JP2015022028A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate processing of amending a signal of a focus detection pixel serving as a defect pixel to a signal for generating an image, while giving a light-shield shape of a focus detection pixel a degree of freedom.SOLUTION: An imaging device comprises: an image pickup element that has an imaging pixel in which an aperture of a pixel is not shielded, and a focus detection pixel in which one part of the aperture of the pixel is shielded; a signal generation part that generates a first signal of a signal serving as the focus detection pixel, and a second signal serving as a signal subtracting the signal of the focus detection pixel from a signal of the imaging pixel; a selection part that selects any of the first signal and the second signal generated by the signal generation part for use in a focus detection; and a focus detection part that performs the focus detection in a phase difference detection method, using one signal of the first signal and the second signal selected by the selection part.

Description

  The present invention relates to an autofocus technique in an imaging apparatus.

  In recent years, when shooting a still image or a moving image, a so-called live view shooting mode in which shooting is performed while observing a subject image formed on an image sensor in real time is becoming common. 2. Description of the Related Art Conventionally, as a method for performing automatic focus detection during live view shooting, there is a contrast evaluation type focus detection method that detects a change in contrast of a subject image that has been subjected to photoelectric conversion by an imaging pixel and determines an in-focus state. .

  On the other hand, for example, Patent Document 1 proposes a method of quickly driving a focus lens by using a phase difference detection method on the image sensor surface. In Patent Document 2, there is a proposal to reduce the number of focus detection pixels that have been subjected to light shielding and become defective pixels and need correction processing. Specifically, a virtual focus detection pixel is obtained by using the difference obtained by subtracting the signal of one focus detection pixel from the signal of the imaging pixel for the other of the pair of focus detection pixels for performing phase difference detection. A method has been proposed.

JP 2004-191629 A Japanese Patent No. 4797606

  However, in Patent Document 2, a signal of a focus detection pixel having a light shielding member in only one of a pair of focus detection pixels for performing phase difference detection is used. Therefore, in order to make the pair of focus detection signals as symmetrical as possible in order to improve the focus detection accuracy, the light shielding member in the focus detection pixel substantially halves the light beam range incident on the photoelectric conversion unit. The light shielding shape is limited.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a signal for generating an image of a focus detection pixel signal serving as a defective pixel while giving a degree of freedom to a light shielding shape of the focus detection pixel. It is to facilitate the correction process.

  An image pickup apparatus according to the present invention includes an image pickup element having an image pickup pixel in which a pixel opening is not shielded, a focus detection pixel in which a part of the pixel opening is shielded, and a signal from the focus detection pixel. A signal generation unit that generates a first signal and a second signal that is a signal obtained by subtracting the signal of the focus detection pixel from the signal of the imaging pixel; and the first signal generated by the signal generation unit. A selection means for selecting which one of the first signal and the second signal is used for focus detection; and one of the first signal and the second signal selected by the selection means. And a focus detection unit that performs focus detection using a phase difference detection method.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to make easy the process which correct | amends the signal of the focus detection pixel used as a defect pixel to the signal for image generation, giving a freedom degree to the light shielding shape of the focus detection pixel. .

1 is a diagram illustrating a configuration of a camera that is an embodiment of an imaging apparatus of the present invention. FIG. 3 is a diagram illustrating an example of a pixel array of an image sensor. The figure which showed the opening shape of the pixel for an imaging in the image sensor of FIG. 2, a focus detection pixel, and a virtual focus detection pixel. The figure which each showed the light beam range guided to the photoelectric conversion part in the pixel corresponding to FIG. The graph which showed the pupil intensity distribution relationship in each pixel of FIG.3 and FIG.4. The figure which showed the opening shape of the pixel for an imaging in the image pick-up element of FIG. 2, the pixel for a focus detection paired with the pixel of FIG.3 (b), and the virtual focus detection pixel paired with FIG.3 (c). The figure which each showed the light beam range guided to the photoelectric conversion part in the pixel corresponding to FIG. The graph which showed the pupil intensity distribution relationship in each pixel of FIG.6 and FIG.7. The figure which showed the image signal relationship of a pair of focus detection pixel. The figure which showed the reference pixel for performing a defect pixel correction | amendment. The figure which shows the flow of the focus detection operation | movement in one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a camera which is an embodiment of an imaging apparatus of the present invention. FIG. 1 shows a compact digital camera in which a camera body having an image sensor and a photographing optical system are integrated, and can record moving images and still images.

  In FIG. 1, reference numeral 101 denotes a photographing optical system. Reference numeral 102 denotes a first lens group disposed at the tip of the photographing optical system (imaging optical system), which is held movably in the optical axis direction. Reference numeral 103 denotes an aperture, which adjusts the light amount at the time of shooting by adjusting the aperture diameter, and also functions as an exposure time adjustment shutter at the time of still image shooting. Reference numeral 104 denotes a second lens group. The diaphragm 103 and the second lens group 104 are integrally driven in the optical axis direction, and perform a zooming function (zoom function) in conjunction with the moving operation of the first lens group 102. Reference numeral 105 denotes a third lens group that performs focus adjustment by movement in the optical axis direction. Reference numeral 106 denotes an optical low-pass filter, which is an optical element for reducing false colors and moire in a captured image.

  Reference numeral 107 denotes an image sensor composed of a C-MOS sensor and its peripheral circuits. The image sensor 107 is a two-dimensional single-plate color sensor in which M pixels in the horizontal direction and N pixels in the vertical direction are squarely arranged, and a primary color mosaic filter in a Bayer array is formed on-chip.

  Reference numeral 111 denotes a zoom actuator, which rotates a cam cylinder (not shown) manually or by an actuator, thereby driving the first lens group 102 to the third lens group 105 in the optical axis direction to perform a zooming operation. Reference numeral 112 denotes a diaphragm actuator that controls the aperture diameter of the diaphragm 103 to adjust the amount of photographing light and controls the exposure time during still image photographing. A focus actuator 113 drives the third lens group 105 in the optical axis direction to adjust the focus.

  Reference numeral 121 denotes a CPU, which has a calculation unit, ROM, RAM, A / D converter, D / A converter, communication interface, and the like to control various controls of the camera body. Based on a predetermined program stored in the ROM, various means included in the camera are driven, and a series of operations such as AF, photographing, image processing, and recording are executed.

  Reference numeral 122 denotes an image sensor driving unit that controls the imaging operation of the image sensor 107 and A / D-converts the acquired image signal and transmits it to the CPU 121. An image processing unit 123 performs processes such as γ conversion, color interpolation, and image compression of the image acquired by the image sensor 107. When a defect occurs in the image due to the defective pixel, the defective pixel correction unit 124 performs image correction processing to correct the image.

  Reference numeral 125 denotes a focus detection pixel extraction unit that extracts a pixel signal used for focus detection in a method of detecting a phase difference (phase difference detection method) in an image pickup pixel signal extracted by the image pickup device driving unit 122. It is means to do. A virtual focus detection pixel generation unit 126 generates a virtual focus detection pixel signal from the pixel signal used for focus detection extracted by the focus detection pixel extraction unit 125 and other pixel signals (signals). Generation).

  Reference numeral 127 denotes a focus detection signal selection unit, which is a signal of either the focus detection pixel obtained by the focus detection pixel extraction unit 125 or the virtual focus detection pixel obtained by the virtual focus detection pixel generation unit 126. It is a means for selecting whether to use. A focus detection unit 128 performs phase difference type focus detection using the selected focus detection pixel signal and calculates defocus information from the focused state. Note that the portions related to the focus detection described above will be described in detail later.

  A focus driving unit 131 controls the focus actuator 113 based on the defocus information of the focus detection unit 128, and drives the third lens group 105 in the optical axis direction to perform focus adjustment. Reference numeral 132 denotes an aperture driving unit that controls the aperture of the aperture 103 by drivingly controlling the aperture actuator 112. Reference numeral 133 denotes a zoom drive unit that drives the zoom actuator 111 in accordance with the zoom operation of the photographer.

  Reference numeral 141 denotes a display device such as an LCD, which displays information related to the shooting mode of the camera, a preview image at the time of shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, camera posture information, and the like. A group of operation switches 142 includes a power switch, a shooting start switch, a zoom operation switch, a shooting mode selection switch, and the like. Reference numeral 143 denotes a detachable flash memory that records a photographed image.

  FIG. 2 is a diagram illustrating an example of a pixel array of the image sensor according to the present embodiment. FIG. 2 shows a state in which a range of 12 rows in the vertical direction (Y direction) and 14 columns in the horizontal direction (X direction) of the two-dimensional C-MOS area sensor is observed from the photographing optical system side. A Bayer arrangement is applied to the color filters, and green (Red) and red (Red) color filters are alternately provided in order from the left on pixels in odd rows. In addition, blue (Blue) and green (Green) color filters are alternately provided in order from the left in the pixels in even rows. In FIG. 2, the color filter arrangement of Green, Red, and Blue is abbreviated as G, R, and B.

  Circles such as 201-205 represent on-chip microlenses. Each of the plurality of rectangles arranged inside the on-chip microlens is a photoelectric conversion unit (light receiving unit). In addition, the black hatched portion in the figure is a portion that is shielded from light within the pixel. In the following description, a shape in which a plurality of divided photoelectric conversion units are connected is referred to as a connection shape, and the center of the connection shape is referred to as a connection center.

  Reference numeral 201 denotes a first pixel group, which is hereinafter referred to as a general pixel, and the output of the first pixel group is used to generate a recording image. Here, the image for recording corresponds to a moving image in addition to a still image defined in a format such as JPEG. Reference numerals 202 to 205 in the figure denote a second pixel group.

  Although the second pixel group will be described in detail later, a pixel signal photoelectrically converted by a pair of pixels of the pixels 202 and 203 or the pixels 204 and 205 which are pixels of the second pixel group is used to detect a focus using a phase difference method. To use. Alternatively, a difference signal obtained by subtracting the pixel signal of the pixel from the pixel signal of the pixel 201 is used for focus detection by the phase difference method. The pixel signal of the second pixel group can be used as a recording image signal by performing correction processing on the output signal.

  Here, the pixels 202 and 203 and the pixels 204 and 205 detect subject images (vertical stripes and horizontal stripe patterns) in orthogonal directions, respectively. In the pixel arrangement direction in the figure, the pair of pixels 202 and 203 detect a subject image signal in the horizontal direction (scanning in the X direction in the figure to detect a vertical stripe pattern). A pair of pixels 204 and 205 detects a subject image signal in the vertical direction (scanning in the Y direction in the figure to detect a horizontal stripe pattern). Then, a phase difference is obtained from these difference signals to perform focus detection. The pixel groups of the pixels 202 to 205 can perform focus detection using a difference signal of an output signal from the adjacent general pixel group 201.

  This will be described with reference to FIGS. FIG. 3 illustrates the first shape pixel (imaging pixel) 201 of the present embodiment, the second shape pixel (focus detection pixel) 202 in which a light shielding member is arranged in the image sensor, It is the figure which showed the pixel 211 for the virtual focus detection produced | generated from a pixel. FIG. 4 is a diagram simply showing a cross section of the pixel of this embodiment.

  FIG. 4A corresponds to a cross section of the pixel 201 having the first shape, and a light shielding member is not provided for the photoelectric conversion unit 221 as illustrated in FIG. FIG. 4B shows a cross section of the pixel 202 having the second shape in which the light shielding member 405 is arranged in a part of the light guide path to the photoelectric conversion unit and the range of the incident light from the exit pupil of the photographing optical system is regulated. It is equivalent. In this example, in the pixel in FIG. 4B, the opening shape of the photoelectric conversion unit is set to about 3/4 of the area of the photoelectric conversion unit 221 by the light shielding member 405.

  FIG. 4C shows a cross-sectional structure of a virtual focus detection pixel generated from the pixel having the configuration shown in FIGS. 4A and 4B. Here, as the difference obtained by simply subtracting the opening shape 222 of FIG. 3B from the opening shape 221 of FIG. 3A, an opening shape 223 having an area of approximately ¼ of the opening shape 221 is generated. Is done.

  Next, a change in the signal intensity that is input to the photoelectric conversion unit from the exit pupil of the photographing optical system and becomes an image signal due to the change in the aperture shape of the photoelectric conversion unit will be described with reference to FIGS.

  Here, the planes 401 to 403 shown in FIG. 4 are considered to be planes arranged at the exit pupil position of the photographing optical system. Then, the light beam emitted from the plane 401 in FIG. 4A enters the general pixel 201 shown in FIG. 2 and is applied to the photoelectric conversion unit 221. The photoelectric conversion unit 221 performs a photoelectric conversion action. Hereinafter, the relationship between the light incident angle and the photoelectric conversion intensity at that time is referred to as a pupil intensity distribution, and a plane range in which a light beam is irradiated as in the plane 401. Is called the pupil intensity distribution range.

  4B is a diagram illustrating a light shielding member provided in the pixel 202 having the second shape. The light shielding member 405 includes a photoelectric conversion unit 222 from a partial range of the pupil intensity distribution range 401. Is converted into a pupil intensity distribution range as indicated by 402.

  Reference numeral 406 denotes a virtual light shielding portion shape obtained from FIGS. 4A and 4B. A new pupil intensity distribution range 403 is generated as a difference obtained by subtracting 402 from the pupil intensity distribution range 401 by the action of the virtual light shielding unit 406.

  The graph of FIG. 5 shows the pupil intensity distribution characteristics. The planes 401 to 403 shown in FIG. 4 correspond to the entrance pupil position of the photographing optical system when a plane light source having uniform illuminance is used. Then, the horizontal axis represents the light incident angle to the imaging pixels 201 and 202 from the planes 401 to 403. FIG. 5 shows an electric intensity change characteristic in which the photoelectric conversion unit receives a light beam and outputs it as an electric signal with respect to each light beam incident angle, which is a pupil intensity distribution characteristic. Note that the vertical axis of the graph of FIG. 5 is normalized so that the maximum value of the photoelectric conversion intensity is 1.

  Here, the curve indicated by S0 in FIG. 5 indicates the pupil intensity distribution characteristic of the imaging pixel 201, and the curve indicated by S1a indicates the pupil intensity distribution characteristic of the pixel 202. A curve indicated by S2a indicates a difference obtained by subtracting the photoelectric conversion intensity of the curve indicated by S1a from the photoelectric conversion intensity of the curve indicated by S0. The curve indicated by the difference S2a represents the pupil intensity distribution characteristic in the virtual focus detection pixel 211 shown in FIG.

  FIG. 6 shows a pixel shape for performing phase difference type focus detection paired with the focus detection pixel 202 or the virtual focus detection pixel 211 of FIG. FIG. 6A shows a general pixel similar to that shown in FIG. Further, the pixel 203 in FIG. 6B has an opening shape 224 in which the opening shape 222 of the pixel 202 in FIG. 3B is targeted in the scanning direction (horizontal direction in the drawing). The pixel 212 in FIG. 6C is a virtual image generated by the difference obtained by subtracting the pixel 203 in FIG. 6B from the general pixel 201 in FIG. 6A similarly to the pixel 211 in FIG. This is a virtual focus detection pixel having a clear aperture shape 225.

  FIG. 7 shows a cross-sectional structure corresponding to each pixel in FIGS. 6A, 6B, and 6C as in FIG. Reference numerals 401 and 702 in the figure denote an entrance pupil range on the pupil plane that performs a photoelectric conversion action on the exit pupil of the imaging optical system. The entrance pupil range is shown.

  Then, a light beam is incident on the focus detection pixel from the entrance pupil range 402 in FIG. 4B and the entrance pupil range 702 in FIG. 7B, and a phase difference is obtained using a pair of electrical signals photoelectrically converted from the received light beam. The focus detection is performed. Alternatively, light is incident on the virtual focus detection pixel from the virtual entrance pupil range 403 in FIG. 4C and the virtual entrance pupil range 703 in FIG. 7C, and a pair of electricity photoelectrically converted from the received light. A phase difference type focus detection is performed using the signal.

  FIG. 8 shows S0 indicating the pupil intensity distribution characteristics of the general pixel 201 in FIG. 7 and S1b indicating the pupil intensity distribution characteristics of the focus detection pixel 203 in the same manner as described with reference to FIG. Further, a curve S2b that is a pupil intensity distribution characteristic of the virtual focus detection pixel expressed by a difference obtained by subtracting the photoelectric conversion intensity indicated by S1b from the photoelectric conversion intensity indicated by S0 is shown.

  With respect to these characteristics, when the incident angle in the scanning direction for performing focus detection is the horizontal axis of the graph, the pupil intensity distribution characteristics of the pair of focus detection pixels performing focus detection by the phase difference method in FIGS. The characteristic is symmetrical with respect to the vertical axis at 0 °. Therefore, the correlation calculation process at the time of phase difference detection is easy to perform, and accurate focus detection can be performed.

  Next, the phase difference type focus detection based on the pixel structure will be described with reference to FIG. In FIG. 9, AI0 and BI0 are a pair of waveform signals (referred to as an A image waveform and a B image waveform) obtained by interpolating and synthesizing the output signals of the focus detection pixel group in the scanning direction for performing focus detection. The difference in the signal intensity barycentric position is shown in place of the correlation amount.

  Here, AI0 and BI0 in FIG. 9 are the output waveforms of the pair of focus detection pixel groups shown in the combination of FIGS. 4B and 7B, or in FIGS. 4C and 7C. 2 shows a virtual output waveform generated from a pair of virtual focus detection pixel groups shown in combination.

  In the phase difference focus detection method, the relative positions of the A image waveform and the B image waveform are shifted to superimpose each other waveform, and the state where the area amount of the difference portion is the smallest is the most correlated state. Then, the relative shift amount (image shift amount) of the B image waveform with respect to the A image waveform is detected, and the defocus amount is calculated by dividing the base line length from the image shift amount.

  In the focus detection pixel group described above, the factors that determine the size of the aperture shape of the focus detection photoelectric conversion unit are as follows.

  Again, in the phase difference detection type focus detection method, the pupil of the focus detection beam is divided on the exit pupil of the photographing optical system. Then, for example, scanning is performed in one direction (X or Y direction in FIG. 2) of a pair of pupil-divided pixel groups as in 402 and 702 and 403 and 703 in FIGS. Perform phase difference detection.

  If the pupil size in the pupil division direction is large, the focus detection accuracy is improved. However, if the blur amount of the focus detection image becomes too large, the image signal for correlation is weakened. There is a problem that the defocus range that can be made becomes narrower. Therefore, in order to improve the focus detection accuracy in the vicinity of the in-focus position where the defocus amount is small and the blur amount is small, it is preferable to set the pupil size to be large so as to increase the blur amount. In addition, the amount of blur at the same defocus varies depending on the Fno value of the photographing optical system.

  As described above, the selection of the signal for the focus detection pixel is changed according to the specification of the photographing optical system and the change in the setting state at the time of focus detection. For example, in the vicinity of the in-focus position where the defocus amount is small and the blur amount is small, a combination of image signals obtained by the focus detection pixels 202 and 203, that is, a combination of image signals obtained from a pair of pupil ranges 402 and 702 having a large pupil size. Are used for focus detection. Further, for example, when the defocus amount is large and the blur amount is large, as shown by a pair of virtual focus detection pixels 211 and 212, it is obtained from a pair of virtual pupil ranges of 403 and 703 having small pupil dimensions. A combination of virtual image signals to be used is used for focus detection.

  As described above, the focus detection performance improvement in the present embodiment has been described. However, there is a problem that the intensity of the signal of the focus detection pixel provided with the above-described light shielding member is lower than the signal of the normal general pixel. .

  Therefore, when used as an image pickup signal for a recorded image, there is a problem that images such as black spots and spots are mixed and the quality as an appreciation image is deteriorated. Such a focus detection pixel can be considered to be similar to a defective pixel whose pixel output signal does not become a specified value due to a defective manufacturing process of the image sensor.

  FIG. 10 shows a correction method for improving the image output signal of the defective pixel. Here, the pixel 203 provided with the light shielding member in FIG. 2 will be described as an example.

  In FIG. 10, the normal pixel of the adjacent filter of the same color (here, Green) is set as a reference pixel of the pixel 203 as indicated by an arrow. For example, the output of the pixel 203 is corrected by using the average value of the output signals of the four reference pixels in FIG. 10 and using the average value as the output signal of the pixel 203.

  However, this method has a problem in that the handling of the image signal becomes complicated, and at the same time, the position is far away and the image signal at a different position of the subject (parallax is generated) is used. For this reason, for example, in a subject having a clear contrast outline such as an edge, a phenomenon that an image signal that should not be present occurs, and it becomes difficult to perform accurate image correction processing.

  As another method, there is a method of reducing the discontinuity of the output signal with an adjacent pixel having the same color filter by raising the gain of the output value of the pixel 203 itself. Since this method uses its own image signal, there is an advantage that the above-described disadvantage that the accuracy of image correction depends on the subject is alleviated.

  As a correction method for realizing this, in the pupil intensity distribution curve of FIG. 5 or FIG. 8, the integral value of S1a or S1b of the output characteristic curve of the normal pixel output characteristic S0 and the output characteristic curve of the pixel 203 to be corrected is obtained. A method for obtaining the gain value from the area ratio is conceivable. This method can be said to be a simple correction method if a gain value for the exit pupil diameter of the photographing optical system such as the Fno value at the time of photographing is set in advance.

  However, since the ray information from a certain incident angle range is missing, a part of the subject that should be captured is missing. Therefore, in order to obtain correction accuracy, it is desirable to set the light-shielding range of the defective pixel small and to reduce the light loss rate as much as possible. Therefore, in this embodiment, the focus detection pixels (for example, 211 and 212) having the light shielding portion larger than half of the light receiving area are changed from the focus detection pixels (for example, 202 and 203) having the light shielding portion smaller than the half of the light receiving area. Since the signal can be virtually generated, the actual focus detection pixel may be only a pixel having a small light shielding portion. Therefore, the defective pixel correction process can be accurately performed by a simple method as described above.

  Next, FIG. 11 is a flowchart showing a flow of focus detection processing of the present embodiment. Here, after selecting one of the real focus detection pixel signal and the virtual focus detection pixel signal generated therefrom, a method of performing focus detection by performing correlation calculation on the signal acquired from the selected pixel is described. Show.

  The photographing device catches the photographing subject, and first, in step S100, the photographing pixel signal is captured. When the focus detection operation is started, in step S101, a signal for focus detection pixel signal acquisition processing is performed, and in step S102, Fno value acquisition processing at the time of focus detection is performed.

  In step S103, in order to determine which of the actual focus detection pixel or the virtual focus detection pixel generated therefrom is to be used for the focus detection process, the set Fno value and threshold value at the time of focus detection are set. Compare.

  When it is determined in step S103 that the Fno value (aperture value) is brighter than the threshold value, the process proceeds to step S104, and the signal of the focus detection pixel acquired in S101 and the general pixel adjacent to it. A process of generating a virtual focus detection pixel from the signal is performed.

  In step S105, the correlation calculation process is performed using the focus detection signal selected in the conditional branching process in step S103 among the real focus detection pixel signal and the virtual focus detection pixel signal. In step S106, a defocus amount calculation process is performed from the image shift amount obtained by the correlation calculation in step S105.

  Next, in S107, it is determined from the defocus amount obtained in Step S106 whether or not it is within a specified focus determination range. If it is determined that the subject is in focus, a series of focus detection processes are finished and the process proceeds to a photographing operation or the like. On the other hand, when it is determined that the subject is not in focus, a focus drive amount calculation process necessary for focusing is performed from the defocus amount calculated in step S108. In step S109, after focus drive based on the focus drive amount obtained in step S108 is performed, the process returns to step S101, and the focus detection processing operation is repeated again.

  Note that the capturing process of the signal for the imaging pixel in step S100 is performed in accordance with the imaging frame rate of the imaging apparatus, and the process may be turned back at a timing different from the focus detection process.

  As described above, in the above-described embodiment, it is easy to perform correction processing for focus detection pixels (defect pixels), and it is possible to improve focus detection accuracy.

  The present invention relates to focus adjustment of an electronic camera provided with an image sensor, and is particularly useful for movie cameras and digital still cameras.

Claims (5)

An imaging device having an imaging pixel in which the aperture of the pixel is not shielded; and a focus detection pixel in which a part of the aperture of the pixel is shielded;
Signal generating means for generating a first signal that is a signal of the focus detection pixel and a second signal that is a signal obtained by subtracting the signal of the focus detection pixel from the signal of the imaging pixel;
Selecting means for selecting which of the first signal and the second signal generated by the signal generating means is used for focus detection;
Focus detection means for performing focus detection by a phase difference detection method using one of the first signal and the second signal selected by the selection means;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein the light shielding member that shields the aperture of the pixel shields an area smaller than a half of an area of the light receiving portion of the focus detection pixel.   3. The selection unit according to claim 1, wherein the selection unit selects which of the first signal and the second signal is used for focus detection based on an aperture value of a photographing optical system used for photographing. The imaging device described in 1.   The imaging apparatus according to claim 1, further comprising a correcting unit that corrects the signal of the focus detection pixel in order to use the signal of the focus detection pixel as an image signal. . A method for controlling an imaging apparatus including an imaging element having an imaging pixel in which a pixel aperture is not shielded and a focus detection pixel in which a part of the pixel aperture is shielded.
A signal generation step of generating a first signal that is a signal of the focus detection pixel and a second signal that is a signal obtained by subtracting the signal of the focus detection pixel from the signal of the imaging pixel;
A selection step of selecting which of the first signal and the second signal generated by the signal generation step is used for focus detection;
A focus detection step of performing focus detection by a phase difference detection method using one of the first signal and the second signal selected by the selection step;
A method for controlling an imaging apparatus, comprising:

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