JP2019049737A - Focus detecting device and imaging device - Google Patents

Abstract

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 device and an imaging device.

  There is known a camera system which corrects the defocus amount according to the spherical aberration of the imaging optical system and detects an optimum in-focus position (Patent Document 1). The lens barrel of this camera system stores spherical aberration correction data respectively 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 the optimal weighting coefficient according to the aperture equivalent F value unique to the focus detection optical system of the camera body. The spherical aberration correction amount suitable for the focus detection optical system is calculated.

Japanese Patent Application Laid-Open No. 62-227108

  However, the spherical aberration correction amount obtained by the above-described conventional camera system is calculated uniformly, and is not the correction amount for the focus detection optical system unique to each camera body. Therefore, errors due to individual differences in manufacture of the camera body are included.

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

  This invention solves the said subject by the following solution means. Although the reference numerals corresponding to the drawings showing the embodiments of the present invention are given and described, the reference numerals are only for the ease of understanding of the present invention and are not intended to limit the present invention.

  A focus detection device 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, and the microlenses are intervened. Light-receiving element (162) for receiving the light flux from the optical system, and a pair of light-receiving sections for receiving a pair of light fluxes passing through different regions of the optical system among the plurality of light receiving sections And computing means (163) for computing the image plane deviation amount of the optical system based on the outputs of the pair of light receiving parts.

  In the focus detection device according to the above invention, the calculation means (163) calculates a plurality of the image plane deviation amounts corresponding to the plurality of aperture values, and the calculation means (163) calculates the plurality of image plane deviations based on the calculation result. The image plane deviation amount of the optical system can be calculated.

  Further, in the focus detection device according to the above invention, the arithmetic means (163) is configured to calculate the optical based on outputs obtained by the plurality of light receiving units corresponding to the microlenses according to the image height of the image by the optical system. It can be configured to calculate the amount of image plane deviation of the system.

  Further, in the focus detection device according to the above invention, the calculation means (163) is configured to calculate the other of the plurality of f-numbers based on the calculation result of the plurality of image plane deviations corresponding to the plurality of f-numbers. The image plane deviation amount of the optical system corresponding to the aperture value can be calculated.

  Further, in the focus detection device according to the above invention, the calculation means (163) may be configured to make the selection of the pair of light receiving sections different according to the arrangement position of the micro lens on the micro lens array. it can.

  An image pickup apparatus (1) according to the invention is characterized by comprising the focus detection apparatus according to the above invention, and an image pickup means (110) for picking up an image by the optical system.

  In the image pickup apparatus according to the above invention, the calculating means (163) obtains the image plane deviation amount corresponding to the control aperture value of the optical system when the image pickup means performs imaging, and is based on the image plane deviation amount. The optical system can be configured to include focus detection means (163K) for detecting the focusing state of the optical system.

  The imaging apparatus according to the above invention further comprises a contrast detection unit (163G) that detects the contrast of the image by the optical system based on the output obtained by the light receiving element corresponding to the microlens, and the focus detection unit The focusing state may be detected based on the output of the light receiving element whose contrast detected by the contrast detecting means is equal to or more than a predetermined value.

  The image pickup apparatus according to the present invention can be configured to include a storage unit (163J) that stores the image plane deviation amount calculated by the calculation unit in association with the plurality of aperture values.

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

FIG. 1 is a block diagram showing a single-lens reflex digital camera according to an embodiment of the present 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 of the focus detection apparatus of the camera shown in FIG. It is a top view which shows the arrangement state of the focus detection optical system of a camera shown in FIG. 1, and a focus detection sensor. It is sectional drawing which shows the focus detection optical system and focus detection sensor of a camera which are shown in FIG. It is a top view which expands and shows one focus detection optical system and focus detection sensor of a camera shown in FIG. It is a top view which shows the example of selection of a pair of photoelectric conversion element among 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 one focus detection optical system and focus detection sensor which are shown to FIG. 3D. It is a top view which shows the further another selection example of a pair of photoelectric conversion element among one focus detection optical system and focus detection sensor which are shown to FIG. 3D. It is a top view which shows the further another selection example of a pair of photoelectric conversion element among 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. It is a figure which shows the relationship between the pixel interval of the focus detection apparatus shown in FIG. 1, and aperture value F. FIG. FIG. 7 is a graph for explaining a method of calculating a shift amount x in the camera focus detection device 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 state of the focus detection optical system which concerns on other embodiment of the camera shown in FIG. 1, and a focus detection sensor. It is a top view which expands and shows one focus detection optical system and focus detection sensor of FIG. 7A.

  Hereinafter, an embodiment of the above-mentioned invention is described based on a drawing. In the following, an embodiment in which the invention is applied to a lens-interchangeable single-lens reflex digital camera will be described based on the drawings, but the invention is also applied to any imaging device and lens-fixed camera that performs focus adjustment of a shooting 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 present invention, and the general configuration of a camera other than the configuration relating to the focus detection device and the imaging device The illustration and the explanation thereof are partially omitted.

  The camera 1 according to this embodiment includes a camera body 100 and a lens barrel 200. The camera body 100 and the lens barrel 200 are detachably coupled by a mount 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, an aperture device 220, and the like.

  The focus lens 211 is provided so as to be movable along the optical axis L1, and its position is adjusted by the lens drive motor 230 while its position or movement amount is detected by the encoder 260. The focus lens 211 can move in the direction of the optical axis L1 from the end (closest end) on the camera body side to the end (infinite end) on the subject side by rotation of the rotary 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. In addition, 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 according to the drive amount and drive speed calculated based on the focus detection result described later.

  The aperture device 220 is configured to adjust the aperture diameter centered on the optical axis L <b> 1 in order to limit the light amount of the light flux passing through the imaging optical system and reaching the imaging device 110. Adjustment of the aperture diameter by the aperture device 220 is performed, for example, by 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. . Also, for adjustment of the aperture diameter, a signal corresponding to the set aperture value is sent from the camera control unit 170 to the diaphragm drive unit 240 via the lens control unit 250 by manual operation by the operation unit 150 provided in the camera body 100. It is also done by being sent. The aperture diameter of the diaphragm device 220 is detected by a diaphragm aperture sensor (not shown), and the lens controller 250 recognizes the current aperture diameter.

  A lens control unit 250 is provided in the lens barrel 200. 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 the defocus amount and the aperture control signal from the camera control unit 170. Lens information, for example, an open F-number 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 a light flux from a 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 which is rotated by a predetermined angle between the observation position of the subject and the photographing position around the rotation axis 123, and the quick return mirror 121 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 into the optical path of the optical axis L1 in the state of observation of the subject, and rotates so as to retract from the optical path of the optical axis L1 in the state of imaging of the subject.

  The quick return mirror 121 is a half mirror, and reflects light flux (optical axes L2 and L3) of a part of the light flux (optical axis L1) from the subject by the quick return mirror 121 when the object is at the observation position. Then, the light is guided to the finder 135 and the photometric sensor 137, and a part of the luminous flux (optical axis L4) is transmitted and guided to the sub mirror 122. On the other hand, the sub mirror 122 is 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 flux (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 by the photographer. Calculation and detection of the focusing state of the focusing lens 211 are performed. Then, when the photographer fully presses the release button, the mirror system 120 is rotated to the photographing position, the light flux from the subject (optical axis L1) is guided to the image sensor 110, and the photographed image data is stored in a memory (not shown).

  The imaging element 110 is provided on the light axis L1 of the light flux from the subject of the camera body 100 and at a position to be a planned focal plane of the photographing lens 210, and the shutter 111 is provided on the front surface thereof. The imaging device 110 is a device in which a plurality of photoelectric conversion devices are two-dimensionally arranged, 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 of the image sensor 110 opens based on the result of the exposure calculation or when the shutter number set by the photographer is released when the shutter button included in the operation unit 150 is fully pressed (during shutter release) And expose the imaging element 110. The electric image signal photoelectrically converted by the image pickup element 110 is image-processed by the camera control unit 170 and stored in a memory (not shown). The memory for storing the photographed image can be configured by a built-in memory, a card type memory, or the like.

  On the other hand, the light flux from the subject light reflected by the quick return mirror 121 forms an image on the focusing plate 131 disposed on the surface optically equivalent to the imaging device 110, and passes through the pentaprism 133 and the eyepiece lens 134. It is led to the eyeball of the photographer. At this time, the transmission type liquid crystal display 132 superimposes and displays a focus detection area mark etc. on the subject image on the focusing screen 131, and relates to photographing such as shutter speed, aperture value, and number of shots in an area outside the subject image. Display information Thus, the photographer can observe the subject and the background thereof, shooting related information, and the like through the finder 135 in the shooting preparation state.

  The photometric sensor 137 is configured of a two-dimensional color CCD image sensor or the like, and divides the shooting screen into a plurality of areas to output a photometric signal according to the brightness of each area in order to calculate an exposure value at the time of shooting. 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, and switches between the auto focus mode / manual focus mode and the one shot mode / conti in the auto focus mode. It is possible to switch the nuisance mode. The shutter is turned on when the shutter release button is fully pressed, but in addition to this, when the button is pressed halfway in the auto focus mode, the focusing operation of the focusing lens is turned on, and turned off when the button is released. The 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.

  A camera control unit 170 is provided in the camera body 100. The camera control unit 170 includes a microprocessor and peripheral components such as a memory, and is electrically connected to the lens control unit 250 by the electrical 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 the defocus amount and the aperture control signal is transmitted to the lens control unit 250. Further, as described above, the camera control unit 170 reads out the image information from the imaging device 110, performs predetermined information processing as necessary, and outputs the information to a memory (not shown). Further, the camera control unit 170 controls the entire camera 1 such as correction of photographed 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 driving amount calculation unit 164 shown in FIG. 1 constitute a focus detection device of a phase difference detection method and represent the focus adjustment state of the photographing lens 210. Detect the defocus amount.

  The focus detection apparatus of this embodiment will be described with reference to FIGS. 2 to 3D.

  FIG. 2 is a block diagram showing the configuration of the focus detection apparatus, and is a block diagram showing the configuration of the focus detection calculation unit 163 shown in FIG. 1 in detail in accordance with the processing procedure. FIG. 3A is also a view showing the optical arrangement of the focus detection device, and FIG. 3B is a plan view showing the arrangement of the focus detection optical system 161 and the focus detection sensor 162, as seen from the micro mirror array 161 from the sub mirror 122 side. FIG. 3C is a cross-sectional view showing the focus detection optical system 161 and the focus detection sensor 162 (cross-sectional view along the line IIIC-IIIC in FIG. 3B), and FIG. 3D shows 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 micro lens array in which a plurality of micro lenses 161a are densely squarely arranged in a two-dimensional manner as shown in FIG. 3B, and as shown in FIG. It is arranged near P1. Hereinafter, it is also referred to as a microlens array 161. The microlens array 161 can be arranged to coincide with the position P1 to be the planned focal plane, but can be arranged to be shifted from the position P1 to be the planned focal plane. In the case where they are arranged to coincide with each other, when there is a contrast of the object image between the microlenses 161a, that portion becomes a dead zone, but by arranging them in a shifted manner, generation of such a dead zone can be avoided.

  The focus detection sensor 162 is a light receiving element array in which a plurality of photoelectric conversion elements 162a are densely squarely arranged in a two-dimensional manner as shown in FIG. 3D, and is disposed substantially at the focus position of the microlens array 161 as shown in FIG. It is done. 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 of the microlenses 161a.

  The micro lens 161a of this example is a circular micro lens, and the micro lens array 161 is one in which such circular macro lenses 161a are squarely arranged. The upper, lower, left, and right directions in the figure coincide with the upper, lower, left, and right directions of the imaging screen imaged by the imaging element 110. By arranging regular hexagonal micro lenses 161a in a honeycomb shape instead of circular micro lenses, it is possible to avoid the dead zone of focus detection between lenses which occurs when circular micro lenses are arranged, but Will be described later.

  On the other hand, the photoelectric conversion element array 162 disposed behind the microlens array 161 is a square photoelectric conversion element 162a. One photoelectric conversion element 162a is formed smaller than one microlens 161a, and 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. There is. These photoelectric conversion elements 162a are photoelectric conversion elements 162a provided corresponding to the micro lenses 161a.

  Now, as described above, since the microlens array 161 is disposed at or near the position P1 (the plane optically equivalent to the imaging surface of the imaging device 110) to be the planned focal plane of the imaging lens 210, the imaging device 110 The same optical image as is projected. A pupil image of the photographing lens 210 is formed on each of the light receiving element arrays 162 by the respective micro lenses 161a, and each photoelectric conversion element 162a of the light receiving element array 162 corresponds to each portion of the pupil. If the conversion element 162a is selected and the outputs thereof are combined, an image captured by the aperture corresponding to the photoelectric conversion element 162a is obtained.

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

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

  At this time, when any of the focus detection areas AFP 1 to 11 shown in FIG. 4 is selected, the photoelectric conversion element 162 a corresponding to the micro lens 161 a corresponding to the predetermined range corresponding to the selected focus detection area is selected. Read only the output.

  FIG. 4 is a view showing the 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 in the photographing screen 135A. This display is performed by the liquid crystal display 132 superimposing a mark representing the position of eleven focus detection areas on the object image on the focusing plate 131. Then, the photographer operates the operation unit 150 to select a desired focus detection area AFP, or automatically selects a focus detection area AFP according to 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 micro lens 161a corresponding to a predetermined range (indicated by a dotted line in FIG. 4) centered on the focus detection area AFP7. Read the output from.

  Here, it is necessary to calculate the pupil center position of the photographing lens 210 in order to secure the above-described conjugate relationship of the pupil. This is because the microlens array 161 and the light receiving element array 162 are usually manufactured separately and then assembled, so it is uncertain which position of the photoelectric conversion element 162a corresponds to which micro lens 161a. It is. Further, 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 seen from the micro lens 161a changes. Therefore, the position of the photoelectric conversion element 162a which is in a conjugate relationship with the pupil center position of the photographing lens 210 is determined to be the center of the microlens 161a in the microlens optical axis center determination unit 163C.

  The position of the photoelectric conversion element 162a corresponding to the center of each micro lens 161a is obtained from the position (image height) of the micro lens 161a with respect to the optical axis L1 of the photographing lens 210 and the distance from the micro lens 161a to the pupil of the photographing lens 210. be able to. For example, in a lens barrel in which the distance from the micro lens 161a to the pupil of the photographing lens 210 is known, the data group of the center position of each micro lens 161a is stored in advance in the memory of the lens control unit 250 Based on the distance to the pupil of the photographing lens 210, the current center position of the photographing 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 of the microlenses 161a or around 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 painted in the same drawing is extracted.

  If the distance to the pupil of the imaging lens 210 is unknown, the distance to the pupil may be taken as an infinite position, and the central position determined only from the positional relationship between the microlens 161a and the photoelectric conversion element 162a may be used. .

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

  Assuming that 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 f-number is the focal length at the effective aperture (pixel spacing). Since it is a divided value, as shown in FIG. 3E, F = 14 when selected with a pixel spacing of 2 pixels, F = 7 when selected with a pixel spacing of 4 pixels as shown in FIG. 3F, As shown in 3G, each optical information of F = 4.7 is obtained when the pixel spacing of 6 pixels is selected, and F = 3.5 when the pixel spacing of 8 pixels is selected as shown in FIG. 3H. be able to. Although FIG. 4 is omitted, when selected at a pixel interval of 10 pixels, optical information of F = 2.8 can be obtained. The relationship between the pixel interval and the aperture value is shown in FIG.

  And since each photoelectric conversion element 162a is conjugate with the corresponding position of the pupil of the photographing lens 210, the optical information obtained by this is information that has a correlation with the focal position when the aperture value F is changed. Become.

  The calculated aperture value selection unit 163D illustrated in FIG. 2 has pixel intervals for determining the base 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. Are output to the pixel pattern table 163E.

  The upper limit of the pixel interval is determined by the minimum aperture value that the micro lens 161a can take, but 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 micro lens 161a. Can. That is, when the open 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 the pixel interval of each step up to the vicinity of the open aperture value accordingly. Output this in stages.

  When the pixel interval is determined based on the open aperture value data of the imaging lens 210, the pixel selection unit 163F extracts a pixel selection pattern representing the aperture value-interval relationship from the pixel pattern table 163E. The pixel pattern extracted here can be selected by selecting two photoelectric conversion elements 162a at a predetermined interval, but it is also possible to select a plurality of photoelectric conversion elements 162a orthogonal to the base line based on conditions such as the amount of incident light. . The examples shown in FIGS. 3E to 3H show examples in which three photoelectric conversion elements 162a are selected.

  Actual photoelectric conversion elements 162a are specified from the optical axis center position determined by the microlens optical axis center determination unit 163C and the pixel pattern extracted by the pixel pattern table 163E.

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

  The image shift amount calculation unit 163H executes detection of the focal position by the pupil division phase difference method. That is, the image shift amount calculation unit 163H performs the image shift calculation using the first signal sequence {aj} and the second signal sequence {bj} to calculate the defocus amount. The first signal train {aj} and the second signal train {bj} are aj (j = 1, 2,... N) and bj (j = 1) from positions symmetrical with respect to the center along the base line in the micro lens 161a. , 2,... N), the focal position, that is, the focal shift amount from the planned focal plane, is the parallax of the pupil position optically conjugate to the target photoelectric conversion element 162a. appear. That is, the one-dimensional curve represented by the data string cut out from the N micro lenses 161a is shifted by the amount of parallax between the first signal string {aj} and the second signal string {bj}. The focus detection calculation in the image shift amount calculation unit 163H is to obtain the phase shift amount between the two data strings on the premise that almost the same image is projected on the two data strings.

  This calculation calculates the difference between the first signal sequence {aj} and the second signal sequence {bj} while shifting the relative base numbers of the two number sequences, and obtains the amount of shift at which this becomes the smallest. First, from the first signal sequence {aj} and the second signal sequence {bj}, the correlation operation value Dk of a pair of images (signal sequences) is determined by the following equation.

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

  FIG. 6 is a graph for explaining the method of calculating the amount of deviation x in the focus detection device of this embodiment. As shown in FIG. 6, the minimum Dk is Di, and the adjacent Dk is Di + 1 and Di-1. First, choose the larger of Di + 1 and Di-1. Since Di-1 is larger in the example shown in the figure, Di-1 is selected. Next, let L1 be a straight line connecting the selected Di-1 and Di. Then, assuming that the inclination of the straight line L1 is α, the straight line passing through Di + 1 whose inclination is -α is L2 and the intersection point of the straight lines L1 and L2 is obtained, the x of the intersection point becomes the above-mentioned deviation x.

  When the focal point position for one pixel interval (for example, 2 pixels), that is, the aperture value (for example, F = 14) is obtained in the image shift amount calculation unit 163H, similarly for the next pixel interval (for example, 4 pixels, F = 7) And the focal point position at that f-number is determined. This process is executed for all the pixel intervals shown in FIG. 5, and the obtained data result of each focus position is stored in the storage unit 163J.

  For example, as shown in FIG. 5, an example in which the results for the pixel intervals of 2, 4, 6, 8, and 10 pixels are stored for each aperture value F is shown by black circles in FIG. This represents the spherical aberration of the photographing lens 210 by discrete values. Then, the correction unit 163K reads the actual aperture value f at the time of shooting, and from the table shown in FIG. 7 stored in the storage unit 163J, using the interpolation or extrapolation of the measurement values in the vicinity, the photographing lens The image shift amount due to the spherical aberration of 210 is corrected to an optimal focus position that makes it zero.

  Here, since the f-number f is obtained by dividing the focal length by the effective aperture, correction is performed using a reciprocal 1 / f of the f-number f with a linear pixel dimension-effective aperture. That is, in the correction table, the reciprocal 1 / f of the corresponding aperture value f is associated with the measurement value.

Assuming that the reciprocal 1 / f of the aperture value f of this correction table is xi and the measured value is yi, the correction table is represented by {xi, yi} (where xi <xi _{+ 1} ). Then, when the photographing aperture value f is read, xi, xi ≦ ff ≦ xi _{+ 1,} is obtained from the reciprocal ff = 1 / f by interpolation. If there is no value satisfying xi ≦ ff ≦ xi _{+ 1} , there is a value to be obtained outside the correction table, so xi = x0 or xi = x _n−1 (n is the final value of the correction table). Find xi by interpolation. In this manner, the distribution coefficient s is obtained from the following equation 2, and the focal position Y corresponding to the imaging aperture value can be obtained by proportionally calculating the measurement values in the vicinity from this.

[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 and calculates the lens drive amount Δd. It outputs to the lens drive control unit 165.

  The lens drive control unit 165 sends a drive command to the lens drive motor 230 while capturing 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 the present embodiment, the focal position corresponding to a plurality of pixel intervals, that is, the aperture value is calculated from the image of the focus detection sensor 162, and is used to calculate the luminous flux corresponding to the actual imaging aperture value. Since the focal position is determined, the focal point can be detected with high accuracy even if the imaging lens has different focal position variations due to spherical aberration.

Other Embodiments
In the embodiment described above, the micro lens array 161 in which the circular micro lenses 161a shown in FIG. 3B are squarely arranged is used, but it is also possible to use the micro lens array 161 in which regular hexagonal macro lenses 161a are densely arranged in a honeycomb shape. .

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

  The focus detection optical system 161 of this example is a micro lens array in which a plurality of micro lenses 161a are densely arranged in a two-dimensional manner (in a honeycomb shape) as shown in FIG. 8A. Similarly to the above, it is disposed in the vicinity of the position P1 which is the planned focal plane of the photographing lens 210.

  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 is similar to that shown in FIG. It is disposed substantially at the focal position of the microlens array 161.

  The micro lens 161a of this example has a shape obtained by cutting out a circular micro lens having a lens surface shape indicated by an alternate long and short dash line in a regular hexagon, and has the same function as the circular micro lens. The microlens array 161 is formed by arranging such regular hexagonal macro lenses 161 a in a honeycomb shape.

  By arranging the regular hexagonal micro lenses 161a in a honeycomb shape as described above, it is possible to avoid the dead zone of focus detection between the lenses, which occurs when circular micro lenses are arranged. The upper, lower, left, and right directions in the figure coincide with the upper, lower, left, and right directions of the imaging screen imaged by the imaging element 110.

  On the other hand, in the photoelectric conversion element array 162 disposed behind the microlens array 161, square photoelectric conversion elements 162a are squarely arranged as in the above embodiment. One photoelectric conversion element 162a is formed smaller than one microlens 161a, and 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. There is.

  Since the microlens array 161 of this example configured in this way is a regular hexagonal microlens 161a arranged in a honeycomb shape as shown in FIG. 8A, the image data array also becomes a honeycomb shape.

  Also in this embodiment, since the focal position corresponding to a plurality of pixel intervals, that is, the aperture value is calculated from the image of the focus detection sensor 162, and the focal position of the luminous flux corresponding to the actual imaging aperture value is obtained using this. Even in the case of an imaging lens with different focal position variations due to spherical aberration, the focal point can be detected accurately.

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

  In the embodiment described above, the focus detection sensor 162 which is a two-dimensional sensor is provided separately from the imaging device 110, but instead of this, the microlens 161a and the photoelectric conversion device 162a are similar to a part of the imaging device 110. It is possible to provide a configuration, and focus detection can be performed by the above-described procedure.

  The present invention may be applied to hybrid AF in which the AF of the pupil division phase difference detection method and the AF of the contrast method (mountain climbing AF) based on the image signal obtained by the imaging element 110 are used in combination.

1 single-lens reflex digital camera 100 camera body 110 imaging device 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: microlens optical axis center determination unit 163D: calculation aperture value selection unit 163E: pixel pattern table 163F: pixel selection unit 163G: target detection row extraction unit 163H: image shift amount calculation Unit 163J: Storage unit 163K: Correction unit 164: Lens driving amount calculation unit 200: Lens barrel 210: Shooting lens 211: Focus lens

Claims (2)

A microlens array in which a plurality of microlenses are two-dimensionally arranged;
A light receiving element having a plurality of light receiving portions arranged in a two-dimensional shape provided for each of the micro lenses, and receiving a light flux from the imaging lens through the micro lenses;
Of the plurality of light receiving units of the micro lens, the driving amount of the focus lens of the photographing lens is determined by signals output from a pair of light receiving units that are symmetrical with respect to the light receiving unit having a conjugate relationship with the pupil center position of the photographing lens. A driving amount computing unit that computes
Equipped with
The position of the light receiving unit in a conjugate relationship with the pupil center position of the photographing lens is the two-dimensional position of the microlens from the optical axis of the photographing lens, and the pupil of the photographing lens and the microlens An imaging apparatus, which changes the distance between the pair of light receiving units according to the aperture value of the photographing lens, depending on the distance. In the imaging device according to claim 1,
The image shift amount by a pair of light passing through different pupil regions of the shooting lens calculated by the signals output from the pair of light receiving units is corrected by the image shift amount by spherical aberration of the shooting 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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