JPH02280582A - Automatic exposure controller - Google Patents

Abstract

PURPOSE:To make the size of a camera main body small and to attain proper exposure control by providing an exposure control means and controlling either of an iris means and an exposure time control means in response to a digital signal converted by an A/D conversion means. CONSTITUTION:An output current in response to an incident luminous quantity is added for each picture element of an area sensor 15 to a capacitor CI and supplied to an A/D converter 29. An output from the A/D converter 29 is latched by a latch circuit 30 and the latched digital data is supplied to a control section 19. The control section 19 sets an optimum iris and exposure time in response to the total incident luminous quantity to an area sensor 15. Then the image pickup state by the iris 13 and drivers 17, 18 is set to the optimum exposure. Thus, it is not required to provide a device for exclusive use of photometry, the camera main body is made small in size and accurate photometry exposure control corresponding to the pickup position is attained.

Description

[Detailed description of the invention] [Technical field of the invention]

The present invention relates to an automatic exposure control device for an electronic still camera or video movie camera using a solid-state image sensor such as a CCD.

[Background Art and its Problems] Generally, the exposure setting value in a camera is set according to the amount of light irradiated when taking a photograph. In other words, with conventional manual exposure adjustment cameras, the amount of light irradiated at the shooting location is measured in advance using a photometer separate from the camera, and the exposure value is selected according to the measured amount of irradiation. Adjusted exposure. In recent years, auto-exposure and auto-focus cameras have been frequently used, and these cameras are equipped with a dedicated photometry device for controlling exposure in the camera body. Recently, electronic still cameras, video movie cameras, and the like using solid-state image sensors have been put into practical use, and these electronic cameras are also equipped with a device dedicated to photometry for automatic exposure control. However, in the above automatic exposure control type camera,
Providing a photometry section in the camera body not only hinders miniaturization, but also because the image sensor position and the photometry position are different, resulting in a difference with the actual imaging light amount.
There is a problem in that it is difficult to perform appropriate exposure control. [Purpose of the Invention] The present invention was made in view of the above-mentioned problems, and it is possible to downsize the camera body and perform appropriate exposure control without the need to separately provide a device dedicated to photometry. The purpose of this invention is to provide an automatic exposure control device. [Summary of the Invention] In other words, the automatic exposure control device according to the present invention includes an image sensor for obtaining image data, an aperture means for controlling the amount of light irradiated to the image sensor, and an exposure device for controlling the exposure time of the image sensor. A time control means, an imaging current storage means for storing a current corresponding to the output level of the image sensor, an analog/digital conversion means for obtaining a digital signal corresponding to the amount of current stored by the storage means, and an analog/digital conversion means for obtaining a digital signal corresponding to the amount of current stored by the storage means. The apparatus is configured to include exposure control means for controlling the aperture means and/or the exposure time control means in accordance with the converted digital signal. . Embodiments of the Invention An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an electronic circuit of an automatic exposure control device of the present invention. In the figure, 11 is an optical system block, and this optical system block 11 includes lenses 12m, 12
b and an iris (aperture) 13. This aperture operation by the iris 13 is performed by an iris drive motor 14. An area sensor 15 made of a solid-state image sensor is arranged at an imaging position adjacent to the optical system block 11. Horizontal scanning of this area sensor 15 is performed by an H driver 17, and vertical scanning is performed by a V driver 18. The timing is controlled by a timing generator 16. An iris drive motor control line 20 is connected to the iris drive motor 14, and a timing generator 1 is connected to the iris drive motor control line 20.
A control signal from the control unit 19 is applied to the iris 1 through the shutter speed control line 21, respectively.
The aperture in 3 and the exposure time in area sensor 15 are controlled. On the other hand, the image signal from the area sensor 15 is A/Da
The signal is supplied to the exchange section 22. This A/D converter 22 converts the image signals sequentially given from each pixel of the area sensor 15 into
The image signal is converted into a digital signal according to the signal level, and the image signal obtained by this digital conversion is stored in the image data memory 23. The writing address of the image signal to the image data memory 23 is specified by the control unit 19 in synchronization with the imaging scanning timing of the area sensor 15. The output current corresponding to the amount of incident light for each pixel in the area sensor 15 is given to the DC cut circuit 24 via the transistor TRI, and after its DC component is cut off, it is inverted and amplified via the operational amplifier 25, and is inverted and amplified by the clamp circuit. 2
given to 6. Here, the operational amplifier 25 inverts and amplifies the sensor output signal and sets the maximum signal level corresponding to the self-portrait area to 1.0 Vpp using the variable resistor VRI. Further, the clamp circuit 26 is connected to the area sensor 1.
The variable resistor VR2 is set so that the signal level of the sensor signal sent from 5, other than the effective output level, becomes the "+VDD" level in synchronization with the pulse timing of the clamp pulse CP.
The sensor signal clamped at the ineffective signal level by the clamp circuit 26 is input to the operational amplifier 28 of the constant current circuit section 27. This constant current circuit section 27 charges the capacitor Ct with the output signal current for one field in the effective area of the sensor signal from the area sensor 15, and the sensor signal current charged in the capacitor CI is vertically It is discharged every time the synchronizing signal VD is applied. In other words, an output current value corresponding to the amount of incident light for each pixel of the area sensor 15 is added to the capacitor CI. Here, the current io flowing through the capacitor CI is determined by the following formula. io = (VDD2-Vin) R1 Then, the current addition value corresponding to the amount of incident light charged by the capacitor CI is given to the A/D converter 29. This A/D
The converter 29 receives a sampling clock AD output from the control unit 19 10 to 20 μs before the vertical synchronization signal VD.
The current value charged in the capacitor CI is converted into a digital value in accordance with CK, and the A/D conversion output from this A/D conversion rA29 is the vertical synchronization signal V.
The signal is latched by the latch circuit 30 in response to a latch timing signal output from the control unit 19 immediately before D. That is, the latch circuit 30 latches digital data corresponding to the amount of light incident on the area sensor 15. The digital data latched by the latch circuit 30 is then given to the control section 19. The control unit 19 includes a data table for setting the aperture and exposure time according to the digital signal latched by the latch circuit 30. In other words, the control unit 19
Now, based on the digital signal latched by the latch DVF 130, the optimum aperture value and exposure time are set according to the amount of light incident on the area sensor 15, and the iris 13 is set.
And the imaging state by each driver 17, 18 is set to the optimum exposure state. Here, the photometric exposure control process in the electronic circuit is executed, for example, when the camera body release switch is pressed halfway. Next, the exposure control operation by the automatic exposure control device having the above configuration will be explained with reference to the timing chart shown in FIG. For example, when the user presses the release switch halfway, the control section 19 outputs an iris control signal and an exposure control signal based on a predetermined exposure setting value, which are applied to the iris drive motor 14 and the timing generator N16, respectively. Here, the iris 13 is set to a predetermined aperture value, the area sensor 15 is set to a predetermined exposure time, and the area sensor 15 outputs an output current signal corresponding to the amount of incident light. When the photometry operation by the area sensor 15 is started, an output current value corresponding to the sum of the amount of incident light in each pixel of the area sensor 15 is determined by the capacitor CI in the constant current circuit section 27.
will be charged. Then, the sensor output current addition value corresponding to the amount of incident light for each pixel of the area sensor 15 charged to the capacitor CI is converted into a digital value by the A/D converter 29 and latched by the latch circuit 30. Then, a digital signal indicating the amount of light incident on the area sensor 15 latched by the latch circuit 30 is output to the control section 19, and the control section 19, based on a data table prepared in advance,
The aperture and exposure time are set according to the digital values, and control signals are output to the iris drive motor 14 and timing generator 16 to obtain the optimum exposure state. That is, when the amount of light incident on the area sensor 15 is less than the appropriate amount, the light amount value is given to the control unit 19 as a digital signal, the aperture for the iris 13 is opened, and the exposure time of the area sensor 15 is delayed. controlled in direction. As a result, the amount of incident light on the area sensor 15 is increased and set to a proper exposure state. On the other hand, if the amount of light incident on the area sensor 15 is larger than the appropriate amount, the light amount value is given to the control unit 19 as a digital signal, the aperture for the iris 13 is closed, and the exposure time of the area sensor 15 is shortened. controlled by. As a result, the amount of light incident on the area sensor 15 is reduced and set to an appropriate exposure state. After the photometric exposure control operation, when the release switch is fully pressed, the image signal from the area sensor 15 in the optimal exposure state is input to the A/D converter 22,
The image data is converted into a digital image signal and stored in the image data memory 23.
is memorized. Therefore, according to the automatic exposure control device configured as described above, the area sensor 15 that performs imaging performs photometry itself, and the aperture and shutter speed of the iris 13 and the area sensor 15 are controlled based on a digital signal corresponding to the amount of photometry. Since the light metering amount is automatically controlled in the section 19 and adjusted so that it is set to the optimal exposure state, there is no need to provide a dedicated device for metering, and not only can the camera body be made smaller, but it can also be placed at the imaging position. It is possible to perform corresponding and accurate photometric exposure control. [Effects of the Invention] As described above, according to the present invention, there is provided an image sensor for obtaining image data, an aperture means for controlling the amount of light irradiated to the image sensor, and an exposure time for controlling the exposure time of the image sensor. a control means, an imaging current storage means for storing a current corresponding to the output level of the image sensor, an analog/digital conversion means for obtaining a digital signal corresponding to the amount of current stored by the storage means, and a conversion means by the conversion means. Since the camera is configured to include an exposure control means for controlling the aperture means and/or the exposure time control means in accordance with the digital signal, there is no need to separately provide a device dedicated to photometry, and the camera body can be miniaturized. It is possible to provide an automatic exposure control device that enables proper exposure control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an electronic circuit of an automatic exposure control device according to an embodiment of the present invention, and FIG. 2 is a timing chart showing operating waveforms in various parts of the electronic circuit of the automatic exposure control device. DESCRIPTION OF SYMBOLS 11... Optical system block, 12g, 12b... Lens, 13... Iris, 14... Iris drive motor, 15... Area sensor, 16... Timing generator, 17... H driver, 18-V driver, 19
・$ control unit, 20...Iris drive motor control line, 21...Shutter speed control line, 22...A
/D converter, 23... image data memory, 24...
DC cut circuit, 25.28... operational amplifier, 26.
... Clamp circuit, 27... Constant current circuit section, 29...
- A/D converter, 30... latch circuit, CP... clamp pulse, VD... vertical synchronization signal. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] An image sensor for obtaining image data, an aperture means for controlling the amount of light irradiated to the image sensor, an exposure time control means for controlling the exposure time of the image sensor, and an output of the image sensor. an imaging current storage means for storing a current according to the level; an analog/digital conversion means for obtaining a digital signal corresponding to the amount of current stored by the storage means; 1. An automatic exposure control device comprising: and an exposure control means for controlling the exposure time control means and/or the exposure time control means.