformer 16 as shown in FIG. 7. Current It flowing through vertical deflection yoke 9 for B
(Figure (al), 1. (Figure (C)) shows that screen distortion correction waveforms with opposite polarities flow superimposed on the main deflection current, and current IG (Figure (C)) flows through the G vertical deflection yoke 8.
bl), only the main deflection current flows, and as a result, the red CRT
I. Screen distortion on the screen 4 of the blue CRT 3 is corrected and convergence characteristics can be improved.

According to this embodiment, the screen distortion correction transformer 16 is provided after the correction waveform generator 10, and the vertical deflection yokes 7.9 of the red and blue CRTs 1.3 are connected to the secondary side of the transformer 16. , connect the line vertical deflection yoke 8 to that tap,
A current consisting of the main deflection current and a correction current of opposite polarity is passed through each of the vertical deflection yokes of the red CRT1 and the blue CRT2, and only the main deflection current is passed through the vertical deflection yokes of the peripheral CRT. Therefore, as before, for R, B
Vertical screen distortion can be corrected with a simple configuration of a screen distortion correction transformer drive circuit and a screen distortion correction transformer without providing a convergence coil and its output circuit.

In the above embodiment, a projection TV in which three CRTs of R, G, and B were arranged horizontally was explained, but by stacking three CRTs arranged horizontally in two or three stages vertically, A similar effect can be obtained with respect to distortion correction in the vertical direction with respect to the constructed projection TV.

〔Effect of the invention〕

As described above, according to the screen distortion correction circuit according to the present invention,
A current consisting of the main deflection current and a correction current of opposite polarity is passed through each vertical deflection yoke of the red CRT and blue CRT, and only the main deflection current is passed through the vertical deflection yoke of the peripheral CRT. Therefore, vertical screen distortion can be corrected using only the main deflection yoke without using a convergence coil, and the circuit load can be reduced with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a screen distortion correction circuit according to an embodiment of the present invention, FIG. 2 is a current waveform diagram from a screen distortion correction transformer of the screen distortion correction circuit according to an embodiment of the present invention, and FIG. A diagram showing the arrangement of a CRT used in a projection TV and the projected screen on the screen. Figure 4 is a diagram showing the projection raster of a projection TV viewed from the front of the screen. Figure 5 is a diagram showing the conventional convergence system for correcting screen distortion. Correction circuit diagram FIG. 6 is a current waveform diagram output from a correction waveform generator of a conventional convergence correction circuit. 1 is a red (R) CRT, 2 is a green (G) CRT, 3 is a blue (B) CRT, 4 is a screen, 5 is a vertical drive circuit, 6 is a vertical deflection output circuit, 7 is a vertical deflection for R yoke,
8 is the vertical deflection yoke for G, 9 is the vertical deflection yoke for B, 1
0 is a correction waveform generator, 15 is a drive circuit for a screen distortion correction transformer, and 16 is a screen distortion correction transformer. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 1b 1"Kin (R) Shield CRT 2° # (G) JCRT 3: J (B) JCRT 9: BM!J fIM73-ri

Claims (1)

[Claims] (1) In a screen distortion correction circuit for a projection TV using three red, green, and blue CRTs arranged in parallel, there is a correction waveform generation circuit that generates a trapezoidal distortion correction waveform, and a screen that receives the correction waveform as input. The distortion correction drive circuit and the screen distortion correction drive circuit are connected to the primary side, and the vertical deflection coils of the CRTs on both sides of the CRTs arranged in parallel are connected to the secondary side, and the taps thereof are connected to the secondary side. is equipped with a screen distortion correction transformer connected to the vertical deflection coil of the CRT placed in the center of the three CRTs, and screen distortion of opposite polarity to the vertical deflection coils of the two CRTs placed on both sides. A screen distortion correction circuit for a projection TV, characterized in that a correction signal is superimposed.