JPH05236493A - Black-and-white video signal output device - Google Patents

Abstract

PURPOSE:To output a black-and-white video signal including a color burst signal from the color video camera, which outputs a composite color video signal in the NTSC system, without complicating the circuit constitution. CONSTITUTION:In the color picture reproducing mode, an analog switch 30 is switched to the position shown by a broken line. A chroma signal C and a luminance signal Y are synthesized by an adder to output the composite color video signal in the NTSC system. In the black-and-white picture reproducing mode, the analog switch 30 is switched to the position shown by a continuous line by the signal from an AND gate 35, and color information modulated by a chrominance subcarrier is not outputted. However, the analog switch 30 is switched to the position shown by the broken line by the signal from a control pulse generator to output the black-and-white video signal where the color burst signal is synthesized with the luminance signal Y while the color burst signal exists from the leading edge of the horizontal synchronizing signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monochrome video signal output device incorporated in a color video camera which outputs an NTSC color composite signal (composite color video signal).

[0002]

2. Description of the Related Art Since solid-state image pickup devices such as CCD image sensors have been put into practical use, various types of image pickup video cameras such as commercial and consumer movie video cameras and still video cameras have been commercialized. Most of these video cameras are now capable of color imaging. Some color video cameras are used, for example, to capture a document such as a report at a conference table and simultaneously display the image on several CRTs. Since general documents are often black and white originals, a monochrome type video camera may be used when used only for the above purposes, but in reality a color video camera is used to support color originals. Is normal.

Since a general color video camera is designed to reproduce an image on a home-use television receiver, the final video signal is output as a composite color video signal of the NTSC system. Especially when reproducing a monochrome image. There is known a color video camera capable of outputting not only a composite color video signal but also a black and white video signal for the purpose of reproducing a high quality image without mixing of color noise and deviation of white balance. 4 and 5 each show a conventional example for outputting a black and white video signal.

FIG. 4 shows a signal from the color / monochrome (COL / BW) switching signal terminal 2, which is a chroma signal C modulated by a color subcarrier (color subcarrier: about 3.58 MHz) by the analog switch 3. In the black-and-white mode, a black-and-white video signal containing a synchronizing signal such as a horizontal synchronizing signal H in addition to the luminance data signal S is output. Further, in the example shown in FIG. 5, when the black-and-white mode signal is input from the switching signal terminal 2, the two analog switches 4 and 5 are set to the illustrated positions, and the color difference signal is generated before the modulator 6 modulates the color subcarrier. Cut "RY" and "BY". As a result, the finally obtained output signal becomes a monochrome video signal including the luminance data signal S, the synchronizing signal such as the horizontal synchronizing signal H, and the color burst signal CB superimposed by the modulator 6.

[0005]

However, in the case of the conventional method shown in FIG. 4, the black-and-white image signal finally obtained does not include the color burst signal. The color burst signal is used as a signal that provides a phase reference when identifying hue information from a composite color video signal,
It is a signal wave having the same frequency as the color subcarrier and having about 10 cycles. This color burst signal is not only used for identifying hue information, but is also used for synchronously driving a plurality of color video cameras.
It is often used as a synchronizing signal for "error LOCK". However, for the above reason, if there is no color burst signal, the color video camera that outputs the black and white video signal cannot be used as a reference for synchronization. For example, a black and white image and a color image are split on a CRT screen. Even if an attempt is made to combine the images, a so-called synchronous flow occurs and good image processing cannot be performed. Also, FIG.
The above-mentioned problem does not occur because the black-and-white video signal obtained by the method of 1) includes a color burst signal, but an analog switch is required for each of the color difference signals "RY" and "BY", and the circuit Becomes complicated.

In order to solve the above problems, the present invention provides
It is an object of the present invention to provide a black and white video signal output device capable of taking out a black and white video signal including a color burst signal by using only one switching means.

[0007]

In order to achieve the above object, the present invention takes out only a color burst signal from a chroma signal, synthesizes it with the luminance signal, and outputs the synthesized signal as a monochrome video signal. It was done.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 3 schematically showing the structure of a color video camera using the present invention, a subject image is formed on a CCD image sensor 9 through an image pickup lens 7 and an optical low pass filter 8. CCD image sensor 9
In the photocathode of, a complementary color type color separation filter in which minute color filters transmitting only cyan, yellow, magenta and green color lights are arranged in a matrix is incorporated, and the CCD drive pulse generator 10 and the CCD driver 1 are provided.
The CCD image sensor 9 is driven by 1. This allows the CCD image sensor 9 to output two types of color signals C.
1 and C2 are serially output at regular intervals. C
The CD image sensor 9 includes two CDS circuits 12, 1
3 are connected in parallel. These CDS circuits 12, 1
3 is an output signal “CCD by correlated double sampling
The two types of color signals C1 and C2 are separated from "OUT" and output. Therefore, the CDS circuits 12 and 13 are supplied with sampling pulses for correlated double sampling from the CCD drive pulse generator 10.

The color signals C1 and C2 thus obtained are input to the color separation matrix circuit 15 and converted into primary color signals R (red signal), G (green signal) and B (blue signal) by matrix operation, and at the same time The luminance signal Y _H is calculated by the sampling process. The primary color signals R, G, B and the luminance signal Y from the color separation matrix circuit 15
_{The H} is then input to the gain control circuit 16.
The gain control circuit 16 automatically adjusts the white balance by adjusting the gain for each color channel based on the balance of the signal levels of the primary color signals R, G, and B. Of course, the gain adjustment for each color channel can be performed based on the externally input data for white balance adjustment.

Since the primary color signals R, G, B obtained by the above circuit processing are values influenced by the spectral transmittance of the individual color filters constituting the color separation filter, the actual subject is In many cases, it does not accurately reflect the hue or saturation of the color. Therefore, the linear matrix circuit 18 is used to perform matrix calculation on the primary color signals R, G, B based on the correction coefficient corresponding to the spectral transmittance of each color filter. The correction coefficient used for this calculation is preset in the microcomputer 20. Of course, it is also possible to perform the correction gain adjustment for each color channel based on the color correction data externally input.

The signal processing circuit 22 receives the corrected primary color signals R,
Upon receiving the G and B and the luminance signal Y _H and the input of correction data from the microcomputer 20, γ correction, knee white clipping processing, etc. are performed so as to satisfy the conditions at the time of image reproduction. Subsequently, the primary color signals R, G, B and the luminance signal Y _H are input to the band correction circuit 24. Single-chip color video camera is generally the bandwidth is narrow for the color signal is in the difficulty, the band correction circuit 24 in order to resolve this difficulty, the luminance signal Y _H is using the fact bandwidth is wider in the high range and, it has to compensate by using the luminance signal Y _H and the insufficient band of the color signal.

The band-corrected primary color signals R, G, B are output as they are to the external output terminal as RGB signals, while being input to the encoder 25. The encoder 25 receives the primary color signals R, G, B and receives the luminance signal Y and the color difference signal "R-.
Three types of signals, "Y" and "BY", are created, and combined processing with vertical and horizontal sync signals is also performed, and 3.58 MHz.
Balanced modulation processing using the color sub-carrier is converted into an NTSC composite color video signal and output. Therefore, either the RGB signal or the NTSC composite color video signal can be used depending on the application and the reproducing device. If the output of the S video signal is also desired, the encoder 25 may be provided with a function of outputting to the S video signal.

The encoder 25 includes the synthesizing circuit shown in FIG. This synthesizing circuit is for synthesizing a chroma signal C obtained by modulating a color difference signal with a color subcarrier and a luminance signal Y combined with a composite synchronizing signal. The form of the signal appearing on each signal line in FIG. As shown in FIG. The chroma signal C of the signal line is the color burst signal C
B, and a color data signal C containing information on hue and color saturation
It consists of D and. The luminance signal Y of the signal line is a combination of the luminance data signal S with a horizontal synchronizing signal H, a vertical synchronizing signal, and an equalizing pulse, and the signal level thereof is also standardized with reference to the pedestal level.

As shown in FIG. 1, an analog switch 30 is provided on the signal line. The analog switch 30 maintains the connection position shown by the broken line when a low level signal is input to its control terminal, and becomes the connection position shown by a solid line when a high level signal is input. Then, when the analog switch 30 is in the connection position shown by the broken line, the chroma signal C remains as it is and the adder 3
2 and is combined with the luminance signal Y. As a result, as shown in FIG. 2, an NTSC composite color video signal is output to the signal line.

A control pulse generator 33 is connected to the signal line. The control pulse generator 33 is composed of, for example, a one-shot multivibrator, and outputs a control pulse that is at a low level for a certain time Δ when the leading edge of the horizontal synchronizing signal H included in the luminance signal Y is detected. Then, it is supplied to one input terminal of the AND gate 35. The constant time Δ is determined with reference to the time point when the output period of the color burst signal CB included in the chroma signal C ends. At the other input terminal of the AND gate 35, the switching signal "CO
L / BW ”is input. The switching signal becomes high level when the user selects the monochrome mode, and becomes low level when the normal color mode is set.

When the user selects the image reproduction in the color mode, one input terminal of the AND gate 35 is always at the low level, so that the analog switch 30 is always in the connection position of the broken line regardless of the change of the control pulse. is there. Therefore, the normal NTSC composite color image signal is output to the signal line as shown in FIG.

On the other hand, when the image reproduction in the monochrome mode is selected, one input terminal of the AND gate 35 is maintained at the high level. Then, the luminance signal Y is supplied to the signal line, and when the leading edge of the horizontal synchronizing signal H is detected, a low-level control pulse is generated with a time width Δ. When this control pulse is input to the AND gate 35, the output of the AND gate 35 becomes low level, and the analog switch 30 is switched to the broken line position. Further, since both input terminals of the AND gate 35 are at the high level during the period in which the control pulse is not generated, the analog switch 30 is switched to the solid line position and the chroma signal C is cut off. Therefore, the output signal obtained from the signal line in the black and white mode is an NTSC which is a combination of a synchronizing signal such as a horizontal synchronizing signal H, a color burst signal CB and a luminance data signal S as shown in FIG.
It becomes a black and white video signal of the system.

Even if a color burst signal is included in the black-and-white video signal as described above, there is no problem in reproducing a black-and-white image, and conversely, by using this color burst signal as a reference synchronizing signal, another color video signal can be obtained. The camera can be genlocked with this black-and-white video signal and driven synchronously, which is very convenient when synthesizing a black-and-white image and a color image on a CRT.

Although the present invention has been described above based on the illustrated embodiment, the pulse width Δ of the control pulse does not necessarily have to reach the end of the color burst signal.
For example, it may be completed before the subsequent video period. Further, the generation timing of the control pulse does not necessarily have to be the leading edge of the horizontal synchronizing signal, and the pedestal level which is the signal level of the back porch and the front porch is detected by the comparator having a good high frequency response and the luminance signal Y is detected. The low level control pulse may be generated during the period when the signal level is equal to or lower than the pedestal level.

[0020]

As described above, according to the black-and-white video signal output device of the present invention, the black-and-white video signal including the color burst signal can be accurately output with a simple circuit configuration. Therefore, this black-and-white video signal can be used as a synchronization signal for genlock.
Therefore, it becomes possible to easily synchronize with a composite color video signal sent from another color video camera, and it becomes very convenient because image synthesis and various video signal processing can be performed.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an example of a monochrome image output device using the present invention.

FIG. 2 is a time chart diagram showing an outline of signal waveforms appearing on signal lines in the circuit block of FIG.

FIG. 3 is a schematic configuration diagram of a video camera using the present invention.

FIG. 4 is a circuit block diagram showing an example of a conventional monochrome video signal output device.

FIG. 5 is a circuit block diagram showing another example of a conventional monochrome video signal output device.

[Explanation of symbols]

 30 analog switch 32 adder 33 control pulse generator 35 AND gate

Claims (1)

[Claims] 1. A color video camera for obtaining an NTSC composite color video signal by synthesizing a luminance signal and a chroma signal which is modulated by a color subcarrier and includes a color burst signal. A black-and-white video signal output device, wherein only a color burst signal is taken out from the inside and combined with the luminance signal, and the combined output is obtained as a black and white video signal.