JP2004120456A - Color television camera device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that although a chroma components of a color television camera device is a signal required and indispensable for color reproduction, from the viewpoint of S/N characteristic, noise components will be increased, especially when S/N characteristic is bad, the chroma components are outputted as a colored black to a video signal when photographing a dark part of an object of low luminance. <P>SOLUTION: A color television camera device comprises an image pickup means for converting light from an object into a video signal, a video signal processing part for processing the video signal of the image pickup means, a means for generating a luminance signal and a color signal from the video signal processed by the video signal processor, and a luminance signal level discrimination section for discriminating a level of the luminance signal. The device is configured so that a gain of the color signal is controlled based on the output of the luminance signal level discrimination section. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color television camera device, and more particularly, to a color television camera device that controls a macro signal according to a luminance signal level.
[0002]
[Prior art]
The color television camera device processes each of the R (red), G (green), and B (blue) color signals from the imaging element portion, after performing signal processing such as gamma correction and contour enhancement processing, and then converts the R, G, and B color signals. A component signal converted into a luminance component and a chroma component or a chroma component is modulated and multiplexed and output as a composite signal.
[0003]
FIG. 2 is a block diagram showing the overall configuration of a conventional color television camera device. The light of each color of R, G, and B separated by the optical system prism 40 is input to the image pickup devices 21, 22, and 23, where it is converted into electrical signals of R, G, and B signals. The R signal, G signal, and B signal are amplified by signal amplifiers 24, 25, and 26, and then converted into digital signals by analog-to-digital converters 27, 28, and 29, respectively. Various signal processing such as enhancement processing is performed, and a luminance signal Y and color difference signals RY and BY are generated from the R, G, and B signals in the matrix circuit 31.
Of the color difference signals, the RY component is compressed to 1 / 1.14 times, and the BY component is compressed to 1 / 2.03 times, band-limited by LPFs 34 and 35, respectively, and then modulated by the modulation circuit 36. Then, a chrominance signal is generated, multiplexed with a luminance signal by a multiplexing circuit 37, and output to an output terminal 39 as a VBS signal. The output terminal 38 outputs a Y signal, an RY signal, and a BY signal separately. When the matrix circuit 31 generates the luminance signal Y from the R, G, and B signals, for example, in the NTSC system,
Y = 0.30 × R + 0.59 × G + 0.11 × B (1)
Obtains a luminance signal Y. The color difference signal can be easily obtained by RY and BY.
[0004]
One of the characteristics of the color television camera device is a signal-to-noise (hereinafter, referred to as S / N) characteristic. Before the matrix circuit 31, a noise removing circuit (not shown) for removing a noise component from the RGB signal. Z) is incorporated. It is known that the noise component is visually more visible in a low-luminance area that is a dark part than in a high-luminance area that is a bright part.
[0005]
[Problems to be solved by the invention]
Comparing the S / N characteristics of the color television camera device, it is better to evaluate only the luminance signal than to the VBS signal. This is because a chroma component in a color television camera signal is an indispensable signal for color reproduction, but increases a noise component from the viewpoint of S / N characteristics. In particular, when the S / N characteristic is poor, there is a problem that when a dark portion (black component) of a low-luminance subject is photographed, it is output as a slightly tinted black to a video signal.
[0006]
It is an object of the present invention to provide a color television camera device in which a video signal output is improved by nonlinearly controlling a chroma signal according to a luminance signal level.
[0007]
Another object of the present invention is to provide a color television camera device which divides a luminance region from a luminance signal and gives a gain process according to the luminance region to a chroma component to improve a signal-to-noise characteristic. is there.
[0008]
Still another object of the present invention is to provide a color television camera device which improves a signal-to-noise characteristic by determining a low-luminance region from a luminance signal and attenuating a chroma signal in a low-luminance portion. is there.
[0009]
[Means for Solving the Problems]
The color television camera device according to the present invention includes an imaging unit that converts light from a subject into a video signal, a video signal processing unit that processes a video signal from the imaging unit, and an image that is processed by the video signal processing unit. Means for generating a luminance signal and a chrominance signal from a signal; and a luminance signal level determining unit for determining a level of the luminance signal, wherein a gain of the color signal is controlled based on an output of the luminance signal level determining unit. Is configured.
[0010]
In the color television camera device of the present invention, the luminance signal is divided into a low luminance region and a high luminance region, and the gain of the color signal is controlled based on gain coefficients corresponding to the low luminance region and the high luminance region. Be composed.
[0011]
In the color television camera device according to the present invention, a low-luminance region is determined from the luminance signal, and the gain coefficient is reduced in the low-luminance region.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing the overall configuration of one embodiment of the present invention. In FIG. 1, the light of each color of R, G, and B separated by the optical system prism 20 is input to the imaging devices 1, 2, and 3, where it is converted into electrical signals of R, G, and B signals. You. The R signal, the G signal, and the B signal are amplified by the signal amplifiers 4, 5, and 6, respectively, and then converted into digital signals by the analog-to-digital converters 7, 8, and 9, respectively. Various signal processing such as enhancement processing is performed, and a luminance signal Y and color difference signals RY and BY are generated from the R, G, and B signals in the matrix circuit 11.
[0013]
In the gain processing circuit 13 (to be described in detail later), of the gain adjustment and color difference signals, the RY component is compressed to 1 / 1.14 times and the BY component is compressed to 1 / 2.03 times. After being band-limited by LPFs (low-pass filters) 14 and 15, the data is modulated by a modulation circuit 16 to generate a chroma signal, multiplexed with a luminance signal Y by a multiplexing circuit 17, and output to an output terminal 19 as a VBS signal. You. The output terminal 18 outputs a Y signal, an RY signal, and a BY signal separately. When the matrix circuit 11 generates the luminance signal Y, the color difference signal RY signal, and the BY signal from the R, G, and B signals, for example, in the NTSC system, the calculation can be performed by the above equation (1).
[0014]
The luminance signal Y output from the matrix circuit 11 outputs a gain signal corresponding to the luminance level in the level determination circuit 12 and applies it to the gain processing circuit 13. The chrominance signal is subjected to predetermined compression processing separately from the RY component and the BY component in the gain processing circuit 13, gain processing is performed using the gain coefficient obtained from the level determination circuit 12, and the LPFs 14 and 15 perform band limiting. The modulated signal is modulated by the modulation circuit 16 to become a chroma signal. The multiplexing circuit 17 multiplexes the luminance signal Y and the chroma signal and outputs the multiplexed signal to the output terminal 19 as a VBS signal. The output terminal 18 directly outputs the luminance signal Y and the color difference signal from the gain processing circuit 13.
[0015]
Next, an embodiment of a specific configuration of the gain processing circuit 13 shown in FIG. 1 will be described with reference to FIG. For example, in the case of the NTSC system, the RY component of the color difference signal is compressed to 1 / 1.14 times and the BY component to 1 / 2.03 times in the compression circuit 33 as described in FIG. Was explained.
[0016]
Accordingly, the gain processing circuit 13 receives the gain control signal from the level determination circuit 12 in addition to the above-described compression coefficient. That is, the gain control signal (gain coefficient) from the level determination circuit 12 is applied to the terminal 61 in FIG. The RY signal and the BY signal are applied to the terminals 62 and 63, respectively. The RY signal applied to the terminal 62 is multiplied by a multiplier 66 by a compression coefficient 1 / 1.14 from the RY signal compression coefficient unit 64 and a gain coefficient relating to the luminance signal level applied to the terminal 61. The multiplied coefficient is multiplied by a multiplier 68, gain controlled, and output from an output terminal 70 as a Cr signal.
[0017]
Similarly, the BY signal applied to the terminal 63 is multiplied by a compression coefficient 1 / 2.03 from the BY signal compression coefficient unit 65 and a gain coefficient related to the luminance signal level applied to the terminal 61. The multiplied coefficient is multiplied by a multiplier 69, gain controlled, and output from an output terminal 71 as a Cb signal.
[0018]
Accordingly, the Cr and Cb signals obtained at the terminals 70 and 71 are compressed by coefficients 1 / 1.14 and 1 / 2.03, respectively, and the control coefficient corresponding to the luminance signal level from the level determination circuit 12 is It is output as an added signal.
[0019]
Next, an embodiment of a specific configuration of the level determination circuit 12 in FIG. 1 will be described with reference to FIG. The luminance signal Y input from the matrix circuit 11 to the input terminal 75 is configured such that a gain coefficient corresponding to the signal level of the luminance signal Y is output to the terminal 77 by the ROM circuit 76. That is, the ROM circuit 76 generates the gain coefficient of the chroma signal from the read-only memory 76 (hereinafter referred to as ROM) using the information of the luminance signal Y as an address, and outputs the gain control signal (gain coefficient) to the output terminal 77. You. The ROM circuit 76 can realize various gain characteristics by preparing a data table. For example, if the main purpose is to improve the S / N characteristics, the gain coefficient in the low-luminance area is reduced, and as the luminance increases, the compression coefficient of the normal color difference component becomes 1 / 1.14. You just have to prepare. If color component information is desired even at the expense of the S / N characteristics, the data table of the ROM may be set so as to increase the gain coefficient at low luminance.
[0020]
In the case of a color television camera device, matrix processing is performed on the R, G, and B signals after gamma processing. Therefore, if a characteristic close to the inverse gamma characteristic is given to the chroma component, the S / N characteristic is improved. . Since there is little color information in the low-brightness region, compressing the low-brightness-side chroma component has little effect on the color reproduction of the image quality, so there is no particular problem.
[0021]
Next, a second embodiment of the present invention will be described with reference to FIG. 3, the optical system prism 20, the image sensors 1, 2, 3, the amplifiers 4, 5, 6, the A / D converters 7, 8, 9 and the process circuit 10 shown in FIG. 1 are the same as those in FIG. Therefore, they are omitted in FIG. Therefore, the output terminals of the process circuit 10 correspond to the input terminals 41, 42, and 43 shown in FIG. 3, and the R, G, and B signals after various signal processing are input to the matrix circuit 44.
[0022]
When considering the circuit of an actual product design, the gain processing circuit portion of FIG. 1 is the same as a conventionally used gain processing circuit, but this circuit has an extremely large circuit scale. Therefore, in the gain processing of the chroma signal, the circuit scale is smaller and the design efficiency is higher when the chroma signal is installed as close to the output terminal as possible.
[0023]
Therefore, in FIG. 3, the RY signal and the BY signal output from the matrix circuit 44 are compressed by the compression circuit 46, modulated by the modulation circuit 49 via the LPFs 47 and 48, and thereafter, 51 is applied. In the compression circuit 46, as described above, the RY signal is compressed to 1 / 1.14 times and the BY signal is compressed to 1 / 2.03 times.
[0024]
On the other hand, the level of the luminance signal output from the matrix circuit 44 is determined by the level determiner 45 and applied to the gain processing circuit 51 via the rate converter 55. The rate converter 55 is for adjusting the phase relationship and timing of the luminance signal to the phase relationship and timing of the chroma signal applied to the gain processing circuit 51.
[0025]
The gain processing circuit 51 adjusts the gain of the chroma signal from the modulation circuit 49 according to the luminance signal level from the level determination circuit 45, multiplexes the luminance signal with the luminance signal in the multiplexing circuit 52, and outputs a color television signal from the output terminal 54. Is done.
[0026]
When the luminance signal and the chrominance signal are individually output, they may be obtained from the output terminal 53 as individual signals via the gain processing circuit 50, respectively. The gain coefficient from the level determination circuit 45 is applied to the gain processing circuit 50. Although the output terminal 53 is described as a single terminal for convenience, it is configured so that a luminance signal and a color difference signal are individually obtained.
[0027]
As described above, the present invention has been described in detail. However, the present invention is not limited to the embodiment of the color television camera device described herein. It is needless to say that the present invention can be widely applied to a television apparatus or the like for reproducing a color image by using a digital camera.
[0028]
【The invention's effect】
As described above, according to the present invention, a color television image having excellent S / N characteristics can be reproduced in both the low-luminance region and the high-luminance region, and a video signal having desired chroma characteristics is output. The color television apparatus can be realized, and the effect is extremely large.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of a color television camera device of the present invention.
FIG. 2 is a block diagram illustrating an example of a conventional color television camera device.
FIG. 3 is a block diagram showing another embodiment of the present invention.
FIG. 4 is a block diagram showing an embodiment of a gain processing circuit used in the present invention.
FIG. 5 is a block diagram showing one embodiment of a level determination circuit used in the present invention.
[Explanation of symbols]
1, 2, 3: image sensor, 4, 5, 6: amplifier, 7, 8, 9: analog-digital converter, 10: signal processing circuit, 11: matrix circuit, 12: level determination circuit, 13: gain processing Circuits, 14 and 15: LPF, 16: modulation circuit, 17: multiplex circuit, 18, 19: output terminal, 41, 42, 43: input terminal, 44: matrix circuit, 45: level determination circuit, 47, 48: LPF , 49: modulation circuit, 50, 51: gain processing circuit, 52: multiplex circuit, 55: rate conversion section, 53, 54: output terminal, 61, 62, 63: input terminal, 64: RY compression coefficient unit, 65: BY compression coefficient unit, 66, 67, 68, 69: multiplier, 70, 71: output terminal, 75: input terminal, 76: memory, 77: output terminal.

Claims (3)

An imaging unit that converts light from a subject into a video signal, a video signal processing unit that processes the video signal from the imaging unit, and generates a luminance signal and a color signal from the video signal processed by the video signal processing unit Means, a luminance signal level determining unit for determining a level of the luminance signal, and a gain of the color signal based on an output of the luminance signal level determining unit. 2. The color television camera device according to claim 1, wherein the luminance signal is divided into a low luminance region and a high luminance region, and a gain of the color signal is controlled based on gain coefficients corresponding to the low luminance region and the high luminance region. A color television camera device. 3. The color television camera device according to claim 2, wherein a low luminance region is determined from said luminance signal, and said gain coefficient is reduced in said low luminance region.

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