JPH1098744A - Color television camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a white blur and a hue variation phenomenon, etc., and obtain video which has a hue close to the hue of an original subject by detecting a high-luminance signal higher than an arbitrary video signal level and compressing respective RGB video signals of an area detected as the high- luminance signal with the same compressibility. SOLUTION: An NAM circuit 1 detects the high-luminance signal part from the respective R, G, and B video signals and an arbitrary DC level signal. Amplifiers 2 to 4 which amplify the respective R, G, and B video signals are varied in gain with the signal from the signal from the NAM circuit 1. The respective R, G, and B video signals which are changed into video signals by a video signal converting element and the arbitrary DC level signal for detecting the high-luminance video signal are inputted to the NAM circuit 1, which detects a video signal larger than the DC level signal. With the detection signal, the gains of the R, G< and B variable gain amplifiers 2 to 4 are controlled to compress the R, G, and B video signal levels with the same compressibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television camera.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG.
Generally, R, G, and B video signal processing of a color television camera that splits light into three primary colors of R, G, and B and converts the light into video signals by an image sensor will be described below. R, G,
The B video signals are supplied to variable gain amplifiers 2, 3, and 4 for R, G,
Each of the B video signal levels is set to the same level, gamma-corrected by gamma circuits 5, 6, and 7, and input to knee circuits 8, 9, and 10. The knee circuits 8, 9 and 10 compress and output an image signal portion of the input video signal which is 100% or more of the rated image signal level. Output image signals from the knee circuits 8, 9, and 10 are input to white clip circuits 11, 12, and 13 and are clipped at 110% of the rated image signal level, and output to subsequent stages (not shown). .

[0003]

In the above-mentioned prior art,
RGB beyond the knee point and white clip point
When processing is performed to compress a high-brightness video signal, there is no difference in RGB video signal levels due to compression processing by the knee and white clip circuits, and an image in which an overexposure phenomenon occurs occurs. Further, even if there is a slight difference between the R, G, and B video signal levels, a phenomenon in which the hue changes to a hue different from that of the actually captured subject appears. In general, in the case of a subject having a wide dynamic range of light quantity, there have been problems such as that the color of the sky looks white and that the hue of the flesh color of the part of the human face where the light hits changes.

It is an object of the present invention to reduce such overexposure and hue change, and to obtain an image closer to the original object hue.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention detects a high-luminance signal having an arbitrary video signal level or more, and detects each RG in an area detected as a high-luminance signal.
The B video signal is compressed at the same compression ratio.

As a result, in the prior art, even when a video signal of a high luminance level which is knee clipped and has the same hue as white is input, the R, G, and B video signal level ratios have the same compression ratio. Therefore, a color signal that does not change and does not change the hue is generated, and the overexposure phenomenon can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 is an R, G, B video signal and an arbitrary DC
NAM circuits 2, 3, and 4 for detecting a high luminance signal portion from the level signal are amplifiers for amplifying each of the R, G, and B video signals. The gain of the amplifier is varied by a signal from the NAM circuit 1. The R, G, and B video signals converted into video signals by an image signal conversion element (not shown) and an arbitrary DC level signal for detecting a high-luminance video signal are output from the NAM circuit 1.
And a video signal higher than the DC level signal is detected. The gains of the R, G, and B variable gain amplifiers 2, 3, and 4 are controlled by the detection signal, and the R, G, and B video signal levels are compressed at the same compression ratio.

[0008]

According to the present invention, overexposure and hue change are improved, and a subject having a wide dynamic range is reproduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of claim 1 of the present invention.

FIG. 2 is a waveform chart showing the effect of the present invention.

FIG. 3 is a block diagram showing the entire configuration of a conventional technique.

FIG. 4 is a waveform chart obtained by a conventional technique.

[Explanation of symbols]

1: NAM circuit, 2, 3, 4: variable gain amplifier,
5, 6, 7: gamma circuit, 8, 9, 10: knee circuit,
11, 12, 13: white clip circuits.

Claims (1)

[Claims] 1. A color television camera for performing video signal processing for each of R, G, and B channels for an RGB video signal converted by an image sensor, wherein the R, G, and B video signals and an arbitrary DC level A NAM circuit for detecting a high-brightness signal from the signal and a variable gain amplifier for each of R, G, and B video signals whose gain is controlled by the high-brightness signal detected by the NAM circuit. A high-luminance signal portion compressed for each of R, G, and B video signals at the same ratio.