JPH03154588A - Camera - Google Patents

Abstract

PURPOSE:To make unbalanced color not eminent in a picked-up video image by decreasing gain of a signal relating to a color when an object is picked up at a comparatively dark place without use of a strobe light. CONSTITUTION:A controller 10 controls the gain of gain changeover circuits 29, 30 so as to switch it from a standard value to a lower value in the strobe-off mode in which a measured brightness of a photometry element 23 is prescribed value or below and a strobe 41 is not in operation. Thus, when the brightness of an object is comparatively low, the rate of a color signal in the picked-up video image is decreased, the unbalanced color balance is not made remarkable and since a signal representing the brightness is not subjected to gain switching, the picture quality of the video image is almost unchanged.

Description

[Detailed Description of the Invention] Summary of the Invention In a camera in which the adjustment position in the white balance adjustment circuit is fixed at a position suitable for daylight and strobe photography, the strobe is not used in a relatively dark place (for example, indoors). When taking pictures, lower the gain of the signal related to one color in order to make the imbalance in white as less noticeable as possible.

BACKGROUND OF THE INVENTION The present invention relates to a camera (including a removable one) equipped with a strobe device.

In a camera equipped with a solid-state electronic imaging device that outputs a video signal representing a captured image of a subject, it is necessary to adjust the color balance of the video signal (color signal). On the other hand, in some cameras with a built-in strobe device, the color sensor is omitted in order to reduce the size of the camera, and the one-color balance adjustment position is fixed at a position suitable for both daylight and strobe photography. As a result, when shooting indoors (mainly under fluorescent or electric bulb lighting) without using a strobe device, the color balance will be disrupted, and the captured image will not accurately represent the actual color tones of the subject. The question arises that the possibility is high.

Summary of the Invention This invention provides a camera with a fixed one-color balance adjustment position, which improves the accuracy of images shot with a relatively simple configuration even when shooting in a relatively dark place such as indoors without using a strobe. The purpose is to make the change in color balance as inconspicuous as possible.

The present invention provides a camera equipped with a processing circuit that separates a video signal output from a solid-state electronic imaging device into a signal representing brightness and a signal related to color, and a strobe light emitting device, in which a single color photometric element is used to measure the brightness of a subject. a gain switching circuit that switches the gain of the signal between a standard value and a reduced value; and a gain switching circuit that switches the gain of the signal between a standard value and a reduced value, and The present invention is characterized by comprising means for controlling switching from a standard value to a reduced value.

According to this invention, in the strobe off mode in which no strobe device is used, when the brightness of the subject is relatively low, the gain of the gain switching circuit for the signal related to one color is switched from the standard value to the reduced value, so two shots are taken. The ratio of color signals in the captured video is reduced, and the imbalance in one color becomes less noticeable. Since the gain is not switched for the signal representing brightness, the image quality of the video hardly changes.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which the present invention is applied to a still video camera (electronic still camera) will be described in detail.

FIG. 1 shows part of the electrical configuration of a still video camera.

The overall operation of the still/video φ camera is controlled by the control device IO.
supervised by. This control device IO is composed of a CPU, memory, interface, etc.

The imaging optical system 20 includes an imaging lens system 21. for forming a subject image. It is composed of an aperture 22 and a shutter (not shown; the shutter can also be implemented as an electronic shutter). A photometric element 23 for measuring the brightness of incident light is disposed within the imaging optical system 20, and a signal representing the measured brightness is input to the control device 10. Aperture 22
is controlled by the control device 101; The aperture 22 may be manually settable.

A solid-state imaging device 24 such as a COD is arranged on the focal plane of the optical system 20, and this device outputs color signals of three primary colors, R (red), G (green), and B (blue) representing the subject image. do. In the electronic shutter system, the signal charge accumulation time of the solid-state imaging device 24 is controlled by the control device 10. The image data of the subject imaged on the imaging device 24 is read out as a three-color video signal in synchronization with a synchronization signal given by the control device 1G, and is read out as a three-color video signal by a preamplifier circuit (not shown) and a first variable gain amplification circuit. Circuit (color balance adjustment circuit') 25, 28, and 27 are inputted to the process matrix circuit 28, respectively.

Among the variable gain amplification circuits 25 to 27, the variable gain amplification circuit 25 to which the color signal R is input and the variable gain amplification circuit 27 to which the color signal B is input are given a control signal from the electronic volume circuit 14. Based on the signal, the gain adjustment of each signal is performed by two-stage switching as described later.

Color signals R and G input in the process matrix circuit 28
, B to generate a luminance signal Y and two color difference signals R-Y,
B-Y is created.

The created color difference signals R-Y and B-Y pass through second variable gain amplifier circuits 29 and 30, and the luminance signal Y is directly input to a recording signal processing circuit 31, respectively. Color difference signal R
A control signal from the control device 10 is given to the second variable gain amplification circuit 29 to which -Y is input and the second variable gain amplification circuit 30 to which the color difference signal B-Y is input, and based on this control signal, The gain adjustment of each color difference signal is 2.
This is done in stages.

That is, when the measured luminance of the 7111 optical element 23 is an EV value of 11 or more, and when performing strobe photography using a strobe light emitting device, the standard value is used as the gain of these variable gain amplifier circuits 29 and 30. It will be done. On the other hand, if the measured luminance is an EV value of 11 or less,
When shooting without using a strobe light emitting device (strobe off mode), the gain of these variable gain amplifier circuits 29 and 30 is set to a value lower than the standard value (this is called a reduction value). . This setting is performed by the control device IO via the D/A conversion circuit 16. −
For example, the reduced value is about 75% of the standard value.

Strobe off mode is when the operator does not set strobe photography using the strobe setting switch 13.
This includes when the strobe 41 is forcibly turned off based on the judgment of the control device 10.

In this way, in the strobe off mode in which no strobe device is used, the circuit 29 adjusts the levels of the one-color difference signals R-Y and B-Y when the subject brightness is relatively low.
．． Since the gain of a(l is switched from the standard value to the reduced value, 1. The proportion of color signals in the captured image is reduced, making the imbalance of one color less noticeable.As for the luminance signal Y, the gain is switched. Since this is not done, the image quality of the video will hardly change.

The recording signal processing circuit 31 includes a line sequential circuit, a pre-emphasis circuit, an FM modulation circuit, and a combination path, and an FM-modulated composite video signal is output from this circuit 31 and sent to a gate circuit 32 for recording control. Sent.

The still/video magnetic disk 34 is driven by the disk motor 3
5 for a constant rotational speed, for example 3800r, p, m.

Rotationally driven. A magnetic head 33 for recording is in contact with this magnetic disk 34, and one phase detection pulse PG is applied to the core of the magnetic head 33 for each rotation of the magnetic disk 34.
A phase detector 37, which generates , is nearby. The magnetic head 33 is transported in the radial direction of the magnetic disk 34 by its transport mechanism and positioned on a predetermined track. The phase detection pulse PG is given to the control device 10.

As mentioned above, for strobe photography, there is a strobe 41, and a charging circuit 43 that stores charge to supply instantaneous driving current for the strobe 41. A strobe switch 42 that applies charging current from a charging circuit 43 to the strobe 41 to cause the strobe 41 to emit light, and a strobe charging switch 44 that supplies voltage from the power source 1 to the charging circuit 43 are provided. The charging circuit 43 includes a circuit that detects that the charging voltage has reached a predetermined value and outputs a charging completion signal. switches 42 and 4
4 is turned on and off by the control device 10. 1st
In the figure, the power supply 1 is commonly used for the strobe light emitting device and other circuits, but a power supply exclusively for the strobe may be provided.

RAM II is connected to the control device IO. FIG. 2 shows part of the contents of RAM II.

Two types of color balance adjustment values are set in RAMII. One of them is for daylight and strobe photography (this is called the first adjustment value), and when the brightness by the Dj optical element 23 is above a predetermined value (for example, an EV value of 11 or more), and when the strobe light emitting device is This is the standard color balance adjustment value. This color balance adjustment value is set in advance using a standard light source, and adjusted to a value corresponding to a color temperature of 5500, for example.

The other is for indoor photography (this is called the second adjustment value)
, the brightness measured by the photometric element 23 is below a predetermined value (for example, EV
11 or less) and is in strobe off mode. As the second adjustment value, for example, a value slightly higher than the first adjustment value (the gain of the variable gain adjustment circuit 25, 27 is slightly increased) is used. If the first adjustment value is 1, this is about 1.1-1.2.

Indoor lighting can be classified in detail into white fluorescent lights, daylight colored fluorescent lights, incandescent lights, etc., but the adjustment settings for indoor photography are the average settings suitable for these lighting lights. Just use it.

The first or second adjustment value is read out by the control device 10 and applied to the electronic volume circuit 14 .

The electronic volume circuit 14 is a D/A conversion circuit 15R115.
B, and outputs a voltage signal (control voltage) according to the input color balance adjustment value.

One D/A conversion circuit 15R is for color signal R, and the other D/A conversion circuit 15B is for color signal B.

A voltage signal output from the electronic volume circuit 14 is used for gain control of the variable gain amplifier circuits 25 and 27.

In this way, you can use strobe off without using a strobe device.
mode, when the subject brightness is relatively low, the color balance adjustment value that determines the gain of the variable gain tank width circuits 25 and 27 for two-color balance adjustment is switched to the one for indoor photography, so there is no need to install a single-color sensor. It is possible to achieve color balance adjustment that is almost suitable for indoor photography, and to obtain an image with little deviation in the balance of one color. Moreover, the number of settings for adjusting the balance of one color is small, and all that is required is switching them.
Since a color sensor is not required, the configuration is simple and the camera can be configured compactly.

Figure 3 shows this still video and camera strobe off.
It shows the processing procedure during shooting in the mode.

At the start of photographing, the distance to the subject is measured by a distance measuring device (illustrated path) (step 51),
The subject brightness is measured by the photometric element 23 (step 61). On the other hand, based on these distance measurement data and brightness data, the aperture value of the aperture 22 is determined, and the shutter speed (exposure time) is determined (step 5).
2.53). On the other hand.

Based on the luminance data obtained by the Al11 light, it is determined whether the measured luminance is less than a predetermined value for gain switching of the variable gain amplifier circuit 29, 30 for color difference signals (step 62), and even if it is less than the predetermined value. If the above reduction value is the amplifier circuit 2
9.30 and its gain is reduced (step 6
3). If the measured luminance is above a predetermined value, the amplifier circuit 29.
The gain of 30 is kept at the standard value.

Also, it is determined whether the constant luminance of 1117 is less than a predetermined value for switching the gain of the color balance adjustment variable gain amplifier circuit 25.27 (step 64), and if it is less than the predetermined value, the RA
Adjustment values for indoor photography (second adjustment values) are read out from the MII, and sent to these amplifier circuits 2 via the electronic volume circuit 14.
5.27 (step 65). If the measured luminance is equal to or greater than the predetermined value, the first adjustment value is selected and maintained in the set state.

Thereafter, if the shutter release button is pressed, exposure processing is performed (step 54), and the resulting video signal is recorded on the magnetic disk 34 (step 55).

In the strobe-on mode, the variable gain amplifier circuit 29
．． The standard value is maintained as the gain of 80, and the first adjustment value is selected as the one-color balance adjustment value.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, and is a block diagram of a two-still video camera, Fig. 2 shows color balance adjustment value data in RAM, and Fig. 3 is a flow chart showing the photographing processing procedure. It is. 29, 30... Variable gain amplifier circuit for color difference signal level adjustment. 41... Strobe. that's all

Claims (1)

[Scope of Claims] A photometric element for measuring subject brightness in a camera equipped with a processing circuit that separates a video signal output from a solid-state electronic imaging device into a signal representing brightness and a signal related to color, and a strobe light emitting device. , a gain switching circuit that switches the gain of the color-related signal between a standard value and a reduced value, and a gain switching circuit that switches the gain of the color-related signal between a standard value and a reduced value, and when the measured brightness of the photometric element is below a predetermined value and the strobe light emitting device is in a strobe off mode in which the strobe light emitting device does not operate. A camera comprising means for controlling gain to switch from a standard value to a reduced value.