JP2015225310A - Image capturing device, control method therefor, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-precision focus adjustment even when an in-focus position according to a contrast evaluation is outside a drivable range of a focusing lens.SOLUTION: An image capturing device includes; an image sensor in which a plurality of first focus detection pixels for receiving light rays passing through a first pupil area of an imaging optical system, a plurality of second focus detection pixels for receiving light rays passing through a second pupil region, and a plurality of imaging pixels are arrayed; a first focus adjustment unit which performs phase difference-based focus adjustment, based on a first signal and second signal acquired from the first focus detection pixels and second focus detection pixels, respectively; a second focus adjustment unit which performs contrast detection-based focus adjustment, based on a sum signal obtained by shifting and adding the first signal and second signal; and a control unit. When a difference between a defocus amount detected by the second focus adjustment unit and a maximum drivable amount of a focusing lens is within a range in which the second focus adjustment unit can perform focus adjustment by the summing process that shifts and adds the first signal and second signal, the control unit lets the second focus adjustment unit perform focus adjustment by the summing process.

Description

  The present invention relates to a technique for performing autofocus (AF) control based on a photoelectric conversion signal output from an image sensor.

  As one of focus detection methods in the imaging apparatus, there is an imaging plane phase difference method in which phase detection method focus detection is performed by focus detection pixels arranged in an image sensor. As another method of focus detection of the image pickup apparatus, there is a contrast method in which focus detection is performed based on contrast evaluation performed on a captured image output from the image sensor.

  In Patent Document 1, an imaging apparatus capable of an imaging surface phase difference method has a contrast evaluation unit and a correlation calculation unit, compares absolute values of two focus evaluation ranges obtained from them, and compares the focus of an object based on the comparison result. A method for determining an evaluation value is disclosed. In the contrast evaluation means of Patent Document 1, the focus lens is actually driven for AF in order to determine the contrast focus position based on the contrast evaluation value of the signal obtained by shifting and adding image signals from different pupil regions. The focus position can be specified without performing.

JP 2013-25246 A

  However, depending on the position of the subject, the contrast focus position acquired by the contrast evaluation unit may be outside the driving range of the focus lens. The prior art disclosed in Patent Document 1 does not show a specific countermeasure for such a case. Therefore, focus adjustment by contrast evaluation may be impossible.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to enable highly accurate focus adjustment even when the focus position by contrast evaluation is outside the driving range of the focus lens.

  An imaging apparatus according to the present invention includes a first focus detection pixel that receives a light beam passing through a first pupil partial region of the imaging optical system, and the imaging optical system different from the first pupil partial region. A second focus detection pixel that receives a light beam passing through the second pupil partial region, and a pupil region obtained by combining the first pupil partial region and the second pupil partial region of the imaging optical system. An imaging device in which a plurality of imaging pixels that receive a passing light beam are arranged, a first signal obtained from the first focus detection pixel, and a second signal obtained from the second focus detection pixel First focus adjusting means for performing phase difference based focus adjustment, a first signal obtained from the first focus detection pixel, and a second signal obtained from the second focus detection pixel. Control based on the sum signal generated by shifting and summing A second focus adjusting unit that performs a focus adjustment of a strike detection method, and a focus adjustment from a large defocus state to a small defocus state of the imaging optical system is performed using the first focus adjusting unit; Control means for controlling the focus adjustment from the defocused state to the vicinity of the best focus position using the second focus adjustment means, and the control means is controlled by the second focus adjustment means. The difference between the detected defocus amount and the maximum drive amount of the focus lens of the imaging optical system is added by shifting and adding the first signal and the second signal by the second focus adjusting means. When the focus adjustment is within a range where the process can be performed, the second focus adjustment unit is caused to perform the focus adjustment by the addition process.

  According to the present invention, it is possible to perform high-precision focus adjustment even when the focus position by contrast evaluation is outside the driving range of the focus lens.

The figure which shows the structure of 1st Embodiment of the imaging device of this invention. Schematic of a pixel arrangement. The schematic plan view and schematic sectional drawing of a pixel. Schematic explanatory drawing of pixel and pupil division. Schematic explanatory diagram of image sensor and pupil division FIG. 3 is a schematic relationship diagram between a defocus amount and an image shift amount of a first focus detection signal and a second focus detection signal. The flowchart which shows the flow of a 1st focus detection process. The schematic explanatory drawing of the shading by the pupil shift | offset | difference of a 1st focus detection signal and a 2nd focus detection signal. The figure which shows the example of a filter frequency band. The figure which shows the example of a 1st focus detection signal and a 2nd focus detection signal. The figure which shows the example of the 1st focus detection signal and 2nd focus detection signal after an optical correction process and a 1st filter process. The figure which shows the example of calculation of 1st defocus amount and 2nd defocus amount. Schematic explanatory drawing of a refocus process. 6 is a flowchart showing a flow of second focus detection processing in the first embodiment. The figure which shows the example of the 1st focus detection signal after a 2nd filter process, and a 2nd focus detection signal. The figure which shows the example which carried out the shift addition of the 1st focus detection signal and 2nd focus detection signal after a 2nd filter process. The figure which shows the example of the 2nd evaluation value in case a peak position can be specified. FIG. 3 is a schematic explanatory diagram of a refocusable range. The figure which shows the example of the 2nd evaluation value when a peak position cannot be specified. 5 is a flowchart showing a flow of focus detection processing in the first embodiment. 9 is a flowchart showing a flow of focus detection processing in the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
[overall structure]
FIG. 1 is a diagram showing a configuration of a digital camera which is a first embodiment of an imaging apparatus of the present invention. In FIG. 1, reference numeral 101 denotes a first lens group disposed at the tip of the imaging optical system, which is held so as to be able to advance and retract in the optical axis direction. Reference numeral 102 denotes an aperture / shutter, 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 103 denotes a second lens group. The diaphragm shutter 102 and the second lens group 103 integrally move forward and backward in the optical axis direction, and perform a zooming function (zoom function) in conjunction with the forward and backward movement of the first lens group 101.

  Reference numeral 105 denotes a third lens group that performs focus adjustment by advancing and retreating 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 pickup element including a two-dimensional CMOS photosensor and a peripheral circuit, which is disposed on the image forming plane of the image forming optical system.

  A zoom actuator 111 rotates a cam cylinder (not shown) to drive the first lens group 111 to the third lens group 105 forward and backward in the optical axis direction, thereby performing a zooming operation. Reference numeral 112 denotes an aperture shutter actuator that controls the aperture diameter of the aperture / shutter 102 to adjust the amount of photographing light, and controls the exposure time during still image photographing. Reference numeral 114 denotes a focus actuator, which performs focus adjustment by driving the third lens group 105 back and forth in the optical axis direction.

  Reference numeral 115 denotes an electronic flash for illuminating a subject at the time of photographing. A flash illumination device using a xenon tube is suitable, but an illumination device including LEDs that emit light continuously may be used. Reference numeral 116 denotes an AF auxiliary light device that projects an image of a mask having a predetermined aperture pattern onto a subject field via a light projection lens, thereby improving the focus detection capability for a dark subject or a low-contrast subject.

  Reference numeral 121 denotes a CPU in the camera that controls various controls of the camera body, and includes a calculation unit, a ROM, a RAM, an A / D converter, a D / A converter, a communication interface circuit, and the like. Then, based on a predetermined program stored in the ROM, various circuits included in the camera are driven, and a series of operations such as AF, photographing, image processing, and recording are executed. The CPU 121 is a focus detection signal generation unit, a first focus detection unit, and a second focus detection unit of the present embodiment.

  An electronic flash control circuit 122 controls lighting of the electronic flash 115 in synchronization with the photographing operation. Reference numeral 123 denotes an auxiliary light driving circuit that controls the lighting of the AF auxiliary light device 116 in synchronization with the focus detection operation. An image sensor driving circuit 124 controls the image capturing operation of the image sensor 107 and A / D converts the acquired image signal and transmits the image signal to the CPU 121. An image processing circuit 125 performs processing such as γ conversion, color interpolation, and JPEG compression of an image acquired by the image sensor 107.

  A focus drive circuit 126 controls the focus actuator 114 based on the focus detection result, and adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction. Reference numeral 128 denotes an aperture shutter drive circuit which controls the aperture shutter actuator 112 to control the aperture of the aperture / shutter 102. Reference numeral 129 denotes a zoom drive circuit that drives the zoom actuator 111 in accordance with the zoom operation of the photographer.

Reference numeral 131 denotes a display device such as an LCD, which displays information related to the shooting mode of the camera, a preview image before shooting, a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. An operation switch group 132 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. Reference numeral 133 denotes a detachable flash memory that records a photographed image.
[Image sensor]
FIG. 2 shows a schematic diagram of the arrangement of the imaging pixels and focus detection pixels of the imaging device in the present embodiment.

  FIG. 2 shows the pixel (imaging pixel) array of the two-dimensional CMOS sensor (imaging device) in this embodiment in a range of 4 columns × 4 rows, and the focus detection pixel array in a range of 8 columns × 4 rows. Is. In the pixel group 200 of 2 columns × 2 rows shown in FIG. 2, a pixel 200R having a spectral sensitivity of R (red) is on the upper left, a pixel 200G having a spectral sensitivity of G (green) is on the upper right and lower left, and B ( A pixel 200B having a spectral sensitivity of (blue) is arranged at the lower right. Further, each pixel includes a first focus detection pixel 201 and a second focus detection pixel 202 arranged in 2 columns × 1 row.

  A large number of 4 columns × 4 rows of pixels (8 columns × 4 rows of focus detection pixels) shown in FIG. 2 are arranged on the surface, and a captured image (focus detection signal) can be acquired. In the present embodiment, the pixel period P is 4 μm, the number of pixels N is 5575 columns × 3725 rows = about 20.75 million pixels, the column direction cycle PAF of focus detection pixels is 2 μm, and the focus detection pixel number NAF is 11150 horizontally. The description will be made assuming that the image sensor has columns × vertical rows 3725 = approximately 41.5 million pixels.

  FIG. 3A shows a plan view of one pixel 200G of the image pickup device shown in FIG. 2 as viewed from the light receiving surface side (+ z side) of the image pickup device, and a cross section taken along the line aa in FIG. A cross-sectional view seen from the y side is shown in FIG.

  As shown in FIG. 3, in the pixel 200G of the present embodiment, a microlens 305 for condensing incident light is formed on the light receiving side of each pixel, and is divided into NH (two divisions) in the x direction and NV in the y direction. A divided (one-divided) photoelectric conversion unit 301 and a photoelectric conversion unit 302 are formed. The photoelectric conversion unit 301 and the photoelectric conversion unit 302 correspond to the first focus detection pixel 201 and the second focus detection pixel 202, respectively.

  The photoelectric conversion unit 301 and the photoelectric conversion unit 302 may be a pin structure photodiode in which an intrinsic layer is sandwiched between a p-type layer and an n-type layer, or an intrinsic layer may be omitted and a pn junction if necessary. A photodiode may be used.

  In each pixel, a color filter 306 is formed between the microlens 305 and the photoelectric conversion unit 301 and the photoelectric conversion unit 302. Further, as necessary, the spectral transmittance of the color filter may be changed for each pixel, or the color filter may be omitted.

  The light incident on the pixel 200 </ b> G illustrated in FIG. 3 is collected by the microlens 305, dispersed by the color filter 306, and then received by the photoelectric conversion unit 301 and the photoelectric conversion unit 302.

  In the photoelectric conversion unit 301 and the photoelectric conversion unit 302, a pair of electrons and holes are generated according to the amount of received light and separated by a depletion layer, and then negatively charged electrons are accumulated in an n-type layer (not shown), The holes are discharged to the outside of the image sensor through a p-type layer connected to a constant voltage source (not shown). Electrons accumulated in the n-type layer (not shown) of the photoelectric conversion unit 301 and the photoelectric conversion unit 302 are transferred to the capacitance unit (FD) through the transfer gate and converted into a voltage signal.

  FIG. 4 is a schematic explanatory diagram showing the correspondence between the pixel structure of this embodiment shown in FIG. 3 and pupil division. FIG. 4 shows a sectional view of the pixel structure of the present embodiment shown in FIG. 3A as viewed from the + y side and an exit pupil plane of the imaging optical system. In FIG. 4, in order to correspond to the coordinate axis of the exit pupil plane, the x-axis and y-axis of the cross-sectional view are inverted with respect to FIG.

  In FIG. 4, the first pupil partial region 501 of the first focus detection pixel 201 is substantially conjugated with the light receiving surface of the photoelectric conversion unit 301 whose center of gravity is decentered in the −x direction and the microlens. A pupil region that can be received by the first focus detection pixel 201 is shown. The first pupil partial region 501 of the first focus detection pixel 201 has an eccentric center of gravity on the + X side on the pupil plane.

  In FIG. 4, the second pupil partial region 502 of the second focus detection pixel 202 is substantially conjugated with the light receiving surface of the photoelectric conversion unit 302 whose center of gravity is decentered in the + x direction and the microlens. A pupil region that can be received by the bifocal detection pixel 202 is shown. The center of gravity of the second pupil partial region 502 of the second focus detection pixel 202 is eccentric to the −X side on the pupil plane.

  In FIG. 4, the pupil region 500 can receive light in the entire pixel 200 </ b> G when the photoelectric conversion unit 301 and the photoelectric conversion unit 302 (first focus detection pixel 201 and second focus detection pixel 202) are all combined. This is the pupil area.

  FIG. 5 is a schematic diagram showing the correspondence between the image sensor of this embodiment and pupil division. Light beams that have passed through different pupil partial areas of the first pupil partial area 501 and the second pupil partial area 502 are incident on each pixel of the image sensor at different angles, and are used for first focus detection divided into 2 × 1. Light is received by the pixel 201 and the second focus detection pixel 202. In the present embodiment, the pupil region is divided into two pupils in the horizontal direction. If necessary, pupil division may be performed in the vertical direction.

  The imaging device of the present embodiment includes a first focus detection pixel that receives a light beam passing through the first pupil partial region of the imaging optical system, and a second pupil partial region of the imaging optical system different from the first pupil partial region. A plurality of second focus detection pixels for receiving a light beam passing through the first imaging element and a plurality of imaging pixels for receiving a light beam passing through a pupil region including the first pupil partial region and the second pupil partial region of the imaging optical system. ing.

  In the imaging device of the present embodiment, each imaging pixel is composed of a first focus detection pixel and a second focus detection pixel. If necessary, the imaging pixel, the first focus detection pixel, and the second focus detection pixel are configured as separate pixels, and the first focus detection pixel and the second focus detection are included in a part of the imaging pixel array. A configuration may be adopted in which the pixels for use are partially arranged.

In the present embodiment, a first focus signal is generated by collecting the light reception signals of the first focus detection pixels 201 of each pixel of the image sensor, and the second light reception signals of the second focus detection pixels 202 of each pixel are collected. A focus signal is generated to perform focus detection. Further, by adding the signals of the first focus detection pixel 201 and the second focus detection pixel 202 for each pixel of the imaging element, an imaging signal (captured image) having a resolution of N effective pixels is generated.
[Relationship between defocus amount and image shift amount]
Hereinafter, the relationship between the defocus amount and the image shift amount of the first focus detection signal and the second focus detection signal acquired by the image sensor of the present embodiment will be described. FIG. 6 shows a schematic relationship diagram of the defocus amounts of the first focus detection signal and the second focus detection signal and the image shift amount between the first focus detection signal and the second focus detection signal. The imaging device of the present embodiment is arranged on the imaging surface 800, and the exit pupil of the imaging optical system is divided into a first pupil partial region 501 and a second pupil partial region 502, as in FIGS. .

  The defocus amount d is a distance | d | from the imaging position of the subject to the imaging surface, and a negative sign (d <0) indicates a front pin state where the imaging position of the subject is on the subject side from the imaging surface. A rear pin state in which the imaging position of the subject is on the opposite side of the subject from the imaging surface is defined as a positive sign (d> 0). An in-focus state where the imaging position of the subject is on the imaging surface (in-focus position) is d = 0. In FIG. 6, the subject 801 shows an example in a focused state (d = 0), and the subject 802 shows an example in a front pin state (d <0). The front pin state (d <0) and the rear pin state (d> 0) are combined to form a defocus state (| d |> 0).

  In the front pin state (d <0), the luminous flux that has passed through the first pupil partial area 501 (second pupil partial area 502) out of the luminous flux from the subject 802 is once condensed and then the gravity center position G1 of the luminous flux. The image spreads in the width Γ 1 (Γ 2) with (G 2) as the center, resulting in a blurred image on the imaging surface 800. The blurred image is received by the first focus detection pixel 201 (second focus detection pixel 202) constituting each pixel arranged in the image sensor, and a first focus detection signal (second focus detection signal) is generated. Is done. Therefore, the first focus detection signal (second focus detection signal) is formed as a subject image in which the subject 802 is blurred by the width Γ1 (Γ2) at the gravity center position G1 (G2) on the imaging surface 800. The blur width Γ1 (Γ2) of the subject image generally increases in proportion to the amount of defocus amount d | d |. Similarly, the magnitude | p | of the object image displacement amount p (= difference G1-G2 in the center of gravity of the light beam) between the first focus detection signal and the second focus detection signal is also the size of the defocus amount d. As | d | increases, it generally increases in proportion. Even in the rear pin state (d> 0), the image shift direction of the subject image between the first focus detection signal and the second focus detection signal is opposite to that in the front pin state, but the same.

Therefore, in this embodiment, as the magnitude of the defocus amount of the first focus detection signal and the second focus detection signal or the imaging signal obtained by adding the first focus detection signal and the second focus detection signal increases. The amount of image shift between the first focus detection signal and the second focus detection signal increases.
[Focus detection]
In the present embodiment, using the relationship between the defocus amount and the image shift amount of the first focus detection signal and the second focus detection signal, a method based on the first focus detection of the phase difference method and the refocus principle (hereinafter referred to as “refocus”). Second focus detection). First focus detection is performed to adjust the focus from the large defocus state to the small defocus state, and second focus detection is performed to adjust the focus from the small defocus state to the vicinity of the best focus position.
[First focus detection of phase difference method]
The phase difference type first focus detection in the present embodiment will be described below. In the first focus detection based on the phase difference method, the first focus detection signal and the second focus detection signal are relatively shifted to calculate a correlation amount (first evaluation value) representing the degree of coincidence of the signals. The image shift amount is detected from the shift amount that improves the degree of coincidence. As the magnitude of the defocus amount of the imaging signal increases, the image defocus amount is set to the first defocus because of the relationship that the image defocus amount between the first focus detection signal and the second focus detection signal increases. The focus is detected by converting it into a quantity.

  FIG. 7 shows a schematic diagram of the flow of the first focus detection process of the present embodiment. Note that the operation of FIG. 7 is executed by the focus detection signal generation unit, the image sensor 107 serving as the first focus detection unit, the image processing circuit 125, and the CPU 121 of the present embodiment.

  In step S110, a focus detection area for performing focus adjustment is set from the effective pixel area of the image sensor. The focus detection signal generating means generates a first focus detection signal (A image) from the light reception signal of the first focus detection pixel in the focus detection area, and generates a second from the light reception signal of the second focus detection pixel in the focus detection area. A focus detection signal (B image) is generated.

  In step S120, the first focus detection signal and the second focus detection signal are each subjected to 3-pixel addition processing in the column direction in order to suppress the signal data amount, and further, Bayer is used to convert the RGB signal into the luminance Y signal. (RGB) addition processing is performed. These two addition processes are combined into a first pixel addition process.

  In step S130, shading correction processing (optical correction processing) is performed on the first focus detection signal and the second focus detection signal, respectively.

  Hereinafter, shading due to pupil shift between the first focus detection signal and the second focus detection signal will be described. FIG. 8 shows the first pupil partial region 501 of the first focus detection pixel 201, the second pupil partial region 502 of the second focus detection pixel 202, and the exit pupil 400 of the imaging optical system at the peripheral image height of the image sensor. The relationship is shown.

  FIG. 8A shows a case where the exit pupil distance Dl of the imaging optical system and the set pupil distance Ds of the image sensor are the same. In this case, the exit pupil 400 of the imaging optical system is substantially equally divided by the first pupil partial region 501 and the second pupil partial region 502.

  On the other hand, when the exit pupil distance D1 of the imaging optical system shown in FIG. 8B is shorter than the set pupil distance Ds of the image sensor, the peripheral pupil height of the image sensor is equal to the exit pupil of the imaging optical system. A pupil shift of the entrance pupil of the image sensor occurs, and the exit pupil 400 of the imaging optical system is non-uniformly divided into pupils. Similarly, when the exit pupil distance Dl of the imaging optical system shown in FIG. 8C is longer than the set pupil distance Ds of the image sensor, the exit pupil and the image sensor of the imaging optical system are used at the peripheral image height of the image sensor. This causes a pupil shift of the entrance pupil, and the exit pupil 400 of the imaging optical system is non-uniformly divided into pupils. As pupil division becomes nonuniform at the peripheral image height, the intensity of the first focus detection signal and the second focus detection signal also becomes nonuniform, and one of the first focus detection signal and the second focus detection signal Shading occurs with increasing strength and decreasing the other strength.

  In step S130 of FIG. 7, the first shading correction coefficient of the first focus detection signal and the second focus are determined according to the image height of the focus detection area, the F value of the imaging lens (imaging optical system), and the exit pupil distance. A second shading correction coefficient of the detection signal is generated respectively. The first focus detection signal is multiplied by the first focus detection signal, the second shading correction coefficient is multiplied by the second focus detection signal, and shading correction processing (optical correction processing) of the first focus detection signal and the second focus detection signal is performed. )I do.

  In the first focus detection of the phase difference method, the first detection defocus amount is detected based on the correlation (signal coincidence) between the first focus detection signal and the second focus detection signal. When shading due to pupil shift occurs, the correlation (signal coincidence) between the first focus detection signal and the second focus detection signal may be reduced. Therefore, in the first focus detection of the phase difference method, the shading correction processing (optical) is performed in order to improve the correlation (signal matching degree) between the first focus detection signal and the second focus detection signal and to improve the focus detection performance. It is desirable to perform correction processing.

  In step S140 of FIG. 7, the first filter processing is performed on the first focus detection signal and the second focus detection signal. An example of the pass band of the first filter processing of the present embodiment is shown by a solid line in FIG. In the present embodiment, since the focus detection in the large defocus state is performed by the first focus detection of the phase difference method, the pass band of the first filter processing is configured to include the low frequency band. When the focus adjustment is performed from the large defocus state to the small defocus state as necessary, the pass band of the first filter processing at the time of the first focus detection according to the defocus state is indicated by a one-dot chain line in FIG. As described above, it may be adjusted to a higher frequency band.

  Next, in step S150 of FIG. 7, a first shift process for relatively shifting the first focus detection signal and the second focus detection signal after the first filter process in the pupil division direction is performed, and the degree of coincidence of the signals is expressed. A correlation amount (first evaluation value) is calculated.

  The k-th first focus detection signal after the first filter processing is A (k), the second focus detection signal is B (k), and the range of the number k corresponding to the focus detection area is W. The correlation amount (first evaluation value) COR is calculated by Equation (1), where s1 is the shift amount by the first shift process and Γ1 is the shift range of the shift amount s1.

  By the first shift process of the shift amount s1, the k-th first focus detection signal A (k) and the k-s1th second focus detection signal B (k-s1) are subtracted in correspondence to generate a shift subtraction signal. To do. The absolute value of the generated shift subtraction signal is calculated, the number k is summed within the range W corresponding to the focus detection area, and the correlation amount (first evaluation value) COR (s1) is calculated. If necessary, the correlation amount (first evaluation value) calculated for each row may be added over a plurality of rows for each shift amount.

  In step S160, a real-valued shift amount at which the correlation amount is the minimum value is calculated from the correlation amount (first evaluation value) by subpixel calculation, and is set as the image shift amount p1. The first defocus amount (Def1) is obtained by multiplying the image shift amount p1 by the image height of the focus detection area, the F value of the imaging lens (imaging optical system), and the first conversion coefficient K1 corresponding to the exit pupil distance. To detect.

  In the present embodiment, the first filter processing and the first shift processing are performed on the first focus detection signal and the second focus detection signal by the first focus detection means of the phase difference method, the correlation amount is calculated, and the correlation amount is calculated. A first defocus amount is detected.

  In the imaging device of the present embodiment, the light beam received by the focus detection pixels (first focus detection pixel and second focus detection pixel) is different from the light beam received by the imaging pixel. Therefore, the influence of each aberration (spherical aberration, astigmatism, coma aberration, etc.) of the imaging optical system on the focus detection pixel is different from the influence on the imaging signal. When the aperture value (F value) of the imaging optical system is small (bright), the difference becomes larger. Therefore, when the aperture value of the imaging optical system is small (bright), the best focus between the detection focus position (position where the first defocus amount is 0) calculated by the first focus detection of the phase difference method and the imaging signal. There may be a difference between the focal position (the MTF peak position of the imaging signal). Therefore, particularly when the aperture value (F value) of the imaging optical system is equal to or smaller than the predetermined aperture value, the focus detection accuracy of the first focus detection of the phase difference method may be lowered.

  FIG. 10 shows an example of the first focus detection signal (broken line) and the second focus detection signal (solid line) at the best focus position of the image pickup signal at the peripheral image height of the image sensor of the present embodiment. Although it is the best focus position of the imaging signal, the signal shapes of the first focus detection signal and the second focus detection signal are different due to the influence of each aberration of the imaging optical system. FIG. 11 shows the first focus detection signal (broken line) and the second focus detection signal (solid line) after the shading correction process and the first filter process. Although it is the best focus position of the imaging signal, the image shift amount p1 between the first focus detection signal and the second focus detection signal is not zero. Therefore, a difference is generated between the detection focus position calculated by the first focus detection of the phase difference method and the best focus position of the imaging signal.

  FIG. 12 shows an example of the first defocus amount (broken line) by the first focus detection of the phase difference method in the present embodiment. The horizontal axis is the set defocus amount, and the vertical axis is the detected defocus amount. The first focus detection signal and the second focus detection signal shown in FIG. 10 are the first focus detection signal and the second focus detection signal when the set defocus amount is 0 [mm] in FIG. Referring to FIG. 12, at the best focus position with the set defocus amount of 0, the first defocus amount by the first focus detection indicated by the broken line is offset by about 50 μm to the rear pin side. It can be seen that there is a difference of about 50 μm from the detected in-focus position calculated by the single focus detection.

In the present embodiment, the difference between the detected in-focus position calculated from the focus detection signal and the best in-focus position of the imaging signal is suppressed, thereby enabling highly accurate focus detection. Therefore, in addition to the first focus detection based on the phase difference method, the second focus detection based on the refocus method that enables highly accurate focus detection near the best focus position of the imaging optical system is performed.
[Refocus second focus detection]
Hereinafter, the second focus detection of the refocus method (contrast detection method) in the present embodiment will be described. In the second focus detection of the refocus method of the present embodiment, the first focus detection signal and the second focus detection signal are relatively shifted and added to generate a shift addition signal (refocus signal). A contrast evaluation value of the generated shift addition signal (refocus signal) is calculated, an MTF peak position of the imaging signal is estimated from the contrast evaluation value, and a second defocus amount is detected.

  FIG. 13 shows a schematic explanatory diagram of the refocus processing in the one-dimensional direction (column direction, horizontal direction) by the first focus detection signal and the second focus detection signal acquired by the image sensor of the present embodiment. An imaging surface 800 in FIG. 13 corresponds to the imaging surface 800 illustrated in FIGS. 5 and 6. In FIG. 13, i is an integer, and the first focus detection signal of the i-th pixel in the column direction of the image sensor arranged on the imaging surface 800 is schematically represented by Ai, and the second focus detection signal is schematically represented by Bi. The first focus detection signal Ai is a light reception signal of a light beam incident on the i-th pixel at the principal ray angle θa (corresponding to the pupil partial region 501 in FIG. 5). The second focus detection signal Bi is a light reception signal of a light beam incident on the i-th pixel at the principal ray angle θb (corresponding to the pupil partial region 502 in FIG. 5).

  The first focus detection signal Ai and the second focus detection signal Bi have not only light intensity distribution information but also incident angle information. Therefore, the first focus detection signal Ai is translated along the angle θa to the virtual imaging plane 810, and the second focus detection signal Bi is translated along the angle θb to the virtual imaging position 810 and added. A refocus signal at the virtual imaging plane 810 can be generated. Translating the first focus detection signal Ai along the angle θa to the virtual imaging plane 810 corresponds to a +0.5 pixel shift in the column direction, and the second focus detection signal Bi is virtually linked along the angle θb. Translating to the image plane 810 corresponds to a -0.5 pixel shift in the column direction. Therefore, the first focus detection signal Ai and the second focus detection signal Bi are relatively shifted by +1 pixel, and Ai and Bi + 1 are added in correspondence with each other, whereby a refocus signal on the virtual imaging plane 810 can be generated. Similarly, the first focus detection signal Ai and the second focus detection signal Bi are shifted by an integer and added to generate a shift addition signal (refocus signal) on each virtual imaging plane corresponding to the integer shift amount. . The contrast evaluation value of the generated shift addition signal (refocus signal) is calculated, and the MTF peak position of the imaging signal is estimated from the calculated contrast evaluation value, thereby performing the second focus detection of the refocus method.

  FIG. 14 shows a schematic diagram of the flow of the second focus detection process of the present embodiment. The operation of FIG. 14 is executed by the focus detection signal generation unit, the image sensor 107 as the second focus detection unit, the image processing circuit 125, and the CPU 121 of the present embodiment.

  In step S210, a focus detection area for performing focus adjustment is set from the effective pixel area of the image sensor. The focus detection signal generating means generates a first focus detection signal (A image) from the light reception signal of the first focus detection pixel in the focus detection area, and generates a second from the light reception signal of the second focus detection pixel in the focus detection area. A focus detection signal (B image) is generated.

  In step S220, the first focus detection signal and the second focus detection signal are each subjected to a three-pixel addition process in the column direction in order to suppress the amount of signal data, and further, Bayer is used to convert the RGB signal into a luminance Y signal. (RGB) addition processing is performed. These two addition processes are combined into a second pixel addition process. If necessary, one or both of the three-pixel addition process and the Bayer (RGB) addition process may be omitted.

  In step S230, the second filter processing is performed on the first focus detection signal and the second focus detection signal. An example of a pass band of the second filter processing of the present embodiment is indicated by a broken line and a dotted line in FIG. In the present embodiment, focus detection is performed from the small defocus state to the vicinity of the best in-focus position by the refocus second focus detection. Therefore, the pass band of the second filter process is set to include a higher frequency band than the pass band of the first filter process.

  If necessary, second filter processing is performed using a Laplacian (second-order differential) [1, -2,1] filter that performs edge extraction of the subject signal in the second filter processing, as indicated by the dotted line in FIG. The pass band may be set to a higher frequency band. By extracting the high frequency component of the subject and performing the second focus detection, the focus detection accuracy can be further improved.

  In step S240, a second shift process for relatively shifting the first focus detection signal and the second focus detection signal after the second filter process in the pupil division direction is performed and added to generate a shift addition signal (refocus signal). Generate. Further, a contrast evaluation value (second evaluation value) is calculated from the generated shift addition signal.

  The k-th first focus detection signal after the first filter processing is A (k), the second focus detection signal is B (k), and the range of the number k corresponding to the focus detection area is W. The contrast evaluation value (second evaluation value) RFCON is calculated by Expression (2), where s2 is the shift amount by the second shift process and Γ2 is the shift range of the shift amount s2.

  By the second shift processing of the shift amount s2, the kth first focus detection signal A (k) and the ks2th second focus detection signal B (ks2) are added in correspondence with each other, and the shift addition signal is obtained. Generate. The absolute value of the shift addition signal is calculated, the maximum value in the range of the focus detection area W is taken, and the contrast evaluation value (second evaluation value) RFCON (s2) is calculated. If necessary, the contrast evaluation value (second evaluation value) calculated for each row may be added over a plurality of rows for each shift amount.

  In step S250, a real-value shift amount at which the contrast evaluation value is the maximum value is calculated from the contrast evaluation value (second evaluation value) by subpixel calculation, and is set as the peak shift amount p2. The second detection defocus amount (Def2) is obtained by multiplying the peak shift amount p2 by the image height of the focus detection area, the F value of the imaging lens (imaging optical system), and the second conversion coefficient K2 corresponding to the exit pupil distance. Is detected. If necessary, the first conversion coefficient K1 and the second conversion coefficient K2 may be the same value.

  In the present embodiment, the second focus detection unit of the refocus method performs the second filter processing and the second shift processing on the first focus detection signal and the second focus detection signal, and adds them to generate a shift addition signal. . Then, a contrast evaluation value is calculated from the shift addition signal, and a second defocus amount is detected from the contrast evaluation value.

  In the imaging device of this embodiment, as shown in FIGS. 4 and 5, the imaging pixel is obtained by adding the light beam received by the first focus detection pixel and the light beam received by the second focus detection pixel. The light beam is received. Unlike the first focus detection using the phase difference method, the second focus detection using the refocus method performs focus detection using a shift addition signal (refocus signal) of the first focus detection signal and the second focus detection signal. Therefore, since the light beam corresponding to the shift addition signal used in the second focus detection and the light beam corresponding to the imaging signal substantially coincide, each aberration of the imaging optical system (spherical aberration, astigmatism, coma aberration, etc.) The influence on the shift addition signal and the influence on the imaging signal are substantially the same. Therefore, the detection focus position (position where the second detection defocus amount is 0) calculated by the refocus second focus detection and the best focus position of the imaging signal (MTF peak position of the imaging signal) are approximately Therefore, the focus detection can be performed with higher accuracy than the first focus detection using the phase difference method.

  An example of the first focus detection signal (broken line) and the second focus detection signal (solid line) at the best focus position of the image pickup signal at the peripheral image height of the image pickup device of the present embodiment shown in FIG. FIG. 15 shows the first focus detection signal (broken line) and the second focus detection signal (solid line) after applying the above. In addition, the first focus detection signal (broken line) and the second focus detection signal (solid line) after the second filter processing are relatively shifted by -2, -1, 0, 1, 2, and shifted to add. An example of the addition signal (refocus signal) is shown in FIG. It can be seen that the peak value of the shift addition signal changes as the shift amount changes. An example of the contrast evaluation value (second evaluation value) calculated from each shift addition signal is shown in FIG.

  FIG. 12 shows an example of the second defocus amount (solid line) by the second focus detection of the refocus method in the present embodiment. The horizontal axis is the set defocus amount, and the vertical axis is the detected defocus amount. The first focus detection signal and the second focus detection signal shown in FIG. 10 are the first focus detection signal and the second focus detection signal when the set defocus amount is 0 [mm] in FIG. It can be seen that at the best focus position with the set defocus amount 0, the second defocus amount by the second focus detection is suppressed to be smaller than the first defocus amount by the first focus detection, and the focus detection can be performed with high accuracy.

Therefore, in the present embodiment, the refocus second focus detection is more accurate than the phase difference first focus detection in the vicinity of the best focus position with the set defocus amount 0 of the imaging optical system. Focus detection is possible.
[Refocusable range]
On the other hand, since there is a limit to the refocusable range, the range of the defocus amount that can be detected with high accuracy by the refocus second focus detection is limited.

  A schematic explanatory diagram of a refocusable range in the present embodiment is shown in FIG. If the allowable circle of confusion is δ and the aperture value of the imaging optical system is F, the depth of field at the aperture value F is ± Fδ. On the other hand, the effective aperture value F01 (F02) in the horizontal direction of the pupil partial region 501 (502) narrowed by dividing NH × NV (2 × 1) becomes dark as F01 = NHF. The effective depth of field for each first focus detection signal (second focus detection signal) is ± NHFδ and NH times deep, and the focusing range is extended NH times. Within the range of effective depth of field ± NHFδ, a focused subject image is acquired for each first focus detection signal (second focus detection signal). Therefore, the refocusing process for refocusing (refocusing) after shooting is performed by the refocusing process of translating the first focus detection signal (second focus detection signal) along the principal ray angle θa (θb) shown in FIG. )can do. Therefore, the defocus amount d from the imaging surface where the focus position can be readjusted (refocused) after shooting is limited, and the refocusable range of the defocus amount d is approximately the range of Expression (3). .

| D | ≦ NHFδ (3)
The permissible circle of confusion δ is defined by δ = 2ΔX (the reciprocal of the Nyquist frequency 1 / (2ΔX) of the pixel period ΔX). If necessary, the reciprocal of the Nyquist frequency 1 / (2ΔXAF) of the period ΔXAF (= 6ΔX: in the case of 6 pixel addition) of the first focus detection signal (second focus detection signal) after the second pixel addition processing is allowed to be perturbed. It may be used as a circle δ = 2ΔXAF.

  The range of the defocus amount at which the refocus second focus detection can be performed with high accuracy is generally limited to the range of the expression (3), and the defocus range where the focus detection can be performed with high accuracy by the second focus detection is This is the range below the defocus range in which the first focus detection of the phase difference method can be performed. As shown in FIG. 6, the relative shift amount and defocus amount in the horizontal direction between the first focus detection signal and the second focus detection signal are approximately proportional.

  Therefore, the present embodiment is configured such that the shift range of the second shift process of the refocus second focus detection is equal to or smaller than the shift range of the first shift process of the phase difference first focus detection. Therefore, when there is no in-focus position within the shift range of the second shift process of the second focus detection by the refocus method due to movement of the subject or the like, the contrast evaluation value (second evaluation value) as shown in FIG. 19 is obtained.

  In the focus detection of this embodiment, the first focus detection is performed to adjust the focus from the large defocus state to the small defocus state of the imaging optical system, and the vicinity of the best focus position from the small defocus state of the imaging optical system. The second focus detection is performed in order to adjust the focus up to. Therefore, it is desirable that the pass band of the second filter processing of the second focus detection includes a higher frequency band than the pass band of the first filter processing of the first focus detection. In addition, it is desirable that the pixel addition number in the second pixel addition process for the second focus detection is equal to or less than the pixel addition number in the first pixel addition process for the first focus detection.

As described above, when the aperture value of the imaging optical system is equal to or smaller than the predetermined aperture value (predetermined F value), the focus detection accuracy of the first focus detection of the phase difference method may decrease. Therefore, if necessary, when the aperture value of the imaging optical system is equal to or smaller than the predetermined aperture value, the second defocus amount is set by the refocus second focus detection in addition to the phase difference first focus detection. It is desirable to detect and perform highly accurate focus detection.
[Processing flow of focus detection processing]
A focus detection processing flow of this embodiment is shown in FIG. In the present embodiment, the lens is driven by performing the first focus detection of the phase difference method until the absolute value of the defocus amount of the imaging optical system becomes a predetermined value 1 or less (first predetermined value or less), and the lens is driven. The focus is adjusted from the large defocus state to the small defocus state of the system. Thereafter, the lens is driven by performing the second focus detection of the refocus method until the absolute value of the defocus amount of the imaging optical system is equal to or smaller than a predetermined value 2 (<predetermined value 1) (second predetermined value). Focus adjustment is performed from the small defocus state of the imaging optical system to the vicinity of the best focus position.

  In step S100, the first detection defocus amount (Def1) is detected by the first focus detection by the phase difference method. When the detected magnitude | Def1 | of the first defocus amount (Def1) is larger than the predetermined value 1 in step S101, the process proceeds to step S102, and the lens is set according to the first defocus amount (Def1). Driving is performed, and the process returns to step S100. On the other hand, when the magnitude | Def1 | of the first defocus amount (Def1) detected in step S100 is equal to or smaller than the predetermined value 1, the process proceeds to step S200.

  In step S200, the second detection defocus amount (Def2) is detected by the second focus detection by the refocus method. In step S201, it is determined whether or not the magnitude | Def2 | of the second defocus amount (Def2) is larger than a maximum drive defocus amount (Def_FL, maximum drive amount) indicating a driveable range of the focus lens. When the magnitude | Def2 | of the second defocus amount (Def2) detected in step S200 is larger than the maximum drive defocus amount (Def_FL), it is determined that focus adjustment by driving the focus lens cannot be performed. Then, the process proceeds to step S204, and it is determined whether or not a focused image can be generated by the refocus process. If the magnitude | Def2 | of the second defocus amount (Def2) is equal to or smaller than the maximum drive defocus amount (Def_FL) in step S201, it is determined that the focus adjustment by driving the focus lens can be performed, and the process proceeds to step S202. And migrate.

  In step S202, it is determined whether or not the magnitude | Def2 | of the second defocus amount (Def2) is equal to or smaller than a predetermined value 2 (<predetermined value 1). If the magnitude | Def2 | of the second defocus amount (Def2) is larger than the predetermined value 2 (<predetermined value 1), the lens is driven according to the second defocus amount (Def2) in step S203, and the step Return to S200. On the other hand, when the magnitude | Def2 | of the second defocus amount (Def2) is equal to or smaller than the predetermined value 2, the focus adjustment operation ends.

  In step S204, the magnitude | Def2−Def_FL | of the difference between the second defocus amount (Def2) and the maximum drive defocus amount (Def_FL) is adjusted from the imaging surface where the focus position can be readjusted (refocused). It is determined whether or not the focus amount is greater than d ′. If | Def2−Def_FL | is equal to or smaller than the adjustment defocus amount d ′ (within the adjustment range), it is determined that the focus position can be readjusted (refocus), and the process proceeds to step S205. If | Def2−Def_FL | is larger than the adjustment defocus amount d ′, it is not within the range where the focus position can be readjusted (refocused), so it is determined that the focus is NG and the focus adjustment operation is terminated.

  In step S205, the lens is driven according to the maximum driving defocus amount (Def_FL) of the focus lens driving unit of the present embodiment. Then, in order to perform the refocus process, the process proceeds to step S206.

  In step S206, the image signal acquired at the position where the focus lens is driven by the maximum drive defocus amount (Def_FL) in step S205 is re-resolved using the defocus amount of the difference between (Def2) and (Def_FL). Perform focus processing. Then, a focused image is generated, and the focus adjustment operation is terminated. The refocus processing is as described above with reference to FIG.

  With the above configuration, it is possible to suppress the difference between the detected in-focus position calculated from the focus detection signal and the best in-focus position of the imaging signal, and to perform highly accurate focus adjustment. Further, even if the second detection defocus amount calculated from the contrast evaluation value calculated by the second focus detection means is larger than the maximum driving defocus amount of the focus lens, focus adjustment is not impossible, and high-precision focus adjustment is possible. It becomes.

(Second Embodiment)
FIG. 21 is a flowchart illustrating an outline of the flow of focus detection processing according to the second embodiment. In this embodiment, the second defocus amount (Def2) is larger than the maximum driving defocus amount (Def_FL) of the focus lens, and the adjustment defocus amount d from the imaging surface where the focus position can be readjusted (refocused). It is an example when it is smaller than '. In such a case, a refocus process is performed using the second defocus amount (Def2) without driving the focus lens, and a focused image is generated.

  Steps S300 to S302 in FIG. 21 are the same as steps S100 to S102 in FIG. Steps S400 to S404 are the same as steps S200 to S204 in FIG.

  In step S405, the adjustment defocus that allows the magnitude | Def2-Def_FL | of the difference between the second defocus amount (Def2) and the maximum drive defocus amount (Def_FL) in step S404 to readjust the focus position (refocus). This is performed when the amount is less than d ′.

  In step S405, it is determined whether or not the second defocus amount (Def2) is larger than the adjustment defocus amount d ′ that allows the focus position to be readjusted (refocused), and whether or not the focus lens drive is necessary. To do. If the second defocus amount (Def2) is larger than the adjustment defocus amount d ′ that allows the focus position to be readjusted (refocused), it is necessary to move the focus lens to a range where the refocus processing can be performed. Migrate to

  In step S406, the focus lens is driven, and the process proceeds to step S407 to perform a refocus process. In this case, the defocus amount used in the refocus processing in step S407 is a defocus amount that is the difference between the second defocus amount (Def2) and the maximum drive defocus amount (Def_FL).

  On the other hand, when the second defocus amount (Def2) is equal to or smaller than the adjustment defocus amount d ′ that allows the focus position to be readjusted (refocused), it is determined that the refocus processing can be performed without driving the focus lens. Then, the process proceeds to step S407. In this case, since the focus lens drive is not performed, the defocus amount used in the refocus processing in step S407 is the second defocus amount (Def2).

  In step S407, a refocus process is performed using the defocus amount acquired in step S405 or step S406 to generate a focused image, and the focus adjustment operation ends. The refocus processing is as described above with reference to FIG. Other than the above, the second embodiment is the same as the first embodiment.

With the above configuration, it is possible to suppress the difference between the detected in-focus position calculated from the focus detection signal and the best in-focus position of the imaging signal, and to perform highly accurate focus adjustment. Further, even if the second defocus amount calculated from the contrast evaluation value calculated by the second focus detection means is larger than the maximum drive defocus amount, focus adjustment is not impossible, and highly accurate focus adjustment is possible. Further, when the second defocus amount calculated from the contrast evaluation value calculated by the second focus detection means is larger than the maximum driving defocus amount of the focus lens, high-speed and high-precision focus adjustment without driving the focus lens. Is possible.
(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

200: pixel group, 200R, 200G, 200B: pixel, 201, 202: focus detection pixel, 501: first pupil partial region, 502: second pupil partial region

Claims (14)

A first focus detection pixel that receives a light beam passing through the first pupil partial region of the imaging optical system, and a second pupil partial region of the imaging optical system that is different from the first pupil partial region. A second focus detection pixel that receives a light beam that passes through, and an image sensor that receives a light beam that passes through a pupil region obtained by combining the first pupil partial region and the second pupil partial region of the imaging optical system. An image sensor having a plurality of pixels arranged;
First focus adjustment means for performing phase difference type focus adjustment based on a first signal obtained from the first focus detection pixel and a second signal obtained from the second focus detection pixel. When,
Contrast based on an addition signal generated by shifting and adding the first signal obtained from the first focus detection pixel and the second signal obtained from the second focus detection pixel. A second focus adjusting means for performing focus adjustment of the detection method;
The focus adjustment from the large defocus state to the small defocus state of the imaging optical system is performed using the first focus adjustment unit, and the focus adjustment from the small defocus state to the vicinity of the best focus position is performed. Control means for performing control using the second focus adjustment means,
The control means determines that the difference between the defocus amount detected by the second focus adjustment means and the maximum drive amount of the focus lens of the imaging optical system is the first signal by the second focus adjustment means. And an image pickup apparatus that causes the second focus adjustment means to perform focus adjustment by the addition processing when the addition processing for shifting and adding the second signals is within a range in which focus adjustment is possible. .   The defocus amount detected by the second focus adjustment means is larger than the maximum drive amount of the focus lens of the imaging optical system, and the defocus amount detected by the second focus adjustment means and the image formation When the difference from the maximum drive amount of the focus lens of the optical system is within a range in which focus adjustment can be performed by the addition processing by the second focus adjustment unit, the control unit moves the focus lens to the maximum drive amount. The imaging apparatus according to claim 1, wherein after being driven, the second focus adjustment unit performs focus adjustment by the addition process.   The defocus amount detected by the second focus adjustment means is larger than the maximum drive amount of the focus lens of the imaging optical system, and the focus adjustment is possible by the addition processing by the second focus adjustment means. 2. The imaging according to claim 1, wherein the control unit causes the second focus adjustment unit to perform focus adjustment by the addition process without driving the focus lens when the value is within the range. apparatus.   After the focus adjustment by the first focus adjustment unit is performed until the absolute value of the defocus amount is equal to or less than the first predetermined value, the focus adjustment by the second focus detection unit is performed by using the absolute value of the defocus amount. The imaging apparatus according to claim 1, wherein the imaging device is performed until the value becomes equal to or smaller than a second predetermined value that is smaller than the first predetermined value.   The first focus adjusting unit calculates a correlation amount by performing a first filter process and a first shift process on the first signal and the second signal, and calculates a first decimation from the correlation amount. In addition to detecting the focus amount, the second focus adjusting unit performs a second filter process and a second shift process on the first signal and the second signal, and adds them to obtain the added signal. The imaging apparatus according to claim 1, wherein the imaging device generates, calculates a contrast evaluation value from the addition signal, and detects a second defocus amount from the contrast evaluation value.   The imaging apparatus according to claim 5, wherein a pass band of the second filter process includes a frequency band higher than a pass band of the first filter process. A first focus detection pixel that receives a light beam passing through the first pupil partial region of the imaging optical system, and a second pupil partial region of the imaging optical system that is different from the first pupil partial region. A second focus detection pixel that receives a light beam that passes through, and an image sensor that receives a light beam that passes through a pupil region obtained by combining the first pupil partial region and the second pupil partial region of the imaging optical system. A method for controlling an imaging device including an imaging device in which a plurality of pixels are arranged,
A first focus adjustment step of performing phase difference type focus adjustment based on a first signal obtained from the first focus detection pixel and a second signal obtained from the second focus detection pixel; When,
Contrast based on an addition signal generated by shifting and adding the first signal obtained from the first focus detection pixel and the second signal obtained from the second focus detection pixel. A second focus adjustment step for performing detection-type focus adjustment;
The focus adjustment from the large defocus state to the small defocus state of the imaging optical system is performed in the first focus adjustment step, and the focus adjustment from the small defocus state to the vicinity of the best focus position is performed in the second focus adjustment step. And a control process for performing control in the focus adjustment process.
In the control step, the difference between the defocus amount detected in the second focus adjustment step and the maximum drive amount of the focus lens of the imaging optical system is determined by the second focus adjustment step. When the addition processing for shifting and adding the second signal is within a range where focus adjustment is possible, the imaging device is characterized in that focus adjustment by the addition processing is performed in the second focus adjustment step. Control method.   The defocus amount detected by the second focus adjustment step is larger than the maximum drive amount of the focus lens of the imaging optical system, and the defocus amount detected by the second focus adjustment step and the image formation When the difference from the maximum drive amount of the focus lens of the optical system is within a range in which the focus adjustment can be performed by the addition process by the second focus adjustment step, the control step is configured to move the focus lens to the maximum drive amount. 8. The method of controlling an imaging apparatus according to claim 7, wherein after the driving, the focus adjustment by the addition process is performed in the second focus adjustment step.   The defocus amount detected by the second focus adjustment step is larger than the maximum drive amount of the focus lens of the imaging optical system, and the focus adjustment can be performed by the addition processing by the second focus adjustment step. 8. The imaging according to claim 7, wherein in the case of being within a range, the focus adjustment by the addition process is performed in the second focus adjustment step without driving the focus lens in the control step. 9. Control method of the device.   After performing the focus adjustment in the first focus adjustment process until the absolute value of the defocus amount is equal to or less than the first predetermined value, the focus adjustment in the second focus detection process is performed using the absolute value of the defocus amount. The method according to claim 7, wherein the control is performed until the value becomes equal to or less than a second predetermined value that is smaller than the first predetermined value.   In the first focus adjustment step, a correlation amount is calculated by performing a first filter process and a first shift process on the first signal and the second signal, and the first defocusing process calculates a correlation value. In addition to detecting the focus amount, in the second focus adjustment step, the first signal and the second signal are subjected to a second filter process and a second shift process and added to obtain the added signal. 8. The method according to claim 7, further comprising: generating a contrast evaluation value from the added signal, and detecting a second defocus amount from the contrast evaluation value.   The method of controlling an imaging apparatus according to claim 11, wherein the pass band of the second filter processing includes a frequency band higher than the pass band of the first filter processing.   The program for making a computer perform each process of the control method of any one of Claims 8 thru | or 12.   A computer-readable storage medium storing a program for causing a computer to execute each step of the control method according to any one of claims 8 to 12.

Images