JPH027788A - Automatic white balance control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic white balance control arrangement useful for use, for example, in multiple child cameras (secondary still cameras or color video cameras).

2. Description of the Related Art A conventional example of an automatic white balance control device for a Shizuoka camera will be described with reference to FIG. The color temperature of the subject is
The color information output signals r, , g, , b, detected by the color temperature detection sensor 1 are input to the switching circuit 14 . Further, predetermined signals are stored in the memory 3, and color information output signals r242. b2 is switching circuit 1
4 is input. The color temperature detection sensor 1 has a finite sensitivity to low-illuminance subjects, and when photographing a low-illuminance subject below the detection sensitivity, a low-illuminance detection signal is output and input to the switching circuit 14. The switching circuit 14 outputs a color information output signal r2 when there is a detection signal depending on the presence or absence of a low illuminance detection signal.
"2" Select 2, and if there is no color information output 1 word r
+ +g1. Select b1. Output r4 of switching circuit 14
+g4+b4 is input to the color temperature processing circuit 7. The optical image of the subject is input to the image pickup device or image pickup tube 8 through the lens, and electrical signals R and G are input.

A luminance signal Y and a color difference signal (RY) 1. Yl, (RY)1.(B-Y)1 is a control signal outputted from the color temperature processing circuit 7 in order to obtain white balance, and is converted to the control circuit 10. , 11, 12, and output as a white balanced video signal by the subsequent signal processing circuit 13.

Problems to be Solved by the Invention However, the automatic white balance control device configured as described above cannot perform white balance control using the signal value in the memory 3 at low illuminance where the color temperature detection sensor 1 does not operate normally. As a result, the white balance control does not follow the subject whose color temperature changes under low illumination, and the white balance can only be achieved when the color temperature is at a certain level. It had the problem of causing deterioration.

In view of this, it is an object of the present invention to provide an automatic white balance control device that allows white balance control to follow even a subject with low illuminance, does not cause deterioration in image quality, and reduces the number of failed shots.

Means for Solving the Problems In order to solve the above problems, the automatic white balance control device of the present invention detects the color temperature of the subject to be photographed, and sends out a low-light detection signal when the light is too low to be tracked by its detection sensitivity. a writable first memory that stores the color information signal only when the low-light detection signal is not output; a nonvolatile second memory that stores a predetermined color information signal; and a camera. and means to detect whether the camera's lens cover is open or closed, and when the sensor's low-light detection signal is not output, white balance control is performed using the sensor's color information signal, and then, When a low-light detection signal from the sensor is output and the camera continues to be powered off and the lens cover continues to be open, white balance control is performed using the color information signal stored in the first memory; When the camera power is once opened or the lens cover is once closed and the low-light detection signal of the sensor is detected immediately after the camera starts shooting, white balance control is performed using the color information signal stored in the second memo IJ-. According to the present invention, with the above-described configuration, at the illuminance at which the color temperature detection sensor normally operates, white balance control is performed based on the output of the color temperature detection sensor, and a writable memory is also provided. The signal of the color temperature detection sensor is memorized in the memory, and in low light conditions where the color temperature detection sensor does not work properly, you can use the value in the memory above unless you turn off the camera or cover the lens. , because it performs white balance control, it is possible to shoot a subject at a certain color temperature and output an image with a good white balance even when the color temperature changes to low light. Furthermore, even if the color temperature sensor does not work properly when shooting low-light situations, which are rare, you can still switch to the conventional white balance control mode by turning off the camera or covering the lens. This enables shooting with good image quality and fewer mistakes.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an automatic white balance control device in one embodiment of the present invention.

The color temperature of the subject is detected by a color temperature detection sensor 1, and color information output signals r, gl, b are input to a switching circuit 4. Furthermore, when the low illuminance detection signal from the color temperature detection sensor 1 is not output, it is simultaneously written into the writable non-volatile memory 2. The output signals "s+gs, bs" of the memory 2 are input to the switching circuit 4. Predetermined signals are still stored in the memory 3, and the color information output signal r22g2.b2 is input to the switching circuit 4.
is input. If there is no low illuminance detection signal, the switching circuit 4 outputs the color information output signal r19g1. Select b1. When there is a low illuminance detection signal, the camera power supply opening/closing detection circuit 6 detects on, and the lens cover opening/closing detection circuit 6 detects an open state, the switching circuit 4 outputs the color information output signal r34g5.
．． Select b5. When there is a low illuminance detection signal and the camera power supply opening/closing detection circuit 6 detects OFF or the lens cover opening/closing detection circuit 6 detects a closed state, the switching circuit 4 is reset and the color information output signal r21g2. Select b2. The output r41g4 +b4 of the switching circuit 4 is input to the color temperature processing circuit 7, which performs the same operation as the conventional example.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, when subjects are photographed under the same color temperature, even if the illuminance reaches a point where the color temperature detection sensor cannot detect it, the camera can be turned off or the lens cover can be closed. Unless you do this, correct white balance control will occur, and when shooting under conditions where color temperature changes
There are very few cases where the light is low from the moment you start shooting (power on or lens cover open), but even in those cases, constant white balance control is available, so you can easily shoot with good image quality and fewer mistakes. The effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an automatic white balance control device of the present invention, and FIG. 2 is a block diagram of a conventional automatic white balance device. 1...Color temperature detection sensor, 2...Memory (first), 3...Memory (second), 4...
Switching circuit, 6...Camera power supply opening/closing detection circuit, 6.
...Lens cover opening/closing detection circuit, 7...Color temperature processing circuit, 8...Image sensor or image pickup tube, 9...
...Previous stage signal processing, 10.11.12... Control circuit, 13 - Post-stage signal processing.

Claims (1)

[Claims] A sensor that detects the color temperature of the subject to be photographed and outputs a color information signal, and outputs a low-light detection signal when the light is too low to react with its detection sensitivity, and a sensor that outputs a low-light detection signal when the low-light detection signal is not output. a writable first memory for storing a color information signal; a non-volatile second memory for storing a predetermined color information signal; a means for detecting opening/closing of a camera power supply; and opening/closing of a camera lens cover. When the low-light detection signal of the sensor is not output, white balance control is performed using the color information signal of the sensor, and after that, when the low-light detection signal of the sensor is detected, the camera power continues to be closed and If the lens cover remains open, white balance control is performed using the color information signal stored in the first memory, and the camera power is once opened or the lens cover is once closed and the camera starts shooting. An automatic white balance control device characterized in that the automatic white balance control device is configured to perform white balance control using a color information signal stored in a second memory when a low illuminance detection signal of the sensor is detected.