JPH02131085A - Electronic still camera - Google Patents

Abstract

PURPOSE:To attain proper exposure setting even in the case of back light or spot light by detecting a difference of brightness between a middle part and a circumferential part of an object picture based on an electric signal from a solid-state image pickup device and correcting brightness information when the brightness difference is a prescribed level or over so as to apply exposure control. CONSTITUTION:A level detection section 28 detects the brightness distribution of a pickup pattern and sends a brightness distribution signal to a CPU 22. Then the CPU 22 compares signals of the 1st photometry section 32 with that of the 2nd photometry section 34 and when the brightness of the 1st photometry section 32 is larger than the brightness of the 2nd photometry section 34 by an EV value 3 or over, a photometry signal from a photodetection section 20 is corrected larger than an actual value and when the brightness of the 1st photometry section 32 is smaller than the brightness of the 2nd photometry section 34 by an EV value 3 or over conversely, the photometry signal from the photodetection section 20 is corrected smaller than an actual value. When the absolute value of the difference of the brightness between the 1st photometry section 32 and the 2nd photometry section 34 is less than EV value 3, non correction is applied to the photometry information from the photodetection section 20.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronic still camera with an automatic exposure control mechanism, and more particularly to an electronic still camera that can prevent inappropriate exposure caused by backlight or spot light. It is related to.

[Conventional technology]

In recent years, electronic still cameras that can electronically capture images without using film have become popular. This electronic still camera converts an optical image into an electrical signal by using a solid-state imaging device such as a CCD,
This electrical signal is further subjected to signal processing and recorded as a video signal on a recording medium such as a still video floppy disk.

For example, as described in Japanese Patent Application Laid-Open No. 57-83971, such electronic still cameras can measure light in a narrow range of the photographic screen by spot metering, and can measure the brightness of the subject itself. There are devices that allow reliable photometry.

Furthermore, as described in Japanese Patent Application Laid-Open No. 63-161980, the solid-state imaging device itself also functions as a photometer, measuring multiple locations within the photographic screen, thereby eliminating the need for additional photometering means. There are devices that allow you to perform photometry.

[Problem to be solved by the invention]

However, in the method described in the above-mentioned Japanese Patent Application Laid-Open No. 57-83971, although the main subject at the center of the shooting screen is given an appropriate exposure, the brightness of the surrounding background is ignored, resulting in poor background depiction. There is a hatchling point. In addition, in the latter publication, brightness information is obtained from multiple locations on the shooting screen, but when there is a large difference in brightness depending on the metering range, such as in a backlit scene, the exposure for the main subject may be set to an appropriate value. The disadvantage is that it easily comes off.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to provide an electronic still camera capable of setting appropriate exposure even in the case of backlight or spot light.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a detection means for detecting a brightness difference between a central part and a peripheral part of a subject image based on an electric signal from a solid-state imaging device; At certain times, the exposure control means corrects the luminance information from the photometry means and performs exposure control.

[Effect]

Since the present invention is configured as described above, it is possible to reliably detect a backlit scene or a spot light condition from the brightness difference between the subject and its surroundings. Furthermore, based on this detection result, it is possible to accurately correct the brightness information of the photometric means, and to obtain appropriate exposure information.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of the configuration of an electronic still camera according to this embodiment, and FIG. 2 shows the position of a subject 12 within a photographic screen 10.

In the figure, light from a subject 10 is collected by a photographic lens 14, passes through an aperture 16 in an open state, and enters a solid-state image sensor (hereinafter abbreviated as rCCD) 18. On the other hand, light from a wide range around the subject 12 is transmitted to the light receiving section 2.
0, and the light receiving unit 20 photoelectrically converts the received light and sends it to a central processing unit (hereinafter abbreviated as rCPU) 22 as a photometric signal. Note that the light receiving section 20 is constituted by a light receiving element such as a photodiode, for example.

The CCD 1B is driven and controlled by a CCD drive circuit 24, photoelectrically converts incident light for each pixel, and sends the signal to a level detection section 28 during exposure control, and supplies it to an image processing section 26 during imaging. ing.

When the processing command signal from the CPU 22 is input, the level detection section 28 detects the luminance distribution within the image capture screen from the signal from the CCD 1B, and supplies this luminance distribution signal to the CPU 22.

The CPU 22 uses this brightness distribution signal to determine the first photometry section 32 on the subject 12 and the subject 1.2 as shown in FIG.
The luminance of the surrounding second photometric unit 34 is compared, and the difference in luminance between them is calculated. Then, when the photometry signal from the first photometry section 32 is greater than the signal from the second photometry section by an EV value of 3 or more, that is, when the subject 12 is brighter than its surroundings by an EV value of 3 or more, it is determined that the spotlight is illuminated. And conversely, E
If the V value is 3 or more and it is dark, it is determined that the situation is backlit. In the case of a backlight condition or a spot light condition, the photometric value from the light receiving section 20 is corrected according to the difference.

In addition to the above-mentioned functions, the CPU 22 also has a function to collectively control each of the above-mentioned parts, and is activated by a signal from the release switch 36 and sends a signal to the CCD drive circuit 24 to control the COD. It drives, controls the image processing section 26 and the image recording section 30, and further controls the AE control section 38 based on the correction value.

On the other hand, the image processing section 26 forms an image based on the image signal from C0D1B in response to a processing command signal from the CPU 22, and supplies a recording signal to the image recording section 30. The image recording section 30 records the image information output from the image processing section 26 onto a magnetic recording medium or the like.

Note that the aperture device 40 is controlled by the AE control section 38, and
The aperture 16 is driven to open and close.

Next, the operation and effect of the embodiment configured as described above will be explained along the flowchart of FIG. 3.

First, when the power is turned on, the CPU 22 starts up, and when the release switch 36 is pressed halfway, the light receiving section 20 receives external light, and the CCD drive circuit drives the CCD 18 to photoelectrically convert the incident light. and sends the signal to the level detection section 28.

Next, the level detection unit 28 detects the brightness distribution of the image capture screen, and sends a brightness distribution signal to the CPU 22.

Then, in the CPU 22, the first photometry section 32 and the second photometry section 3
4, and if the brightness of the first photometer 32 is higher than the brightness of the second photometer 34 by EV value 3 or more, that is, when the subject I2 is illuminated with a spotlight,
The photometry signal from the light receiving section 20 is corrected to be larger than the actual value, and conversely, when the luminance of the first photometry section 32 is lower than the luminance of the second photometry section 34 by an EV value of 3 or more, that is, when the subject 12 is backlit. Sometimes, the photometric signal from the light receiving section 20 is corrected to a smaller value.

On the other hand, if the absolute value of the brightness difference between the first photometric section 32 and the second photometric section 34 is the EV value 3 or less, the photometric information from the light receiving section 20 is not corrected at all.

Determine the appropriate exposure based on the photometric values as above, and
Based on this exposure data, the E control section 38 controls the CCD drive circuit 24 to adjust the drive time of the CCD 18, and also controls the aperture drive section 40 to adjust the aperture 16.

Next, when the release switch 36 is further pressed in this state, the light transmitted through the photographing lens 14 passes through the aperture of the diaphragm 16 and forms an image on the CCD 18.

Then, according to a processing command signal from the CPU 22, the image processing section 26 forms an image from the image signal of C0D1B,
The image recording section 30 records this image information on a magnetic disk or the like.

〔Effect of the invention〕

4. As explained above, in the present invention, the solid-state imaging device that captures the subject image is also used as a means for detecting unique illumination conditions such as backlighting and spot illumination, and thereby the external light type photometry means is used. The photometric value detected by the camera is corrected. Therefore, even when setting the exposure based on the photometric value from the external light metering means, it is possible to achieve the function of preventing extreme overexposure and underexposure.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining the operation of the embodiment. FIG. 3 is a flowchart for explaining the operation of the embodiment. 22 . . . CPU 32...First photometry section 34...Second photometry section. 12...Subject 18...CCD 20...Light receiving section 28...Level detection section 12 (cane photographing object) To: EV=3

Claims (1)

[Claims] (1) In an electronic still camera equipped with a photometer that measures subject brightness using an external light method and a solid-state imaging device that converts an optically formed subject image into an electrical signal, electricity from the solid-state imaging device is provided. A detection means for detecting a brightness difference between a central part and a peripheral part of a subject image based on the signal, and when the brightness difference is equal to or higher than a predetermined level, the brightness information from the photometry means is corrected to perform exposure control. An electronic still camera characterized by comprising: exposure control means.