JPH02100471A - Electronic camera - Google Patents

Abstract

PURPOSE:To set the best exposure state by measuring the light of a subject with an analog video signal read out of picture elements in a specific range. CONSTITUTION:When a shutter release button is pressed, a switching means 15 is switched to a contact (b) and a driving circuit 20 generate a driving signal for scanning only plural picture elements in the center area of an image sensor 13 vertically and horizontally. Then an exposure quantity detecting circuit 14 detects the mean value or peak value of the analog video signal read out of the center area and supplies it to a shutter control circuit 19 through an A/D converter 16 to set the operation timing of a mechanical shutter 12 for the best exposure quantity, thereby taking a picture. Thus, the best exposure state can be set and the accuracy of digital signal processing is improved by the shutter control means 19.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention captures an image with a color image sensor having a photoelectric conversion function, and converts the video signal generated by the imaging into a digital signal and records it. Regarding electronic cameras.

[Conventional technology]

Conventionally, as such an electronic camera, Japanese Patent Application Laid-Open No. 60-43
There is one shown in No. 978. As shown in FIG. 3, this electronic camera has an optical system 1 that forms an optical image of a subject.
, a color image sensor (solid-state image sensor) 2 is placed behind the optical system 1 and photoelectrically converts the optical image and outputs an analog video signal for each pixel, and the analog video signal is output from the driver circuit 3. It is read out by horizontally and vertically scanning the color image sensor 2 in synchronization with the drive signal. The analog video signal read out by this scanning is converted into a digital signal by the A/D converter 4, and is stored in the semiconductor memory 5 in synchronization with the address signal at a predetermined timing output from the driver circuit 6 and in correspondence with the pixel arrangement. It looks like this. In addition, in this invention, an electronic viewfinder function is provided by supplying a video signal to an electronic viewfinder 9 via a D/A converter 7 and a switching circuit 8, and outdoor photography with batch 'J-10 is made possible. ing.

[Problem to be solved by the invention]

In such an electronic camera, it is necessary to set the optimum exposure state using a shutter or aperture (not shown) in the optical system 1. In particular, if a photograph is taken with an exposure amount that deviates from the optimum state, the image may become distorted. This may cause problems such as the inability to record good video due to limitations in the dynamic range of the sensor 2 and the signal processing system connected to it.
It is desired to develop a more precise exposure control means.

[Means for solving the problems] The present invention has been made in view of the above problems,
It is an object of the present invention to provide an electronic camera having a simple structure and having a highly accurate exposure control means.

In order to achieve this object, the present invention provides an exposure amount detection means that performs photometry of a subject using analog signals read out from pixels in a specific range among analog video signals read out from an image sensor; At times, the detection signal of the exposure amount detection means is sent to an A/D converter, and when shooting, the image signal is sent to an A/D converter.
A switching means for switching and transmitting the analog video signal read out by the sensor to a BA/D converter, and a mechanical shutter or an electronic system using the image sensor itself based on the output signal from the A/D converter during photometry. By providing a shutter control means for setting the optimum shutter speed of the shutter, the camera is configured to perform shooting under optimum exposure conditions at the time of shooting.

[Effect]

In the present invention having such a configuration, an optimum exposure state can be set by the photometry means and the shutter control means, and accuracy can be improved by digital signal processing in the shutter control means. Furthermore, since the image sensor for photographing is also used for photometry, there is no need for a separate photoelectric conversion element for photometry, and the output signal of the image sensor and the output signal of the exposure amount detection means are connected to the same A/ Since the signal is converted into a digital signal by a D converter, the configuration can be made small and simple.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. First, to explain the configuration, in the figure, a mechanical shutter 12 and a CC
A color image sensor 13 consisting of D, etc. is arranged in sequence, and an optical image of a subject incident through the optical system 11 passes through a mechanical shutter 12 and is sent to the color image sensor 1.
It is designed to form an image on 3.

Reference numeral 14 denotes an exposure amount detection circuit, which detects the light intensity of the optical image of the subject by detecting the average value or peak value of the analog video signal read out from the color image sensor 13.

Reference numeral 15 denotes a switching means consisting of an analog switch, etc., in which the analog video signal read from the color image sensor 13 is connected to the switching contact a, and the exposure amount detection circuit 1
The detection signal detected at step 4 is applied to each of the switching contacts a and b, and one of the signals is transferred to the A/D converter 16 by switching between the switching contacts a and b.

Reference numeral 17 denotes a video signal processing circuit, which performs so-called γ correction and white balance adjustment on the digital video signal output from the A/D converter 16, separates the luminance signal and color difference signal, and generates a readable and writable random signal. Access memory (RAM)
) is stored in a built-in card-type memory device 18.

The output terminal of the A/D converter 16 is connected to the shutter control circuit 19.
The shutter control circuit 19 is also connected to the A/D converter 1.
A shutter speed for setting the optimum exposure amount is set in the mechanical shutter 12 according to the digital detection signal outputted from the shutter 6. That is, the mechanical shutter 12 does not operate at the set speed due to mechanical factors such as collisions between shutter blades, so the mechanical shutter 12 does not operate at the set speed. Control is performed to automatically adjust the actuation timing of the shutter 12.

Reference numeral 20 denotes a drive circuit that generates a drive signal for outputting the video signal generated in each pixel of the image sensor 13 by so-called vertical and horizontal scanning readout. The drive circuit 20 generates a drive signal that vertically and horizontally scans only the plurality of pixels distributed in the central area of the color image sensor 13 during photometry, thereby reading out only the signal charges in this area, and reads out all the signal charges during photography. It has a function of outputting two types of drive signals for scanning pixels.

21 is a central control circuit incorporating a micro combinator, etc., and controls the switching operation of the switching means 15, the processing operation of the video signal processing circuit 17, the writing operation of the memory device 18, the operation of the shutter control circuit 19, and the driving of the drive circuit 20. Centrally control each operation timing.

Next, the operation of this embodiment will be explained. First, when a shutter release button (not shown) is pressed after setting the shutter speed, the switching means 15 switches to the switching contact side, and the exposure amount detection circuit 14 is activated.

At the same time, the drive circuit 20 connects the color image sensor 13
By generating drive signals that vertically and horizontally scan only a plurality of pixels distributed in the central region of the area, only the signal charges in the area are read out. The exposure amount detection circuit 14 detects the average value or peak signal of the analog video signal read out from the central area, outputs these detection signals to the switching contact C, and outputs these detection signals to the A/D via the contact C of the switching means 16. converter 16
supply to

The A/D converter 16 converts it into a digital detection signal and supplies it to the shutter control circuit 19.
corrects the operation timing of the mechanical shutter 12 so that the exposure amount corresponds to the set shutter speed.

Next, the mechanical shutter 12 performs a shutter operation at a shutter speed that includes the correction value to take a photograph.

Next, the switching means 15 switches to the switching contact a side, and the signal charge generated in each pixel of the image sensor 13 by this photographing is read out in synchronization with the drive signal from the drive circuit 20, thereby producing a video signal. is transmitted to the A/D converter 16 via switching contacts a-c. A/
The D converter 16 converts the video signal into a digital signal and supplies it to the video signal processing circuit 17, and the video signal processing circuit F forms a luminance signal and a color difference signal of the NTSC system through digital arithmetic processing and stores them in the memory device 18. let

In this way, this embodiment can set the optimum exposure condition by correcting the shutter operation timing caused by the mechanical structure of the mechanical shutter 12, and furthermore, by providing the switching means 15, one A/
Since the D converter 16 enables two different signal processing systems, the structure can be simplified. Furthermore, since the image sensor 13 for imaging is used as a photometric sensor, a separate photometric sensor is not required. Furthermore, the image
Since photometric processing is performed based on the signal charges of some pixels distributed in the central region of the sensor 13, rapid detection can be performed.

Next, another embodiment will be described with reference to FIG. In this figure, the same or corresponding parts as in FIG. 1 are indicated by the same reference numerals.

This embodiment relates to an electronic camera in which the image sensor 13 itself performs a shutter operation.

That is, this image sensor 13 is composed of an interline transfer type charge storage device (CCD), and has a period during which signal charges generated in a group of light receiving elements constituting a pixel are transferred to a vertical transfer path (i.e., a light receiving period). The actual shutter operation is performed by controlling the shutter.

Therefore, during photometry, the drive circuit 20 generates a drive signal that vertically and horizontally scans only the plurality of pixels distributed in the central area of the color image sensor 13, reads only the signal charge in the area, and performs exposure detection. circuit 1
4 detects the average value or peak signal of the analog video signal read out from the central area, outputs these detection signals to the switching contact, and sends them to the A/D converter 16 via the contact C of the switching means 16. The A/D converter 16 converts it into a digital detection signal and supplies it to the shutter control circuit 19, and the shutter control circuit 19 adjusts the shutter operation timing to obtain the optimum exposure amount corresponding to the set shutter speed. The correction value is instructed to the drive circuit 20.

Then, the drive circuit 20 controls the light receiving period of each pixel of the color image sensor according to the correction value at the time of photographing, simultaneously performs vertical and horizontal readout scanning of the signal charge, and switches the readout analog video signal. Means 15
The signal is supplied to the A/D converter 16 through contacts a-c, and then converted into a digital signal and stored in the memory device 18.

In the above two embodiments, a circuit configuration in which one A/D converter is used for digital conversion of the video signal and the photometric detection signal is shown, but the digital detection signal to the shutter control circuit is used for aperture adjustment. It may also be applied to signals.

Further, although the case where a memory device containing a semiconductor memory is used as a recording medium has been described, the present invention can also be applied to an electronic camera using a magnetic recording medium.

〔Effect of the invention〕

As explained above, according to the present invention, an image sensor that receives an optical image of a subject and outputs an analog video signal for each pixel.
In an electronic camera having a sensor and an A/D converter that converts the analog video signal into a digital signal, reading out from pixels in a specific range of the analog video signal read out from the image sensor during photometry an exposure amount detection means that performs photometry of the subject using the analog video signal obtained by the camera;
a switching means for switching and transmitting an analog video signal read from the image sensor to the A/D converter during photographing, and a mechanical switch based on the output signal from the A/D converter during photometry. Since the shutter control means is provided to set the shutter speed of the electronic shutter by the shutter or the image sensor itself, it is possible to set the optimum exposure state, and to improve the accuracy by digital signal processing in the shutter control means. Can be done. Furthermore, since the output signal of the image sensor and the output signal of the photometric element are generated by the same A/D converter, the configuration can be made compact and simple.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention; FIG. 2 is a block diagram of another embodiment; FIG. 3 is a block diagram of a conventional example. Third factor Mechanical shutter Color image sensor Exposure detection circuit Switching means A/D converter Video signal processing circuit Memory device Shutter control circuit Drive circuit Central control circuit

Claims (1)

[Scope of Claims] An electronic camera having an image sensor that receives an optical image of a subject and outputs an analog video signal for each pixel, and an A/D converter that converts the analog video signal into a digital signal, comprising: exposure amount detection means that performs photometry of a subject using analog video signals read out from pixels in a specific range among the analog video signals read out from the image sensor; a switching means for switching and transmitting a signal to the A/D converter, and an analog video signal read from the image sensor during photography to the A/D converter; and an output from the A/D converter during photometry; Based on the signal, the mechanical shutter or the image
An electronic camera characterized by comprising a shutter control means for setting the shutter speed of an electronic shutter by the sensor itself.