JP2935048B2 - Automatic exposure control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic exposure control device in, for example, an electronic still camera using a solid-state imaging device such as a CCD.

[Prior art and its problems] In recent years, most of general cameras have an AE (auto exposure) function and an AF (auto focus) function.
When a desired depth of field is obtained using a camera equipped with an AE function, AE is performed with aperture priority.

In other words, in order to increase the depth of field, an operation is usually performed to close the aperture and slow down the shutter speed.For a camera equipped with the AE function with the aperture priority, the operator manually sets the aperture value. The AE works so that an appropriate exposure is obtained according to the aperture value, and the shutter speed is automatically set.

However, conventionally, since the selection of the aperture value for the desired depth of field is performed based on the experience of the operator, there is a problem that failure is likely to occur.

[Object of the Invention] The present invention has been made in view of the above problems, and it is not necessary to manually set an aperture value based on the experience of an operator.
It is an object of the present invention to provide an automatic exposure control device capable of obtaining an exposure state according to a desired depth of field.

[Summary of the Invention] That is, the automatic exposure control device according to the present invention is formed by an imaging lens, a diaphragm unit for adjusting the amount of incident light of an optical image incident through the imaging lens, and an image formed through the imaging lens and the diaphragm unit. Imaging means for outputting an electrical image signal based on an optical image, exposure control means for controlling an exposure time of an optical image converted to an image signal by the imaging means, and an image signal converted to an image signal by the imaging means. Area designating means for arbitrarily designating two focus areas with respect to the optical image,
Distance detecting means for determining the distance to each of the objects corresponding to the two focus areas; and lens movement for moving the imaging lens so that the object corresponding to any one of the two focus areas is in focus. Means, a distance difference calculating means for calculating a distance difference between respective distances to the objects respectively corresponding to the two focus areas obtained by the distance detecting means, and detecting a luminance of an optical image applied to the imaging means. A luminance detecting unit, and a diaphragm unit based on a distance difference between the object corresponding to each of the two focus areas obtained by the distance difference calculating unit and a luminance of an irradiation optical image with respect to the imaging unit detected by the luminance detecting unit. Aperture / exposure time setting for setting the aperture value and the exposure time of the optical image by the exposure control means It is constructed by a stage.

Embodiments of the Invention One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an electronic circuit in an electronic still camera equipped with an AE / AF function. In FIG. 1, reference numeral 10 denotes a control unit, which controls the operation of each circuit unit. The control unit 10 includes a mode switch 11 for setting a shooting mode by switching between an auto mode and a manual mode of AE (auto exposure) and AF (auto focus), a release switch 12 operated at the time of subject shooting, and A measurement area designating unit 13 for designating a photometry area for AE control in the shooting area to be spot measurement or total measurement, and for designating a focus area for AF control is connected.
Here, the measurement area designating unit 13 sets
In order to obtain a clear image only at one focal length, for example, to specify a focus area at a location, two focus areas A and B are superimposed and specified at that location. To obtain a clear image with the depth of field between the focal lengths, the front side is designated as the focus area B and the back side is designated as the focus area A. In this case, the focus is finally adjusted for the focus area B, and the depth of field between the focus areas A and B can be obtained by selecting the aperture and the shutter speed based on the AE control. Reference numeral 14 denotes a finder for visually setting the photographing area. Inside the finder 14, a liquid crystal display unit 15 is provided. The liquid crystal display section 15 displays a designated area on a shooting area in accordance with a designation operation of the photometry area or the focus areas A and B by the measurement area designation section 13, and the liquid crystal display section 15 includes a control section 10 Drive control is performed through the liquid crystal drive unit 16 by a control signal from the controller.

On the other hand, 17 is an imaging optical system, 18 is an imaging lens, 19 is an iris (aperture), 20 is a zoom lens, and the subject image captured by the finder 14 is the imaging lens 18, the iris 19 and the zoom lens 20. Through the solid-state imaging device (CC
D) Optically imaged at 21. The imaging lens 18 is driven by a lens drive motor 22, and the drive of the lens drive motor 22 is controlled by a motor drive control unit 23. The motor drive control unit 23 receives an auto focus control signal from the auto focus control unit 24 to obtain an optimum focal length corresponding to the focus areas A and B. The iris 19 is driven by an iris drive motor 25, and the iris drive motor 25 is drive-controlled by a motor drive control unit 26. The iris control signal indicating the aperture opening corresponding to the optimum exposure value is input from the automatic exposure control unit 27 to the motor drive control unit 26.

The solid-state imaging device 21 has a large number of pixels composed of photodiodes arranged horizontally and vertically, converts the image information formed into an electric signal of a level corresponding to the image light amount, and outputs the electric signal. A large number of pixels of the solid-state imaging device 21 are horizontally scanned by an H driver 28 and a V driver
Vertical scanning is performed by 29. The horizontal scanning timing of each pixel of the image sensor with respect to the H driver 28 and the V driver 29
Is equivalent to an imaging exposure time (shutter speed), and the imaging exposure time is controlled by the transfer control unit 30. For the transfer control unit 30, the automatic exposure control unit 27 sends the exposure time data storage unit 31
Is supplied with the shutter speed (exposure time) instruction data written in. Here, the transfer control unit 30 causes the H driver 28 and the V driver 29 to perform the exposure operation of the subject image on the solid-state imaging device 21 according to the imaging exposure time given from the exposure time data storage unit 31. When the scanning control operation of the solid-state imaging device 21 corresponding to the imaging exposure time is completed, the accumulated charge of the optical image is output and transferred in synchronization with the vertical scanning signal V at that time, and the transfer control unit 30 outputs the automatic focus control unit. A transfer end signal is output to 24 and the automatic exposure control unit 27.

The electric signal output for each pixel of the solid-state imaging device 21 is output from the H driver 28 and the V driver 29
The signal is sent to the image signal processing circuit 32 according to the vertical scanning signal.
The image signal processing circuit 32 is synchronized to the vertical synchronization signal V _sync and a horizontal synchronizing signal H _sync is output from the synchronizing signal generating unit 33, an image signal input from the solid-state imaging device 21,
Luminance signal and synchronization signal (Y + S) and color difference signal (RY)
(BY) and the image signal processing circuit.
The luminance signal and the synchronizing signal (Y + S) and the color difference signals (RY) (BY) from the CPU 32 are sequentially sent to an image data memory (RAM) 34 addressed by the control unit 10 and A / D converted. Then, only the luminance signal Y is derived and supplied to the switching circuit 35. Further, the image signal processing circuit 32 supplies a vertical and horizontal synchronization signal corresponding to the output timing of the luminance signal Y to the measurement area control unit 36. The measurement area control unit 36 detects the scanning timing of the photometry area or the focus area specified in advance by the measurement area specification unit 13 based on the vertical and horizontal synchronization signals indicating the solid-state imaging device scanning timing from the image signal processing circuit 32. Then, the switching gate of the switching circuit 35 is turned on.
Only the luminance signal Y of the image signal corresponding to the photometry area or the focus area is given to the automatic exposure control unit 27 or the automatic focus control unit 24 through Here, the automatic exposure control unit 27 obtains the amount of incident light to the solid-state imaging device 21 based on the imaging luminance signal Y corresponding to the designated photometry area from the solid-state imaging device 21. The iris control signal from the automatic exposure control unit 27 is obtained by setting an optimum exposure value based on the depth of field between the shutter and the aperture opening and the imaging exposure time (shutter speed) according to the optimum exposure value. Is provided to the iris motor drive control unit 26, and the exposure time instruction data is provided to the exposure time data storage unit 31. Further, the automatic focus control unit 24 obtains an optimum focal length based on the imaging luminance signal Y corresponding to the designated focus area from the solid-state imaging device 21, and the auto focus control signal for obtaining the optimum focal length is a lens motor. It is provided to the drive control unit 23.

Here, the area data of the focus areas A and B by the measurement area designating unit 13 is written into the registers 40a and 40b of the data register 40 as scanning coordinates for the solid-state imaging device 21, and the measurement area control unit 36 The on / off control of the switching circuit 35 is controlled by the registers 40a, 40
This is performed in accordance with the area data written in b. Further, the distance data A of the focus area A and the distance data B of the focus area B corresponding to the optimum focal distance obtained by the automatic focus control unit 24 are also written in the registers 40c and 40d of the data register 40, respectively. In this case, the distance difference corresponding to the depth of field between the focuses A and B is calculated by the calculation unit in the control unit 10, and written into the register 40e. That is, the automatic exposure control unit 27
Is the focus area A when the optimal exposure value is set.
To B are obtained from the register 40e.

On the other hand, a stored image signal processing unit 37 is connected to the image data storage unit. The stored image signal processing unit 37 converts the digital image signal stored in the image data storage unit 34 into a luminance signal, a synchronization signal (Y + S) and a color difference signal (RY).
The image signal from the stored image signal processing unit 37 is output from an image signal output terminal 38.

FIG. 2 shows the internal configuration of the automatic exposure control unit 27. The imaging luminance signal Y corresponding to the designated photometry area given to the automatic exposure control unit 27 via the switching circuit 35 is shown.
Is converted into a digital signal corresponding to the imaging level of each pixel via the A / D converter 41 and is provided to the adder. The adder 42 adds up digital signals corresponding to the amount of incident light obtained for each pixel corresponding to the designated photometry area of the solid-state imaging device 21. Is given to the aperture / shutter speed conversion table 43. The aperture / shutter speed conversion table 43 stores a plurality of aperture openings / exposure times corresponding to proper exposure, based on the actual brightness addition value corresponding to the designated photometry area obtained at the reference exposure time and aperture opening. Is selected, and one aperture / exposure time for obtaining the depth of field between the focus areas A and B stored in the register 40e is selected from the exposure combinations. The optimum exposure time data of the solid-state imaging device 21 selected by the aperture / shutter speed conversion table 43 is transferred to the exposure time data storage unit 31, and the iris control signal corresponding to the optimum aperture opening is converted to the iris motor drive control unit 26. Is output to

In addition, for the aperture / shutter speed conversion table 43 of the automatic exposure control unit 27, in addition to the distance difference data between the focus areas A / B, the type of imaging lens (wide-angle, standard, telephoto) Is provided with data on the depth of field, such as lens data indicating

Next, the automatic focusing of the electronic still camera having the above configuration
The exposure control processing will be described.

FIG. 3 shows focus areas A and B in the viewfinder 14.
First, the operator looks through the finder 14 and captures the subject, and the photometric area and the focus areas A and B are controlled by the measurement area specifying unit 13 to perform AE control and AF control at a desired depth of field. When designated, the designated focus area is displayed on the liquid crystal display unit 15 by the liquid crystal drive unit 16. Here, when the half-press signals S ₁ and the release switch 12 in the half-pressed state is inputted to the control unit 10, automatic focus-exposure control processing is started as described below.

Figure 4 is a flowchart showing the automatic focus-exposure control processing, i.e., when the half-press signal S ₁ is input to the control unit 10 from the release switch 12, the automatic exposure control unit 27, aperture size and To initialize the exposure time,
An iris control signal corresponding to the fully opened aperture value is output to the iris motor drive control unit 26, and standard exposure time data (1/250 sec) is set in the exposure time data storage unit 31 (steps S1 and S2). Then, the iris 19 is set to the aperture value F = 22 (fully opened) by the iris drive motor 25, and the solid-state imaging device 21 sends the H signal from the transfer control unit 30 to H based on the exposure time stored in the exposure time data storage unit 31. Through the driver 28 and the V driver 29, the shutter speed S =
Exposure is driven at 1/125. Then, the image signal processing circuit 32
From the focus area A,
The luminance signal Y of the pixel area corresponding to B
In addition, a luminance signal of a pixel area corresponding to the designated photometry area is supplied to the automatic exposure control unit 27. Here, the automatic focus control unit 24 firstly sets a contrast level based on the luminance characteristic of the focus area A. Then, the automatic focus control is performed to maximize the value, and the auto focus control signal is supplied to the lens motor drive control unit 23 to move the imaging lens 18 to the optimum focus position (step S3). At this time, a distance A corresponding to the focus area A is calculated by the control unit 10 based on the moving position of the imaging lens 18 according to the autofocus control signal from the autofocus control unit 24, and is stored in the register 40c of the data register 40. It is written (step S4). Further, the auto focus control unit 24 further performs auto focus control to maximize the contrast level based on the luminance characteristics of the focus area B, and supplies an auto focus control signal to the lens motor drive control unit 23 to control the imaging lens 18. Move to the optimum focus position (step S5). At this time, based on the moving position of the imaging lens 18 according to the auto focus control signal from the auto focus control unit 24, the focus area B
Is calculated by the control unit 10 and written into the register 40d of the data register 40 (step S
6).

Then, the distance data A to the focus area A stored in the register 40c and the distance data B to the focus area B stored in the register 40d are stored in the control unit 10.
The distance difference (| distance A-distance B |) is calculated and written again into the register 40e of the data register 40 (step S7).

On the other hand, from the image signal processing circuit 32 to the switching circuit
The luminance signal Y of the pixel area corresponding to the designated photometry area supplied to the automatic exposure control unit 27 through 35 is shown in FIG.
The digital addition is performed from the A / D conversion unit 41 through the addition unit 42, whereby the luminance addition data corresponding to the designated photometry area of the solid-state imaging device 21 is given to the aperture / shutter speed conversion table 43. Here, in the aperture / shutter speed conversion table 43, for example, five combinations of appropriate exposures of the aperture opening and the exposure time based on the luminance addition data corresponding to the specified photometry area are selected. Then, the aperture / shutter speed conversion table 43 indicates the distance difference between the focus areas A and B given from the register 40e through the control unit 10 from the five appropriate exposure combinations selected in advance based on the luminance addition data. A set of appropriate exposure combinations is selected based on the data and the depth-of-field data, whereby the exposure time data for driving the solid-state imaging device 21 to perform the exposure with the optimum exposure time is obtained from the automatic exposure control unit 27. The iris control signal is sent from the automatic exposure control unit 27 to the iris motor drive control unit 26 (step S8).

That is, in the aperture / shutter speed conversion table 43, the distance difference corresponding to the depth of field (|
When the distance A-distance B |) is large, an exposure combination having a small aperture and a low shutter speed is selected from among the five combinations, and the distance difference (| distance A-distance) corresponding to the depth of field is selected. When B |) is small, an exposure combination having a large aperture and a high shutter speed is selected.

Then, in step S8, the exposure time data of the exposure combination selected based on the aperture / shutter speed conversion table 43 is written in the exposure time data storage unit 31,
Further, in a state in which the iris control signal corresponding to the aperture value is output to the iris motor drive control unit 26, the signal S ₂ press from the release switch 12 the shutter all is inputted to the control unit 10, the solid-state imaging device 21 In the state where the iris 19 is adjusted to an appropriate aperture according to a desired depth of field, based on the exposure time stored in the exposure time data storage unit 31,
Exposure driving is performed at an appropriate shutter speed from the transfer control unit 30 through the H driver 28 and the V driver 29. Then, the electric signal accumulated in each of the pixels of the solid-state imaging device 21 in the appropriate exposure state is sent to the image signal processing circuit 32, and the luminance signal and the synchronizing signal (Y + S) and the color difference signal (RY) (B -Y), the image data is sent to and stored in the image data memory 34 addressed by the control unit 10.

Therefore, according to the electronic still camera equipped with the AE / AF function having the above configuration, the focus areas A and B are respectively specified at the two focal positions on the subject, and the focus areas A and B are controlled according to the respective automatic focus controls. The distance difference between A and B is obtained as the depth of field from the movement information of the imaging lens, and a plurality of appropriate exposure combinations (aperture / shutter speed) are obtained from the luminance information of the specified designated photometry area.
Is selected, and one of the proper exposure combinations is selected as the distance difference A.
~ B, so that it is not necessary to manually set the aperture value according to the depth of field according to experience, and it is easy and accurate to obtain a clear image at the desired depth of field. Automatic exposure setting of an aperture value and a shutter speed at which a signal is obtained becomes possible.

In the above embodiment, the distance difference between the focus areas A and B specified on the subject is obtained from the automatic focus control information of the imaging lens for each of the focus areas A and B. For example, a method using reflection of infrared rays or ultrasonic waves may be used.

Although the image data storage unit 34 in the above embodiment is configured using a video RAM, a storage device such as an FDD (floppy disk drive) may be used.

[Effects of the Invention] As described above, according to the present invention, an imaging lens, aperture means for adjusting the incident light amount of an optical image incident through the imaging lens, and optics imaged through the imaging lens and the aperture means Imaging means for outputting an electrical image signal based on an image; exposure control means for controlling the exposure time of an optical image converted to an image signal by the imaging means; and optical means for converting the image signal to an image signal by the imaging means Arbitrarily 2 for the image
Area designating means for designating two focus areas, distance detecting means for finding respective distances to subjects respectively corresponding to the two focus areas designated by the area designating means, and one of the two focus areas A lens moving means for moving the imaging lens so that the subject corresponding to the area is in focus, and a distance difference between respective distances to the objects respectively corresponding to the two focus areas obtained by the distance detecting means. Distance difference calculation means, brightness detection means for detecting the brightness of the optical image applied to the image pickup means, distance difference to the subject corresponding to each of the two focus areas obtained by the distance difference calculation means, and the brightness detection Based on the brightness of the illuminating optical image to the imaging means detected by the means. Aperture and exposure time setting means for setting the aperture value and the exposure time of the optical image by the above-mentioned exposure control means. An automatic exposure control device capable of obtaining an exposure state according to the depth can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electronic circuit in an electronic still camera according to an embodiment of the automatic exposure control device of the present invention, and FIG. 2 is a block diagram showing an internal configuration of an automatic exposure control section in the electronic still camera. FIG. 3 shows a focus area A, in the viewfinder of the electronic still camera.
FIG. 4 is a flow chart showing an automatic focus / exposure control process by the electronic still camera. 10 control unit, 11 mode switch, 12 release switch, 13 measurement area designation unit, 14 finder, 15 liquid crystal display unit, 16 liquid crystal drive unit, 17 imaging optics System, 18 imaging lens, 19 iris, 20 zoom lens, 21 solid-state imaging device, 22 lens drive motor, 23 lens motor drive control unit, 24 auto focus control unit, 25 ... Iris drive motor, 26 ... Iris motor drive control unit, 27 ... Automatic exposure control unit, 28 ... H driver, 29 ... V driver, 30 ... Transfer control unit, 31 ... Exposure time data storage Section, 32 ... Image signal processing circuit, 33 ...
Synchronization signal generator, 34 ... Image data storage, 35 ... Switching circuit, 36 ... Measurement area controller, 37 ... Storage image signal processor, 38 ... Image signal output terminal, 40 ... Data register 40a to 40e: Register, 41: A / D converter, 4
2 ... Addition unit, 43 ... Aperture / shutter speed conversion table.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H04N 5/235 G03B 3/00 A (56) References JP-A-61-246711 (JP, A) JP-A-3-179433 ( JP, A) JP-A-62-280727 (JP, A) JP-A-63-118727 (JP, A) JP-A-60-136480 (JP, A) JP-A-2-294169 (JP, A) JP-A-54-143229 (JP, A) JP-A-61-9630 (JP, A) JP-A-3-288833 (JP, A) JP-A-3-2846 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) G03B 7/097 G03B 15/05 G02B 7/28-7/40 G03B 3/10-3/12

Claims (1)

(57) [Claims] An imaging lens; an aperture unit for adjusting an incident light amount of an optical image incident through the imaging lens; and an electric image signal based on the optical image formed through the imaging lens and the aperture unit. Imaging means for outputting; an exposure control means for controlling an exposure time of an optical image converted to an image signal by the imaging means; and arbitrarily two focus areas for an optical image converted to an image signal by the imaging means. Area designating means for designating, distance detecting means for calculating respective distances to the objects respectively corresponding to the two focus areas designated by the area designating means, and one of the two focus areas Lens moving means for moving the imaging lens so that the object is in focus; Distance difference calculating means for calculating a distance difference between respective distances to the objects respectively corresponding to the two focus areas; luminance detecting means for detecting the luminance of an optical image applied to the imaging means; The aperture value of the aperture unit and the exposure of the optical image by the exposure control unit based on the distance difference to the subject corresponding to each of the two focus areas and the luminance of the irradiation optical image with respect to the imaging unit detected by the luminance detection unit. An automatic exposure control device, comprising: aperture / exposure time setting means for setting time.