JPH04893A - White balance adjustment circuit - Google Patents

Abstract

PURPOSE:To make stable malfunction-free white balance adjustment with a white balance adjustment circuit having a simple constitution by performing the second control after prescribed time set by a timer means. CONSTITUTION:A push switch 11 for starting is provided and a starting signal from this switch 11 is supplied to a microcomputer 10 through an OR circuit 12. The starting signal is also supplied to a timer means 13 and a signal taken out of the means 13 is supplied to the microcomputer 10 through the circuit 12 after prescribed time T. At the microcomputer 10, therefore, the first gain control is performed to amplifiers 4R and 4B upon receiving the starting signal and second gain control is performed to the amplifiers 4R and 4B upon receiving the signal from the timer means 13. During the period between the first and second control, the detecting signal of a detector is converged so that malfunction-free stable adjustment can be performed with a simple configuration.

Description

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

[Summary of the invention]

The present invention relates to a white balance adjustment circuit, and performs a second gain control after a predetermined period of time after the first gain control, thereby making it possible to perform good white balance adjustment with a simple configuration. It is something.

[Conventional technology]

For example, various circuits for adjusting the white balance in consumer color video cameras have been proposed (Japanese Patent Application Laid-Open No. 1983-1999-1).
(See Figure 1 of Publication No. 4993).

[Problem to be solved by the invention]

By the way, in such a white balance adjustment circuit, it is being considered to perform digital processing to form a control signal for adjustment using, for example, a microcomputer (μmC0N).

That is, FIG. 3 shows the configuration for this purpose, in which the three primary color signals R, G, and B from the signal processing circuit (31) in the previous stage are sent to amplifiers (32R), (32G), and (32B), respectively.
The signal is supplied to the subsequent signal processing circuit (33) through the signal processing circuit (33). Along with that, amplifier (32R), (32G), (
The signals from 32B) are detected by the detectors (34R),
(34G) and (34B), and the level of each signal is detected and sent to an A/D converter (35R).

(35G) and (35B), and the converted digital values are sent to the control microcomputer (35G) and (35B).
μmC0N) (36). Then, the value formed by 20 μ - 000 N (36) is sent to the D/A converter (37
R) (37B), and the converted analog signals are supplied to gain control terminals of amplifiers (32R) (32B).

As a result, for example, when the μmCON (36) is started while photographing a white subject, the ratio of the color signal of the video signal is detected by the μmCON (36), and this ratio is set in a predetermined relationship. A control signal is formed and supplied to the amplifiers (32R) (32B) to adjust the white balance.

However, in this circuit, the detector (34R) (3
4G) (34B) is usually provided with a time constant of several tens of vertical periods in order to eliminate the influence of noise and the like. For this reason μ
Even if a control signal was output from m CON (36), the detection signals of the detectors (34R) (34G) (34B) did not respond immediately, and this delay could cause malfunctions such as excessive control. .

Conventionally, the detectors (34R) (34G) (34B) are reset using the vertical synchronization signal from the signal processing circuit (31) to prevent malfunctions due to delays. It is necessary to prepare a special detector with this function, which makes the configuration complicated and requires 1
This causes problems such as a longer convergence time because the detection level becomes smaller.

This application was made in view of these points, and is intended to enable good white balance adjustment with a simple configuration.

[Means to solve the problem]

The present invention has a plurality of amplifiers (4R) (4G) (4B) through which a plurality of color signals are passed, and detects the level of the signal from these amplifiers (detector (7R)).
) (7G) (7B) ) In the white balance adjustment circuit, the gain control of the amplifier is performed (microcomputer (10)) so that these levels become equal, and an activation switch (11) is provided. , the signal from this starting switch performs the first gain control of the amplifier, and the signal from the starting switch starts the timer means (13) for a predetermined time, and the signal from this timer means controls the gain of the amplifier for the second time. This white balance adjustment circuit is characterized in that the gain of the amplifier is controlled.

[Effect]

According to this, since the second control is performed after a predetermined time set by the timer means, the detection signal of the detector is converged during this time, and stable adjustment without malfunction can be performed with a simple configuration. I can do it.

〔Example〕

In Figure 1, (1) is a lens system, and image light from a subject (not shown) is collected by this lens system (1) and supplied to a solid-state color image sensor (CCD) (2). .

The signal from this CCD (2) is transmitted to the previous stage signal processing circuit (
3) to form three primary color signals R, G, and B, and these three primary color signals R, G, and B are respectively supplied to an amplifier (4R) (
4G) (4B) to the subsequent signal processing circuit (5). The signal processing circuit (5) then performs the formation of the luminance signal Y and the two-color difference signals R-Y, B-Y, T correction, and encoding, thereby forming a standard composite color video signal. This formed video signal is sent to the output terminal (
6).

At the same time, the above-mentioned amplifier (4R) (4G) (4B
) from the detector (7R) (to 7) (
A/D converter (8R) (8G) (8
B), and the respective converted digital values are supplied to a control microcomputer (μmCON) (10). The value formed by this μmCON (10) is then supplied to the D/A converter (9R) (9B),
Each converted analog signal is sent to an amplifier (4R) (
4B), and the white balance is adjusted.

Further, in this circuit, a bush switch (11) for starting is provided, and a starting signal from this switch (11) is passed through an OR circuit (12) to μmc.

N (10). At the same time, switch (11
) is supplied to the timer means (13) as shown in FIG. 2A, and after a predetermined time T as shown in FIG. 2B, a signal as shown in FIG. is taken out, and this signal is passed through the OR circuit (12) to μ
mCON (10).

As a result, in μ-CON (10), switch (1
1) The first amplifier (4R) (4B
) gain control is performed and the timer means (13)
The second amplifier (4R) (4B)
gain control is performed.

In this case, the above-mentioned predetermined time T is
) (7G) By setting the time enough for the signal to converge in (7B), the second gain control can accurately detect and process the adjusted signal in amplifier (4E) (4B). Therefore, the residual components can be accurately readjusted by the first adjustment.

Therefore, in this circuit, the detector (7R) (7G)
(7B) does not require any special reset means, and the circuit can be realized using a simple integrator or the like.

In this way, according to the above-mentioned circuit, the second control is performed after a predetermined time set by the timer means, so the detection signal of the detector is converged during this period, and stable adjustment without malfunction is performed with a simple configuration. It is something that can be done like this.

Note that in the above-described circuit, the signals used for adjustment may be based on a luminance signal and yellow and cyan color signals.

Furthermore, in the above-mentioned circuit, the timer means (11) may be processed by, for example, a built-in software counter, without providing an actual circuit.

As a result, according to the above-mentioned circuit, even when the process of adjusting the white balance of a video signal is performed by digital processing, for example, it can be realized extremely well.

〔Effect of the invention〕

According to this invention, since the second control is performed after a predetermined time set by the timer means, the detection signal of the detector is converged during this time, so that stable adjustment without malfunction can be performed with a simple configuration. Now you can.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an example of a white balance adjustment circuit according to the present invention, FIG. 2 is a time chart diagram for explaining the white balance adjustment circuit, and FIG. 3 is a diagram for explaining the prior art. (1) Harens system, (2) 4;t CCD, (3) (5
) is the signal processing circuit, (4R) (4G) (4B) is the amplifier, (6) is the output terminal, (8R) (8G) (8B)
is an A/D converter, (9R) (9B) is a D/A converter,
(10) is a microcomputer, (11) is a huff switch, (12) is an OR circuit, and (13) is a timer means.

Claims (1)

[Claims] It has a plurality of amplifiers through which a plurality of color signals are passed, and the levels of the signals from these amplifiers are detected and the gains of the amplifiers are controlled so that these levels are equalized. In the white balance adjustment circuit, a start switch is provided, and a signal from the start switch performs the first gain control of the amplifier, and a signal from the start switch starts a timer means for a predetermined time. and a second gain control of the amplifier is performed using the signal from the timer means.