JPS6350290A - Adjusting cirtcuit for white balance of color video camera - Google Patents

Abstract

PURPOSE:To eliminate a erroneous photographing such as pnotographing an outdoor object through a room, which is caused by the erroneous adjustment of white balance, by providing a means that decides whether white balance is correct or not according as the integration value of a color difference signal lies within a range at a prescribed level or not and that displays the results. CONSTITUTION:With chrominance components R-YL and B-YL as an input, integration circuits 19 and 20 integrate the signals, and window comparators 21 and 22 detect whether two integrated outputs lie within the range of the prescribed level + or -delta with the outputs of the integration circuits 19 and 20 as an input. If at least one of the window comparators 21 and 22 has the output of a logic '1', an OR gate 23 obtains the output of a logic '1', which is taken out as the lighting output of a displayed light emitting diode LED in a finder by a display 24. Thus, a photographer can know whether white balance adjustment is correct or not when he takes a picture.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a white balance adjustment circuit for a color video camera.

Background of the Invention - In a color video camera, the quality of light illuminating the subject (
Since the hue (color temperature) changes depending on the scene (outdoors and indoors, sunny and cloudy skies, incandescent and fluorescent lights, etc.), basic adjustments are made to accurately reproduce the colors of the subject illuminated at the standard color temperature. It is equipped with a white balance adjustment means that allows you to adjust white subjects so that they appear white when photographing.

There are known methods for this white balance adjustment, such as interposing a color temperature conversion filter, adjusting the gain of the camera's color signal circuit, or switching the circuit. A method for automatically adjusting the color signal gain to zero has been put into practical use, and an automatic color temperature adjustment method has also been proposed that detects the color temperature of the light source illuminating the subject and automatically adjusts it based on that value. .

Problems to be Solved by the Invention - In the conventional automatic adjustment method, incorrect white balance adjustment may occur. For example, when photographing the outdoors from indoors, the color sensor for automatic color temperature adjustment detects the indoor color temperature, and adjusts the gain of the color signal circuit accordingly. The captured image will be emphasized. Conversely, when photographing a room from outside, the image will have red emphasized for the same reason. Also, in low light conditions, the non-linearity of the color sensor's detection characteristics caused erroneous adjustments.

On the other hand, conventional manual adjustment methods are limited to rough adjustments such as switching with switches, and it is confusing to judge the adjustment direction and adjustment level for the color temperature of the subject, and there are cases where the adjustment is forgotten. In many cases, it is only possible to determine whether the image is appropriate or not by replaying the image, which sometimes results in failure in photographing.

An object of the present invention is to provide a white balance adjustment circuit that prevents errors from occurring in white balance adjustment for the color temperature of an object.

Means for Solving a Problem - In order to achieve the above-mentioned object, the present invention provides a pair of integrating circuits that respectively integrate two color difference signals separated from an imaging signal, and a system in which the outputs of the pair of integrating circuits are A pair of window comparators that detect whether or not the level is within a predetermined level range, and a display that indicates that the white balance is inappropriate when at least one of the outputs of the pair of window comparators has a detection output that exceeds the predetermined level range. It is equipped with a circuit.

One Embodiment - FIG. 1 is a circuit diagram showing one embodiment of the present invention. The imaging signal of the subject by the imaging device 1 is sent to the luminance signal processing circuit 2
The luminance signal YH is taken out by the color signal separation circuit 3, and the narrowband luminance signal YL and the red and green color signals R9B are extracted.
is taken out. The chrominance signals R and B are each supplied with a gain control amplifier 4,
5, the differential amplifiers 6 and 7 calculate the difference between the luminance signal YL and the color difference signal R-YL.
, B 7 Y L . These color signals R-YL and B-YL are phase-modulated by a modulation circuit 8, and added to a luminance signal Y)I by an adder 9, thereby being extracted as a video signal.

The gain control amplifiers 4 and 5 perform white balance adjustment by controlling the gains of the color signals R and H, and this gain control is performed by detecting the color temperature of the subject. That is, the red sensor 10. After the color temperature is detected by the blue sensor 11 and these detection signals are linearized by the logarithmic amplifiers 12 and 13, a difference signal between the rain detection signals is obtained by the differential amplifier 14, and further by the color temperature clipping circuit 15. Clipping is performed, and this signal and the inverted signal from the inverting amplifier 16 are compressed by the signal compression circuit 17 and the signal compression circuit 8, respectively, to form a gain control signal for the gain control amplifier 4.5.

In addition to the automatic color temperature adjustment circuit configured as described above, circuits 19 to 24 are provided in this embodiment. This will be explained in detail below.

Integrating circuits 19 and 20 receive color signals R-YL and B-YL, respectively.
The window comparators 21 and 22 receive the outputs of the integrating circuits 19 and 20, respectively, and detect whether the respective integrated outputs are within a predetermined level ±δ range. This window comparator 21.22
is made to obtain a logic "1" output when the integral output exceeds the ±δ range. The OR gate 23 outputs a logic "1" when at least one of the window comparators 21 and 22 has a logic "1°" output, and this output is output on the display 2.
4. Light emitting diode LED displayed in the viewfinder
It is taken out as the lighting output. The lighting output of the light emitting diode LED is meaningful as an indicator of white balance adjustment.

Integrating circuit 19.20 and window comparator 21,
22 is specifically realized by the configuration shown in FIG. The figure shows an integrating circuit 19 and a window comparator 2.
1, the integrating circuit is a resistor R1.

It is configured with R2 and capacitor C. The window comparator has a level + set by the voltage division of resistors R3 and R4.
δ, an upper limit detection circuit using an operational amplifier OF + , and a resistor R5.

It is composed of a lower limit detection circuit using the level -δ set by R6, an operational amplifier OP2, and a NAND game (Nando game) G that takes the logical sum of the outputs of both operational amplifiers OF, OP2.

The operation of the configuration described above will be explained. In automatic color temperature adjustment by gain control of gain control amplifier 4.5, if the color temperature of the actual imaged screen is appropriate, the color difference signal R
-YL.

The value obtained by integrating B - Y L over the entire screen or several screens becomes approximately zero. Therefore, the color temperature-adjusted color difference signal R-YL,
B-YL is integrated by an integrating circuit 19 and 20 with a time constant corresponding to one entire screen or several screens, and window comparators 21 and 22 determine whether each integrated output is within a level range of ±δ. By detecting this, it is possible to determine that the color temperature adjustment of the imaging signal is appropriate, that is, that the white balance adjustment is properly performed. As a result of this determination, by associating the LEDs of the display driver 24 with lighting and turning off, it is possible to inform the photographer whether white balance adjustment is appropriate or inappropriate at the time of shooting. When this display becomes an unfriendly display, the white balance adjustment is switched to manual adjustment in consideration of the photographed image, thereby obtaining a photographing state that provides an appropriate display, and photographing with an appropriate white balance is made possible.

In addition, in the example, the case of a color video camera with automatic color temperature adjustment is shown, but this can be applied to a camera with manual adjustment or a camera with preset automatic white balance adjustment to obtain the same effect. Can be done.

Furthermore, although a level determiner is used for each of R-YL and B-YL this time, it is also possible to integrate R-YL and B-YL and then add them, and then determine the level based on the value.

Effects of the Invention As is clear from the above description, the present invention determines the appropriateness of white balance depending on whether the integral value of the color difference signal is present in a predetermined level determiner.

Since a means for determining and displaying unsuitability is provided, it is effective to eliminate photographing due to incorrect white balance adjustment, such as when photographing from indoors to outdoors.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
It is a specific circuit diagram of the integrating circuit and the window comparator in the figure. 1... Imaging device, 2... Luminance signal processing circuit, 3... Color signal separation circuit. 4.5...Gain control amplifier, 8...Modulation circuit, 10.11...Sensor, 19.20...Integrator circuit, 21.22...Window comparator, 24...
display driver.

Claims (1)

[Claims] 1) A pair of integrating circuits that respectively integrate two color difference signals separated from an imaging signal, a pair of window comparators that detect whether the outputs of these pair of integrating circuits are within a predetermined level range, and A solution for white balance adjustment of a color video camera, comprising a display circuit that displays inappropriate white balance when at least one of the outputs of a pair of window comparators has a detection output exceeding the predetermined level range.