JP6890937B2 - Focus detector, image pickup device, and focus detection method - Google Patents

Description

The present invention is a focus detection apparatus, imaging apparatus, and relates to a focus detecting method and, more particularly, to an automatic focus detection technique.

A phase difference focus detection method (phase difference AF) is known as an automatic focus detection (AF) method for an image pickup apparatus. Phase-difference AF is AF that is often used in video cameras and digital still cameras, and there are some that use an image sensor as a focus detection sensor. Since phase-difference AF uses an optical image to detect the focus, the aberration of the optical system that forms the optical image may give an error to the focus detection result, and a method for reducing such an error is available. Proposed.

For example, Patent Document 1 discloses a method of correcting a focus detection error due to the shapes of a pair of optical images formed by a pair of focus detection light fluxes not matching due to aberration of an optical system in a focused state. Has been done.

Japanese Unexamined Patent Publication No. 2013-171251

However, in the conventional method, the correction that depends on the color, direction, and spatial frequency of the subject and the correction that depends on the phase difference AF are collectively corrected, so that the correction accuracy may not be sufficient. Further, in Patent Document 1, the amount of defocus between the best image plane and the planned focal plane is detected and corrected. Therefore, the correction depending on the color, direction, and spatial frequency of the subject and the correction depending on the phase difference AF are collectively corrected, and the calculated correction value becomes large. For this reason, the influence of the correction value calculation error becomes large, and the correction accuracy is not sufficient.

In view of the above problems, the present invention makes the focus detection error of the phase difference AF highly accurate by separately correcting the correction depending on the color, direction, and spatial frequency of the subject and the correction depending on the phase difference AF. It is an object of the present invention to provide a correctable focus detection method.

In order to solve the above problems, the focus detection device of the present invention photoelectrically converts light beams that have passed through different pupil regions of the imaging optical system, and outputs a plurality of pixels capable of outputting a pair of photoelectric conversion signals. From the image pickup means, the acquisition means for acquiring the aberration information of the photographing optical system, the imaging focus position calculated from the image characteristics or the evaluation characteristics of the image from the acquired aberration information, and the focus detection characteristics of the focus detection means. The first correction value is calculated from the calculated focus detection focus position, and is a correction value according to the difference in the amount of center of gravity shift caused by the shapes of the pair of line image intensity distributions being different from each other. calculating a second correction value from the pair of phase difference focus detection in-focus position which based on the line image intensity distribution of the photographing optical system corresponding to the photoelectric conversion unit is detected by the phase difference focus detection method of the image pickup means in and , A calculation means for calculating the focus detection correction value from the first correction value and the second correction value, and
Have.

According to the present invention, the focus detection error of the phase difference AF due to the aberration of the optical system can be accurately corrected by separately correcting the correction depending on the color, direction, and spatial frequency of the subject and the correction depending on the phase difference AF. A correctable focus detection method can be provided.

It is a block diagram of a digital camera as an example of an image pickup apparatus. It is a figure which shows the structural example of the image sensor. It is a figure which shows the relationship between a photoelectric conversion region and an exit pupil. It is a block diagram which shows the structure of a TVAF part. It is a flowchart which shows the AF operation. It is a flowchart which shows the process of calculating a focus detection correction value. It is a figure which shows an example of a focal point detection area. It is a figure which shows the calculation process of the difference between the in-focus position of a photographed image, and the focus detection focus position. It is a figure explaining the amount of the center of gravity shift of a line image intensity distribution by defocus. It is a figure which shows the line image intensity distribution when the difference between the amount of center of gravity shift and the correlation calculation result is large. It is a figure which shows the shading by the pupil deviation of a pair of line image intensity distributions. It is a figure which shows an example of a filter frequency band. It is a figure which shows that the manufacturing error of the 2nd correction value changes according to the image plane tilt. It is a figure which shows that the manufacturing error of the 2nd correction value changes according to the image plane tilt. It is a figure which shows that the manufacturing error of the 2nd correction value changes according to the image plane tilt. It is a figure explaining that the focus detection error of a phase difference AF can be corrected with high accuracy. It is a flowchart which shows the focus detection correction value calculation which concerns on 2nd Embodiment.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. The embodiment has a specific and specific configuration in order to facilitate understanding and explanation of the invention, but the present invention is not limited to such a specific configuration. For example, although the embodiment in which the present invention is applied to a single-lens reflex type digital camera with interchangeable lenses will be described below, the present invention can also be applied to a digital camera of a non-interchangeable lens type and a video camera. It can also be carried out on any electronic device equipped with a camera, such as a mobile phone, a personal computer (laptop, tablet, desktop type, etc.), a game machine, or the like.

(First Embodiment)
(Explanation of the configuration of the imaging device-lens unit)
FIG. 1 is a block diagram showing a functional configuration of a digital camera as an example of an imaging device according to the present embodiment. The digital camera of the present embodiment is a single-lens reflex camera with interchangeable lenses, and has a lens unit 100 and a camera body 120. The lens unit 100 is attached to the camera body 120 via the mount M shown by the dotted line in the center of the figure. The digital camera of the present embodiment will be described by taking an interchangeable lens single-lens reflex camera as an example, but the present invention is not limited to this, and for example, a camera with an integrated lens may be used.

The lens unit 100 includes an optical system (first lens group 101, aperture 102, second lens group 103, focus lens group (hereinafter, simply referred to as “focus lens”) 104), and a drive / control system. In the present embodiment, the lens unit 100 is a photographing lens that includes a focus lens 104 and forms an optical image of a subject. In this embodiment, the lens unit 100 constitutes a control means.

The first lens group 101 is arranged at the tip of the lens unit 100 on the subject side and is movably held in the optical axis direction OA. The aperture 102 functions not only as a function of adjusting the amount of light during shooting, but also as a mechanical shutter for controlling the exposure time during shooting of a still image. The aperture 102 and the second lens group 103 can be integrally moved in the optical axis direction OA, and the zoom function is realized by moving in conjunction with the first lens group 101. The focus lens 104 can also be moved in the optical axis direction OA, and the subject distance (focusing distance) at which the lens unit 100 focuses changes depending on the position. By controlling the position of the focus lens 104 in the optical axis direction OA, the focus adjustment for adjusting the focusing distance of the lens unit 100 is performed.

The drive / control system includes a zoom actuator 111, an aperture actuator 112, a focus actuator 113, a zoom drive circuit 114, an aperture aperture drive circuit 115, a focus drive circuit 116, a lens MPU 117, and a lens memory 118. The zoom drive circuit 114 drives the first lens group 101 and the third lens group 103 in the optical axis direction OA by using the zoom actuator 111, and controls the angle of view of the optical system of the lens unit 100. The aperture shutter drive circuit 115 drives the aperture 102 using the aperture actuator 112, and controls the aperture diameter and opening / closing operation of the aperture 102. The focus drive circuit 116 drives the focus lens 104 in the optical axis direction OA by using the focus actuator 113, and controls the focusing distance of the optical system of the lens unit 100. Further, the focus drive circuit 116 detects the current position of the focus lens 104 by using the focus actuator 113.

The lens MPU (processor) 117 performs all calculations and controls related to the lens unit 100, and controls the zoom drive circuit 114, the aperture drive circuit 115, and the focus drive circuit 116. Further, the lens MPU 117 is connected to the camera MPU 125 through the mount M to communicate commands and data. For example, the lens MPU 117 detects the position of the focus lens 104 and notifies the lens position information in response to a request from the camera MPU 125. This lens position information includes the position of the focus lens 104 in the optical axis direction OA, the position and diameter of the exit pupil in the optical axis direction OA when the optical system is not moving, and the optical axis of the lens frame that limits the light beam of the exit pupil. Includes information such as position and diameter in direction OA. Further, the lens MPU 117 controls the zoom drive circuit 114, the aperture drive circuit 115, and the focus drive circuit 116 in response to a request from the camera MPU 125. The lens memory 118 stores in advance optical information necessary for automatic focus detection. The camera MPU 125 controls the operation of the lens unit 100 by, for example, executing a program stored in the built-in non-volatile memory or the lens memory 118.

(Explanation of the configuration of the imaging device-camera body)
The camera body 120 has an optical system (optical low-pass filter 121 and an image sensor 122) and a drive / control system. The first lens group 101, the aperture 102, the second lens group 103, the focus lens 104 of the lens unit 100, and the optical low-pass filter 121 of the camera body 120 constitute a photographing optical system.

The optical low-pass filter 121 reduces false colors and moire of captured images. The image sensor 122 is composed of a CMOS image sensor and peripheral circuits, and is arranged with m pixels in the horizontal direction and n pixels in the vertical direction (n and m are integers of 2 or more). The image pickup device 122 of the present embodiment has a pupil division function, and can perform phase-difference AF using image data. The image processing circuit 124 generates data for phase difference AF and image data for display, recording, and contrast focus detection methods (contrast AF, TVAF) from the image data output by the image pickup element 122.

The drive / control system includes an image sensor drive circuit 123, an image processing circuit 124, a camera MPU 125, a display 126, an operation switch group 127, a memory 128, a phase difference AF unit 129, and a TVAF unit 130. The image sensor drive circuit 123 controls the operation of the image sensor 122, A / D converts the acquired image signal, and transmits the acquired image signal to the camera MPU 125. The image processing circuit 124 performs general image processing performed by a digital camera, such as γ conversion, white balance adjustment processing, color interpolation processing, and compression coding processing, on the image data acquired by the image pickup element 122. The image processing circuit 124 also generates a signal for phase difference AF.

The camera MPU (processor) 125 performs all calculations and controls related to the camera body 120, and performs sensor drive circuit 123, image processing circuit 124, display 126, operation switch group 127, memory 128, phase difference AF unit 129, and TVAF. The unit 130 is controlled. The camera MPU 125 is connected to the lens MPU 117 via the signal line of the mount M, and communicates commands and data with the lens MPU 117. Further, the camera MPU 125 issues a lens position acquisition request, an aperture with a predetermined drive amount, a focus lens, a zoom drive request, a request for acquisition of optical information unique to the lens unit 100, and the like to the lens MPU 117. Further, the camera MPU 125 has a built-in ROM 125a that stores a program that controls camera operation, a RAM 125b that stores variables, and an EEPROM 125c that stores various parameters.

The display 126 is composed of an LCD or the like, and displays information on a shooting mode of the camera, a preview image before shooting, a confirmation image after shooting, an in-focus state display image at the time of focus detection, and the like. The operation switch group 127 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The memory 128 as the recording means of the present embodiment is a detachable flash memory for recording captured images.

The phase difference AF unit 129 performs focus detection processing by phase difference AF using the focus detection data obtained by the image processing circuit 124. More specifically, the image processing circuit 124 generates a pair of image data formed by light beams passing through the pair of pupil regions of the photographing optical system as focus detection data, and the phase difference AF unit 129 is the pair. The amount of focus shift is detected based on the amount of shift of the image data of. As described above, the phase difference AF unit 129 of the present embodiment performs phase difference AF (imaging surface phase difference AF) based on the output of the image pickup device 122 without using a dedicated AF sensor. The operation of the phase difference AF unit 129 will be described in detail later.

The TVAF unit 130 performs focus detection processing of contrast AF based on the evaluation value for TVAF (contrast information of image data) generated by the image processing circuit 124. In the focus detection process of contrast AF, the focus lens 104 is moved to detect the focus lens position where the evaluation value peaks as the in-focus position. As described above, the digital camera of the present embodiment can execute both phase difference AF and contrast AF, and can be selectively used or used in combination depending on the situation.

(Explanation of focus detection operation: phase difference AF)
Next, the operations of the phase difference AF unit 129 and the TVAF unit 130 will be further described. First, the operation of the phase difference AF unit 129 will be described. FIG. 2A is a diagram showing a pixel array of the image sensor 122 according to the present embodiment, and covers a range of 6 rows in the vertical direction (Y direction) and 8 columns in the horizontal direction (X direction) of the two-dimensional C-MOS area sensor. , The state observed from the lens unit 100 side is shown. The image pickup element 122 is provided with a Bayer array color filter, and green (G) and red (R) color filters are alternately applied to the pixels in the odd rows in order from the left, and the color filters in the even rows are from the left. Blue (B) and green (G) color filters are arranged alternately in this order. In the pixel 211, the circle 211i represents an on-chip microlens, and the plurality of rectangles 211a and 211b arranged inside the on-chip microlens are photoelectric conversion units, respectively.

In the image pickup device 122 of the present embodiment, the photoelectric conversion units of all the pixels are divided into two in the X direction, and the photoelectric conversion signal of each photoelectric conversion unit and the sum of the photoelectric conversion signals can be read out independently. Further, by subtracting the photoelectric conversion signal of one photoelectric conversion unit from the sum of the photoelectric conversion signals, a signal corresponding to the photoelectric conversion signal of the other photoelectric conversion unit can be obtained. The photoelectric conversion signal in each photoelectric conversion unit may be used as data for phase difference AF, or may be used for generating a parallax image constituting a 3D (3-Dimensional) image. Further, the sum of the photoelectric conversion signals can be used as normal captured image data.

Here, the pixel signal when performing phase difference AF will be described. As will be described later, in the present embodiment, the emission light flux of the photographing optical system is pupilly divided by the microlens 211i of FIG. 2A and the divided photoelectric conversion units 211a and 211b. Then, for a plurality of pixels 211 within a predetermined range arranged in the same pixel row, the outputs of the photoelectric conversion unit 211a are connected and organized, and the AF image A and the outputs of the photoelectric conversion unit 211b are connected and organized. Let the thing be a B image for AF. As the output of the photoelectric conversion units 211a and 211b, a pseudo luminance (Y) signal calculated by adding the outputs of green, red, blue, and green included in the unit array of the color filter is used. However, AF images A and B may be organized for each of the red, blue, and green colors.

By detecting the relative image shift amount of the AF image A and B generated in this way by the correlation calculation, the focus shift amount (defocus amount) in the predetermined region can be detected. In the present embodiment, the sum of the output of one photoelectric conversion unit and the output of all photoelectric conversion units is read from the image pickup element 122. For example, when the sum of the output of the photoelectric conversion unit 211a and the output of the photoelectric conversion units 211a and 211b is read, the output of the photoelectric conversion unit 211b is obtained by subtracting the output of the photoelectric conversion unit 211a from the sum. As a result, both the AF image A and the B image can be obtained, and phase-difference AF can be realized. Since such an image sensor is known, further detailed description thereof will be omitted.

FIG. 2B is a diagram showing a configuration example of a readout circuit of the image pickup device 122 of the present embodiment. Horizontal scanning lines 152a and 152b and vertical scanning lines 154a and 154b are wired at the boundary between the pixels of the horizontal scanning circuit 151 and the vertical scanning circuit 153, and each photoelectric conversion unit signals through these scanning lines. Is read out to the outside.

The image sensor of the present embodiment has the following two types of read modes (first read mode and second read mode) in addition to the above-mentioned in-pixel reading method. Specifically, the first read mode is called an all-pixel read mode, which is a mode for capturing a high-definition still image, and in this case, signals of all pixels are read.

The second read mode is called a thinning read mode, and is a mode for only recording a moving image or displaying a preview image. Since the number of pixels required in this case is smaller than that of all pixels, the pixel group reads only the pixels thinned out to a predetermined ratio in both the X direction and the Y direction. Also, when it is necessary to read at high speed, the thinning read mode is used in the same manner. When thinning out in the X direction, signals are added to improve S / N, and when thinning out in the Y direction, the signal output of the line to be thinned out is ignored. Phase-difference AF and contrast AF are also usually performed based on the signals read in the second read mode.

FIG. 3 is a diagram for explaining the conjugate relationship between the exit pupil surface of the photographing optical system and the photoelectric conversion unit of the image pickup device arranged at zero image height, that is, near the center of the image surface in the image pickup apparatus of the present embodiment. The photoelectric conversion unit in the image sensor and the exit pupil surface of the photographing optical system are designed to have a conjugate relationship by an on-chip microlens. The exit pupil of the photographing optical system generally coincides with the surface on which the iris diaphragm for adjusting the amount of light is placed. On the other hand, the photographing optical system of the present embodiment is a zoom lens having a scaling function, but depending on the optical type, the distance and size of the exit pupil from the image plane change when the scaling operation is performed. FIG. 3 shows a state in which the focal length of the lens unit 100 is at the center of the wide-angle end and the telephoto end. With the exit pupil distance Zep in this state as a standard value, the optimum design of the eccentricity parameter according to the shape of the on-chip microlens and the image height (X, Y coordinates) is made.

In FIG. 3A, the lens unit 100 includes a lens barrel member 101b that holds the first lens group 101, a third lens group 105, and a lens barrel member 104b that holds the focus lens 104. It also includes an opening plate 102a that defines the opening diameter of the diaphragm 102 when it is open, and a diaphragm blade 102b for adjusting the aperture diameter when the diaphragm 102 is closed. The virtual images 101b, 102a, 102b, and 104b, which act as limiting members for the light flux passing through the photographing optical system, show an optical virtual image when observed from the image plane. Further, the synthetic aperture in the vicinity of the aperture 102 is defined as the exit pupil of the lens, and the distance from the image plane is defined as Zep as described above.

The pixel 211 is arranged near the center of the image plane, and is referred to as a central pixel in the present embodiment. From the bottom layer, the central pixel 211 is composed of photoelectric conversion units 211a and 211b, wiring layers 211e to 211g, color filters 211h, and on-chip microlens 211i. Then, the two photoelectric conversion units are projected onto the exit pupil surface of the photographing optical system by the on-chip microlens 211i. That is, the exit pupil of the photographing optical system is projected onto the surface of the photoelectric conversion unit via the on-chip microlens 211i.

FIG. 3B shows projected images of the photoelectric conversion unit on the exit pupil surface of the photographing optical system, and the projected images on the photoelectric conversion units 211a and 211b are EP1a and EP1b, respectively. Further, in the present embodiment, the image pickup device has a pixel capable of obtaining the output of either one of the two photoelectric conversion units 211a and 211b and the output of the sum of both. The output of the sum of both is a photoelectric conversion of the luminous flux that has passed through both the projection images EP1a and EP1b, which are almost the entire pupil region of the photographing optical system.

In FIG. 3A, when the outermost light flux passing through the photographing optical system is indicated by L, the luminous flux L is regulated by the aperture plate 102a of the diaphragm, and the projected images EP1a and EP1b are vignetting in the photographing optical system. Has hardly occurred. In FIG. 3B, the luminous flux L in FIG. 3A is shown in TL. From the fact that most of the projected images EP1a and EP1b of the photoelectric conversion unit are included in the circle indicated by TL, it can be seen that vignetting is almost not generated. Since the luminous flux L is limited only by the aperture plate 102a of the diaphragm, the TL can be rephrased as 102a. At this time, at the center of the image plane, the vignetting states of the projected images EP1a and EP1b are symmetrical with respect to the optical axis, and the amount of light received by the photoelectric conversion units 211a and 211b is equal.

When performing phase-difference AF, the camera MPU 125 controls the sensor drive circuit 123 so as to read the above-mentioned two types of outputs from the image sensor 122. Then, the camera MPU 125 gives information on the focus detection region to the image processing circuit 124, generates AF A image and B image data from the output of the pixels included in the focus detection region, and is a phase difference AF unit. Order 129 to supply. The image processing circuit 124 generates AF image A and B image data according to this command and outputs the data to the phase difference AF unit 129. Further, the image processing circuit 124 supplies RAW image data to the TVAF unit 130.

As described above, the image sensor 122 constitutes a part of the focus detection device for both the phase difference AF and the contrast AF. In the present embodiment, the configuration in which the exit pupil is divided into two in the horizontal direction has been described as an example, but the exit pupil may be divided into two in the vertical direction for some pixels of the image sensor. Further, the exit pupil may be divided in both the horizontal and vertical directions. By providing pixels that divide the exit pupil in the vertical direction, phase-difference AF corresponding to the contrast of the subject in the vertical direction as well as the horizontal direction becomes possible.

(Explanation of focus detection operation: Contrast AF)
Next, contrast AF (TVAF) will be described with reference to FIG. Contrast AF is realized by the camera MPU 125 and the TVAF unit 130 working together to repeatedly drive the focus lens and calculate the evaluation value. First, when RAW image data is input from the image processing circuit 124 to the TVAF unit 130, the AF evaluation signal processing circuit 401 extracts the green (G) signal from the Bayer array signal and emphasizes the low-luminance component. Gamma correction processing that suppresses high-brightness components is performed. In the present embodiment, the case where the TVAF is performed with the green (G) signal will be described, but all the red (R), blue (B), and green (G) signals may be used. Further, the luminance (Y) signal may be generated by using all RGB colors. The output signal generated by the AF evaluation signal processing circuit 401 is referred to as a luminance signal Y in the following description regardless of the type of signal used.

It is assumed that the focus detection region is set in the region setting circuit 413 from the camera MPU 125. The region setting circuit 413 generates a gate signal that selects a signal within the set region. The gate signal is input to each circuit of the line peak detection circuit 402, the horizontal integration circuit 403, the line minimum value detection circuit 404, the line peak detection circuit 409, the vertical integration circuits 406, 410, and the vertical peak detection circuits 405, 407, and 411. To. Further, the timing at which the luminance signal Y is input to each circuit is controlled so that each focal evaluation value is generated by the luminance signal Y in the focal detection region. In the area setting circuit 413, a plurality of areas can be set according to the focus detection area.

Next, a method of calculating the Y peak evaluation value will be described. The gamma-corrected luminance signal Y is input to the line peak detection circuit 402, and the Y line peak value for each horizontal line is obtained within the focus detection region set in the area setting circuit 413. The output of the line peak detection circuit 402 is vertically peak-held in the focus detection region in the vertical peak detection circuit 405, and a Y peak evaluation value is generated. The Y-peak evaluation value is an effective index for determining a high-luminance subject or a low-light subject.

Next, a method of calculating the Y integral evaluation value will be described. The gamma-corrected luminance signal Y is input to the horizontal integration circuit 403, and the integrated value of Y is obtained for each horizontal line in the focus detection region. Further, the output of the horizontal integration circuit 403 is vertically integrated in the focus detection region in the vertical integration circuit 406 to generate a Y integration evaluation value. The Y integral evaluation value can be used as an index for determining the brightness of the entire focus detection region.

Next, a method of calculating the Max-Min evaluation value will be described. The gamma-corrected luminance signal Y is input to the line peak detection circuit 402, and the Y line peak value for each horizontal line is obtained in the focus detection region. Further, the gamma-corrected luminance signal Y is input to the line minimum value detection circuit 404, and the minimum value of the luminance signal Y is detected for each horizontal line in the focus detection region. The line peak value and the minimum value of the luminance signal Y for each detected horizontal line are input to the subtractor, and (line peak value-minimum value) is input to the vertical peak detection circuit 407. The vertical peak detection circuit 407 vertically holds the peak in the focus detection region and generates a Max-Min evaluation value. The Max-Min evaluation value is an effective index for determining low contrast and high contrast.

Next, a method of calculating the region peak evaluation value will be described. The gamma-corrected luminance signal Y is passed through the BPF 408 to extract a specific frequency component and generate a focal signal. This focus signal is input to the line peak detection circuit 409, and the line peak value for each horizontal line is obtained in the focus detection region. The line peak value is peak-held in the focus detection region by the vertical peak detection circuit 411, and a region peak evaluation value is generated. Since the region peak evaluation value does not change much even if the subject moves within the focus detection region, it is an effective index for restart determination for determining whether or not to shift from the in-focus state to the process of searching for the in-focus again.

Next, a method of calculating the total line integral evaluation value will be described. Similar to the region peak evaluation value, the line peak detection circuit 409 obtains the line peak value for each horizontal line in the focus detection region. The signal inputs the line peak value to the vertical integration circuit 410 and integrates the total number of horizontal scanning lines in the vertical direction within the focus detection region to generate the total line integration evaluation value. The high-frequency all-line integral evaluation value is a main AF evaluation value because the dynamic range is wide and the sensitivity is high due to the effect of integration. Therefore, in the present embodiment, when it is simply described as a focus evaluation value, it means an all-line integral evaluation value.

The AF control unit 151 of the camera MPU 125 acquires each of the above-mentioned focus evaluation values, and moves the focus lens 104 in a predetermined direction along the optical axis direction through the lens MPU 117 by a predetermined amount. Then, various evaluation values described above are calculated based on the newly obtained image data, and the focus lens position where the total line integral evaluation value is the maximum value is detected. In the present embodiment, various AF evaluation values are calculated in the horizontal line direction and the vertical line direction. As a result, focus detection can be performed on the contrast information of the subject in two directions orthogonal to each other, horizontal and vertical.

(Explanation of the flow of focus detection processing)
Next, the automatic focus detection (AF) operation in the digital camera of the present embodiment will be described. After explaining the outline of the AF process, a detailed explanation will be given. In the present embodiment, first, the camera MPU 125 obtains the amount of defocus (defocus amount) by applying phase difference AF or contrast AF to the focus detection region described later. When the focus detection is completed by any of the methods, the camera MPU 125 calculates the focus detection correction value for correcting the result of the automatic focus detection, and corrects the focus detection result. Then, the camera MPU 125 drives the focus lens 104 based on the corrected focus detection result.

Next, the details of the AF process described above will be described with reference to the flowcharts shown in FIGS. 5 and 6. FIG. 5 shows the flow of the entire AF process, and FIG. 6 shows the flow of calculating the focus detection correction value for correcting the result of the automatic focus detection in step S5 of FIG. The following AF processing operations are mainly executed by the camera MPU 125, unless another subject is specified. Further, when the camera MPU 125 drives or controls the lens unit 100 by transmitting a command or the like to the lens MPU 117, the operating subject may be described as the camera MPU 125 for the sake of brevity.

First, in step S1, the camera MPU 125 sets the focus detection region. The focus detection area 219 set here may be determined by the main subject 220 shown in FIG. 7, or may be a preset focus detection area. In the present embodiment, the coordinates (x1, y1) representing the focus detection area 219 are set with respect to the focus detection area. The representative coordinates (x1, y1) at this time may be adjusted to, for example, the position of the center of gravity with respect to the focus detection region 219.

Next, in step S2, the camera MPU 125 acquires a focus detection signal used for automatic focus detection. When the automatic focus detection is phase-difference AF, the AF A image and the photoelectric conversion unit 211b are formed by connecting the outputs of the photoelectric conversion unit 211a for a plurality of pixels 211 within a predetermined range arranged in the same pixel row. The AF B image is acquired by connecting the outputs of. When the automatic focus detection is contrast AF, RAW image data is input to the TVAF unit 130 from the image processing circuit 124. Then, the AF evaluation signal processing circuit 401 acquires a signal that has been subjected to gamma correction processing that extracts the green (G) signal from the Bayer array signal and emphasizes the low-luminance component and suppresses the high-luminance component.

Next, in step S3, the camera MPU 125 performs focus detection based on the above-mentioned phase difference AF or contrast AF processing. Next, in S4, the camera MPU 125 acquires the correction value calculation conditions necessary for calculating the focus detection correction value. The focus detection correction value can be used for changes in the photographing optical system or changes in the focus detection optical system, such as the position of the focus lens 104, the position of the first lens group 101 indicating the zoom state, and the position coordinates (x1, y1) of the focus detection region. It changes with it. Therefore, in step S2, the camera MPU 125 acquires information such as, for example, the position of the focus lens 104, the position of the first lens group 101 indicating the zoom state, and the position coordinates (x1, y1) of the focus detection region. In addition to this, the focus detection correction value changes according to each combination of the contrast direction (horizontal, vertical), color (red, green, blue), and spatial frequency for evaluating the focal state. Therefore, information such as the magnitude of weighting for each combination of contrast direction (horizontal, vertical), color (red, green, blue), and spatial frequency as shown in FIG. 8D, which will be described later, is also acquired.

Next, in step S5, the camera MPU 125 calculates a focus detection correction value for correcting the result of automatic focus detection. Specifically, it is calculated from the difference between the imaging in-focus position calculated from the image characteristics or evaluation characteristics of the captured image, the focus detection in-focus position calculated from the focus detection characteristics of the focus detection means, and the phase difference correction information. The focus detection correction value is calculated from the phase difference focus detection focusing position. Details of the image characteristics or evaluation characteristics of the captured image and the focus detection characteristics of the focus detection means will be described later. The camera MPU 125 functions as a focus detection correction amount calculation means. The details of the focus detection correction value calculation method in step S5 will be described later with reference to FIG.

Next, in step S6, the camera MPU 125 corrects the focus detection result DEF_0 by the following formula using the correction value (BP) for correcting the result of the automatic focus detection calculated in step S5, and after the correction. The focus detection result DEF is calculated.
DEF = DEF_0 + BP

Next, in step S7, the camera MPU 125 drives the focus lens 104 to the in-focus position of the corrected focus detection result DEF. The camera MPU 125 functions as a control means. Next, in step S8, the camera MPU 125 makes a focusing determination, and if it is determined that the camera is out of focus (NO), the process proceeds to step S1 and if it is determined that the camera is in focus (YES), the AF process ends. To do.

(Explanation of focus detection correction value calculation)
Hereinafter, the calculation of the focus detection correction value for correcting the result of the automatic focus detection in step S5 of the flow of the entire AF process described above with reference to FIG. 5 will be described with reference to FIG. Steps S101 to S104 are processes related to calculation of the first correction value which is the difference between the imaging in-focus position and the focus detection in-focus position, and steps S107 to S111 are the focus detection in-focus position and the phase difference focus detection. This is a process related to the calculation of the second correction value, which is the difference in the in-focus position.

First, in step S101 (acquisition step), the camera MPU 125 acquires aberration information. The aberration information in the present embodiment is information representing the aberration state of the optical system, and is, for example, information regarding the imaging position of the photographing optical system for each of the color, direction, and spatial frequency of the subject.

Here, the spatial frequency aberration information stored in the lens memory 118 will be described with reference to FIGS. 8 (A) and 8 (B). FIG. 8A shows the defocus MTF of the photographing optical system. The horizontal axis represents the position of the focus lens 104, and the vertical axis represents the intensity of the MTF. The four types of curves drawn in FIG. 8A are MTF curves for each spatial frequency, and show the case where the spatial frequency changes from the lower to the higher in the order of MTF1, MTF2, MTF3, and MTF4. .. The MTF curve of the spatial frequency F1 (lp / mm) corresponds to the MTF1, and similarly, the spatial frequencies F2, F3, F4 (lp / mm) correspond to the MTF2, MTF3, MTF4. Further, LP4, LP5, LP6, and LP7 indicate the focus lens 104 positions corresponding to the maximum values of the defocus MTF curves.

FIG. 8B is a diagram showing aberration information in this embodiment. FIG. 8B shows the equation of the information MTF_P_RH of the focus lens 104 position showing the maximum value of the defocus MTF of FIG. 8A. The aberration information in the present embodiment is described below, for example, for each of the above-mentioned six combinations of color and direction, with the spatial frequency f and the position coordinates (x1, y1) of the focus detection region on the image sensor as variables. It is expressed by the formula of.
MTF_P_RH (f, x, y) = (rh (0) x x + rh (1) x y + rh (2)) x f2 + (rh (3) x x + rh (4) x y + rh (5)) x f + (rh (6)) × x + rh (7) × y + rh (8)) (1)

The equation (1) shows the equation of the information MTF_P_RH of the focus lens 104 position indicating the maximum value of the defocus MTF for each spatial frequency corresponding to the horizontal (H) direction for the red (R) color signal. , Other combinations are also expressed by the same formula. Further, in the present embodiment, rh (n) (0 ≦ n ≦ 8) is stored in advance in the lens memory 118 of the lens unit 100, and the camera MPU 125 requests the lens MPU 117 to rh (n) (0 ≦ n ≦ n). ≤8) shall be acquired. However, rh (n) (0 ≦ n ≦ 8) may be stored in the non-volatile region of the camera RAM 125b.

Further, as a response to the manufacturing error of the first correction value, the manufacturing error correction information rhd (n) of the first correction value with respect to rh (n) is stored in the non-volatile region of the lens memory 118 or the camera RAM 125b. When performing manufacturing error correction of the first correction value, rhd (n) is acquired from the non-volatile region of the lens memory 118 or the camera RAM 125b, rhd (n) is added to rh (n), and manufacturing error correction is performed. Do. The camera MPU 125 functions as the first manufacturing error correction means of the present embodiment.

Coefficients (rv, gh, gv, bh, bv) in each combination of red and vertical (MTF_P_RV), green and horizontal (MTF_P_GH), green and vertical (MTF_P_GV), blue and horizontal (MTF_P_BH), blue and vertical (MTF_P_BV) Can be memorized and acquired in the same way. In this way, by converting the aberration information into a function and storing the coefficients of each term as aberration information, the amount of data in the lens memory 118 and the camera RAM 125b can be reduced, and changes in the photographing optical system and the focus detection optical system can be dealt with. Aberration information can be stored.

Further, FIG. 8D shows a combination of contrast direction (horizontal, vertical), color (red, green, blue), and spatial frequency for evaluating the focal state of the correction value calculation condition acquired in step S4 of FIG. An example of the magnitude of the weighting is shown. The conditions shown in FIG. 8D are the weighting coefficient used to calculate the imaging in-focus position calculated from the image characteristics or evaluation characteristics of the captured image and the focus detection in-focus position calculated from the focus detection characteristics of the focus detection means. is there.

Here, returning to FIG. 6, in step S102 and step S103, the camera MPU 125 is a combination of the weighting coefficient shown in FIG. 8 (D) acquired in step S4 and the aberration information acquired in step S101. Calculate the focus position. That is, the imaging in-focus position (P_IMG) calculated from the image characteristics or the evaluation characteristics of the captured image, and the focus detection in-focus position (P_AF) calculated from the focus detection characteristics of the focus detection means are calculated. The camera MPU 125 functions as a focusing position calculation means of the present embodiment. Specifically, first, the position information (x1, y1) of the focus detection region is substituted into x and y of the equation (1). By this calculation, the equation (1) is expressed in the form of the following equation (2).
MTF_P_RH (f) = Arh × f2 + Brh × f + Chr (2)

The camera MPU 125 also calculates MTF_P_RV (f), MTF_P_GH (f), MTF_P_GV (f), MTF_P_BH (f), and MTF_P_BV (f) in the same manner. FIG. 8B shows an example of aberration information after substituting the position information of the focus detection region in step S1, where the horizontal axis represents the spatial frequency and the vertical axis represents the maximum value of the defocus MTF. Position (peak position). As shown in the figure, when the chromatic aberration is large, the curves for each color deviate, and when the vertical and horizontal differences are large, the horizontal and vertical curves in the figure deviate. As described above, in the present embodiment, the defocus MTF information corresponding to the spatial frequency is provided for each combination of the color (RGB) and the evaluation direction (H and V).

Next, the camera MPU 125 weights the aberration information with a coefficient (FIG. 8D) that constitutes a weighting coefficient used for calculating the focusing position of the correction value calculation condition acquired in step S4. As a result, the setting information is weighted with respect to the color and direction evaluated by focus detection and imaging. Specifically, the camera MPU 125 calculates the spatial frequency characteristic MTF_P_AF (f) for focus detection and the spatial frequency characteristic MTF_P_IMG (f) for captured images using equations (3) and (4).
MTF_P_AF (f) =
K_AF_R x K_AF_H x MTF_P_RH (f)
+ K_AF_R x K_AF_V x MTF_P_RV (f)
+ K_AF_G x K_AF_H x MTF_P_GH (f)
+ K_AF_G x K_AF_V x MTF_P_GV (f)
+ K_AF_B x K_AF_H x MTF_P_BH (f)
+ K_AF_B x K_AF_V x MTF_P_BV (f) (3)
MTF_P_IMG (f) =
K_IMG_R x K_IMG_H x MTF_P_RH (f)
+ K_IMG_R x K_IMG_V x MTF_P_RV (f)
+ K_IMG_G x K_IMG_H x MTF_P_GH (f)
+ K_IMG_G x K_IMG_V x MTF_P_GV (f)
+ K_IMG_B x K_IMG_H x MTF_P_BH (f)
+ K_IMG_B x K_IMG_V x MTF_P_BV (f) (4)

In FIG. 8C, focus lens positions (peak positions) LP4_AF, LP5_AF, in which the defocus MTF obtained by substituting the discrete spatial frequencies F1 to F4 into the equation (3) has a peak (maximum value), are shown. LP6_AF and LP7_AF are shown on the vertical axis. The camera MPU 125 uses the following equation (5) to express the imaging focus position (P_IMG) calculated from the image characteristics or evaluation characteristics of the captured image and the focus detection focus position (P_AF) calculated from the focus detection characteristics of the focus detection means. ) And (6).

The focus detection focusing position is calculated by using the maximum value information of the defocus MTF for each spatial frequency shown in FIGS. 8 (C) obtained by the equations (3) and (4) and the imaging obtained in step S4 in step S4. Weight and add in the evaluation band of the image and AF. That is, the maximum value information MTF_P_AF (f) and MTF_P_IMG (f) of the defocus MTF for each spatial frequency are weighted and added by the captured image obtained in step S4 and the evaluation band K_IMG_FQ (n) and K_AF_FQ (n) of AF. ..
P_IMG = MTF_P_IMG (1) x K_IMG_FQ (1) + MTF_P_IMG (2) x K_IMG_FQ (2) + MTF_P_IMG (3) x K_IMG_FQ (3) + MTF_P_IMG (4) x K_IMG_FQ (4) (5)
P_AF = MTF_P_AF (1) x K_AF_FQ (1) + MTF_P_AF (2) x K_AF_FQ (2) + MTF_P_AF (3) x K_AF_FQ (3) + MTF_P_AF (4) x K_AF_FQ (4) (6)

Here, the image characteristics or evaluation characteristics of the captured image and the focus detection characteristics of the focus detection means will be described. The image characteristic or evaluation characteristic of the captured image means a characteristic when evaluating the captured image, that is, a characteristic for evaluation when viewed by the human eye. The focus detection characteristic of the focus detection means means a characteristic at the time of focus detection, that is, a characteristic to be evaluated at the time of AF processing.

A specific example is shown below. Regarding the weighting coefficients K_AF_H, K_AF_V, K_IMG_H, and K_IMG_V based on the focus detection information shown in FIG. 8 (D), when the focus detection direction is the pupil division shape as shown in FIG.
K_AF_H = 1
K_AF_V = 0
K_IMG_H = 0.5
K_IMG_V = 0.5
And set. This is because the focus position evaluation by AF processing largely contributes to the aberration due to the horizontal direction H, and the focus position evaluation when viewed by the human eye is focused in the aberration state in which the horizontal direction H and the vertical method V are averaged at a ratio of 1: 1. This is because it is common to determine the position.

Regarding the color weighting coefficients K_AF_R, K_AF_G, K_AF_B, K_IMG_R, K_IMG_G, K_IMG_B, for example,
K_AF_R = 0.25
K_AF_G = 0.5
K_AF_B = 0.25
K_IMG_R = 0.3
K_IMG_G = 0.5
K_IMG_B = 0.2
And set. At the time of focus detection, the focus position is evaluated based on the signal acquired from the sensor of the Bayer array, but the captured image fluctuates due to the influence of the chromatic aberration of each weighted color given by the desired white balance coefficient. Due to.

Regarding the spatial frequency weighting coefficients K_AF_fq (1) to K_AF_fq (4) and K_IMG_fq (1) to K_IMG_fq (4), for example,
AF_fq (1) = 0.8
AF_fq (2) = 0.2
AF_fq (3) = 0
AF_fq (4) = 0
K_IMG_fq (1) = 0
K_IMG_fq (2) = 0
K_IMG_fq (3) = 0.5
K_IMG_fq (4) = 0.5
And set. This is because, in general, the focus position is evaluated in the band having a low spatial frequency at the time of focus detection, and the focused image is evaluated in the band having a high spatial frequency in the captured image.

Here, returning to FIG. 6, in step S104 (first calculation step), the camera MPU 125 has a first correction value (BP) which is a component depending on the color, direction, and spatial frequency of the subject (focus detection correction value (BP)). BP1) is calculated by the following formula (7).
BP1 = P_AF-P_IMG (7)

In the present embodiment, the processing related to the position of the focus detection region, the color of the evaluation signal, and the contrast direction is executed prior to the processing related to the evaluation band. This is because when the photographer determines the position of the focus detection area by setting, the information regarding the position of the focus detection area and the color and direction to be evaluated is rarely changed. On the other hand, the signal evaluation band is frequently changed by the read mode of the image sensor, the digital filter of the AF evaluation signal, and the like. For example, in a low-light environment where the signal S / N decreases, it is conceivable to change the band of the digital filter to a lower band. In this embodiment, in such a case, a coefficient with a low frequency of change (peak coefficient) is calculated and then stored, and only a coefficient with a high frequency of change (evaluation band) is calculated as necessary, and the first correction is performed. Calculate the value. As a result, the amount of calculation can be reduced when the photographer has set the position of the focus detection region.

Next, in step S105, the manufacturing error correction information of the first correction value is held for each state, the manufacturing error correction information corresponding to the focus detection condition is acquired, and the manufacturing error correction is performed. The manufacturing error correction information of the first correction value may be held only in a specific state, and the state not held may be calculated from the rate of change between the states of the first correction value.

(Explanation of focus detection correction value calculation)
Next, in step S106, the camera MPU 125 determines the focus detection method, and if the focus detection method in step S3 is phase-difference AF (YES), the process proceeds to step S107, and if it is not phase-difference AF (NO). The process proceeds to step S114. That is, BP2, which is the difference between the focus detection focus position calculated from the focus detection characteristic of the focus detection means and the phase difference focus detection focus position detected by the phase difference focus detection (phase difference AF), is set to BP2 = 0 and the step is performed. Proceed to S114. In this way, by determining the focus detection method and calculating the focus detection correction value, it is possible to correct the amount of focus shift with high accuracy according to the focus detection method.

Next, in S107, the camera MPU 125 determines the correction value calculation condition. Then, when the difference between the focus detection focusing position (P_AF) calculated from the focus detection characteristic of the focus detection means and the phase difference focus detection focus position (P_AF2) detected by the phase difference AF is small (YES), the step. Proceed to S114. That is, BP2, which is the difference between the focus detection focus position calculated from the focus detection characteristic of the focus detection means and the phase difference focus detection focus position detected by the phase difference AF, is set to BP2 = 0 and the process proceeds to step S114. On the other hand, if the condition is not small (NO), the process proceeds to step S108.

Hereinafter, the condition that the difference between the focus detection focusing position (P_AF) calculated from the focus detection characteristic of the focus detection means and the phase difference focus detection focus position (P_AF2) detected by the phase difference AF is small will be described. The phase difference AF detects the amount of deviation of the center of gravity of the line image intensity distribution due to defocus and calculates the in-focus position. Here, FIG. 9 is a diagram for explaining the amount of deviation of the center of gravity of the line image intensity distribution due to defocus. FIG. 9 shows a state in which there is no vignetting due to the amount of deviation of the center of gravity, the aberration (hereinafter referred to as aberration such as coma) that gives a difference to at least one of the correlation calculation results (the amount of displacement of the line image intensity distribution), and the aperture 102. In the state shown in FIG. 9, there is no difference between the focus detection focusing position (P_AF) calculated from the focus detection characteristic of the focus detection means and the phase difference focus detection focusing position (P_AF2) detected by the phase difference AF.

The defocus positions 1201_P and 1202_P indicate different positions. The pair of line image intensity distributions 1201_A and 1201_B are shown by a pair of line image intensity distributions corresponding to the divided photoelectric conversion units 211a and 211b at the defocus position 1201_P. The pair of line image intensity distributions 1202_A and 1202_B indicate a pair of line image intensity distributions corresponding to the divided photoelectric conversion units 211a and 211b at the defocus position 1202_P. Further, the center-of-gravity positions 1201_GA and 1201_GB indicate the positions of the center of gravity of the pair of line image intensity distributions 1201_A and 1201_B. The center of gravity position 1202_GA and 1202_GB indicate the center of gravity position of the pair of line image intensity distributions 1202_A and 1202_B. Further, the center-of-gravity deviation amount 1201_difG indicates the difference between the center-of-gravity positions 1201_GA and 1201_GB, and the center-of-gravity deviation amount 1202_difG indicates the difference between the center-of-gravity positions 1202_GA and 1202_GB. Further, as shown in FIG. 9, when there is no aberration such as coma or vignetting due to the aperture 102 or the like, the amount of deviation of the center of gravity 1201_difG and 1202_difG increases according to the defocus. By detecting the amount of deviation of the center of gravity, the phase difference AF calculates the amount of defocus.

Next, a case where aberrations such as coma of the photographing optical system and vignetting due to the diaphragm 102 and the like are large will be described. FIG. 10 shows a pair of line image intensity distributions when aberrations such as coma of the photographing optical system and vignetting due to the diaphragm 102 and the like are large. 1301_A shown by the dotted line in FIG. 10 shows the line image intensity distribution corresponding to the photoelectric conversion unit 211a, and 1301_B shown by the solid line shows the line image intensity distribution corresponding to the photoelectric conversion unit 211b. Further, the alternate long and short dash line G_A indicates the position of the center of gravity of 1301_A, and the alternate long and short dash line G_B indicates the position of the center of gravity of 1301_B. As shown in FIG. 10, the line image intensity distributions 1301_A and 1301_B have an asymmetrical shape in which the line image intensity distribution has a tail on one side due to the influence of aberrations such as coma of the optical system. In this way, when the line image intensity distribution has an asymmetrical shape with a tail on one side, the position of the center of gravity of the line image intensity distribution is pulled toward the tailed side, and the center of gravity shifts.

Further, the line image intensity distributions 1301_A and 1301_B are affected by vignetting due to the aperture 102 of the photographing optical system and the like, and a light amount difference occurs between the line image intensity distributions. The line image intensity distribution 1301_A with larger vignetting is more affected by aberrations such as coma, and the degree of asymmetry is larger. As described above, when the degree of asymmetry is different between the line image intensity distribution 1301_A and the line image intensity distribution 1301_B, the deviation amounts of the respective center of gravity positions G_A and G_B are different, and the difference in the amount of deviation of the center of gravity occurs.

The line image intensity distribution 1301_IMG shows a line image intensity distribution corresponding to the sum of the photoelectric conversion signals of the photoelectric conversion units 211a and 211b, which is the sum of the line image intensity distributions 1301_A and 1301_B. The defocus position is different, and the position of the center of gravity of the line image intensity distribution of 1302_A shown by the dotted line and the line image intensity distribution of 1301_B shown by the solid line match. The line image intensity distribution 1302_IMG represents a line image intensity distribution obtained by adding the line image intensity distributions 1302_A and 1302_B.

Comparing the line image intensity distribution 1301_IMG and the line image intensity distribution 1302_IMG, the line image intensity distribution shape of 1301_IMG, which is the sum of the line image intensity distributions with different center of gravity positions, is larger than that of the line image intensity distribution sum 1302_IMG, which has the same center of gravity position. Can be seen to be sharp. The position where the shape of the line image intensity distribution 1301_IMG and 1302_IMG corresponding to the signal of the captured image is the sharpest means the in-focus position. Therefore, it can be said that the states in which the positions of the centers of gravity are different are the focusing positions, and the states in which the positions of the centers of gravity are the same are the positions defocused from the focusing positions.

From this, when the degree of asymmetry differs between the pair of line image intensity distributions and there is a difference in the amount of deviation of the center of gravity, the position where the positions of the centers of gravity match does not become the focusing position, and the positions where the positions of the centers of gravity differ are different. It will be in focus position. As described above, when aberrations such as coma of the photographing optical system such as the line image intensity distributions 1301_A and 1301_B and vignetting due to the aperture 102 and the like are large, the line image intensity distribution is asymmetric in addition to the amount of center of gravity shift due to defocus. There is a difference in the amount of center of gravity shift depending on the degree. As a result, the phase difference AF detects that there is an out-of-focus position at the defocus position that should be detected as in-focus.

Further, in the correlation calculation used when detecting the amount of focus shift by the phase difference AF, a detection error occurs when there is a shape difference such as the line image intensity distributions 1301_A and 1301_B. When there is no shape difference, the correlation amount representing the degree of coincidence of the signals becomes 0 where the pair of line image intensity distributions completely overlap. However, in the case of 1301_A and 1301_B having a shape difference, 1301_A and 1301_B do not completely overlap, and the correlation amount indicating the degree of signal matching does not become 0, and the correlation amount is slightly deviated. Take a minimum value. As described above, when there is a shape difference between the pair of line image intensity distributions, a detection error occurs.

From the above, the condition that the difference between the focus detection focus position (P_AF) calculated from the focus detection characteristic of the focus detection means and the phase difference focus detection focus position (P_AF2) detected by the phase difference AF is small is the imaging optics. This is a case where aberrations such as coma of the system and vignetting due to the aperture 102 and the like are small. Further, when the position coordinates (x1, y1) of the focus detection region are near the center image height, aberrations such as coma of the optical system are small, and vignetting due to the aperture 102 of the optical system is generally small. .. Therefore, even when the position coordinates (x1, y1) of the focus detection region are near the center image height, the focus detection focus position (P_AF) calculated from the focus detection characteristics of the focus detection means and the phase difference AF detects the phase difference. It can be said that the condition is that the difference between the focus detection focusing position (P_AF2) is small.

Next, returning to FIG. 6, in step S108, the camera MPU 125 acquires the phase difference correction information. The phase difference correction information is information related to the phase difference focus detection focusing position detected by the phase difference AF. In the present embodiment, the line image intensity of the photographing optical system corresponding to the divided photoelectric conversion units 211a and 211b at the focus detection focusing position (P_AF) calculated from the focus detection characteristic of the focus detection means calculated in step S103. Obtain the distribution, LSF_A, LSF_B. The line image intensity distribution of the photographing optical system includes the position of the focus lens 104 indicating the defocus state, the position of the first lens group 101 indicating the zoom state, the position coordinates of the focus detection region (x1, y1), and the like. It changes with changes in the system and changes in the focus detection optical system. Therefore, the line image intensity distribution to be acquired is determined based on the correction value calculation condition acquired in step S4.

Next, in step S109, the camera MPU 125 performs shading correction processing (optical correction processing) on LSF_A and LSF_B acquired in step S108, respectively. Here, FIG. 11 shows the relationship between the first pupil region 501 of the photoelectric conversion unit 211a, the second pupil region 502 of the photoelectric conversion unit 211b, and the exit pupil 400 of the imaging optical system at the peripheral image height of the imaging element. Shown. The horizontal direction of the pupil is the X-axis, and the vertical direction of the pupil is the Y-axis.

FIG. 11A is a diagram showing a state in which 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 evenly divided by the first pupil region 501 and the second pupil region 502. On the other hand, when the exit pupil distance Dl of the imaging optical system shown in FIG. 11B is shorter than the set pupil distance Ds of the imaging element, the peripheral image height of the imaging element is the exit pupil of the imaging optical system. The entrance pupil of the image pickup element is displaced, and the exit pupil 400 of the imaging optical system is unevenly divided into pupils. Similarly, when the exit pupil distance Dl of the imaging optical system shown in FIG. 11C is longer than the set pupil distance Ds of the imaging element, the exit pupil of the imaging optical system and the imaging element are measured at the peripheral image height of the imaging element. The exit pupil 400 of the imaging optical system is unevenly divided into pupils due to the pupil shift of the entrance pupil. As the pupil division becomes non-uniform at the peripheral image height, the intensities of LSF_A and LSF_B also become non-uniform, and shading occurs in which the intensity of either LSF_A or LSF_B increases and the intensity of the other decreases.

Returning to FIG. 6, in step S109, the first shading correction coefficient of LSF_A and the second shading correction coefficient of LSF_B are determined according to the image height of the focus detection region, the F value of the imaging lens (imaging optical system), and the exit pupil distance. Shading correction coefficients are generated respectively. The first shading correction coefficient is multiplied by LSF_A, the second shading correction coefficient is multiplied by LSF_B, and shading correction processing (optical correction processing) of LSF_A and LSF_B is performed.

In the present embodiment, the second correction value is calculated based on the correlation between LSF_A and LSF_B (the degree of signal matching). When shading occurs due to pupil displacement, the correlation between LSF_A and LSF_B (the degree of signal matching) may decrease. When shading occurs due to pupil displacement, the correlation between LSF_A and LSF_B (the degree of signal matching) may decrease. Therefore, it is desirable to perform shading correction processing (optical correction processing) in order to improve the correlation (signal matching degree) between LSF_A and LSF_B and improve the focus detection performance.

Next, in step S110, the camera MPU 125 filters LSF_A and LSF_B. Here, an example of the pass band of the filtering process of the present embodiment is shown in FIG. The horizontal axis represents the spatial frequency and the vertical axis represents the filter coefficient. In the present embodiment, it is desirable to adjust the pass band of the filter processing at the time of focus detection according to the evaluation band of the focus detection of the phase difference AF as shown by the solid line or the alternate long and short dash line in FIG.

Next, in step S111, the camera MPU 125 performs a shift process of relatively shifting the filtered LSF_A and LSF_B in the pupil division direction, and calculates a correlation amount representing the degree of signal matching (correlation calculation). In the present embodiment, the k-th LSF_A after the filter processing is A (k), the LSF_B is B (k), and the range of the number k corresponding to the focus detection region is W. The correlation amount COR is calculated by the equation (8), where the shift amount by the shift process is s1 and the shift range of the shift amount s1 is Γ1.

By the shift processing of the shift amount s1, the k-th A (k) and the k-s1st B (k-s1) are associated and subtracted to generate a shift subtraction signal. The absolute value of the generated shift / subtraction signal is calculated, the sum of the numbers k is taken within the range W corresponding to the focus detection region, and the correlation amount COR (s1) is calculated. If necessary, the correlation amount (evaluation value) calculated for each row may be added over a plurality of rows for each shift amount. From the calculated correlation amount, the shift amount of the real value at which the correlation amount is the minimum value is calculated by the sub-pixel calculation, and the image shift amount p1 is calculated. In the present embodiment, the image shift amount p1 is derived based on the correlation amount (correlation calculation) indicating the degree of coincidence between the LSF_A and LSF_B signals, but it may be calculated based on the center of gravity shift amount of the LSF_A and LSF_B signals. Good.

Next, in step S112 (second calculation step), the camera MPU 125 adds the position coordinates (x1, y1) of the focus detection region, the aperture value of the optical system, and the exit pupil distance to the image shift amount p1 calculated in step S111. The second correction value (BP2) is calculated by multiplying the conversion coefficient K according to the above. Next, in step S113, the manufacturing error correction of the second correction value is performed.

In the present embodiment, a case where the manufacturing error correction information of the second correction value is held according to the amount of image plane tilt of the photographing optical system will be described. The camera MPU 125 functions as a second manufacturing error correction means of the present embodiment. Here, FIGS. 13 to 15 show diagrams for explaining that the manufacturing error of the second correction value changes according to the image plane tilt of the photographing optical system. 13 (A) and 14 (A) show the case where the image plane of the photographing optical system is not tilted. FIG. 13 (A) shows the right image height, and FIG. 14 (A) shows the left image height. It shows the situation. The line image intensity distributions 1501_A and 1503_A are line image intensity distributions corresponding to the divided photoelectric conversion units 211a, and the line image intensity distributions 1501_B and 1503_B are line image intensity distributions corresponding to the divided photoelectric conversion units 211b. is there.

13 (B) and 14 (B) show the case where the image plane of the photographing optical system is tilted. FIG. 13 (B) shows the right image height, and FIG. 14 (B) shows the left image height. Represents. The line image intensity distributions 1502_A and 1504_A are line image intensity distributions corresponding to the divided photoelectric conversion units 211a, and the line image intensity distributions 1502_B and 1504_B are line image intensity distributions corresponding to the divided photoelectric conversion units 211b. is there. The lateral aberration amount 1510 represents the lateral aberration amount when there is no image surface tilt, and the lateral aberration amount 1511 represents the lateral aberration amount when there is image surface tilt. Further, the center of gravity positions 1501_G_A to 1504_G_A represent the center of gravity positions of the line image intensity distributions 1501_A to 1504_A, and the center of gravity positions 1501_G_B to 1504_G_B represent the center of gravity positions of the line image intensity distributions 1501_B to 1504_B.

Comparing FIGS. 13 (A) and 14 (A), it can be seen that the line image intensity distribution 1501_A and the line image intensity distribution 1502_B, and the line image intensity distribution 1501_B and the line image intensity distribution 1502A have the same shape. As described above, when there is no image plane tilt, it can be seen that there is no difference in shape only by switching and inverting the line image intensity distributions corresponding to the photoelectric conversion units 211a and 211b at the left and right image heights.

Next, when FIG. 13 (B) and FIG. 13 (A) are compared, the line image intensity distribution 1502_A formed by the light rays mainly passing through the side where the amount of lateral aberration is expanded due to the tilt of the image plane is tailed to the outer side. The shape is changing in the direction of pulling. On the other hand, the shape of the line image intensity distribution 1502_B formed by the light rays mainly passing through the side where the lateral aberration is reduced changes in the direction in which the tail becomes smaller. From this, the line image intensity distribution 1502_G_A moves outward from the line image intensity distribution 1501_G_A, and the line image intensity distribution 1502_G_B moves inward from the line image intensity distribution 1501_G_B.

Next, when FIG. 14 (B) and FIG. 14 (A) are compared, the line image intensity distribution 1504_A formed by the light rays mainly passing through the side where the amount of lateral aberration is expanded due to the tilt of the image plane is tailed to the outer side. The shape is changing in the direction of pulling. On the other hand, the shape of the line image intensity distribution 1504_B formed by the light rays mainly passing through the side where the lateral aberration is reduced changes in the direction in which the tail becomes smaller. From this, the line image intensity distribution 1504_G_A moves outward from the line image intensity distribution 1503_G_A, and the line image intensity distribution 1504_G_A moves inward from the line image intensity distribution 1503_G_A.

FIG. 15A shows a diagram for explaining the difference in the position difference of the center of gravity between the case where there is no image plane tilt at the right image height and the case where there is an image plane tilt. The center of gravity position difference δG1 is the center of gravity position difference between the line image intensity distributions 1501_A and 1501_B when there is no image plane tilt, and the center of gravity position difference δG2 is the center of gravity position difference between the line image intensity distributions 1502_A and 1502_B when there is no image plane tilt. Is shown.

FIG. 15B is a diagram for explaining the difference in the amount of center of gravity shift between the case where there is no image plane tilt at the left image height and the case where there is an image plane tilt. The center of gravity shift amount δG3 indicates the center of gravity shift amount of 1503_A and 1503_B, and the center of gravity shift amount δG4 indicates the center of gravity shift amount of 1504_A and 1504_B. As shown in FIG. 15 (A), the line image intensity distribution 1501_G_A moves outward to the line image intensity distribution 1502_G_A, and the line image intensity distribution 1501_G_B moves inward to become the line image intensity distribution 1502_G_B. It becomes smaller from δG1 to δG2. Further, as shown in FIG. 15B, the line image intensity distribution 1503_G_A moves outward to the line image intensity distribution 1504_G_A, and the line image intensity distribution 1503_G_B moves inward to become the line image intensity distribution 1504_G_B due to the image plane tilt. The amount of deviation increases from δG3 to δG4.

From the above, it can be seen that the amount of center of gravity shift changes according to the image plane tilt, the image height of one decreases, and the image height of the other increases. Since the amount of center of gravity shift is the amount of focus shift due to phase difference AF, it can be said that the amount of focus shift due to phase difference AF changes according to the image plane tilt. Therefore, the information regarding the manufacturing error of the second manufacturing error is stored in advance in the lens memory 118 as the image plane tilt amount (T) of the photographing optical system, and the second manufacturing error correction value (BP2d) is set as the focus detection condition. The amount of image plane tilt (T) corresponding to the above is obtained and calculated according to the equation (9).
BP2d = BP2 × T × α (9)
Here, α is a conversion coefficient for calculating DELTA_BP2 from the image plane tilt amount (T) and BP2. As described above, in step S113, the camera MPU 125 adds BP2d to BP2 using the calculated BP2d to perform the second manufacturing error correction. The camera MPU 125 functions as a second manufacturing error correction means.

In the present embodiment, the information regarding the manufacturing error of the second correction value is held for each state, the manufacturing error correction information according to the focus detection condition is acquired, and the manufacturing error correction value is calculated. However, the manufacturing error correction information may be held only in a specific state, and the state not held may be calculated from the rate of change of the second correction value between the states.

In this way, by separately performing the manufacturing error correction that depends on the color, direction, and spatial frequency of the subject and the manufacturing error correction that depends on the phase difference AF, it is possible to carry out the manufacturing error correction for each factor. Accurate manufacturing error correction is possible. If the manufacturing error correction cannot be performed for each of the first correction value (BP1) and the second correction value (BP2) having different factors, the first correction value (BP1) and the second correction value (BP2) are calculated separately. The same manufacturing error correction can only be performed with phase difference AF and contrast AF. As a result, the accuracy of one of the manufacturing error corrections is lowered.

(Focus detection correction value calculation)
Next, returning to FIG. 6, in step S114 (third calculation step), the camera MPU 125 calculates the focus detection correction value (BP) by the following formula (10).
BP = BP1 + BP2 (10)
In the present embodiment, the focus detection correction value (BP) is divided into a first correction value (BP1) that depends on the color, direction, and spatial frequency of the subject and a second correction value (BP2) that depends on the phase difference AF. To calculate. This makes it possible to correct the amount of focus shift of automatic focus detection in phase difference AF with high accuracy.

Here, FIG. 16 shows a diagram for explaining that the correction can be performed with high accuracy by separately calculating the first correction value (BP1) and the second correction value (BP2). The position P_IMG in FIG. 16 is calculated from the image in-focus position calculated from the image characteristics or evaluation characteristics of the captured image calculated in step S102, and the position P_AF is calculated from the focus detection characteristics of the focus detection means calculated in step S103. Indicates the focus detection focus position. The correction value BP1 is the first correction value calculated in step S104, the correction value BP2 is the second correction value calculated in step S112, and the correction value BP is calculated in step S114. Indicates the focus detection correction value. Further, the difference BP'is a correction value calculated based on the flow of FIG. 6 based on the line image intensity distribution at the position P_IMG without separating the first correction value and the second correction value, and the difference δBP is , Represents the difference (BP'-BP) from the correction value originally desired to be calculated. The horizontal axis shows the set def (actual defocus amount), and the vertical axis shows the detection def (def amount calculated by the automatic focus detection means).

As shown in FIG. 16, when the relationship between the setting def and the detection def is not linear, the correction value is calculated based on the LSF at the imaging focusing position (P_IMG) calculated from the image characteristics or the evaluation characteristics of the captured image. To do. In this case, when the detected image shift amount is converted into the defocus amount, an error δBP occurs due to the non-linearity between the set def and the detected def. On the other hand, when the correction value is calculated based on the LSF at the focus detection focusing position (P_AF) calculated from the focus detection characteristic of the focus detection means, the calculated correction value becomes small, so the setting def And the influence of the error becomes small due to the non-linearity of the detection def.

As described above, according to the present embodiment, the focus detection correction value (BP) is the first correction value (BP1) that depends on the color, direction, and spatial frequency of the subject, and the second correction value (BP2) that depends on the phase difference AF. ) And the calculation. This makes it possible to correct the amount of focus shift of automatic focus detection in phase difference AF with high accuracy.

(Second Embodiment)
Next, the second embodiment will be described. The main difference from the first embodiment is that the phase difference correction information acquired in step S107 is not the line image intensity distribution, but the phase difference focus detection focusing position detected by the phase difference AF and the focus detection characteristic of the focus detection means. This is the difference from the focus detection focusing position calculated from. Further, in the first embodiment, the focus detection correction value is calculated separately for the first correction value and the second correction value. However, in the present embodiment, when calculating P_AF, it is the difference between the phase difference focus detection focus position detected by the phase difference AF and the focus detection focus position calculated from the focus detection characteristic of the focus detection means. 2 Calculated by adding the correction value (BP2).

The automatic focus detection (AF) operation in the digital camera of the present embodiment will be described with reference to FIGS. 5 and 17. The process of FIG. 5 is omitted because it is the same process as that of the first embodiment. Hereinafter, in the first embodiment, the calculation of the focus detection correction value for correcting the result of the automatic focus detection in step S5 of the flow of the entire AF process described with reference to FIG. 5 will be described with reference to FIG. ..

First, in step S1601, the camera MPU 125 acquires aberration information. The aberration information here is information representing the aberration state of the optical system, and is, for example, information regarding the imaging position of the photographing optical system for each of the color, direction, and spatial frequency of the subject. Next, in step S1602, the camera MPU 125 acquires the phase difference correction information. The phase difference correction information is information related to the phase difference focus detection focusing position detected by the phase difference AF. In the present embodiment, the difference between the phase difference focus detection focus position detected by the phase difference AF and the focus detection focus position calculated from the focus detection characteristic of the focus detection means is acquired. In addition, the difference between the phase difference focus detection focus position detected by the phase difference AF and the focus detection focus position calculated from the focus detection characteristics of the focus detection means depends on the change in the photographing optical system and the change in the focus detection optical system. It changes with it. That is, changes in the photographing optical system and changes in the focus detection optical system, such as the position of the focus lens 104 indicating the defocus state, the position of the first lens group 101 indicating the zoom state, and the position coordinates (x1, y1) of the focus detection region. It changes with. Therefore, the difference between the phase difference focus detection focus position detected by the acquired phase difference AF and the focus detection focus position calculated from the focus detection characteristic of the focus detection means is a correction value acquired in step S4 of FIG. Determined based on the calculation conditions.

Next, in step S1603 and step S1604, the camera MPU 125 obtains the imaging focusing position (P_IMG) and the focus detection focusing position (P_AF) from the aberration information acquired in step S1601 and the phase difference correction information acquired in step S1602. Is calculated. That is, the imaging in-focus position (P_IMG) calculated from the image characteristics or the evaluation characteristics of the captured image, and the focus detection in-focus position (P_AF) calculated from the focus detection characteristics of the focus detection means are calculated.

In this embodiment, the case where the following coefficients are set among the coefficients constituting the weighting coefficient used for calculating the in-focus position shown in FIG. 8D in the first embodiment will be described as an example.
K_AF_H = 1
K_AF_V = 0
K_IMG_H = 0.5
K_IMG_V = 0.5
K_IMG_FQ (1) = 1
K_IMG_FQ (2) = 0
K_IMG_FQ (3) = 0
K_IMG_FQ (4) = 0
K_AF_R = 0
K_AF_G = 1
K_AF_B = 0
K_IMG_R = 0.3
K_IMG_G = 0.5
K_IMG_B = 0.2

Further, the information MTF_P_GH of the focus lens 104 position indicating the maximum value of the defocus MTF for each spatial frequency corresponding to the horizontal (H) direction for the green (G) color signal of the formula (1) in the first embodiment is expressed by the formula MTF_P_GH. It is represented by (11).
MTF_P_GH (f, x, y) = (gh (0) x x + gh (1) x y + gh (2)) x f2 + (gh (3) x x + gh (4) x y + gh (5)) x f + (gh (6)) × x + gh (7) × y + gh (8)) (11)

First, in the present embodiment, twice the second correction value (BP2) is added to the gh (8) term of the equation (10) corresponding to the horizontal (H) direction for the green (G) color signal. That is, twice the second correction value (BP2), which is the difference between the phase difference focus detection focus position detected by the phase difference AF and the focus detection focus position calculated from the focus detection characteristic of the focus detection means, is added. .. In order to distinguish MTF_P_GH (f, x, y) after addition from that before addition, it is expressed as MTF_P_GH_BP2 (f, x, y). The equation (11) after addition is shown in equation (12).
MTF_P_GH_BP2 (f, x, y) = (gh (0) x x + gh (1) x y + gh (2)) x f2 + (gh (3) x x + gh (4) x y + gh (5)) x f + (gh (6)) × x + gh (7) × y + (gh (8) + BP2 × 2)) (12)

The equation (12) shows the equation of the information MTF_P_GH_BP2 of the focus lens 104 position indicating the maximum value of the defocus MTF for each spatial frequency corresponding to the horizontal (H) direction for the green (G) color signal. The same applies to the horizontal (H) direction of the red (R) color and blue (B) color signals. The vertical (V) direction of the red (R) color, green (G) color, and blue (B) color signals is the same as in the formula (1) of the first embodiment.

Further, in the present embodiment, the camera MPU 125 acquires gh (8) and BP2, and the second correction value (BP2) is calculated twice by the equation (12). However, the camera MPU 125 may acquire gh (8) + BP2 × 2 obtained by adding twice the second correction value (BP2) in advance with the lens MPU117. By doing so, it is possible to reduce the communication between the lens MPU 117 and the camera MPU 125.

Further, in the lens memory 118 of the lens unit 100, gh (8) + BP2 × 2 is stored in advance as gh (8) _BP2 instead of gh (8), and the camera MPU 125 requests the lens MPU 117 to perform gh (8). 8) _BP2 may be acquired. Note that gh (8) _BP2 may be stored in the non-volatile region of the camera RAM 125b. In this case, the storage capacity of the lens memory 118 or the camera RAM 125b can be reduced.

Next, the position information (x1, y1) of the focus detection region is substituted into x and y of the equation (12). By this calculation, the equation (12) is expressed in the form of the following equation (13).
MTF_P_GH_BP2 (f) = Agh x f2 + Bgh x f + Cgh + BP x 2
= MTF_P_GH (f) + BP x 2 (13)
Agh, Bgh, and Cgh represent the same coefficients as in the first embodiment. Here, the camera MPU 125 also calculates MTF_P_RH_BP2 (f) and MTF_P_BH_BP2 (f) in the same manner.

Next, the camera MPU 125 is a coefficient (FIG. 8 (D)) that constitutes a weighting coefficient used for calculating the focusing position of the correction value calculation condition acquired in step S4 of FIG. 5 of the first embodiment. Weight the aberration information. However, the above-mentioned values are used for K_AF_H, K_AF_V, K_IMG_H, K_IMG_V, K_IMG_FQ (1), K_IMG_FQ (2), K_IMG_FQ (3), and K_IMG_FQ (4).

Specifically, the equation (13) and the above-mentioned coefficients are substituted into the equations (3) and (4) of the first embodiment. When substituting and rearranging, equations (14) and (15) are obtained.
MTF_P_AF_BP2 (f) = MTF_P_GH (f) + BP2 × 2 (14)
MTF_P_IMG_BP2 (f) =
0.15 × MTF_P_RH (f)
+0.15 × MTF_P_RV (f)
+0.25 × MTF_P_GH (f)
+0.25 MTF_P_GV (f)
+0.25 × MTF_P_BH (f)
+0.25 × MTF_P_BV (f)
+ BP2 (15)

Further, when the above-mentioned coefficients are substituted into the equations (3) and (4) of the first embodiment and arranged, the equations (16) and (17) are obtained.
MTF_P_AF (f) = MTF_P_GH (f) (16)
MTF_P_IMG =
0.15 × MTF_P_RH (f)
+015 × MTF_P_RV (f)
+0.25 × MTF_P_GH (f)
+0.25 MTF_P_GV (f)
+0.25 × MTF_P_BH (f)
+0.25 × MTF_P_BV (f) (17)

When the equations (14) and (15) are rearranged using the equations (16) and (17), the equations (18) and (19) are obtained.
MTF_P_AF_BP2 (f) = MTF_P_AF (f) + BP2 × 2 (18)
MTF_P_IMG_BP2 (f) = MTF_P_IMG (f) + BP2 (19)

Next, the camera MPU 125 sets the imaging focusing position (P_IMG) and the focus detection focusing position (P_AF) in consideration of the second correction value (BP2) depending on the phase difference AF by the following equations (20) and (21). ). That is, the focus detection focus position (P_IMG) calculated from the image characteristics or evaluation characteristics of the captured image in consideration of the second correction value (BP2) and the focus detection focus position (P_AF) calculated from the focus detection characteristics of the focus detection means. ) Is calculated according to the following equations (20) and (21).

The focus detection focus position is calculated by weighting and adding the maximum value information of the defocus MTF for each spatial frequency obtained by the equations (14) and (15) and the photographed image and the AF evaluation band obtained in step S4. To do. That is, the maximum value information MTF_P_AF_BP2 (f) and MTF_P_IMG_BP2 (f) of the defocus MTF for each spatial frequency are weighted and added by the captured image obtained in step S4 and the AF evaluation bands K_IMG_FQ (n) and K_AF_FQ (n). .. However, in this embodiment, the calculation is performed using the above-mentioned K_IMG_FQ (1), K_IMG_FQ (2), K_IMG_FQ (3), and K_IMG_FQ (4).
P_IMG_BP2 = MTF_P_IMG_BP2 (1)
= MTF_P_IMG (1) + BP2 (20)
P_AF_BP2 = MTF_P_AF_BP2 (1)
= MTF_P_AF (1) + BP2 × 2 (21)

Next, in step S1605, the camera MPU 125 calculates the focus detection correction value (BP) by the following equation (22).
BP = P_AF_BP2-P_IMG_BP2
= MTF_P_AF (1) -MTF_P_IMG (1) + BP2
= BP1 + BP2 (22)

As described above, the first correction value (BP1) and the second correction value (BP1) are calculated by adding twice the second correction value (BP2) to the gh (8) term of the equation (11). The focus detection correction value (BP) including BP2) can be calculated. As described above, according to the present embodiment, the focus detection error of the phase difference AF due to the aberration of the optical system is corrected by separately correcting the correction depending on the color, direction, and spatial frequency of the subject and the correction depending on the phase difference AF. Can be provided with a focus detection method capable of accurately correcting.

Moreover, although the preferred embodiment of the present invention has been described, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

Claims (8)

An imaging means having a plurality of pixels capable of photoelectrically converting a light flux passing through different pupil regions of an imaging optical system and outputting a pair of photoelectric conversion signals.
An acquisition means for acquiring aberration information of the photographing optical system, and
From the acquired aberration information, the first correction value is calculated from the imaging in-focus position calculated from the image characteristic or the evaluation characteristic of the image and the focus detection in-focus position calculated from the focus detection characteristic of the focus detection means.
A correction value corresponding to the gravity center displacement amount difference caused by the shape of the pair of line image intensity distributions are different from each other, the imaging optical system corresponding to the pair of photoelectric conversion units of the image pickup means in the focus detecting focus position and based on the line image intensity distribution by calculating a second correction value from the phase difference focus detection in-focus position detected by the phase difference focus detection method,
A calculation means for calculating the focus detection correction value from the first correction value and the second correction value, and
A focus detector characterized by having. The first correction value is the difference between the imaging focus position and the focus detection focus position, and the second correction value is the difference between the focus detection focus position and the phase difference focus detection focus position. The focus detection device according to claim 1, wherein the focus detection device is characterized by the above. According to claim 1 or 2, the phase difference focus detection focusing position is calculated based on the amount of misalignment of the line image intensity distribution of the photographing optical system detected by the phase difference focus detection method. The focus detector of the description. Any one of claims 1 to 3, wherein the calculation means calculates the focus detection correction value using only the first correction value when the phase difference focus detection method is not used. The focus detector according to. The calculating means, when the difference between the phase difference focus detection focus position and the focus detection focus position is small, by using only the first correction value to calculate the focus detection correction value, the difference is not smaller The focus detection device according to any one of claims 1 to 4, wherein the focus detection correction value is calculated from the first correction value and the second correction value. The focus detection device according to any one of claims 1 to 5, wherein the aberration information of the photographing optical system is information regarding the imaging position of the photographing optical system for each of a plurality of different spatial frequencies. The focus detection device according to any one of claims 1 to 6.
A control means for controlling the position of the focus lens of the photographing optical system based on the result of the focus detection corrected by the focus detection correction value, and
An imaging device characterized by comprising. A focus detection method of a focus detection device having an imaging means having a plurality of pixels capable of photoelectrically converting a light flux passing through different pupil regions of an imaging optical system and outputting a pair of photoelectric conversion signals.
The first correction value is calculated from the imaging in-focus position calculated from the image characteristics or evaluation characteristics of the image from the aberration information of the photographing optical system and the focus detection in-focus position calculated from the focus detection characteristics of the focus detection means. 1 calculation process and
The imaging optical system corresponding to the pair of photoelectric conversion units of the imaging means at the focus detection focusing position, which is a correction value corresponding to the difference in the amount of center of gravity shift caused by the shapes of the pair of line image intensity distributions being different from each other. The second calculation step of calculating the second correction value from the phase difference focus detection focusing position detected by the phase difference focus detection method based on the line image intensity distribution of
A third calculation step of calculating the focus detection correction value from the first correction value and the second correction value, and
A focus detection method characterized by having.

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