JP3017873B2 - Black and white video signal output device - Google Patents

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 for outputting a color composite signal (composite color video signal) of the NTSC system.

[0002]

2. Description of the Related Art Since solid-state imaging devices such as CCD image sensors have been put into practical use, various types of video cameras for imaging, such as commercial and consumer movie video cameras and still video cameras, have been commercialized. Most of these video cameras can capture color images. Some color video cameras are used, for example, to capture a document such as a report on a conference table and simultaneously display the image on several CRTs. Since general documents are often black-and-white documents, a monochrome video camera may be used when used only for the above applications, but a color video camera is used in order to be able to handle color documents in practice. Is common.

Since a general color video camera is intended to reproduce an image on a home television receiver, the final video signal is output as a composite color video signal of the NTSC system. 2. Description of the Related Art A color video camera capable of outputting not only a composite color video signal but also a black-and-white video signal has been known for the purpose of reproducing a high-quality image without color noise mixing or white balance shift. 4 and 5 each show a conventional example for outputting a black and white video signal.

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

[0005]

However, in the case of the conventional system shown in FIG. 4, the finally obtained monochrome video signal does not include a color burst signal. The color burst signal is used as a signal that provides a phase reference when identifying hue information from the composite color video signal,
It is a signal wave of about 10 cycles having the same frequency as the color subcarrier. This color burst signal is used not only for identifying hue information but also for genlock (GEN) when a plurality of color video cameras are to be driven synchronously.
This is often used as a synchronization signal for an E.R. However, if there is no color burst signal for the above reason, the color video camera outputting the black and white video signal cannot be used as a synchronization reference. 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 images, a so-called synchronous flow occurs, and good image processing cannot be performed. FIG.
Since the black-and-white video signal obtained by the above method includes a color burst signal, the above problem does not occur. However, an analog switch is required for each of the color difference signals "RY" and "BY", and a circuit is required. Is complicated.

The present invention has been developed to solve the above problems.
It is an object of the present invention to provide a black-and-white video signal output device capable of extracting a black-and-white video signal including a color burst signal simply by using a plurality of switching means.

[0007]

In order to achieve the above object, according to the present invention , a luminance signal including a horizontal synchronizing signal and a color
Wave modulation and color burst signal
And a chroma signal containing the color data signal in time series.
Composite video signal of NTSC system
Output video signal to a color video camera
In order to incorporate the device, this black and white video signal output device
Is provided before the adding means, and the chroma signal is provided to the adding means.
The ON position and the chroma signal that are allowed to be supplied are added
Between the off position, which prohibits supply to the means.
Replaceable switching means and provided before the adding means
Constant in response to the horizontal sync signal contained in the luminance signal
A control pulse generator that generates a control pulse with a width and a color
When the mode is set, the control pulse is invalidated and the switch is disabled.
The switching means is maintained at the ON position and the
Output a composite color video signal.
Inputting the control pulse to switching means,
Turns on the switching means for a certain period corresponding to the width
By switching to the off position during other periods,
Separating the color burst signal from the chroma signal
The luminance signal is supplied to the
Control means for outputting a black and white video signal with a burst signal added
And a stage .

[0008]

FIG. 3 schematically shows the structure of a color video camera using the present invention. A subject image is formed on a CCD image sensor 9 via an imaging lens 7 and an optical low-pass filter 8. CCD image sensor 9
A complementary color separation filter in which minute color filters that transmit only the respective color lights of cyan, yellow, magenta, and green, for example, are arranged in a matrix, is incorporated in the photocathode. The CCD driving pulse generator 10 and the CCD driver 1
1 drives the CCD image sensor 9. Thus, two types of color signals C are output from the CCD image sensor 9.
1 and C2 are output serially 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.
OUT ", two types of color signals C1 and C2 are separated 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 obtained in this way are input to a color separation matrix circuit 15, where they are converted into primary color signals R (red signal), G (green signal), and B (blue signal) by a matrix operation. luminance signal Y _H is calculated by the sampling process. Then, the primary color signals R, G, B and the luminance signal Y from the color separation matrix circuit 15 are output.
_H is input to the gain control circuit 16 next.
The gain control circuit 16 adjusts the gain for each color channel based on the balance of the signal levels of the primary color signals R, G, and B, and automatically performs white balance adjustment. Of course, it is also possible to perform gain adjustment for each color channel based on externally input white balance adjustment data.

The primary color signals R, G, and B obtained by the above circuit processing have values influenced by the spectral transmittance of each color filter constituting the color separation filter. In many cases, the hue and color saturation are not correctly reflected. For this reason, a linear matrix circuit 18 is used, and a matrix operation is performed on the primary color signals R, G, and B based on a correction coefficient corresponding to the spectral transmittance of each color filter. The correction coefficient used for this calculation is set in the microcomputer 20 in advance. 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 outputs the corrected primary color signals R,
Receiving G, B and the luminance signal Y _H, and receiving correction data from the microcomputer 20, it performs γ correction, knee / white clip processing, etc. so as to satisfy the conditions for image reproduction. Subsequently the primary color signals R, G, B and the luminance signal Y _H is inputted to the band correction circuit 24. The single-panel color video camera generally has a drawback in that the band of the color signal is narrow, but the band correction circuit 24 uses the fact that the luminance signal Y _H has a wide band even in the high band to solve this drawback. and, it has to compensate by using the luminance signal Y _H and the insufficient band of the color signal.

The primary color signals R, G, and B after the band correction are output to the external output terminals as they are as RGB signals, while being input to the encoder 25. The encoder 25 receives the primary color signals R, G, and B, and receives the luminance signal Y and the color difference signal “R−G”.
Y "and" B-Y ", and furthermore, a synthesizing process with vertical and horizontal synchronizing signals, and 3.58 MHz
And performs a balanced modulation process using the chrominance sub-carrier to convert to an NTSC composite color video signal and output it. Therefore, any of the RGB signal and the NTSC composite color video signal can be used depending on the application and the playback device. If output of an S video signal is also desired, an output function for an S video signal may be added to the encoder 25.

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. This is as shown in FIG. The chroma signal C of the signal line is a color burst signal C
B and a color data signal C including information on hue and color saturation.
D. The luminance signal Y of the signal line is a combination of the luminance data signal S, the horizontal synchronizing signal H, the vertical synchronizing signal, and the equalizing pulse, and the signal level is standardized on the basis of 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 indicated by the broken line when a low level signal is input to its control terminal, and assumes the connection position indicated by a solid line when a high level signal is input. When the analog switch 30 is at the connection position shown by the broken line, the chroma signal C
2 and is combined with the luminance signal Y. Thereby, as shown in FIG. 2, the composite color video signal of the NTSC system is output to the signal line.

A control pulse generator 33 is connected to the signal line. The control pulse generator 33 is constituted by, for example, a one-shot multivibrator, and outputs a control pulse which becomes low level for a certain time Δ when detecting the leading edge of the horizontal synchronizing signal H included in the luminance signal Y. Then, the signal is supplied to one input terminal of the AND gate 35. The fixed time Δ is determined with reference to the end of the output period of the color burst signal CB included in the chroma signal C. A switching signal “CO” from the microcomputer 20 is input to the other input terminal of the AND gate 35.
L / BW "is input. The switching signal goes high when the user selects the black and white mode, and goes low when the user switches to the normal color mode.

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 at the connection position indicated by the broken line regardless of the change of the control pulse. is there. Therefore, as shown in FIG. 2, an ordinary NTSC composite color video signal is output to the signal line.

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 a 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 with a time width Δ is generated. 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 position indicated by the broken line. Since both input terminals of the AND gate 35 are at a high level during a period in which no control pulse is generated, the analog switch 30 is switched to the position indicated by the solid line, and the chroma signal C is discarded. Therefore, the output signal obtained from the signal line in the monochrome mode is an NTSC signal obtained by synthesizing a synchronization signal such as a horizontal synchronization signal H, a color burst signal CB, and a luminance data signal S as shown in FIG.
This is a black and white video signal.

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

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

[0020]

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

[Brief description of the drawings]

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

FIG. 2 is a time chart schematically showing a signal waveform appearing on a signal line in the circuit block of FIG. 1;

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]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-149979 (JP, A) JP-A-2-79579 (JP, A) JP-A-4-43790 (JP, A) JP-A 62-79 207087 (JP, A) Jikken Sho 57-37558 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/64 H04N 9/70 H04N 9/04

Claims (1)

(57) [Claims] 1. A luminance signal including a horizontal synchronizing signal and a chroma signal which is modulated by a chrominance subcarrier and includes a color burst signal and a color data signal in time series.
In a black-and-white video signal output device used in a color video camera that outputs a composite color video signal of the NTSC system by combining with an addition means, a chroma signal provided in a preceding stage of the addition means is provided to the addition means.
The ON position and the chroma signal that are allowed to be supplied are added
Between the off position, which prohibits supply to the means.
Switchable switching means and a horizontal synchronizing signal which is provided in a stage preceding the adding means and is included in the luminance signal.
Control pulse that generates a control pulse of a fixed width in response to the
And the control pulse is invalidated when the color mode is set.
The switching means is kept at the ON position and the
Output the composite color video signal from the
Sometimes the control pulse is input to the switching means,
The switching means is turned off only for a certain period corresponding to the certain width.
Switch to the off position during the other period.
To separate the color burst signal from the chroma signal
To the adding means, and from the adding means to a luminance signal.
Output a black and white video signal to which a color burst signal is added
And a control means .