JPS60254895A - Color camera - Google Patents

Abstract

PURPOSE:To improve the deterioration in color reproducibility during the lighting of a high color temperature light source by applying a chroma signal and a luminance signal with matrix by a gain control voltage which varies with the change of color temperature, and controlling continuously a correction quantity. CONSTITUTION:When the light source rises in color temperature, gain control quantities of R and B vary so as to make a white balance adjustment. Color difference signals B-YL and R-YL added to a signal YL and a luminance signal increase in quantities K1-K4 according to said variations and the signal YL applied to subtracters 7 and 8 is corrected to suppress the motion of vectors of each subject when the color temperature of the light source is high. Similarly, a luminance signal supplied to an adder 13 is corrected, so the balance ratio of a chroma quantity and a luminance level which is not represented with vectors is also corrected, thereby improving greatly the deterioration in color reproducibility in a high color temperature atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a color camera capable of white balance adjustment.

1. Construction of a conventional example and its problems FIG. 1 shows the construction of a conventional color camera having a color temperature detection device of a light source. The video signal converted into an electric signal by the image pickup tube 1 is amplified by a brilliance amplifier 2, and then enters a luminance signal processing circuit 3 and a chroma signal processing circuit 4. The luminance signal processing circuit 3 extracts a luminance component from the input video signal, and the chroma signal processing circuit extracts a narrow range luminance signal YL from the input video signal.
and R2B signals. The R signal and B signal are each R cane @ control circuit 5. Enter B gain fist control circuit 6. On the other hand, the color temperature information obtained by the color temperature sensor 10 is input as R and B gain control signals to the R and B gain control circuits 5.6 through the color temperature information-voltage conversion circuit 11 to perform gain control. By doing this, a white balance is achieved that corresponds to the color temperature of the light source illuminating the subject.

The gain-controlled R and B signals are sent to subtracter 7.
, 8 are subtracted between the YL multiplied signals to produce color difference signals R-YL signal and B-YL multiplied signal. R-YL multiplied signal B-YI,
The signal is modulated by the modulator 9, enters the adder 13 together with the synchronization signal generated by the synchronization signal generator 12, and the luminance signal Y from the luminance signal processing circuit 3, and is output from the output terminal 14 to the NTS
C output is obtained.

However, when the white balance is simply adjusted using the conventional method, there is no problem under a light source of 3200 c', which is the standard, but when shooting under a high color temperature, the color reproduction deteriorates significantly. To explain in detail using FIG. 2, when an object of red, yellow, green, cyan, blue, and magenta is imaged under illumination with a color temperature of 3200°, the tips of the vectors shown by dotted lines are 15°, 16°, 17°, 18°. Reproduced on 19.20,
Although good color reproduction characteristics are obtained, as the color temperature of the irradiation light source increases, the color reproduction position of each subject moves in the direction of the arrow. Furthermore, the amount of balance between the amount of chroma and the brightness level also changes, causing a problem in that color reproducibility is greatly degraded.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the above-mentioned conventional examples, and aims to improve the deterioration of color reproducibility in high color temperature light source illumination.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides gain control voltages for R and B signals that vary depending on the color temperature of the light source.
A circuit is provided that continuously varies the matrix amount of the chroma signal and the luminance signal.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 3, the same parts as in FIG. 1 are indicated by the same symbols. 21 is a matrix correction circuit for luminance signal Y;
2 is a matrix correction circuit for the narrow-range luminance signal YL, 23
is an inverter. Here, the operation of the matrix correction circuit 22 is expressed by a formula: YL'=YL-1(B-YL)+1c
2(R-Yl), to 1. k2≧0. In the above equation, YL is the output signal of the matrix correction circuit 22, and YL is the input signal. Then, in response to changes in color temperature, the constant values of 1 and 2 are controlled by a gain control signal output from the color temperature information/voltage conversion circuit 11.

The operation of the matrix correction circuit 21 is also expressed by the following equation. YH'-YH- to 3(B-Yl)+ to 4(R-Y2)
.

k3. 4≧O where YH is the matrix correction circuit 21
, and YH is the input signal.

3 to the constant. The value of 4 is controlled by a gain control signal output from the color temperature information/voltage conversion circuit 11.

Next, the operation of the above embodiment will be explained. When the color temperature of the light source increases, R and B cannot be used to maintain white balance.
The gain control amount changes. Depending on the amount of change, the color difference signal (B-YL
) signal and (R-YL) signal (k1 to 4) are increased and the YL-fold signal applied to subtracters 7 and 8 is corrected, resulting in the vector movement of each subject when using a high color temperature light source as shown in Figure 2. suppress. Similarly, since the luminance signal applied to the adder 13 is also corrected, the balance ratio between the amount of chroma and the luminance level, which is not expressed on the vector, is also corrected, which significantly reduces the deterioration of color reproducibility at high color temperatures. It can be improved.

Effects of the Invention The embodiments have been described above.According to the present invention, not only chroma correction but also brightness correction can be performed at the same time as the color temperature of the light source changes. It is possible to correct reproduction errors and realize a high-quality color camera.

In the above embodiment, the information for performing matrix control is obtained from the color temperature sensor, but if it is a color camera that captures a white image with a camera and takes white balance, the gain of R or B may be used. - The above information may be obtained from the control voltage.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a color camera having a conventional color temperature sensor, FIG. 2 is a vector diagram showing its color reproducibility, and FIG. 3 is a block diagram of a color camera according to an embodiment of the present invention. 21.22...Matrix correction circuit.

Claims (1)

[Claims] A color camera comprising a means for multiplying a chroma signal and a luminance signal by a matrix using a gain control voltage that changes in response to changes in color temperature, and continuously controlling the amount of correction thereof.