JPH0263295A - White balance adjustment circuit - Google Patents

Abstract

PURPOSE:To reduce the converging time independently of the quantity of a difference from a present control voltage by reading a control voltage from a table in response to the ratio of plural color signals and supplying the control voltage to plural amplifiers. CONSTITUTION:The circuit consists of plural amplifiers 24R-24B through which plural color signals pass respectively, a ratio detection means 6 detecting the ratio of the plural color signals, and a table 7 on which a control voltage to plural amplifiers 24R-24B in response to the ratio of the plural color signals is written. When the ratio detected by a ratio detection means 8 is within a prescribed range, the control voltage read from the table 7 in response to the ratio is supplied to the plural amplifiers 24R-24B. Thus, the converging time is reduced independently of the quantity of the difference of the present control voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance adjustment circuit for a color video camera.

[Summary of the invention]

According to the present invention, when the ratio of the plurality of color signals is within a predetermined range, the plurality of amplifiers through which the plurality of color signals respectively pass,
By supplying the control voltage read out from the table according to the ratio, the convergence time of the control voltage can be shortened and malfunctions can be prevented.

[Conventional technology]

Conventionally, color video cameras require white balance adjustment in order to obtain high-quality color images (see Japanese Patent Laid-Open No. 56-4993). If the white balance deteriorates, when shooting a white subject,
Not only does the reproduced image become colored and not white, but also the color reproduction when photographing ordinary subjects deteriorates, making it impossible to obtain high-quality river images.

FIG. 3 is a block diagram of an example of a color video camera having a white balance adjustment circuit.

In the same figure, (21) is the imaging lens, (22) is the CC
D Color photography using solid-state image sensors @! It is element.

The output signal of the color image sensor (22) is sent to the signal processing circuit (2
3), and from this signal processing circuit (23), red,
At the edge, blue j Keikyu signals R, G, and B are output.

Primary color signal R1G output from the signal processing circuit (23),
B is the amplifier (24N) and (24G
).

It is supplied to the matrix circuit (25) via (24B). Here, the amplifier (241(), (24B)
constitutes a white balance adjustment amplifier, and its gain is controlled as described later.

From the matrix circuit (25), a luminance signal Y, a red difference signal RY, and a blue difference signal! 3-Y is output and supplied to the color encoder (26). The output terminal (27) derived from this color encoder (26) is
For example, an NTSC color image (SV) can be obtained.

Also, in this example of FIG. 3, the amplifier (2, f).

(24G), (24B), integral circuit (28
R), (28G).

(28B), comparator (29R), (29B)
, a gain control circuit (30) constitutes an image processing white balance adjustment circuit. That is, amplifier (24) 1), (24G), (24B
The primary color signals R, G, and B outputted from the respective integration circuits (28) 1).

It is supplied to (28G) and (28B') and is integrated by ζ. Integrating circuit (28M'), (28G
) are respectively supplied to a comparator (29R), and a comparison error signal output from this comparator (29R) is supplied to a gain control circuit (30). Integral circuit (2
The output signals of 8B) and (28G) are each supplied to a comparator (29B), and the comparison error signal output from the ratio 12 (29B) is supplied to a gain control circuit (30). The above-mentioned amplifier (24R), , (2
4B) is controlled by this gain control circuit (30). That is, comparator (29)1),
(29B) based on the output signal of the integrating circuit (28B).
The gain of the amplifier (24ft'), <2i) is controlled so that the primary color signals R, G, and B output from (24ft'), (28G), and (28B) are all equal.

[Problem to be solved by the invention]

By the way, in the white balance adjustment circuit in the example shown in FIG. 3, the color image sensor (22) is red.

When a normal image containing green and blue is captured, the average of the images is achromatic, so a good Why 1-balance adjustment is performed, but Color 11! When the image element (22) captures an image of a single color such as red, green, or blue, there is a problem in that even if the image is averaged, it does not become achromatic, and the image element (22) malfunctions to make the image white. Ta.

In addition, in the white balance adjustment circuit in the example in FIG. 3, since the convergence value of the control 1-roll voltage to the amplifiers (24R) and (24B) is not known in advance, the current control 1 call of the amplifiers (24R) and (2aa) is not known in advance. There is a disadvantage that the convergence time varies greatly depending on the magnitude of the difference between the voltage and the voltage.

Therefore, it is an object of the present invention to shorten the convergence time of the control voltage to the amplifier and to prevent malfunctions.

[Means to solve the problem]

This invention includes a plurality of amplifiers (24) 1) to (24B) through which a plurality of color signals pass, a ratio detection means (6) for detecting a ratio of a plurality of color signals, and a plurality of color signals (No. 4). It is equipped with a table (7) in which control voltages to a plurality of amplifiers (24R) to (24B) according to the ratio are recorded, and when the ratio detected by the ratio detection means (6) is within a predetermined range, this One control ball read out from the table (7) according to the detected ratio is connected to multiple amplifiers (2
4R) to (24B).

[Effect]

In the above configuration, the control voltage is read from the table (7) according to the ratio of the plurality of color signals, and this control voltage is supplied to the plurality of amplifiers (2i) to (24B), so that the current control voltage and Regardless of the size of the difference, the convergence time becomes rectangular.

In a normal color video camera, for example, white balance adjustment is performed by varying the gain of the red primary color (No. 6) and the blue primary color (No. 3), but the gain changes when the color temperature of the illumination light source changes. There is a correlation.

In the above configuration, white balance adjustment is performed only when the ratio of multiple color signals is within a predetermined range, so white balance adjustment is performed only when the color temperature of the illumination light source changes. When capturing a single-color image such as the above, the balance 'iJ~ is not adjusted and malfunctions are prevented.

(Embodiment) An embodiment of the present invention will be described below with reference to Fig. 1. In Fig. 1, parts corresponding to those in Fig. 3 are given the same reference numerals, and detailed explanation thereof will be omitted. .

In the same figure, primary colors No. 14 R, G, and B output from the signal processing circuit (23) are each input to an amplifier (IR).

(IG), <IB), connection switch (2R
), (2G).

The integral via (2B) is the path (3)1), (3G)
, (3B).

It is also output from the signal processing circuit (23)! #The primary color urgent signal G is supplied to the comparator (9) and compared with the reference voltage VRgr. Connection switch (2) 1) mentioned above.

(2G), (2B) are controlled by the output signal of the comparator (9), and when the green primary color signal G becomes larger than the reference voltage VREF, the connection switch (2)1),
(2G).

2B) is turned off, and turned on at other times.

The outputs d of the integrating circuits (3N), (3G), and (3B) are on the a side and b side of the changeover switch (4), respectively.
It is supplied to the fixed terminal on the side and C side. This selector switch (
4) are switched sequentially at predetermined time intervals, and from this changeover switch (4), the integration circuit (Su), (3G)
, (3B), time-division signals of primary color signals R, G, and B are output. The output signal of the changeover switch (4) is converted into a digital signal by an A/D converter (5) and then supplied to a microcomputer (hereinafter referred to as "microcomputer") (6). In this microcomputer (6),
Based on the output signal of the switch (4), the primary color signals R, G,
The ratio of B, for example, G/R and G/B is calculated.

(7) is a table made of, for example, a ROM.

In this table (7), the gain necessary to achieve white balance with R-G=8 is shown in the amplifier (24) 1).

(24B) to obtain each amplifier (24M
) (24B) is written in advance in relation to the ratio of the primary color signals R, G, H.

From this table (7), the above-mentioned microcontroller (6)
The amplifier (
24R) and (24B), the control voltages to be supplied are read out, respectively.

The control voltage thus read by the microcomputer (6) is converted into an analog signal by the D/A converter (8) and then supplied to the amplifiers (24R) and (24B).

By the way, in a device that achieves white balance by changing the gain of the red primary color signal R1 and the blue primary color signal B output from the signal processing circuit (23) by iJ, the red primary color when the color temperature of the illumination light source changes. There is a correlation between the gains of the signal R9 and the blue primary color decoding code B. For example, when the gain of the red primary color signal R is set to R gain and the gain of the blue primary color signal B is set to B gain, the graph in a state where white balance is achieved is as shown by the solid line a in FIG. 2. Therefore, R gain, B
Only when the gain is on the solid line a, therefore only when the j-Keikyu signals R, G, and B are at a predetermined ratio, read out the control voltage from the table (7) as described above and apply it to the amplifier (24M), (24B). ), and on the other hand, if the R gain and B gain are not on the solid line a, the previous control voltage can be maintained, and the white balance can be adjusted only when the color temperature of the illumination light source changes. will be done.

In this example, in consideration of some variations and the diversity of illumination light such as light bulbs and F & light lamps, a certain width is provided as shown with diagonal lines in Figure 2, and the R gain and B gain are set within this range. Only when the control voltage is within the range, the control voltage is read from the table (7), and this control voltage is applied to the amplifier (24).
R), (24B); on the other hand, when the R gain and B gain are not within this range, the amplifier (24R)
) and (24B), the previous control voltages are maintained.

In this example, the integration circuit (3M), (3G)
.

According to the ratio of the primary color signals R, G, and B output from (3B), from table (7), the amplifier (24R) and (24B) calculate the gain necessary to achieve white balance.
) to obtain each amplifier (2441),
(Since the control voltage to be supplied to 24B is read out and supplied to amplifiers (24R) and (24B), white balance adjustment can be performed satisfactorily.In this way, according to this example, from table (7), The necessary control voltage is read out and the amplifier (24N), (2
4B), the convergence time can be shortened regardless of the magnitude of the difference from the current control voltage.

Further, in this example, the control voltage is read out from the table (7) and white balance adjustment is performed only when the R gain and B gain are within the range shown by the diagonal lines in FIG. Therefore, according to this example, white balance adjustment is performed only when the color temperature of the illumination light source changes. For example, when capturing an image of a single color such as red, green, or blue, white balance adjustment is not performed. It is possible to prevent malfunctions such as turning a single color image into white.

In addition, in this example, the green primary color signal G is the reference voltage VRgF
When larger, connect switch (2 pin),
(2G) and (2B) are turned off. When the green primary color signal G becomes larger than the reference voltage VRICF, each pixel of the color image pickup element (22) is saturated, and the primary color signals R1G and H output from the signal processing circuit (23) have equivalent color information. It becomes something that does not exist. In this example, these primary color signals R, G, and B are transmitted through an integrating circuit (3R),
Since it is not supplied to (3G) and (3B), malfunctions can be prevented.

Although not mentioned above, in this example, (1o) is an external interface, (11) is a mode selection switch,
The mode selection switch (11) is the external interface (
10) to the microcomputer (6). and,
By operating the mode selection switch (11), you can select an automatic tracking mode that operates as described above, a fixed mode that fixes the control voltage, or a preset control voltage such as indoor, outdoor, SI light, etc. It can be changed to preset output modes, etc.

In the above embodiment, the signal processing circuit (23) outputs the primary color signals R, G, and B, but for example, the yellow signal Ya, the cyan signal cy, and the green primary color signal G are output from the signal processing circuit (23).
It can be similarly applied to things that are outputted.

〔Effect of the invention〕

According to this invention, a control voltage is read out from a table according to the ratio of a plurality of color signals, and this control voltage is supplied to a plurality of amplifiers, so that it takes a long time to converge regardless of the magnitude of the difference from the current control voltage. In addition, since white balance adjustment is performed only when the ratio of multiple color signals is within a predetermined range, for example, when forming an m-color b image into an I image, the white balance It is possible to prevent malfunctions from occurring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the same, and FIG. 3 is a block diagram of an example of a color video camera. (IR) ~ (1B) , (24R) ~ (24B
) is the amplifier, (2R) to (2B) are the connection switches,
(3R) to (3B) are integral circuits, (4) are changeover switches, (5) are Al1) converters, (6) are microcomputers, (7) are tables, (8) are D/A converters, (9
) is a comparator, (22) is a color image sensor, (23) is a signal processing circuit, (25) is a matrix circuit, and (26) is a color encoder.

Claims (1)

[Claims] A plurality of amplifiers through which a plurality of color signals pass, a ratio detection means for detecting a ratio of the plurality of color signals, and a ratio detecting means for detecting a ratio of the plurality of color signals to the plurality of amplifiers according to a ratio of the plurality of color signals. and a table in which control voltages are written, and when the ratio detected by the ratio detection means is within a predetermined range, the control voltage read from the table according to the detected ratio is supplied to the plurality of amplifiers. A white balance adjustment circuit characterized by: