JPS61128693A - Color camera - Google Patents

Abstract

PURPOSE:To make a complete white balance adjustment even under an illumination of various types of fluorescent lights by two types of color and temperature informations with respect to a light source by employing the first, the second and the third photoelectric converters having spectral characteristics. CONSTITUTION:An image converted into an electric signal by a pickup device 1 enters a brightness signal processing circuit and a chromaticity signal processing circuit 3. In the circuit 3, the image is divided into an R, B signal and a narrow zone brightness signal YL, and the R, B signal enters respectively to gain control circuits 4, 5 and after a white balance adjustment, is deducted to the signal YL by deducting devices 6, 7 and two color difference signals of R-YL and B-YL are formed. A chromaticity signal modulated by a modulator 8 is added in an adding device together with a synchronous signal and a brightness signal to obtain an NTC signal. R, G, B components of lights in the vicinity of an object to be photographed are respectively detected by an R sensor 12, a G sensor 13, and a B sensor 14, and by division devices 15, 16, G/B and G/R signals are obtained and applied to the circuits 4, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to white balance adjustment in color cameras.

Conventional technology Conventionally, in color cameras that detect the light temperature of the light surrounding the subject and automatically adjust the white balance, the ratio of the red component to the growth component (R/B) of the light source is used as a means of automatic white balance adjustment. information) and used that information to control the gain of the chroma signal.

Problems to be Solved by the Invention However, since two gain control adjustments are made for the R and B signal channels of the chroma signal using only the R/B information of the light source, the point temperature characteristics of blackbody radiation may deviate from the point temperature characteristics. It has been difficult to achieve accurate white balance adjustment under other light sources, such as fluorescent lighting.

The present invention eliminates the drawbacks of the conventional example, and aims to perform highly accurate white balance adjustment even under a light source that deviates from the ideal color temperature characteristics of black body radiation.

Means for Solving the Problem In order to achieve the above object, the present invention solves the problem by reducing the G
/R, G/B information is detected respectively, and the gain amount of the R signal channel (hereinafter referred to as R-ch) and B signal channel (hereinafter referred to as B-ch) of the chroma signal is calculated based on the color temperature change of the surrounding light of the subject. Each is controlled independently.

Therefore, according to the present invention, since the R-ah and B-ch gain amounts are controlled by the G/R and G/B information, it is possible to control the gain amount of R-ah and B-ch by using the G/R and G/B information, so that it is possible to control the gain amount of R-ah and B-ch by using the G/R and G/B information. It also allows for highly accurate white balance adjustment.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. In FIG. 1, 1 is an imaging device.

2 is a luminance signal processing circuit, and 3 is a chroma signal processing circuit.

4 is the R-ch gain control circuit, 5 is the B-ch
A gain control circuit, 6 and 7 are subtracters, 8 is a modulator, 9 is a synchronization signal generation circuit, and 10 is an adder.

11 is an output terminal from which an NT8C signal output is obtained.

The above shows the configuration of a well-known NTSC color camera, and FIG. 1 is a block diagram thereof. 1
2 is an R sensor that detects the R signal component of the surrounding light of the subject; 1
3 is a G sensor that detects the G signal component, 14 is a B sensor that detects the B signal component, and 15.16 is a divider that logarithmically compresses and subtracts the information obtained from the sensors 12, 13, and 14. be.

Next, the operation of the above embodiment will be explained.

An image converted into an electrical signal by the imaging device 1 enters a luminance signal processing circuit 2 and a chroma signal processing circuit 3. Here, the chroma signal processing circuit 3 separates the R signal, the B signal, and the narrowband luminance signal (Yl, signal), among which the R9B signal is sent to the R-ch gain control circuit 4 and B, respectively.
-ch) Enters the y'in control circuit 5, and after white balance adjustment, the YL multiplied signal is subtracted by the subtracters 6 and 7, creating two color difference signals: R-Y signal, B-YL multiplied signal. It will be done. The chroma signal modulated by the modulator 8 is
It is added together with the synchronization signal and the luminance signal by an adder 10, and N
This becomes a TSC signal. Here, R-ch, B-ch gay/control circuit 4 for white balance,
Assume that the gain control characteristics of No. 5 are as shown in FIG.

On the other hand, the R component, G component, and B component of the surrounding light of the subject are detected by the R sensor 12. G sensor 13. The G/R signal and G/B signal are output from the dividers 15 and 14, respectively, and the output characteristics are as shown in Fig. 3 for the color temperature. Control circuit 4, 5
In addition, if the gain control of the R-ch and B-ch shown in FIG. 2 is performed, accurate white balance control can be performed.

Here, under a light source that does not match the point temperature characteristics of blackbody radiation, for example, under white fluorescent lamp illumination, the characteristics needed to achieve white balance are points A and B in FIG. R, /B
Although it is impossible to perform complete white balance control using information alone,
In the information system, divider 15.1 under white fluorescent lamp illumination
It is possible to select the output of 6 as point C2D in Fig. 3,
Highly accurate white balance adjustment can be achieved even under light sources that deviate from the color temperature characteristics of black body radiation.

Note that the sensors 12, 13, and 14 can be constructed of filters that pass blue, green, and red light, respectively, and photodiodes.

Effects of the Invention The present invention has the above-mentioned configuration and has different spectral characteristics. Since the second and third photoelectric converters are used to detect two types of color temperature information for the light source, it has the advantage that sufficient white balance adjustment is possible even under various types of fluorescent lighting. 0

[Brief Description of the Drawings] Fig. 1 is a block diagram of a color camera according to an embodiment of the present invention, Fig. 2 shows the gain control characteristics of R-ch and B-ch for white balance adjustment, and Fig. 2 shows the gain control characteristics of R-ch and B-ch for white balance adjustment. Figure 3 shows the output characteristics of the divider.0 1...imaging device, 2...luminance signal processing circuit, 3...
・Chroma signal processing circuit, 4...R-ch gain control circuit, 5...B-ch gain control circuit,
6.7...Subtractor, 8...Modulator, 9...Synchronization signal generation circuit, 10...Adder, 11...Output terminal, 1
2...R sensor, 13...G sensor, 14...B
Sensor, 15°16...Divider. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (2)

[Claims] (1) first, second, and third photoelectric converters that convert the light of the subject into electrical signals and pass different specific colors, respectively;
A compressor that comparatively compresses the outputs of the first and second and first and third photoelectric converters, and a color filter provided with a gain control circuit that receives the chroma signal processing output as an input and uses the output of the compressor as a gain control input. camera. (2) The color camera according to claim 1, wherein the compression characteristics of the compressor are approximated to the characteristics of the gain control circuit.