JP2001083405A - Device and method for detecting focus and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera system constituted so that a composition intended by a photographer can be quickly photographed by simultaneously detecting a focus at the center and the plural peripheral parts of an imaging device. SOLUTION: This focus detector is constituted so that the defocus amount of a photographing lens is calculated by selectively transmitting the beams CR, CL, LR and LL in areas whose pupil positions are different through the photographing lenses 1a and 1b and correlatively arithmetically operating plural images formed on the imaging device 4 from the beams. Then, the correlative arithmetic operation is carried out according to the images obtained from the central part 41a and the plural peripheral parts 41b and 41c of the imaging device 4. Thus, since the focus can be simultaneously detected at the central part and the plural peripheral parts of the imaging device such as a CCD without adding a mechanical element, quick photographing is easily realized and the image corresponding to the intention of the photographer can be easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection apparatus, and more particularly to a focus detection apparatus, a focus detection method, and a storage medium for calculating a defocus amount of a photographic lens using light beams passing through different regions of a pupil of a photographic lens. About.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as a camera focus detection device. The following three methods are typical methods. 1) A method of obtaining a distance to a subject by triangulation using infrared rays 2) A method of measuring a shift amount of a light beam passing through different regions of a pupil of a photographing lens 3) A method of searching for a peak of a high-frequency component

Of these methods, the method 2) is a focus detection device called a so-called phase difference method. Since the direction and amount of the defocus can be calculated, a still image is photographed by a single-lens reflex type silver halide camera or the like which places importance on quick shooting. It is often used for cameras.

A focus detection device 3) is a so-called hill-climbing method.
Since an image pickup device such as a CD can be used directly, it is widely used in cameras mainly for moving images such as video cameras.

On the other hand, in recent years, so-called digital cameras, which use an image pickup device such as a CCD as an image pickup medium and electrically record image information on a recording medium, have become widespread as an image input device for a personal computer or the like.

[0006] In the case of digital cameras, as a main use method, many focus on quick shooting as in the case of a silver halide camera, and as a AF method, a digital camera passes through a 45 ° mirror like a single-lens reflex type silver halide camera. After a part of the light beam is reflected in a direction substantially perpendicular to the photographing optical axis by a sub-mirror arranged behind the 45 ° mirror, the light beam that has passed through different pupil areas of the photographing lens is re-formed by the re-imaging optical system. A phase difference method is suitable in which an image is formed on a pair of distance measurement sensors behind the image lens, and the direction of the focus position can be determined and the defocus amount can be detected by comparing the positions of the formed images on the sensor.

However, since the back focus of the photographing lens of the digital camera is short in proportion to the image size of the silver halide camera and the digital camera, the digital camera has a 45 ° mirror like a single-lens reflex type silver halide camera. It is difficult to construct a phase difference AF system similar to a silver halide camera.

In recent years, many so-called multi-point AF systems capable of performing focus detection in a plurality of areas of a photographing range have been disclosed as phase difference AF systems.

There are two main reasons for employing a multi-point AF system in a camera as follows. The first reason is that when assuming a composition in which the photographer brings the main subject to a peripheral area other than the center, the main subject is once focused at the center of the screen, and this state is maintained. This is for avoiding the troublesome operation of moving the entire camera so as to achieve the expected composition and then moving to the shooting operation.

The second reason is that if the main subject is different from the photographer's intention and is located at a position slightly deviated from the central AF area, the main subject is out of focus and is different from the photographer's intention. This is to prevent a state in which the image is in focus, that is, the occurrence of a so-called hollow portion.

Multipoint AF for single-lens reflex type silver halide camera
As a system, for example, a configuration disclosed in Japanese Patent Application Laid-Open No. 5-107466 discloses a system in which not only focus information of only a central region of a subject but also a plurality of re-focusing devices for re-imaging light beams from a plurality of peripheral regions of the subject. It comprises an imaging optical system and a plurality of distance measuring sensors corresponding to the respective re-imaging optical systems.

[0012]

However, in the above-described multi-point AF system for a single-lens reflex type silver halide camera, a plurality of re-imaging lenses and a plurality of distance measuring sensors are indispensable in configuration. It is not preferable in terms of cost and space.

Since the arrangement of a 45 ° mirror is extremely difficult due to the configuration of the digital camera as described above, the multi-point AF system widely used in single-lens reflex cameras is replaced with a digital camera. It is difficult to follow the multi-point AF system.

The present invention has been made in order to solve such a problem. In a camera using an image pickup device such as a digital camera or a video camera, it is possible to determine the direction of a focus position and detect a defocus amount. A camera system that achieves a phase difference method and simultaneously performs focus detection at the center and a plurality of peripheral portions of an image sensor to provide a camera system that can quickly capture a composition that matches a photographer's intention. Will focus on unintended parts of
The purpose is to achieve the prevention of so-called hollow holes.

[0015]

A focus detection apparatus according to the present invention selectively passes a light beam in an area having a different pupil position to a photographing lens, and correlates a plurality of images formed on an image sensor from the light beam. A focus detection device that calculates a defocus amount of the photographing lens by calculating, and performs the correlation calculation using images obtained from a central portion and a plurality of peripheral portions of the image sensor.

In one embodiment of the focus detection apparatus according to the present invention, the plurality of images are formed on the image pickup device by passing light beams in the areas having different pupil positions through the photographing lens in time series. Like that.

In one embodiment of the focus detection device according to the present invention, the focus detection device includes a plurality of openings symmetrically arranged with respect to an optical axis of the photographing lens, and a light shielding unit for selectively shielding the openings. The plurality of images are formed on the image pickup device by sequentially shielding the plurality of openings from light with the light shielding unit.

The focus detecting device according to the present invention passes a light beam in an area having a different pupil position to a photographing lens, simultaneously forms an image on each of the light beams on an image sensor, and outputs an output signal obtained from the image sensor. A focus detection device that processes by a plurality of filters having different characteristics, calculates an autocorrelation coefficient from the filter output, and calculates focus information from an obtained peak position. The output signal is obtained from a central portion and a plurality of peripheral portions of the image sensor.

In one embodiment of the focus detection apparatus according to the present invention, the peak position is obtained from the sum of the autocorrelation coefficients of the output signals processed by the plurality of filters having different characteristics. It is configured to calculate focusing information.

In one embodiment of the focus detection device according to the present invention, the plurality of peripheral portions are set at symmetrical positions with respect to a central portion of the image sensor.

In one embodiment of the focus detection device according to the present invention, the plurality of peripheral portions are set in a direction perpendicular to a central portion of the image sensor.

In one embodiment of the focus detection device according to the present invention, the plurality of peripheral portions are set in a horizontal direction with respect to a central portion of the image sensor.

In one embodiment of the focus detection device according to the present invention, the plurality of peripheral portions are set in a diagonal direction of the image sensor with respect to a central portion of the image sensor.

In one embodiment of the focus detection device according to the present invention, the signal charge reading speed of an image obtained from the central portion and a plurality of peripheral portions is different from the signal charge reading speed of an image in another region.

In one embodiment of the focus detection device according to the present invention, the calculation is performed using only luminance signal components of the plurality of images.

The focus detecting device of the present invention comprises: a photographing lens;
An image sensor that receives an object image formed by the photographing lens; and a light beam selecting unit that selectively passes light beams in different areas of the pupil of the photographing lens, and selectively passes through the light beam selecting unit. The defocus amount of the photographic lens is calculated by correlating an image obtained from a central portion and a plurality of peripheral portions of the image sensor among a plurality of images formed on the image sensor by the emitted light flux. .

[0027] The focus detection device of the present invention comprises: a photographing lens;
An image pickup device for receiving the subject image formed by the photographing lens; and a light beam passing means for simultaneously passing light beams in different regions of the pupil of the photographing lens. The image sensor is obtained from the light beam passing through the light beam passing means. Of the output signals, the output signals obtained from the central portion and the plurality of peripheral portions of the image sensor are processed by a plurality of filters having different characteristics, an autocorrelation coefficient is calculated from the filter outputs, and the obtained peak position is obtained. Calculate focusing information.

According to the focus detection method of the present invention, light beams in regions having different pupil positions are selectively passed through the photographing lens, and the images formed at the central portion and the peripheral portion on the image sensor from each of the light beams are correlated. By performing the calculation, the defocus amount of the photographing lens is calculated.

In one embodiment of the focus detection method according to the present invention, the plurality of images are formed on the image pickup device by passing light beams in the areas having different pupil positions through the photographing lens in time series. .

According to the focus detection method of the present invention, light beams in regions having different pupil positions are passed through a photographing lens, and the respective light beams are simultaneously imaged on a central portion and a plurality of peripheral portions on an image sensor. An output signal obtained from the image sensor is processed by a plurality of filters having different characteristics, an autocorrelation coefficient is calculated from the filter output, and focus information is calculated from the peak position.

In one embodiment of the focus detection method according to the present invention, the peak position is obtained from the sum of the autocorrelation coefficients of the output signals processed by the plurality of filters having different characteristics. Calculate focusing information.

The storage medium of the present invention is a computer-readable storage medium storing a program for causing a computer to execute the procedure of the focus detection method.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a focus detection device according to a first embodiment of the present invention and a camera using the same, wherein 1a is a front lens group, 1b is a rear lens group, 2 is a rear lens group 1b. This is a lens line-out mechanism for moving the lens, and includes a motor for moving the lens and its driver.

Reference numeral 3 denotes a shutter stop system including a pupil position moving mechanism, 4 denotes an image pickup signal processing system such as a CCD that converts an optical image into a photoelectric signal by converting the optical image, and 5 denotes an A / D converter that digitizes the image signal. , 6 are digital signal processing units for performing various digital signal processing of the digital video signal converted in 5, 7
Is a system control section of the entire camera, 8 is a PCMCIA-compliant slot connected to a recording medium, a function card, and the like and its controller section, 9 is a buffer memory such as a DRAM used for temporary storage of digital video signals, 10 is an electronic viewfinder (EV
F), 11 is a driver section of the EVF, 12 is a D / A converter for sending an analog signal to the driver section, 13
VRAM for holding an image to be displayed on an EVF and outputting a digital signal to a D / A converter, 14 for an external black and white liquid crystal (EXT.LCD) for displaying camera mode data and the like,
15 is the EXT. Reference numeral 16 denotes an operation unit outside the camera, such as a shutter button and a dial, for example, a controller and a driver for displaying on the LCD.

First, when the shutter button of the operation unit 16 is half-pressed, that is, when the switch SW1 is turned on, the system control unit 7 detects this and starts the AF operation. FIG. 12 shows a sequence flow of this AF.

First, the system control unit 7 sends a control signal to the shutter aperture system 3 to control the shutter aperture system 3
Pupil aperture The shutter diaphragm system 3 includes several types of photographing diaphragms having different apertures, and a pupil time division phase difference aperture (hereinafter referred to as CCD or other image signal processing) having two holes formed in the horizontal direction in order to perform pupil time division phase difference AF. From the perspective of system 4,
The aperture disk 3a having the left hole as the left pupil and the right hole as the right pupil), and the aperture disk 3a is rotated in order to select each of the apertures provided on the concentric circle. Motor 3d for inserting the aperture of the iris, and a light shielding plate 3 for shielding either the left pupil or the right pupil during pupil time division phase difference AF.
b, and a motor 3c for moving the light shielding plate 3b.

In order to perform the pupil time division phase difference AF, the diaphragm disk 3a is rotated by an instruction from the system control unit 7 so that the pupil time division phase difference stop comes in the optical path.
FIG. 2 is a diagram showing a positional relationship between the stop disk 3a and the light-shielding plate 3b. A circle A shown by a broken line in FIGS. 1 and 2 shows a pupil shape when the stop of the imaging optical system is opened. I have. First, FIG.
As shown in (a), the right pupil of the pupil time-division phase difference stop is closed by the light shielding plate 3b (step S11, see FIG. 12, the same applies hereinafter), and only the light beam on the left side of the lens is used by the imaging signal processing system 4 such as a CCD. First, light is measured for setting exposure conditions (step S12).

It is desirable that the time required for photometry or the time required for reading data for taking in AF data be as short as possible in order to reduce the so-called shutter time lag.

In reading data for taking in AF image data, it takes a long time to read the entire screen of the solid-state image pickup device, as in the case of reading an image of actual photographing. Only a part of the image necessary for the image is read out by the same reading method as in the actual shooting, and the reading of the other part is read out at high speed.

Such a reading method will be described below.
FIG. 3 shows a schematic diagram of the imaging signal processing system 4 (interline CCD). 31 is a pixel, 32 is a vertical charge transfer element,
33 is a horizontal charge transfer element, and 34 is an output unit.
The signal charge photoelectrically converted by the pixel is sent to the vertical charge transfer element, and is sequentially transferred in the direction of the horizontal charge transfer element by four-phase drive pulses φV1, φV2, φV3 and φV4.

The horizontal charge transfer element transfers the signal charges for one horizontal line transferred from the vertical charge transfer element to the output section by the two-phase drive pulses φH1 and φH2, where it is converted into a voltage and output.

FIG. 4 is a schematic view of an image pickup area of a CCD.
In this example, in order to speed up the read operation, only a necessary read area is read at a normal speed, and in other cases, a sweep transfer for reading at a high speed is performed. 41 is an area to be read out as usual, and 42 and 43 are high-speed sweep transfer areas in the first half and the second half, respectively.

FIG. 5 is a timing chart for one vertical synchronizing period when the vertical charge transfer element of the CCD is driven in four phases. VD denotes a vertical synchronization signal and a vertical blanking period is indicated by a LOW potential, and HD denotes a horizontal synchronization signal and a horizontal blanking period is indicated by a LOW potential. φV1, φV2,
φV3 and φV4 denote four-phase driving pulses of the vertical charge transfer element, and 51 and 52 denote read pulses for transferring signal charges photoelectrically converted by the pixels to the vertical charge transfer element. Reference numerals 53 and 54 of the four-phase drive pulses indicate high-speed sweep transfer pulses for transferring the signal charges read to the vertical charge transfer elements in the regions 42 and 43 in FIG. 4 at high speed, respectively. By sweeping out the area other than the necessary reading area at high speed in this way, the speed of the partial reading operation can be increased.

The exposure condition is set based on the partial data read in this way (step S14), and the first exposure for AF is performed (step S15). At this time, depending on the photometric value, it may be determined that distance measurement is not possible due to low luminance (step S13, YES). At that time, although not shown as a sequence flow, a normally used pupil time division phase difference is used. By using a pupil time-division phase difference stop having a stop hole having a pupil area larger than the stop, the amount of light received by the CCD is increased so that distance measurement cannot be performed even at low luminance.

As another method, there is a method of emitting auxiliary light (not shown). At this time, exposure conditions for auxiliary light are set (step S21), auxiliary light is emitted (step S22), and exposure is performed. Further, high-speed reading is performed in the same manner as in photometry, and the data is stored in the camera (step S23).

Next, the CCD is reset and the motor 3c is driven to move the light shielding plate 3b as shown in FIG. 2 (b) in order to obtain AF image data consisting of light beams passing through different pupil regions. Then, the closed aperture is opened and the other aperture is closed, exposure conditions are set (steps S16 and S24), and the second exposure is performed. If the auxiliary light is emitted at the time of the first exposure,
Also for the second time, the exposure condition setting for the auxiliary light is performed, and the exposure is performed by emitting the auxiliary light (steps S24 and S25).

Then, partial high-speed reading is performed in the same manner as in the first time, and the data is fetched (step S17).
The correlation calculation with the data held for the second time is performed to obtain the defocus amount (step S18).

Hereinafter, the algorithm of the correlation calculation will be described. Image data (left image) consisting of a light beam passing through the left pupil region and image data (right image) consisting of a light beam passing through the right pupil region are fetched, and the two output data are correlated. The method of correlation is "max algorithm"
And the data of the left image is a (i) (however,
i = 1, 2, 3,..., n), and the data of the right image is represented by b (i)
(Where i = 1, 2, 3,..., N), the correlation amount C
(Τ) is represented by the following equation.

[0049]

(Equation 1)

Here, max [a (i + τ), b
(I)] is the larger value of a (i + τ) and b (i), and m is for calculating the correlation amount extracted from n output data a (i) and b (i). (M <n). Also, i0 is the number to be skipped when extracting m data from n data of the right image.

In practice, first, c (0) when τ = 0 is calculated. Next, as shown in FIG.
From (i), m pieces of data shifted to the right by τ = 1 are extracted, and the correlation amount c between this data and the data of the right image is extracted.
Calculate (1). In this way, τ = 0, 1, 2,
.., T, the correlation amount c (τ) is sequentially calculated. The shift amount τ when the minimum value is obtained among the correlation amounts c (τ)
Are the data a (i) of the left image and the data b (i) of the right image
Corresponds to the deviation amount. Furthermore, in order to improve the detection accuracy of the shift amount (calculate the shift amount τ to a value below the decimal point instead of an integer value (pixel)), an interpolation calculation is performed using the minimum value of the correlation amount and values before and after the correlation amount. , The shift amount may be calculated.

When a plurality of lines are used as data for the correlation operation, for example, a correlation operation is performed for each corresponding line, and an average of the obtained correlation value group is obtained. Before performing the calculation, the shift amount may be obtained by averaging a plurality of line data in the vertical direction to obtain data for one line and then performing a correlation operation. It is also possible to calculate a correlation between a plurality of lines.

In order to reduce the effects of the pattern of the subject, the contrast, and the like, the effects of the difference in photographing conditions, the effects of the color filter array built in the solid-state image sensor, and the effects of noise, the output data from the sensor is reduced. May be subjected to a filter operation, and then a correlation operation may be performed.

Further, when the output data from the sensor is processed into image data, only the luminance signal is used for the purpose of shortening the time required for focus detection by speeding up the processing of the image data. The correlation operation may be performed using the image that has been placed.

Depending on the optical system, a fixed relational expression is established between the image shift amount and the defocus amount, and the defocus amount and the focus shift amount. Therefore, the defocus amount is obtained from the image shift amount calculated by the correlation operation. The focus movement amount is calculated from the defocus amount, the focus lens of the optical system is moved in the optical axis direction (step S19), and the AF pupil diaphragm is retracted from the optical path (step S20). Of course, this retreat operation may be performed during the movement of the lens.

The above is a series of operations of the pupil time division phase difference AF. This operation is performed until the image plane enters the range near the focus.

In the actual shooting, the diaphragm disk 3a is rotated,
After retracting the pupil time-division phase-difference diaphragm from the optical path, the photographer selects a diaphragm for proper exposure from among several types of photographing diaphragms having different apertures, and performs photographing. Then, the data of the solid-state image sensor is read out for recording, subjected to image signal processing by the signal processing unit 6, and subjected to processing such as image data compression if necessary, and recorded on the recording medium via the PCMCIA slot 8. .

At this time, the image data is subjected to video processing for finder display in the signal processing section 6 and the VRAM
13 and is displayed on the EVF 10. This allows the photographer to check the subject image.

Next, a description will be given of an operation relating to focus detection at a plurality of peripheral portions in the present embodiment. In the present embodiment, as shown in FIG. 6, the readout area 41 for focus detection described in FIG. 4 is replaced by a plurality of focus detection areas 41a, 41b,
41c, and focus detection is performed in each of the plurality of focus detection areas.

The focus detection areas 41a and 41b shown in FIG.
7 is shown in FIG. 7, and the image shift amount and the direction of the image shift in the image formed state are shown in FIG. The focus state of the focus detection area 41c will not be described because the focus detection area 41a and the focus detection area 41c have a symmetrical image formation relationship with the optical axis of the photographing lens.

FIG. 7A shows an image forming state of a light beam passing through the right pupil of the photographing lens, and FIG. 7B shows an image forming state of a light beam passing through the left pupil of the photographing lens. FIG. 7C shows an image forming state at the time of actual photographing.

In FIG. 7 (c), a light beam from the subject 71 passes through the front lens group 1a of the photographic lens, and a predetermined luminous aperture provided on the iris disk 3a provides a desired brightness. After the luminous flux is restricted, the light passes through the rear group 1b of the photographing lens and forms an image of the subject on the image pickup device 4 such as a CCD.

In such a photographing optical system, at the time of focus detection, as shown in FIGS. 7A and 7B, a pupil having two holes opened in the horizontal direction by rotating the stop disk 3a. The time-division phase difference stop is inserted into the optical path of the photographing lens, and the light-shielding plate 3b for passing only the light flux from the left or right pupil region is moved to the left and right in time series to sequentially move the left pupil and the right pupil. Shield.

At this time, since the light beam CL passing through the left pupil and the light beam CR passing through the right pupil in the central portion of the CCD are symmetric with respect to the optical axis of the photographing lens, they are constant as shown in FIG. CCD of subject image with respect to defocus amount
The image shift amount a on the surface is the same for the left and right pupils, and the direction of the image shift is opposite to the optical axis.

On the other hand, in the periphery of the CCD,
The light beam LL passing through the left pupil and the light beam LR passing through the right pupil have different incident angles of the light beam on the CCD 4, and as a result, as shown in FIG. The amount of image shift from the in-focus state is such that the light flux LR passing through the right pupil is b and the light flux LL passing through the left pupil
Is c and c> b.

However, the amount of image shift between the central portion and the peripheral portion is a function caused only by the imaging magnification of the photographing lens in an ideal situation ignoring the aberration generated by the photographing lens. The relation between the relative image forming positions of the light beam that has passed through the pupil and the light beam that has passed through the right pupil is the same between the center and the periphery. That is, even when a focus detection area is newly set in the peripheral portion, the image shift amount and the defocus amount can be calculated by the same method as the focus detection operation performed in the central portion.

Therefore, according to the present embodiment, the calculation of the image shift amount and the calculation of the defocus amount in both the central portion and the peripheral portion allow the object not to be located at the center of the imaging region. Thus, focusing can be performed reliably.

In this embodiment, it is also possible to set the focus detection area in the vertical direction with respect to the center by using the same method as setting the focus detection area in the horizontal direction with respect to the center. It is.

FIG. 9 shows an image pickup area of an image pickup device such as a CCD described in FIG. 4. In the example shown in FIG. 9, the readout area for focus detection is not limited to the readout area 41 described in FIG. , Two areas, read areas 91 and 92, are set in the vertical direction of the read area 41. Also, instead of the high-speed sweeping transfer areas 42 and 43 for increasing the focus detection speed shown in FIG.
Four areas of 3, 94, 95, and 96 are set.

A plurality of read areas 9 set in this way
1, 41, and 92, that is, 41 shown in FIG.
By setting a, 91a, and 92a as the focus detection areas, it is possible to set the focus detection areas also in the vertical direction.

As shown in FIG. 11, two focus detection areas 91 and 92 are respectively provided in readout areas 91 and 92 for focus detection.
By setting b, 91c and the focus detection areas 92b, 92c, it is also possible to set the focus detection area in a diagonal direction of an imaging device such as a CCD.

As described above, by setting the focus detection area directly on the image sensor such as a CCD, it is possible to arbitrarily set the read-out and sweep-out areas. Without having to add
The calculation of the defocus amount and the focus detection of the image shift amount can be performed.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. The focus detection device according to the second embodiment and the camera using the same are the same as those in the first embodiment shown in FIG. That is, in FIG. 1, 1a is a front lens group, 1b is a rear lens group,
Reference numeral 2 denotes a lens extension mechanism for extending the rear group 1b of the photographing lens, including a motor for moving the lens and its driver unit, 3 a shutter aperture system including a focus detection pupil opening, and 4 an optical image. An imaging signal processing system such as a CCD that converts photoelectrically into a video signal, 5 is an A / D converter that digitizes the video signal, and 6 is a digital that performs various digital signal processing of the digital video signal converted by 5 A signal processing unit, 7 is a system control unit for the entire camera, and 8 is a PCM connected to a recording medium, a function card, and the like.
A CIA-compliant slot and its controller 9 are used for temporary storage of digital video signals, for example, DRAM
Buffer memory, etc., 10 is an electronic viewfinder (EVF), 11 is a driver section of the EVF, 12 is a D / A converter for sending an analog signal to the driver section, 13 is an image to be displayed on the EVF, A VRAM 14 for outputting a digital signal to the D / A converter 14 is an external monochrome liquid crystal (EXT.L) for displaying camera mode data and the like.
CD), 15 is the EXT. Reference numeral 16 denotes an operation unit outside the camera, such as a shutter button and a dial, for example, a controller and a driver for displaying on the LCD.

First, the shutter button of the operation unit 16 is half-pressed, that is, when the switch SW1 is turned on (step S31, FIG. 14).
(The same applies hereinafter.) The system control unit 7 detects this, and starts the AF operation (step S32). FIG. 14 shows a sequence flow of this AF.

First, the system control section 7 sends a control signal to the shutter aperture system 3 to control the shutter aperture system 3
Pupil aperture The shutter diaphragm system 3 includes two types of photographing diaphragms having different apertures, and two horizontal shutters for performing focus detection (hereinafter, autocorrelation AF) by autocorrelation calculation from signal outputs from an imaging signal processing system 4 such as a CCD. A diaphragm disk 3a having a perforated focus detection pupil opening (hereinafter, the left hole is referred to as a left pupil and the right hole is referred to as a right pupil when viewed from the side of the imaging signal processing system 4 such as a CCD), and a concentric circle In order to select each of the apertures provided above, the motor comprises a motor 3d for rotating the aperture disk 3a to insert a desired aperture in the optical path.

In order to perform the autocorrelation AF, the diaphragm disk 3a is rotated so that the focus detection pupil opening comes in the optical path according to an instruction from the system control unit 7 (step S33).

Next, the light beam passing through the pupil on the right side of the pupil opening for focus detection and the light beam passing on the left side enter the CCD of the imaging signal processing system 4 such as a CCD. Perform (Step S34).

As in the first embodiment, the time required for photometry or the time required for reading data for taking in AF data is determined in as short a time as possible in order to reduce a so-called shutter time lag. Is desirable.

Therefore, the data reading for taking in the AF image data takes a long time to read the entire screen of the solid-state imaging device as in the case of reading the image of the actual photographing. As in the case of the first embodiment, only a part of the image necessary for focus detection is read out by the same readout method as in the main photographing, and the other parts are read out at high speed.

The method of reading is the same as in the first embodiment, but will be described below. FIG. 3 shows a schematic diagram of the imaging signal processing system 4 (interline CCD). 31 is a pixel, 32 is a vertical charge transfer element, 33 is a horizontal charge transfer element, and 34 is an output unit. The signal charge photoelectrically converted by the pixel is
Sent to the vertical charge transfer element, and the four-phase driving pulses φV1, φ
V2, φV3 and φV4 sequentially transfer in the direction of the horizontal charge transfer element.

The horizontal charge transfer element transfers the signal charges for one horizontal line transferred from the vertical charge transfer element to the output section by the two-phase driving pulses φH1 and φH2, where it is converted into a voltage and output.

The image pickup area of the CCD is the same as in the first embodiment. As shown in FIG. 4, also in the present embodiment, in order to speed up the reading operation, only a necessary reading area is read at a normal speed, and in other cases, a sweep transfer for reading at a high speed is performed. 41 is an area to be read out as usual, and 42 and 43 are high-speed sweep transfer areas in the first half and the second half, respectively.

FIG. 5 is a timing chart for one vertical synchronizing period when the vertical charge transfer element of the CCD is driven in four phases.
Is the same as the first embodiment shown in FIG. VD is a vertical synchronization signal, a vertical blanking period is indicated by a LOW potential, and HD is
Indicates a horizontal synchronizing signal, and a horizontal blanking period is indicated by a LOW potential. φV1, φV2, φV3 and φV4 denote four-phase driving pulses of the vertical charge transfer element, and 51 and 52 denote read pulses for transferring signal charges photoelectrically converted by the pixels to the vertical charge transfer element. Reference numerals 53 and 54 of the four-phase drive pulses indicate high-speed sweep transfer pulses for transferring the signal charges read to the vertical charge transfer elements in the regions 42 and 43 in FIG. 4 at high speed, respectively.
By sweeping out the area other than the necessary reading area at high speed in this way, the speed of the partial reading operation can be increased.

Exposure conditions are set based on the partial data read in this manner (step S35), exposure for AF is performed (step S36), and a correlation operation is performed by using the electric signal output from the CCD, thereby obtaining a data. The focus amount is obtained (step S37).

Next, a process of calculating focus information by autocorrelation calculation from the output electric signal will be described with reference to FIG.

In FIG. 13, reference numeral 4 denotes an image pickup device such as a CCD. Reference numerals 102, 103, and 104 denote filters having different characteristics. Reference numeral 105 denotes an autocorrelation coefficient calculator, and reference numeral 106 denotes an adder.

Reference numeral 107 denotes a peak detector, and reference numeral 108 denotes a focus position calculator. Output signal x from imaging element 4
(T) shows three types of filters 102 and 10 having different characteristics.
3, 104. Filters 102, 103,
The characteristics of 104 are, for example, (1), (2),
This is a characteristic as shown in equation (3).

[0088]

(Equation 2)

Here, y (t) indicates the signal after passing through the filter. Therefore, the characteristics of these filters are that the filter 102 is a differential filter that does not transmit high-frequency components much, the filter 103 is a differential filter, and the filter 104 is a filter that transmits only high-frequency components. The signals that have passed through the respective filters are input to the autocorrelation coefficient calculator 105. Assuming that the input signal is y (t), the autocorrelation coefficient calculator 105 calculates C0 (τ) by the following equation (4).

[0090]

(Equation 3)

The three autocorrelation coefficients calculated from the signals passed through the three types of filters are added by the adder 106. The maximum peak position of the autocorrelation coefficient added by the peak detector 107 is calculated, and the focus position calculator 1
At 08, the image shift amount is calculated from the maximum peak position.

Here, for the purpose of speeding up the signal processing and consequently reducing the time required for focus detection, the correlation operation may be performed using a signal using only the luminance signal.

After that, the focus lens is moved in the optical axis direction according to the amount of image shift. Depending on the optical system, a fixed relational expression is established between the image shift amount and the defocus amount, and the defocus amount and the focus shift amount. Therefore, the defocus amount is obtained from the image shift amount calculated by the correlation operation, and further, the defocus amount is calculated. The amount of focus movement is calculated from the amount, and the focus lens of the optical system is moved in the optical axis direction (step S3).
8), the pupil stop for AF is retracted from the optical path (step S)
39). Of course, this retreat operation may be performed during the movement of the lens.

The above is a series of operations of the auto-correlation AF.
This operation is performed until the image plane enters a range near the meeting point.

In the main photographing performed after the end of the AF operation, the photographing is performed by selecting an appropriate aperture from among several kinds of photographing diaphragms having different apertures. Then, the data of the solid-state image sensor is read out for recording, subjected to image signal processing by the signal processing unit 6, and subjected to processing such as image data compression if necessary, and recorded on the recording medium via the PCMCIA slot 8. .

At this time, the image data is subjected to video processing for finder display in the signal processing section 6 and the VRAM
13 and is displayed on the EVF 10. This allows the photographer to check the subject image.

Next, an operation related to focus detection at a plurality of peripheral portions in the present embodiment will be described. In the second embodiment, as in the first embodiment, as shown in FIG.
The readout area 41 for focus detection in FIG. 4 is divided into a plurality of focus detection areas 41a, 41b, and 41c, and focus detection is performed in each of the plurality of focus detection areas.

The focus detection areas 41a and 41b shown in FIG.
The image forming state and the image shift amount and the direction of the image shift in the image forming state are the same as those in the first embodiment shown in FIGS. 7 and 8, and will be described below. The focus state of the focus detection area 41c will not be described because the focus detection area 41a and the focus detection area 41c have a symmetrical image formation relationship with the optical axis of the photographing lens.

FIG. 7A shows an image forming state of a light beam passing through the right pupil of the photographing lens, and FIG. 7B shows an image forming state of a light beam passing through the left pupil of the photographing lens. FIG. 7C shows an image forming state at the time of actual photographing.

In FIG. 7 (c), the light beam from the subject 71 passes through the front lens group 1a of the photographic lens so that a desired brightness is obtained by a predetermined photographic aperture provided on the aperture disk 3a. After the luminous flux is restricted, the light passes through the rear group 1b of the photographing lens and forms an image of the subject on the image pickup device 4 such as a CCD.

In such a photographing optical system, when detecting the focus, as shown in FIGS. 7A and 7B, the focus disk is formed by rotating the aperture disk 3a to form two holes in the horizontal direction. The detection pupil opening is inserted into the optical path of the photographing lens, passes light beams from the left and right pupil areas, and forms an image of the subject on the image sensor 4 such as a CCD.

At this time, since the light beam CL passing through the left pupil and the light beam CR passing through the right pupil at the center of the CCD are symmetrical with respect to the optical axis of the photographing lens, they are constant as shown in FIG. CCD of subject image with respect to defocus amount
The image shift amount a on the surface is the same for the left and right pupils, and the direction of the image shift is opposite to the optical axis.

On the other hand, in the periphery of the CCD,
The light beam LL passing through the left pupil and the light beam LR passing through the right pupil have different incident angles of the light beam on the CCD 4, and as a result, as shown in FIG. The image shift amount from the in-focus state is b for the light beam LR passing through the right pupil, and c for the light beam LL passing through the left pupil, and c> b.

However, the image shift amount between the central portion and the peripheral portion is a function which is caused only by the imaging magnification of the photographing lens in an ideal situation ignoring the aberration generated by the photographing lens. The relation between the relative image forming positions of the light beam that has passed through the pupil and the light beam that has passed through the right pupil is the same between the center and the periphery. That is, even when a focus detection area is newly set in the peripheral portion, the image shift amount and the defocus amount can be calculated by the same method as the focus detection operation performed in the central portion.

Therefore, according to the present embodiment, the calculation of the image shift amount and the calculation of the defocus amount in both the central portion and the peripheral portion enable the calculation even if the subject does not exist at the center of the imaging region. Thus, focusing can be performed reliably.

In the second embodiment, similarly to the first embodiment, as shown in FIGS. 9 and 10, a method similar to that of setting a focus detection area in the horizontal direction with respect to the center is used.
It is possible to set a focus detection area in a direction perpendicular to the center.

FIG. 9 shows an image pickup area of an image pickup device such as a CCD described in FIG. 4. In this embodiment, not only the readout area 41 described in FIG. 41, the readout areas 91,
Ninety-two areas are set. Also, instead of the high-speed sweep transfer areas 42 and 43 for increasing the focus detection speed shown in FIG. 4, the high-speed sweep transfer areas 93 and 9 are provided.
4, 95, and 96 are set.

A plurality of read areas 9 set in this way
1, 41, and 92, that is, 41 shown in FIG.
By setting a, 91a, and 92a as the focus detection areas, it is possible to set the focus detection areas also in the vertical direction.

As in the first embodiment, as shown in FIG. 11, two focus detection areas 91b and 91c and two focus detection areas 92b and 92c are set in the read areas 91 and 92 for focus detection, respectively. This makes it possible to set a focus detection area in a diagonal direction of an image pickup device such as a CCD.

As described above, by setting the focus detection area directly on the image pickup device such as a CCD, it is possible to arbitrarily set the read-out / sweep-out region, and furthermore, special parts are used in all parts on the image pickup device. Without having to add
The calculation of the defocus amount and the focus detection of the image shift amount can be performed.

In each of the above-described embodiments, the case where a single focus photographing lens is used has been described. However, a zoom lens may be used as the photographing lens.

In each of the above-described embodiments, the back lens group 1b disposed on the image sensor side in the focusing operation
However, the focusing operation may be performed by simultaneously moving the front lens group 1a or the front and rear lens groups 1a and 1b disposed on the object side.

Although the case where the pupil is divided into left and right (horizontal directions) as different pupil regions has been described, pupil division may be performed in the upper and lower directions (vertical direction) or in an oblique direction. Or focus detection may be performed using an image obtained by dividing three or more pupils.

Further, only the peripheral focus detection area may be provided without providing the central focus detection area 41a.

The functions of the above-described embodiments are implemented in an apparatus connected to the various devices or a computer in a system so that various devices are operated so as to realize the functions of the above-described embodiments. Computer program (CPU or MPU) for the system or device
The present invention also includes those implemented by operating the various devices according to the programs stored in the program.

In this case, the program code itself of the software realizes the function of the above-described embodiment, and the program code itself and means for supplying the program code to the computer,
For example, a storage medium storing such a program code constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
A magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (operating system) or other operating system running on the computer. Needless to say, even when the functions of the above-described embodiments are realized in cooperation with application software or the like, such program codes are included in the embodiments of the present invention.

Further, after the supplied program code is stored in the memory provided on the function expansion board of the computer or the function expansion unit connected to the computer, the function expansion board or the function expansion unit is stored based on the instruction of the program code. It is needless to say that the present invention also includes a case where a CPU or the like provided in the above performs a part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0119]

According to the present invention, it is possible to achieve a phase difference method capable of judging the direction of the focus position and detecting the defocus amount, and at the central portion and a plurality of peripheral portions of an image pickup device such as a CCD without additional mechanical elements. By simultaneously performing the focus detection in the section, it is possible to easily obtain an image that meets the quick shooting property and the intention of the photographer, and it is also possible to achieve the prevention of so-called hollow holes.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a camera having a focus detection device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an aperture system constituting a pupil position moving mechanism according to the first embodiment of the present invention.

FIG. 3 is an interline CC according to an embodiment of the present invention.
It is a schematic diagram which shows the schematic structure of D.

FIG. 4 is an interline type CC according to an embodiment of the present invention.
It is a schematic diagram which shows the focus detection area of D.

FIG. 5 is an interline CC according to the embodiment of the present invention.
6 is a timing chart for explaining a driving operation of D.

6 is a schematic diagram showing a horizontal focus detection area in a focus detection readout area shown in FIG. 5;

FIG. 7 is a schematic diagram showing an image formation state on a focus detection area shown in FIG. 6;

8 is a schematic diagram illustrating an image shift amount and a direction of the image shift in the image forming state illustrated in FIG. 7;

FIG. 9 is an interline type CC according to an embodiment of the present invention.
It is a schematic diagram which shows the focus detection area of D.

FIG. 10 is a schematic diagram showing a focus detection area in a vertical direction in the focus detection readout area of FIG. 9;

11 is a schematic diagram showing a diagonal focus detection area in the focus detection readout area of FIG. 9;

FIG. 12 is a flowchart illustrating a procedure of an AF operation according to the first embodiment of the present invention.

FIG. 13 shows an autocorrelation A according to the second embodiment of the present invention.
It is a schematic diagram which shows the principle of F.

FIG. 14 is a flowchart illustrating a procedure of an AF operation according to the first embodiment of the present invention.

[Explanation of symbols]

1a Focusing lens group of photographing lens 1b Lens group other than focusing lens group 1b of photographing lens 2 Lens extension mechanism 3 Shutter aperture system including pupil position moving mechanism 4 CCD and imaging signal processing system 5 A / D converter 6 Digital Signal processing unit 7 System control unit 8 PCMCIA-compliant slot and its controller unit 9 Buffer memory 10 Electronic viewfinder 11 EVF driver unit 12 D / A conversion unit 13 VRAM 14 External monochrome liquid crystal 15 EXT. Controllers and drivers for LCD display 102, 103, 104 Filter 105 Autocorrelation coefficient calculator 107 Peak detector 108 Focus position calculator

Continued on the front page F term (reference) 2H011 AA01 BA22 BB02 BB04 2H051 AA00 BA02 BA07 BA12 CB05 CB06 CB22 CE09 CE14 CE18 EA20

Claims (18)

[Claims] 1. A defocus amount of the photographing lens by selectively passing a light beam in an area having a different pupil position with respect to the photographing lens and performing a correlation operation on a plurality of images formed on an image sensor from the light beam. A focus detection device that calculates the correlation calculation based on images obtained from a central portion and a plurality of peripheral portions of the image sensor. 2. The image pickup device according to claim 1, wherein the luminous fluxes in the areas having different pupil positions are passed through the photographing lens in a time-series manner to form the plurality of images on the image sensor. 3. The focus detection device according to claim 1. 3. A plurality of openings symmetrically arranged with respect to an optical axis of the photographing lens, and a light-shielding portion for selectively shielding the openings from light, and the plurality of openings are sequentially arranged by the light-shielding portions. 3. The plurality of images are formed on the image pickup device by light shielding the image pickup device.
3. The focus detection device according to claim 1. 4. A light beam in an area having a different pupil position passes through a photographing lens, and each of the light beams is simultaneously imaged on an image sensor, and an output signal obtained from the image sensor is filtered by a plurality of filters having different characteristics. A focus detection device that calculates the autocorrelation coefficient from the filter output, and calculates the focus information from the obtained peak position, wherein the output signal for calculating the focus information is A focus detection device, wherein the focus detection device obtains the image data from a central portion and a plurality of peripheral portions of an image sensor. 5. The apparatus according to claim 1, wherein said peak position is obtained from an added value of an autocorrelation coefficient of said output signal processed by said plurality of filters having different characteristics, and said focus information is calculated from said peak position. 5. The method according to claim 4, wherein
3. The focus detection device according to claim 1. 6. The focus detection device according to claim 1, wherein the plurality of peripheral portions are set at symmetric positions with respect to a central portion of the image sensor. 7. The focus detection device according to claim 1, wherein the plurality of peripheral portions are set in a direction perpendicular to a central portion of the image sensor. 8. The focus detection device according to claim 1, wherein the plurality of peripheral portions are set in a horizontal direction with respect to a central portion of the image sensor. 9. The apparatus according to claim 1, wherein the plurality of peripheral portions are set in a diagonal direction of the image sensor with respect to a central portion of the image sensor. Focus detection device. 10. The signal charge reading speed of an image obtained from the central portion and a plurality of peripheral portions and the signal charge reading speed of an image in another region are different from each other. Item 13. The focus detection device according to Item 1. 11. The method according to claim 1, wherein the calculation is performed using only luminance signal components of the plurality of images.
The focus detection device according to any one of the above items. 12. A photographic lens, comprising: an image sensor for receiving a subject image formed by the photographic lens; and luminous flux selecting means for selectively passing luminous fluxes in different regions of a pupil of the photographic lens, By correlating an image obtained from a central portion and a plurality of peripheral portions of the image sensor among a plurality of images formed on the image sensor by the light beam selectively passed by the light beam selecting means, A focus detection device for calculating a defocus amount of a photographing lens. 13. A luminous flux, comprising: a photographic lens; an image sensor for receiving a subject image formed by the photographic lens; and a luminous flux passing means for simultaneously transmitting luminous fluxes in different regions of a pupil of the photographic lens. Of the output signals obtained from the luminous flux passing through the passing means, the output signals obtained from the central portion and the plurality of peripheral portions of the image sensor are processed by a plurality of filters having different characteristics, and the autocorrelation coefficient is obtained from the filter output A focus detection device that calculates and calculates focusing information from the obtained peak position. 14. A luminous flux in an area having a different pupil position is selectively passed through a photographing lens, and an image formed in a central portion and a peripheral portion on an image sensor from each of the luminous fluxes is correlated to calculate the correlation. A focus detection method comprising calculating a defocus amount of a photographing lens. 15. The image forming apparatus according to claim 14, wherein the light beams in the areas having different pupil positions are passed through the photographing lens in a time-series manner to form the plurality of images on the image sensor. Focus detection method. 16. An image pickup device that allows light beams in regions having different pupil positions to pass through the imaging lens and simultaneously forms an image of each of the light beams on a central portion and a plurality of peripheral portions on the image sensor, thereby obtaining an output obtained from the image sensor. A focus detection method comprising: processing a signal by a plurality of filters having different characteristics; calculating an autocorrelation coefficient from the output of the filter; and calculating focusing information from the peak position. 17. The method according to claim 1, wherein the peak position is obtained from an added value of autocorrelation coefficients of the output signals processed by the plurality of filters having different characteristics, and the focus information is calculated from the peak position. The focus detection method according to claim 16. 18. A computer-readable storage medium storing a program for causing a computer to execute the procedure of the focus detection method according to claim 14.