JP2011007867A - Focus detecting means and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detecting device, detecting a focus with high accuracy regardless of an object.SOLUTION: The focus detecting device includes: a light receiving element array having a microlens array in which a plurality of microlenses are two-dimensionally arranged and a plurality of light receiving elements provided for each microlens, to receive a light flux from an optical system through the microlens array; an image generating part for generating a pan-focus image based on output signals output from the light receiving elements of the light receiving element array; a detecting part for detecting a specified object in the pan-focus image; and a focus detecting part which performs processing according to the object detected by the detecting part for the output signals output from the light receiving elements of the light receiving element array to detect the focus state of the optical system.

Description

  The present invention relates to a focus detection device and a camera.

  Using a light receiving element array having a plurality of light receiving elements for each microlens of the microlens array in which a plurality of microlenses are arranged, light beams from different partial areas of the pupil of the optical system are passed through each microlens array. A focus detection device that receives light by each of a plurality of light receiving elements is known. In Patent Document 1, among at least three signal sequences corresponding to an image of a light beam transmitted through at least three partial regions, a shift amount of two signal sequences is obtained for each of a plurality of sets of partial regions and added. Focus detection can be performed without generating false focus on a subject having a pattern.

JP 2008-304808 A

  However, in addition to a subject having a periodic pattern, for example, in the case of a low-contrast subject, a subject competing for perspective, or a subject with low brightness, false focusing may occur. The focus detection apparatus disclosed in Patent Document 1 has a problem that false focusing may occur in the case of a low-contrast subject, a subject competing for perspective, or a low-luminance subject.

  As described above, conventionally, there is a problem that the focus detection accuracy is lowered depending on the focus detection target.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a focus detection device with high accuracy and a camera including the focus detection device regardless of the object.

  The present invention has been made to solve the above-described problems, and includes a microlens array in which a plurality of microlenses are arranged two-dimensionally, and a plurality of light receiving elements provided for each of the microlenses. A light receiving element array that receives a light beam from an optical system via the microlens array, an image generation unit that generates a pan focus image based on an output signal output from the light receiving element of the light receiving element array, and Among the pan-focus images, a detection unit that detects a specific target, and an output signal output from the light receiving element of the light receiving element array is processed according to the target detected by the detection unit, And a focus detection unit that detects a focus state of the optical system.

  According to this invention, focus detection accuracy can be performed with high accuracy regardless of the object.

It is a block diagram which shows the structure of the digital single-lens reflex camera provided with the focus detection apparatus by one Embodiment of this invention. It is a block diagram which shows the detailed structure of the focus detection sensor of FIG. 1 by this embodiment. It is a block diagram which shows the structure of the focus detection sensor of FIG. 1 and FIG. 2 by this embodiment. It is explanatory drawing which shows the image pick-up element used when producing | generating a pan focus image in the focus detection sensor of FIGS. 1-3 by this embodiment. It is a 1st flowchart which shows operation | movement of the digital single-lens reflex camera by this embodiment. FIG. 6 is a second flowchart showing an example of detailed operation of the AF parameter changing process in the first flowchart of FIG. 5 according to the present embodiment. It is explanatory drawing which shows the example of the output data from the focus detection sensor by this embodiment. It is explanatory drawing which shows an example of the correlation calculation and shift amount by this embodiment. It is explanatory drawing which shows an example at the time of dividing | segmenting the several light receiving element which the focus detection sensor by this embodiment has into several blocks.

  FIG. 1 is a cross-sectional view illustrating a configuration of a digital single-lens reflex camera (hereinafter referred to as a camera) including a focus detection apparatus 100 according to an embodiment. Note that illustrations and descriptions of general devices and apparatuses of the camera other than the devices and apparatuses related to the focus detection apparatus 100 and the imaging apparatus of the present invention are omitted. In a camera according to an embodiment, a lens barrel 20 is attached to the camera body 1, and the lens barrel 20 can be replaced with various photographing lenses. In this embodiment, an interchangeable lens camera will be described as an example. However, the present invention is not limited to the interchangeable lens camera, and can be applied to a fixed lens camera.

  The lens barrel 20 includes a zooming lens 21, a focusing lens 22, an aperture 24, a lens and an aperture driving actuator 25, a lens memory 26, and the like. In FIG. 1, the zooming lens 21 and the focusing lens 22 are represented by a single photographing lens 23. The zooming lens 21 is a lens that is driven in the optical axis direction by an actuator 25 to change the focal length of the photographing lens 23. The focusing lens 22 is a lens that is driven in the optical axis direction by an actuator 25 to adjust the focus of the photographing lens 23. The diaphragm 24 is driven by an actuator 25 to change the diaphragm opening diameter. The lens memory 26 stores information on the lens barrel 20 and the photographing lens 23 such as the open F value of the photographing lens 23, the exit pupil position (distance from the surface equivalent to the imaging surface to the exit pupil) PO, and the focal length. ing.

  The camera body 1 includes an imaging element 2, a shutter 3, a focus detection sensor (light receiving element array) 5, an image generation unit 61, a pattern matching processing unit 62, an AF parameter setting unit 63, a focus detection calculation unit 64, and a lens drive amount calculation unit. 65, control circuit 7, drive circuit 8, quick return mirror 9, sub mirror 10, finder screen 11, transmissive liquid crystal display 12, pentaprism 13, photometric lens 14, photometric sensor 15, eyepiece 16, and operation member 17 It has. As will be described later, the focus detection sensor 5 includes, for example, a focus detection optical system (microlens array) 40 and a photoelectric conversion array element (a plurality of light receiving elements) 50.

  The imaging device 2 is composed of a CCD, a CMOS, or the like, and converts the subject image formed by the imaging lens 23 in the lens barrel 20 into an electrical signal and outputs it. The shutter 3 is opened only when the shutter button (not shown) is fully pressed (at the time of shutter release) for the exposure calculation result or the shutter time manually set by the photographer to expose the image sensor 2.

  The focus detection sensor 5, the image generation unit 61, the pattern matching processing unit 62, the AF parameter setting unit 63, and the focus detection calculation unit 64 constitute the focus detection device 100, and the focus of the photographing lens (imaging optical system) 23. A defocus amount indicating an adjustment state is detected. Details of the focus detection apparatus 100 will be described later.

  The lens drive amount calculation unit 65 calculates the lens drive amount up to the focus position of the focus lens based on the defocus amount detected by the focus detection calculation unit 64 of the focus detection apparatus 100.

  The control circuit 7 includes a microcomputer (not shown) and peripheral components such as a memory, and performs sequence control such as photometry, focus detection, and shooting, and calculation control such as exposure calculation. Further, the control circuit 7 drives the actuator 25 via the drive circuit 8 based on the lens drive amount calculated by the lens drive amount calculation unit 65 to drive the focusing lens 22 in focus.

  The drive circuit 8 controls driving of a lens and an aperture driving actuator 25 provided in the lens barrel 20. The photometric sensor 15 divides the photographing screen into a plurality of areas and outputs a photometric signal corresponding to the luminance of each area.

  An operation member 17 that is operated by the photographer is disposed on the camera body 1. The operation member 17 includes a release half-push switch that is turned on when the shutter button is half-pressed, a release full-push switch that is turned on when the shutter button is fully pushed. When the release half-press switch is pressed, a signal indicating the start of AF is input to the control circuit 7. When the release full-press switch is pressed, a signal indicating the start of imaging is input to the control circuit 7.

  Except during photographing, the quick return mirror 9 and the sub mirror 10 are placed in the photographing optical path as shown in FIG. At this time, part of the light from the subject that has passed through the photographing lens 23 is reflected by the quick return mirror 9 and guided to the finder screen 11 to form a subject image on the screen 11. The transmissive liquid crystal display 12 displays a focus detection area mark superimposed on a subject image on the screen 11 and displays information related to shooting such as a shutter speed, an aperture value, and the number of shots outside the subject image.

  The subject image on the screen 11 is guided to the photographer's eyes via the pentaprism 13 and the eyepiece lens 16 and is also guided to the photometric sensor 15 via the pentaprism 13 and the photometric lens 14. The control circuit 7 performs an exposure calculation based on a photometric signal for each photometric area output from the photometric sensor 15, and calculates a shutter speed and an aperture value corresponding to the luminance of the subject. When the manual exposure shooting mode is set, the shutter speed and aperture value set by the photographer operating the operation member 17 are used.

  On the other hand, another part of the light from the subject that has passed through the photographing lens 23 passes through the quick return mirror 9 and is reflected by the sub-mirror 10, and is guided to the focus detection sensor 5. The focus detection apparatus 100 described above detects a defocus amount indicating the focus adjustment state of the photographing lens (imaging optical system) 23 based on another part of the light from the subject.

  At the time of shooting, the quick return mirror 9 and the sub mirror 10 are retracted (mirror-up) from the shooting optical path, and the light flux from the subject that has passed through the shooting lens 23 when the shutter 3 is opened is guided to the imaging device 2. A subject image formed on the imaging surface is captured.

  Next, details of the focus detection apparatus 100 will be described. First, an example of the configuration of the focus detection sensor 5 among the configurations of the focus detection device 100 will be described with reference to FIGS. 2 to 4.

  FIG. 2 is a block diagram showing an example of a detailed configuration of the focus detection sensor 5. As shown in FIG. 2, the focus detection sensor 5 includes a focus detection optical system 40 and a photoelectric conversion array element 50. . In FIG. 2, the focus detection optical system 40 is a microlens array in which a plurality of microlenses 41 are two-dimensionally arranged, and is equivalent to the surface on which the photographing lens 23 is focused, that is, the imaging surface of the image sensor 2. Arranged near the surface. In FIG. 2, although the number of microlenses is small, actual microlenses are arranged at a pitch of 100 microns or less, so if the microlens array is, for example, 5 mm square, the microlens The number of is very large.

  The photoelectric conversion array element 50 is a light receiving element array 51 in which a plurality of light receiving elements (photoelectric conversion elements) are two-dimensionally arranged, and is disposed behind the focus detection optical system 40 with respect to the quick return mirror 9. 2 and FIGS. 3 and 4 to be described later, a light receiving element array 51 in which a total of 25 light receiving elements of 5 rows and 5 columns for each microlens 41 are arranged in a square array will be described as an example. The number of light receiving elements for each microlens is not limited to the number of this embodiment. Moreover, it is good also as a light receiving element array which arranged the several light receiving element in the two-dimensional form, without arrange | positioning several light receiving elements collectively for every microlens.

  FIG. 3 shows a plurality of light receiving elements arranged in a two-dimensional form of the photoelectric conversion array element 50. Each of the plurality of light receiving elements is a photoelectric conversion element. A plurality of light receiving elements arranged in a two-dimensional manner, and among the plurality of light receiving elements corresponding to the microlens, two rows of light receiving elements are used as line sensors like the light receiving elements shown in black in FIG. The amount of focus shift can be detected (see FIG. 7 described later). That is, the amount of focus shift can be detected by the phase difference detection method using the two rows of line sensors. Of the light receiving elements corresponding to a plurality of microlenses, two rows of light receiving elements may be used as line sensors in the light receiving elements corresponding to some of the microlenses, as shown in FIG.

Of the plurality of light receiving elements arranged in a two-dimensional array of photoelectric conversion array elements 50, the light is output only from the central light receiving element corresponding to the microlens 41 (see the black light receiving element in the center of FIG. 4). When the signals are combined, a pan-focus image can be generated. This pan-focus image is an image that is clearly focused from the near view to the distant view of the camera. That is, the pan focus image is an image having a deep depth of field.
Here, the case where only the center light receiving element corresponding to the microlens 41 is used has been described. However, even if the output signals output from the light receiving elements corresponding to the center part of the microlens are combined, the panning is similarly performed. A focus image can be generated.

  Next, in the configuration of the focus detection apparatus 100, the image generation unit 61, the pattern matching processing unit 62, the AF parameter setting unit 63, and the focus detection calculation unit 64 will be described.

  The image generation unit 61 generates a pan focus image based on an output signal output from the light receiving elements of the light receiving element array included in the focus detection sensor 5. For example, as described above, the image generation unit 61 is a plurality of light receiving elements arranged in a two-dimensional manner of the focus detection sensor 5, and among the plurality of light receiving elements corresponding to the microlens 41, the center of the microlens. A pan focus image is generated by synthesizing output signals output from the light receiving elements corresponding to the sections (see FIG. 4).

  The pattern matching processing unit 62 detects a specific target from the pan focus image generated by the image generation unit 61. For example, the pattern matching processing unit 62 detects a target corresponding to at least one of the contrast, luminance, periodicity, and distance difference of the image included in the pan focus image as a specific target.

  The AF parameter setting unit 63 sets a parameter for detecting the focus state of the optical system in the focus detection calculation unit 64 based on the specific target detected by the pattern matching processing unit 62. As will be described later, this parameter includes setting of a threshold value of a contrast value that is an index of detection accuracy when performing correlation calculation, and setting of a gain when controlling the focus detection sensor 5. Thus, the focus detection calculation unit 64 detects the focus state of the optical system by performing processing corresponding to the object detected by the pattern matching processing unit 62 on the output signal output from the light receiving elements of the light receiving element array. Can do.

  The focus detection calculation unit 64 calculates a defocus amount indicating the focus adjustment state of the photographing lens 23 based on the focus detection signal from the focus detection sensor 5. The focus detection calculation unit 64 calculates the defocus amount based on the parameters set by the AF parameter setting unit 63 when calculating the defocus amount.

Next, the focusing operation by the camera of the present embodiment will be described with reference to FIG.
First, in step S101, the image generation unit 61 generates a pan focus image by image composition processing. In order to generate a pan focus image, the image generation unit 61 generates an image using a central light receiving element corresponding to the microlens 41 as described with reference to FIG. By generating a pan-focus image in this way, unlike the case of a normal camera, in step S102 described later, the pattern matching processing unit 62 performs pan-focus, which is an image in which a subject from a foreground to a distant view is almost in focus. Based on the image, scene analysis such as pattern matching can be performed. In this step S101, when imaging is performed using the focus detection sensor 5, the gain of the focus detection sensor 5 may be adjusted in accordance with the amount of light.

  In step S102, the pattern matching processing unit 62 determines a subject from the generated pan focus image by scene analysis processing such as pattern matching. The pattern matching here is a technique for extracting features from a certain input image and discriminating a subject from template information. The information used as the template is a plurality of predetermined information that the focus detection calculation unit 64 is not good at.

  Next, in step S103, the AF parameter setting unit 63 performs processing to change or set the AF parameter for the focus detection calculation unit 64 based on the subject determined in step S102. As a process for changing or setting the AF parameter for the focus detection calculation unit 64, the AF parameter setting unit 63 is, for example, a sensor for causing the focus detection calculation unit 64 to perform an AF process corresponding to the determined subject. Change settings such as a threshold used for calculating the control method and the defocus amount. The processing in step S103 will be described later with reference to FIG.

  Next, in step S104, the control circuit 7 determines whether or not the switch SW1 is turned on. Here, the switch SW1 is a release half-push switch included in the operation member 17 described above. If it is determined in step S104 that the switch SW1 is not turned on, the control circuit 7 repeats the processing from step S101.

  On the other hand, if it is determined in step S104 that the switch SW1 has been turned on, the control circuit 7 causes the focus detection sensor 5 to accumulate charges in step S105. In this step S105, a part of the processing is controlled based on the recognized subject, that is, reflecting the setting obtained from step S103.

  FIG. 7 shows an example of output data from the focus detection sensor 5. In FIG. 7, the horizontal axis indicates an identification number for identifying a pixel constituting the line sensor, and the vertical axis indicates an output value from the pixel constituting the line sensor indicated by the identification number. For example, FIG. 7A shows the case of the first line sensor among the two rows of line sensors shown in FIG. For example, FIG. 7B shows a case of the second line sensor among the two rows of line sensors shown in FIG. Here, δ corresponds to the image shift amount calculated by the defocus calculation (correlation calculation) in step S107. Based on the image shift amount δ, the focus detection calculating unit 64 calculates a defocus amount in step S107 described later.

  In step S106, the focus detection calculation unit 64 reads a signal from the sensor array of the focus detection sensor 5 that has performed accumulation control.

  Next, in step S107, the focus detection calculation unit 64 calculates the defocus amount based on the signal read in step S106. Depending on the scene recognized in step S102 described above, a part of the processing in calculating the defocus amount may be executed by reflecting the threshold set in step S103 described above.

  FIG. 8 shows an example of the correlation calculation (calculation performed when calculating the defocus amount) and the shift amount in step S107. In FIG. 8, the horizontal axis represents the shift amount L, and the vertical axis represents the correlation amount (reliability) C [L] corresponding to the shift amount. In step S107 described above, the focus detection calculation unit 64 calculates the defocus amount so that the correlation amount C [L] is minimized (or minimized).

  The correlation amount C [L] is calculated as follows, for example. For example, let {a (i)} and {b (i)} be signal sequences output from the two line sensor described in FIG. Here, i is an identification number indicating a pixel between the first end and the second end of the line sensor. The correlation amount C [L] calculated from the two rows of line sensors is expressed by the following (Equation 1).

  C [L] = Σ | a (i) −b (j) | (Formula 1)

  In (Equation 1), L is the shift amount and j−i = L, and Σ is the summation operation in the pixels constituting the line sensor, that is, the above-described first end and second end of the line sensor. Represents the sum operation between and.

  Next, in step S108, the focus detection calculation unit 64 determines whether or not focus detection is possible from the defocus amount calculated in step S107. This determination is made based on the contrast value or reliability of the correlation calculation result.

  If it is determined in step S108 that focus detection is possible, in the next step S109, the lens drive amount calculation unit 65 calculates the lens drive amount up to the focus position of the focus lens based on the calculated defocus amount. .

  Next, in step S110, based on the lens drive amount calculated in step S109, the control circuit 7 drives the actuator 25 via the drive circuit 8 to drive the focusing lens 22 in focus.

  On the other hand, if it is determined in step S108 that focus detection is not possible, the control circuit 7 determines whether or not the focusing lens 22 is being driven in the next step S111. This determination is performed when the focusing lens 22 has not yet started moving, and has already moved the focusing lens 22, but when the subject is lost on the way, based on the defocus amount that could be detected earlier, This is a determination for continuing the lens driving of the focusing lens 22.

  If it is determined in step S111 that the focusing lens 22 is being driven, the control circuit 7 advances the process to step S110 described above. On the other hand, if it is determined in step S111 that the focusing lens 22 is not being driven, it is determined in step S108 that the defocus amount cannot be detected, and the lens is not yet driven in step S111 described above. Thus, in the next step S112, the control circuit 7 performs a scanning operation and searches for the focal position.

  Subsequent to step S110 or step S112 described above, in the next step S113, the control circuit 7 determines whether or not the focus lens has reached the in-focus position.

  If it is determined in step S113 that the focusing lens 22 has not reached the in-focus position, the control circuit 7 repeats the processing from step S104 described above. On the other hand, if it is determined in step S113 that the focusing lens 22 has reached the in-focus position, the control circuit 7 ends the in-focus processing.

  Thereafter, when the release full-press switch included in the operation member 17 is pressed, a signal indicating the start of imaging is input to the control circuit 7. In response to the input of the signal indicating the start of imaging, the control circuit 7 retracts the quick return mirror 9 and the sub mirror 10 from the imaging optical path, and images the subject image by the imaging element 2.

  Next, an example of processing by the AF parameter setting unit 63 in step S103 of FIG. 5 will be described using FIG.

  First, in step S201, the AF parameter setting unit 63 determines whether or not the subject at the focus area position obtained by the pattern matching process in step S102 of FIG. 5 has low contrast. This determination of whether or not the contrast is low refers to, for example, determining whether or not the contrast of the subject at the focus area position is lower than a predetermined contrast.

  If it is determined in step S201 that the contrast is not low, in step S202, the AF parameter setting unit 63 determines that the subject at the focus area position obtained by the pattern matching process in step S102 is a periodic pattern. It is determined whether or not. The determination as to whether or not the pattern is a periodic pattern is made, for example, when the subject at the focus area position obtained by the pattern matching process in step S102 in FIG. 5 matches a pattern that is determined in advance to determine the periodic pattern. It may be determined whether or not to perform, or may be determined based on the result of Fourier transform of the subject at the focus area position. This Fourier transform is, for example, a two-dimensional Fourier transform. In order to increase the calculation speed, a two-dimensional fast Fourier transform may be used as the two-dimensional Fourier transform.

  If it is determined in step 202 that the pattern is not a periodic pattern, in step S203, the AF parameter setting unit 63 determines that the subject at the focus area position obtained by the pattern matching process in step S102 in FIG. It is determined whether or not the brightness. The determination as to whether or not the luminance is low is made by determining whether or not the luminance of the subject at the focus area position is lower than a predetermined luminance, for example.

If it is determined in step S203 that the brightness is not low, in step S204, the AF parameter setting unit 63 determines that the subject at the focus area position obtained by the pattern matching process in step S102 in FIG. Determine if there is a conflict. For example, a pattern for determining whether or not a near view and a distant view compete is determined in advance, and the subject at the focus area position This is done by determining whether or not it corresponds to the pattern.

  On the other hand, if it is determined in step S201 described above that the contrast is low, then in step S205, the AF parameter setting unit 63 is at the focus area position obtained by the pattern matching process in step S102 of FIG. It is determined whether or not the subject has low contrast. This determination of whether or not the contrast is low is the same as the determination of whether or not the contrast is low in step S203 described above.

If it is determined in step S205 that the contrast is not low, then in step S209, the AF parameter setting unit 63 performs first low contrast setting for the focus detection calculation unit 64.
As the first setting for low contrast, the AF parameter setting unit 63 performs false focusing on the focus detection calculation unit 64 while, for example, increasing a contrast value threshold value that is an index of detection accuracy when performing correlation calculation. Make settings such as increasing reliability for prevention.
Specifically, the AF parameter setting unit 63 lowers the threshold for detecting the contrast E with respect to the focus detection calculation unit 64 so that the contrast E shown in FIG. 8 can be detected even when the contrast is low. Set. Further, in order to make detection as easy as possible even in the case of low contrast, a setting is made such that the gain setting when controlling the focus detection sensor 5 is controlled with a low gain setting with a high S / N. Note that the gain setting here is lower than the low-brightness setting in step S207, which will be described later, and the second low-contrast setting in step S210.

On the other hand, if it is determined in this step S205 that the contrast is low, then in step S210, the AF parameter setting unit 63 performs the second low contrast setting for the focus detection calculation unit 64.
As this second setting for low contrast, the AF parameter setting unit 63 performs false focusing on the focus detection calculation unit 64, for example, while increasing a contrast value threshold value that is an index of detection accuracy when performing correlation calculation. Make settings such as increasing reliability for prevention.
Specifically, the AF parameter setting unit 63 lowers the threshold for detecting the contrast E with respect to the focus detection calculation unit 64 so that the contrast E shown in FIG. 8 can be detected even when the contrast is low. Set. Further, in order to make detection as easy as possible even in the case of low contrast, settings are made such as controlling the gain setting when controlling the focus detection sensor 5 with a high gain setting with a high S / N. Note that the gain setting here is lower than the low-brightness setting in step S207, which will be described later, and higher than the second low-contrast setting in step S210 described above.

  On the other hand, if it is determined in step 202 described above that the pattern is a periodic pattern, the AF parameter setting unit 63 performs setting for the periodic pattern in the focus detection calculation unit 64 in step S206. As the periodic pattern setting, for example, a setting for performing processing as shown in the following document 1 may be performed. As another setting, in the case of a strong periodic signal or the like, a setting may be made to narrow the calculation range of the correlation calculation.

  Reference 1 “Japanese Patent Laid-Open No. 2008-304808”

On the other hand, if it is determined in step 203 described above that the luminance is low, then in step S207, the AF parameter setting unit 63 performs setting for low luminance in the focus detection calculation unit 64. As the low-brightness setting, like the first low-contrast setting in step S209 or the second low-contrast setting in step S210 described above, a contrast value or reliability serving as an index of detection accuracy when performing correlation calculation Set to lower.
Further, in order to make it possible to detect low contrast as much as possible, the gain setting when controlling the focus detection sensor 5 is set to a setting with a high S / N and a gain as high as possible. In this way, by setting a high gain while maintaining a high S / N, the peak value of the charge output can be increased as much as possible as shown in FIG. Note that the gain setting here is higher than the low luminance setting in step S207 and the second low contrast setting in step S210, and may be a maximum gain. Further, the optimum balance between the gain and the S / N may be different depending on the focus detection sensor 5.

  On the other hand, if it is determined in step 204 described above that there is a perspective conflict, then in step S208, the AF parameter setting unit 63 makes a perspective conflict setting for the focus detection calculation unit 64. For example, when shooting an animal in a fold, if you want to focus on the animal, that is, if there is no subject in front and there is a conflict, The sensor in the area is divided into a plurality of blocks so that the defocus amounts of competing subjects are calculated. FIG. 9 shows an example in which a plurality of light receiving elements included in the focus detection sensor 5 are divided into a plurality of blocks.

  For example, as shown in FIG. 9, as indicated by reference signs A1, A2, and A3, the first detection state in which the plurality of light receiving elements of the focus detection sensor 5 are divided into a plurality of blocks is As indicated by B1 and B2, the plurality of light receiving elements of the focus detection sensor 5 are changed to a second divided state that is divided into a plurality of blocks so as to be different from the first divided state. In addition, with respect to the two rows of line sensors shown in FIG. 3, the division state of each line sensor is changed as shown in FIG.

  On the other hand, if it is determined in step 204 that there is no perspective conflict, the AF parameter setting unit 63 performs, for example, a predetermined standard setting for the focus detection calculation unit 64. This is because a standard setting is sufficient because it is not a subject that is not good at autofocus.

  As described above with reference to FIG. 6, according to the process by the AF parameter setting unit 63 in step S <b> 103 in FIG. 5, the subject at the focus area position obtained by the pattern matching process in step S <b> 102 in FIG. When it is low contrast and not low brightness (equivalent to the case of step S209), when it is low contrast and low brightness (equivalent to the case of step S210), when it is not low contrast but low brightness (in the case of step S207) The focus detection calculation unit 64 has a periodic pattern (e.g., in the case of step S206) or a conflict in perspective (e.g., in case of step S209). Settings appropriate for each case are made. Therefore, the focus detection calculation unit 64 can normally detect the focus state of the optical system in any case.

  Note that the determination processing in steps S201 to S205 in FIG. 6 described above has no priority and may be in any order. Further, not only the subject that is not good at the subject but also a human face or the like may be used according to a pattern matching template and an algorithm suitable for it may be used.

  It should be noted that focus detection is performed for any combination of conditions such as low contrast, low brightness, periodic pattern, and whether or not they are competing for perspective. Parameters set in the calculation unit 64 may be stored in advance in a storage unit included in the camera. The AF parameter setting unit 63 may read out parameters corresponding to arbitrarily combined conditions from the storage unit and set the read parameters in the focus detection calculation unit 64.

  In the description of the present embodiment described above, the pan focus image (see FIG. 4) generated using the central light receiving element corresponding to the microlens 41 is the focal length or shooting distance of the optical system. It has been described that the image is taken in focus from the near view to the distant view without depending on it. In the case of a wide-angle system with a focal length of the optical system shorter than that of a standard lens, such as 35 mm, and a deep depth of field, from a near view to a distant view without depending on the focal length or shooting distance of the optical system. The image may be in focus.

  However, in the case of a telephoto system in which the focal length of the optical system is longer than that of a standard lens, for example, 200 mm, and the depth of field is shallow, the range in which the image is focused from near view to distant view is the optical system. May depend on the focal length and shooting distance. For example, there is a possibility that a pan-focus image (see FIG. 4) generated by using a central light receiving element corresponding to the microlens 41 is captured in a range of several meters before and after the shooting distance. is there.

  In such a case, based on the focal length of the optical system, for example, the photographing distance is changed in order, and the center light receiving element corresponding to the microlens 41 is used as described in step S101 in FIG. Pan-focus images from which images are generated may be taken in order. In step S102 of FIG. 5, the pattern matching processing unit 62 determines a subject from the generated pan focus image by scene analysis processing such as pattern matching based on the pan focus images sequentially captured. Similarly, in step S103 in FIG. 5, the AF parameter setting unit 63 performs focus detection on the AF processing corresponding to the determined subject based on the subject determined in step S102 based on the pan focus images sequentially captured. The sensor control method to be performed by the calculation unit 64 and the setting of the threshold value used when calculating the defocus amount are changed.

  By doing this, even if the pan focus image generated using the central light receiving element corresponding to the microlens 41 is not in focus from the near view to the distant view, the shooting distance In any case described with reference to FIG. 6, appropriate parameters are set in the focus detection calculation unit 64 by capturing the pan focus image by changing the above. Therefore, since the focus detection calculation unit 64 is set appropriately for each case, the focus state of the optical system can be normally detected.

  Note that the pan-focus image generated using the central light-receiving element corresponding to the microlens 41 is more than the image obtained when the optical system is simply picked up with a diaphragm so as to increase the depth of field. Deep depth of field. For this reason, the pattern matching processing unit 62 performs a scene analysis process such as pattern matching on the basis of the pan focus image generated using the central light receiving element corresponding to the microlens 41, from the generated pan focus image. This makes it easier to identify the subject.

  In the description of the above embodiment, the focus detection sensor 5 and the image sensor 2 have different configurations, and the case where an image is captured by the image sensor 2 has been described. That is, the image sensor 2 different from the focus detection sensor 5 has been described as capturing an image by the light receiving system. However, the focus detection sensor 5 and the image sensor 2 may be integrated, and the focus detection sensor 5 as the image sensor 2 may capture an image by the light receiving system. That is, the focus detection sensor 5 can be used not only as a light receiving sensor used for autofocus but also as a light receiving sensor used for imaging.

  In this case, the quick return mirror 9 and the sub mirror 10 may be omitted, and the focus detection sensor 5 integrated with the image sensor 2 may be disposed at the position of the image sensor 2. In addition, a finder screen 11, a transmissive liquid crystal display 12, a pentaprism 13, and an eyepiece lens are displayed so that an image captured by the focus detection sensor 5 is displayed on a display unit such as a liquid crystal display device provided in the camera. It is also possible to omit 16.

  The image generation unit 61 may determine the number of light receiving elements corresponding to the central portion of the microlens 41 according to the focal length of the optical system. For example, in the description of the above-described embodiment, as described with reference to FIG. 4, the case where the image generation unit 61 generates a pan focus image based on one light receiving element in the center of the micro lens 41 has been described. However, for example, the image generation unit 61 may generate a pan focus image based on the nine light receiving elements in the center of the microlens 41. For example, the control circuit 7 may set the number of the light receiving elements in the image generation unit 61 according to the focal length of the optical system.

  The image generating unit 61 has been described as generating a pan-focus image using the central light receiving element corresponding to the microlens 41, but the image generating unit 61 is used as the central light receiving element corresponding to the microlens 41. The pan focus image may be generated by combining output signals output from some of the plurality of light receiving elements. For example, when the photometric sensor 15 has a plurality of focus positions, from some of the plurality of light receiving elements so as to correspond to the focus position selected from the plurality of focus positions. A pan focus image may be generated by synthesizing output signals to be output. In this way, the focus state of the optical system can be detected based on the pan focus image corresponding to the focus position selected from the plurality of focus positions. That is, focus detection areas are set at a plurality of positions in the shooting screen, and the focus detection sensor 5 can output a focus detection signal indicating the focus adjustment state of the shooting lens 23 for each focus detection area.

  Note that each processing unit of the image generation unit 61, the pattern matching processing unit 62, the AF parameter setting unit 63, the focus detection calculation unit 64, the lens driving amount calculation unit 65, or the control circuit 7 in FIG. In addition, each processing unit may be configured by a memory and a CPU (central processing unit), and a program for realizing the function of each processing unit may be loaded into the memory and executed. The function may be realized by.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 5 ... Focus detection sensor, 40 ... Focus detection optical system, 41 ... Micro lens, 50 ... Photoelectric conversion array element, 51 ... Light receiving element array, 61 ... Image generation part, 62 ... Pattern matching process part, 63 ... AF parameter setting part 64 ... focus detection calculation unit, 65 ... lens drive amount calculation unit, 100 ... focus detection device

Claims (8)

It has a microlens array in which a plurality of microlenses are arranged two-dimensionally and a plurality of light receiving elements provided for each of the microlenses, and receives a light beam from an optical system via the microlens array. A light receiving element array;
An image generator that generates a pan-focus image based on an output signal output from the light receiving element of the light receiving element array;
A detection unit for detecting a specific target in the pan focus image;
A focus detection unit that detects a focus state of the optical system by performing processing according to the target detected by the detection unit on an output signal output from the light receiving element of the light receiving element array;
A focus detection apparatus comprising: The focus detection apparatus according to claim 1,
The image generation unit
Among the plurality of light receiving elements, the pan focus image is generated by synthesizing an output signal output from a light receiving element corresponding to a central portion of the microlens.
A focus detection apparatus. The focus detection device according to claim 1 or 2,
The image generation unit
Determining the number of light receiving elements corresponding to the center of the microlens according to the focal length of the optical system;
A focus detection apparatus. The focus detection apparatus according to any one of claims 1 to 3,
The image generation unit
Combining the output signals output from some of the plurality of light receiving elements to generate the pan focus image;
A focus detection apparatus. The focus detection apparatus according to any one of claims 1 to 4,
The detector is
Detecting at least one of contrast, brightness, periodicity, and distance difference of an image included in the pan-focus image as the specific target;
A focus detection apparatus. The focus detection device according to any one of claims 1 to 5,
A camera comprising: The camera according to claim 6,
An imaging unit that captures an image by the optical system;
A camera comprising: The camera according to claim 7,
The imaging unit
Taking an image by the optical system based on an output signal from the light receiving element array,
A camera characterized by that.

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