JP2015043026A - Image capturing device and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image capturing device which uses an image sensor having focus detection pixels and which realizes both high-speed crop shooting and a large focus detection area.SOLUTION: An image capturing device with a crop shooting feature has an image sensor 158 having focus detection pixels of an image plane phase difference detection type. The image capturing device provides control for reading signals from the focus detection pixels located outside a crop shooting area. A focus detection area setting unit 163 determines whether or not to acquire signals from the focus detection pixels located outside the crop shooting area using area information on focus detection pixels, information on an effective image area of an image capturing lens mounted on a camera main body 150, and information on the crop shooting area to set a focus detection area. Focus detection signal extraction means 164 obtains positional information of the focus detection pixels from the focus detection area setting unit 163, extracts signals from the focus detection pixels in the focus detection area that has been set from output signals of the image sensor 158, and outputs the same to a camera-side CPU 166 via an AF method selection unit 165.

Description

  The present invention relates to an image pickup apparatus that performs focus detection by a phase difference detection method using focus detection pixels of an image pickup element, and a control method thereof.

  In so-called live view shooting, in which shooting is performed while observing a subject image in real time when shooting a still image or a moving image, accurate and fast focus detection is desired. Patent Document 1 discloses a mechanism for performing focus detection by a phase difference detection method during live view shooting. However, in the interchangeable lens digital camera, there is a problem that image data of an area including vignetting is also recorded when an imaging optical system that does not conform to the size of the imaging element is used. For this reason, Patent Document 2 discloses an apparatus for recording an image of an effective screen area by a method of trimming a recording image area to limit a use area (hereinafter referred to as crop photography).

JP 2004-191629 A JP 2005-175683 A JP 2009-244862 A

  In conventional crop photography, if the reading area of an image signal is limited, the reading area related to the signal of the focus detection pixel is also narrowed at the same time in the focus detection by the phase difference detection method. For this reason, the length of a focus detection signal waveform (hereinafter referred to as a detection length) for performing correlation calculation at a focus detection point corresponding to a subject image located around the screen is limited, so that focus detection accuracy is reduced. there is a possibility. In addition, in order to ensure a sufficient detection length, the focus detection point must be arranged closer to the center of the imaging screen, resulting in a narrow focus detection area.

  An object of the present invention is to achieve both speeding up during crop photography and securing a wide focus detection area in an imaging apparatus using an imaging device having focus detection pixels.

  In order to solve the above-described problem, an apparatus according to the present invention includes an imaging element having a focus detection pixel that outputs a focus detection signal based on phase difference detection, and acquires a signal from the imaging pixel in the first region during crop photography. An imaging apparatus that outputs a captured image, the control means for acquiring a signal from the focus detection pixel in the first area and the focus detection pixel in the second area including the first area, and performing a focus detection calculation; Focus adjustment means for adjusting the focus of the imaging optical system according to the result of the focus detection calculation calculated by the control means is provided.

  ADVANTAGE OF THE INVENTION According to this invention, in the imaging device using the image pick-up element which has a focus detection pixel, high-speed at the time of crop photography and ensuring of a wide focus detection area can be made compatible.

1 is a block diagram of an imaging apparatus according to an embodiment of the present invention. It is a figure which illustrates the arrangement | sequence of the focus detection pixel of the system using the mask of an image pick-up element. It is a figure which illustrates the arrangement | sequence of the focus detection pixel of the system which divided the photoelectric conversion part of the image pick-up element into two. It is a figure which illustrates the arrangement | sequence of the focus detection pixel of the system which divides the photoelectric conversion part of an image sensor into 4 and adds 2 signals. It is a figure explaining the pupil projection state of a focus detection pixel. It is the figure which showed the signal waveform of a pair of focus detection pixel group which performs correlation calculation, and a gravity center space | interval (image shift | offset | difference) state. It is the schematic which shows the relationship between the waveform for focus detection in the in-focus state of an imaging optical system, and detection length. It is the schematic which shows the relationship between the focus detection waveform and detection length in the state which the to-be-photographed image by the imaging optical system has produced the largest blur in the imaging optical system. FIG. 5 is a diagram illustrating an effective imaging area, an effective image area, a crop imaging area, and an area where focus detection is possible at the time of maximum gain. It is a figure explaining extending the field where focus detection is possible in this embodiment. It is a flowchart explaining the focus detection process and focusing control operation | movement at the time of imaging | photography of this embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings. The present invention can be applied to an imaging apparatus such as a single-lens reflex camera, a compact digital camera, or a video camera having a crop photography function using an imaging device having focus detection pixels of a phase difference detection method.
FIG. 1 is a configuration diagram of an imaging apparatus according to the present invention. The imaging device includes a replaceable lens unit 100 and a camera main body 150 using an imaging device having focus detection pixels, and can record still images and moving images. It should be noted that description of portions that are not directly related to the technical contents of the present invention, such as an image recording circuit, a display drive circuit, and an operation member, will be omitted. The camera body 150 may include a contrast-type focus detection unit that uses an image from the image sensor.

  The lens group 101 is an optical member constituting the imaging optical system. The iris diaphragm 102 is controlled by a diaphragm diameter driving unit 106 to adjust the light amount during photographing. In this imaging optical system, the focus position is adjusted by moving the lens group 101 in the optical axis direction by the focus driving unit 105. The focus driving unit 105 and the aperture diameter driving unit 106 receive a control command from the lens side CPU (central processing unit) 104 and perform drive control. As will be described later, communication processing is executed between the camera side transmission unit 168 and the lens side transmission unit 103, and exposure adjustment and focus adjustment are performed based on the photometric value and focus detection evaluation value in the camera main body unit 150.

The memory in the lens unit 100 stores effective image area information 107 and various optical system information 108. The effective image area information 107 is an area (effective image area) that conforms to the imaging image area characteristics in which the focus detection image and the shooting and recording image are effective in accordance with the peripheral light amount characteristics and the image circle diameter of the imaging optical system. Show. The optical system information 108 includes the following information.
Information on the exit pupil position of the lens unit 100 and information on the F-number area relating to the settable aperture diameter.
-Optical characteristic information such as the focal length of the imaging optical system (focal length region in the case of an interchangeable zoom lens)-Identification information of the imaging optical system.
The effective image area information 107 and the various optical system information 108 are transmitted from the lens side transmission unit 103 to the camera body unit 150 via the camera side transmission unit 168 by communication.

Next, the configuration of the camera body 150 having the form of an interchangeable single-lens reflex camera will be described.
The presence or absence of deflection of the light beam from the subject via the lens unit 100 is switched by driving the flip-up reflection member 155. In the reference state where the reflecting member 155 is positioned on the photographing optical path, the light beam from the subject is deflected, and a subject image is formed on the focusing screen 154 with a display area adjustment function. The subject image is visually observed by the user through the eyepiece 152 via the pentagonal reflecting prism 151. A part of the subject image formed on the focusing screen 154 is imaged on an internal sensor via the optical system of the photometric unit 153, and an electric signal for photometry is generated. Based on the electrical signal, the exposure amount determination unit 160 determines an appropriate exposure amount, and generates a signal for adjusting the gain amount for the image sensor driving unit 161 and controlling the aperture diameter of the lens unit 100.

  A part of the reflection part of the reflection member 155 has a semi-transmission characteristic, and the transmitted light is deflected by the sub-reflection member 156 and guided to the focus detection unit 157. The sub-reflection member 156 is folded in conjunction with the reflection member 155 in a state where the reflection member 155 is retracted upward from the photographing optical path (see a broken line in the drawing). Thereby, the light from the subject incident on the image sensor 158 is not obstructed.

The light beam guided to the focus detection unit 157 is received by a focus detection sensor in the unit. The focus detection sensor generates a pair of image signals (focus detection signals) for phase difference detection and outputs them to an AF (autofocus) method selection unit 165.
The AF method selection unit 165 switches between a phase difference detection method using a focus detection sensor, or an imaging surface phase difference detection method based on so-called pupil division in which focus detection pixels are arranged on the image sensor 158. Focus detection and focus adjustment are performed according to the selected focus detection scheme.

  The image sensor 158 includes a CMOS (complementary metal oxide semiconductor) sensor capable of partially reading an image pixel signal and its peripheral circuit. The image sensor 158 is squarely arranged with M pixels in the horizontal direction and N pixels in the vertical direction. A two-dimensional single-plate color sensor in which a Bayer array primary color mosaic filter is formed on-chip is used. Although a detailed configuration will be described later, focus detection pixels are arranged in the image sensor.

  Next, description will be made with the imaging element 158 receiving a subject image in a state where the reflecting member 155 moves upward and retracts from the photographing optical path (see the broken line in FIG. 1). First, the effective image area information 107 and optical system information 108 from the lens unit 100, and the dynamic optical system characteristic values such as the aperture diameter (F value) and the focus position output from the lens side CPU 104 are the camera body 150. Is transmitted to. These pieces of information are transmitted to the imaging region setting unit 162 and the focus detection region setting unit 163 via the lens side transmission unit 103 and the camera side transmission unit 168. Information other than information that changes dynamically, such as the aperture diameter, is transferred at the timing when the lens unit 100 is mounted on the camera body 150, for example.

The image sensor driving unit 161 performs a process of setting and driving an area in which an image signal is acquired from the pixel unit on the image sensor 158. The imaging area setting unit 162 determines an imaging area set for recording, outputs area information for displaying a subject image on a focusing screen 154 with a display area adjustment function, and performs display adjustment on the focusing screen 154. Make it.
A focus detection area setting unit (hereinafter referred to as an area setting unit) 163 calculates a detection length necessary for focus detection calculation using effective image area information unique to the imaging optical system and various characteristic information of the imaging optical system. The position information of focus detection pixels necessary for focus detection is defined. A focus detection signal extraction unit (hereinafter referred to as a signal extraction unit) 164 generates a pair of electrical signals for phase difference detection at the focus detection pixel position defined by the region setting unit 163 from the pixel signal obtained by the image sensor 158. Extract. The focus detection signal is output to the AF method selection unit 165.

  The AF method selection unit 165 selects a focus detection signal from the focus detection unit 157 or the signal extraction unit 164. Alternatively, when a contrast method is further employed, a focus detection signal based on the contrast evaluation value is added to the options. In the AF method selection process to be used, for example, the position state of the reflecting member 155 is detected, and the light guide state of the subject light beam is referred to. In addition, the contrast method and the imaging surface phase difference detection method are automatically selected according to the result of evaluating the state of the subject image during live view. Of course, selection by manual setting of user operation is also possible. The focus detection signal selected by the AF method selection unit 165 is output to the camera side CPU 166.

  After determining the AF method to be used, the camera side CPU 166 acquires a focus detection signal from the AF method selection unit 165, performs a focus detection calculation, and calculates a defocus amount. The focus drive amount determination unit 167 calculates the movement direction and drive amount of the focus lens that performs focusing control based on the defocus amount from the camera side CPU 166. The drive control information is transmitted from the camera side transmission unit 168 to the lens side CPU 104 via the lens side transmission unit 103. The focus lens is driven by a drive control command to the focus drive unit 105 to perform focus adjustment. In the present embodiment, there is provided a configuration for ensuring a wide focus-detectable region without degrading high-speed continuous shooting performance during crop photography.

Next, the configuration and light receiving characteristics of the focus detection pixels provided in the image sensor 158 will be described. FIG. 2 shows a structural example of a pixel array of the image sensor 158. The vertical direction in FIG. 2 is defined as the Y direction, and the horizontal direction is defined as the X direction.
A pixel group 200 in FIG. 2 is a pixel group including a photoelectric conversion unit for forming a captured image. The pixel groups 201 to 204 are focus detection pixel groups each including a photoelectric conversion unit in which light shielding structures are arranged in the pixels (see Patent Document 3). Using the photoelectric conversion signals output from the pixel groups 201 and 202 arranged in a line along the Y direction in the figure as a pair of correlation calculation signals for phase difference detection, focus detection is performed on an object having a horizontal stripe pattern shape. Is called. Similarly, for a subject having a vertical stripe pattern, pixel groups 203 and 204 arranged in a line along the X direction in FIG. 2 are used. By obtaining signals output from the pixel groups 203 and 204 and performing a correlation calculation, focus detection is performed on a subject having a vertical stripe pattern shape.

FIG. 3 illustrates a pixel array structure of an image sensor in which two photoelectric conversion units are arranged for one microlens. The vertical direction in FIG. 3 is defined as the Y direction, and the horizontal direction is defined as the X direction.
A pixel group 300 in FIG. 3 is used for focus detection on a subject having a stripe pattern in the X direction. The signals output from the pixels 302 and 303 arranged in the Y direction are used as a pair of correlation calculation signals. The pixel group 301 is used for focus detection on a subject having a stripe pattern in the Y direction. The signals output from the pixels 304 and 305 arranged in the X direction are used as a pair of correlation calculation signals.
For the captured image signal, the addition result of each signal output from the pixels 302 and 303 and the addition result of each signal output from the pixels 304 and 305 are used.

  FIG. 4 illustrates a pixel array structure of an image sensor in which four photoelectric conversion units are arranged for one microlens. The pixel characteristics described with reference to FIG. 3 can be obtained by changing the addition method related to the electrical signals of the four photoelectric conversion units. The vertical direction in FIG. 4 is defined as the Y direction, and the horizontal direction is defined as the X direction.

In FIG. 4, when focus detection is performed on a subject having a stripe pattern in the Y direction by the pixel group 400, the outputs of the pixels 401 and 402 aligned in the X direction and the outputs of the pixels 403 and 404 are added. The obtained pixel signals for two rows are used as a pair of electrical signals for correlation calculation.
In addition, when focus detection is performed on a subject having a stripe pattern in the X direction, the outputs of the pixels 401 and 403 arranged in the Y direction are added and the outputs of the pixels 402 and 404 are added. The obtained pixel signals for two columns are used as a pair of electrical signals for correlation calculation.

  As for the above-described two types of addition processing for focus detection, the addition method may be changed by dividing into a plurality of blocks on the image sensor. A pixel arrangement structure equivalent to the case of FIG. 3 can be realized by alternately changing the addition method in the staggered arrangement. At this time, since the vertical stripe pattern and horizontal stripe pattern subjects can be simultaneously evaluated, it is possible to eliminate the dependency of the subject pattern on the focus detection.

Depending on the shooting state, the addition method for all pixels may be switched in time series. Since focus detection pixels related to focus detection with respect to a subject in the same pattern direction are in a dense state, it is possible to avoid a problem that a subject having a thin line segment that occurs in a sparse range of focus detection pixels cannot be detected in the vicinity of in-focus. .
The signal for the photographed image can be obtained from the addition result of the pixel signals of the pixels 401 to 404.

  By using such an image sensor structure, it is not necessary to separate a part of the subject image via the imaging optical system by an optical system dedicated to focus detection as in the conventional phase difference focus detection method. Therefore, when the image sensor receives light in real time and performs image recording, live view shooting can be performed while monitoring the subject image. This makes it possible to perform focus detection using a phase difference detection method that cannot be performed without subject beam splitting in conventional moving image shooting.

  In the present embodiment, when a CMOS sensor is used as the image sensor, a signal can be partially read from the image pickup pixel or the focus detection pixel. Thereby, a focus detection signal can be acquired from a part of the focus detection pixels.

Next, a structure for generating a focus detection signal of the phase difference detection method by the imaging device having the above configuration will be described with reference to FIGS. The focus detection pixel has, for example, the structure shown in FIG.
A cross section 500 in FIG. 5 shows the focus detection pixel having the structure shown in FIG. 2, and shows the microlens 501 and the light shielding member 502. The photoelectric conversion units 503 and 504 are focus detection pixels that output a pair of electric signals (hereinafter referred to as an A image signal and a B image signal) for performing a correlation calculation. The focus detection pixels are arranged in a line direction as described with reference to FIG. For the photoelectric conversion signal of each focus detection pixel, if necessary, linear interpolation processing or the like is performed using an output signal of an adjacent pixel. The output of the focus detection pixel generates an A image signal and a B image signal for performing correlation calculation.

  In the exit pupil shape EP0 of the imaging optical system, regions EPa and EPb indicate separated pupil regions in which light beams enter the photoelectric conversion units 503 and 504, that is, the focus detection pixels for the A image signal and the B image signal, respectively. . In this way, by separating the entrance pupil of the imaging optical system into a plurality of pupil regions and taking in light rays, focus detection can be performed based on changes in the A image signal and the B image signal in the change of the in-focus state.

FIG. 6 exemplifies output waveforms of the focus detection pixel groups for the A image signal and the B image signal when the focus detection pixels shown in FIG. 5 are arranged in one line direction.
Waveforms AI0 and BI0 shown in FIG. 6 are waveforms obtained by interpolating the output signals of the focus detection pixel groups for the A and B images. In the focus detection using the phase difference detection method, for example, when the relative positions of the A image waveform and the B image waveform are shifted and the waveforms are superimposed, the state where the area amount of the difference portion is the smallest is the correlation degree. It is judged to be high. At the time of correlation calculation, as indicated by L0 in FIG. 6, a relative shift amount (image shift amount) for shifting the A image waveform and the B image waveform is calculated, and conversion processing to a defocus amount from this is performed. Done.

  Therefore, it is desirable that the acquired waveform has a sufficient length in order to perform accurate correlation calculation using a pair of focus detection signal waveforms during focus detection. For example, a case is assumed in which the end of one waveform of the A image and the B image is interrupted in the waveform of FIG. In this case, when the correlation calculation is performed, an image shift amount different from the image shift amount that actually shows the maximum degree of correlation is calculated. That is, when the detection length according to the imaging state cannot be ensured, the focus detection accuracy decreases.

  FIG. 7 and FIG. 8 show a state when the subject is focused on the imaging surface including the focus detection pixels, and a state where the image is out of focus and the image is greatly blurred. Hereinafter, a conceptual description will be given regarding the difference in detection length required in each state.

  7 and 8 show a state in which a subject image is formed on the imaging surface for a cross-shaped subject 701. The light from the subject 701 forms an image on the imaging surface 702 of the imaging element having focus detection pixels via the imaging optical systems 700a to 700c as indicated by light rays 703a to 703c. 7A and 8A and 8B show schematic optical path diagrams. FIGS. 7B and 8C show a simplified relationship between the focus detection pixels and the subject image.

FIG. 7 shows a state of the subject image 710a that is substantially in focus.
The focus detection pixel group 711 is arranged in the horizontal direction and detects the in-focus state of the vertical direction component. The focus detection pixel group 712 is arranged in the vertical direction, and detects the in-focus state of the horizontal direction component. Signal waveforms 720a and 721a indicate output signals of the A image and the B image obtained by the focus detection pixel group 711, respectively. Signal waveforms 730a and 731b indicate output signals of the A image and the B image obtained by the focus detection pixel group 712, respectively. Correlation calculation is performed using these signal waveforms. In an almost in-focus state, the image shift amount between the A image signal and the B image signal is small. Accordingly, accurate focus detection can be performed without using all focus detection signals over the detection lengths related to the focus detection pixel groups 711 and 712.
A method of performing focus detection simultaneously on the horizontal and vertical component images of the subject as described above is referred to as a cross focus detection method.

FIG. 8 shows a state in which the subject is greatly out of focus and a blurred subject image 710 b is formed on the imaging surface 702.
FIG. 8A shows a so-called rear pin state in which the focal point is located behind (on the right side) the imaging surface. In this case, the subject 701 is located at a close distance in a focus adjustable region of the imaging optical system 700b, and the imaging optical system 700b is set to a focus position in an infinite object distance state. FIG. 8B shows a so-called front pin state in which the focal point is located in front (left side) of the imaging surface. In this case, the subject 701 is located at an infinitely far position, and the imaging optical system 700c is set to a focus position in a state where the object distance is close.
In the two states shown in FIGS. 8A and 8B, the amount of blur when the degree of blur becomes the maximum is referred to as the maximum blur amount of the imaging optical system. Normally, the maximum amount of blur is the amount of blur when the aperture of the imaging optical system is open. Each amount of blurring in the states of FIGS. 8A and 8B is equivalent for convenience of explanation.

  When it is desired to dynamically change the focus detection area when the aperture value changes, the focus detection area is set so that the maximum amount of blur corresponding to each aperture value can be derived. At this time, the numerical value related to the information indicating the maximum amount of profit is stored in the memory in the form of a reference table. Alternatively, a coefficient value with the aperture value as a variable may be stored in a memory, and the maximum amount of profit may be calculated from an arithmetic expression. Further, when the imaging optical system is a zoom lens, it is preferable to divide the focal length region so as to have the maximum amount of blur for each region.

Signal waveforms 720b and 721b in FIG. 8C respectively show an A image signal and a B image signal by the focus detection pixel group 711 in a state where the blur amount is large. Signal waveforms 730b and 731b respectively indicate an A image signal and a B image signal by the focus detection pixel group 712 when the blur amount is large. The detection length 740 indicates a detection length necessary to detect the focus of the blurred image with respect to the vertical component of the light beam from the subject. The detection length 741 indicates a detection length necessary for detecting the focus of the blurred image with respect to the horizontal component of the luminous flux from the subject.
By setting the detection length in each direction, the expanded waveform of the vertical component (see signal waveforms 720b and 721b) and the horizontal component (signal waveforms 730b and 731b) when the degree of blurring is large. The entire signal can be captured.

Next, with reference to FIG. 9 and FIG. 10, the relationship between the crop imaging area on the image sensor having the focus detection pixel, the effective image area, and the focus detectable area derived from the position of the focus detection pixel will be described.
FIG. 9 shows a focus-detectable region when focus detection is performed using focus detection pixels only in the designated crop photography region. FIG. 10 shows a focus-detectable area when setting to read out a part of focus detection pixel signals necessary for focus detection outside the crop photography area in the present embodiment.
An area 900 in FIGS. 9 and 10 indicates an effective imaging area of the imaging device. The information of the effective imaging area 900 is updated by the camera side CPU 166 by the change of the magnification position or the focus position of the imaging optical system. In addition, when the update of information becomes a load on the imaging system, information on the area where the area becomes the narrowest among the effective imaging areas that can be dynamically taken by the imaging lens attached to the camera body is used as a representative value. Also good.
A first area 901 indicates a crop photography area that limits an image signal acquisition area. The effective image area 902 has a smaller image circle diameter than the effective imaging area 900. That is, an example in which an imaging optical system (photographing lens) with a narrow shootable area is mounted on the camera body is shown.

  A horizontally long rectangle constituting the cross shape indicates a detection long region 904, and a vertically long rectangle indicates a detection long region 905. As described with reference to FIG. 8, the detection length regions 904 and 905 correspond to detection lengths necessary for focus detection, which are obtained from the maximum amount of blur of the photographing lens attached to the camera body. A focus detection center point 903 for the subject and its range (see rectangular frame 906) are shown.

  As a premise, it is assumed that cross focus detection is possible in the detection long regions 904 and 905, and the focus detection pixel group is arranged over the crop photographing region 901. The area where focus detection is possible even in the maximum blur state is limited so that the detection areas 904 and 905 in the vertical direction and the horizontal direction can be accommodated in the crop photography area 901. As a result, the region (first focus detection region) indicated by the rectangular frame 906 in FIG. 9 is limited as the region where the focus detection center point is arranged.

FIG. 10 shows a second area 1009 in which the focus detection signal can be captured for the necessary detection length outside the crop photography area 901. A part of the focus detection pixels can output a focus detection signal with a detection length necessary for focus detection in the second area where the effective image area 902 and the effective imaging area 900 overlap.
For example, the focus detection center point 1000 is shown at the intersection of the detection long regions 1001 and 1002. When focus detection is performed on a subject corresponding to this point, the above-described maximum gain information is used when reading a signal of a focus detection pixel outside the crop shooting area 901. This information is obtained from information on the focal length, aperture diameter, and focusable area of the imaging optical system.

  With respect to the detection length that enables focus detection in the maximum blur state, the detection length region 1001 is necessary for focus detection of the vertical component, and the detection length region 1002 is required for focus detection of the horizontal component. As for the subject corresponding to the focus detection center point 1003, in the case of the maximum blur state as described above, the signal of the focus detection pixel is acquired according to the necessary detection length represented by the detection length areas 1004 and 1005.

As described above, for the focus detection pixels that are within the effective image pickup area 900 and within the effective image area 902 even outside the crop image pickup area 901, only a limited focus detection pixel signal necessary for focus detection is acquired. Is done. This signal is captured in addition to the image signal from the imaging pixels in the crop photography area 901. Since the increase in the reading time of the focus detection pixels added to the image signal for recording is slight, the influence on the processing time is small.
The focus detectable area shown in FIG. 10 is expanded from the area of the rectangular frame 906 to the area 1006. That is, when only the focus detection signal limited in the crop photography area 901 is captured, the area (first focus detection area) indicated by the rectangular frame 906 is used. On the other hand, in the present embodiment, the area can be expanded to the area 1006 (second focus detection area) so as to include the focus detection center points 1000 and 1003. An area 1006 is in the first area (in the crop photography area 901), but the detection long area used for focus detection extends to the second area 1009.

  In high-speed continuous shooting that requires only a slight increase in signal reading time, first, a signal of a focus detection pixel outside the cropped imaging region 901 is read. The camera side CPU 166 performs processing for setting a focus detectable area. The information used at this time is the area information of the focus detection pixel, the information of the effective image area of the imaging optical system, and the information of the crop imaging area, and whether to use the signal of the focus detection pixel outside the crop imaging area. Is judged. In the case of the determination result that the signal of the focus detection pixel outside the crop photographing area is used, as described in comparison with FIG. 9 and FIG. 10, the focus detectable area is enlarged. On the other hand, if the focus detection center point is within the area indicated by the rectangular frame 906 in FIG. 9, it is not necessary to capture the signal of the focus detection pixel outside the crop photography area 901. In this case, information indicating the area of the rectangular frame 906 is stored in the memory. Since the camera-side CPU 166 can refer to this information and determine whether or not it is necessary to read the signal of the focus detection pixel outside the crop shooting area 901 in accordance with the selected focus detection point (focus detection position information). Is good.

FIG. 11 is a flowchart for explaining a focus detection process and a focus control operation during photographing according to the present embodiment. It is assumed that the aperture operation of the imaging optical system is performed so as to achieve proper exposure during live view, and the AF-enabled area is changed by detecting a change in the aperture value. The following processing is realized by the camera side CPU 166 reading and executing the control program from the memory.
When the image pickup apparatus is turned on, the area information of the focus detection pixel is set in S100, and the area information is transmitted to the focus detection area setting unit 163 in FIG. In the next S101, the mounting state of the taking lens on the camera body is detected. In step S102, the camera side CPU 166 acquires effective image area information from the photographing lens. The effective image area information of the photographic lens is transmitted to the imaging area setting unit 162 in FIG.

  In next step S103, the camera-side CPU 166 acquires information on various characteristics of the photographing lens (imaging optical system). The information on various characteristics is a group of information related to a necessary detection length at the time of focus detection, such as a photographing lens mounted on the camera body, that is, a maximum blur amount of the imaging optical system or a blur amount with respect to an aperture value. . The maximum amount of blur is the amount of blur when the subject at the closest position is photographed when the focus lens position is at infinity, or conversely, the subject at an infinite distance when the focus lens position is in the closest state. Shows the amount of profit when shooting. In S104, a specific AF method is determined from a plurality of focus detection methods (AF methods) employed in the imaging apparatus. When determining the AF method, the camera side CPU 166 determines, for example, whether or not the camera is in a live view mode in which light from a subject is incident on the image sensor. For this reason, it is detected whether or not the movable reflecting member 155 shown in FIG. 1 is in a state of jumping up and retracting from the photographing optical path.

  S105 is a determination process for performing branch selection of the subsequent process by the AF method selected in S104. It is determined whether the imaging surface phase difference detection method or another method is used. Other AF methods include TTL phase difference detection using a focus detection signal output from the focus detection unit 157. In addition, there are a method using a focus detection unit without using an imaging optical system, a subject contrast method, and the like. If an AF method other than the imaging surface phase difference detection method is selected in S105, the process proceeds to S106, and focus detection processing of another AF method is executed.

After S106, in S114, the camera side CPU 166 calculates the defocus amount and performs in-focus determination. When it is determined to be in focus within the setting conditions, a series of processing ends. Actually, the focus determination process in S114 may differ depending on the focus detection method. In S114, it is assumed that the camera-side CPU 166 comprehensively performs the focus determination of the focus detection unit provided in the imaging apparatus.
If it is determined in S114 that the focus is not within the set conditions, the process proceeds to S115. The focus drive amount determination unit 167 determines the drive direction and drive amount of the focus lens based on the calculated defocus amount. Thereafter, the process proceeds to S116, and the focus lens driving process necessary for performing the focusing operation is executed. Then, the process returns to S105, and the focus detection process corresponding to the change of the subject is repeated.
On the other hand, if it is determined in S105 that the AF method is the imaging plane phase difference detection method, the process proceeds to S107, and a focus detection point selection process is performed to select a location to be focused on the subject.

Next, in step S108, aperture data acquisition processing for the imaging optical system is executed. In S109, using the aperture value information (F number information) obtained in S108, the area setting unit 163 calculates a detection length necessary for the focus detection process as described with reference to FIG. S110 is a process for determining whether or not the area having the detection length calculated in S109 (see FIGS. 9 and 10) exceeds the crop photography area. This process is performed by the area setting unit 163, and if it is determined that it is necessary to read the signal of the focus detection pixel in the range exceeding the crop photography area, the process proceeds to S111. If it is determined to read the signal of the focus detection pixel in the crop photography area, the process proceeds to S112.
In S111, in accordance with the determination result of reading the focus detection pixel signal, the focus detection signal reading setting necessary outside the crop photography region is set.

In S112, the signal extraction unit 164 performs a focus detection signal acquisition process for the focus detection pixels set in steps S109 to S111. In S113, a focus detection calculation process is performed using the focus detection signal acquired in S112, and a defocus amount is calculated. Then, the process proceeds to S114, and as described above, an in-focus determination is made based on the defocus amount.
In the description of FIG. 11, a necessary detection length is calculated according to the currently set aperture value data, and the region setting unit 163 enlarges the focus detection region as much as possible. However, when the calculation is performed simply, for example, information fixed to the detection length when the aperture is opened may be used as the specific detection length information.

  In the present embodiment, an imaging device using an imaging device having an imaging surface phase difference detection type focus detection unit and capable of reading partial pixel signals sacrifices continuous shooting performance during crop photography. In addition, the focus detectable region can be enlarged. Therefore, according to the present embodiment, it is possible to achieve both speeding up during crop photography and securing a wide focus detection area.

DESCRIPTION OF SYMBOLS 100: Lens unit 101: Imaging optical system lens group 150: Camera main-body part 158: Image pick-up element 163: Focus detection area setting part 164: Signal extraction part for focus detection 166: Camera side CPU

Claims (8)

An image pickup apparatus including an image pickup element having a focus detection pixel that outputs a focus detection signal by phase difference detection, outputs a captured image by acquiring a signal from an image pickup pixel in a first region during crop shooting,
Control means for acquiring a signal from the focus detection pixel in the first area and the focus detection pixel in the second area including the first area and performing a focus detection calculation;
An imaging apparatus comprising: a focus adjustment unit that performs focus adjustment of an imaging optical system according to a result of a focus detection calculation calculated by the control unit. The control means includes
The information of the effective image area of the imaging optical system, the area information of the focus detection pixel, and the information of the first area are obtained, the detection length necessary for the focus detection calculation is calculated, and used for focus detection. Area setting means for setting a focus detection area by defining position information of focus detection pixels;
Signal extraction means is provided for acquiring position information of the focus detection pixel from the area setting means, and extracting a signal of the focus detection pixel of the focus detection area set by the area setting means from an output signal of the image sensor. The imaging apparatus according to claim 1.   The imaging apparatus according to claim 2, wherein the area setting unit sets the focus detection area by determining whether or not a signal of the focus detection pixel located outside the first area is used. .   4. The imaging apparatus according to claim 2, wherein the control unit updates information on an effective image area of the imaging optical system when a magnification position or a focus position of the imaging optical system is changed. 5. .   The area setting unit sets the focus detection area using information on a focal length, a diaphragm diameter, and a focusable area of the imaging optical system when reading a signal of the focus detection pixel located outside the first area. The imaging apparatus according to claim 2 or 3, wherein   The control means further acquires a focus detection pixel signal of the second region from the first focus detection region when focus detection is performed by acquiring a focus detection pixel signal of the first region, and performs focus detection. The imaging apparatus according to claim 1, wherein focus detection calculation is performed by changing to a second focus detection region in the case of performing.   The first focus detection region and the second focus detection region wider than the first focus detection region are regions where a focus detection center point in cross focus detection is located and are within the first region. The imaging device according to claim 6. A control method executed by an imaging apparatus that includes an imaging element having a focus detection pixel that outputs a focus detection signal by phase difference detection, and that acquires a signal from the imaging pixel in the first region and outputs a captured image during crop photography. There,
Obtaining a signal from a focus detection pixel in the first region and a focus detection pixel in a second region including the first region, and performing a focus detection calculation by a control unit;
A method for controlling an imaging apparatus, comprising: a step of adjusting a focus of an imaging optical system by a focus adjustment unit according to a result of a focus detection calculation calculated by the control unit.

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