JP6347581B2 - Focus detection apparatus and control method thereof - Google Patents

Description

The present invention relates to a focus detection apparatus and a control method thereof .

  As one of autofocus (AF) methods mounted on an imaging apparatus such as a camera, there is a phase difference detection method (hereinafter referred to as phase difference AF). In the phase difference AF, the light beam that has passed through the exit pupil of the photographing lens is divided into two, and the two divided light beams are received by a set of focus detection sensors. Then, by detecting the shift amount of the signal output according to the received light amount, that is, the relative positional shift amount in the beam splitting direction (hereinafter referred to as the image shift amount), the shift amount in the focus direction of the photographing lens ( Hereinafter, the defocus amount is obtained.

  Patent Document 1 divides a photoelectric conversion unit of a pixel of an image sensor into two parts to give a pupil division function, performs focus detection by individually processing the output of the divided photoelectric conversion unit, and is divided into two parts. A focus detection device that uses the combined calculation force of the photoelectric conversion unit as an imaging signal is disclosed. Further, Patent Document 2 discloses a camera that performs phase difference detection AF based on the result of face detection, and selects a focus detection area according to the face detection state for each scene to be shot.

JP 2001-305415 A JP 2007-286255 A

  The focus detection device disclosed in Patent Document 1 does not consider which position in the imaging angle of view the focus detection area (focus detection area) is set to. In the configuration in which the photoelectric conversion unit of the pixel of the image sensor is divided into two, it is possible to arbitrarily provide a focus detection region, so it is necessary to set a focus detection region suitable for the subject. In addition, the camera disclosed in Patent Document 2 has a focus detection area at the face or eye position when a face is detected as a subject, when the detected face is small, or when it is not at the center of the imaging angle of view. In some cases, the focus adjustment process using the result of the phase difference AF cannot be executed.

An object of the present invention is to provide a focus detection apparatus and a control method thereof that perform appropriate focus detection according to the position and size of a main subject using an image sensor having a photoelectric conversion unit divided into a plurality of parts.

A focus detection apparatus according to an embodiment of the present invention is an imaging device that includes a plurality of photoelectric conversion elements for one microlens, and the microlenses are two-dimensionally arranged, and outputs an image signal. An image sensor, detection means for detecting a main subject area within a shooting angle of view, setting means for setting a focus detection area for acquiring an image signal used for focus detection, and two images obtained from image signals in the focus detection area Control means for executing a focus detection process based on the image shift amount of the image, and the focus detection area includes a search area that is a range corresponding to an image shift amount when calculating the image shift amount of the two images. A reference area set based on a position and a size of the main subject area , and when the size of the main subject area is larger than a predetermined size, the search area is the predetermined area Less than size Than if rather come large, the reference area has a smaller proportion to the size of the main subject region than in the case of less magnitude the predetermined.

According to the focus detection apparatus of one embodiment of the present invention , it is possible to perform appropriate focus detection according to the position and size of the main subject using an imaging device having a plurality of photoelectric conversion units.

It is a figure which shows the structural example of the imaging device of a present Example. It is a flowchart explaining the operation example of an imaging device. It is a figure explaining the structural example of an image pick-up element. It is a figure which shows the pupil of a photographic lens when it sees from an image sensor. It is a figure explaining an A image signal and a B image signal. It is a figure explaining a correlation calculation. It is a figure explaining the example of the conversion process from the image shift amount to the defocus amount. It is a figure explaining a focus detection area. 6 is a flowchart for describing focus detection region setting processing according to the first exemplary embodiment. It is a flowchart explaining the focus detection process in a present Example. It is a flowchart explaining the focus control process of a present Example. It is a figure explaining a focus detection area. FIG. 10 is a diagram illustrating focus detection region setting processing in the second embodiment.

This embodiment will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.
Example 1
FIG. 1 is a diagram illustrating a configuration example of the imaging apparatus according to the present embodiment. The imaging apparatus 100 is a video camera or a digital still camera that can shoot a subject and record moving image or still image data on various media such as a tape, a solid-state memory, an optical disk, and a magnetic disk, but is not limited thereto. It is not something. Each unit in the imaging apparatus 100 is connected via a bus 160. Each unit is controlled by a main CPU 151 (central processing unit).

  The imaging apparatus 100 is equipped with a focus detection apparatus that performs phase difference type focus detection using an imaging element including a plurality of photoelectric conversion elements sharing one microlens. That is, the imaging device includes first and second photoelectric conversion units that generate image signals by photoelectrically converting light beams that have passed through different regions of the exit pupil of the imaging optical system with respect to one microlens. Having a pixel portion. The focus detection apparatus of the present embodiment includes an imaging apparatus (imaging apparatus body) configured to be able to acquire an optical image obtained via an imaging optical system (imaging lens), and an imaging device that can be attached to and detached from the imaging apparatus body. The present invention is applied to an imaging system that includes an optical system. However, the present embodiment is not limited to this, and can be applied to an imaging apparatus in which an imaging optical system is integrally provided.

  The photographing lens 101 (lens unit) includes a fixed first group lens 102, a zoom lens 111, a diaphragm 103, a fixed third group lens 121, and a focus lens 131. The diaphragm control unit 105 adjusts the light amount at the time of shooting by adjusting the aperture diameter of the diaphragm 103 by driving the diaphragm 103 via the diaphragm motor 104 in accordance with a command from the main CPU 151.

  The zoom control unit 113 changes the focal length by driving the zoom lens 111 via the zoom motor 112. The focus control unit 133 controls the focus adjustment state by driving the focus lens 131 via the focus motor 132. The focus lens 131 is a focus adjustment lens. The focus lens 131 is simply illustrated as a single lens in FIG. A subject image formed on the image sensor 141 via these optical members (the photographing lens 101) is converted into an electric signal by the image sensor 141.

  The imaging element 141 is a photoelectric conversion element that performs photoelectric conversion of a subject image (optical image) into an electrical signal. In the imaging device 141, two photoelectric conversion elements (light receiving regions) are arranged in each of the light receiving elements of m pixels in the horizontal direction and n pixels in the vertical direction as described later. An image formed on the imaging element 141 and subjected to photoelectric conversion is arranged as an image signal (image data) by the imaging signal processing unit 142.

  The phase difference AF processing unit 135 uses image signals (signal values) individually output from two photoelectric conversion elements (first photoelectric conversion element and second photoelectric conversion element) to divide light from the subject. An image shift amount in the division direction of the obtained image is detected (calculated). In other words, the phase difference AF processing unit 135 performs a correlation operation using signal values obtained independently from each of the first photoelectric conversion element and the second photoelectric conversion element, and calculates an image shift amount. It is. The phase difference AF processing unit 135 is a defocus amount calculation unit that calculates a shift amount (defocus amount) in the focus direction of the photographing lens 101 based on the detected image shift amount. Note that the scope of application of the present invention is not limited to the case where there are two photoelectric conversion elements included in the imaging element. The present invention is applicable when the imaging device includes an arbitrary number of photoelectric conversion elements of two or more.

  The defocus amount is calculated by multiplying the image shift amount by a coefficient (conversion coefficient). Each operation of the image shift amount calculation unit and the defocus amount calculation unit is performed based on a command from the main CPU 151. Further, at least a part of these operations may be executed by the main CPU 151 or the focus control unit 133. Further, the area of the image signal sent to the phase difference AF processing unit 135 is determined by the main CPU 151.

  The phase difference AF processing unit 135 outputs the calculated shift amount (defocus amount) to the focus control unit 133. The focus control unit 133 determines a drive amount for driving the focus motor 132 based on the shift amount of the photographing lens 101 in the focus direction. AF control is realized by the movement control of the focus lens 131 by the focus control unit 133 and the focus motor 132. The focus detection apparatus of the present embodiment is realized by the main CPU 151, the image sensor 141, the image signal processor 142, and the phase difference AF processor 135 described above.

  Image data output from the imaging signal processing unit 142 is sent to the imaging control unit 143 and temporarily stored in a RAM (Random Access Memory) 154. The image data stored in the RAM 154 is compressed by the image compression / decompression unit 153 and then recorded on the image recording medium 157. In parallel with this processing, the image data stored in the RAM 154 is sent to the image processing unit 152.

  The image processing unit 152 processes an image signal obtained using the addition signal of the first photoelectric conversion element and the second photoelectric conversion element. For example, the image processing unit 152 performs reduction / enlargement processing to an optimum size for image data. The image data processed to the optimum size is sent to the monitor display 150 and displayed as an image. Therefore, the operator can observe the captured image in real time. Note that the monitor display 150 displays the captured image for a predetermined time immediately after the image is captured, so that the operator can check the captured image. The main CPU 151 functions as a detection unit that refers to the image data temporarily stored in the RAM 154 and detects the main subject within the shooting angle of view. The main CPU 151 detects a face area as a main subject using a known face recognition technique, for example.

  The operation unit 156 (operation switch) is used for an operator to give an instruction to the imaging apparatus 100. An operation instruction signal input from the operation unit 156 is sent to the main CPU 151 via the bus 160. The battery 159 is appropriately managed by the power management unit 158, and stably supplies power to the entire imaging apparatus 100. The flash memory 155 stores a control program necessary for the operation of the imaging apparatus 100. When the imaging apparatus 100 is activated by the operation of the operator (when the power supply is turned off from the power-off state), the control program stored in the flash memory 155 is read (loaded) into a part of the RAM 154. The main CPU 151 controls the operation of the imaging apparatus 100 according to a control program loaded in the RAM 154.

FIG. 2 is a flowchart for explaining an operation example of the imaging apparatus. Each step in FIG. 2 is performed based on an instruction from the main CPU 151.
First, when the power of the imaging apparatus 100 is turned on, the main CPU 151 starts calculation (control) (step S201). Subsequently, the flags and control variables of the imaging apparatus 100 are initialized (step S202). Then, the main CPU 151 moves an optical member (imaging optical member) such as the focus lens 131 to the initial position (step S203).

  Next, the main CPU 151 determines whether or not a power OFF operation has been performed by the operator (whether there is a power OFF operation) (step S204). If a power OFF operation has been performed, the process proceeds to step S205. If the power OFF operation has not been performed, the predetermined process proceeds to step S207. In step S205, the main CPU 151 moves the imaging optical member to the initial position and performs post-processing such as clearing various flags and control variables in order to turn off the power of the imaging apparatus 100 (step S205). Then, the processing (control) of the imaging device 100 is terminated (step S206).

  On the other hand, in step S207, the main CPU 151 performs focus detection processing. Subsequently, the focus control unit 133 drives the focus lens 131 with the driving direction, speed, and position determined in the focus detection process of step S207, and moves the focus lens 131 to a desired position (step S208).

  Next, in step S209, the image sensor 141 photoelectrically converts the subject image (imaging process). Further, the imaging signal processing unit 142 performs predetermined processing (image processing) on the subject image subjected to photoelectric conversion, and outputs an image signal.

  Next, the main CPU 151 detects whether or not the recording button (operation unit 156) has been pressed by the operator, and determines whether or not recording is in progress (step S210). If not, the process returns to step S204. If recording is in progress, the process proceeds to step S211. In step S <b> 211, the image signal (image data) output from the imaging signal processing unit 142 is compressed by the image compression / decompression unit 153 and recorded on the image recording medium 157. Then, the process returns to step S204, and the above steps are repeated.

FIG. 3 is a diagram illustrating a configuration example of the image sensor.
With reference to FIG. 3, the phase difference detection method in a present Example is demonstrated. FIG. 3A shows a configuration (cross section) of a pixel of an image sensor 141 having a pupil division function. The photoelectric conversion element 30 is divided into two photoelectric conversion elements 30-1 (first photoelectric conversion element) and photoelectric conversion element 30-2 (second photoelectric conversion element) per pixel, and has a pupil division function. Have. The microlens 31 (on-chip microlens) has a function of efficiently collecting light on the photoelectric conversion element 30, and is arranged so that the optical axis is aligned with the boundary between the photoelectric conversion elements 30-1 and 30-2. Further, a planarizing film 32, a color filter 33, a wiring 34, and an interlayer insulating film 35 are provided inside one pixel.

  FIG. 3B is a partial configuration diagram (plan view) of the image sensor 141. The imaging element 141 is formed by arranging a plurality of pixels each having the configuration shown in FIG. In order to capture an image, R (red), G (green), and B (blue) color filters 33 are alternately arranged in each pixel, and a set of pixel blocks 40, 41, and 42 is arranged with four pixels. As a result, a so-called Bayer array is formed. In FIG. 3B, “1” or “2” shown below each of R, G, and B is a numerical value that represents each of the photoelectric conversion elements 30-1 and 30-2.

  FIG. 3C is an optical principle diagram of the image sensor 141. FIG. 3C illustrates part of a cross section obtained by cutting along line AA in FIG. The image sensor 141 is disposed on the planned image plane of the photographic lens 101. Due to the action of the microlens 31, the photoelectric conversion elements 30-1 and 30-2 are configured to receive a pair of light beams that have passed through different positions (regions) of the pupil (exit pupil) of the photographing lens 101, respectively. Yes. The photoelectric conversion element 30-1 mainly receives a light beam that passes through the right position in FIG. On the other hand, the photoelectric conversion element 30-2 mainly receives a light flux that passes through the left position of the pupil of the photographing lens 101 in FIG.

  FIG. 4 is a diagram illustrating the pupil of the photographing lens when viewed from the image sensor. The pupil 50 has a sensitivity region (A image pupil) 51-1 of the photoelectric conversion element 30-1 and a sensitivity region (B image pupil) 51-2 of the photoelectric conversion element 30-2. Reference numerals 52-1 and 52-2 represent barycentric positions of the A image pupil and the B image pupil, respectively.

  The imaging apparatus 100 can generate an image signal by adding the outputs of two photoelectric conversion elements in which color filters of the same color are arranged in the same pixel. In addition, when performing the focus detection process, the imaging apparatus acquires a focus detection signal of one pixel by integrating outputs from the photoelectric conversion elements corresponding to the photoelectric conversion elements 30-1 in one pixel block. Then, the imaging apparatus 100 can generate the A image signal by continuously acquiring this signal in the horizontal direction like the pixel blocks 40, 41, and 42.

  Similarly, the imaging apparatus 100 acquires a focus detection signal for one pixel by integrating outputs from the photoelectric conversion elements corresponding to the photoelectric conversion element 30-2 in one pixel block. The imaging apparatus 100 can generate a B image signal by continuously acquiring this signal in the horizontal direction. A pair of phase difference detection signals is generated from the A image signal and the B image signal.

  FIG. 5 is a diagram for explaining the A image signal and the B image signal. In this example, the A image signal and the B image signal are collectively described as an “image signal”. In FIG. 5, the vertical axis indicates the level of the image signal, and the horizontal axis indicates the pixel position. In FIG. 5, a graph curve W1 indicates an A image signal, and a graph curve W2 indicates a B image signal. The image shift amount X of the generated pair of phase difference detection signals changes according to the imaging state (focused state, front pin state, or rear pin state) of the photographic lens 101. When the photographing lens 101 is in focus, the image shift amount between the two image signals is eliminated. On the other hand, in the front pin state or the rear pin state, image shift amounts in different directions occur. The image shift amount has a fixed relationship with the distance between the position where the subject image is formed by the photographing lens 101 and the upper surface of the microlens, the so-called defocus amount.

FIG. 6 is a diagram for explaining the correlation calculation.
The main CPU 151 obtains a first image and a second image from the first and second photoelectric conversion units corresponding to the focus detection area, respectively. In this example, an image signal related to the first image is an A image signal, and an image signal related to the second image is a B image signal. The main CPU 151 compares the first image with the second image while shifting the second image. Thereby, the main CPU 151 calculates a correlation value between the two images, and calculates an image shift amount between the two images based on the calculated correlation value. The main CPU 151 calculates a difference between positions at which the correlation value is maximized as an image shift amount. Therefore, the correlation calculation requires the number of pixels for comparing two image signals and calculating the correlation value and the sum of the number of pixels corresponding to the shift amount. Hereinafter, the pixel range for calculating the correlation value is referred to as a reference range. A pixel range corresponding to the shift amount is described as a search range.

  The main CPU 151 determines the defocus amount of the taking lens 101 based on the calculated image shift amount. Then, the main CPU 151 calculates a lens driving amount that brings the photographing lens 101 into a focused state based on the obtained defocus amount, and performs focus adjustment according to the calculated lens driving amount.

FIG. 7 is a diagram for explaining an example of conversion processing from the image shift amount calculated by the correlation calculation to the defocus amount.
FIG. 7A shows an optical system including the photographing lens 101 and the image sensor 141. A focus detection surface position p1 is located on the optical axis OA at the position p0 of the planned imaging plane with respect to the subject 70. FIG. 7B shows an image signal at a position p1 on the focus detection surface. The relationship between the image shift amount and the defocus amount is determined according to the optical system.

  The defocus amount can be calculated by multiplying the image shift amount X by a predetermined coefficient K (conversion coefficient). The coefficient K is calculated based on the barycentric positions of the A image pupil and the B image pupil. When the position p1 of the focus detection surface moves to the position p2, the image shift amount changes according to the similarity between the triangles at the positions p0, q2, and q3 and the triangles at the positions p0, q2 ', and q3'. Therefore, it is possible to calculate the defocus amount at the position p2 on the focus detection surface. Based on the defocus amount, the main CPU 151 calculates the position of the focus lens 131 for obtaining a focused state with respect to the subject.

FIG. 8 is a diagram illustrating the focus detection area.
The focus detection area is an area from which an image signal used for focus detection is read from the pixel portion of the image sensor. The main CPU 151 functions as a control unit that executes focus detection processing based on the image shift amount of the two images obtained from the image signal read from the focus detection area.

  A focus detection area 81 shown in FIG. 8 is set based on a detection frame based on face recognition. Specifically, the main CPU 151 sets the focus detection area based on the position and size of the detected main subject (face). Thereby, when a face is detected, focus detection can be performed on the position of the face in the imaging angle of view 80.

  FIG. 8A shows a focus detection region when a face is detected small. When the face is detected small, it is assumed that the person who is the subject is at a position away from the imaging device, so it is necessary to set the focus detection area so as to capture the face reliably. Therefore, the imaging apparatus aligns the center of the focus detection area 81 with the center position of the detected face, and sets the reference area 82 in the correlation calculation to the same size as the face frame.

  FIG. 8B shows a focus detection area in the case where a large face is detected. When a large face is detected, it is assumed that the person who is the subject is at a short distance from the imaging apparatus. Further, when photographing a face up, it is necessary to set a focus detection area so as to catch the eye in order to focus on the eye. Therefore, the imaging apparatus sets the center of the focus detection area 81 to the detected eye position, sets the reference area 82 in the correlation calculation small, and sets the search area 83 large.

  Note that when the imaging apparatus generates a focus detection signal for one pixel, line addition may be performed in the vertical direction within an appropriate range. The size of the focus detection area 81 including the reference area 82 and the search area 83 is variable depending on the size of the detected face, but an upper limit and a lower limit may be provided. Further, as shown in FIGS. 8A and 8B, a plurality of focus detection areas are set on the imaging angle of view 80, and the area around the focus detection area 81 provided on the eyes or the face is auxiliary. The focus detection area 84 may be set. In this embodiment, the setting of the focus detection area for the right eye has been described, but the same applies to the left eye.

FIG. 9 is a flowchart illustrating the focus detection area setting process according to the first embodiment. Each step in FIG. 9 is executed by the main CPU 151.
First, focus detection area setting is started (step S901). The main CPU 151 substitutes the initial value of the size of the focus detection area with the reference area Sr as 200 pixels and the search area Ss as 100 pixels (step S902).

  Next, the main CPU 151 acquires a face detection position Xf and a face detection size Sf as a result of the face detection process (step S903). When a plurality of faces are detected, the position and size are acquired for the face that is the main subject based on the result of face recognition. Then, the main CPU 151 determines whether or not the face size is larger than a predetermined value (threshold value) (step S904).

  When the face size Sf is larger than the predetermined value, the main CPU 151 acquires the eye position Xe (step S905). Then, the main CPU 151 resets the reference area Sr to 100 pixels and the search area Ss to 200 pixels (step S906). That is, the main CPU 151 sets the range of the reference area to be smaller than the size of the range set in step S902. The main CPU 151 sets the range of the search area to be larger than the size of the range set in step S902. Subsequently, the focus detection area is set in a range of Xe− (Sr + Ss) / 2 to Xe + (Sr + Ss) / 2 (step S907), and the process is terminated (step S912).

  On the other hand, if it is determined in step 904 that the face size Sf is smaller than the predetermined value, the main CPU 151 sets the reference area Sr as the face size Sf (step S908). In this example, the main CPU 151 sets the reference area Sr to a size equal to the face size, but the main CPU 151 may set the reference area Sr to a size larger than the face size. Subsequently, the main CPU 151 determines whether or not the reference area Sr is larger than a predetermined value (step S909). In this example, the predetermined value is 100 pixels.

  When the reference area Sr is 100 pixels or less, the main CPU 151 substitutes 100 pixels for the reference area Sr (step S910). That is, the main CPU 151 sets the reference area to the lower limit value. Then, the process proceeds to step S911.

  When the reference area Sr is larger than 100 pixels, the main CPU 151 sets the focus detection area to a range of Xf− (Sr + Ss) / 2 to Xf + (Sr + Ss) / 2 (step S911). That is, the main CPU 151 sets the center of the focus detection area to the position of the center of the face. In addition, the numerical value in a present Example is an example.

  FIG. 10 is a flowchart for explaining the focus detection process in this embodiment. Each step in FIG. 10 is executed by the main CPU 151, the phase difference AF processing unit 135, and the focus control unit 133, and corresponds to step S207 in FIG.

  First, focus detection is started (step S1001). Subsequently, the main CPU 151 sets the focus detection area described with reference to FIG. 9 (step S1002). Then, the image sensor 141 accumulates charges (step S1003).

  Next, the main CPU 151 determines whether or not charge accumulation has been completed (step S1004). If the charge accumulation of the image sensor 141 has not been completed, the process returns to step S1003. When the charge accumulation is completed, the main CPU 151 reads out the pixel value of the image signal for the focus detection area 81 shown in FIG. 8 (step S1005).

  Next, the main CPU 151 determines whether or not reading for a predetermined number of pixels in the focus detection area 81 has been completed (step S1006). If reading for the predetermined number of pixels has not been completed, the process returns to step S1005. If reading for a predetermined number of pixels is completed, the process advances to step S1007.

  Next, the focus control unit 133 performs pre-correction processing on the acquired image signal (step S1007). The pre-correction processing includes correction processing for the read image signal and image signal filtering processing such as an averaging filter and an edge enhancement filter.

  Then, the main CPU 151 performs a correlation calculation to calculate a shift amount at which the correlation is the highest (step S1008). Specifically, the main CPU 151 calculates the correlation value while shifting the pixels of the A image signal and the B image signal in the focus detection area 81, and the difference between the positions where the correlation value is maximized is set as the image shift amount X. calculate. When calculating the correlation value, the two image signals are overlapped, the corresponding signals are compared with each other, and the accumulation of the smaller value is obtained. The accumulation of the larger value may be acquired. Moreover, you may acquire the difference of these values. Accumulation is an index indicating correlation, and when the accumulation of the smaller value is acquired, the largest value is when the correlation is high.

  When the accumulation of the larger value is acquired or when the difference is acquired, the time when this value is the smallest is the time when the correlation is high. After calculating the shift amount with the highest correlation, an interpolation operation is performed using the correlation value between the shift amount and the preceding and subsequent shift amounts, and an interpolation value within one shift is calculated. The sum of the shift amount and the interpolation value is the image shift amount X. As described above, the main CPU 151, the focus control unit 133, or the phase difference AF processing unit 135 as the image shift amount calculation unit is obtained independently from each of the first photoelectric conversion element and the second photoelectric conversion element. An image shift amount is calculated by performing correlation calculation using the obtained signal values.

  Next, the main CPU 151 evaluates the reliability of the calculated image shift amount X (step S1009). The reliability is calculated based on the contrast of the image signal, the degree of coincidence between the two image signals, and the like. Subsequently, the main CPU 151 determines whether or not the reliability is greater than a predetermined threshold value, that is, whether or not the reliable image shift amount X has been obtained (step S1010). When the reliability is larger than the threshold, the main CPU 151 calculates the defocus amount Def by multiplying the deviation amount X by the corrected coefficient K (by the relational expression Def = K × X) (step S1011). . Then, the focus detection process ends. When the reliability is equal to or lower than the threshold value, that is, when a reliable image shift amount cannot be detected, the main CPU 151 does not perform focus detection.

FIG. 11 is a flowchart for explaining the focus control process of this embodiment.
When the focus control method is started, the main CPU 151 performs a predetermined calculation. Then, the focus control unit 133 controls the focus motor 132 in accordance with an instruction from the main CPU 151. Each step shown in FIG. 11 is executed by the main CPU 151 and the focus control unit 133, and corresponds to step S208 in FIG.

  First, focus control is started (step S1101). Subsequently, the focus control unit 133 acquires the defocus amount calculated in the focus detection process described with reference to FIG. 10 (step S1102). Then, the focus control unit 133 calculates a drive amount (lens drive amount) of the focus lens 131 based on the defocus amount (step S1103). Calculation of the lens driving amount includes calculation of the lens driving direction and speed.

  Next, the main CPU 151 determines whether or not the absolute value of the defocus amount is equal to or less than a predetermined value (step S1104). If the absolute value of the defocus amount is not less than or equal to the predetermined value, the main CPU 151 determines that the position of the focus lens 131 is not the in-focus position (in-focus), and the process proceeds to step S1105. Then, the main CPU 151 drives the focus lens 131 according to the lens driving amount calculated in step S1103 (step S1105), and the process ends. Thereafter, focus detection and focus lens driving are repeated in accordance with the processing shown in the flowchart shown in FIG.

  On the other hand, when the absolute value of the defocus amount is equal to or less than the predetermined value, the main CPU 151 determines that the focus lens position is in focus. Then, the main CPU 151 stops lens driving (step S1106) and proceeds to step S1107. Thereafter, focus detection is performed according to the flowchart shown in FIG. 2, and when the defocus amount again exceeds a predetermined value, the focus lens 131 is driven.

  As described above, the imaging apparatus including the focus detection apparatus according to the present exemplary embodiment sets the focus detection area (reference area and search area) according to the face position when a face is detected at the imaging angle of view. As a result, focus detection can be performed at any position in the imaging angle of view of the face as the main subject, and the speed of focus adjustment can be increased by using the phase difference AF result for the main subject. Is possible. In addition, by changing the size of the reference area and the search area according to the size of the face, the face is the focus detection area when the face is small, and the focus of the eyes is detected when the face is large. The area can be switched adaptively according to the shooting situation.

(Example 2)
In the second embodiment, the imaging apparatus sets the focus detection region based on the position and size of the face detection frame and the detected eye distance of the face. In the second embodiment, the same contents as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  In step S904 in FIG. 9 described above, when the face size Sf is larger than a predetermined value, the position of the focus detection area is aligned with the position of the right eye or the left eye, and the search area Ss is set to be large. However, as shown in FIG. 12A, for example, even when the face size is larger than a predetermined size, the focus detection area of one eye covers the other eye depending on the size of the detected face. May end up. When the main CPU 151 performs a correlation calculation on this focus detection area, it is not known whether the target of correlation is the right eye or the left eye. Therefore, in the second embodiment, when the center of the focus detection area is set to the first eye, the main CPU 151 executes the following process when the focus detection area covers the second eye. As shown in FIG. 12B, the main CPU 151 resets the reference area 82 so that both the first and second eyes enter the focus detection area, and the face in which the center of the focus detection area is detected. To match.

  FIG. 13 is a flowchart illustrating focus detection region setting processing according to the second embodiment. Steps S1301 to S1304 in FIG. 13 are the same as steps S901 to S904 in FIG.

  When the face size Sf is larger than the predetermined value, in step S1305, the main CPU 151 obtains the right eye position Xe1 and the left eye position Xe2 (step S1305). In the imaging field angle 80, the right side is the positive direction of X, and Xe2> Xe1.

  Next, the main CPU 151 resets the reference area Sr to 100 pixels and the search area Ss to 200 pixels (step S1306). Then, the main CPU 151 determines whether the focus detection area aligned with the position of the right eye includes the left eye (step S1307). Specifically, the main CPU 151 determines whether Xe1 + (Sr + Ss) / 2 <Xe2. If Xe1 + (Sr + Ss) / 2 <Xe2, the main CPU 151 determines that the focus detection area aligned with the right eye does not include the left eye, and the process advances to step S1308. If Xe1 + (Sr + Ss) / 2 ≧ Xe2, the main CPU 151 determines that the focus detection area aligned with the position of the right eye includes the left eye, and the process advances to step S1309.

  In step S1308, the main CPU 151 sets the focus detection area in the range of Xe− (Sr + Ss) / 2 to Xe + (Sr + Ss) / 2 (step S1308), and the process ends (step S1315).

  In step S1309, the main CPU 151 resets the reference area Sr to (Xe2-Xe1) + α and the search area Ss to 150 pixels (step S1309). Here, Xe2-Xe1 represents the distance between the eyes of the face to be the subject, and α is a margin for setting the reference area Sr slightly larger than the distance between the eyes. Subsequently, the main CPU 151 resets the focus detection area to a range of Xf− (Sr + Ss) / 2 to Xf + (Sr + Ss) / 2 (step S1314). As a result, if the focus detection area includes the other eye when the center of one eye is aligned, the reference area 82 is reset so that both eyes enter, and the center of the focus detection area is detected. It is possible to match the face.

  On the other hand, the processing executed in step 1304 when the face size Sf is smaller than the predetermined value (the processing in steps S1311 to S1314) is the same as the processing in steps S908 to S911 in FIG. In addition, the numerical value in a present Example is an example.

  In this example, the description has been given on the assumption that the eye position can also be detected at the time of face detection. However, the present invention is not limited to this, and the main CPU 151 may estimate the eye position from the size of the face. The main CPU 151 may estimate the eye position from the obtained image signal.

  As described above, in this embodiment, by providing the focus detection area based on the detected distance between the eyes of the face, it is possible to clarify the correlation target in the correlation calculation.

  In each of the above embodiments, a method has been described in which the main subject is a face detected by face detection, and the focus detection area is set based on the position and size of the face. However, the present invention is not limited to this. For example, the present invention can be applied if a subject such as a pet or other object can be detected by a recognition technique and its position and size can be detected.

  According to each of the above embodiments, in the focus detection device capable of imaging and focus detection using the two-divided photoelectric conversion unit, when a face is detected at the imaging angle of view, the position of the face, the size, or A focus detection area is set according to the interval between eyes. As a result, focus detection can be performed at any position in the imaging angle of view of the face that is the main subject. Therefore, according to each of the embodiments described above, it is possible to provide a focus detection device, an imaging device, an imaging system, and a focus detection method capable of performing focus detection on the main subject.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. In this case, the program and the storage medium storing the program constitute the present invention.

101 Shooting Lens 135 Phase Difference AF Processing Unit 151 CPU

Claims (9)

An image sensor that has a plurality of photoelectric conversion elements for one microlens, and the microlens is two-dimensionally arranged, and outputs an image signal;
Detecting means for detecting a main subject area within a shooting angle of view;
Setting means for setting a focus detection region for acquiring an image signal used for focus detection;
Control means for executing a focus detection process based on an image shift amount of two images obtained from an image signal of the focus detection area;
The focus detection area includes a search area that is a range corresponding to an image shift amount when calculating an image shift amount between the two images, and a reference area that is set based on the position and size of the main subject area. Including
If the size of the main subject region is larger than the size that is determined in advance, the search region, the rather larger can than below the predetermined magnitude, the reference region size the predetermined A focus detection apparatus characterized in that a ratio with respect to the size of the main subject region is smaller than that in the case of the following .   The control means acquires a first image and a second image based on output signals from the first and second photoelectric conversion units of the image sensor, and shifts the second image, respectively. The correlation value between the two images is calculated by comparing the first image with the second image, and the image shift amount between the two images is calculated based on the calculated correlation value. The focus detection apparatus according to claim 1, wherein The focus detection apparatus according to claim 1, wherein the detection unit detects a face area as the main subject area .   When the detected face area is larger than a predetermined threshold, the setting means sets the center of the focus detection area to the position of the eye included in the face area, and the detected face area 4. The focus detection apparatus according to claim 3, wherein when the threshold value is not larger than the threshold value, a center of the focus detection area is set to a center position of the face area.   The setting means sets the range of the reference area included in the focus detection area to a size larger than the size of the face area when the detected face area is not larger than a threshold value. The focus detection apparatus according to claim 3 or 4.   When the setting means sets the center of the focus detection area to the position of the first eye, and the focus detection area includes the second eye, the center of the focus detection area is set to the position of the center of the face area. The reference area is reset so that the reference area included in the reset focus detection area includes the first and second eyes. The focus detection apparatus of any one of Claims. An imaging device having a plurality of pixels capable of photoelectrically converting a light beam that has passed through different pupil regions of the imaging optical system and outputting a pair of focus detection signals;
Detecting means for detecting a main subject area within a shooting angle of view;
Setting means for setting a focus detection region for acquiring an image signal used for focus detection;
Control means for executing a focus detection process based on an image shift amount of two images obtained from an image signal of the focus detection area;
The focus detection area includes a search area that is a range corresponding to an image shift amount when calculating an image shift amount between the two images, and a reference area that is set based on the position and size of the main subject area. Including
If the size of the main subject region is larger than the size that is determined in advance, the search region, the rather larger can than below the predetermined magnitude, the reference region size the predetermined A focus detection apparatus characterized in that a ratio with respect to the size of the main subject region is smaller than that in the case of the following . A method of controlling a focus detection apparatus having an image sensor that has a plurality of photoelectric conversion elements for one microlens, and the microlens is two-dimensionally arranged and outputs an image signal. There,
A detection step of detecting a main subject area within a shooting angle of view;
A setting step for setting a focus detection region for acquiring an image signal used for focus detection;
A control step of performing a focus detection process based on an image shift amount of two images obtained from an image signal of the focus detection region,
The focus detection area includes a search area that is a range corresponding to an image shift amount when calculating an image shift amount between the two images, and a reference area that is set based on the position and size of the main subject area. Including
If the size of the main subject region is larger than the size that is determined in advance, the search region, the rather larger can than below the predetermined magnitude, the reference region size the predetermined A control method for a focus detection apparatus, wherein a ratio to the size of the main subject area is smaller than that in the case of the following . A method for controlling a focus detection apparatus including an imaging element having a plurality of pixels capable of photoelectrically converting a light beam that has passed through different pupil regions of an imaging optical system and outputting a pair of focus detection signals,
A detection step of detecting a main subject area within a shooting angle of view;
A setting step for setting a focus detection region for acquiring an image signal used for focus detection;
A control step of performing a focus detection process based on an image shift amount of two images obtained from an image signal of the focus detection region,
The focus detection area includes a search area that is a range corresponding to an image shift amount when calculating an image shift amount between the two images, and a reference area that is set based on the position and size of the main subject area. Including
If the size of the main subject region is larger than the size that is determined in advance, the search region, the rather larger can than below the predetermined magnitude, the reference region size the predetermined A control method for a focus detection apparatus, wherein a ratio to the size of the main subject area is smaller than that in the case of the following .

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