JPH06337650A - Video processing device - Google Patents

Abstract

PURPOSE:To obtain gradation of video displayed on a display device and to prevent void of white color of video, in a video processing device. CONSTITUTION:In a video processing device in which an input composite (video) signal is processed in the prescribed way and made R, G, B signals, a display panel is driven based on the R, G, B signals, and video can be displayed on the display panel, the composite signal (video) is inputted to a gain amplifying section 1 and a horizontal synchronism separating section 2, a horizontal synchronizing signal separated in the horizontal synchronism separating section 2 is inputted to an AGC detecting section 3, a signal obtained by detecting the horizontal synchronizing signal in the AGC detecting section 3 is made a control signal of the gain amplifying section 1, a peak-to-peak value of the composite signal is varied in accordance with a value of the horizontal synchronizing signal, the peak-to-peak value of the composite signal is kept a constant value (1Vpp) not so as to exceed 1Vpp, and the constant composite signal is processed in the prescribed way.

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 technique for displaying a video image of a composite (video) signal on a display, and more particularly to a video processing device for eliminating a white crushed display image. is there.

[0002]

2. Description of the Related Art This video processing apparatus performs predetermined signal processing on an input composite signal to obtain R, G, B signals, and based on these R, G, B signals, a liquid crystal display panel (hereinafter referred to as LCD) or plasma. It is displayed on a display panel (hereinafter referred to as PDP).

When an LCD is used as a display,
The video processing device described above is based on R, G, B signals obtained by predetermined signal processing such as Y / C separation processing and color demodulation processing
D is driven to display an image, and when the image is displayed, the gradation of the image is obtained based on, for example, a color demodulated signal.

When a PDP is used as the display, the video processing apparatus obtains R, G, B signals by predetermined signal processing such as Y / C separation processing and color demodulation processing, and at the same time sets the level of the color demodulated signal. The number of times of light emission of each cell of the PDP is converted, the PDP is driven based on the R, G, and B signals to display an image, and the gradation of the image is obtained.

[0005]

By the way, since the voltage / light transmission characteristic of the liquid crystal (normally white) is as shown in FIG. 2, the inclination of the light transmission characteristic curve is extremely small at a high applied voltage of the liquid crystal. Become. On the other hand, for example, a composite signal from a laser disk or the like may be larger than 1 Vpp (peak to peak).

In such a case, if the display is an LCD, in the above image processing apparatus, gradation is taken in a portion (bright side of image) where the magnitude of the input composite signal exceeds a constant value of 1 Vpp. It is difficult to obtain, that is, a normal gradation can be obtained, and as a result, an image of white crushed (a state in which the gradation of a bright image is bad) is displayed, and the image quality is deteriorated.

If the display is a PDP,
In the image processing device, since the level of the color demodulated signal is converted into the number of times of light emission of the PDP to obtain the gradation,
Similar to the above, it is difficult to obtain the gradation, and a white-blank image is displayed, resulting in deterioration of image quality.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image processing device capable of suppressing the underexposure of an image displayed on a display such as an LCD or PDP and improving the image quality. To provide.

[0009]

In order to achieve the above object, the present invention performs predetermined signal processing on an input composite (video) signal to obtain R, G, B signals, and based on the R, G, B signals. In a video processing device capable of driving a display to display an image on the display, the synchronous portion of the composite signal is detected, and the size of the composite signal is changed according to the detected synchronous portion. The gist is that the magnitude of the composite signal is kept constant, and the composite signal having the constant magnitude is subjected to predetermined signal processing to obtain R, G, B signals.

[0010]

With the above means, the magnitude of the composite signal does not exceed, for example, 1 Vpp. Therefore, when an LCD (liquid crystal display) is used as the display,
The part where the inclination of the light transmission characteristic curve of the liquid crystal is small is not used, and the gradation on the bright side of the display image is obtained.

When a PDP (plasma display panel) is used as the display, the bright side level of the signal obtained by color demodulating the composite signal by the predetermined signal processing is obtained, so that the gradation of the bright side of the display image is as usual. Can be obtained.

As a result, the image displayed on the display does not have to be crushed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A video processing apparatus according to the present invention is a peak-to-peak (peak to peak) signal of an input composite (video) signal.
When the peak) changes, the video part and the sync part of the same composite signal change at the same rate, the size of this sync part (amplitude of the horizontal sync pulse) is detected, and the peak of the composite signal is detected by this detected value. The tow peak is varied to keep the peak tow peak of the composite signal at a constant value (1 Vpp).

Therefore, as shown in FIG. 1, this video processing apparatus has a gain amplification section (gain amplification section) 1 for varying the magnitude (peak to peak) of an input composite (video) signal, and the same input composite signal. Of the horizontal sync signal (horizontal sync pulse), and a control for varying the gain of the gain amplifier 1 according to the magnitude of the separated horizontal sync signal (amplitude of the horizontal sync pulse). An automatic gain detection (AGC detection) unit 3 for outputting a signal is provided.

Although not shown, this video processing apparatus is provided with the above circuit at the input stage, and a signal (composite signal) obtained by the circuit is subjected to predetermined processing including Y / C separation processing, color demodulation processing and the like as in the conventional case. It has a circuit configuration that performs signal processing.

Next, the operation of the video processing apparatus having the above configuration will be described in detail. First, it is assumed that the magnitude of the input composite signal (peak to peak) is larger than 1 Vpp shown in FIG. 3, for example.

At this time, the horizontal sync separation unit 2 separates the horizontal sync signal of the input composite signal and outputs it to the AGC detection unit 3. The AGC detection unit 3 detects the horizontal sync signal and the detected signal is detected. Is used as a control signal for the gain amplifier 3. The level of this control signal varies depending on the magnitude of the input composite signal. That is, when the peak to peak of the input composite signal increases, the video portion and the synchronization portion of the same composite signal increase at the same rate.

Then, the gain amplifying section 1 includes the AGC detecting section 3
The gain is varied according to the control signal output from the input signal to change the size of the input composite signal. When the peak-to-peak of the input composite signal becomes larger than 1 Vpp, the amplitude of the horizontal synchronizing signal of the same composite signal also becomes large, so that the level (voltage value) of the control signal output from the AGC detection unit 3 becomes large.

The control signal reduces the gain of the gain amplifying section 3 and thus the input composite signal. Moreover, since the control signal has a value corresponding to the magnitude of the horizontal synchronizing signal, the magnitude of the input composite signal is maintained at the normal 1 Vpp, and the magnitude of the composite signal does not exceed 1 Vpp.

Therefore, LCD (liquid crystal display)
By providing the circuit having the above-described configuration in the video processing device that drives, it is possible to suppress the whiteout of the video displayed on the LCD (liquid crystal display). That is, the peak-to-peak of the composited signal, which is subjected to the predetermined signal processing in the conventional video processing apparatus, becomes constant and becomes 1 Vpp.
This is because, since the light transmission characteristic curve of the liquid crystal has a small inclination, it is not necessary to use the portion where the inclination of the light transmission characteristic curve of the liquid crystal is large, and the gradation on the bright side of the image can be obtained as usual.

Further, by providing the circuit of the above configuration in the image processing device for driving the PDP (plasma display panel), it is possible to suppress the whiteout of the image displayed on the LCD (liquid crystal display). That is, the peak-to-peak of the composite signal, which is subjected to the predetermined signal processing in the same manner as in the conventional video processing apparatus, becomes constant and the peak to peak becomes 1 Vp
This is because, since it does not exceed p, the bright side level of the signal demodulated by the same composite signal can be obtained and the gradation of the image can be obtained.

[0022]

As described above, according to the present invention, a composite (video) signal is subjected to predetermined signal processing into R, G, B signals, and a display panel is displayed based on these R, G, B signals. In a video processing device that can be driven to display video on the same display panel, the synchronous portion of the composite (video) signal is detected, and the peak-to-peak of the composite signal is varied by this detection value to determine the peak of the composite signal. The toe peak is maintained at a constant value (1 Vpp), that is, the peak toe peak of the composite signal does not exceed 1 Vpp. Therefore, when an LCD or PDP is used as the display, the gradation on the bright side of the displayed image is It is possible to obtain it as usual, and it is possible to improve the image quality as a result of eliminating the underexposure of the displayed image. Kill.

[Brief description of drawings]

FIG. 1 is a schematic partial block diagram of a video processing apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic graph showing a light transmission characteristic curve of liquid crystal.

FIG. 3 is a schematic graph showing a composite (video) signal.

[Description of Reference Signs] 1 gain amplification section (gain amplification section) 2 horizontal sync separation section (sync separation means) 3 AGC detection section (automatic gain detection section)

Claims (3)

[Claims] 1. An input composite (video) signal is subjected to predetermined signal processing to obtain R, G, B signals, and a display is driven based on the R, G, B signals so that an image can be displayed on the display. In the video processing device, the synchronous portion of the composite signal is detected, the magnitude of the composite signal is changed according to the detected synchronous portion, the magnitude of the composite signal is kept constant, and the fixed composite An image processing apparatus characterized in that signals are subjected to predetermined signal processing to obtain R, G, B signals. 2. An input composite (video) signal is subjected to predetermined signal processing to obtain R, G, B signals, and a liquid crystal display panel is driven based on the R, G, B signals to display an image on the liquid crystal display panel. In a displayable video processing device, a gain amplification means for varying the size of the composite signal, a sync separation means for separating a horizontal sync signal (horizontal sync pulse) of the composite signal, and a separated horizontal sync signal of the separated horizontal sync signal. Automatic gain detection means for outputting a control signal for varying the gain of the gain amplifying means according to the magnitude (amplitude of the horizontal synchronizing pulse), the magnitude of the composite signal is constant, and the constant composite signal Signal processing to R, G, B
A video processing device characterized by being a signal. 3. An input composite (video) signal is subjected to predetermined signal processing to obtain R, G, B signals, and a PDP is driven based on the R, G, B signals so that an image can be displayed on the PDP. In a video processing device, a gain amplifying means for varying the size of the composite signal, a sync separating means for separating a horizontal sync signal (horizontal sync pulse) of the composite signal, and a size of the separated horizontal sync signal (horizontal An automatic gain detection means for outputting a control signal for varying the gain of the gain amplification means in accordance with the amplitude of the sync pulse), the magnitude of the composite signal is constant, and the constant composite signal is predetermined. R, G, B processed
A video processing device characterized by being a signal.