JPS6359067A - Pincushion distortion correcting circuit - Google Patents

Abstract

PURPOSE:To attain very fine distortion correction inexpensively by forming a pincushion distortion correction table based on the result of measurement of pincushion distortion and generating a pincushion distortion deflection current based on a correction information output of said correction table so as to apply pincushion distortion correction. CONSTITUTION:The upper/lower and the left/right pincushion distortion correction table is formed respectively in a ROM2A and a ROM2B. Correction table information is read from the ROM2A under the control of a read control means 1A. Moreover, a sawtooth wave is generated from a sawtooth wave generator 6 based on a vertical synchronizing signal Vs, the sawtooth wave and a conversion output of a D/A converter DAC3 are added by an adder 9 and a vertical deflection current flows to a vertical deflection yoke DY 5. The upper/lower pincushion distortion on a CRT display is corrected by the vertical deflection current. Then the left/right pincushion distortion correction deflecting current is supplied to the horizontal deflection yoke DY 11 as described above to correct the left/right pincushion distortion of the CRT.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Object of the Invention] (Industrial Application Field) The present invention relates to a pincushion distortion correction circuit for a CRT display.

(Prior Art) Conventionally, as a method for correcting pink distortion among image distortions caused by CRI displays, a method has been adopted in which a correction current is superimposed on each of the vertical and horizontal deflection currents of a CRT display. It is being

The basic waveform of the correction current in this case is shown in FIG. 2, and the vertical deflection current waveform and horizontal deflection current waveform after correction are shown in FIGS. 3 and 4, respectively.

(Problems to be Solved by the Invention) However, when implementing the above-mentioned correction Bunod equation, the modulation circuit configuration especially in the vertical portion becomes complex, which causes a cost problem. In addition, as in the past, the modulation waveform of
It is not possible to correspond to the magnetic field component (abbreviated as Yj), and as a result, it is not possible to perform fine-grained distortion correction.

This invention has been developed in view of the above circumstances, and its first objective is to provide a cushion distortion correction system that can be realized at low cost and that also provides fine-grained distortion correction. [Configuration of the Invention] (Means for Solving the Problems) The present invention provides a circuit for controlling the CRT in a state in which a known pincushion distortion correction signal is applied and in a state in which a known pincushion distortion correction signal is not applied. a pincushion distortion correction table formed based on pincushion distortion measurement results at multiple points on the display;
The apparatus includes a readout control means for controlling reading of the correction table information, and a correction deflection current generation means for outputting a pincushion distortion correction deflection current based on the readout correction table information.

(Function) Correction table information is read out from the pincushion distortion correction table under the readout control of the readout control means, and a correction deflection current is output based on this correction table information. As described above, a pincushion distortion correction table is formed based on the measurement results of pincushion distortion at multiple points on a CRT display, and a pincushion distortion deflection current is generated based on the correction information output of this correction table. Since pincushion distortion is thereby corrected, manufacturing loss can be reduced by simplifying the correction circuit itself and drastically reducing the number of adjustment parts. Also, C
Since the pincushion distortion correction table is created based on the pincushion distortion measurement results at multiple points on the RT display, the magnetic field distribution distortion of the deflection yoke.

It is possible to correct pincushion distortion including both sides of the electronic lens distortion of the CRT display and mechanical and physical distortion of the CRT display, and as a result, very fine distortion correction can be performed.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

FIGS. 1(a) and 1(b) show circuits according to an embodiment of the present invention. FIG. 1(a) shows a circuit for correcting vertical pincushion distortion, and FIG. 1(b) shows a circuit for correcting left and right pincushion distortion. This is the circuit that does this.

The circuit shown in FIG.
M (read on memory) 2A.

It has a DAC (digital to analog converter) 3° correction deflection current generating means 4A and a sawtooth wave generator 6.

Upper and lower pincushion distortion correction tables are formed in the ROM 2A, and in this sense, the ROM 2A is also referred to as a pincushion distortion correction table.

This pincushion distortion correction table is formed based on the results of upper and lower pincushion distortion measurements at a plurality of points on a CRT display in a state in which a known pincushion distortion correction signal is applied and in a state in which a known pincushion distortion correction signal is not applied. Specifically, it is formed as follows.

First, an image is displayed on a CRT display without adding a correction signal waveform, and pincushion distortion is measured.

In this case, measurement points are determined in advance. For example, let's say 16 points horizontally, 16 points vertically, and a total of 256 points for the picture frame. Next, a known correction signal waveform, for example, the correction waveform shown in Figure 2, is added to the horizontal and vertical deflection current waveforms from a temporary storage element (e.g., ROM) or directly from the outside, and the amount of pincushion distortion is measured again, and combined with the previous measurement. Based on two sets of pincushion distortion data, the deflection circuit, deflection yoke (
DY) Create a transfer function that includes magnetic field distortion, CRT display electronic lens distortion, mechanical distortion, etc., and write an appropriate correction waveform shape, correction amount, or both as a function from the calculation result in ROM 2A. . This forms a pincushion distortion correction table.

Further, the readout control means 1A controls the readout of correction table information from the ROM 2A,
Here, PLL- (phase locked loop) 7
and a counter 8. In general, most of the reliable external signals are only horizontal synchronization signal 1-1s and vertical synchronization signal
A clock 1-1c with a period of 1/6 is required. It is made using PLL7. In other words, the PLL7 phase
A comparator (not shown) is connected to 1 of t-1s and Hc.
The PLL 7 is locked by taking in a clock corresponding to six times the cycle from the counter 8. By this method, for example, 16 words of information can be stored in the ROM in the horizontal direction.
It can be obtained from 2A. In addition, in this embodiment, since the information corresponding to the number of horizontal lines in one vertical period is stored in the ROM, for example, if the number of horizontal lines is 1024, then it is 10 bits.
For example, if there are 16 points in the horizontal direction, a counter 8 of 4 bits, 14 bits in total, is required. Information deviation is prevented by clearing the counter 8 by Vs.

The DAC 3 converts the output of the ROM 2A into an analog signal, and the converted output is sent to the correction deflection current generation means 4A arranged at the subsequent stage. Further, the sawtooth wave generator 6 generates a sawtooth wave at the input timing of the vertical synchronization signal VS, and the generated sawtooth wave is sent to the correction deflection current generation means 4A.

The correction deflection current generating means 4A outputs a pincushion distortion correction deflection current based on the correction table information read from the ROM 2A, and adds the output of the sawtooth wave generator 6 and the output of the DAC 3. adder 9,
A vertical deflection amplifier 10 is provided which supplies a deflection current as shown in FIG. 2 to the vertical DY 5 based on the crimping output of the adder 9.

In the above configuration, under the control of the readout control means 1A based on the vertical synchronization signal Vs and the horizontal synchronization signal 1-1s,
Correction table information is read out from M (pincushion distortion correction table) 2A, and this information is sent as an analog signal to the correction deflection current generation means 4A via the DAC 3.

On the other hand, a sawtooth wave generator 6 based on the vertical synchronization signal Vs
A more sawtooth wave is generated and added to the generated sawtooth wave by the converter 9 of the DAC 3,
The vertical deflection current according to this addition result is the vertical deflection amplifier 1.
0 to the vertical DY5. This vertical deflection current corrects the vertical pincushion distortion of the CRT display.

Next, the case of correcting left and right pincushion distortion will be explained based on FIG. 1(b). The circuit shown in (b) of the same figure is
It has a read control means IB, a ROM 2B, a DSC 3, and a correction deflection current generation means 4B.

A left and right pincushion distortion correction table is formed in the ROM 2B, and in this sense, the ROM 2A is also referred to as a pincushion distortion correction table.

This pincushion distortion correction table is formed in the same manner as above.

Further, the read control means 1B is constituted by a counter 12. In this embodiment, since information for the number of horizontal lines is stored in the ROM, the counter 12 is, for example, 102 horizontal lines.
If there are 4 lines, 10 bits are required. For this reason, synchronization is achieved by using the horizontal synchronizing signal H8 as a clock and using the vertical synchronizing signal @VS as a clear signal for the counter 12.

The DAC 3 converts the output of the ROM 2B into an analog signal, as shown in FIG. ing.

The correction deflection current generating means 4B generates left and right pincushion distortion correction deflection currents based on the output of the DAC 3, and includes a transistor 13 and a horizontal deflection amplifier 14. Horizontal deflection) 7 amplifier 14 is horizontal synchronization signal) -
A deflection current is supplied to the horizontal DY 11 by the input of Is, and by modulating the power supply voltage VCC of the horizontal deflection amplifier 14 with a transistor 13, a correction deflection current as shown in FIG. 4 is supplied.

In the above configuration, under the control of the readout control means 1B, R
Correction table information is read from the OM2B, and this information is supplied to the bases of the transistors 13 through DAC3. Therefore, the Vcc of the horizontal deflection amplifier is modulated by the correction table information, and as a result, the horizontal DY1
1 is supplied with a left and right pincushion distortion correction deflection current, thereby correcting left and right pincushion distortion of the CRT.

As described above, in this embodiment, the pincushion distortion correction table is stored in the ROM (2A, 2
B> is formed, the correction table information is read out from the ROM under the control of the readout control means (1△, 1B), and the pincushion distortion correction deflection current is generated by the correction deflection current generation means (4△, 4B) based on this information. 1, the correction circuit itself can be simplified and the number of adjustment parts can be reduced, and the manufacturing cost of the distortion correction circuit can be reduced. In addition, since the pincushion distortion correction table is created based on the pincushion distortion measurement results at the complement points of the CRT display, the magnetic field distribution distortion of the deflection yoke (DY),
It is possible to correct pincushion distortion that includes the electronic lens distortion of the CRT display and the mechanical and physical distortion of the CRT display. Extremely effective when high definition is required.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made.

For example, in the above embodiment, the circuit for performing upper and lower pincushion distortion (Fig. 1(a)) and the circuit for correcting left stone pincushion distortion (Fig. 1(b)) each have their own ROM2A.
, 2B, but one ROM
It is also possible to form a distortion correction table with 10F inside and a pincushion distortion correction table on the right, and in this way, the circuit can be made more pure.

[Effects of the Invention] As mentioned above, according to the present invention, it is possible to provide a pincushion distortion correction circuit that can be realized at low cost and can perform fine distortion correction.

[Brief explanation of drawings]

Figures 1 (a) and (b) are circuit diagrams of the embodiment of the present invention, Figure 2 is a basic waveform diagram of a conventional correction current, and Figures 3 and 4 are vertical and horizontal deflection currents after correction. FIG. 1A, IB...readout control means, 2A, 2+3...ROM (pincushion distortion correction table), 4A, 4B...correction deflection current generation means.

Claims (1)

[Claims] In a pincushion distortion correction circuit that corrects pincushion distortion of a CRT display, based on pincushion distortion measurement results at multiple points on the CRT display with and without adding a known pincushion distortion correction signal. a pincushion distortion correction table formed by the method, a readout control means for controlling readout of the correction table information, and a correction deflection current generation means for outputting a pincushion distortion correction deflection current based on the readout correction table information. A pincushion distortion correction circuit comprising: