JPH0444491A - White balance device for video camera - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a white balance device for a color video camera.

[Conventional technology]

The third section is a block circuit diagram of a conventional color video camera shown in, for example, Japanese Utility Model Publication No. 41-16011, and in the figure, tl) is a lens.

(2) is the image sensor, (3) is the color separation circuit, (4) is the R channel gain control circuit, (5) is the R channel gain control circuit, (6) is the process circuit, and (7) is the matrix circuit. , (8) is the encoder circuit, (10) is the output terminal,
(21) is the R sensor (a photoelectric conversion element mainly sensitive to red), +22) is the G sensor (a photoelectric conversion element mainly sensitive to green), and (23) is the B sensor (mainly sensitive to blue). Photoelectric conversion element 1. (24), (251 is a division circuit.

Next, the operation will be explained. A light image incident from the lens (1) is photoelectrically converted by the image sensor (2), and is color-separated into three color signals of R, G, and B by a color separation circuit 13).

On the other hand, the R sensor (2I), the G sensor C22), and the B sensor (23) generate outputs proportional to the R component, G component, and B component of the incident light. Now, let each output value be Rs,
When Gs and Bs are given, the ratio between the G component and the R component which does not depend on the amount of incident light from the division circuit (24) am/Rs
(=v*) is output, and the ratio B of the B component to the G component, /aII (=va), is output from the division circuit (25).

The gain control circuit (4) is configured such that its gain increases as the control voltage VR increases, and the gain of the other gain control circuit (5) decreases as the control voltage V8 increases. , gain control circuit (
4) controls the gain of the R signal, and the gain control circuit (5)
The white balance is adjusted by controlling the gain of the B signal.

That is, in the case of a light source with a low color temperature, that is, a light source with more R component than G component and less B component, the control voltage V is lower than in the case of a light source with high color temperature. , v becomes a low value, the gain of the R channel gain control circuit (4) becomes small, and the gain of the B channel gain control circuit (5) becomes large. In the case of a light source with less R component and more B component,
The gain of the R channel gain control circuit (4) increases, and the gain of the B channel gain control circuit (5) decreases.

In this way, the gain of the R channel gain control circuit (4) and the gain of the B channel gain control circuit (5) are automatically controlled in response to changes in the R component, G component, and 7B components included in the light source. Therefore, the white balance can be automatically adjusted.

[Problems to be Solved by the Invention] Since the conventional color video camera is configured as described above, 1. For example, when a light source is directly incident on the R, G, B sensor and there is backlight, the color temperature of the sensor section and the subject are different. There was a problem that white subjects were colored blue due to the difference in color temperature.

This invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a color video camera with less deviation in white balance adjustment during backlighting.

[Means to solve the problem]

The color video camera according to the present invention has two outputs G, /Rs =Va of the first and second division circuits.

A closed area including the color temperature locus axis of the light source is set on a two-dimensional plane expressed by Bs /as = v, and the color of the light source is determined by the detected output of the first division circuit and the output of the second division circuit. If the temperature coordinates are within the closed region,
A coordinate conversion means is provided for converting the color temperature to the one with a higher color temperature, and two outputs of the converted coordinates V are o and V. It is characterized in that it is configured to perform white balance adjustment by.

[Effect]

In the coordinate conversion means according to the present invention, the output of the first division circuit and the output of the second division circuit are converted to the one having a higher color temperature by the coordinate converter when backlighting occurs.

[Example〕 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block circuit diagram of this embodiment, and the same parts as in FIG. 3 are given the same reference numerals, and their explanation will be omitted.

In the figure, (30) is a coordinate converter.

Next, the operation will be explained.

Figure 2 shows a two-dimensional plane represented by v8 and V6. It shows the area where the

Straight line connecting points A and B in the diagram! The trajectory indicated by v s = v * approximately matches the color temperature trajectory of an incandescent bulb or sunlight, and the color temperature of the incandescent bulb and the light source of sunny sunlight are directly on 1iAB.

In such a coordinate system, R, G when backlit.

When light directly enters each of the B sensors (21) to (23) from a light source, the coordinates of V@ and V- exist within the closed area. This coordinate G is shown as a point G in FIG.

At this time, since the color temperature of the subject is generally higher than the color temperature sensed by the sensor, the white balance shifts toward the front.

The coordinate converter (30) converts the coordinate G into the coordinate G0 according to the calculation formula below, and the converted bee mark value Via. , Vl
lG. is output as a control signal. The coordinates of G are (V,.

, Vaa) Go coordinates (V 1lan , V *
** ).

V *** = V na-βd vllc, o=vlIG+βd However, β>O, d=V*a (Vma Q).

The coordinate G0 is a coordinate converted to a color temperature higher than the coordinate G.

In the above embodiment, the closed area is shown as an area surrounded by six straight lines, but the shape of the closed area may be a rectangle, a parallelogram, a circle, an ellipse, or the like.

Also, the coordinate converter is a microcomputer.

It may be a digital circuit, an analog circuit using a clip circuit, or the like.

Furthermore, backlight correction output V*@. The TVIGO may be used to perform backlight correction such as iris correction.

[Effects of the Invention] As described below, according to the present invention, the ratio of the color components of the light source detected by the R, G, and B sensors R, /R, = V true, R6/R
, = V, it is determined whether the light source is backlit or not. If it is backlit, the values of the detected -Vm and Vm are corrected so that the color temperature becomes higher, and the correction value is used. Since the present invention is configured to correct the white balance, it is possible to obtain a white balance correction device that can reduce significant deviations in white balance during backlighting.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram of an embodiment of the present invention, Fig. 2 is a diagram for explaining the color temperature correction operation of this embodiment, and Fig. 3 is a block diagram of a white balance correction system of a conventional color video camera. It is a circuit diagram. (2) - Image sensor, (3) - Color separation circuit, (4), (E
ll-gain control circuit, (211-R sensor, +221-
G sensor, +231-B sensor, (24), (25
)--divider, (30)--coordinate converter. In each figure, the same reference numerals indicate the same or equivalent parts. Figure 2 VB=VR

Claims (1)

[Claims] (1) Red, green, and blue components of light source light R_S, G_S, B_
S is detected by R, G, and B sensors, respectively, and V_
The white color is configured to adjust the levels of the red and blue components of the red, green, and blue components of which the imaging signal is separated based on the values of R=R_S/G_S and V_B=G_S/B_S to achieve white balance. In the balance device, when the coordinates determined by the calculated values of V_R and V_B in a two-dimensional coordinate system having the vertical and horizontal axes of V_R and V_B are within a region including a predetermined portion of V_R=V_B,
It is characterized by comprising a coordinate conversion means for correcting the values of V_R and V_B in the direction of increasing color temperature, and adjusting the levels of the separated red and blue video signals based on the correction values. A white balance device for video cameras.