JPH06334895A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To input a video signal by dividing a correction circuit, executing adjustment of picture quality such as contrast and brightness in the intermediate stage, and applying gamma correction corresponding to a display device so as to apply optimum gamma correction to the video signal. CONSTITUTION:An input video signal is A/D-converted 2 and inputted to an image pickup gamma correction circuit 3. The circuit 3 corrects the video signal based on a conversion table for gamma correction suitable for correction of the image pickup camera in a ROM. The video signal corrected by the circuit 3 is inputted to a multiplier 4, in which the video signal is multiplied by a contrast adjustment signal and the product is inputted to an adder 5. The adder 5 adds the product to a brightness adjustment signal, in which the brightness of the video signal input signal is adjusted and the result is fed to a display device gamma correction circuit 6 as a video signal. The circuit 6 corrects the video signal based on a conversion table in the ROM and the signal is fed to a liquid crystal display panel 9 via a D/A converter 7 and an amplifier 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit, and more particularly to video signal processing such as gamma correction when a video signal is displayed on a liquid crystal display device or the like.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional gamma correction circuit in a video signal processing circuit uses a digital gamma correction circuit 10 for image pickup and display device which synthesizes gamma characteristics for image pickup and display device. The video signal input converted into a signal is gamma-corrected and output, and the output is converted into an analog signal by the D / A converter 7 and then input to the amplifier 11,
The amplifier 11 adjusts the contrast and the brightness, and inputs them to the liquid crystal panel 9.

[0003]

However, the liquid crystal panel 9
A desirable gamma correction characteristic is a characteristic α as shown in FIG. 3. When the contrast and brightness are adjusted after the gamma correction, the video signal waveform changes when the contrast and brightness adjustment levels are large, and the liquid crystal changes. There is a problem that the optimum gamma correction cannot be performed because the characteristics deviate from the optimum part. According to the present invention, the correction circuit is divided, the image quality such as contrast and brightness is adjusted in the middle, and the gamma correction corresponding to the display device is performed after the image quality adjustment. The purpose is to make a correction so that a video signal can be input to the display device.

[0004]

A video signal processing circuit according to the present invention comprises a first correction circuit for correcting a video signal input converted into a digital signal and outputting it after correction such as gamma correction for imaging.
The first correction circuit includes at least one arithmetic circuit that calculates and outputs an image quality adjustment signal and a second correction circuit that performs gamma correction for the signal from the arithmetic circuit. The video signal is displayed based on the output from the two-correction circuit.

[0005]

According to the present invention, with the above-described structure, the video signal processing is performed, and the first correction circuit performs the correction processing such as the gamma correction for the image pickup camera on the sending side, and thereafter,
Since the arithmetic circuit adjusts the image quality such as contrast and brightness, and after performing the image quality adjustment, the second correction circuit performs gamma correction corresponding to the display device. It becomes possible to input the video signal to the display device by performing the optimum gamma correction on the video signal.

[0006]

1 is a block diagram showing an embodiment of a video signal processing circuit of the present invention. A video signal input through the input terminal 1 is converted into a digital signal by the A / D converter 2 and input to the gamma correction circuit 3 for image pickup. The image capturing gamma correction circuit 3 uses a ROM, stores a gamma correction conversion table suitable for correction of the image capturing camera on the sending side, and corrects a video signal based on the conversion table. Alternatively, a RAM may be used instead of the ROM, and a conversion table of characteristics for correcting a video signal input as necessary may be written in the RAM to perform processing such as gamma correction or color correction. good. The video signal corrected by the imaging gamma correction circuit 3 is input to the multiplier 4, and for example, the video signal input is quantized by 8 bits in the A / D converter 2, and the multiplier 4 adjusts the contrast of 4 bits. The signal is multiplied and the contrast of the video signal input is adjusted to output as a 12-bit video signal, which is input to the adder 5.

The adder 5 adds the brightness adjustment signal of 10 bits to perform brightness adjustment of the video signal input to 1
Gamma correction circuit 6 for display device as 3-bit video signal
To enter. RO is used as the gamma correction circuit 6 for the display device.
When M is used and, for example, a liquid crystal panel is used as a display device, a conversion table of a characteristic α as shown in FIG.
3 bits are input to the ROM as an address, the video signal is corrected based on the conversion table stored in the ROM, and 8
It is converted into a bit video signal, output, and input to the D / A converter 7. The D / A converter 7 converts the input video signal into an analog signal and inputs it to the liquid crystal panel 9 via the amplifier 8 or the like to display the video signal.

Therefore, after the image quality is adjusted, the gamma correction circuit 6 for the display device performs the gamma correction corresponding to the display device. Therefore, even if the image quality adjustment such as contrast and brightness is performed, it is optimal for the video signal. It is possible to perform various gamma corrections and input to the display device. Further, since the number of bits of the input address of the ROM used as the gamma correction circuit 6 for the display device is set to 13 bits, which is larger than 8 bits, there is an advantage that the arithmetic processing of the image quality adjustment can be performed by a simple integer arithmetic. A plasma display panel or the like may be used as the display device. In this case, the gamma correction circuit 6 for the display device is caused to store a conversion table suitable for gamma correction of the plasma display panel or the like. In this case, since it can be driven by a digital signal, the D / A converter 7 may be omitted.

[0009]

As described above, according to the present invention,
After adjusting the contrast and brightness, the gamma correction circuit for the display device performs gamma correction.
It is possible to provide a video signal processing circuit capable of performing optimum gamma correction on a video signal and inputting it to a display device even if the contrast and brightness are adjusted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal processing circuit of the present invention.

FIG. 2 is a block diagram showing a video signal processing circuit of a conventional example.

FIG. 3 is an explanatory diagram showing a gamma correction characteristic of liquid crystal.

[Explanation of symbols]

 1 Input Terminal 2 A / D Converter 3 Gamma Correction Circuit for Imaging 4 Multiplier 5 Adder 6 Gamma Correction Circuit for Display Device 7 D / A Converter 8 Amplifier 9 Liquid Crystal Panel 10 Gamma Correction Circuit for Imaging and Display Device 11 Amplifier

Claims (3)

[Claims] 1. A first correction circuit for correcting an image signal input converted into a digital signal and outputting the image signal after correction such as gamma correction for image pickup, and calculating and outputting a signal from the first correction circuit and an image quality adjustment signal. And a second correction circuit for gamma-correcting a signal from the arithmetic circuit for a display device, and displaying a video signal based on an output from the second correction circuit. Video signal processing circuit. 2. The arithmetic circuit comprises a multiplier and an adder, and the video signal input to the arithmetic circuit is multiplied by a contrast adjustment signal in the multiplier to adjust the contrast of the video signal, 2. The video signal processing circuit according to claim 1, wherein the adder adjusts the brightness of the video signal by adding it to the brightness adjustment signal. 3. The second correction circuit comprises a ROM storing a conversion table for gamma correction for a display device.
3. The video signal processing circuit according to claim 1, wherein the number of bits of the video signal increased by the arithmetic circuit is converted and output by the OM.