JP2016153909A - Focus detecting device and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detecting device and an imaging device that can correct defocus amount precisely in accordance with spherical aberration of an imaging optical system.SOLUTION: A focus detecting device comprises: a microlens array 161 in which a plurality of microlenses 161a are arranged; a plurality of light receiving sections 162a provided in correspondence with the microlenses; a light receiving element 162 which receives light beams from an optical system through the microlenses; and calculating means 163 which selects a pair of light receiving sections, among the plurality of light receiving sections, receiving a pair of light beams passed through different regions of the optical system in association with a plurality of aperture values of the optical system, and calculates an amount of image plane shift in the optical system on the basis of output from the pair of the light receiving sections.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a focus detection apparatus and an imaging apparatus.

  A camera system is known that corrects the defocus amount in accordance with the spherical aberration of the imaging optical system and detects an optimal in-focus position (Patent Document 1). The lens barrel of this camera system stores spherical aberration correction data corresponding to the two open-equivalent F values of the focus detection optical system. Then, these two spherical aberration correction data are read by the mounted camera body, and the two spherical aberration correction data are multiplied by an optimum weighting coefficient according to the aperture equivalent F value specific to the focus detection optical system of the camera body. Then, a spherical aberration correction amount suitable for the focus detection optical system is calculated.

JP-A-62-227108

  However, the spherical aberration correction amount obtained by the conventional camera system described above is calculated uniformly, and is not a correction amount for the focus detection optical system unique to each camera body. Therefore, an error due to individual differences in manufacturing the camera body is included.

  The problem to be solved by the present invention is to provide a focus detection device and an imaging device capable of accurately correcting the defocus amount according to the spherical aberration of the imaging optical system.

  The present invention solves the above problems by the following means. In addition, although the code | symbol corresponding to drawing which shows embodiment of this invention is attached | subjected and demonstrated, this code | symbol is only for making an understanding of invention easy, and is not the meaning which limits invention.

  The focus detection apparatus according to the present invention includes a microlens array (161) in which a plurality of microlenses (161a) are arranged, and a plurality of light receiving units (162a) provided corresponding to the microlenses, through the microlenses. A light receiving element (162) that receives a light beam from the optical system, and a pair of light receiving units that receive a pair of light beams that have passed through different regions of the optical system among the plurality of light receiving units. And a calculation means (163) for selecting an aperture value and calculating an image plane shift amount of the optical system based on outputs of the pair of light receiving units.

  In the focus detection apparatus according to the above invention, the calculation means (163) calculates a plurality of image plane deviation amounts corresponding to the plurality of aperture values, and based on the calculation result, the calculation unit (163) corresponds to the specific aperture value. An image plane shift amount of the optical system can be calculated.

  In the focus detection apparatus according to the invention described above, the calculation means (163) may be configured such that the optical unit is based on outputs obtained by the plurality of light receiving units corresponding to the microlenses according to an image height of the image by the optical system. The image plane deviation amount of the system can be calculated.

  Further, in the focus detection apparatus according to the above invention, the calculation means (163) is different from the plurality of aperture values based on the calculation result of the plurality of image plane deviation amounts corresponding to the plurality of aperture values. The image plane deviation amount of the optical system corresponding to the aperture value can be calculated.

  Further, in the focus detection apparatus according to the above invention, the calculation means (163) may be configured to vary the selection of the pair of light receiving units according to the arrangement position of the microlenses on the microlens array. it can.

  An imaging device (1) according to the invention includes the focus detection device according to the invention described above and an imaging means (110) for capturing an image by the optical system.

  In the imaging apparatus according to the above invention, the calculation unit (163) obtains the image plane deviation amount corresponding to the control aperture value of the optical system when imaging is performed by the imaging unit, and is based on the image plane deviation amount. And a focus detection means (163K) for detecting the focus adjustment state of the optical system.

  The imaging apparatus according to the invention further includes a contrast detection unit (163G) that detects a contrast of an image by the optical system based on an output obtained by a light receiving element corresponding to the microlens. The focus adjustment state can be detected based on the output of the light receiving element whose contrast detected by the contrast detecting means is a predetermined value or more.

  Further, the imaging apparatus according to the above invention may be configured to include a storage unit (163J) that stores the image plane shift amount calculated by the calculation unit in association with the plurality of aperture values.

  According to the above invention, the defocus amount can be accurately corrected according to the spherical aberration of the imaging optical system.

It is a block diagram which shows the single-lens reflex digital camera which concerns on embodiment of invention. It is a block diagram which shows the structure of the focus detection apparatus of the camera shown in FIG. It is a figure which shows the optical arrangement | positioning of the focus detection apparatus of the camera shown in FIG. FIG. 2 is a plan view showing an arrangement state of focus detection optical systems and focus detection sensors of the camera shown in FIG. 1. It is sectional drawing which shows the focus detection optical system and focus detection sensor of the camera shown in FIG. It is a top view which expands and shows one focus detection optical system and focus detection sensor of the camera shown in FIG. It is a top view which shows the example of selection of a pair of photoelectric conversion element among the one focus detection optical system and focus detection sensor which are shown to FIG. 3D. It is a top view which shows the other selection example of a pair of photoelectric conversion element among the one focus detection optical system and focus detection sensor which are shown to FIG. 3D. It is a top view which shows the other selection example of a pair of photoelectric conversion element among the one focus detection optical system and focus detection sensor which are shown to FIG. 3D. It is a top view which shows the other selection example of a pair of photoelectric conversion element among the one focus detection optical system and focus detection sensor which are shown to FIG. 3D. It is a figure which shows the imaging | photography screen observed with the finder shown in FIG. FIG. 2 is a diagram illustrating a relationship between a pixel interval and an aperture value F of the focus detection apparatus illustrated in FIG. 1. 6 is a graph for explaining a method of calculating a shift amount x in the focus detection apparatus of the camera shown in FIG. 1. It is a graph which shows the relationship of the focus position with respect to the aperture value calculated | required in the focus detection apparatus shown in FIG. It is a top view which shows the arrangement | sequence state of the focus detection optical system and focus detection sensor which concern on other embodiment of the camera shown in FIG. It is a top view which expands and shows one focus detection optical system and focus detection sensor of FIG. 7A.

  Hereinafter, embodiments of the invention will be described with reference to the drawings. In the following, an embodiment in which the above invention is applied to an interchangeable lens single-lens reflex digital camera will be described with reference to the drawings. However, the above invention is also applicable to any imaging device or lens fixed camera that adjusts the focus of a photographing lens. can do.

  FIG. 1 is a block diagram showing a single-lens reflex digital camera 1 (hereinafter simply referred to as a camera 1) according to an embodiment of the invention. The general configuration of the camera other than the configuration related to the focus detection device and the imaging device of the invention is described above. Some illustrations and explanations thereof are omitted.

  The camera 1 of this example includes a camera body 100 and a lens barrel 200, and the camera body 100 and the lens barrel 200 are detachably coupled by a mount unit 300.

  The lens barrel 200 incorporates a photographing optical system including a photographing lens 210 including a focus lens 211 and a zoom lens 212, a diaphragm device 220, and the like.

  The focus lens 211 is provided so as to be movable along the optical axis L <b> 1, and its position or amount of movement is detected by the encoder 260 and its position is adjusted by the lens drive motor 230. The focus lens 211 can move in the direction of the optical axis L1 from the end on the camera body side (closest end) to the end on the subject side (infinite end) by the rotation of the rotating cylinder. Incidentally, information on the position or movement amount of the focus lens 211 detected by the encoder 260 is transmitted to the lens drive control unit 165 via the lens control unit 250. The lens drive motor 230 is driven by a drive signal received from the lens drive control unit 165 via the lens control unit 250 in accordance with a drive amount and a drive speed calculated based on a focus detection result described later.

  The aperture device 220 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light beam that passes through the photographing optical system and reaches the image sensor 110. The aperture diameter is adjusted by the aperture device 220 by, for example, transmitting a signal corresponding to the aperture value calculated in the automatic exposure mode from the camera control unit 170 to the aperture drive unit 240 via the lens control unit 250. . The aperture diameter is adjusted by a manual operation by the operation unit 150 provided in the camera body 100, and a signal corresponding to the set aperture value is transmitted from the camera control unit 170 to the aperture drive unit 240 via the lens control unit 250. This is also done by sending it. The aperture diameter of the aperture device 220 is detected by an aperture aperture sensor (not shown), and the current aperture diameter is recognized by the lens controller 250.

  The lens barrel 200 is provided with a lens control unit 250. The lens control unit 250 includes a microprocessor and peripheral components such as a memory, and is electrically connected to the camera control unit 170. The lens control unit 250 receives information such as a defocus amount and an aperture control signal from the camera control unit 170, and a camera. Lens information, for example, an open F value unique to the photographing lens 210 is transmitted to the control unit 170.

  On the other hand, the camera body 100 includes a mirror system 120 for guiding the light flux from the subject to the image sensor 110, the finder 135, the photometric sensor 137, and the focus detection optical system 161. The mirror system 120 includes a quick return mirror 121 that rotates by a predetermined angle between the observation position and the photographing position of the subject around the rotation axis 123, and the quick return mirror 121 that is pivotally supported by the quick return mirror 121. And a sub mirror 122 that rotates in accordance with the rotation.

  In FIG. 1, a state where the mirror system 120 is at the observation position of the subject is indicated by a solid line, and a state where the mirror system 120 is at the photographing position of the subject is indicated by a two-dot chain line. The mirror system 120 is inserted on the optical path of the optical axis L1 in the state where the subject is in the observation position, while rotating so as to retract from the optical path of the optical axis L1 in the state where the subject is in the photographing position.

  The quick return mirror 121 is composed of a half mirror, and in a state where the subject is at the observation position, the quick return mirror 121 reflects a part of the light flux (optical axes L2 and L3) from the subject (optical axis L1). Then, the light is guided to the finder 135 and the photometric sensor 137, and a part of the light beam (optical axis L4) is transmitted to the sub mirror 122. On the other hand, the sub mirror 122 is constituted by a total reflection mirror, and guides the light beam (optical axis L4) transmitted through the quick return mirror 121 to the focus detection optical system 161.

  Therefore, when the mirror system 120 is at the observation position, the light beam (optical axis L1) from the subject is guided to the finder 135, the photometric sensor 135, and the focus detection optical system 161, and the subject is observed and exposed. Calculation and detection of the focus adjustment state of the focus lens 211 are executed. When the photographer fully presses the release button, the mirror system 120 rotates to the photographing position, and the light flux (optical axis L1) from the subject is guided to the image sensor 110, and the photographed image data is stored in a memory (not shown).

  The image sensor 110 is provided on the camera body 100 on the optical axis L1 of the light beam from the subject and at a position that becomes the planned focal plane of the photographing lens 210, and a shutter 111 is provided on the front surface thereof. The imaging element 110 is a two-dimensional array of a plurality of photoelectric conversion elements, and can be configured by a two-dimensional CCD image sensor, a MOS sensor, a CID, or the like.

  The shutter 111 disposed on the front surface of the image sensor 110 is opened for the number of shutter seconds set based on the exposure calculation result or set by the photographer when the shutter button included in the operation unit 150 is fully pressed (during shutter release). Then, the image sensor 110 is exposed. The electrical image signal photoelectrically converted by the image sensor 110 is subjected to image processing by the camera control unit 170 and then stored in a memory (not shown). Note that the memory for storing the photographed image can be constituted by a built-in memory or a card-type memory.

  On the other hand, the light beam from the subject light reflected by the quick return mirror 121 forms an image on a focusing screen 131 disposed on a surface optically equivalent to the image sensor 110, and passes through the pentaprism 133 and the eyepiece lens 134. Guided to the photographer's eyeball. At this time, the transmissive liquid crystal display 132 superimposes and displays a focus detection area mark on the subject image on the focusing screen 131 and relates to shooting such as the shutter speed, aperture value, and number of shots in an area outside the subject image. Display information. As a result, the photographer can observe the subject, its background, and photographing related information through the finder 135 in the photographing preparation state.

  The photometric sensor 137 is composed of a two-dimensional color CCD image sensor or the like, and divides the photographing screen into a plurality of regions and outputs a photometric signal corresponding to the luminance of each region in order to calculate an exposure value at the time of photographing. Image information detected by the photometric sensor 137 is output to the camera control unit 170 and used for automatic exposure control.

  The operation unit 150 is a shutter release button or an input switch for the photographer to set various operation modes of the camera 1. Switching between the autofocus mode / manual focus mode and the autofocus mode also includes a one-shot mode / continuous mode. It is possible to switch between the numeric modes. The shutter release button is turned on when the shutter release button is fully pressed, but in addition to this, when the button is pressed halfway in the autofocus mode, the focusing operation of the focus lens is turned on, and when the button is released, it is turned off. Various modes set by the operation unit 150 are transmitted to the camera control unit 170, and the operation of the entire camera 1 is controlled by the camera control unit 170.

  The camera body 100 is provided with a camera control unit 170. The camera control unit 170 includes peripheral components such as a microprocessor and a memory, and is electrically connected to the lens control unit 250 through an electric signal contact unit provided in the mount unit 300, and receives lens information from the lens control unit 250. At the same time, information such as a defocus amount and an aperture control signal is transmitted to the lens control unit 250. The camera control unit 170 reads out image information from the image sensor 110 as described above, performs predetermined information processing as necessary, and outputs the information to a memory (not shown). The camera control unit 170 controls the entire camera 1 such as correction of captured image information and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 200.

  The focus detection optical system 161, the focus detection sensor 162, the focus detection calculation unit 163, and the lens drive amount calculation unit 164 shown in FIG. 1 constitute a phase difference detection type focus detection device and represent the focus adjustment state of the photographing lens 210. Detect the defocus amount.

  The focus detection apparatus of this example will be described with reference to FIGS.

  FIG. 2 is a block diagram showing the configuration of the focus detection apparatus, and is a block diagram showing in detail the configuration of the focus detection calculation unit 163 shown in FIG. 1 according to the processing procedure. 3A is a view showing the optical arrangement of the focus detection device, and FIG. 3B is a plan view showing an arrangement state of the focus detection optical system 161 and the focus detection sensor 162, and is a view of the microlens array 161 viewed from the sub mirror 122 side. 3C is a cross-sectional view showing the focus detection optical system 161 and the focus detection sensor 162 (cross-sectional view taken along the line IIIC-IIIC in FIG. 3B), and FIG. 3D is an enlarged view of one microlens 161a and the focus detection sensor 162. It is a top view.

  The focus detection optical system 161 is a microlens array in which a plurality of microlenses 161a are two-dimensionally densely squarely arranged as shown in FIG. 3B, and a position that is a planned focal plane of the photographing lens 210 as shown in FIG. 3A. It is arranged in the vicinity of P1. Hereinafter, it is also referred to as a microlens array 161. The microlens array 161 can be arranged so as to coincide with the position P1 serving as the planned focal plane, but can also be arranged shifted from the position P1 serving as the planned focal plane. When they are arranged to coincide with each other, the portion becomes a dead zone when there is a contrast of the subject image between the microlenses 161a. However, such a dead zone can be avoided by shifting the portion.

  The focus detection sensor 162 is a light receiving element array in which a plurality of photoelectric conversion elements 162a are two-dimensionally densely squarely arranged as shown in FIG. 3D, and is arranged at a substantially focal position of the microlens array 161 as shown in FIG. 3C. Has been. Hereinafter, it is also referred to as a light receiving element array 162. FIG. 3C shows the spread of the light beam received by the photoelectric conversion element 162a at or near the center of each microlens 161a.

  The microlens 161a of this example is a circular microlens, and the microlens array 161 is a circular array of such circular macrolenses 161a. The vertical and horizontal directions in the figure coincide with the vertical and horizontal directions of the imaging screen imaged by the imaging element 110. Although a regular hexagonal microlens 161a is arranged in a honeycomb shape instead of the circular microlens, it is possible to avoid a dead zone of focus detection between lenses that occurs when circular microlenses are arranged. Will be described later.

  On the other hand, the photoelectric conversion element array 162 arranged behind the microlens array 161 is a square array of square photoelectric conversion elements 162a. One photoelectric conversion element 162a is formed to be smaller than one microlens 161a. As shown in an enlarged view in FIG. 3D, a plurality of photoelectric conversion elements 162a are included in a range in which one microlens 161a is vertically projected. Yes. These photoelectric conversion elements 162a are photoelectric conversion elements 162a provided corresponding to the microlenses 161a.

  As described above, the microlens array 161 is disposed at or near the position P1 (a surface optically equivalent to the image pickup surface of the image pickup device 110) that is the planned focal plane of the image pickup lens 210. The same optical image is projected. On the light receiving element array 162, the pupil image of the photographing lens 210 is formed by each micro lens 161a, and each photoelectric conversion element 162a of the light receiving element array 162 corresponds to each part of the pupil. If the conversion element 162a is selected and its output is synthesized, an image photographed with a diaphragm corresponding to the photoelectric conversion element 162a can be obtained.

  The focus detection of this embodiment is performed according to the following procedure.

  The A / D converter 163A of the focus detection calculation unit 163 shown in FIG. 2 converts the analog image signal output from the focus detection sensor (light receiving element array) 162 into a digital image signal and outputs it to the memory 163B. The memory 163B outputs this digital image signal in response to a request from the microlens optical axis center determining unit 163C.

  At this time, when any of the focus detection areas AFP1 to AFP11 shown in FIG. 4 is selected, the photoelectric conversion element 162a corresponding to the microlens 161a corresponding to the predetermined range corresponding to the selected focus detection area is selected. Read output only.

  FIG. 4 is a diagram showing a photographing screen 135A observed from the finder 135 including the focus detection area AFP. In this example, it is assumed that eleven focus detection areas AFP1 to AFP11 are set on the photographing screen 135A. This display is performed when the liquid crystal display 132 superimposes marks representing the positions of eleven focus detection areas on the subject image on the focusing screen 131. Then, the photographer operates the operation unit 150 to select a desired focus detection area AFP, or automatically selects the focus detection area AFP by a predetermined sequence based on data such as automatic exposure. For example, when the focus detection area AFP7 shown in FIG. 4 is selected, the photoelectric conversion element 162a corresponding to the microlens 161a corresponding to a predetermined range (shown by a dotted line in FIG. 4) centering on the focus detection area AFP7. Read the output from.

  Here, in order to secure the above-described pupil conjugate relationship, it is necessary to calculate the pupil center position of the taking lens 210. This is because it is uncertain which photoelectric conversion element 162a corresponds to which position of which microlens 161a because the microlens array 161 and the light receiving element array 162 are usually manufactured and assembled independently. It is. In addition, since it is assumed that the lens barrel 200 is replaced in the single-lens reflex camera 1, the position of the pupil of the photographing lens 210 viewed from the microlens 161a changes. For this reason, the microlens optical axis center determining unit 163C determines the position of the photoelectric conversion element 162a that is conjugate with the pupil center position of the photographing lens 210 as the center of the microlens 161a.

  The position of the photoelectric conversion element 162a corresponding to the center of each microlens 161a is obtained from the position (image height) of the microlens 161a with respect to the optical axis L1 of the photographing lens 210 and the distance from the microlens 161a to the pupil of the photographing lens 210. be able to. For example, in a lens barrel in which the distance from the microlens 161a to the pupil of the photographing lens 210 is known, a data group at the center position of each microlens 161a is stored in advance in the memory of the lens control unit 250 or the like. Based on the distance to the pupil of the photographic lens 210, the current center position of the photographic lens 210 is calculated by interpolation or extrapolation.

  Then, the obtained image data of the photoelectric conversion element 162a corresponding to the center of the optical axis of each microlens 161a or the periphery of the center is extracted from the image data stored in the memory 163B. In the light receiving element array 162 having the photoelectric conversion element 162a shown in FIG. 3D, for example, image data of the central photoelectric conversion element 162c filled in the same figure is extracted.

  When the distance to the pupil of the photographing lens 210 is unknown, the distance to the pupil can be set to an infinite position, and the center position obtained only from the positional relationship between the microlens 161a and the photoelectric conversion element 162a can be used. .

  When the optical axis center of each microlens is determined in this way, in order to evaluate the spherical aberration of the photographing lens 210, a plurality of baseline lengths are set with the optical axis center as the center point. The focal position of the lens varies according to the beam diameter represented by the aperture value F, and the degree of variation varies depending on the lens, and also varies depending on individual differences in manufacturing even for lenses of the same model. Therefore, as shown in FIGS. 3E to 3H, a pair of photoelectric conversion elements 162d and 162d that are symmetrical with respect to the photoelectric conversion element 162c corresponding to the center of the optical axis of the microlens are selected.

  When the focal length of the microlens 161a shown in FIGS. 3E to 3H is 90 μm and the size of one photoelectric conversion element 162a is 3.2 μm × 3.2 μm, the aperture value F is an effective aperture (pixel interval). As shown in FIG. 3E, F = 14 when selected at a pixel interval of 2 pixels as shown in FIG. 3E, and F = 7 when selected at a pixel interval of 4 pixels as shown in FIG. 3F. Each optical information of F = 4.7 is obtained when selected at a pixel interval of 6 pixels as shown in 3G, and F = 3.5 when selected at a pixel interval of 8 pixels as shown in FIG. 3H. be able to. Although not shown in FIG. 4, when 10 pixel intervals are selected, optical information of F = 2.8 can be obtained. The relationship between the pixel interval and the aperture value is shown in FIG.

  Since each photoelectric conversion element 162a is conjugate with the corresponding position of the pupil of the photographing lens 210, the optical information obtained thereby is information correlated with the focal position when the aperture value F is changed. Become.

  The calculated aperture value selection unit 163D shown in FIG. 2 uses a pixel interval for determining the baseline length, such as 2 pixels as the first step, 4 pixels as the second step, 6 pixels as the third step, and 8 pixels as the fourth step. Is output to the pixel pattern table 163E.

  The upper limit of the pixel interval is determined by the minimum aperture value that can be taken by the microlens 161a. However, the upper limit of the pixel interval is defined by the open aperture value of the photographing lens 210 by sufficiently reducing the minimum aperture value of the microlens 161a. Can do. That is, when the aperture value data of the photographing lens 210 is received from the lens barrel 200 side, the calculated aperture value selection unit 163D determines the aperture value and pixel interval of each step up to the vicinity of the maximum aperture value accordingly. , Output this step by step.

  When the pixel interval is determined based on the open aperture value data of the photographic lens 210, the pixel selection unit 163F extracts a pixel selection pattern representing the relationship between the aperture value and the interval from the pixel pattern table 163E. In addition, although the pixel pattern extracted here may select two photoelectric conversion elements 162a with a predetermined interval, a plurality of photoelectric conversion elements 162a orthogonal to the base line can also be selected based on conditions such as the amount of incident light. . The example shown in FIGS. 3E to 3H shows an example in which three photoelectric conversion elements 162a are selected.

  The actual photoelectric conversion element 162a is specified from the optical axis center position obtained by the microlens optical axis center determination unit 163C and the pixel pattern extracted by the pixel pattern table 163E.

  The target detection row extraction unit 163G reads out and integrates the outputs of the pair of photoelectric conversion elements 162a constituting the pattern from the memory 163B, and indicates the image shift amount due to the pair of light beams that have passed through different pupil regions of the photographing lens 210. A detection signal, that is, a pair of focus detection signal trains is generated. Then, the first signal sequence {aj} and the second signal sequence {bj} (j is a natural number) are extracted and output to the image shift amount calculation unit 163H.

  In the image shift amount calculation unit 163H, detection of the focal position by the pupil division phase difference method is executed. That is, the image shift amount calculation unit 163H calculates the defocus amount by executing the image shift calculation using the first signal sequence {aj} and the second signal sequence {bj}. The first signal sequence {aj} and the second signal sequence {bj} are respectively aj (j = 1, 2,... N) and bj (j = 1) from positions symmetrical with respect to the center along the base line in the microlens 161a. , 2,... N) is stored, the focal position, that is, the focal shift amount from the planned focal plane is the parallax of the pupil position that is optically conjugate to the photoelectric conversion element 162a. appear. That is, the one-dimensional curve represented by the data sequence cut out from the N microlenses 161a is shifted by the amount of parallax between the first signal sequence {aj} and the second signal sequence {bj}. The focus detection calculation in the image shift amount calculation unit 163H obtains the phase shift amount between the two data strings on the assumption that almost the same images are projected on the two data strings.

  In this calculation, the difference between the first signal sequence {aj} and the second signal sequence {bj} is calculated while shifting the relative radix of the two number sequences, and the amount of deviation that minimizes this is obtained. First, a correlation calculation value Dk of a pair of images (signal sequences) is obtained from the first signal sequence {aj} and the second signal sequence {bj} by the following equation.

[Formula 1] Dk = Σ | a _{i + k} −b _i |
Since Dk represented by Equation 1 is a discrete value, the minimum value can be regarded as the vicinity of the true minimum value. Therefore, the amount of deviation x is calculated by interpolating from the Dk values before and after the minimum value Dk. If the spatial change of the first signal sequence {aj} and the second signal sequence {bj} is expressed as a sine change, D (x) when a continuous function is used is the absolute value of the sine wave, and thus D (x ) Can be obtained by a simple linear approximation based on discrete Dk.

  FIG. 6 is a graph for explaining a method of calculating the shift amount x in the focus detection apparatus of this example. As shown in FIG. 6, let Dk be the minimum Dk, and Dk adjacent to this be Di + 1 and Di-1. First, the larger one of Di + 1 and Di-1 is selected. In the example shown in the figure, Di-1 is larger, so Di-1 is selected. Next, let L1 be a straight line connecting the selected Di-1 and Di. When the slope of the straight line L1 is α, the straight line passing through Di + 1 with the slope of −α is L2, and when the intersection of the straight lines L1 and L2 is obtained, the x of the intersection is the above-described deviation amount x.

  When the image shift amount calculation unit 163H determines a focal position for one pixel interval (for example, 2 pixels), that is, an aperture value (for example, F = 14), the same applies to the next pixel interval (for example, 4 pixels, F = 7). The focal position at the aperture value is obtained. This process is executed for all the pixel intervals shown in FIG. 5, and the data results of the respective focal positions obtained are stored in the storage unit 163J.

  For example, as shown in FIG. 5, an example in which the results for pixel intervals of 2, 4, 6, 8, and 10 pixels are stored for each aperture value F is indicated by black circles in FIG. This represents the spherical aberration of the taking lens 210 as a discrete value. Then, the correction unit 163K reads the actual aperture value f at the time of shooting, and uses the nearby measurement value interpolation method or extrapolation method from the table shown in FIG. 7 stored in the storage unit 163J. The focal point position is corrected to an optimum focal point position where the image shift amount due to the spherical aberration 210 is zero.

  Here, since the aperture value f is obtained by dividing the focal length by the effective aperture, it is corrected by the linear pixel dimension-effective aperture using the inverse 1 / f of the aperture value f. That is, in the correction table, the reciprocal 1 / f of the corresponding aperture value f is associated with the measured value.

When the reciprocal 1 / f of the aperture value f of this correction table is xi and the measurement value is yi, the correction table is represented by {xi, yi} (where xi <x _{i + 1} ). When the photographing aperture value f is read, xi satisfying xi ≦ ff ≦ xi _{+ 1} is obtained from the reciprocal ff = 1 / f by interpolation. When there is no value satisfying xi ≦ ff ≦ x _{i + 1} , there is a value to be found outside the correction table, so xi = x0 or xi = x _n−1 (n is the final value of the correction table). Find xi by the insertion method. In this way, the distribution coefficient s is obtained from the following formula 2, and the nearby measurement value is proportionally calculated from the distribution coefficient s, whereby the focal position Y corresponding to the photographing aperture value can be obtained.

[Formula 2]
s = (ff−xi) / (x _{i + 1} −xi)
Y = (1-s) yi + sy _{i + 1}
This correction can also be performed by a spline function.

Returning to FIG. 2, the lens drive amount calculation unit 164 calculates a lens drive amount Δd for making the shift amount x zero based on the shift amount x sent from the defocus calculation unit 163. Output to the lens drive control unit 165.

  The lens drive control unit 165 sends a drive command to the lens drive motor 230 while taking in the lens drive amount Δd sent from the lens drive amount calculation unit 164, and drives the focus lens 211 by the lens drive amount Δd.

  As described above, in the camera 1 of this example, a plurality of pixel intervals, that is, focal positions corresponding to the aperture value are calculated from the image of the focus detection sensor 162, and this is used to calculate the luminous flux corresponding to the actual imaging aperture value. Since the focal position is obtained, it is possible to detect the focal point with high accuracy even with a photographic lens having different focal position variations due to spherical aberration.

<< Other embodiments >>
In the embodiment described above, the microlens array 161 in which the circular microlenses 161a shown in FIG. 3B are squarely arranged is used. However, the microlens array 161 in which regular hexagonal macrolenses 161a are densely arranged in a honeycomb shape can also be used. .

  FIG. 8A is a plan view showing an arrangement state of focus detection optical systems and focus detection sensors according to another embodiment, and is a view of the microlens array 161 viewed from the sub mirror 122 side. Although the photoelectric conversion element 162a is shown only behind a part of the microlenses 161a in the same figure, the photoelectric conversion element 162a is similarly arranged behind the other microlenses 161a. FIG. 8B is an enlarged plan view showing one focus detection optical system and focus detection sensor.

  The focus detection optical system 161 of this example is a microlens array in which a plurality of microlenses 161a are arranged densely (in a honeycomb shape) two-dimensionally as shown in FIG. 8A, and is shown in FIG. 3A of the above embodiment. In the same manner as described above, the photographic lens 210 is disposed in the vicinity of the position P1 serving as the planned focal plane.

  On the other hand, the focus detection sensor 162 is a light receiving element array in which a plurality of photoelectric conversion elements 162a are densely arranged in a two-dimensional manner as shown in FIG. 8A, and similarly to that shown in FIG. 3C of the above embodiment, The microlens array 161 is disposed at a substantially focal position.

  The microlens 161a of the present example has a shape obtained by cutting a circular microlens whose lens surface shape is indicated by a one-dot chain line into a regular hexagon, and has the same function as the circular microlens. The microlens array 161 has such regular hexagonal macro lenses 161a arranged in a honeycomb shape.

  By arranging regular hexagonal microlenses 161a in a honeycomb shape in this way, it is possible to avoid a dead zone in focus detection between lenses that occurs when circular microlenses are arranged. The vertical and horizontal directions in the figure coincide with the vertical and horizontal directions of the imaging screen imaged by the imaging element 110.

  On the other hand, the photoelectric conversion element array 162 disposed behind the microlens array 161 is a square array of square photoelectric conversion elements 162a, as in the above embodiment. One photoelectric conversion element 162a is formed to be smaller than one microlens 161a. As shown in an enlarged view in FIG. 8B, a plurality of photoelectric conversion elements 162a are included in a range in which one microlens 161a is vertically projected. Yes.

  In the microlens array 161 of this example configured as described above, since regular hexagonal microlenses 161a are arranged in a honeycomb shape as shown in FIG. 8A, the arrangement of image data is also in a honeycomb shape.

  Also in this embodiment, a plurality of pixel intervals, that is, focal positions corresponding to the aperture value are calculated from the image of the focus detection sensor 162, and the focal position of the luminous flux corresponding to the actual photographing aperture value is obtained using this. Even with a photographic lens that varies in focal position variation due to spherical aberration, the focal point can be detected with high accuracy.

  3D and 8B show a light receiving element array 162 in which a plurality of photoelectric conversion elements 162a are squarely arranged for each microlens 161a. However, the number and arrangement of the photoelectric conversion elements 162a for each microlens 161a are shown. It is not limited to. Further, as shown in the figure, instead of arranging the photoelectric conversion element 162a for each microlens 161a, the light receiving element array 162 may be arranged for the plurality of microlenses 161a or the entire microlens array 161. Furthermore, instead of arranging the square photoelectric conversion elements 162a in a square shape, regular hexagonal photoelectric conversion elements can also be arranged in a honeycomb shape.

  In the above-described embodiment, the focus detection sensor 162 that is a two-dimensional sensor is provided separately from the image sensor 110. However, instead of this, a microlens 161a and a photoelectric conversion element 162a are provided in a part of the image sensor 110. It is also possible to detect the focus by the above-described procedure.

  Note that the present invention may be applied to a hybrid AF that uses both the pupil division phase difference detection AF and the contrast AF (mountain climbing AF) based on the image signal obtained by the image sensor 110.

DESCRIPTION OF SYMBOLS 1 ... Single-lens reflex digital camera 100 ... Camera body 110 ... Image pick-up element 161 ... Focus detection optical system (micro lens array)
161a ... Micro lens 162 ... Focus detection sensor (light receiving element array)
162a ... Photoelectric conversion element 163 ... Focus detection calculation unit 163C ... Micro lens optical axis center determination unit 163D ... Calculated aperture value selection unit 163E ... Pixel pattern table 163F ... Pixel selection unit 163G ... Target detection column extraction unit 163H ... Image shift amount calculation Unit 163J ... storage unit 163K ... correction unit 164 ... lens driving amount calculation unit 200 ... lens barrel 210 ... photographing lens 211 ... focus lens

Claims (2)

A microlens array in which a plurality of microlenses are arranged two-dimensionally;
A plurality of light receiving portions arranged in a two-dimensional manner provided for each microlens, and a light receiving element that receives a light flux from the photographing lens via the microlens
The driving amount of the focus lens of the photographing lens is determined by a signal output from a pair of light receiving units symmetrical around the light receiving unit conjugate with the pupil center position of the photographing lens among the plurality of light receiving units of the micro lens. A driving amount calculating unit for calculating;
With
The position of the light receiving unit that is conjugate to the pupil center position of the photographing lens is a two-dimensional position of the microlens from the optical axis of the photographing lens, and between the pupil of the photographing lens and the microlens. An imaging apparatus that varies depending on a distance and changes an interval between the pair of light receiving units according to an aperture value of the photographing lens. The imaging device according to claim 1,
An image shift amount due to a pair of light beams that have passed through different pupil regions of the photographing lens calculated by signals output from the pair of light receiving units is corrected by an image shift amount due to spherical aberration of the photographing lens at the aperture value. An image pickup apparatus, further comprising: focus detection means for detecting a focus adjustment state of the photographing lens based on the corrected image shift amount.

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