JPS60253935A - Color camera - Google Patents

Abstract

PURPOSE:To obtain a natural video output which gives no feeling of physical disorder by clipping the information output of an external light sensor to high or low color temperature according to photographic conditions. CONSTITUTION:The video signal of an image pickup device 1 is inputted to brightness and chroma signal processing circuits 2 and 3 and separated by the circuit 3 into a narrow-band luminance signal YL and an R and a B signal; and the R and B signals are supplied to gain control circuits 4 and 5 for white balance adjustment and inputted to substracters 6 and 7, which input color difference signals R-YL and B-YL to a modulator 8. The synchronizing signal of a generator 9 is added 10 to the wide-band luminance signal YH obtained by the circuit 2 and the chroma modulated signal of the modulator 8 to obtain an NTSC output. The color temperature information of the external sensor 12 is applied to the circuit 5 through high and low color temperature clipping circuits 13 and 14 and further applied to the circuit 4 through an inverting amplifier 15. Consequently, high color temperature clipping is performed under blue sky photographic conditions and low color temperature clipping is performed on sunset glow and candle light photographic conditions, thereby obtaining a natural video output which gives no feeling of physical disorder.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a color camera.

Conventional configurations and their problems Color cameras that use information from external light sensors to perform white balance may, for example, cause the blue sky to become white when photographing it, or the sky to be white at sunset. 1
It may not be possible to express the redness under a candle light source.

Object of the Invention The present invention eliminates the drawbacks of the above-mentioned conventional examples.Structure of the Invention The present invention clips the information output of an external light sensor to a high color temperature under blue sky imaging conditions, and improves the image quality during sunset and candlelight imaging. Under certain conditions, low color temperature clipping is performed to obtain natural video output without any discomfort.

Description of examples An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, 1 is an imaging device, 2 is a luminance signal processing circuit, 3 is a chroma signal processing circuit, 4 is a gain control circuit for the R channel which is the first signal, and 6 is the B channel which is the second signal. gain control circuit,
6 and 7 are subtracters, 8 is a modulator, 9 is a synchronization signal generation circuit,
1o is an adder, and 11 is an output terminal. The configurations 1 to 11 above are well-known configurations of color cameras. 1
2 is an external light sensing sensor, which outputs a signal corresponding to the color temperature of the irradiated light. Reference numeral 13 denotes a high color temperature cryograph circuit, which clips the high color temperature region of the output signal of the external light sensing sensor 12. 14 is a low color temperature clipping circuit which similarly clips the low color temperature region. 16 is an inverting amplifier, 16
is an output terminal for corrected color temperature information. The operation of this embodiment will be explained below. The image converted into an electrical signal by the imaging device 1 is sent to a luminance signal processing circuit 2. It enters the cross signal processing circuit 3. The chroma signal processing circuit 3 separates the third signal into a narrowband luminance signal (YL), an R signal, and a B signal. The separated R and B signals are subjected to white balance adjustment by gain control circuits 4 and 5, and then input to subtracters 6 and 7, respectively, to produce two color difference signals (
R-YL, B-YL) 9 enters the modulator 8. A wideband luminance signal (Y
A synchronizing signal from a synchronizing signal generator 9 is added to a chroma modulation signal obtained by a modulator 8 and a chroma modulating signal by an adder 10, and an NTSC output is obtained at an output terminal 11. Here, the control signal of the gain control circuit 4.5 that performs white balance adjustment is used to convert color temperature information obtained from the external light sensor 12 to the high color temperature clipping circuit 13. The light passes through the low color temperature clipping circuit 14 and has the characteristics shown by the solid line in FIG. The characteristics indicated by the broken line here are those of the high color temperature clipping circuit 13.
This is the case without the low color temperature clipping circuit 14.

By applying the color temperature information shown in FIG. 2 to the R channel gain control circuit 4 through the B channel gain control circuit 5 and the inverting amplifier 15,
When capturing an image of a blue sky, the color temperature of the blue sky at 9,500° to 10,000° is not followed and is fixed at the outdoor color temperature (7,000°K), so the blue sky is not corrected to be white. On the other hand, when capturing an image at sunset or under a candle light source, the color temperature information is fixed at 2800':K, making it possible to realize an image close to the colors perceived by the human eye.

In the above embodiment, the high color temperature clipping circuit 13 and the low color temperature clipping circuit 14 are used together, but the present invention is not limited to the sauce, and it is also possible to select only one of them.

Furthermore, although we have described a color camera that uses YL and R2B as chroma signals, it is possible to implement this in any color camera that achieves white balance by controlling the gain amounts of two of the third primary colors of the color signal.

Effects of the Invention As is clear from the following explanation, according to the present invention, the white balance is not uniformly balanced under a blue sky, sunset, or under a candle light source, but the optimal white balance is determined according to the imaging scene. It has the advantages that can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color camera according to an embodiment of the present invention, and FIG. 2 is a diagram showing output characteristics after correction of color temperature information of an external light sensor. 9313...-
- High color temperature clip circuit, 14...Low color temperature clip circuit. Name of agent: Patent attorney Toshio Nakao (1 person, 1 illustration)

Claims (1)

[Claims] High color temperature region clip circuit for the output of the sensor for detecting external light,
A color camera that performs white balance adjustment as a control input of a color gain control circuit via at least one of the low color temperature region clipping circuits.