JPH0632442B2 - White balance adjustment device for electronic cameras - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. TECHNICAL FIELD The present invention relates to a white balance adjusting device in an electronic camera.

b. 2. Description of the Related Art In electronic cameras, white balance is adjusted according to changes in the color temperature of a light source in order to perform good color reproduction in electronic cameras. The adjusting means is roughly classified into a manual method and an automatic tracking method. The manual method is provided with a white balance preset switch that is set in advance so that white balance can be achieved for light sources of several color temperatures, and the white balance is preset by switching this switch. The method is to provide a sensor for detecting a color temperature, constantly detect a change in color temperature of a light source, and directly control a gain of a variable gain amplifier for white balance adjustment corresponding to the change to adjust white balance.

On the other hand, as an electronic camera, a multi-mode electronic camera having a combination of an electronic still mode, a video camera mode, and a mode for recording one screen while looking at a monitor (hereinafter referred to as 1 shot video camera mode) has been proposed. The electronic camera of this type is required to have maneuverability and quick-shooting ability especially when it has an electronic still camera mode. Therefore, it is considered that the automatic tracking white balance adjustment is suitable. An example of a conventional electronic camera that performs such an automatic tracking white balance adjustment is shown in FIG. In FIG. 3, 1 is a white filter, 2R, 2G and 2B are color sensors, 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, and 8 is system control. Circuit, 9 is a synchronizing signal generating circuit, 10 is a release pulse input terminal, 11 is a mode switching signal input terminal, 12
Is a composite color television signal output terminal. The light that has passed through the white filter 1 is incident on the sensors 2R, 2G, and 2B that have red, green, and blue sensitivities, respectively.
It is input as a signal to the white balance control circuit 3 via G and 2B. This white balance control circuit 3
The white balance control signal is output to control the gain of the variable gain amplifier for white balance adjustment in the image pickup signal processing circuit 6 to adjust the white balance.
Then, when a release pulse is input to the release pulse input terminal 10 while the electronic still camera mode signal is input to the mode switching signal input terminal 11, the shutter drive pulse from the system control circuit 8 opens and closes the shutter 4. The image pickup device 5 operates and the image pickup output signal is inputted from the image pickup device 5 to the image pickup signal processing circuit 6. Further, in the state where the video camera mode signal or the 1 shot video camera mode signal is input to the mode switching signal input terminal 11, the shutter 4 is maintained in the open state regardless of the presence or absence of the release pulse, and the image sensor 5 is continuously operated. The image pickup output signal is input to the image pickup signal processing circuit 6. The image pickup output signal is separated into red (R), green (G) and blue (B) component signals in the image pickup signal processing circuit 6 and then input to the white balance adjustment variable gain amplifier. Is adjusted, input to the encoder 7, and output from the output terminal 12 as a composite color television signal. In such an electronic camera that performs white balance adjustment by the conventional automatic tracking method or manual method, the gain of the variable gain amplifier for white balance adjustment is controlled in an open loop, and the adjustment state of the white balance is fed back to the control device. Because it is not
In particular, in the electronic still camera mode in which the output signal from the image sensor is not obtained until the shutter is completely opened / closed after the release switch is turned on, the white balance adjustment state cannot be evaluated, and a nonlinear gain control characteristic is generally used. Since the control of the variable gain amplifier for white balance adjustment is incomplete, proper white balance adjustment becomes difficult, and the problem of white balance adjustment often occurs only after viewing a reproduced image after imaging.

C. The present invention has been made in view of the above points, and it is possible to evaluate the white balance adjustment state in all imaging / recording modes at all times, and thereby to achieve a highly accurate white balance adjustment of an electronic camera. An object is to provide a white balance adjusting device.

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

In FIG. 1, color sensors 2R, 2G, and 2B having red, green, and blue sensitivities are arranged at the positions where the light passing through the white filter 1 strikes.
G and 2B are connected to the pseudo imaging signal generation circuit 13. The output of the pseudo imaging signal generation circuit 13 is the switching circuit 1
It is connected via 4 to an image pickup signal processing circuit 6 having a variable gain amplifier for white balance adjustment. On the other hand, an image pickup device 5 is arranged at a position where the light passing through the shutter 4 strikes, and the output of the image pickup device 5 is connected to the image pickup signal processing circuit 6 via a switching circuit 14. The output of the image pickup signal processing circuit 6 is connected to the encoder 7 and the white balance error detection circuit 15, respectively, and the output of the white balance error detection circuit 15 is input to the white balance control circuit 3 and the white balance control circuit. The output of 3 is fed back to the imaging signal processing circuit 6 via the storage circuit 16. The output of the system control circuit 8 which receives signals from the synchronization signal generation circuit 9, the release pulse input terminal 10 and the mode switching signal input terminal 11 is the shutter 4, the image sensor 5, the imaging signal processing circuit 6, and the pseudo imaging. It is input to the signal generation circuit 13, the switching circuit 14, and the storage circuit 16, respectively. The pseudo image pickup signal generation circuit 13 uses the pseudo image pickup signal generation pulse from the system control circuit 8 to generate the color centers 2R and 2R having the same spectral sensitivity characteristics as the image pickup element 5 at the same timing as the (imaging element) drive pulse.
The outputs of G and 2B are sampled, and the pseudo imaging elephant equivalent to the output from the image sensor 5 is generated. This pseudo image pickup signal is equivalent to the output signal of the image pickup element 5 when picking up an image of a monochrome object.

e. Operation of Embodiment Next, the operation of the embodiment of the present invention having the above-described configuration will be described.

(I) In case of electronic still camera mode With the electronic still camera mode signal being input to the mode switching signal input terminal 11, the shutter 4 is closed without the release pulse input from the release pulse input terminal 10. At this time, the image pickup output signal from the image pickup device 5 is not obtained, but since the light is always incident on the color sensors 2R, 2G, 2B, the pseudo image pickup signal from the pseudo image pickup signal generation circuit 13 is output from the shutter 4. Can always be obtained regardless of movement. Therefore, until the release pulse is input, the changeover circuit 14 is set by the changeover switch control pulse from the system control circuit 8, and the pseudo image pickup signal output from the pseudo image pickup signal generation circuit 13 is output to the image pickup signal processing circuit 6. Enter in. The pseudo image pickup signal generation circuit 1
It is assumed that the pseudo imaging signal generation pulse for activating 3 is output in synchronization with the turning on of a main power source (not shown), and is continuously output while the main power source is turned on. The image pickup signal processing circuit 6 separates the pseudo image pickup signal into R, G, and B components in accordance with the signal processing pulse from the system control circuit 8, passes through the variable gain amplifiers respectively, and then detects a white balance adjustment error. It is output as an RGB output signal to the white balance error detection circuit 15. The white balance control circuit 3 receives the white balance error signal from the white balance error detection circuit 15 and processes the image pickup signal so that the error is eliminated, that is, the R, G, and B components are equal in magnitude. A white balance control signal for controlling the variable gain amplifier in the circuit 6 is output. At this time,
Since the storage circuit control pulse is not output from the system control circuit 8, the storage circuit 16 does not operate, and the white balance control signal is input to the image pickup signal processing circuit 6 as it is.

When a release pulse is input from the release pulse input terminal 10, the system control circuit 8 outputs a shutter drive pulse, an image sensor drive pulse, and a memory circuit control pulse to the shutter 4, the image sensor 5, and the memory circuit 16, respectively.
The memory circuit 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 the changeover switch control pulse from the system control circuit 8 to connect the output of the image pickup device 5 to the image pickup signal processing circuit 6. Therefore, the image pickup signal obtained from the image pickup device 5 after the shutter 4 has completed the opening / closing operation is properly adjusted in white balance by the image pickup signal processing circuit 6 which has already been subjected to white balance control, and is passed through the encoder 7. It is output from the composite color television signal output terminal 12.

(II) In case of video camera mode or 1 shot video camera mode When the signal of video camera mode or 1 shot video camera mode is input to the mode switching signal input terminal 11, the shutter 4 is activated regardless of the presence or absence of the release pulse.
Is kept open, the image pickup device 5 continuously outputs an image pickup signal in accordance with the image pickup device drive pulse. Therefore, it is usually sufficient to input the image pickup output signal to the image pickup signal processing 6 through the switching circuit 14, but even in this type of mode, since the image pickup signal is not output during the vertical blanking period, the system control circuit during this period. 8 outputs a changeover switch control pulse to operate the changeover circuit 14,
The pseudo image pickup signal is input to the image pickup signal processing circuit 6, white balance adjustment is performed as in the case of the electronic still camera mode described above, and the storage circuit 16 is operated immediately before the vertical blanking period ends, and the next one field is set. Alternatively, while reading one frame, the white balance adjustment state at that time is held. Therefore, since the switching circuit 14 performs the switching operation once in the vertical blanking period for each field or frame, the white balance adjustment is performed for each screen.

Here, the pseudo image pickup signal output from the pseudo image pickup signal generation circuit 13 will be described. In the above embodiment, the image pickup device 5 is arranged between the G filters arranged in a checkered pattern, for example.
In the case of a charge-coupled device (CCD) in which color filters are arranged according to a so-called Bayer arrangement in which R filters are arranged every other row and B filters are arranged between the rows, the second pulse is added to the image pickup element drive pulse shown in FIG. The line identification pulse and the image pickup element (horizontal) drive pulse shown in FIG. Then, the image sensor 5 discriminates whether the GB line is the RG line by the line discriminating pulse, sequentially reads out one pixel at a time in the order GBGB ... Or RGRG ... by the image sensor (horizontal) drive pulse, and outputs it as an image output signal. There is.
On the other hand, the pseudo image pickup signal is continuously output from the system control circuit 8 at the same timing as the image pickup element (horizontal) drive pulse, and the pseudo image pickup signal is generated in accordance with the pseudo image pickup signal generation pulse including the information of the line identification pulse. The generation circuit 13 appropriately reads the outputs of the color sensors 2R, 2G, 2B and outputs them. Color sensor 2R, 2
Since the outputs of G and 2B are R, G and B one by one, that is, only for one pixel, the pseudo imaging signal generating circuit 13 outputs the outputs of the color sensors 2R, 2G and 2B as shown in FIG. 2 (b). G
By repeatedly reading out in the same order as the B line or the RG line, it is possible to output the pseudo imaging signal as described above. Although the above embodiment is premised on a multi-mode electronic camera, the white balance control device of the present invention is very effective when used individually for an electronic still camera, a video camera and a 1-shot video camera.

f. Effects As described above, according to the present invention, in the electronic still camera mode or the electronic still camera in the multi-mode electronic camera, it is possible to evaluate the white balance adjustment state, which has been impossible in the past. The balance can be adjusted. In addition, in the multi-mode electronic camera, the white balance is adjusted immediately before shooting one screen (one field or one frame) and signal processing in all imaging and recording modes, so that it is quick even if the color temperature of the light source changes. It is possible not only to make the electronic camera excellent in maneuverability, quick-shooting property and color reproducibility with less adjustment error due to time delay, but by operating the switching circuit at an appropriate timing, Since the same white balance adjustment device can be used in all imaging / recording modes, the system can be effectively used.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIGS. 2 (a) and 2 (b) are diagrams for explaining a pseudo imaging signal according to the present invention, and FIG. 3 is a block diagram of a conventional example. is there. 3: White balance control circuit 5: Image sensor, 6: Image signal processing circuit 8: System control circuit 13: Pseudo image signal generation circuit, 14: Switching circuit 15: White balance error detection circuit 16: Storage circuit

Claims (1)

[Claims] 1. An electronic camera having at least a first photographing mode in which a shutter is opened and closed for photographing in response to a release signal and a second photographing mode in which photographing is performed with a shutter always open, Pseudo image pickup signal generating circuit that outputs a signal equivalent to the image pickup output signal from the image pickup device, and a switch for connecting to the image pickup signal processing circuit by switching either the output of the image pickup device or the output of the pseudo image pickup signal generation circuit. Circuit, a white balance error detection circuit that detects a white balance adjustment error from the output of the imaging signal processing circuit, and an output of the white balance error detection circuit, and outputs a white balance control signal to the imaging signal processing circuit. White balance control circuit for controlling white balance adjustment by the white balance control circuit, the white balance control circuit and the imaging signal processing A storage circuit interposed between the circuits and capable of holding a white balance control signal; and a system control circuit for controlling the operation timing of the storage circuit and the switching circuit, wherein the system control circuit is the first shooting mode. Is selected, the white balance control signal is stored and held in the storage circuit in response to the input of the release signal, and the switching circuit is operated to connect the image pickup device and the image pickup signal processing circuit. However, when the second shooting mode is selected, the switching circuit, the pseudo imaging signal generating circuit, and the imaging signal processing circuit are connected only during the vertical blanking period, and immediately before the end of the vertical blanking period. A white balance adjustment device for an electronic camera, wherein the storage circuit stores and holds a white balance control signal.