JPH04170887A - White balance correction device - Google Patents

Abstract

PURPOSE:To appropriately correct a white balance in spite of the ratio of zoom by controlling the white balance based on output information from an image pickup element, detection information of a color temperature detection means and detection information of a zoom ratio detection means. CONSTITUTION:The color temperature detection means 6 detecting color temperature information on incident light from a subject, the zoom ratio detection means 12 detecting the ratio of the zoom of a zoom lens and a white balance control circuit 13 controlling the white balance based on output information from the image pickup element 1, detection information of the color temperature detection means 6 and detection information of the zoom ratio detection means 12 are provided. The white balance control circuit 13 changes the control signal of the white balance by zoom ratio information from a zoom encoder 12 and outputs it to amplifiers 3a and 3b for white balance control. Thus, the white balance can appropriately be corrected by a stable operation in spite of the ratio of the zoom.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance correction device for an imaging device such as a video camera equipped with a zoom lens.

[Conventional technology]

Conventionally, devices for correcting the white balance of video cameras and the like have either controlled the white balance based on information obtained from the image sensor itself, or controlled the white balance based on the color temperature information of the incident light from the subject. There is something that controls it. There is also known a correction device that combines the two and controls white balance using information from both.

FIG. 4 is a block diagram showing a schematic configuration of a conventional white balance correction device that combines both information from the image sensor and color temperature information. In the figure, reference numeral 1 denotes a CCD, which is a solid-state imaging device, in which imaging light from a subject is photoelectrically converted. 2 is R (red) from the output signal of CCD 1
, a color separation circuit that separates G (green) and B (*) color signals;
3a.

3b is a variable gain controllable white balance control amplifier (amplifier) that amplifies the R and B color signals output from the color separation circuit 2; 4 is a gain-controlled R and B color signal and color separation circuit 2; Input the G color signal from , and generate the luminance signal Y and color difference signal RY.

5 is a signal processing circuit that generates a standard television signal by inputting the luminance signal Y and color difference signals RY and B-Y; 6 is a color of incident light from the subject; A color temperature sensor detects temperature information, and 7 is a white balance control circuit that controls white balance based on the detection information of the color temperature sensor 6 and the output information from the CCD 1. Here, the color temperature information and the color difference signal R- The gains of the white balance control amplifiers 3a and 3b are controlled based on the information obtained by comparing Y and BY with the reference level.

In the apparatus configured as described above, the imaging light from the subject that enters the CCD 1 is photoelectrically converted, and then
The signal is input to the color separation circuit 2 and separated into color signals of the three primary colors R2O and B. Among these color signals, the R and B color signals are input to the signal processing circuit 4 via white balance control amplifiers 3a and 3b, and the G color signal is directly input to the signal processing circuit 4. The signal processing circuit 4 generates a luminance signal Y and color difference signals R-Y and B-Y, which are input to the signal processing circuit 5 at the subsequent stage.

On the other hand, the light from the subject also enters the color temperature sensor 6, where the color temperature information of the incident light is detected, and the color temperature information is input to the white balance control circuit 7. This white balance control circuit 7 also includes the signal processing circuit 4.
The color difference signals R-Y and B-Y are inputted. and,
The white balance control circuit 7 generates a control signal based on each input signal, and this control signal is supplied to the white balance control amplifiers 3a and 3b.

Thereby, the white balance is controlled to be optimal.

The luminance signal Y and the white balance-controlled color difference signals R-Y and B-Y are input to the signal processing circuit 5 as described above, where they are converted into standard television signals and then output to the outside. .

Next, the control operation of the above-mentioned white balance control circuit 7 will be explained in detail. FIG. 5 is a diagram showing the internal configuration of the control circuit 7. As shown in FIG. In the figure, 8 is a first gain control signal forming circuit that uniquely forms gain control signals (white balance correction signals) R1 and Bl of R and B signals according to color temperature information from the color temperature sensor 6. , 9 is the color difference signal R-Y
, B-Y and its achromatic color level (V , , , f) to form gain control signals R2 and B2 for the R signal and the B signal, respectively. A limiter that limits the gain control signals R2 and B2 output from the second gain control signal forming circuit 9.

11a and jlb are the limited control signal R2°B2 and the control signal R1 from the first gain control signal forming circuit 8.
, B2 and outputs the result.

In the circuit shown in FIG. 5 above, the first gain control signal forming circuit 8
A limiter 10a is applied to the control signals R1 and Bl output from
, 10b, the second width is regulated to a predetermined limit width by
The control signals R2 and B2 from the gain control signal forming circuit 9 are added to form the R correction signal and the B correction signal. This signal is transmitted to the white balance control amplifier 3a in FIG.
3b as a control signal, and the white balance is optimally controlled. In this way, the gains of the white balance control amplifiers 3a and 3b are controlled based on both the output information from the CCD 1 and the detection information of the color temperature sensor 6 in FIG. 1, and the white balance is appropriately corrected. Ru.

[Problem to be solved by the invention]

However, in conventional white balance correction devices such as those described above, the regulation range of the limiter is fixed to a preset value, so the distance between the imaging device equipped with a zoom lens and the subject is not constant. Even the zoom ratio (magnification) of a zoom lens.

Depending on the focal length (focal length), the color of the subject may or may not be affected, resulting in unstable operation and the inability to perform proper white balance correction.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a white balance correction device that can perform appropriate white balance correction with stable operation regardless of the zoom ratio of a zoom lens.

[Means to solve the problem]

The white balance correction device of the present invention is configured as follows.

1. In a white balance correction device for an imaging device equipped with an image sensor that photoelectrically converts imaging light from a subject and a zoom lens, a color temperature detection means for detecting color temperature information of incident light from the subject; A zoom ratio detection means for detecting a zoom ratio, and a white balance control circuit for controlling white balance based on output information from the image sensor, detection information of the color temperature detection means, and detection information of the zoom ratio detection means. Ta.

(2) In the device of Takiki I, the white balance control circuit changes the white balance control signal based on the output information of the image sensor and the detection information of the color temperature detection means based on the detection information of the zoom ratio detection means and outputs the resultant signal. I did it like that.

m. An image sensor that photoelectrically converts imaging light from a subject, a color separation circuit that separates a plurality of color signals from the output signal of this image sensor, and a gain control that controls the gain of a predetermined color signal among the color signals. and a zoom lens, the color temperature detection means detecting color temperature information of incident light from a subject, and the zoom ratio detecting a zoom ratio of a front zoom lens. and a white balance control circuit that outputs a control signal for white balance correction to the gain control means, the white balance control circuit forming a gain control signal according to information detected by the color temperature detection means. a first gain control signal forming circuit that forms a gain control signal from a result of comparing the level of a color signal from an image sensor with a reference level;
#limiting means for limiting the output of the signal forming circuit based on the detection information of the zoom ratio detecting means, and a control signal based on the output limited by the limiting means and the output of the first gain control signal forming circuit; is outputted to the gain control means.

(Function) The white balance correction device of the present invention is provided with a zoom ratio detection means for detecting the zoom ratio (magnification, focal length) of the zoom lens, and the detection information of the zoom ratio detection means and the output from the image sensor are White balance is controlled based on the information and color temperature information. Therefore, it is possible to prevent the operation from becoming unstable due to the zoom ratio.

〔Example〕

FIG. 1 is a block diagram showing the circuit configuration of a white balance correction device according to an embodiment of the present invention, and the same reference numerals as in FIG. 4 indicate the same components. In the figure! 2 is a CCD (solid-state image sensor) that photoelectrically converts the imaging light from the subject; 2 is a color separation circuit that separates multiple color signals from the output signal of CCD 1; specifically, the three primary color signals of R, G, and B; Separate and output. Reference numerals 3a and 3b denote white balance control amplifiers (gain control means) for controlling the gain of a predetermined color signal among the three primary color signals, and here variable gain control is performed for each of the R and B color signals. 4 is R and B output from these white balance control amplifiers 3a and 3b.
5 is a signal processing circuit which receives the color signal of G and the color signal of G outputted from the color separation circuit 2 and generates a luminance signal Y and color difference signals R-Y and B-Y; 5 indicates the luminance signal Y and color difference signal R;
A signal processing circuit that generates and outputs a standard television signal from -Y and B-Y, 6 a color temperature sensor (color temperature detection means) that detects color temperature information of incident light from a subject, and 12 an imaging device. A zoom encoder (zoom ratio detection means) 13 detects the zoom ratio of the provided zoom lens, and detects the white balance based on the output information from the CCD 1, the detection information from the color temperature sensor 6, and the detection information from the zoom encoder 12. The white balance control circuit that controls
The above color difference signal RY generated by the signal processing circuit 4 as output information from the DI.

B-Y is input, and the white balance control amplifier 3a
, 3b output a control signal for white balance correction.

FIG. 2 is a diagram showing the internal configuration of the white balance control circuit 13, and the same reference numerals as in FIG. 5 indicate the same components. In the figure, 8 is a first gain control signal forming circuit that forms gain control signals (white balance correction signals) R1 and Bl according to the detection information (color temperature information) of the color temperature sensor 6, and 9 is a first gain control signal forming circuit that forms gain control signals (signals for white balance correction) R1 and Bl according to the detection information (color temperature information) of the color temperature sensor 6. Gain control signals R2, B are obtained from the result of comparing the level of the color signal (here, the level of the color difference signals R-Y, B-Y) with the reference achromatic color level (vref).
1. A second gain control signal forming circuit forming 2, 14a, 1
4b is a limiter that limits the output of the second gain control signal forming circuit 9 based on the output information of the limit width variable means 15, and the limit width variable means 15 includes a zoom encoder 12.
detection information (zoom ratio information) is supplied. Then, the output limited by the limiters 14a, 14b and the output of the first gain control signal forming circuit 8 are combined into a computing unit 11a,
The R correction signal and B correction signal added by flb are supplied to white balance control amplifiers 3a and 3b as control signals.

Next, the operation will be explained.

The signal processing operation from when the imaging light from the subject enters the CCDI until the standard television signal is output from the signal processing circuit 5 is the same as that of the apparatus shown in FIG. A zoom encoder 12 is provided to detect the zoom ratio of the zoom lens, and white balance control is performed in consideration of the zoom ratio information detected by the zoom encoder 12. That is,
The white balance control circuit 13 sends a white balance control signal based on output information from the CCD 1 and color temperature information from the color temperature sensor 6 to the zoom encoder 12.
The white balance control amplifier 3a is changed based on the zoom ratio information from the white balance control amplifier 3a.

I am trying to output it to 3b. Therefore, the color of the subject is not affected by the zoom ratio, and appropriate white balance correction can be performed with stable operation regardless of the zoom ratio of the zoom lens.

Figure 3 shows the zoom ratio of the zoom lens and the limiter 1 in Figure 2.
4a and 14b show the relationship with the limit width. With the characteristics shown in FIG. 3, the limiters 14a, 14
b works, but this characteristic is a characteristic when the distance between the camera or imaging device and the subject is constant and the zoom ratio changes; This is expected to increase the probability that it will become easier. Therefore, in addition to the characteristics shown in FIG. 3, characteristics may also be adopted that take into consideration the variable width of the zoom ratio, the directivity of the color temperature sensor 6, and the like.

Note that the zoom encoder 12 that detects the zoom ratio may be of any type.

(Effects of the Invention) As described above, according to the present invention, a zoom ratio detection means for detecting the zoom ratio of a zoom lens is provided, and detection information of the zoom ratio detection means, output information from an image sensor, and color temperature are provided. Since the white balance is controlled based on the information, there is an effect that appropriate white balance correction can be performed with stable operation regardless of the zoom ratio of the zoom lens.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of a white balance correction device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the internal configuration of the white balance control circuit of FIG. 1, and FIG.
The figure is a characteristic diagram showing the relationship between the zoom ratio of the zoom lens and the limit width of the limiter shown in Fig. 3, Fig. 4 is a block diagram showing the circuit configuration of the conventional device, and Fig. 5 is the white balance control circuit shown in Fig. 4. FIG. 2 is a configuration diagram showing the internal configuration of. 1---CCD (solid-state image sensor) 2---Color separation circuit 4.5---Signal processing circuit 6---Color temperature sensor (color temperature detection means) 8---
. . . First gain control signal forming means 9 --- Second gain control signal forming means 11 a, 1 l b ---
--- Arithmetic unit 12 --- Zoom encoder (zoom ratio detection means) 13 ... White balance control circuit 14 a, 14 b --- Limiter (limiting means) 15 ... −・Limit width variable means

Claims (3)

[Claims] (1) In a white balance correction device for an imaging device that includes an image sensor that photoelectrically converts imaging light from a subject and a zoom lens, a color temperature detection means that detects color temperature information of incident light from the subject, and the zoom lens and a white balance control circuit that controls white balance based on the output information from the image sensor, the detection information of the color temperature detection means, and the detection information of the zoom ratio detection means. A white balance correction device characterized by being equipped with. (2) The white balance control circuit is characterized in that the white balance control circuit outputs a white balance control signal based on the output information from the image sensor and the detection information of the color temperature detection means, while changing the white balance control signal based on the detection information of the zoom ratio detection means. The white balance correction device according to claim 1. (3) an image sensor that photoelectrically converts imaging light from a subject;
White balance correction for an imaging device that includes a color separation circuit that separates a plurality of color signals from the output signal of the image sensor, gain control means that controls the gain of a predetermined color signal among the color signals, and a zoom lens. The apparatus includes a color temperature detection means for detecting color temperature information of incident light from a subject, a zoom ratio detection means for detecting a zoom ratio of the zoom lens, and a control signal for white balance correction to the gain control means. a first gain control signal forming circuit that forms a gain control signal according to the detection information of the color temperature detection means; and a white balance control circuit that outputs a color signal from the image sensor. a second gain control signal forming circuit that forms a gain control signal from the result of comparing the level of the signal with a reference level; and a restriction that limits the output of the second gain control signal forming circuit based on the detection information of the zoom ratio detecting means. A white balance correction device comprising: means for outputting a control signal based on the output limited by the limiting means and the output of the first gain control signal forming circuit to the gain controlling means.