JP2708970B2 - Color video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic white balance adjusting device for a color video camera for controlling a white balance based on an image signal obtained from an image sensor.

[0002]

2. Description of the Related Art In a color video camera, it is necessary to control a white balance in order to correct a difference in wavelength distribution of light depending on a light source. This control is performed in red (hereinafter R),
The ratio of the three primary color signals of blue (hereinafter B) and green (hereinafter G) is 1:
This is performed by adjusting the gain of each color signal so as to be 1: 1. Generally, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-35792 (H04N9 / 73), a method is used in which the gain is adjusted so that the integral values of the color difference signals RY and BY of the screen become zero. Have been.

FIG. 2 is a block diagram of a white balance adjustment circuit using this method. The light that has passed through the lens 1 is photoelectrically converted by an imaging device (CCD) 2 and then converted into a color separation circuit 3.
Are extracted as three primary color signals of R, G, and B. The G color signal is directly passed through, and the R and B color signals are passed through an R amplifier circuit 4 and a B amplifier circuit 5 to a camera process and matrix circuit 6.
, And a luminance signal Y and color difference signals RY and BY of red and blue are generated and sent to the video circuit 7.

At the same time, the two color difference signals are respectively integrated by integrating circuits 17 and 18 for a sufficiently long time, and gain control circuits 13 and 14 are controlled by gain control circuits 13 and 14 so that the result becomes zero. Adjust the gain of 5.

[0005]

In the above-described method, when a general subject is photographed, a rule of thumb is that a value obtained by averaging the color difference signals of the entire screen is equivalent to a case where a completely white surface is photographed. Therefore, it is necessary that the photographing screen contains each color on average.

However, in this method, when the color of the subject itself is biased, for example, when a person wearing red or blue data is closed up, even if the color distribution of the entire screen is averaged. When the white balance adjustment is performed on such a subject as described above, the gain changes in the direction to cancel the biased color and the white balance shifts to the complementary color side, and the white color state is not adjusted. There is a disadvantage that reproduction cannot be performed.

[0007]

The difference in the wavelength distribution of a light source is generally represented by a color temperature (unit: Kelvin: K). FIG. 3 shows the color temperatures of various light sources. Thus, the color temperature of natural light has a bluish color of 5000 K or more, and the color temperature of artificial light has a reddish color of 5000 K or less. Usually, considering that natural light exists outdoors and artificial light exists indoors, when shooting outdoors, only the gain correction in the direction of increasing the R signal and decreasing the B signal is performed. At the time of photographing, only gain correction in the direction of increasing the B signal and decreasing the R signal may be performed.

Accordingly, the present invention provides a method for controlling a luminance signal level in an imaged video signal or a diaphragm control signal for controlling a diaphragm amount of a diaphragm mechanism so that the luminance signal becomes an optimum level.
It is characterized in that it is distinguished between an indoor shooting state and an outdoor shooting state, and the characteristic of the white balance adjustment operation is changed according to the result.

[0009]

Since the present invention is constructed as described above, even if a person wearing a red data outdoors or a person wearing a blue data indoors is closed up, the color is canceled. The white balance does not shift to the complementary color side by changing the gain in the direction. Therefore, stable white balance adjustment can be performed.

[0010]

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

FIG. 1 is a circuit block diagram of the automatic white balance adjusting device according to the present embodiment.

Light incident on the lens 1 is transmitted to an optical diaphragm mechanism 8.
, And after being imaged on the CCD 2 and photoelectrically converted,
The color separation circuit 3 extracts the three primary color signals of R, G, and B. The R and B signals among these three primary color signals pass through R and B amplifier circuits 4 and 5, respectively, and are input to the camera process and matrix circuit 6 together with the G signal. Based on these signals, the luminance signals Y, R, and B are output. The respective color difference signals RY, BY
Is generated, supplied to the video circuit 7, and subjected to known processing.

The RY and BY signals are supplied to integrating circuits 18 and 17, respectively, and simultaneously the luminance signal Y
Is supplied to the integration circuit 19. Each integrating circuit digitally integrates the input signal over a certain period of time, for example, one field period, and obtains the integrated values as the color evaluation values r and b and the luminance evaluation value y for each field.

The reference level of the two color difference signals input to the integrating circuits 17 and 18, ie, the zero level, is set in advance to a level obtained when a complete achromatic surface is photographed.
Therefore, it goes without saying that each color difference signal can take not only a positive value but also a negative value.

The luminance evaluation value y is input to a subtractor 24,
It is compared with a reference value Vref set in advance so as to obtain the optimum exposure state, where M = Vref-y is subtracted, and this subtraction value M is supplied to the iris motor unit 30 and the indoor / outdoor discrimination circuit 23. Is done.

The iris motor unit 30 drives the iris motor in accordance with the subtraction value M to change the aperture of the optical aperture mechanism 8 and executes an automatic exposure adjustment operation for keeping the brightness of the screen at an optimum constant level. I do. That is, as shown in FIG. 4, when the luminance evaluation value y increases, the subtraction value M decreases, and the optical diaphragm mechanism 8 operates in the closing direction to reduce the amount of light incident on the CCD 2. Conversely, when the luminance evaluation value y decreases, the subtraction value M increases, and the optical diaphragm mechanism 8 operates in the opening direction to increase the amount of light incident on the CCD 2.

On the other hand, the indoor / outdoor discriminating circuit 23 is provided with a threshold value Vt for discriminating between indoor and outdoor, as shown in FIG. 4, and when the input subtraction value M is larger than the threshold value Vt, The control signal S at the H level is issued assuming that the camera is in the shooting state, and the control signal S at the L level is issued when it is smaller than the threshold value, assuming that the camera is outdoors.

The control signal S thus generated is input to the gain control circuits 33 and 34. In the conventional example, as shown in FIGS. 5 and 6, when the input color evaluation values r and b are equal to or greater than zero, the gains Gr and B of the R amplifier circuit 4 increase as the evaluation values increase. Gain Gb of amplifier circuit 5
Is adjusted in such a way that the gain becomes larger as the evaluation value becomes smaller when the value is less than or equal to zero, and adjustment is made so that the two-color evaluation value is always at the zero level. Control considering the control signal S is added to these gain adjustment operations.

That is, when the control signal S at the H level is input when it is determined that the camera is in the indoor photographing state, the color evaluation value r is negative and the color evaluation value b is positive, as indicated by the solid lines in FIGS. Is fixed at 1, that is, the operation is performed so that the gain adjustment is not substantially performed. As a result, even if the person wearing the blue data is photographed indoors in a close-up manner and the color evaluation value b is increased, the gain Gb is suppressed from being reduced, and the white balance may be shifted in the direction to cancel the blue. Absent.

When an L-level control signal S is input in the outdoor shooting state, the color evaluation value r is positive and the color evaluation value b is negative, as indicated by the solid lines in FIGS. Was fixed at 1. As a result, even when the person wearing the red sweater is photographed outdoors in close-up and the color evaluation value r increases, the gain Gr is prevented from decreasing, and the white balance does not shift in the direction to cancel the red color.

As described above, by switching the operation of the white balance adjustment based on the indoor / outdoor judgment, it is possible to perform a stable white balance adjustment that is hardly affected by the color of the subject.

Note that, as shown in FIG.
The luminance evaluation value y is input in place of the subtraction value M, and the threshold value yt of FIG. 4 is set. When the evaluation value y is larger than the threshold value yt, the control signal S is determined to be indoor and the control signal S is inversely evaluated. When the value y is smaller than the threshold value yt, it is possible to determine whether the control signal S is at L level or not.

It is needless to say that the operation of each circuit described above can be processed by software using a microcomputer.

[0024]

Since the present invention is constructed as described above, even if a person who wears red data outdoors or a person who wears blue data indoors, etc. The gain changes in the direction to cancel the white balance, and the white balance does not shift to the complementary color side, and stable white balance adjustment becomes possible.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of one embodiment of the present invention.

FIG. 2 is a circuit block diagram of a conventional example.

FIG. 3 is a diagram illustrating color temperatures of various light sources.

FIG. 4 is a diagram showing a relationship between a luminance evaluation value y and a subtraction value M.

FIG. 5 is a diagram showing a conventional relationship between a color evaluation value r and a gain Gr set accordingly.

FIG. 6 is a diagram showing a conventional relationship between a color evaluation value b and a gain Gb set accordingly.

FIG. 7 is a diagram showing a relationship between a color evaluation value r in an indoor shooting state and a gain Gr set accordingly.

FIG. 8 is a diagram illustrating a relationship between a color evaluation value b in an indoor shooting state and a gain Gb set accordingly.

FIG. 9 is a diagram showing a relationship between a color evaluation value r in an outdoor shooting state and a gain Gr set accordingly.

FIG. 10 is a diagram illustrating a relationship between a color evaluation value b in an outdoor shooting state and a gain Gb set accordingly.

FIG. 11 is a circuit block diagram of another embodiment.

[Explanation of symbols]

 4 R amplification circuit 5 B amplification circuit 33, 34 Gain control circuit 23 Indoor / outdoor discrimination circuit 24 Subtractor

Claims (2)

(57) [Claims] 1. A white balance adjusting means for performing a white balance adjusting operation for controlling a gain of each color signal based on a color information signal in a captured video signal, and a brightness signal level in the captured video signal is an optimum level. Exposure control means for issuing an aperture control signal to the aperture adjustment means to adjust the aperture amount of the aperture adjustment means, and indoor / outdoor determination means for determining whether an indoor shooting state or an outdoor shooting state based on the aperture control signal. In the indoor shooting state, only the gain correction in the direction of increasing the B signal and decreasing the R signal is enabled, and in the outdoor shooting state, only the gain correction in the direction of increasing the R signal and decreasing the B signal is enabled. A color video camera characterized by changing characteristics of a white balance adjustment operation. 2. A white balance adjusting means for executing a white balance adjusting operation for controlling a gain of each color signal based on a color information signal in a captured video signal, and an indoor shooting state based on a luminance signal level in the captured video signal. Indoor / outdoor determining means for determining whether the signal is in an outdoor shooting state. Only the gain correction in the direction of increasing the B signal and reducing the R signal in the indoor shooting state is enabled, and increasing the R signal and reducing the B signal in the outdoor shooting state. A color video camera, wherein the characteristic of the white balance adjustment operation is changed so as to enable only the gain correction in the direction in which the white balance is adjusted.