JPS61208993A - White balance adjustment device for electronic camera - Google Patents

Abstract

PURPOSE:To provide for high precision white balance adjustment by switching the output of the image pickup element and the output of the pseudo image pickup signal generating circuit and outputting the resulting output to an image pickup signal processing circuit so as to make a feedback control of the white balance of the image pickup signal processing circuit. CONSTITUTION:Color sensors 2R, 2G and 2B are disposed at positions on which the light passed through a white filter 1 is irradiated and every sensor outputs are introduced into a pseudo image pickup signal processing circuit 13. The output of the circuit 13 is supplied through a switching circuit 14 to an image pickup signal processing circuit 6. An image pickup element 5 is arranged at a position on which the light passed through a shutter 4 is irradiated, and the output of the element 5 is supplied through a circuit 14 to a circuit 6. The circuit 13 in controlled by a system control circuit 8 to produce pseudo image pickup signal equvalent to the output from the element 5. The white balance adjustment of the circuit 6 is controlled by feedback fashion by the detected output of the error detecting circuit 15. In such a manner, the white balance of the circuit 6 is controlled with high precision and the image pickup signal may be outputted through an encoder.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Technical Field The present invention relates to a white balance adjustment device for an electronic camera.

b. Prior art and its problems In electronic cameras, white balance is adjusted in accordance with changes in the color temperature of a light source in order to achieve good color reproduction. This adjustment means can be roughly divided into a manual method and an automatic tracking method.

The manual method is equipped with a white balance preset switch that is preset to achieve white balance for light sources with several color temperatures, and the white balance is preset by switching this switch. This method uses a color temperature detection sensor to constantly detect changes in the color temperature of the light source, and directly controls the corresponding gain of the white balance adjustment variable gain amplifier to adjust the white balance.

On the other hand, as an electronic camera, a multi-mode electronic camera has recently been proposed that has an electronic still mode, a video camera mode, and a mode that records one screen while looking at the monitor (hereinafter referred to as the 15-hot video camera mode). For some types of electronic cameras, especially when they have an electronic still camera mode, mobility and quick shooting performance are required, so automatic tracking white balance adjustment is considered suitable. An example of a conventional electronic camera that performs white balance adjustment using automatic tracking is as follows.
There is something like the one shown in Figure 3. In FIG. 3, ■ is a white filter, 2R12G, 2B is a color sensor, and 3 is a white balance control circuit.

4 is a shutter, 5 is an image sensor, 6 is an image signal processing circuit,
7 is an encoder, 8 is a system control circuit, 9 is a synchronizing signal generation circuit, 10 is a release pulse input terminal, 11 is a mode switching signal input terminal, and 12 is a composite color television signal output terminal. The light that has passed through the white filter 1 is incident on sensors 2R52G and 2B that are sensitive to red, green, and blue, respectively, and is input as a signal to the white balance control circuit 3 via the sensors 2R12G and 2B. The white balance control circuit 3 outputs a white balance control signal to control the gain of a variable gain amplifier for white balance adjustment in the imaging signal processing circuit 6, thereby adjusting the white balance. When a release pulse is input to the release pulse input terminal 10 while electronic still camera mode No. 46 is input to the mode switching signal input terminal 11, the shutter 4 is activated by the shutter drive pulse from the system control circuit 8. The opening/closing operation is performed, and an imaging output signal is input from the imaging element 5 to the imaging signal processing circuit 6 . Further, when the video camera mode or I5hot video camera mode signal is input to the mode switching signal input terminal 11, the shutter 4 is kept open regardless of the presence or absence of the release pulse, and the image sensor 5 is continuously An imaging output signal is inputted to the imaging signal processing circuit 6 from. The imaging output signal is red (R),
After being separated into green (G) and blue (B) component signals,
The signal is inputted to a variable gain amplifier for white balance adjustment to perform white balance adjustment, inputted to an encoder 7, and outputted from an output terminal 12 as a composite color television signal. In such conventional electronic cameras that perform white balance adjustment using an automatic tracking method or a manual method, the gain of the variable gain amplifier for white balance adjustment is controlled in an open loop, and the white balance adjustment status is fed back to the control device. Therefore, it is not possible to evaluate the white balance adjustment state, especially in electronic still camera modes where the output signal from the image sensor is not obtained until the release switch is turned on and the shutter completes the opening/closing operation. Since the control of a variable gain amplifier for white balance adjustment having control characteristics is incomplete, proper white balance adjustment becomes difficult, and problems often arise in which a problem with white balance adjustment is noticed only after viewing the reproduced image after being captured.

C0 Purpose The present invention has been made in view of the above points, and is an electronic system that can constantly evaluate the white balance adjustment state in all imaging/recording modes, thereby enabling highly accurate white balance adjustment. The purpose of the present invention is to provide a white balance adjustment device for a camera.

d. Configuration of the embodiment An embodiment of the present invention will be described below based on one drawing.

In FIG. 1, color sensors 2R, 2G, and 2B, which are sensitive to red, green, and blue, are arranged at positions where the light that has passed through the white filter 1 hits.
, 2B are connected to the pseudo image signal generation circuit 13.

The output of the pseudo image signal 13 is sent to the white balance Fill! via the switching circuit 14. It is connected to an imaging signal processing circuit 6 equipped with a variable gain amplifier. On the other hand, an image sensor 5 is arranged at a position where the light passing through the shutter 4 hits, and the output of the image sensor 5 is connected to the image signal processing circuit 6 via a switching circuit 14. The output of the imaging signal processing circuit 6 is connected to an encoder 7 and a white balance error detection circuit 15, respectively.

The output of the white balance error detection circuit 15 is input to the white balance control circuit 3, and the output of the white balance control circuit 3 is fed back to the imaging signal processing circuit 6 via the storage circuit 16. Further, the output of the system control circuit 8, which receives signals from the synchronization signal generation circuit 9, the release pulse input terminal 1O, and the mode switching signal input terminal 11, is transmitted to the shutter 4, the image sensor 5, the image signal processing circuit 6. Pseudo image signal generation circuit 13, switching circuit 14, and memory circuit 1
6 are respectively input. The pseudo image signal generation circuit 13 uses a pseudo image signal generation pulse from the system control circuit 8 to generate the color sensor 2 having the same spectral sensitivity characteristics as the image sensor 5 at the same timing as the shutter drive pulse.
The R, 2G, and 2B outputs are sampled to generate a pseudo image signal equivalent to the output from the image sensor 5. This pseudo image signal is equivalent to the output signal of the image sensor 5 when capturing an image of a monochromatic object.

e. Effect of the embodiment Next, the operation of the embodiment of the present invention having the above configuration will be explained.

(1) In the case of electronic still camera mode When the electronic still camera mode signal is input to the mode switching signal input terminal 11, but no release pulse is input from the release pulse input terminal 10 and the shutter 4 is in the open state. Although no imaging output signal is obtained from the imaging device 5, since light is always incident on the color sensors 2R, 2G, and 2B, the pseudo imaging from the pseudo imaging signal generation circuit 13 is performed by the operation of the shutter 4. can always be obtained no matter what. Therefore, until the release pulse is input, the switching circuit 14 is set by the changeover switch control pulse from the system control circuit 8, and the pseudo imaging signal output from the pseudo imaging signal generation circuit 13 is transferred to the imaging signal processing circuit 6. Enter it in. It should be noted that the pseudo imaging signal generation pulse that activates the g-simulation imaging signal generation circuit 13 is output in conjunction with turning on the main power (not shown), and is continuously output while the main power is turned on. do. The imaging signal processing circuit 6 separates the pseudo imaging signal into R, G, and B components in accordance with the signal processing pulse from the system control circuit 8, and passes them through variable gain amplifiers.

White balance error detection circuit 15 that detects adjustment errors
output as a KGB output signal. The white balance control circuit 3 inputs the white balance error signal from the white balance error detection circuit 15 and processes the imaging signal so as to eliminate the error, that is, so that the magnitude of each R, G, and B component becomes equal. A white balance control signal for controlling the variable gain amplifier in circuit 6 is output. At this time, since the storage circuit control pulse from the system control circuit 8 is not output, the storage circuit 16 does not operate, and the white balance control signal is input to the imaging signal processing circuit 6 as it is.

When a release pulse is input from the release pulse input terminal 10, a shutter drive pulse, an image sensor drive pulse, and a memory circuit control pulse are outputted from the system control circuit 8 to the shutter 4, the image sensor 5, and the memory circuit 16, respectively. 16 holds the white balance control state at the time when the release pulse is input to the system control circuit 8;
after that.

The switching circuit 14 is switched by a changeover switch control pulse from the system control circuit 8 to connect the output of the image sensor 5 to the image signal processing circuit 6. Therefore.

The image signal obtained from the image sensor 5 after the shutter 4 completes its opening/closing operation has its white balance properly adjusted by an image signal processing circuit 6 in which white balance control has already been performed, and is sent to a composite color image via an encoder 7. The signal is output from the television signal output terminal 12.

(n) In the case of video camera mode or 15hot video camera mode When the video camera mode or 15hot video camera mode signal is input to the mode switching signal input terminal 11, the shutter 4 is open regardless of the presence or absence of the release pulse. Because it is kept in the state.

The image sensor 5 continuously outputs an image signal in accordance with the image sensor drive pulse. Therefore, normally the switching circuit 1
4, the imaging output signal may be input to the imaging signal processing 6, but even in this type of mode, the imaging signal is not output during the vertical blanking period, so the system control circuit 8 inputs the changeover switch control pulse during this period. is output to operate the switching circuit 14, input the pseudo imaging signal to the imaging signal processing circuit 6, perform white balance adjustment in the same way as in the electronic still camera mode described above, and immediately before the vertical blanking period ends. The storage circuit 16 is operated to maintain the current white balance adjustment state while reading out the next field or frame. Therefore, since the switching circuit 14 performs one switching operation during the vertical blanking period for each field or frame, white balance adjustment is performed for each screen.

Here, the pseudo image signal output from the pseudo image signal generation circuit 13 will be explained. In the above embodiment, the image sensor 5 is placed between the G filters arranged in a checkered pattern, for example.
It includes a charge-coupled device in which color filters are arranged according to a so-called 1ayer arrangement in which R filters are arranged every other row and B filters are arranged between the rows, and image pickup device parallel drive pulses. Then, the image sensor 5 identifies whether it is a GB line or an RG line using a line identification pulse, and the image sensor 5 uses a parallel drive pulse to identify whether it is a GB line or an RG line.
The pixels are sequentially read out one pixel at a time in the order of RG-111 and output as an imaging output signal. On the other hand, the pseudo imaging signal is continuously outputted from the system control circuit 8 at the same timing as the image sensor parallel drive pulse, and the pseudo imaging signal generation circuit 13 is color sensor 2R, 2G
, 2B are appropriately read and output.

Color sensor 2R.

Since the outputs of 2G and 2B are R and G, 81 each, that is, only for one pixel, it is possible to output the above-mentioned pseudo image signal by repeatedly reading them in the order of the pseudo image signal generation circuit 13. Although the above embodiments are based on the premise of a multi-mode electronic camera, the white balance control device of the present invention can also be used individually for an electronic still camera, a video camera, and a video camera. Very effective.

f. Effects As described above, according to the present invention, it is possible to evaluate the white balance adjustment state in the electronic still camera mode of a multi-mode electronic camera or in an electronic still camera, which was previously impossible. White balance adjustment becomes possible. In addition, in multi-mode electronic cameras, the white balance is adjusted immediately before capturing one screen (one field or one frame) and signal processing in all imaging recording modes, so it can quickly respond to changes in the color temperature of the light source. By operating the switching circuit at the appropriate timing, it is possible to create an electronic camera with excellent mobility, quick shooting performance, and color reproducibility, with little adjustment error due to time delay. The same white balance adjustment device can be used in all imaging and recording modes, allowing effective use of the system.

[Brief explanation of drawings]

FIG. 3, which is a diagram for explanation, is a block diagram of a conventional example. 3: White balance control circuit 5: Imaging device 6: Imaging signal processing circuit 8 System control circuit 13: Pseudo imaging signal generation circuit 14: Switching circuit 15:
White balance error detection circuit 16: Memory circuit Patent applicant: Asahi Optical Industry Co., Ltd. Representative Tetsumine Matsumoto) Figure procedure amendment November 27, 1985

Claims (1)

[Claims] a pseudo image signal generation circuit that outputs a signal equivalent to an image output signal from an image sensor; and a switch that switches and connects either the output of the image sensor or the output of the pseudo image signal generation circuit to the image signal processing circuit. a white balance error detection circuit that detects a white balance adjustment error from the output of the imaging signal processing circuit; and a white balance error detection circuit that inputs the output of the white balance error detection circuit and outputs a white balance control signal to the imaging signal processing circuit. a white balance control circuit that controls white balance adjustment using a white balance control circuit; a storage circuit that is interposed between the white balance control circuit and the imaging signal processing circuit and is capable of holding a white balance control signal; A white balance adjustment device for an electronic camera, which includes a system control circuit that operates at a set timing.