Imaging device and control method of the same

Abstract

To obtain a correct one defocus amount from a plurality of defocus amounts different from each other in an image height, a focus detection direction and the like.SOLUTION: An imaging device 120 has: focus detection means 129 of performing focus detection within an imaging screen, and acquiring a plurality of first defocus amounts different from each other in at least one of an image height, a focus detection direction and an angle of a subject; and control means 125 of performing focus control. The control means is configured to: acquire first information indicative of a relationship between the defocus amount in a specific position of the imaging screen and the focus amount in response to the at least one in an area other than the specific position; acquire a plurality of second defocus amounts, using the plurality of first defocus amounts and the first information; and acquire a third defocus amount to be used in the focus control from the plurality of second defocus amounts.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an imaging device capable of autofocus (AF).

Background Art

[0002] As an imaging device that performs focus detection by a phase difference detection method using an imaging element such as a CMOS sensor, Patent Document 1 discloses an imaging device that performs focus detection in a plurality of different focus detection directions. In this imaging device, one defocus amount used for AF is obtained by comparing the defocus amounts obtained in a plurality of focus detection directions. Patent Document 2 also discloses a method of performing AF using a focus sensitivity according to an image height when different defocus amounts occur according to the image height.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When determining one defocus amount used for AF by comparing the defocus amounts obtained in a plurality of focus detection directions as in the imaging device of Patent Document 1, if a difference in defocus amount according to the image height as in Patent Document 2 is included, correct comparison etc. cannot be performed. As a result, an accurate single defocus amount cannot be obtained, and high-precision AF cannot be performed.

[0005] The present invention provides an imaging device and a control method thereof that can obtain an accurate single defocus amount from a plurality of defocus amounts in which the image height, the focus detection direction, etc. are different from each other.

Means for Solving the Problems

[0006] As one aspect of the present invention, an imaging device includes focus detection means for performing focus detection within an imaging screen to obtain a plurality of first defocus amounts in which at least one of the image height, the focus detection direction, and the subject angle is different from each other, and control means for performing focus control. The control means obtains first information indicating the relationship between the defocus amount at a specific position on the imaging screen and the defocus amount corresponding to at least one of the regions other than the specific position, obtains a plurality of second defocus amounts using the plurality of first defocus amounts and the first information, and obtains a third defocus amount to be used for focus control from the plurality of second defocus amounts.

[0007] Further, as another aspect of the present invention, a control method for an imaging device includes a step of obtaining a plurality of first defocus amounts in which at least one of the image height, the focus detection direction, and the subject angle is different from each other, a step of obtaining first information indicating the relationship between the defocus amount at a specific position on the imaging screen and the defocus amount corresponding to at least one of the regions other than the specific position, a step of obtaining a plurality of second defocus amounts using the plurality of first defocus amounts and the first information, and a step of obtaining a third defocus amount to be used for focus control from the plurality of second defocus amounts. A program for causing a computer of the imaging device to execute the processing according to the above control method also constitutes another aspect of the present invention.

Effect of the Invention

[0008] According to the present invention, an accurate one defocus amount can be obtained from a plurality of defocus amounts in which at least one of the image height, the focus detection direction, and the subject angle is different.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

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Figure 10

Figure 11

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] FIG. 1 shows the configuration of an imaging system 10 including an imaging device (hereinafter referred to as a camera body) 120 according to Embodiment 1. A lens unit (interchangeable lens) 100 is detachably attached to a camera body 120 as a digital camera via a mount M shown by a dotted line in the figure. Note that the imaging device may have an imaging optical system integrally provided. The imaging device is not limited to a digital camera, and may be other imaging devices such as a video camera.

[0012] The lens unit 100 includes a first lens group 101, a diaphragm 102, a second lens group 103, and a focus lens group (hereinafter simply referred to as a focus lens) 104 as a focus element, and a drive / control system. The imaging optical system takes in light from a subject and forms a subject image.

[0013] The first lens group 101 is disposed closest to the object side and is held movably in the optical axis direction in which the optical axis OA extends. The aperture 102 adjusts the amount of light by changing its aperture diameter and functions as a shutter for exposure time adjustment during still image shooting. The aperture 102 and the second lens group 103 are integrally movable in the optical axis direction and perform zooming by moving in conjunction with the first lens group 101. The focus lens 104 is movable in the optical axis direction to perform focusing. Focus control (AF) is performed by controlling the position of the focus lens 104 according to the focus detection result described later.

[0014] The drive / control system includes a zoom actuator 111, an aperture actuator 112, a focus actuator 113, a zoom drive circuit 114, an aperture drive circuit 115, a focus drive circuit 116, a lens MPU 117, and a lens memory 118. The zoom drive circuit 114 drives the zoom actuator 111 to move the first lens group 101 and the third lens group 103 in the optical axis direction during zooming. The aperture drive circuit 115 drives the aperture actuator 112 to operate the aperture 102 and perform aperture operation and shutter operation.

[0015] The focus drive circuit 116 drives the focus actuator 113 to move the focus lens 104 in the optical axis direction during focusing. The focus drive circuit 116 functions as a position detection unit that detects the current position of the focus lens 104 (hereinafter referred to as the focus position) through the focus actuator 113.

[0016] The lens MPU 117 is a computer that executes operations and processing related to the lens unit 100, and controls the zoom drive circuit 114, the aperture drive circuit 115, and the focus drive circuit 116. Also, the lens MPU 117 is communicably connected to the camera MPU 125 in the camera body 120 through the communication terminal of the mount M, and exchanges commands and data. For example, the lens MPU 117 notifies the camera MPU 125 of lens information in response to a request from the camera MPU 125. This lens information includes information such as the focus position, the position and diameter in the optical axis direction of the exit pupil of the imaging optical system, and the position and diameter in the optical axis direction of the lens frame that limits the light beam of the exit pupil.

[0017] Also, the lens MPU 117 controls the zoom drive circuit 114, the aperture drive circuit 115, and the focus drive circuit 116 in response to a request from the camera MPU 125. The lens memory 118 stores the optical information necessary for AF. The camera MPU 125 controls the operation of the lens unit 100 by executing programs stored in the built-in non-volatile memory and the lens memory 118.

[0018] The camera body 120 includes an optical low-pass filter 121, an imaging device 122, an image processing circuit 124, and a drive / control system. The optical low-pass filter 121 is provided to reduce false colors and moiré.

[0019] The imaging device 122 is composed of a CMOS sensor and its peripheral circuits, photoelectrically converts the subject image (optical image) formed by the imaging optical system, and outputs an imaging signal and a pair of focus detection signals (two-image signals). A plurality of imaging pixels of m pixels in the horizontal direction and n pixels in the vertical direction (m and n are integers of 2 or more) are arranged in the imaging device 122. Each imaging pixel includes a pair of focus detection pixels as described later, and has a pupil division function capable of phase difference detection type focus detection.

[0020] The drive / control system includes an imaging element drive circuit 123, an image processing circuit 124, a camera MPU 125, a display 126, an operation switch (SW) 127, a memory 128, a phase difference AF unit 129, a flicker detection unit 130, an AE unit 131, and a white balance (WB) adjustment unit 132. The imaging element drive circuit 123 controls charge accumulation and signal readout in the imaging element 122, and A / D-converts the imaging signal and the pair of focus detection signals output from the imaging element 122, then outputs them to the image processing unit 124 and the camera MPU 125. The image processing circuit 124 performs image processing such as γ conversion, color interpolation processing, and compression encoding processing on the digital imaging signal from the imaging element drive circuit 123 to generate image data.

[0021] The camera MPU 125 as control means is a computer that executes operations and processing related to the camera body 120, and controls the imaging element drive circuit 123, the image processing circuit 124, the display 126, the phase difference AF unit 129, the flicker detection unit 130, the AE unit 131, and the WB adjustment unit 132. Also, the camera MPU 125 is communicably connected to the lens MPU 117 through the communication terminal of the mount M, and exchanges commands and data with the lens MPU 117. For example, the camera MPU 125 requests lens information and optical information from the lens MPU 117, or requests driving of the lenses 101, 104 and the aperture 102. The camera MPU 125 receives the lens information and optical information transmitted from the lens MPU 117.

[0022] The camera MPU 125 incorporates a ROM 125a that stores various programs, a RAM 125b that stores variables, and an EEPROM 125c that stores various parameters. The camera MPU 125 executes various processes including the AF process described later according to the programs stored in the ROM 125a. The camera MPU 125 generates two-image data from the pair of digital focus detection signals from the imaging element drive circuit 123 and outputs it to the phase difference AF unit 129.

[0023] The display 126 is composed of an LCD or the like, and displays information regarding the imaging mode, a preview image before imaging, a confirmation image after imaging, the focus state, and the like. The operation SW 127 includes a power switch, a release (imaging instruction) switch, a zoom switch, an imaging mode selection switch, and the like. The memory 128 is a removable flash memory with respect to the camera body 120, and records the recorded images obtained by imaging.

[0024] The phase difference AF unit 129 as the focus detection means performs focus detection using the two-image data generated by the camera MPU 125. The imaging device 122 photoelectrically converts a pair of optical images formed by light fluxes passing through different pairs of pupil regions among the exit pupils of the imaging optical system, and outputs a pair of focus detection signals. The phase difference AF unit 129 performs a correlation operation on the two-image data generated by the camera MPU 125 from the pair of focus detection signals, calculates the amount of image shift which is the phase difference between them, and calculates (acquires) the defocus amount as information regarding focus from the amount of image shift. The camera MPU 125 calculates the driving amount of the focus lens 104 based on the defocus amount calculated by the phase difference AF unit 129, and transmits a focus control command including the driving amount to the lens MPU 117.

[0025] Thus, in this embodiment, imaging plane phase difference AF using the output of the imaging device 122 is performed without using a dedicated AF sensor for focus detection. In this embodiment, the phase difference AF unit 129 has an acquisition unit 129a that acquires two-image data and a calculation unit 129b that calculates the defocus amount. Note that at least one of the acquisition unit 129a and the calculation unit 129b may be provided in the camera MPU 125.

[0026] The flicker detection unit 130 detects flicker from the image data for flicker detection obtained from the image processing circuit 124. The camera MPU 125 performs control to adjust the exposure amount so that the influence of the detected flicker is reduced.

[0027] The AE unit 131 performs exposure control (AE) by performing photometry using the image data for AE obtained from the image processing circuit 124. Specifically, the AE unit 131 acquires the luminance information of the image data for AE, and calculates the aperture value, shutter speed (shutter seconds), and ISO sensitivity as imaging conditions from the difference between the exposure amount obtained from this luminance information and a preset exposure amount. Then, AE is performed by controlling the aperture value, shutter speed, and ISO sensitivity to be the calculated values.

[0028] The WB adjustment unit 132 calculates the WB of the image data for WB adjustment obtained from the image processing circuit 124, and performs WB adjustment by adjusting the color weights of RGB according to the difference between the calculated WB and a preset appropriate WB.

[0029] Furthermore, the camera MPU 125 can perform a process of detecting a subject such as a person's face in the image data obtained from the image processing circuit 124. The camera MPU 125 can select an image height range for performing phase difference AF, AE, and WB adjustment according to the position and size of the detected subject.

[0030] (Regarding the imaging device 122) FIG. 2 shows the pixel array on the imaging surface of the imaging device 122 as a 2D CMOS sensor in this embodiment. Here, the array of imaging pixels is shown in the range of 4 columns × 4 rows. One pixel group 200 including 2 columns × 2 rows of imaging pixels includes a pixel 200R having a spectral sensitivity of R (red) arranged at the upper left, pixels 200Ga and 200Gb having a spectral sensitivity of G (green) arranged at the upper right and lower left, and a pixel 200B having a spectral sensitivity of B (blue) arranged at the lower right. Each imaging pixel is composed of a first focus detection pixel 201 and a second focus detection pixel 202. In pixels 200R, 200Ga, and 200B, the first focus detection pixel 201 and the second focus detection pixel 202 are arranged horizontally, and in pixel 200Gb, the first focus detection pixel 201 and the second focus detection pixel 202 are arranged vertically.

[0031] FIG. 3(a) shows pixel 200Ga as viewed from the incident side (+z side) of the imaging device 122, and FIG. 3(b) shows the pixel structure of pixel 200Ga in FIG. 3(a) as viewed from the -y side along the a-a cross section. In pixel 200Ga, a microlens 305 for condensing incident light is formed on the incident side, and photoelectric conversion units 301 and 302 that are divided into two in the x direction are formed. The photoelectric conversion units 301 and 302 respectively correspond to the first focus detection pixel 201 and the second focus detection pixel 202.

[0032] The photoelectric conversion units 301 and 302 may be pin-structure photodiodes having an intrinsic layer sandwiched between a p-type layer and an n-type layer, or may be pn-junction photodiodes with the intrinsic layer omitted. A color filter 306 is formed between the microlens 305 and the photoelectric conversion units 301 and 302. The spectral transmittance of the color filter may be changed for each focus detection pixel, or the color filter may be omitted.

[0033] The two light beams incident on pixel 200Ga from the pair of pupil regions are each condensed by the microlens 305, spectrally split by the color filter 306, and then received by the photoelectric conversion units 301 and 302. In each photoelectric conversion unit, electrons and holes are generated in pairs according to the amount of received light, separated in the depletion layer, and then the negatively charged electrons are accumulated in the n-type layer. On the other hand, the holes are discharged outside the imaging device 122 through the p-type layer connected to a constant voltage source (not shown). The electrons accumulated in the n-type layer of each photoelectric conversion unit are transferred to a capacitance unit (FD) via a transfer gate and converted into a voltage signal.

[0034] FIG. 4 shows the relationship between the pixel structure shown in FIGS. 3(a) and (b) and pupil division. Below FIG. 4, the pixel structure when the a-a cross section in FIG. 3(a) is viewed from the +y side is shown, and above, the pupil plane of the pupil distance DS is shown. Note that in FIG. 4, in order to correspond to the coordinate axes of the pupil plane, the x-axis and y-axis of the pixel structure are inverted with respect to FIG. 3(b). The pupil plane corresponds to the incident pupil position of the imaging element 122. In this embodiment, by offsetting (shrinking) the position of the microlens in each pixel from the center of the imaging element 122, the incident pupils in each pixel overlap each other to form the incident pupil of one imaging element 122. The pupil distance DS is the distance between the pupil plane and the imaging plane, and is referred to as the sensor pupil distance in the following description.

[0035] As shown in FIG. 4, the first pupil region 501 of the first focus detection pixel 201 is generally in a conjugate relationship with the light receiving surface of the photoelectric conversion unit 301 whose center of gravity is eccentric in the -x direction by the microlens. The first pupil region 501 is a pupil region through which the light beam that can be received by the first focus detection pixel 201 passes. The center of gravity of the first pupil region 501 is eccentric to the +X side on the pupil plane. Also, the second pupil region 502 of the second focus detection pixel 202 is generally in a conjugate relationship with the light receiving surface of the photoelectric conversion unit 302 whose center of gravity is eccentric in the +x direction by the microlens. The second pupil region 502 is a pupil region through which the light beam that can be received by the second focus detection pixel 202 passes. The center of gravity of the second pupil region 502 is eccentric to the -X side on the pupil plane. The pupil region 500 is a pupil region through which the light beam that can be received by the entire pixel 200G combining the photoelectric conversion unit 301 and the photoelectric conversion unit 302 (the first focus detection pixel 201 and the second focus detection pixel 202) passes.

[0036] As shown in FIG. 5, the light beams that enter the imaging optical system from the subject (the vertical line on the left side in the figure) and pass through the first pupil region 501 and the second pupil region 502 respectively are incident on each imaging pixel at different angles and received by the photoelectric conversion units 301 and 302. The pixels 200R, 200Ga, and 200B perform pupil division in the horizontal direction, and the pixel 200Gb performs pupil division in the vertical direction. The imaging pixels each having a first focus detection pixel and a second focus detection pixel receive the light beams passing through the first pupil region 501 and the second pupil region 502. A pair of focus detection signals is generated by synthesizing the output signals of the first focus detection pixel 201 and the second focus detection pixel 202 in a plurality of imaging pixels. Also, an imaging signal with a resolution of the effective pixel number N (= m × n) is generated by adding the output signals of the first focus detection pixel 201 and the second focus detection pixel 202 in a plurality of imaging pixels. Note that one of the pair of focus detection signals may be subtracted from the imaging signal to generate the other focus detection signal.

[0037] In this embodiment, the first and second focus detection pixels are provided for each of all the imaging pixels of the image sensor 122. However, two imaging pixels may be used as the first and second focus detection pixels, or the first and second focus detection pixels may be provided for some of the imaging pixels.

[0038] (Regarding the relationship between the defocus amount and the image shift amount) FIG. 6 shows the relationship between the defocus amount and the image shift amount of two-image data. 800 indicates the imaging surface of the image sensor 122, and the pupil surface of the image sensor 122 is divided into two parts, the first pupil region 501 and the second pupil region 502. The defocus amount d is defined such that the magnitude of the distance from the imaging position of the subject image (hereinafter referred to as the image position) to the imaging surface 800 is |d|. The pre-pin state where the image position is located on the subject side of the imaging surface is given a negative sign (d < 0), and the post-pin state where the image position is located on the side opposite to the subject with respect to the imaging surface 800 is given a positive sign (d > 0). The in-focus state where the image position is located on the imaging surface 800 is d = 0.

[0039] In FIG. 6, the subject 801 indicates a focused state (d = 0), and the subject 802 indicates a front defocus state (d < 0). The front defocus state (d < 0) and the rear defocus state (d > 0) are combined into a defocus state (|d| > 0).

[0040] In the front defocus state, among the light beams from the subject 802, the light beams that have passed through the first pupil region 501 and the second pupil region 502 respectively spread in widths Γ1 and Γ2 centered on the centroid positions G1 and G2 of the light beams after being focused once, and form a blurred optical image on the imaging surface 800. These blurred images are received by the first focus detection pixel 201 and the second focus detection pixel 202 at each imaging pixel on the imaging surface 800, and thereby the first focus detection signal and the second focus detection signal as a pair of focus detection signals are generated. The first focus detection signal and the second focus detection signal are respectively recorded as blurred images in which the subject 802 spreads in the blur widths Γ1 and Γ2 at the centroid positions G1 and G2 on the imaging surface 800. The blur widths Γ1 and Γ2 increase generally in proportion to the increase in the magnitude |d| of the defocus amount d. Similarly, the magnitude |p| of the image shift amount p (= the difference G1 - G2 in the centroid positions of the light beams) between the first focus detection signal and the second focus detection signal also increases generally in proportion to the increase in the magnitude |d| of the defocus amount d. Even in the rear defocus state (d > 0), the image shift direction between the first focus detection signal and the second focus detection signal is opposite to that in the front defocus state, but the principle is the same.

[0041] In this embodiment, the centroid difference in the respective incident angle distributions in the first pupil region 501 and the second pupil region 502 is referred to as the baseline length. The relationship between the defocus amount d and the image shift amount p on the imaging surface 800 is generally a similar relationship to the relationship of the baseline length with respect to the sensor pupil distance. Since the magnitude of the image shift amount between the first focus detection signal and the second focus detection signal increases as the magnitude of the defocus amount d increases, the phase difference AF unit 129 converts the image shift amount into the defocus amount according to the conversion coefficient calculated based on the baseline length from this relationship.

[0042] In the following description, calculating the defocus amount using a pair of focus detection signals from focus detection pixels that divide the pupil in the horizontal direction (lateral direction), such as the prime 200Ga, is referred to as horizontal-eye focus detection (first detection). Also, calculating the defocus amount using a pair of focus detection signals from focus detection pixels that divide the pupil in the vertical direction (longitudinal direction), such as the pixel 200b, is referred to as vertical-eye focus detection (second detection).

[0043] (Regarding focus sensitivity) Focus sensitivity is an index indicating the relationship between the unit movement amount of the focus lens 104 and the change amount of the image position, which is the imaging position of the optical image. In this embodiment, it indicates the ratio of the change amount of the image position to the unit movement amount of the focus lens 104. For example, if the change amount of the image position when the focus lens 104 is moved by 1 mm, which is its unit movement amount, is 1 mm, the focus sensitivity is 1, and if the change amount of the image position is 2 mm, the focus sensitivity is 2. However, as the focus sensitivity, other values, for example, the reciprocal of the above ratio, may be used.

[0044] Also, when moving the focus lens 104 based on a monotonically increasing function, the change amount of the image position with respect to a specific unit amount can be used as the focus sensitivity. For example, when driving the focus lens 104 along the shape of a cam provided on a cam ring in conjunction with the rotation of the cam ring, the change amount of the image position with respect to the unit rotation angle of the cam ring, which is equivalent to the unit movement amount of the focus lens, may be used as the focus sensitivity.

[0045] When the defocus amount is d and the focus sensitivity is S, generally, the driving amount X of the focus lens 104 is X = d / S (1) obtained by

[0046] Also, when the focus actuator 113 is an actuator that is pulse-driven, such as a stepping motor, the number of pulses P of the focus drive pulse supplied by the focus drive unit 109 to the focus actuator 113 is obtained by the following formula (2).

[0047] P = X / m = d / (mS) (2) In Equation (2), m is the amount of movement of the focus lens 104 per one focus drive pulse.

[0048] The phase difference AF unit 129, the camera MPU 125, and the lens MPU 117 perform focus detection by the phase difference detection method as follows. The camera MPU 125 acquires in advance from the lens MPU 117 the current position of the focus lens 104, the focus sensitivity S, and the amount of movement m of the focus lens 105 per one focus drive pulse.

[0049] As described above, the phase difference AF unit 129 calculates the amount of image shift of the pair of focus detection signals (two-image data) acquired from the imaging device 122, and calculates (detects) the defocus amount from the amount of image shift. The camera MPU 125 calculates the number of pulses P of the focus drive pulse using Equation (2) described above, and transmits a focus drive command including this number of pulses P to the lens MPU 117.

[0050] The lens MPU 117 controls the focus drive circuit 116 so that the focus drive pulse of the number of pulses P received is supplied to the focus actuator 113. As a result, the focus lens 104 moves by the drive amount X (= d / S), and a focused state of the imaging optical system is obtained.

[0051] However, the interchangeable lens 100 of the present embodiment has an imaging optical system in which the defocus amount d(h) changes according to the image height h. Therefore, the camera MPU 125 calculates the drive amount X of the focus lens 104 using the defocus amount d(h) corresponding to the image height h and the focus sensitivity S(h) corresponding to the image height h. That is, the drive amount X of the focus lens 105 is obtained by the following Equation (3). Further, the number of pulses P of the focus drive pulse is obtained by the following Equation (4).

[0052] X = d(h) / S(h) (3) P = X / m = d(h) / (mS(h)) (4) (Regarding the defocus amount ratio) Figures 7(a) and 7(b) show examples of the ratio of the defocus amount for each image height h (hereinafter referred to as the defocus amount ratio) when the defocus amount d(h) at the center (image height h = 0) within the imaging screen of the imaging optical system is set to 1. Figure 7(a) shows the defocus amount ratio in horizontal focus detection (hereinafter also referred to as the horizontal defocus amount ratio), and Figure 7(b) shows the defocus amount ratio in vertical focus detection (hereinafter also referred to as the vertical defocus amount ratio). Here, the defocus amount ratio in the first quadrant of the imaging surface when the imaging element 122 is a full-size sensor is shown. The image heights 0, 2, 4, ······, 18 shown in the bottom row of the figure indicate the horizontal image height [mm], and the image heights 0, 2, 4, ······, 12 shown in the leftmost column indicate the vertical image height [mm].

[0053] When performing horizontal focus detection at an image height other than the center of the imaging screen, the defocus amount d(h) is calculated using the horizontal defocus amount ratio corresponding to the image height in Figure 7(a). For example, in Figure 7(a), the horizontal defocus amount ratio at the image height (horizontal 16 mm, vertical 8 mm) is 3.337. Also, when performing vertical focus detection at an image height other than the center of the imaging screen, the defocus amount d(h) is calculated using the vertical defocus amount ratio corresponding to the image height in Figure 7(b). For example, in Figure 7(b), the vertical defocus amount ratio at the image height (horizontal 16 mm, vertical 8 mm) is 2.1.

[0054] As can be seen from these figures, in this imaging optical system, the defocus amount ratio increases from the center to the peripheral side. Also, the defocus amount ratio is different in the focus detection directions (horizontal and vertical).

[0055] Note that regardless of horizontal focus detection or vertical focus detection, the defocus amount ratio for the same image height may be switched according to the angle (edge angle) of the subject detected from the image data obtained from the image processing circuit 124. This method makes it possible to correct the defocus amount difference corresponding to the image height with higher accuracy.

[0056] Fig. 11(a) shows an example of the edge angle of a subject. The edge angle of the subject is the angle of the edge portion of the subject with respect to the X-axis, which is the horizontal axis on the imaging screen that is the XY plane. The angle of the edge portion of the subject shown as the shaded portion in Fig. 11(a) is θ. The method for detecting this edge angle will be described with reference to Fig. 11(b). Note that the detection method in Fig. 11(b) is merely an example, and other detection methods may be used.

[0057] In Fig. 11(b), the edge angle θ, which is the gradient direction of the coordinates (x, y) of the pixels included in the edge portion of the subject, is calculated by the following equation (5).

[0058] θ(x,y)=arctan(V(x,y) / H,x,y)) (5) The coordinates (x, y) of the pixel are orthogonal coordinates given with the horizontal right direction and the vertical upward direction as the positive directions respectively. H(x,y) represents the horizontal contrast intensity of a specific frequency at the coordinates (x,y), and is given by the following equation (6). P(α,β) represents the luminance value at the coordinates (α,β) of the pixel.

[0059] H(x,y)=P(x+1,y)―P(x-1,y) (6) Similarly, V(x,y) represents the vertical contrast intensity at the coordinates P(x,y), and is given by the following equation (7).

[0060] V(x,y)=P(x,y+1)-P(x,y-1) (7) Here, the detection filter for calculating the contrast intensities of H(x,y) and V(x,y) is set to (1, 0, -1). However, it can be changed to anything that can detect the frequency components of the subject.

[0061] The case of θ = 90° corresponds to the defocus amount ratio in the horizontal-eye focus detection shown in Fig. 7(a), and the case of θ = 0° corresponds to the defocus amount ratio in the vertical-eye focus detection shown in Fig. 7(b). Note that a data table of the defocus amount ratios shown in Figs. 7(a) and 7(b) corresponding to the edge angle of the subject may be held, and the defocus amount ratio corresponding to the edge angle of the subject detected for each image height may be read from the data table and used.

[0062] As described above, the defocus amount ratio indicates the relationship between the defocus amount at the center, which is a specific position on the imaging screen, and the defocus amount corresponding to at least one of the image height, the focus detection direction, and the angle of the subject in the peripheral region other than the specific position. Note that the specific position on the imaging screen does not necessarily have to be the center, and any position that is easy to use as a reference for the defocus amount ratio may be used.

[0063] (Problems in determining one focus detection result from a plurality of focus detection results) In this embodiment, horizontal-eye focus detection and vertical-eye focus detection are performed. However, the focus detection result used to drive the focus lens 104 is the result of one of the horizontal-eye focus detection and the vertical-eye focus detection. Further, even when a plurality of defocus amounts with different image heights are obtained, the defocus amount obtained at a specific image height is used to drive the focus lens 104 in AF.

[0064] As described with reference to FIGS. 7(a) and 7(b), in horizontal-eye focus detection and vertical-eye focus detection, the defocus amount ratio is different even at the same image height. For example, at an image height of (0, 12), the horizontal-eye defocus amount ratio is 1.421 times that of the center, while the vertical-eye defocus amount ratio is 2.484 times the defocus amount. In this case, the defocus amount obtained by vertical-eye focus detection is always larger than the defocus amount obtained by horizontal-eye focus detection. For example, in such a situation, if a nearest-side priority algorithm is applied and the focus detection result used to drive the focus lens 104 is selected, only the defocus amount obtained by vertical-eye focus detection will be selected. Also, for example, when calculating the average of the focus detection results, average values of significantly different defocus amounts will be obtained. Thus, it is inconvenient to perform AF by determining one focus detection result from a plurality of focus detection results with different defocus amount ratios.

[0065] Furthermore, FIG. 8(a) shows an example of determining one defocus amount (hereinafter referred to as the used defocus amount) to be used for AF using a defmap, which is a map showing the defocus amounts at a plurality of image heights for a person as the subject in focus detection. The defmap shows the defocus amounts obtained, for example, at 28 focus detection regions (coordinates (1, 1) to (7, 4)) of 4 horizontal and 7 vertical set on the face and body of the person as shown in FIG. 8(b).

[0066] FIG. 8(c) shows the defocus amount (e.g., horizontal focus detection result) in the above 28 focus detection regions by a histogram. The horizontal axis shows the defocus amount ranges def range x+1, x+2, x+3, x+4, x+5, and the vertical axis shows the number of focus detection regions in which the defocus amount is included in each def range. In this figure, when x = 0, the number of focus detection regions within the defocus amount range centered on 1Fδ (e.g., 0.5Fδ or more and less than 1.5Fδ) is 1, and the number of focus detection regions within the defocus amount ranges centered on 2Fδ and 4Fδ is 7 each. Also, the number of focus detection regions within the defocus amount range centered on 3Fδ is 9, and the number of focus detection regions in the defocus amount range centered on 5Fδ is 7. F is the aperture value, and δ is the allowable confusion circle diameter.

[0067] In FIG. 8(c), the defocus amount range of the maximum number of focus detection regions (mode value) is x+3. Therefore, the defocus amount for the person shown in FIG. 8(a) is likely to be in the range of x+3. Accordingly, the average value of the defocus amount included in the range of x+3, etc. is determined as the used defocus amount.

[0068] In this way, by determining the used defocus amount using a histogram, effects such as preventing foreground-background competition and making it difficult for the focus detection region that obtains the final defocus amount to be influenced by the variation in the defocus amount for each focus detection region can be expected.

[0069] However, when using such a histogram, the defocus amount rate according to the image height described above becomes a problem.

[0070] For example, the focus detection regions (1, 4) shown in FIGS. 8(a) and 8(b) are the focus detection regions with the highest image height, and the defocus amount rate is large. Conversely, the focus detection region (6, 1) is the focus detection region with the image height closest to the center, and the defocus amount rate is small. Such differences in the defocus amount rate between different image heights vary depending on the type of imaging optical system. Taking the example of FIG. 7(a), the focus detection region (1, 4) corresponds to the image height (16, 10) in FIG. 7(a), and the defocus amount rate is 3.165. Also, the focus detection region (6, 1) corresponds to the image height (6, 0) in FIG. 7(a), and the defocus amount rate is 1.321. Also, for the same image height (14, 0) in FIGS. 7(a) and 7(b) corresponding to the same focus detection region (6, 4), the horizontal defocus amount rate is 2.931 and the vertical defocus amount rate is 1.588, which are different from each other.

[0071] The defocus amount at each image height is calculated as a value multiplied by the defocus amount rate. As a result, as shown in FIG. 9(a), the original histogram shown in FIG. 8(c) cannot be obtained, and the defocus amount determined from the maximum number of focus detection regions in the histogram being reduced to one may be different from the original value, or the defocus amounts for the maximum number of focus detection regions may be different between the horizontal and vertical directions.

[0072] FIG. 9(a) is a histogram for horizontal focus detection, and FIG. 9(b) is a histogram for vertical focus detection. In order to further enhance the effect of suppressing the influence of the above-mentioned far - near competition and the variation in the defocus amount for each focus detection region, it is possible to obtain the histogram of FIG. 9(c) by combining the histograms of FIG. 9(a) and FIG. 9(b) and perform focus detection. However, also in this case, if the defocus amount rate corresponding to the image height is not considered, the defocus amounts will be different between the horizontal and vertical directions, resulting in the occurrence of def ranges for multiple maximum numbers of focus detection regions or the def range for the maximum number of focus detection regions being in an incorrect range.

[0073] Therefore, in this embodiment, an appropriate defocus amount for AF is determined from a plurality of defocus amounts with different defocus amount rates.

[0074] The flowchart of FIG. 10 shows the AF process (control method) that the camera MPU 125 executes according to the program in this embodiment.

[0075] When imaging preparation is instructed by a user operation of the release switch on the operation switch 127, the camera MPU 125 starts AF in step S100.

[0076] Next, in step S101, the camera MPU 125 acquires information (first information) on defocus amount ratios in which at least one of the image height, focus detection direction, and subject angle stored in the lens memory 118 from the lens MPU 117 is different from each other. The camera MPU 125 also acquires information (second information) on focus sensitivity for each image height stored in the lens memory 118. At this time, the information on the defocus amount ratio and the focus sensitivity may be acquired in the form of table data, or the information on the coefficients of the functions for calculating the defocus amount ratio and the focus sensitivity may be acquired. That is, it is only necessary to be able to acquire information regarding the defocus amount ratio and the focus sensitivity.

[0077] Also, information on the defocus amount ratio for only some quadrants as shown in FIGS. 7(a) and 7(b) may be acquired, or information on the defocus amount ratio for all quadrants may be acquired. Further, information on the defocus amount ratio and the focus sensitivity of interchangeable lenses of a plurality of models may be stored in the memory 128 in advance, and the information corresponding to the model information (such as lens ID) acquired from the lens MPU 117 may be read from the memory 128 for acquisition.

[0078] Next, in step S102, the camera MPU 125 causes the phase difference AF unit 129 to acquire the defocus amount (first defocus amount) in one or a plurality of focus detection regions.

[0079] Next, in step S103, the camera MPU 125 determines whether to use a plurality of defocus amounts in which at least one of the image height, the focus detection direction, and the subject angle is different from each other in the current AF. If so, the process of step S104 is performed. If not, the process of step S105 is performed. If the used defocus amount is determined using the above-described defocus amount histogram, or if the average value of a plurality of defocus amounts is determined as the used defocus amount, or if the closest or infinite defocus amount is determined as the used defocus amount, the process proceeds to step S104.

[0080] In step S104, the camera MPU 125 normalizes the plurality of defocus amounts acquired in step S102. Specifically, the plurality of defocus amounts acquired in step S102 are divided by the defocus amount rate of the corresponding image height, focus detection direction, or subject angle. As a result, each defocus amount becomes a defocus amount (second defocus amount) normalized to a value corresponding to the central defocus amount with a defocus amount rate of 1, and it becomes possible to compare the plurality of normalized defocus amounts regardless of the image height, focus detection direction, and subject angle.

[0081] As a result, as a histogram of the normalized defocus amounts, a histogram as shown in FIG. 9(d) is obtained, and the camera MPU 125 determines the normalized defocus amount within the def range x + 3, which is the maximum number of focus detection regions, as the used defocus amount (third defocus amount).

[0082] Next, in step S105, the lens MPU 125 calculates (acquires) the driving amount of the focus lens 104 using the use defocus amount determined in step S104 or one defocus amount acquired in step S102. Specifically, the number of pulses P of the focus drive pulse is calculated using the above-described equations (3) and (4). At this time, when step S104 has been passed through, as the defocus amount d(h) and the focus sensitivity S(h) in equations (3) and (4), those at the center (h = 0) may be used. When step S104 has not been passed through, as the defocus amount d(h) and the focus sensitivity S(h) in equations (3) and (4), values corresponding to the image height at which the defocus amount was acquired may be used.

[0083] Next, in step S106, the camera MPU 125 transmits a focus drive command including the driving amount calculated in step S105 to the lens MPU 117. The lens MPU 117 drives the focus lens 104 by controlling the focus drive unit 109 based on the received focus drive command.

[0084] After this, the camera MPU 125 ends this process in step S107.

[0085] According to the above AF process, it is possible to obtain an accurate one defocus amount for AF from a plurality of defocus amounts in which at least one of the image height, the focus detection direction, and the angle of the subject (for example, the image height and the focus detection direction, or the image height and the angle of the subject) is different from each other.

[0086] Note that, in this embodiment, the case of performing focus control to move the focus lens as a focus element in the optical axis direction has been described, but focus control may be performed to move the imaging element as a focus element in the optical axis direction.

[0087] The above embodiments include the following configurations.

[0088] (Configuration 1) Focus detection means for performing focus detection within an imaging screen and obtaining a plurality of first defocus amounts in which at least one of the image height, the focus detection direction, and the angle of the subject is different from each other, and control means for performing focus control, wherein the control means, obtains first information indicating a relationship between the defocus amount at a specific position of the imaging screen and the defocus amount corresponding to at least one of the regions other than the specific position, obtains a plurality of second defocus amounts using the plurality of first defocus amounts and the first information, and obtains a third defocus amount for use in the focus control from the plurality of second defocus amounts. An imaging apparatus characterized by this. (Configuration 2) wherein the control means, obtains, as the first information, information indicating a relationship between the defocus amount at the specific position and the defocus amount corresponding to the image height and the focus detection direction in the region other than the specific position, and obtains the plurality of second defocus amounts using the plurality of first defocus amounts in which at least one of the image height and the focus detection direction is different from each other and the first information. The imaging apparatus according to Configuration 1, characterized by this. (Configuration 3) wherein the control means, obtains, as the first information, information indicating a relationship between the defocus amount at the specific position and the defocus amount corresponding to the image height and the angle of the subject in the region other than the specific position, and obtains the plurality of second defocus amounts using the plurality of first defocus amounts in which at least one of the image height and the angle of the subject is different from each other and the first information. The imaging apparatus according to Configuration 1, characterized by this. (Configuration 4) The first information is information regarding the ratio of the defocus amount in the region other than the specific position to the defocus amount at the specific position. The imaging apparatus according to any one of Configurations 1 to 3, characterized by this. (Configuration 5) The imaging apparatus according to any one of Configurations 1 to 4, wherein the control means acquires the plurality of second defocus amounts obtained by normalizing the plurality of first defocus amounts using the first information. (Configuration 6) The imaging apparatus according to any one of Configurations 1 to 5, wherein the control means acquires the third defocus amount from the mode value of the plurality of second defocus amounts in the histogram of the plurality of second defocus amounts, the average value of the plurality of second defocus amounts, or the nearest or infinite distance value among the plurality of second defocus amounts. (Configuration 7) The control means acquires second information indicating the relationship between the unit displacement amount of the focus element moved by the focus control and the change amount of the position of the subject image, and acquires the driving amount of the focus element in the focus control using the third defocus amount and the second information. The imaging apparatus according to any one of Configurations 1 to 6. (Configuration 8) The imaging apparatus is capable of attaching and detaching an interchangeable lens, and the control means acquires the first information from the interchangeable lens. The imaging apparatus according to any one of Configurations 1 to 7.

[0089] (Other Embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and having one or more processors in the computer of the system or apparatus read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0090] Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment when implementing the present invention.

Description of Reference Numerals

[0091] 104 Focus lens 122 imaging element 125 camera MPU 129 phase difference AF section

Claims

1. Focus detection means for performing focus detection within an imaging screen and obtaining a plurality of first defocus amounts in which at least one of the image height, the focus detection direction, and the angle of the subject is different from each other; And control means for performing focus control. The control means: Obtains first information indicating the relationship between the defocus amount at a specific position on the imaging screen and the defocus amount corresponding to at least one of the regions other than the specific position; Obtains a plurality of second defocus amounts using the plurality of first defocus amounts and the first information; An imaging device, characterized in that a third defocus amount used for the focus control is obtained from the plurality of second defocus amounts.

2. The control means: As the first information, obtains information indicating the relationship between the defocus amount at the specific position and the defocus amount corresponding to the image height and the focus detection direction in the region other than the specific position; The imaging device according to claim 1, characterized in that the plurality of second defocus amounts are obtained using the plurality of first defocus amounts in which at least one of the image height and the focus detection direction is different from each other and the first information.

3. The control means: As the first information, obtains information indicating the relationship between the defocus amount at the specific position and the defocus amount corresponding to the image height and the angle of the subject in the region other than the specific position; The imaging device according to claim 1, characterized in that the plurality of second defocus amounts are obtained using the plurality of first defocus amounts in which at least one of the image height and the angle of the subject is different from each other and the first information.

4. The imaging device according to claim 1, characterized in that the first information is information regarding the ratio of the defocus amount in the region other than the specific position to the defocus amount at the specific position.

5. The imaging device according to claim 1, wherein the control means acquires the plurality of second defocus amounts obtained by normalizing the plurality of first defocus amounts using the first information.

6. The imaging device according to claim 1, wherein the control means acquires the third defocus amount from the most frequent second defocus amount in the histogram of the plurality of second defocus amounts, the average value of the plurality of second defocus amounts, or the value closest to the near side or the infinite far side among the plurality of second defocus amounts.

7. The control means acquires second information indicating the relationship between the unit displacement amount of the focus element moved by the focus control and the change amount of the position of the subject image, and acquires the driving amount of the focus element in the focus control using the third defocus amount and the second information. The imaging device according to claim 1.

8. The imaging device is capable of attaching and detaching an interchangeable lens, and the control means acquires the first information from the interchangeable lens. The imaging device according to claim 1.

9. a step of performing focus detection within an imaging screen to acquire a plurality of first defocus amounts in which at least one of the image height, the focus detection direction, and the angle of the subject is different from each other; a step of acquiring first information indicating the relationship between the defocus amount at a specific position on the imaging screen and the defocus amount corresponding to at least one of the regions other than the specific position; a step of acquiring a plurality of second defocus amounts using the plurality of first defocus amounts and the first information; and a step of acquiring a third defocus amount used for focus control from the plurality of second defocus amounts. A control method for an imaging device.

10. A program, characterized in that a computer of the imaging device is caused to execute processing according to the control method described in claim 9.

Images