JP2015087511A - Focus detector, control method for the same, control program and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely execute focus detection by suppressing erroneous detection of an image shift quantity when executing the focus detection through phase difference detection.SOLUTION: A phase difference AF processing unit 135 applies first filter processing to a first image signal and a second image signal with a prescribed first frequency band, and applies second filer processing with a second frequency band higher than the first frequency band. The phase difference AF processing unit obtains each first image shift quantity in the first and second image signals after the application of the first filer processing, obtains each second image shift quantity showing each image shift quantity in the first and second image signals after the application of the second filer processing, selects either one of the first image shift quantity and the second image shift quantity according to whether or not the first image shift quantity is equal to or higher than a reference image shift quantity determined in accordance with a photographing condition, and then calculates a defocus quantity in accordance with the selected image shift quantity.

Description

  The present invention relates to a focus detection apparatus, a control method thereof, a control program, and an imaging apparatus, and more particularly to a focus detection apparatus using a phase difference detection method.

  Conventionally, a so-called phase difference detection method (hereinafter referred to as phase difference AF) is known as one of autofocus (AF) used in an imaging apparatus such as a digital camera or a video camera. 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 detection signal output according to the received light amount, that is, the shift amount of the relative position in the beam splitting direction (hereinafter referred to as the image shift amount), the shift amount in the focusing direction of the photographing lens. (Hereinafter referred to as defocus amount).

  By the way, there is known a focus detection device that performs phase difference AF at high speed without providing a dedicated focus detection sensor by providing the image sensor with the above-described phase difference detection unit (Patent Document 1). reference).

  In Patent Document 1, pupil division is performed by dividing a photoelectric conversion unit provided in a pixel of an image sensor into two, and focus detection is performed by individually processing the output of the divided photoelectric conversion unit. Furthermore, the output of the photoelectric conversion unit divided into two is added to form an image signal.

  Further, a defocus amount obtained by performing a predetermined filter process on the output of the photoelectric conversion unit and a defocus amount obtained without performing a filter process on the output of the photoelectric conversion unit are selectively used. A focus detection apparatus is known (see Patent Document 2).

JP 2001-305415 A JP-A-2-244020

  However, the focus detection apparatus described in Patent Document 1 does not select whether or not to perform filtering on the output of the photoelectric conversion unit when performing focus detection. As a result, depending on the position of the subject, the image is not selected. The amount of deviation may be erroneously detected.

  Moreover, in the focus detection apparatus described in Patent Document 2, it is selected whether or not to perform filter processing on the output of the photoelectric conversion unit, thereby improving the focus detection accuracy. However, it is not determined whether or not to perform filter processing according to subject conditions such as shooting conditions, subject types, and positions thereof. For this reason, focus detection may not be performed accurately depending on the shooting conditions and subject conditions.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a focus detection apparatus, a control method thereof, a control program, and an imaging device capable of accurately performing focus detection while suppressing erroneous detection of an image shift amount when performing focus detection by phase difference detection. To provide an apparatus.

In order to achieve the above object, a focus detection apparatus according to the present invention is obtained from an image pickup device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographic lens including at least a focus lens. A focus detection device that performs focus detection in accordance with a phase difference between one image signal and a second image signal, and a predetermined first frequency band for the first image signal and the second image signal And a second filter in a second frequency band higher than the first frequency band with respect to the first image signal and the second image signal. A second filter means for performing processing, a first image signal subjected to the first filter processing and a first image displacement amount indicating an image displacement amount in the second image signal, and the second image signal. No fu An image shift amount calculating means for obtaining a second image shift amount indicating an image shift amount in the first image signal and the second image signal subjected to the filter processing, and the first image shift amount according to a photographing condition. Whether or not it is equal to or greater than a predetermined reference image displacement amount, and either one of the first image displacement amount and the second image displacement amount is selected as the selected image displacement amount according to the determination result. A selection means to select;
Defocus amount calculating means for calculating a defocus amount indicating a defocus amount of the focus lens in accordance with the selected image shift amount.

  An imaging device according to the present invention includes: an imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through mutually different pupil regions in a photographing lens including at least a focus lens; and And a control means for driving the focus lens along the optical axis of the photographing lens according to the defocus amount obtained by the focus detection device to bring it into a focused state. Features.

  According to the control method of the present invention, a first image signal and a second image obtained from an imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographing lens including at least a focus lens. A focus detection apparatus control method for performing focus detection according to a signal phase difference, wherein the first filter processing is performed in a predetermined first frequency band with respect to the first image signal and the second image signal. A first filtering process step for performing a second filtering process on a second frequency band higher than the first frequency band for the first image signal and the second image signal. A first image shift amount indicating an image shift amount in the first image signal and the second image signal subjected to the first filter processing, and the second filter. An image shift amount calculating step for obtaining a second image shift amount indicating an image shift amount in the processed first image signal and second image signal, and the first image shift amount according to the shooting condition. It is determined whether or not a predetermined reference image shift amount or more, and one of the first image shift amount and the second image shift amount is selected as a selected image shift amount according to the determination result. And a defocus amount calculating step of calculating a defocus amount indicating a defocus amount of the focus lens in accordance with the selected image shift amount.

  A control program according to the present invention includes a first image signal and a second image obtained from an imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographing lens including at least a focus lens. A control program used in a focus detection device that performs focus detection according to a phase difference between signals, wherein a computer included in the focus detection device has a predetermined program for the first image signal and the second image signal. A first filtering step for performing a first filtering process in a first frequency band; and a second frequency higher than the first frequency band for the first image signal and the second image signal. A second filter processing step for performing a second filter processing in a band, and a first image signal and a second image signal on which the first filter processing has been performed. An image for determining a first image shift amount indicating a shift amount and a second image shift amount indicating an image shift amount in the first image signal and the second image signal subjected to the second filter processing. A shift amount calculating step; determining whether the first image shift amount is equal to or greater than a reference image shift amount determined according to a shooting condition; and determining the first image shift amount according to the determination result. And a selection step of selecting one of the second image shift amounts as a selected image shift amount, and a defocus amount calculation for calculating a defocus amount indicating a focus shift of the focus lens according to the selected image shift amount And executing the step.

  According to the present invention, it is determined whether or not the first image shift amount is greater than or equal to the reference image shift amount determined according to the shooting condition, and the first image shift amount and the first image shift amount are determined according to the determination result. One of the two image shift amounts is selected as the selected image shift amount, and a defocus amount indicating the focus shift of the focus lens is calculated according to the selected image shift amount. Accordingly, erroneous detection of the image shift amount can be suppressed, and the focus detection can be accurately performed according to the photographing condition and the subject condition.

It is a block diagram which shows the structure about an example of an imaging device provided with the focus detection apparatus by the 1st Embodiment of this invention. 3 is a flowchart for explaining an example of a photographing operation performed by the camera shown in FIG. 2A and 2B are diagrams for explaining an example of the configuration of the image sensor illustrated in FIG. 1, in which FIG. A top view and (c) are sectional views which followed an AA line shown in (b). It is a figure which shows the pupil of a photographic lens at the time of seeing the direction of a photographic lens from the image pick-up element shown in FIG. It is a figure which shows the focus detection area | region set to the image which the 1st and 2nd image data obtained by the imaging signal process part shown in FIG. 1 show. FIG. 10 is a diagram for explaining another example of generation of an image signal used for focus detection in the pixel array shown in FIG. It is a figure which shows an example of the A image signal and B image signal which are produced | generated by the phase difference AF process part shown in FIG. It is a figure for demonstrating the conversion from the image shift amount performed to the defocus amount by the phase difference AF process part 135 shown in FIG. It is a figure which shows the state after performing a BPF process with respect to A image signal and B image signal, when the focus lens shown in FIG. 1 is in a defocus state. FIG. 6 is a diagram for explaining selection of first and second image shift amounts performed by a phase difference AF processing unit shown in FIG. 1. It is a flowchart for demonstrating the focus detection process shown in FIG. It is a figure for demonstrating an example of A image signal and B image signal at the time of image | photographing the object which is not suitable for correlation calculation, (a) is a figure which shows an example of A image signal and B image signal which have repeatability, (B) is a diagram showing determination of whether or not the subject has repeatability. 3 is a flowchart for explaining an example of a focus control process shown in FIG. 2. It is a figure for demonstrating the A image signal and B image signal which concern on the object which has only the edge image | photographed with the camera provided with the focus detection apparatus by the 2nd Embodiment of this invention, (a) has only an edge. The figure which shows an example of a to-be-photographed object, (b) is a figure which shows the example which performed the 1st filter process about the A image signal and B image signal which concern on the to-be-photographed object shown to (a), (c) is the object shown to (a) It is a figure which shows the example which performed the 2nd filter process about the A image signal and B image signal which concern on. It is a flowchart for demonstrating the focus detection performed with the camera provided with the focus detection apparatus by the 2nd Embodiment of this invention (the 1). It is a flowchart for demonstrating the focus detection performed with the camera provided with the focus detection apparatus by the 2nd Embodiment of this invention (the 2).

  Hereinafter, an example of an imaging apparatus including a focus detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an example of an imaging apparatus including a focus detection apparatus according to the first embodiment of the present invention.

  The illustrated imaging device is, for example, a digital camera (hereinafter simply referred to as a camera), and the camera 100 captures a subject and records moving images or still image data on a recording medium such as a tape, a solid-state memory, an optical disk, or a magnetic disk. Record. The units included in the camera 100 are connected to each other via a bus 160, and these units are controlled by a main CPU (hereinafter simply referred to as CPU) 151 (central processing unit).

  The camera 100 includes an imaging device 141 including a plurality of photoelectric conversion elements (for example, a first photoelectric conversion element and a second photoelectric conversion element) that share one microlens. The focus detection device performs focus detection by a phase difference detection method in accordance with the output of the image sensor 141.

  The camera 100 includes a photographing lens unit (hereinafter simply referred to as a photographing lens) 101. The photographing lens 101 includes a fixed first group lens 102, a zoom lens 111, a diaphragm mechanism (also simply referred to as a diaphragm) 103, and a fixed third group. A lens 121 and a focus lens 131 are provided. The aperture control unit 105 drives and controls the aperture motor (AM) 104 by controlling the aperture motor (AM) 104 under the control of the CPU 151.

  As a result, the aperture diameter of the diaphragm 103 is adjusted, and the amount of light at the time of shooting is adjusted. Under the control of the CPU 151, the zoom control unit 113 drives and controls the zoom motor (ZM) 112 to drive the zoom lens 111 and change the focal length.

  The focus control unit 133 drives and controls a focus motor (FM) 132 under the control of the CPU 151 to drive a focus lens 131 that is a focus adjustment lens to perform focus adjustment. In FIG. 1, the focus lens 131 is simply shown as a single lens, but is usually composed of a plurality of lenses.

  An optical image (also referred to as a subject image) incident through the taking lens 101 is formed on the image sensor 141. The image sensor 141 outputs an electrical signal (analog signal) corresponding to the optical image. The image sensor 141 has a plurality of pixels arranged in a two-dimensional matrix. For example, the image sensor 141 has m pixels arranged in the horizontal direction (row direction) and n pixels (m and n are each an integer of 2 or more) arranged in the vertical direction (column direction). Two photoelectric conversion elements (light receiving regions) are provided.

  An analog signal (an image signal or an imaging signal) that is an output of the imaging element 141 is given to the imaging signal processing unit 142. The imaging signal processing unit 142 performs A / D conversion on the image signal, and then performs predetermined signal processing to generate image data. At this time, the imaging signal processing unit 142 outputs the first and second image data corresponding to the two photoelectric conversion elements and combines (that is, adds) the first and second image data. Generate data.

  The phase difference AF processing unit 135 corresponds to image data corresponding to two photoelectric conversion elements (that is, the first and second photoelectric conversion elements), that is, an image obtained by dividing light from a subject. Accordingly, the image shift amount in the division direction is detected. That is, the phase difference AF processing unit 135 performs correlation calculation using the signal values obtained from the first and second photoelectric conversion elements to calculate the image shift amount.

  Further, the phase difference AF processing unit 135 calculates a shift amount (defocus amount) in the focus direction of the photographing lens 101 based on the image shift amount. This defocus amount is obtained by multiplying the image shift amount by a predetermined coefficient (conversion coefficient). Note that the image shift amount and the defocus amount are calculated under the control of the CPU 151. Further, at least part of the calculation of the image shift amount and the defocus amount may be performed by the CPU 151 or the focus control unit 133.

  The shift amount (that is, the defocus amount) obtained by the phase difference AF processing unit 135 is sent 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, that is, the shift amount of the photographing lens 101 in the focus direction. The focus control unit 133 drives and controls the focus motor 132 according to the drive amount, and performs AF control by moving the focus lens 131 along the optical axis of the photographing lens 101.

  The imaging signal processing unit 142 sends the above-described composite image data to the imaging control unit 143. Then, the imaging control unit 143 temporarily stores the composite image data in a RAM (Random Access Memory) 154. The image compression / decompression unit 153 compresses the composite image data stored in the RAM 154 and records it on the image recording medium 157.

  Note that the imaging control unit 143 performs readout control of the imaging element 141 under the control of the CPU 151.

  The composite image data stored in the RAM 154 is sent to the image processing unit 152. The image processing unit 152 performs predetermined image processing on the composite image data to obtain processed image data. For example, the image processing unit 152 performs a reduction / enlargement process on the composite image data to convert it to an optimal size. Then, the image processing unit 152 displays the image data processed to the optimum size on the monitor display 150 as an image. Thereby, the operator who is a user can observe an image at the time of imaging | photography in real time.

  Immediately after the image is taken, the image is displayed on the monitor display 150 for a predetermined time.

  The operation unit 156 (also referred to as an operation switch) is used when an operator gives various instructions to the camera 100 (that is, the CPU 151). An operation instruction input from the operation unit 156 is sent to the CPU 151 via the bus 160.

  The imaging control unit 143 controls the imaging element 141 under the control of the CPU 151. At this time, the CPU 151 determines the charge accumulation time in the image sensor 141 based on the operation instruction from the operator input from the operation unit 156 or the size of the pixel signal in the composite image data stored in the RAM 154.

  Further, the CPU 151 determines a gain setting value for reading an image signal from the image sensor 141 to the image signal processing unit 142. Then, the imaging control unit 143 controls the imaging element 141 according to the accumulation time and gain setting values determined by the CPU 151.

  The battery 159 is managed by the power management unit 158 and stably supplies power to the entire camera 100. The flash memory 155 stores a control program necessary for the operation of the camera 100.

  When the camera 100 is activated by the operation of the operator (that is, when the power is turned off to shift to the power on state), the control program stored in the flash memory 155 is read (loaded) into a predetermined area of the RAM 154. . The CPU 151 controls the camera 100 according to the control program loaded in the RAM 154.

  FIG. 2 is a flowchart for explaining an example of the photographing operation performed by the camera 100 shown in FIG. The process according to the flowchart shown in the figure is performed under the control of the CPU 151.

  When the power of the camera 100 is turned on, the CPU 151 starts calculation (control). Then, the CPU 151 initializes various flags and control variables set in the camera 100 (step S202). Subsequently, the CPU 151 controls the focus control unit 133 and the like to move the photographing optical member such as the focus lens 131 to a predetermined initial position (step S203).

  Next, the CPU 151 detects whether or not a power off operation has been performed by the operator (step S204). When the power-off operation is detected (YES in step S204), the CPU 151 performs post-processing such as clearing various flags and control variables in order to turn off the power of the camera 100 (step S205). Then, the CPU 151 ends the shooting operation.

  On the other hand, when the power-off operation is not detected (NO in step S204), the CPU 151 performs a focus detection process described later (step S207). Then, under the control of the CPU 151, as will be described later, the focus control unit 133 illuminates the focus lens 131 according to the driving direction, the driving speed, and the driving position (that is, the defocus amount) obtained by the focus detection process. Driving along the axis moves the focus lens 131 to the in-focus position (step S208: focus control).

  Subsequently, the imaging control unit 143 controls the imaging element 141 under the control of the CPU 151 to photoelectrically convert the subject image (step S209). Then, the imaging signal processing unit 142 performs predetermined signal processing on the image signal that is the output of the imaging element 141 to obtain image data.

  Next, the CPU 151 detects whether the operator has pressed a recording button (not shown) in the operation unit 156 and confirms whether recording is in progress (step S210). If recording is not in progress (NO in step S210), CPU 151 returns to the process in step S204.

  On the other hand, when recording is in progress (YES in step S <b> 210), the CPU 151 causes the imaging control unit 143 to send image data (synthesized image data) output from the imaging signal processing unit 142 to the image compression / decompression unit 153. Then, the image compression / decompression unit 153 compresses the image data and records it on the image recording medium 157. Thereafter, the CPU 151 returns to the process of step S204.

  FIG. 3 is a diagram for explaining an example of the configuration of the image sensor 141 shown in FIG. 3A is a diagram showing a cross section of the pixels provided in the image sensor 141, and FIG. 3B is a plan view showing a part of the pixel array in the image sensor 141. FIG. FIG. 3C is a cross-sectional view along the line AA shown in FIG.

  In FIG. 3A, each pixel includes a photoelectric conversion unit 30 that photoelectrically converts an optical image to obtain a pixel signal. The photoelectric conversion unit 30 is divided into a first photoelectric conversion element 30-1 and a second photoelectric conversion element 30-2. The microlens (on-chip microlens) 31 is disposed so that the optical axis thereof is aligned with the boundary between the first and second photoelectric conversion elements 30-1 and 30-2, and condenses the light on the photoelectric conversion unit 30. . Further, a planarizing film 32, a color filter 33, a wiring 34, and an interlayer insulating film 35 are disposed in the pixel.

  As shown in FIG. 3B, in the image sensor 141, a plurality of pixels shown in FIG. 3A are arranged in a two-dimensional matrix. In these pixels, R (red), G (green), and B (blue) color filters 33 are alternately arranged, and a set of pixel blocks 40, 41, and 42 is constituted by four pixels, This is a so-called Bayer array.

  In FIG. 3B, subscripts “1” and “2” of R, G, and B are subscripts of the first and second photoelectric conversion elements 30-1 and 30-2, respectively. Show.

  In FIG. 3C, the image sensor 141 is disposed on an image formation plane on which light (light flux) incident through the photographing lens 101 forms an image. By the microlens 31, the first and second photoelectric conversion elements 30-1 and 30-2 respectively receive a pair of light beams that have passed through different positions (regions) of the pupil region (exit pupil) of the photographing lens 101.

  In the illustrated example, the first photoelectric conversion element 30-1 receives a light beam that passes through a region located on the right side of a pupil region (also simply referred to as a pupil) of the photographing lens 101. On the other hand, the second photoelectric conversion element 30-2 receives a light beam passing through a region located on the left side of the pupil of the photographing lens 101. Thereby, the pupil 50 is divided into pupils in the pixel (that is, the photoelectric conversion unit 30).

  FIG. 4 is a diagram illustrating the pupil 50 of the photographing lens 101 when the direction of the photographing lens 101 is viewed from the image sensor 141 illustrated in FIG. 3.

  In FIG. 4, the pupil 50 has sensitivity regions 51-1 and 51-2, and the sensitivity region 51-1 is a sensitivity region (hereinafter referred to as an A image pupil) of the first photoelectric conversion element 30-1. The sensitivity region 51-2 is a sensitivity region (hereinafter referred to as a B image pupil) of the second photoelectric conversion element 30-2. The gravity center positions 52-1 and 52-2 are the gravity center positions of the A image pupil and the B image pupil, respectively.

  In the imaging process, an image signal is generated by adding the outputs of two photoelectric conversion elements in which color filters of the same color are arranged in the same pixel.

  On the other hand, in the focus detection process, a focus detection signal (first focus detection signal) is obtained by integrating the outputs of the first photoelectric conversion elements 30-1 in one pixel block. An A image signal (first image signal) is generated by continuously acquiring the first focus detection signal for the pixel blocks 40, 41, and 42, that is, for the pixel blocks arranged in the horizontal direction. Is done.

  Similarly, a focus detection signal (second focus detection signal) is obtained by integrating the outputs of the second photoelectric conversion elements 30-2 in one pixel block. A B image signal (second image signal) is generated by continuously obtaining the second focus detection signals for the pixel blocks arranged in the horizontal direction. Then, the A image signal and the B image signal become phase difference detection signals.

  FIG. 5 is a diagram showing a focus detection area set in an image indicated by the first and second image data obtained by the imaging signal processing unit 142 shown in FIG.

  In FIG. 5, for example, a focus detection region (that is, focus detection pixel) 61 is set at a predetermined position according to the imaging angle of view 60. The phase difference AF processing unit 135 generates the above-described A image signal and B image signal in the focus detection area 61 set for the first and second image data, and converts these A image signal and B image signal. It is a phase difference detection signal. Then, the phase difference AF processing unit 135 performs focus detection on the subject according to the phase difference detection signal.

  Note that a plurality of focus detection areas may be set in the imaging angle of view 60. Here, two photoelectric conversion elements are provided for all the pixels of the image sensor 141 to generate the phase difference detection signal in the focus detection area. For example, the pixels corresponding to the focus detection area are shown in FIG. You may make it be the pixel shown to 3 (a).

  FIG. 6 is a diagram for explaining another example of generation of an image signal used for focus detection in the pixel array shown in FIG.

  In the illustrated example, pixels are line-added in the vertical direction within a predetermined range. That is, an image signal used for focus detection is generated by averaging the two pixel blocks in the Bayer array in the vertical direction. Note that the number of line additions can be arbitrarily set, and the focus detection area 61 increases in the vertical direction with respect to the angle of view as the number of line additions increases.

  FIG. 7 is a diagram illustrating an example of an A image signal and a B image signal generated by the phase difference AF processing unit 135 illustrated in FIG.

  In FIG. 7, the horizontal axis indicates the position of the pixel, and the vertical axis indicates the signal level of the image signal (A image signal and B image signal). The image shift amount X in the phase difference detection signal changes according to the imaging state of the taking lens 101 (for example, in-focus state, front pin state, or rear pin state).

  When the photographic lens 101 is in focus, the amount of image shift between the A image signal and the B image signal is eliminated. On the other hand, when the photographing lens 101 is in the front pin state or the rear pin state, the image shift amount X is generated in different directions. The image shift amount X has a certain relationship with the distance between the position where the subject image is formed by the photographing lens 101 and the top surface of the microlens, that is, the defocus amount.

  The phase difference AF processing unit 135 performs a correlation operation on the A image signal and the B image signal under the control of the CPU 151 to obtain the image shift amount X. In this correlation calculation, the phase difference AF processing unit 135 calculates a correlation value between the A image signal and the B image signal while shifting the pixel position, and the difference between the positions where the correlation value is maximized is determined as an image shift amount. To do. Then, the phase difference AF processing unit 135 obtains the defocus amount of the photographing lens 101 based on the image shift amount X, and calculates the lens driving amount of the focus lens 131 in which the photographing lens 101 is in focus.

  FIG. 8 is a diagram for explaining the conversion from the image shift amount to the defocus amount performed by the phase difference AF processing unit 135 shown in FIG.

  In FIG. 8, an optical system including the photographing lens 101 and the image sensor 141 is shown, and the position p1 of the focus detection surface exists on the optical axis related to the position p0 of the planned imaging surface with respect to the subject 70. The relationship between the image shift amount and the defocus amount is determined according to the optical system. The defocus amount is obtained 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 is moved to the position p2, the amount of image shift according to the similarity between the triangle defined by the positions p0, q2, and q3 and the triangle defined by the positions p0, q2 ′, and q3 ′ Changes. Therefore, the defocus amount at the position p2 on the focus detection surface can be calculated according to the shift amount.

  Under the control of the CPU 151, the phase difference AF processing unit 135 calculates the position of the focus lens 131 for bringing the subject into focus based on the defocus amount.

  By the way, before the above-described correlation calculation, the phase difference AF processing unit 135 performs a filtering process on the A image signal and the B image signal. This filtering process enhances the focus detection accuracy by emphasizing edges in the A image signal and the B image signal.

  In addition, when correction for matching the dynamic range levels of the A image signal and the B image signal is performed, the DC component, which is an error due to the correction, is cut, thereby improving detection accuracy and erroneous detection of an image shift amount. Can be suppressed.

  In the example shown in FIG. 3, when the focus lens 131 is positioned in the vicinity of the in-focus with respect to the subject, the A image signal and the B image signal are substantially the same. For this reason, if band-pass filter (hereinafter referred to as BPF) processing for enhancing edges is performed on the A image signal and the B image signal, focus detection accuracy is improved.

  On the other hand, in the state shown in FIG. 7, that is, when the focus lens 131 is in a defocused state with respect to the subject, the influence of vignetting by the photographing lens 101 and the division of light incident on the two photoelectric conversion elements are 100%. The image indicated by the A image signal and the B image signal is destroyed due to the influence of the partial mixing.

  FIG. 9 is a diagram illustrating a state after the BPF processing is performed on the A image signal and the B image signal when the focus lens 131 illustrated in FIG. 1 is in the defocused state.

  As shown in the figure, when the BPF processing is performed on the A image signal and the B image signal while the focus lens 131 is in the defocused state, the state in which the waveforms of both the A image signal and the B image signal are broken is emphasized. End up. If an attempt is made to detect an image shift amount using such A and B image signals, the position of the image shift will be detected and the defocus amount cannot be obtained with high accuracy.

  Here, the image shift amount obtained in accordance with the A image signal and the B image signal subjected to the first filter processing without the BPF processing is X1, and the A image signal subjected to the second filter processing with the BPF. The image shift amount obtained according to the B image signal is X2. Then, under the control of the CPU 151, the phase difference AF processing unit 135 controls the image shift amount X1 and the image shift amount X2 (second image shift amount) according to the image shift amount X1 (first image shift amount) and the F value of the photographing lens 101. One of the image shift amounts) is selected as the final image shift amount (also referred to as a selected image shift amount).

  Here, the first filter process is a process of reducing noise included in the A image signal and the B image signal by performing a low pass filter (LPF) process on the A image signal and the B image signal, for example. That is, in the first filter processing, filter processing is performed on the A image signal and the B image signal in a predetermined first frequency band.

  The second filter processing is, for example, BPF processing for edge enhancement as described above. That is, in the second filtering process, the filtering process is performed on the A image signal and the B image signal in the second frequency band higher than the first frequency band.

  FIG. 10 is a diagram for explaining selection of the first and second image shift amounts performed by the phase difference AF processing unit 135 shown in FIG.

  In FIG. 10, the horizontal axis indicates the F value of the photographing lens 101, and the vertical axis indicates the reference image shift amount (that is, the range of the image shift amount X1: reference value). If the image shift amount X1 obtained as a result of the first filter processing is smaller than the reference image shift amount corresponding to the F value that is the photographing condition for obtaining the image shift amount X1, the phase difference AF is obtained. The processing unit 135 selects the image shift amount X2 as the final image shift amount (selected image shift amount).

  On the other hand, if the image shift amount X1 obtained as a result of the first filter processing is equal to or larger than the reference image shift amount corresponding to the F value that is the photographing condition for obtaining the image shift amount X1, the phase difference AF. The processing unit 135 selects the image shift amount X1 as the final image shift amount (selected image shift amount).

  That is, the phase difference AF processing unit 135 determines whether the focus lens 131 is located near the in-focus position or in the defocused state with respect to the subject based on the image shift amount X1. Then, the phase difference AF processing unit 135 determines whether it is effective to perform the second filter processing on the A image signal and the B image signal according to the determination result.

  Note that the reference image shift amount is set to increase as the F value decreases, and is set to decrease as the F value increases. In the example shown in FIG. 10, the reference image shift amount (the range of the image shift amount X1) is set in inverse proportion to the F value. A predetermined coefficient K (conversion coefficient) for calculating the defocus amount from the image shift amount is expressed by a function of approximately square with respect to the F value.

  For this reason, if the reference image shift amount is set in inverse proportion to the F value, the range of the defocus amount obtained as a result of multiplying the image shift amount by the predetermined coefficient K is proportional to the F value. That is, the phase difference AF processing unit 135 selects the image shift amount X2 if the depth of focus is within a predetermined range at each F value, and selects the image shift amount X1 if the depth of focus is outside the predetermined range.

  FIG. 11 is a flowchart for explaining the focus detection process shown in FIG. Note that the processing according to the illustrated flowchart is performed by the imaging unit control unit 143 and the phase difference AF processing unit 135 under the control of the CPU 151.

  When focus detection is started, the imaging unit control unit 143 accumulates electric charges by the imaging element 141 (step S1102: sensor accumulation). Then, under the control of the CPU 151, the imaging unit control unit 143 determines whether or not charge accumulation by the imaging element 141 is completed (step S1103). That is, the imaging unit control unit 143 determines whether or not the charge accumulation end time has been reached.

  If the charge accumulation end time has not been reached (NO in step S1103), the imaging unit control unit 143 returns to the process in step S1102 and continues to accumulate charges in the imaging element 141. On the other hand, when the charge accumulation end time is reached (YES in step S1103), the imaging unit control unit 143 reads pixel values in a preset focus detection region (step S1104).

  Subsequently, under the control of the CPU 151, the imaging unit control unit 143 determines whether or not reading for a predetermined number of pixels existing in the focus detection area is completed (step S1105). If the reading for the predetermined number of pixels has not been completed (NO in step S1105), the imaging unit control unit 143 returns to the process of step S1104 and steps S1104 to S1105 until the reading for the predetermined number of pixels is completed. Repeat the process.

  When the reading for the predetermined number of pixels is completed (YES in step S1105), as described above, the phase difference AF processing unit 135 determines the A image signal and the A image signal according to the image data output from the imaging signal processing unit 142. A B image signal is generated. Then, the phase difference AF processing unit 135 performs the above-described first filter processing on the A image signal and the B image signal (step S1106). Note that the first filter processing includes correction processing for the A image signal and B image signal and averaging filter processing.

  Next, under the control of the CPU 151, the phase difference AF processing unit 135 performs the above-described correlation calculation on the A image signal and the B image signal after the first filter processing, and the image shift amount X1 (the first image shift amount). ) Is calculated (step S1107). In this correlation calculation, as described above, the correlation value is obtained while shifting the pixels of the A image signal and the B image signal in the focus detection region, and the difference between the positions where the correlation value is maximized is used as the image shift amount. The When obtaining the correlation value, the A image signal and the B image signal are overlapped and compared, and the smaller accumulated value is used as the correlation value.

  Note that the larger accumulated value may be used as the correlation value. Further, a difference between accumulated values may be used as a correlation value. The cumulative value is an index indicating the correlation value. When the smaller cumulative value is used as the correlation value, the cumulative value is the largest when the correlation is high. When the larger cumulative value is used as the correlation value or when the difference is used as the correlation value, the time when the cumulative value or the difference is the smallest is the time when the correlation is high.

  Subsequently, the phase difference AF processing unit 135 performs second filter processing on the A image signal and the B image signal (step S1108). The second filter processing includes correction processing and averaging filter processing similar to those of the first filter processing, and processing such as edge enhancement. Then, under the control of the CPU 151, the phase difference AF processing unit 135 performs the above-described correlation calculation on the A image signal and the B image signal after the second filter processing, and the image shift amount X2 (second image shift amount). Is obtained (step S1109).

  Next, the phase difference AF processing unit 135 determines whether or not the absolute value of the image shift amount X1 is greater than or equal to the reference image shift amount (predetermined reference value) described with reference to FIG. 10 (step S1110). If the determination result indicates that the absolute value of the image shift amount X1 is equal to or greater than a predetermined reference value (YES in step S1110), the phase difference AF processing unit 135 uses the image shift amount X1 as the final image shift amount (selection). (Image shift amount) is selected (step S1111). On the other hand, if the determination result indicates that the absolute value of the image shift amount X1 is less than the predetermined reference value (NO in step S1110), the phase difference AF processing unit 135 sets the image shift amount X2 as the selected image shift amount. Select (step S1112).

  Subsequent to step S1111 or S1112, the CPU 151 evaluates the reliability of the selected image shift amount (step S1113). When evaluating the reliability, the CPU 151 evaluates the reliability based on the contrast of the A image signal and the B image signal and the degree of coincidence of the A image signal and the B image signal.

  Subsequently, the CPU 151 determines whether or not the selected image shift amount is reliable according to the result of the reliability evaluation in step S1113 (step S1114). In the process of step S1114, the CPU 151 determines whether or not the reliability evaluation result is larger than a predetermined threshold value. When the reliability evaluation result is larger than a predetermined threshold, the CPU 151 determines that the selected image shift amount is reliable.

  On the other hand, if the result of the reliability evaluation is equal to or less than the predetermined threshold, the CPU 151 determines that the selected image shift amount is not reliable. In step S1114, the CPU 151 also determines whether or not the subject is a subject suitable for correlation calculation.

  FIG. 12 is a diagram for explaining an example of an A image signal and a B image signal when a subject that is not suitable for correlation calculation is photographed. FIG. 12A is a diagram illustrating an example of an A image signal and a B image signal having repeatability, and FIG. 12B is a diagram illustrating determination of whether or not the subject has repeatability. .

  In the correlation calculation, when obtaining the correlation value while shifting the A image signal and the B image signal, if the A image signal and the B image signal have repeatability as shown in FIG. It may be determined that the positions match.

  In order to prevent such a misjudgment, for example, as shown in FIG. 12B, a correlation value waveform in which the horizontal axis represents the shift amount obtained by shifting the A image signal and the B image signal and the vertical axis represents the correlation value. The CPU 151 determines whether or not the subject has repetition, that is, the subject not suitable for the correlation calculation, using the square sum of the adjacent difference of the correlation value as an index.

  If it is determined that the selected image shift amount is reliable (YES in step S1114), under the control of the CPU 151, the phase difference AF processing unit 135 multiplies the selected image shift amount by a predetermined coefficient K (that is, Def = K XX (X is the selected image deviation amount)) and defocus amount Def are calculated (step S1115). Then, as will be described later, the focus control unit 133 drives and controls the focus motor 132 based on the defocus amount Def to move the focus lens 131 along the optical axis. Thereafter, the CPU 151 ends the focus detection process.

  On the other hand, if it is determined that the selected image shift amount is not reliable (NO in step S1114), the CPU 151 ends focus detection processing without performing focus detection assuming that focus detection is NG (step S1116).

  FIG. 13 is a flowchart for explaining an example of the focus control process shown in FIG. FIG. 13 is a flowchart showing the focus control method in the present embodiment. Note that the processing according to the illustrated flowchart is performed by the focus control unit 133 under the control of the CPU 151.

  When the focus control process is started, the focus control unit 133 obtains the defocus amount Def from the phase difference AF processing unit 135 under the control of the CPU 151 (step S1302). Then, the focus control unit 133 calculates a drive amount (lens drive amount) of the focus lens 131 based on the defocus amount Def (step S1303). At this time, the focus control unit 133 calculates the lens driving direction and the driving speed according to the defocus amount Def.

  Subsequently, the focus control unit 133 determines whether or not the absolute value of the defocus amount is equal to or less than a predetermined defocus threshold (step S1304). When the absolute value of the defocus amount exceeds the defocus threshold (NO in step S1304), the focus control unit 133 assumes that the position of the focus lens 131 is not the in-focus position (in-focus), and the lens drive amount (and the drive direction). The focus lens motor 132 is driven and controlled according to the drive speed) to move the focus lens 131 along the optical axis (step S1305). Then, the focus control unit 133 ends the focus control process.

  On the other hand, if the absolute value of the defocus amount is equal to or smaller than the defocus threshold (YES in step S1304), the focus control unit 133 assumes that the focus lens position is in focus and controls the focus lens motor 132 to focus lens 131. Is stopped (step S1306). Then, the focus control unit 133 ends the focus control process.

  In the camera 100, as described with reference to FIG. 2, the focus detection is performed a plurality of times until the subject is focused until the power is turned off.

  As described above, in the first embodiment of the present invention, the first image shift amount is obtained according to the A image signal and the B image signal subjected to the first filter processing without BPF, and the first image with BPF is used. The second image shift amount is obtained in accordance with the A image signal and the B image signal subjected to the filtering process 2. Then, either the first image displacement amount or the second image displacement amount is determined depending on whether or not the first image displacement amount is within a predetermined range determined by the F value (that is, the photographing condition) of the photographing lens. Choose. That is, one of the first filter processing and the second filter processing is applied depending on whether or not the first image shift amount is within a predetermined range determined by the F value of the photographing lens.

  Thus, when the focus lens 131 is positioned in the vicinity of the focus with respect to the subject, the edge can be emphasized by the second filter processing. On the other hand, in the defocused state, image collapse can be suppressed by the first filter processing, and as a result, the accuracy of focus detection can be improved.

[Second Embodiment]
Next, an example of a camera provided with the focus detection apparatus according to the second embodiment of the present invention will be described. The configuration of the camera according to the second embodiment is the same as that of the camera shown in FIG.

  In the first embodiment described above, the first image shift amount and the second image shift amount are determined depending on whether or not the first image shift amount is within a predetermined range determined by the F value of the photographing lens. Either one was selected as the selected image shift amount, and the defocus amount was determined according to the selected image shift amount. That is, the first filter process or the second filter process is selected according to the first image shift amount.

  On the other hand, in the second embodiment, the first filter process or the second filter process is selected based on the contrast evaluation value of the subject.

  FIG. 14 is a diagram for explaining an A image signal and a B image signal related to a subject having only an edge photographed by a camera including a focus detection apparatus according to the second embodiment of the present invention. FIG. 14A is a diagram showing an example of a subject having only an edge, and FIG. 14B is a first filter process for the A image signal and the B image signal related to the subject shown in FIG. It is a figure which shows the example which performed. FIG. 14C is a diagram illustrating an example in which the second filter processing is performed on the A image signal and the B image signal related to the subject illustrated in FIG.

  In the second embodiment, in the subject 1401 having only the edge shown in FIG. 14A, the second filter processing with BPF is always performed on the A image signal and the B image signal. That is, regardless of whether or not the first image shift amount obtained by the first filter processing without BPF is within a predetermined range determined by the F value of the photographic lens, the phase difference AF processing unit 135 is the first one. The second image shift amount obtained by the filter process 2 is selected as the selected image shift amount.

  As shown in FIG. 14B, only the part where the image is broken is seen in the A image signal and the B image signal after the first filter processing, whereas FIG. As described above, when the centroids of the A image signal and the B image signal are emphasized by the second filter processing, the image shift from the A image signal and the B image signal becomes clear. Thereby, focus detection can be accurately performed according to the image shift amount.

  When the subject 1401 shown in FIG. 14A is detected, for example, the phase difference AF processing unit 135 calculates the sum of the absolute values of the adjacent differences between the A image signal and the B image signal as the A image signal and the B image signal. The subject 1401 is detected by dividing by the difference between the maximum value and the minimum value.

  15A and 15B are flowcharts for explaining focus detection performed by a camera including a focus detection apparatus according to the second embodiment of the present invention.

  Note that the processing according to the illustrated flowchart is performed by the imaging unit control unit 143 and the phase difference AF processing unit 135 under the control of the CPU 151. Also, in the flowcharts shown in FIGS. 15A and 15B, the same steps as those in the flowchart shown in FIG.

  In step S <b> 1105, when readout for a predetermined number of pixels is completed, the phase difference AF processing unit 135 generates an A image signal and a B image signal according to the image data that is the output of the imaging signal processing unit 142.

  Under the control of the CPU 151, the phase difference AF processing unit 135 obtains the absolute value of the adjacent difference between the A image signal and the B image signal, and obtains the sum α for the number of pixels for the absolute value (step S1506). Then, the phase difference AF processing unit 135 sets the total α as the contrast α.

  Note that the number of pixels to which the absolute value is added is not necessarily the number of read pixels, and the sum may be calculated in an arbitrarily set range.

  Subsequently, the phase difference AF processing unit 135 obtains the maximum value and the minimum value of the same A image signal and B image signal in the range used in the processing of step 1506, respectively. Then, the phase difference AF processing unit 135 calculates the difference between the maximum value and the minimum value, and sets the difference as the contrast β (step S1507).

  Subsequently, the phase difference AF processing unit 135 performs the processes of steps S1106 to S1109 described with reference to FIG. 11 to obtain the first image shift amount X1 and the second image shift amount X2. Then, the phase difference AF processing unit 135 divides the contrast α by the contrast β (α / β), and determines whether α / β, which is a contrast evaluation value, is smaller than a predetermined contrast threshold (step S1512). .

  Note that α / β, which is a contrast evaluation value, is the number of probable edges existing in the subject, and is about 1 in the example shown in FIG. 14, for example, so the contrast threshold is set between 1 and 2. The

  If the contrast evaluation value α / β is less than the contrast threshold (YES in step S1512), the phase difference AF processing unit 135 selects the second image shift amount X2 as the selected image shift amount X (step S1513). .

  On the other hand, if the contrast evaluation value α / β is equal to or greater than the contrast threshold value (NO in step S1512), the phase difference AF processing unit 135 determines that the absolute value of the first image shift amount X1 is the reference image shown in FIG. It is determined whether or not the deviation amount (that is, the reference value) is greater than or equal to (step S1514).

  If the absolute value of the first image shift amount X1 is equal to or larger than the reference image shift amount (YES in step S1514), the phase difference AF processing unit 135 selects the first image shift amount X1 as the selected image shift amount ( Step S1515).

  On the other hand, when the absolute value of the first image shift amount X1 is less than the reference image shift amount (that is, less than the reference threshold value) (NO in step S1514), the phase difference AF processing unit 135 causes the second image shift amount X2 to be smaller. Is selected as the selected image shift amount (step S1516).

  After the processing of step S1513, S1515, or S1516, the processing of steps S1113 to S1116 described in FIG. 11 is performed.

  As described above, in the second embodiment of the present invention, the second filter processing is selected based on the contrast evaluation value of the subject. If the second filter process is not selected based on the contrast evaluation value, the first filter process and the second filter process are performed according to whether the first image shift amount is within a predetermined range determined by the F value of the photographing lens. Select one of the filtering processes.

  As a result, either the second filter process for enhancing the edge according to the subject or the first filter process for suppressing the image collapse is selected, and the focus detection accuracy can always be improved.

  In the first and second embodiments described above, a predetermined range to be compared with the image shift amount (that is, the reference image shift amount) is obtained according to the F value of the photographing lens. Alternatively, the predetermined range may be changed according to the exit pupil distance.

  For example, with respect to the shape of the aperture blade, the closer the aperture aperture is to a perfect circle, the smaller the influence of image distortion. (Image shift amount) is increased. On the other hand, as for the exit pupil distance, when the distance is extremely short, the influence of image collapse becomes large. Therefore, as the exit pupil distance is shortened, the predetermined range shown in FIG. 10 is reduced.

  Furthermore, in the first and second embodiments described above, two types of filter processing are prepared, and the filter processing is selected according to the first image shift amount, but there are three or more types of filter processing. It may be. Further, the frequency band in the filter processing may be changed according to the setting information of the photographing lens.

  As described above, in the embodiment of the present invention, either the second filter process with BPF or the first filter process without BPF is selected according to the photographing condition or the subject. The focus detection accuracy can be improved by properly using the case where the edge enhancement is effective and the case where it is effective to suppress the image collapse.

  As is clear from the above description, in the example shown in FIG. 1, the imaging signal processing unit 142, the phase difference AF processing unit 135, and the CPU 151 include a first filter unit, a second filter unit, and an image shift amount calculation unit. , Function as selection means, defocus amount calculation means, and contrast determination means. Further, the CPU 151, the focus control unit 133, and the focus motor 132 function as control means.

  In the example illustrated in FIG. 1, at least the CPU 151, the imaging signal processing unit 142, and the phase difference AF processing unit 135 constitute a focus detection device.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the focus detection apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the focus detection apparatus. The control program is recorded on a computer-readable recording medium, for example.

  Each of the control method and the control program has at least a first filter processing step, a second filter processing step, an image shift amount calculation step, a selection step, and a defocus amount calculation step.

  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 recording media, and the computer (or CPU, MPU, etc.) of the system or apparatus reads the program. To be executed.

DESCRIPTION OF SYMBOLS 30 Photoelectric conversion part 31 Micro lens 101 Shooting lens 103 Aperture 131 Focus lens 133 Focus control part 135 Phase difference AF process part 141 Image pick-up element 143 Image pick-up part control part 151 CPU

Claims (12)

At least according to the phase difference between the first image signal and the second image signal obtained from an imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographing lens including a focus lens. A focus detection device that performs focus detection,
First filter means for performing a first filtering process on the first image signal and the second image signal in a predetermined first frequency band;
Second filter means for performing a second filter process on the first image signal and the second image signal in a second frequency band higher than the first frequency band;
A first image shift amount indicating an image shift amount in the first image signal and the second image signal on which the first filter processing has been performed is obtained, and the first image processing on which the second filter processing has been performed is obtained. An image shift amount calculating means for obtaining a second image shift amount indicating an image shift amount in the image signal and the second image signal;
It is determined whether or not the first image shift amount is greater than or equal to a reference image shift amount determined according to a shooting condition, and the first image shift amount and the second image are determined according to the determination result. Selecting means for selecting either one of the shift amounts as the selected image shift amount;
Defocus amount calculation means for calculating a defocus amount indicating a defocus of the focus lens according to the selected image shift amount;
A focus detection apparatus comprising:   The selection unit selects the first image shift amount as the selected image shift amount when the first image shift amount is equal to or greater than the reference image shift amount, and the first image shift amount is the reference image shift amount. The focus detection apparatus according to claim 1, wherein the second image shift amount is selected as the selected image shift amount when the image shift amount is less than the image shift amount.   The focus detection apparatus according to claim 1, wherein the photographing condition is an F value that is setting information of the photographing lens.   The focus detection apparatus according to claim 3, wherein the reference image shift amount increases as the F value decreases.   The focus detection apparatus according to claim 3, wherein the reference image shift amount is inversely proportional to the F value. The photographing lens is provided with a diaphragm mechanism having diaphragm blades,
6. The focus detection apparatus according to claim 3, wherein the reference image shift amount is changed in accordance with a diaphragm aperture or an exit pupil distance driven by the diaphragm blades. A contrast determination unit that obtains a contrast evaluation value indicating the contrast of a subject according to the first image signal and the second image signal and determines whether the contrast evaluation value is equal to or greater than a preset threshold value. Have
When the contrast determination unit determines that the contrast evaluation value is less than a preset threshold, the selection unit selects the second image shift amount as the selected image shift amount regardless of the determination result. The focus detection apparatus according to claim 1, wherein   When the contrast determination unit determines that the contrast evaluation value is greater than or equal to a preset threshold value, the selection unit determines the first image shift amount and the second image shift amount according to the determination result. The focus detection apparatus according to claim 7, wherein one of the two is selected as a selected image shift amount.   The contrast determination means obtains a sum of absolute values of adjacent differences between the first image signal and the second image signal, and sets the maximum value and the second value for the first image signal and the second image signal, respectively. The focus detection apparatus according to claim 7 or 8, wherein a difference between minimum values is obtained, and a ratio between the sum and the difference is used as the contrast evaluation value. An imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographing lens including at least a focus lens;
The focus detection device according to any one of claims 1 to 9,
Control means for driving the focus lens along the optical axis of the photographing lens in accordance with the defocus amount obtained by the focus detection device, and bringing the focus lens into a focused state;
An imaging device comprising: At least according to the phase difference between the first image signal and the second image signal obtained from an imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographing lens including a focus lens. A method for controlling a focus detection apparatus that performs focus detection,
A first filter processing step of performing a first filter process on the first image signal and the second image signal in a predetermined first frequency band;
A second filter processing step of performing a second filter processing on the first image signal and the second image signal in a second frequency band higher than the first frequency band;
A first image shift amount indicating an image shift amount in the first image signal and the second image signal on which the first filter processing has been performed is obtained, and the first image processing on which the second filter processing has been performed is obtained. An image shift amount calculating step for obtaining a second image shift amount indicating an image shift amount in the image signal and the second image signal;
It is determined whether or not the first image shift amount is greater than or equal to a reference image shift amount determined according to a shooting condition, and the first image shift amount and the second image are determined according to the determination result. A selection step of selecting either one of the shift amounts as the selected image shift amount;
A defocus amount calculating step of calculating a defocus amount indicating a defocus of the focus lens according to the selected image shift amount;
A control method characterized by comprising: At least according to the phase difference between the first image signal and the second image signal obtained from an imaging device including a plurality of focus detection pixels that receive a pair of light beams that have passed through different pupil regions in a photographing lens including a focus lens. A control program used in a focus detection device that performs focus detection,
A computer included in the focus detection device,
A first filter processing step of performing a first filter process on the first image signal and the second image signal in a predetermined first frequency band;
A second filter processing step of performing a second filter processing on the first image signal and the second image signal in a second frequency band higher than the first frequency band;
A first image shift amount indicating an image shift amount in the first image signal and the second image signal on which the first filter processing has been performed is obtained, and the first image processing on which the second filter processing has been performed is obtained. An image shift amount calculating step for obtaining a second image shift amount indicating an image shift amount in the image signal and the second image signal;
It is determined whether or not the first image shift amount is greater than or equal to a reference image shift amount determined according to a shooting condition, and the first image shift amount and the second image are determined according to the determination result. A selection step of selecting either one of the shift amounts as the selected image shift amount;
A defocus amount calculating step of calculating a defocus amount indicating a defocus of the focus lens according to the selected image shift amount;
A control program characterized by causing

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