KR19990058500A - Color Image Quality Improvement System for Closed Circuit Television System - Google Patents

Abstract

The apparatus for improving color image quality of a CCTV system according to the present invention is a color image signal inputted through a video input unit as it is input to a decoder as it is through a signal switching switch, and when a black and white image signal is inputted, color subcarrier synthesis is performed. The circuit loads the color subcarrier signal into the back porch section of the monochrome video signal and inputs it to the decoder.

Therefore, when the black and white video signal is input in switching the black and white video signal and the color video signal input through the video input unit by the color image quality improving apparatus of the CCTV system according to the present invention, the black and white video signal synthesizes the color subcarrier signal. By inputting the decoder to the decoder, the PLL speed of the decoder can be improved, thereby improving the channel switching speed and preventing the phase of the color screen from shifting.

Description

Color Image Quality Improvement System for Closed Circuit Television System

The present invention relates to an apparatus for improving color image quality of a CCTV system. More particularly, in a system in which a color image signal and a black and white image signal are mixed from a plurality of video cameras, a color subcarrier is synthesized and input to a decoder. Therefore, the present invention relates to a color image quality improving apparatus of a CCTV system, which is capable of improving a color screen quality by improving a phase synchronization delay of a color image signal.

As is well known, Closed Circuit Tele-Vision (hereinafter referred to as CCTV) systems include one or more video cameras that capture surveillance objects, monitors that output video from video cameras, and video cameras. It is composed of a VCR for recording the image captured by the video to be reproduced later. These CCTV systems are currently used for surveillance in banks, factories, and supermarkets, and are installed at major intersections to identify traffic conditions.

In the conventional CCTV system, as shown in FIG. 1, a plurality of channel video signals input from one or more video cameras are sequentially switched by the decoder 20 to separate a color difference signal, a luminance signal, and a horizontal / vertical synchronization signal. It is stored in the memory unit 30 and synthesized by the signal stored in the memory unit 30 through the encoder 40 and output through the video output unit 50. In this case, when a monochrome signal and a color signal are mixed and input to a plurality of video channels, the PLL locking for performing phase synchronization with respect to each image signal is delayed in the decoder 20, and thus the phase of the color image signal is changed. In severe cases, there is a problem in that colors are changed or stains are generated on the screen of the color image displayed through the video output unit 50 due to the phase shift of the color image signal. This problem occurs when a black and white signal is input because the burst of the decoder is delayed because there is no color burst signal.

Accordingly, the present invention has been made to solve this problem, and its purpose is to provide a PLL lock for phase synchronization by carrying a color subcarrier signal in a back porch section of a black and white signal when a black and white signal is input from a plurality of video channels. It is to provide a color image quality improvement device of CCTV system that can be stabilized.

In order to achieve the above object, the apparatus for improving color image quality of a CCTV system according to the present invention sequentially converts a plurality of channels of black and white image signals and color image signals inputted from one or more video cameras by a decoder to convert a color difference signal, a luminance signal, and a horizontal signal. / CCTV system configured to separate the vertical synchronization signal and store it in the memory unit, and synthesize the signal stored in the memory unit through an encoder and output the video signal through the video output unit, wherein the buffer temporarily stores the video signal input from the video camera. A clock generator for outputting a control signal for synthesizing the color subcarriers with the black and white video signal among the video signals input through the buffer, and a black and white video signal having the color subcarrier signal output from the clock generator synthesized in the back porch section; The color image signal input from the video camera And a color subcarrier synthesizing circuit section comprising a signal switching switch section for switching to be selectively switched and input to the decoder, and a logic sum gate for controlling the switching operation of the signal switching switch section according to a control signal output from the clock generator. It features.

The control signal output from the clock generator of the color image quality improving apparatus of the CCTV system according to the present invention includes an image identification signal for distinguishing the signal output from the video camera and a color subcarrier for insertion into a back porch section of the monochrome image signal. And a burst gate signal for distinguishing a back porch section of the black and white image signal, wherein the image identification signal and the burst gate signal are applied to an input terminal of the OR gate.

1 is a system block diagram showing the configuration of a conventional CCTV system,

2 is a system block diagram showing the configuration of a color image quality improving apparatus of a CCTV system according to the present invention;

3 is an exemplary view showing a signal waveform of each part of a color subcarrier synthesis circuit according to the present invention.

*** Explanation of symbols for main parts of drawing ***

10: video input, 20: decoder,

30: memory part, 40: encoder,

50: video output unit, 60: memory control unit,

100: color subcarrier synthesis circuit section, 110: clock generator,

120: buffer, 130: logic gate,

140: signal switching switch.

Hereinafter, with reference to the accompanying drawings, the configuration and operation effects of the color image quality improving apparatus of the CCTV system according to a preferred embodiment of the present invention will be described in detail.

2 is a system block diagram showing the configuration of a CCTV system for implementing the present invention. As shown in FIG. 2, the CCTV system for implementing the present invention includes a video input unit 10 that receives image signals photographed from a plurality of video cameras, and a video signal input to the video input unit 10 in a field or frame. A black-and-white video signal is inputted from the video input unit 10 and a decoder 20 for sequentially converting units, separating horizontal / vertical sync signals from the sequentially converted analog video signals, separating luminance and chrominance signals, and then digitally converting them. In this case, the color subcarrier synthesis circuit unit 100 which synthesizes the color subcarrier signal in the back porch section of the black and white image signal and applies it to the decoder 20, and the luminance signal and the color difference which are separated and digitally converted by the decoder 10. The memory unit 30 temporarily storing signals, the memory control unit 60 controlling timing of writing and reading of the memory unit 30, and the memory unit 30 The encoder 40 converts a digital luminance and chrominance signal into an analog signal and combines the synchronization signal coming through the memory controller 60 into a video signal and synthesizes the converted luminance and chrominance signal into an image signal. And a video output unit 50 for outputting the divided video signal to the screen of the monitor in a split screen or a single screen.

In the above-described configuration, the color subcarrier synthesis circuit 100 may temporarily store a video signal input from the video input unit 10 and a color to a black and white video signal input through the buffer 120. A clock generator 110 for outputting a control signal for synthesizing a subcarrier, and a burst gate signal indicating a timing of synthesizing a video signal identification signal ID and a color subcarrier signal output from the clock generator 110; The logical sum gate 130 for performing the OR operation and the color image signal input from the video input unit 10 and the color subcarrier signal fsc output from the clock generator 110 are synthesized into a back porch section of the monochrome image signal to obtain a decoder ( And a signal switching switch unit 140 which is switched to selectively input the input signal 20.

On the other hand, the control signal output from the clock generator 110 having the above-described configuration is composed of an image signal identification signal ID, a color subcarrier signal fsc, and a burst gate signal, and among these control signals, an image signal. When the identification signal ID is a color image signal, a 'high' level signal is output, and when it is a blackbell image signal, a 'low' level signal is output. In addition, the color subcarrier signal fsc is a signal of 3.58 MHz, which is synthesized in the back porch section of the black and white video signal, and the burst gate signal is output as a 'low' level signal during the back porch section of the black and white video signal. In addition, except for the back porch section, the signal is output as a 'high' level signal to designate a composition position of the color subcarrier signal fsc.

The operation of the color image quality improving apparatus of the CCTV system according to the present invention having such a configuration will be described below.

First, when a black and white image signal is input from the video input unit 10, the black and white image signal input through the video input unit 10 is temporarily stored in the buffer 120, and then input to the clock generator 110. It is applied to the video signal terminal of the switching switch 140. The clock generator 110 outputs a carrier signal of 3.58 MHz through the color subcarrier signal terminal fsc in order to synthesize the color subcarrier signal fsc in the back porch section of the black and white image signal. In addition, since a black and white video signal is input to the video signal identification terminal ID, a signal having a 'low' level is output. The burst gate signal terminal outputs a 'high' level in the section except for the back porch section of the input black and white video signal, and outputs a color subcarrier signal (fsc) by combining the black and white video signal in the back porch section. To do this, a low level signal is output.

Accordingly, in the back porch section of the black and white video signal, a low level signal is applied to the input of the OR gate 130 through the image signal identification terminal and the burst gate signal terminal, so that the OR gate 130 is' The low level signal is output to the signal switching switch unit 140. At this time, the signal switching switch 140 receiving the 'low' level signal from the OR gate 130 switches the contact point of the switch from the image signal terminal to which the image signal output from the video input unit 10 is input to the color subcarrier terminal. The black and white video signal carrying the color subcarrier signal fsc is input to the decoder 20.

However, when the color image signal is input through the video input unit 10, since the image signal identification signal ID having the 'high' level is output from the clock generator 110, the OR gate 130 may perform the signal switching switch unit ( 140, a high level signal is output. Therefore, the switch contact of the signal switching switch unit 140 is connected to the video signal terminal to input the color video signal output from the video input unit 10 to the decoder 20.

3 is an exemplary view showing a signal waveform of each part of a color subcarrier synthesis circuit according to the present invention. As shown in FIG. 3, when the image signal is a color image signal, the image signal is directly input to the decoder 20 through the signal switching switch 140, and when the image signal is a monochrome image signal, a back porch of the monochrome image signal is displayed. Since a color subcarrier signal fsc of 3.58 MHz is loaded in the section and input to the decoder 20, a stable PLL locking operation is performed when the video signal is switched.

The apparatus for improving color image quality of a CCTV system according to the present invention is not limited to the above-described embodiments, and may be variously modified and implemented within the range permitted by the technical idea of the present invention.

As described above, in the color image quality improving apparatus of the CCTV system according to the present invention, when the image signal input through the video input unit is a color image signal, it is directly input to the decoder through the signal switching switch unit, and the monochrome image signal is input. In this case, the color subcarrier synthesis circuit loads the color subcarrier signal into the back porch section of the monochrome video signal and inputs it to the decoder.

Therefore, when the black and white video signal is input in switching the black and white video signal and the color video signal input through the video input unit by the color image quality improving apparatus of the CCTV system according to the present invention, the black and white video signal synthesizes the color subcarrier signal. By inputting the decoder to the decoder, the PLL speed of the decoder can be improved, thereby improving the channel switching speed and preventing the phase of the color screen from shifting.

Claims (2)

Multiple channels of black and white video signals and color video signals input from one or more video cameras are sequentially switched by the decoder to separate the chrominance signal, the luminance signal, and the horizontal / vertical sync signal, and store them in the memory unit. In the CCTV system to synthesize the signals stored in the video output unit, A buffer for temporarily storing an image signal input from the video camera; A clock generator for outputting a control signal for synthesizing a color subcarrier with a black and white video signal among the video signals inputted through the buffer; A signal switching switch unit configured to switch the color subcarrier signal output from the clock generator to be input to the decoder by selectively switching a monochrome image signal synthesized in a back porch section and a color image signal input from the video camera; And a color subcarrier synthesizing circuit unit comprising a logic sum gate for controlling a switching operation of the signal switching switch unit according to a control signal output from the clock generator. The control signal output from the clock generator includes an image identification signal for distinguishing a signal output from the video camera, a color subcarrier signal for insertion into a back porch section of the black and white video signal, and a black and white video signal. And a burst gate signal for distinguishing a back porch section of the apparatus, wherein the image identification signal and the burst gate signal are applied to an input terminal of the OR gate.