JP2014194502A - Imaging apparatus and imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relatively easily attain high focus accuracy when providing a focus detection pixel on an imaging plane of an imaging device, and performing a focus detection by a phase difference system.SOLUTION: An imaging apparatus includes: an imaging device 132 that has a focus detection pixel for detecting a focus by a phase difference system, and photoelectrically converts an optical image to be formed by an imaging optical system; and a camera CPU 151 that moves the imaging optical system in an optical axis direction on the basis of a detection result by the focus detection pixel of the imaging device to perform focus adjustment. The camera CPU 151 computes a correction amount ΔZ, using information about light reception intensity distribution characteristics and information about defocus correction distribution, and moves the imaging optical system on the basis of the correction amount to correct an optimal focus position.

Description

  The present invention relates to an imaging apparatus and an imaging system.

  In a single-lens reflex camera system, it is known that a light beam that has passed through an imaging optical system is reflected by a sub-mirror and guided to a focus detection unit, and this is used to perform focus detection by a phase difference method in the focus detection unit. In addition, the best focus (best focus: BP) correction for correcting the deviation between the in-focus position on the image pickup surface of the image pickup element by the photographing optical system and the in-focus position on the light receiving surface of the light receiving sensor by the optical system of the focus detection unit is also provided. Are known. In the automatic focus adjustment (AF) in this case, for example, the focus lens is further driven by the BP correction amount after the focus lens is driven to the in-focus range based on the detection result of the focus detection unit.

  On the other hand, in live view shooting, in which shooting is performed while observing a subject image formed on an image sensor in real time, Patent Document 1 performs focus detection using a phase difference method by providing focus detection pixels on the image pickup surface of the image sensor. Proposed method.

JP 2004-191629 A

  When focus detection pixels are provided on the imaging surface of the image sensor to perform phase difference focus detection, BP correction is necessary because the focus detection pixels and imaging pixels have different imaging characteristics. In this case, the BP correction value is the pupil plane caused by the light reception sensitivity distribution characteristic of the focus detection pixel depending on the specification and position of the image sensor, the aberration information of the pupil plane unique to the photographing optical system, the F value, and the manufacturing error of the photographing optical system. It fluctuates depending on many parameters such as aberration information. The specification of the image sensor includes the structure and arrangement of focus detection pixels, and the position of the image sensor includes the distance in the optical axis direction from the interchangeable lens mounting position of the camera body to the image sensor. If a BP correction value considering all parameters is prepared and stored in the lens unit in advance, the amount of data becomes enormous, which is not realistic. On the other hand, if an appropriate BP correction value is not used, the focusing accuracy decreases.

  The present invention provides an image pickup apparatus and an image pickup system capable of relatively easily obtaining high focusing accuracy when a focus detection pixel is provided on an image pickup surface of an image pickup element and phase difference type focus detection is performed. For exemplary purposes.

  An imaging apparatus according to the present invention includes a focus detection pixel for performing phase difference focus detection, an image sensor that photoelectrically converts an optical image formed by a photographing optical system, and the focus detection pixel of the image sensor. Control means for adjusting the focus by moving the photographic optical system in the direction of the optical axis based on the detection result of the focus detection, and the control means detects the focus with respect to the light incident angle of the focus detection pixel. The correction amount is calculated using information on the received light intensity distribution characteristic indicating the output signal intensity from the pixel for use and information on the defocus correction distribution indicating the distribution of the defocus correction amount caused by the aberration characteristic of the photographing optical system. The best focus position is corrected by calculating and moving the photographing optical system in the optical axis direction based on the calculated correction amount.

  According to the present invention, it is possible to provide an imaging apparatus and an imaging system that can relatively easily obtain a high focusing accuracy when a focus detection pixel is provided on an imaging surface of an imaging element to perform phase difference type focus detection. can do.

It is a block diagram of the camera system of this embodiment. FIG. 2 is a schematic enlarged plan view showing a pixel array applicable to the image sensor shown in FIG. 1. It is a figure which shows the light imaged on the image pick-up element shown in FIG. It is a graph for demonstrating the principle of a focus detection of a phase difference system. It is a figure which shows the light reception intensity distribution characteristic information of the focus detection pixel and imaging pixel shown to Fig.2 (a). It is a figure which shows the light reception intensity distribution characteristic information of the pixel for focus detection shown in FIG.2 (b), and the pixel for imaging. It is a figure which shows the light reception intensity distribution characteristic information of the pixel for focus detection shown in FIG.2 (c), and the pixel for imaging. It is a graph for demonstrating the method of calculating BP correction value. It is a graph for demonstrating the method of calculating BP correction value. 4 is a flowchart for explaining an automatic focus adjustment operation by the camera CPU shown in FIG. 1.

  FIG. 1 is a block diagram of the camera system (imaging system) of this embodiment. The camera system includes a lens unit (interchangeable lens) 101 and a camera unit (camera body) 121 to which the lens unit 101 is detachably attached. The camera unit 121 of the present embodiment is a single-lens reflex camera, but may be configured as a mirrorless camera. The camera system may be a lens-integrated camera. The camera unit 121 includes a digital still camera, a digital video camera, and the like, and can capture moving images and still images.

  The lens unit 101 is detachably attached to an arbitrary imaging device, and houses a photographing optical system that forms an optical image of a subject (object). The photographing optical system includes, as an example, a first lens group 102, a diaphragm 103, a second lens group 104, and a third lens group 105.

  The first lens group 102 is disposed on the most object side of the photographing optical system. The aperture 103 adjusts the aperture diameter to adjust the amount of light during shooting, and also functions as an exposure time adjustment shutter during still image shooting. The third lens group 105 is a focus lens group for performing focus adjustment by movement in the optical axis direction. A zoom function that changes the focal length by changing the air gap from the first lens group 102 to the third lens group 105 is realized. Note that the configuration of the photographing optical system is exemplary, and may include other lenses such as an anti-vibration lens. In FIG. 1, each lens group is shown as a single lens, but in actuality, it is composed of one or a plurality of lenses.

  Reference numeral 106 denotes a zoom actuator that drives the first lens group 102 to the third lens group 105 in the optical axis direction to perform a zoom operation. Reference numeral 107 denotes an aperture actuator that adjusts the amount of light by changing the aperture diameter of the aperture 103 and controls the exposure time during still image shooting with the role of a shutter depending on the type of camera system. Reference numeral 108 denotes a focus actuator, which adjusts the focus by driving the third lens group 105 in the optical axis direction. Reference numeral 109 denotes a memory (second memory) that stores defocus correction distribution information unique to the optical characteristics of the photographing optical system. The defocus correction distribution information is numerical information for performing the best focus (best focus: BP) correction, and represents the distribution of the defocus correction amount caused by the aberration characteristics of the photographing optical system.

  As the aberration of the photographing optical system, an aberration value due to a manufacturing error may be added in addition to the inherent aberration value. Even if the defocus correction amount distribution information based on the inherent aberration value and the defocus correction distribution information based on the manufacturing error are separately provided, processing such as selection and addition may be performed as necessary with each other's information and individual information. Good.

  Reference numeral 110 denotes a lens CPU (lens control means) that controls the operation of each part of the lens unit 101 and communicates with the camera CPU 151 of the camera unit 121. The lens CPU 110 transmits information according to a request from the camera unit 121 (for example, defocus correction distribution information), or performs an auxiliary calculation and transmits a calculation result.

  The camera unit 121 functions as an imaging device. A reflecting member (main mirror) 122 reflects a part of the light beam that has passed through the photographing optical system to the finder unit 123 that is disposed above the reflecting member 122. The reflection member 122 may be a quick return type reflection member like a general single-lens reflex camera, or may be a semi-transmission type and a fixed type. The reflective member 122 is partially formed with a semi-transmissive region. A sub-reflecting member (sub-mirror) 124 deflects the light beam that has passed through the reflecting member 122.

  Reference numeral 125 denotes a focus detection unit that performs focus detection by the phase difference method from the light beam reflected by the sub-reflection member 124. The phase difference type focus detection means that focus detection is performed by detecting a phase difference between image signals of a pair of subject images. The optical elements 122 to 125 may be omitted when the subject image confirmation is performed using a live view or an external viewfinder.

  Reference numeral 131 denotes an optical low-pass filter that reduces false colors and moire in the captured image.

  Reference numeral 132 denotes an image sensor composed of a C-MOS sensor and its peripheral circuits. The imaging element 132 includes imaging pixels and focus detection pixels. The imaging pixels photoelectrically convert the optical image of the subject formed by the imaging optical system. The focus detection pixel performs focus detection by a phase difference method. Thereby, focus detection can be performed in a short time in live view shooting. Note that the focus detection pixels may function as imaging pixels.

  The image sensor 132 uses a two-dimensional single-plate color sensor in which M pixels in the horizontal direction and N pixels in the vertical direction are squarely arranged, and a Bayer array primary color mosaic filter is formed on-chip. . A phase difference is obtained by arranging a pair of focus detection pixel columns in the pixel column and correlating the photoelectric conversion signals of the pixel columns.

  141 is a wireless communication means, which is composed of an antenna and a signal processing circuit for communicating with a server through a network such as the Internet. The camera unit 121 includes a USB port connected to a personal computer (PC) or the like, and may be connected to a network via the PC.

  The camera CPU (camera control means) 151 includes a calculation unit, a ROM, a RAM, an A / D converter, a D / A converter, a communication interface circuit, and the like in order to control various controls of the camera body. The camera CPU 151 drives various circuits included in the camera based on a program stored in the ROM, and executes a series of operations such as focus detection, photographing, image processing and recording, which will be described later. For example, at least a part of the automatic focus adjustment (AF) method shown in FIG. 10 to be described later may be stored in the ROM as a program.

  A communication control circuit 152 transmits a captured image from the camera to the server and receives images and various information from the server via the communication unit 141. The camera CPU 151 receives received light intensity distribution characteristic information and defocus correction distribution information from a server on the network via the communication control circuit 152 and wireless communication means 141 (or other means such as a USB port and a USB cable). May be obtained.

  A focus detection circuit 154 transmits focus detection information from the focus detection unit 125 to the camera CPU 151.

  Reference numeral 155 denotes a defocus correction distribution information input circuit, which acquires defocus correction distribution information stored in the memory 109 of the lens unit 101 and transmits it to the camera CPU 151. Thereby, the camera CPU 151 calculates in-focus position correction information for correcting the best in-focus position that changes due to the influence of the optical aberration of the photographing optical system.

  Reference numeral 156 denotes a memory (first memory) for storing the received light intensity distribution characteristic information. The memory 156 stores the received light intensity distribution characteristic information at the time of shipment. However, as described above, it is downloaded from a network or the like and stored. May be.

  The received light intensity distribution characteristic information is output signal intensity information with respect to a light incident angle to the focus detection pixel and the imaging pixel of the imaging element 132. For example, the intensity of the signal output from the focus detection pixel when the light beam is vertically incident on the focus detection pixel, and the output from the focus detection pixel when the light beam is incident on the focus detection pixel at an incident angle of 45 ° The strength of the signal to be generated is different. The received light intensity distribution characteristic may be normalized by the intensity of the output signal from the pixel when a light beam from a specific incident angle or a specific coordinate on the pupil surface enters the pixel. As will be described later, it is assumed that the memory 156 stores F-number conversion of the photographing optical system and baseline length information corresponding to the received light intensity distribution characteristics together.

  In the present embodiment, automatic focus adjustment (AF) is performed from the focus detection result obtained via the focus detection unit 125 and the focus detection circuit 154, and AF is performed from the focus detection result by the focus detection pixels of the image sensor 132. However, the former AF is not essential.

  Reference numeral 161 denotes a focus lens drive circuit, which drives and controls the focus actuator 162 based on the focus detection result. Reference numeral 162 denotes an aperture driving circuit that controls the aperture actuator 112 to adjust the aperture diameter of the aperture 103. Reference numeral 164 denotes a zoom drive circuit that drives the zoom actuator 106 in accordance with the zoom operation of the photographer. Note that the zoom actuator 106 and the zoom drive circuit 164 may be omitted when the zoom drive is manual.

  An image processing circuit 171 performs processing such as γ conversion, color interpolation, and image compression of the image acquired by the image sensor 132. Reference numeral 172 denotes a display such as an LCD, which displays information related to the shooting mode of the camera, a preview image at the time of shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, camera posture information, and the like. Reference numeral 173 denotes an operation switch group, which includes a power switch, a shooting start switch, a zoom operation switch, a shooting mode selection switch, and the like. Reference numeral 174 denotes a detachable flash memory that records a photographed image.

  The focus detection unit 125 is provided with a pair of focus detection optical systems. Each optical system captures a part of the exit pupil range of the photographing optical system, forms an image on a pair of light receiving sensors, and correlates the signals photoelectrically converted by the light receiving sensors, thereby obtaining two object images. Detect phase difference. The relationship of the following equation is established among the defocus correction amount (image position displacement amount) DEF, the phase difference (image displacement amount) L, and the base line length K.

K = L / DEF (1)
The calculation of the baseline length requires the optical characteristics and electrical characteristics of the imaging optical system and focus detection pixels. Specifically, the relationship between ray vignetting information for deriving the exit pupil shape of the imaging optical system and the pupil image of the focus detection pixel projected at that position, and the light reception when the focus detection pixel receives light from the exit pupil. Intensity distribution information is required.

  The optical system of the focus detection unit 125 arranges a light-shielding mask to separate the light passage range (pupil separation) of the photographing optical system, and the focus of the photographing optical system prevents the light rays in the light-shielding range from causing vignetting. The brightness (effective F value) above a certain level is maintained in the open state. Since the baseline length information does not change, it is sufficient for the imaging apparatus to store baseline length information unique to the focus detection optical system.

  However, when the phase difference type focus detection is performed by the image sensor of the image sensor 132, the F value fluctuates. Therefore, there arises a problem that the defocus correction amount due to the baseline length information, the aberration inherent in the photographing optical system, and the manufacturing error varies depending on the F value and the received light intensity distribution characteristic.

  Hereinafter, a pixel array applicable to the image sensor 132 will be described with reference to FIG.

  FIG. 2A shows an example of a pixel array on the imaging surface of an imaging device in which one photoelectric conversion unit is arranged in one microlens. The vertical direction is the Y direction, and the horizontal direction is the X direction, which is the same in FIGS. 2B and 2C. Pixels are arranged in a matrix in the XY direction. Reference numeral 200 denotes an imaging pixel, and 201 to 204 denote focus detection pixels. The circle outline of each pixel represents a microlens, and the internal square represents a photoelectric conversion unit. When the imaging pixel 200 is white, it indicates that it is not shielded from light, and when the focus detection pixel is partially black, it indicates that the part is shielded from light.

  A pixel group 201 having a left opening and a pixel group 202 having a right opening arranged in a line in the Y direction generate a subject image in the Y direction. These pixel groups are used as a pair of focus detection pixel rows, and a pair of signals output therefrom are subjected to correlation calculation to detect the focus of a subject having a horizontal stripe pattern shape. Similarly, a pixel group 203 having an upper opening and a pixel group 204 having a lower opening arranged in a line in the X direction generate a subject image in the X direction. These pixel groups are used as a pair of focus detection pixel arrays, and a pair of signals output therefrom are subjected to correlation calculation to detect the focus of a subject having a vertical stripe pattern shape.

  FIG. 2B shows an example of a pixel array on the imaging surface of an imaging device in which two photoelectric conversion units are arranged in one microlens. Pixels are arranged in a matrix in the XY direction, a circle outside each pixel represents a microlens, and two substantially semicircles inside the pixel represent photoelectric conversion elements.

  The photoelectric conversion units 302 and 303 of the pixel group 301 aligned in the X direction are used as a pair of focus detection pixels, and a pair of signals output from the photoelectric conversion units 302 and 303 are subjected to correlation calculation to detect the focus of the subject in the stripe pattern in the Y direction. In addition, the photoelectric conversion units 304 and 305 of the pixel group 300 arranged in the Y direction are used as a pair of focus detection pixels, and a pair of signals output from the photoelectric conversion units 304 and 305 are subjected to correlation calculation to detect the focus of the subject in the X direction stripe pattern. Do. Imaging signals are acquired by adding the electrical signals of the photoelectric conversion units 302 and 303 and the electrical signals of the photoelectric conversion units 304 and 305, respectively.

  FIG. 2C shows an example of a pixel array on the imaging surface of an imaging device in which four photoelectric conversion units are arranged in one microlens. By changing the electric signal addition method of the four photoelectric conversion units, the same result as in FIG. 2B is obtained. Pixels are arranged in a matrix in the XY direction, a circle outside each pixel represents a microlens, and four squares inside each represent a photoelectric conversion element.

  The output signals of the photoelectric conversion units 401 and 402 and the photoelectric conversion units 403 and 404 of the pixel group 400 arranged in the X direction are added together, and the obtained two electric signal waveforms are subjected to a pair of correlation calculation, thereby causing stripes in the Y direction. The focus detection of the subject of the pattern is performed. Further, the output signals of the photoelectric conversion units 401 and 403 and the photoelectric conversion units 402 and 404 of the pixel group 400 arranged in the Y direction are added, and the obtained two electric signal waveforms are subjected to a pair of correlation operations to thereby calculate the X direction. The focus detection of the subject of the stripe pattern is performed.

  Note that the addition method may be changed by dividing the image sensor into blocks, and by changing the addition alternately in a staggered arrangement, a pixel arrangement equivalent to that in FIG. 2B can be achieved. Since the vertical stripe pattern and the horizontal stripe pattern can be evaluated simultaneously, the direction dependency of the subject pattern can be eliminated. In addition, the addition method may be switched for all pixels in accordance with the shooting state or in time series. At this time, since the focus detection pixels for detecting the focus of the subject in the same pattern direction are in a dense state, a subject having a thin line segment generated when the focus detection pixels are sparse cannot perform subject detection near the in-focus state. The problem can be avoided. What is necessary is just to add the electrical signal of the photoelectric conversion parts 402-405 to the signal for imaging | photography.

  FIG. 3A is a cross-sectional view illustrating the relationship between the imaging optical system BL and the focus detection pixels of the image sensor IP, and the optical axis is indicated by a one-dot chain line. FIG. 3A is an example, and the position of the diaphragm and the shape of the lens are not the same as those in FIG. 1, but may be the same.

  AS is a focus detection pixel. EPO is a virtual surface that is disposed between the imaging surface of the imaging element IP and the stop of the imaging optical system BL and is a plane perpendicular to the optical axis of the imaging optical system BL (parallel to the imaging surface). The virtual plane EPO may be an entrance pupil plane of the photographing optical system BL. FIG. 3A shows a state in which the light beam D enters the focus detection pixel AS after passing through the light beam passage range PD of the virtual surface EPO via the photographing optical system BL. Although not shown in FIG. 3A, the pair of focus detection pixel groups described in FIG. 2 exist.

  FIGS. 3B and 3C show pupil projection images of the focus detection pixels with respect to the exit pupil of the imaging optical system BL, and the light flux range incident on the focus detection pixels of the image sensor from the virtual plane EP0. Is shown. FIG. 3B corresponds to the case where the focus detection pixel shown in FIG. 2A is used, and FIG. 3C shows the focus detection pixel shown in FIG. 2B or 2C. Corresponds to the use of.

  In FIG. 3B, reference numerals 600 and 604 denote a pair of focus detection pixels, reference numeral 601 denotes a microlens, reference numeral 602 denotes a light shielding member, and reference numeral 603 denotes a photoelectric conversion unit. EPa0 indicates a light beam range incident on the focus detection pixel 600 on the virtual plane EP0, and EPb0 indicates a light beam range incident on the focus detection pixel 604 on the virtual plane EP0.

  A pixel 700 in FIG. 3C includes a plurality of photoelectric conversion units 702 and 703 that receive light through one microlens 701. The photoelectric conversion units 702 and 703 receive light beams that have passed through an effective range outside the optical axis of the microlens 701, and each receive light beams in different regions of the exit pupil of the photographing optical system BL. EPa0 indicates a light beam range incident on the photoelectric conversion unit 702 on the virtual plane EP0, and EPb0 indicates a light beam range incident on the photoelectric conversion unit 703 on the virtual plane EP0.

  When FIG. 2C is applied, the photoelectric conversion units 702 and 703 correspond to the photoelectric conversion units 403 and 404, and the photoelectric conversion units 401 and 402 are perpendicular to the paper surface of the photoelectric conversion units 702 and 703. Arranged in the depth direction.

  FIG. 4 shows signal waveforms AIO and BIO of a pair of subject images (A image and B image) obtained from the focus detection pixels in the phase difference type focus detection. The horizontal axis X represents pixel arrangement coordinates, and the vertical axis represents photoelectric conversion signal intensity. The signal waveform is interpolated. The phase difference L is the correlation distance (image shift amount), and the defocus correction amount is calculated from Equation 1.

  5 shows the light reception intensity distribution characteristic information of the focus detection pixel shown in FIG. 2A, FIG. 6 shows the light reception intensity distribution characteristic information of the focus detection pixel shown in FIG. These show the received light intensity distribution characteristic information of the focus detection pixels shown in FIG.

  In this case, the “light reception intensity distribution characteristic” refers to a light beam that passes through each region and enters the focus detection pixel when the light beam passage range PD of the virtual plane EPO is divided into a plurality of regions with the optical axis as the origin. The light receiving sensitivity ratio (photoelectric conversion signal intensity ratio) of the pixel with respect to the incident angle to the focus detection pixel. 5 to 7, the XY coordinates are set on the virtual plane EPO, and each axis is orthogonal to the optical axis. LA and LB indicate received light intensity distribution characteristics of the A image and B image focus detection pixels. (A) and (b) are three-dimensional intensity graphs showing the normalized output signal intensity with respect to the position of the XY coordinates. (C) shows a graph of the central section in the depth direction (Y coordinate), L0 shows the received light intensity distribution characteristics of the imaging pixels, the horizontal axis is the X coordinate (Y coordinate is 0), and the vertical axis is normalized. Output signal strength.

  FIG. 5 has such a characteristic that a part of the received light intensity distribution characteristic of the imaging pixel is cut out by the slit-shaped light shielding member 602 shown in FIG. As shown in FIG. 3C, FIG. 6 has a plurality of photoelectric conversion units in one imaging pixel, and LA and LB are equivalent to the photoelectric conversion intensity obtained by combining a part or a plurality of photoelectric conversion units. For this reason, the light reception intensity distribution characteristic obtained by adding LA and LB is equivalent to the light reception intensity distribution characteristic L0 of the imaging pixel. FIG. 7 shows a case where an asymmetric property is generated in the received light intensity distribution characteristics of LA and LB because the microlens in FIG. 6 is decentered in the X direction in the manufacturing process. Also, baseline length information corresponding to the F value of the photographing optical system is stored in the memory 156 in advance from the pupil-divided received light intensity distribution characteristics LA and LB.

  Table 1 shows the output signal intensity from the focus detection pixel with respect to the incident angle of the light beam that passes through each region and enters the focus detection pixel when the light beam passage range PD of the virtual plane EPO is divided into a plurality of regions. It represents information of the received light intensity distribution characteristic and corresponds to FIG. The left side of FIG. 8A is a graph of the X cross section at Y = 0 in Table 1, and the right side of FIG.

  Table 2 shows defocus correction distribution information, which is a normalized distribution of the shift (defocus correction amount) of the best in-focus position caused by the aberration of the photographing optical system BL in each region of the virtual surface EPO. Corresponds to (b). The left side of FIG. 8B is a graph of the X cross section at Y = 0 in Table 2, and the right side of FIG.

  Table 3 is information obtained by multiplying numerical values at the same coordinates in Table 1 and Table 2. In Table 3, the area outside the light beam effective range is left blank for easy understanding, but 0 may be entered in the blank. Table 3 corresponds to FIG. The left side of FIG. 8C is a graph of the X section at Y = 0 in Table 3, and the right side of FIG.

  Using Table 3, the best focus correction position is calculated. If X and Y are square arrays of n × n divisions, the numerical values in the i and j-th region coordinates in the X and Y directions in Table 3 are C (Xi, Yj), and the numerical values of each region of the light passage range PD. Is integrated and the total number of regions of the light passing range PD is set to N, the focus position correction amount is expressed by the following equation.

  That is, the product of the received light intensity distribution characteristic value and the defocus correction distribution value is calculated for each region of the virtual plane EPO, and the calculation result of each region is integrated and divided by the total number N of regions to obtain the focus position correction amount. calculate.

  Even if the combination of the lens unit 101 and the camera unit 121 changes, if each unit has the received light intensity distribution characteristic information and the focus position correction information, the BP correction can be easily performed. Specifically, information on the received light intensity distribution characteristics of the pixels of the image sensor is stored in the memory 156 of the camera unit 121, and information on the defocus correction distribution is stored in the memory 109 of the lens unit 101. In the present embodiment, the camera CPU 151 obtains information on the received light intensity distribution characteristics from the memory 156, obtains information on the defocus correction distribution from the defocus correction distribution information input circuit, and calculates Table 3 and Equation 2. The camera CPU 151 may acquire the calculation result from the lens CPU 110 by transmitting the received light intensity distribution characteristic information to the lens CPU 110 and causing the lens CPU 110 to perform the calculations of Table 3 and Formula 2.

  In this embodiment, Table 3 is acquired by the product of the numerical values of Table 1 and Table 2, but either numerical value may be weighted, or Table 3 is acquired by the weighted average of the numerical values of Table 1 and Table 2. May be. Also, the integration of Equation 2 may be weighted.

  As described above, in the focus detection by the focus detection unit 125, the F value is set to an effective F value. However, when focus detection is performed on the imaging surface of the image sensor, the F value (or aperture value) is changed. Is done. For this reason, in this embodiment, the camera CPU 151 acquires F value information from the operation switch 173 and the like, and selects a defocus correction distribution of an effective region on which a light ray enters based on the information. Specifically, a part of Table 2 is selected according to the F value. Then, the calculation of Table 3 and Formula 2 is performed on the selected defocus correction distribution.

  In this way, if the camera unit and the lens unit have the received light intensity distribution characteristic information and the focus position correction information, the focus position correction amount can be obtained. Therefore, the number of combinations of all camera units and lens units can be obtained. It is no longer necessary to have this information.

  FIG. 9 is the same as FIG. 8 but shows an example in the case where there are manufacturing errors between the image sensor and the photographing optical system. Tables 4, 5, and 6 correspond to FIGS. 9A, 9B, and 9C, respectively. For example, when decentration of the microlens of the image sensor or optical decentration of the photographing optical system occurs in the manufacturing process, in FIG. 9, the received light intensity distribution characteristic and the defocus correction distribution are acquired using measurement or simulation.

  Compared to FIG. 8, the received light intensity distribution characteristics and the defocus correction distribution of FIG. 9 are offset in the X direction, and Table 6 also changes from Table 3. For this reason, the focus position correction amount obtained from Expression 2 is different from that in FIG. Thus, BP correction can be performed even if a manufacturing error that affects the in-focus position occurs in the image sensor or the imaging optical system.

  FIG. 10 is a flowchart showing the AF operation of the camera CPU 151, and “S” represents a step. Here, the case where the focus detection operation is performed using the focus detection pixels on the imaging surface of the image sensor during live view is shown. At least a part of the flowchart shown in FIG. 10 can be embodied as a program for causing a computer to execute the function of each step.

  When the photographer turns on the power switch of the camera, the camera CPU 151 confirms the operation of each actuator and image sensor 132 in the camera, initializes the memory contents and the execution program, and executes the shooting preparation operation.

  When the photographer operates the shutter button or the like, the photographing operation is started, and the camera CPU 151 acquires information on the zoom position, focus position, and F value of the photographing optical system (S100). Next, a focus detection range on the pixel is selected arbitrarily or automatically, and the camera CPU 151 acquires the information (S101).

  Next, the camera CPU 151 acquires an output signal (for example, one shown in FIG. 4) of a target focus detection pixel based on the information on the optical system and the information on the focus detection range acquired in S100 and S101. (S102).

  Next, the camera CPU 151 performs a correlation operation on the output signals obtained in S102 to obtain the phase difference L (S103). Next, the camera CPU 151 acquires baseline length information corresponding to the F value from the phase difference L acquired in S103 and the F value acquired in S100 from the memory 156, and calculates the defocus amount DEF from Equation 1 (S104). .

  Next, the camera CPU 151 determines whether or not focusing can be considered from the defocus amount obtained in S104 (S105). If the camera CPU 151 determines that it is not in focus (No in S105), it issues a command to drive the third lens group 105 based on the defocus amount calculated in S104 via the focus drive circuit 161. 101 is transmitted (S106), and the process returns to S100.

  On the other hand, if the camera CPU 151 determines that it is in focus (Yes in S105), it performs BP correction. That is, the camera CPU 151 acquires the received light intensity distribution characteristic information from the memory 156, and acquires the defocus correction distribution information from the defocus correction distribution information input circuit 155 (S107). Next, the camera CPU 151 selects defocus correction distribution information from the F value obtained in S100 (S108).

  Next, the camera CPU 151 performs the calculation of Table 3 and Formula 2 to acquire the focus position correction amount (S109). Next, the camera CPU 151 transmits a command for driving the third lens group 105 by the focus correction amount to the lens unit 101 via the focus driving circuit 161 (S110), and the focus detection process is terminated. Thereby, the focusing accuracy can be improved. If the calculation time for calculating the correction amount can be performed at a high speed, the focus position correction amount can be processed at steps S107 to S109 between S100 and S105, and the focus correction is performed when the focus determination is OK in S105. You may make it drive.

  According to the present embodiment, in an imaging apparatus having phase difference type focus detection using focus detection pixels, it is possible to improve focusing accuracy by correcting manufacturing error components of the imaging element and the imaging optical system.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, in this embodiment, light reception intensity distribution characteristic information and defocus correction distribution information on the same plane (virtual plane EPO) are used, but light reception intensity distribution characteristic information and defocus correction distribution information on different planes are used. May be.

  The image pickup apparatus of the present invention can be applied to an image pickup apparatus such as a video camera in addition to a single-lens reflex camera or a compact digital camera.

132: Image sensor, 201-204, 300, 400: Focus detection pixels, 151: Camera CPU (camera control means), ΔZ: Focus position correction amount

Claims (6)

An image sensor that has focus detection pixels for performing phase difference focus detection and photoelectrically converts an optical image formed by the imaging optical system;
Control means for adjusting the focus by moving the imaging optical system in the optical axis direction based on the detection result of the focus detection pixels of the image sensor;
Have
The control means includes information on a received light intensity distribution characteristic indicating an output signal intensity from the focus detection pixel with respect to a light incident angle of the focus detection pixel, and a defocus correction amount caused by an aberration characteristic of the photographing optical system. A correction amount is calculated using information on a defocus correction distribution representing the distribution, and the best focus position is corrected by moving the photographing optical system in the optical axis direction based on the calculated correction amount. An imaging apparatus characterized by that. The received light intensity distribution characteristic is disposed between an imaging surface of the imaging device and a diaphragm of the photographing optical system, and considers a virtual surface as a plane perpendicular to the optical axis of the photographing optical system, and light rays of the virtual surface When the passage range is divided into a plurality of regions, the output signal intensity from the focus detection pixel with respect to the incident angle of the light beam that passes through each region and enters the focus detection pixel
The defocus correction distribution represents a distribution of the defocus correction amount in each region of the virtual surface,
The control means includes
Calculating the correction amount by calculating the product of the received light intensity distribution characteristic value and the defocus correction distribution value for each region of the virtual plane, and integrating the operation result of each region and dividing by the total number of regions. The imaging apparatus according to claim 1.   The imaging apparatus according to claim 2, wherein the virtual plane is an entrance pupil plane of the photographing optical system.   The control means acquires an F value of the photographing optical system, selects the defocus correction distribution on which the light ray is incident based on the F value, and corrects the correction amount based on the selected defocus correction distribution. The imaging apparatus according to claim 1, wherein the imaging device is calculated. A first memory storing information on the received light intensity distribution characteristics;
5. The imaging apparatus according to claim 1, wherein the control unit acquires information on the received light intensity distribution characteristic from the first memory. 6. An imaging system comprising: the imaging device according to any one of claims 1 to 5; and a lens unit that is detachably attached to the imaging device.
The lens unit includes a second memory for storing information on the defocus correction distribution, and the control unit acquires the information on the defocus correction distribution from the second memory of the lens unit. Imaging system.