JP6071574B2 - Imaging device - Google Patents

Description

  The present invention relates to an image pickup apparatus having an image pickup element in which a part of the image pickup element is used as a phase difference type focus detection element.

  2. Description of the Related Art Conventionally, an image sensor that also uses a part of the image sensor as a phase difference type focus detection element is known (for example, Patent Document 1). As shown in FIG. 14, the imaging apparatus disclosed in Patent Document 1 has a plurality of phase difference AF areas 101a, 101b, 101c,... Arranged on the imaging surface of an imaging element. When the focus detection area 103 is determined, the phase difference AF area 101h having the largest overlap area in the focus detection area 103 is determined as the phase difference AF focus detection area, and the defocus detected by the phase difference AF area 101h is determined. Use the amount to adjust the focus.

Japanese Patent No. 4853071

  As described above, in the imaging apparatus described in Patent Document 1, the distance measurement area for phase difference AF is selected only by the size of the overlapping area between the subject detection area and the distance measurement area. However, if the selection is made only with the size of the overlapping area, a low-contrast distance-measuring area or a distance-measuring area having no contour component of the subject may be selected. In this case, the desired focus position is not focused. There is a fear.

  The present invention has been made in view of such circumstances, and provides an imaging apparatus capable of selecting a focus detection area of phase difference AF that is most suitable for a subject of interest and accurately detecting a focal point. For the purpose.

In order to achieve the above object, an imaging apparatus according to a first aspect of the present invention includes a plurality of pixels having a photoelectric conversion unit that converts an optical image formed by an imaging optical system into an electrical signal, A focus detection pixel configured to limit an incident direction of a light beam incident on the pixel, and an imaging pixel configured to limit a light beam incident on the pixel to be less than the focus detection pixel, In the imaging apparatus having the imaging device in which the plurality of pixels are two-dimensionally arranged, attention subject detection means for detecting the position of the subject of interest based on the pixel signal output from the imaging device, and the position of the subject of interest And a plurality of distance measurement point setting means for setting a plurality of distance measurement points corresponding to the positions of the focus detection pixels, and a plurality of default values based on outputs of the focus detection pixels corresponding to the plurality of distance measurement points. A calculation means for calculating a focus amount; a priority order determination means for determining the priority order of the set distance measuring points; and determining the reliability of the defocus amount detected corresponding to the set distance measuring points. Reliability determination means, and selection means for selecting a distance measurement point from the plurality of distance measurement points set based on the output of the priority determination means and the output of the reliability determination means The target subject detection means detects an area corresponding to the face, and the ranging point setting means compares a specific area inside the area corresponding to the face with another area corresponding to the face. Thus, the distance measuring points are arranged more densely .

  In the imaging device according to a second aspect based on the first aspect, the priority order determining means increases the priority order of the distance measuring points closer to the specific position of the subject of interest among the plurality of distance measuring points. .

In the imaging apparatus according to a third aspect, in the first or second aspect, the reliability determination means outputs a reliability evaluation value indicating the reliability of the defocus amount, and the selection means A distance measuring point is selected based on a result obtained by weighting the priority of the plurality of distance measuring points determined by the priority determining means to the reliability evaluation value output from the reliability determining means.

In the imaging device according to a fourth invention , in any one of the first to third inventions , the subject-of-interest detection means detects a region corresponding to a facial organ, and the ranging point setting means Ranging points are arranged more densely in the area corresponding to the organ than in the area not corresponding to the organ.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can select the ranging area of phase difference AF optimal for the to-be-focused object, and can detect a focal point accurately can be provided.

1 is a block diagram mainly showing an electrical configuration of a camera according to an embodiment of the present invention. It is a block diagram which shows the detail of the AF calculating part of the camera which concerns on one Embodiment of this invention. It is a figure which shows arrangement | positioning of the pixel which consists of the pixel for phase difference AF detection of the imaging device of the camera which concerns on one Embodiment of this invention, and an imaging pixel. It is an enlarged view of one ranging area of the image sensor of the camera concerning one embodiment of the present invention. It is a figure explaining the ranging method in the camera which concerns on one Embodiment of this invention. It is a figure explaining the ranging method in the camera which concerns on one Embodiment of this invention. 6 is a graph showing a correlation calculation result in the camera according to the embodiment of the present invention. It is a figure which shows the example of a setting of a ranging area in the camera which concerns on one Embodiment of this invention. It is a figure which shows the example of a setting of a ranging area in the camera which concerns on one Embodiment of this invention. It is a figure which shows the example of prioritization of a ranging area in the camera which concerns on one Embodiment of this invention. It is a figure which shows the example of prioritization of a ranging area in the camera which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the camera which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the camera which concerns on one Embodiment of this invention. It is a figure which shows the prior art example of the image pick-up element which shares a part of image pick-up element as a photodiode for focus detection.

  A preferred embodiment will be described below using a digital camera to which the present invention is applied (hereinafter abbreviated as “camera”) according to the drawings. FIG. 1 is a block diagram mainly showing an electrical configuration of a camera according to an embodiment of the present invention. The camera according to this embodiment includes an interchangeable lens barrel 10 and a camera body 20. In the present embodiment, the interchangeable lens barrel 10 and the camera body 20 are configured separately, but may be configured integrally as in a general compact camera.

  A photographic lens 11 is disposed in the interchangeable lens barrel 10. The photographing lens 11 includes a plurality of optical lenses for forming an optical image of the subject S. An actuator 12 and a lens control unit 13 are provided in the interchangeable lens barrel 10. The lens control unit 13 receives the defocus amount from the AF calculation unit 23 in the camera body 20 and controls the actuator 12 based on these pieces of information. The actuator 12 moves the photographing lens 11 in the optical axis direction and performs focusing.

  In the camera body 20, an image pickup device 21, an image processing unit 22, an AF calculation unit 23, and a recording unit 24 are provided. The image sensor 21 is disposed on the optical axis of the photographing lens 11 and in the vicinity of the imaging position of the subject image. The imaging device 21 includes a plurality of pixels having a photoelectric conversion unit that converts a subject image (optical image) into an electrical signal. The plurality of pixels include a phase difference AF detection pixel (also referred to as a focus detection pixel) configured to limit an incident direction of a light beam incident on the pixel, and a light beam incident on the pixel is more than the phase difference AF detection pixel. A plurality of pixels are arranged two-dimensionally, including imaging pixels configured not to be limited. The arrangement of the phase difference AF detection pixels and the imaging pixels of the imaging element 21 will be described later with reference to FIGS. 3 and 4.

  The imaging element 21 outputs the pixel value output from the phase difference AF detection pixel and the imaging pixel to the image processing unit 22 and the AF calculation unit 23. The image processing unit 22 inputs pixel values from the imaging pixels among the pixel values, and performs image processing for the live view display image and the recording image. Further, the image processing unit 22 outputs the image data processed for recording to the recording unit 24. The recording unit 24 includes an electrically rewritable nonvolatile memory, and inputs and records image data for recording. The image processing unit 22 detects the face of the subject using the pixel value, outputs the center coordinate position of the face, detects an organ such as an eye in the face, and the specific coordinate position of the organ. Is output.

  The AF calculation unit 23 receives pixel values from the phase difference AF detection pixels among the pixel values, and performs AF calculation based on the phase difference AF. In the AF calculation, a plurality of distance measuring points corresponding to the positions of the phase difference AF detection pixels are set based on the center coordinate position and the specific coordinate position acquired from the image processing unit 22, and each of the set distance measuring points is set. The defocus amount is calculated for. Then, the priority order of the set focus points is determined, the reliability of the defocus amount of the focus point is further determined, and the photographing lens is selected from a plurality of focus points based on the priority order and the reliability. Select a focusing point for 11 focusing.

  Next, details of the AF calculation unit 23 will be described with reference to FIG. The pixel value 21a is a pixel value output from the image sensor 21 and is temporarily stored in an SDRAM (not shown) or the like.

  Further, a face detection unit 22 a is provided in the image processing unit 22. The face detection unit 22a determines whether or not there is a face in the subject image based on the pixel value of the imaging pixel from the image sensor 21, and if the face is included, the position ( Center coordinate position) and size are detected. Furthermore, organs such as the right eye, left eye, and nose are detected, and the specific coordinate position of the organ is also detected. The face detection unit 22a functions as target subject detection means for detecting the position of the target subject based on the pixel signal output from the image sensor. The center coordinate and the specific coordinate position detected by the face detection unit 22 a are output to the AF ranging point setting unit 33 in the AF calculation unit 23.

  The AF distance measurement point setting unit 33 sets a plurality of distance measurement points corresponding to the center coordinate position and the specific coordinate position detected by the face detection unit 22a. As will be described later, a plurality of distance measuring points can be set on the image sensor 21, and a distance measuring point in the vicinity of the center coordinate position or a specific coordinate position is set and set from the plurality of distance measuring points. The center coordinates of each distance measurement area are output to the distance measurement area priority setting unit 35 and the reliability evaluation unit 36. The AF distance measurement point setting unit 33 functions as distance measurement point setting means for setting a plurality of distance measurement points corresponding to the position of the focus detection pixel for the position of the subject of interest. The setting of the ranging area will be described later with reference to FIGS.

  The phase difference pixel generation unit 34 receives the image data of the phase difference AF detection pixels from among the pixel values 21a, generates a phase difference AF detection pixel sequence, and outputs a defocus amount calculation unit / reliability evaluation unit 37. Output to.

  The defocus amount calculation unit / reliability evaluation unit 37 receives the image data of the pixel array for phase difference AF detection, calculates the defocus amount by the phase difference AF method, and measures the defocus amount of each distance measurement area. It outputs to the distance point determination part 38. Further, the contrast value A of each distance measurement area is calculated using the image data of the pixel array for phase difference AF detection, and is output to the distance measurement point determination unit 38. Further, the reliability evaluation value (correlation value slope Fs) of each ranging area is also obtained from the value at the time of phase difference AF calculation, and is output to the ranging point determination unit 38. The defocus amount calculation unit / reliability evaluation unit 37 functions as a calculation unit that calculates a plurality of defocus amounts based on outputs of the focus detection pixels corresponding to a plurality of distance measuring points. The defocus amount calculation unit / reliability evaluation unit 37 also functions as a reliability determination unit that determines the reliability of the defocus amount detected corresponding to the set distance measuring point. The calculation of the defocus amount by the phase difference AF and the determination of the reliability will be described later with reference to FIGS.

  The ranging area priority order setting unit 35 inputs the center coordinates of each ranging area from the AF ranging point setting unit 33, determines the priority order of the ranging areas, and measures each ranging area priority list. The data is output to the point determination unit 38. A method of determining the priority order of the distance measurement areas will be described later with reference to FIG. The distance measurement area priority order setting unit 35 functions as priority order determination means for determining the priority order of the set distance measurement points.

  The reliability evaluation unit 36 inputs the pixel value from the imaging pixel from the pixel value 21 a, and receives the center coordinates of each ranging area from the AF ranging point setting unit 33. Using these pieces of information, contrast value calculation is performed, and the contrast value B of each distance measurement area is output to the distance measurement point determination unit 38. That is, for the face and organ coordinates detected by the face detection unit 22a and the distance measuring area in the vicinity thereof, the contrast value is calculated using the pixel value from the imaging pixel. The defocus amount calculation unit / reliability evaluation unit 37 also calculates the contrast value A. However, since the contrast B is calculated using the pixel value from the imaging pixel, it takes longer calculation time but has higher accuracy. The value can be determined. The reliability evaluation unit 36 functions as a reliability determination unit that determines the reliability of the defocus amount detected corresponding to the set ranging point.

  As described above, the ranging point determination unit 38, each ranging area priority order list, each ranging area contrast value B, each ranging area defocus amount, each ranging area contrast value A, each ranging area correlation. A value gradient Fs is input to select a distance measuring point. The selection of the distance measuring point will be described with reference to FIG. The distance measuring point determination unit 38 outputs the defocus amount of the selected distance measuring point. The distance measuring point determination unit 38 functions as a selection means for selecting a distance measuring point from the plurality of distance measuring points set based on the output of the priority order determining means and the output of the reliability determining means. In selecting a distance measurement area, reliability evaluation values such as a contrast value and a correlation value gradient Fs may be weighted to the area of the subject in the distance measurement area, as in the prior art.

  Next, the image sensor 21 will be described with reference to FIGS. 3 and 4. In the example shown in FIG. 3, the image sensor 21 is divided into a column direction X1-X7 and a row direction Y1-Y7, and each of these 49 areas becomes a distance measurement area. The area denoted by reference numeral 21b is represented by (X1, Y1). The center point 21c of each distance measuring area of each area is set as the center coordinates of the distance measuring area.

  FIG. 4 shows an arrangement example of pixels in one distance measurement area. As shown in FIG. 4, the interior of each ranging area shown in FIG. 3 is composed of phase difference AF detection pixels and imaging pixels.

  In the distance measurement area shown in FIG. 4, the left aperture phase difference AF detection pixel 21d, the imaging pixel 21e, and the right aperture phase difference AF pixel 21f are alternately arranged. That is, in the leftmost column, L11, L21, L31, and L41 are the left aperture phase difference AF pixels 21d, and R11, R21, R31, and R41 are the right aperture phase difference AF pixels 21f. Imaging pixels 21e are arranged. In the second column from the leftmost side, there are only the imaging pixels 21e. Thereafter, the column including the phase difference AF detection pixels and the column including only the imaging pixels are alternately and repeatedly arranged.

  In the present embodiment, the column including the phase difference AF detection pixels and the column including only the imaging pixels are every other column. However, the column including the phase difference AF detection pixels and the phase difference AF detection pixels. Of course, it is possible to arrange a column composed of only two or more imaging pixels between the columns including.

  The AF pixel column generated by the phase difference pixel generation unit 34 (see FIG. 2) is an average value of pixel values from the left aperture AF detection pixel or a pixel from the right aperture AF detection pixel for each pixel column. Calculate the average value. That is, it is generated by the following calculation.

Left aperture AF detection pixel array:
L1 = (L11 + L21 + L31 + L41) / 4
L2 = (L12 + L22 + L32 + L42) / 4
L3 = (L13 + L23 + L33 + L43) / 4
...
Ln = (L1 (n) + L2 (n) + L3 (n) + L4 (n)) / 4

Pixel array for right aperture AF detection:
R1 = (R11 + R21 + R31 + R41) / 4
R2 = (R12 + R22 + R32 + R42) / 4
R3 = (R13 + R23 + R33 + R43) / 4
...
Rn = (R1 (n) + R2 (n) + R3 (n) + R4 (n)) / 4

In the example shown in FIG. 4, the upper left coordinate is (X1, Y1), the lower right coordinate is (Xr, Yr), and the distance measurement area center coordinate 21c is (Xk, Yk). The center coordinates (Xc [k], Yc [k]) of the distance measurement area are arbitrary lengths (a [k], b [k] for each distance measurement area from the face center coordinates / specific coordinates (Xco, Yco). ]) Is added (in this embodiment, k = 1 to 7),
Xc [k] = Xco + a [k], Yc [k] = Yco + b [k]
It becomes. Note that k is a distance measurement area number, and k = 0, 1, 2,..., Area_num−1 (Area_num: number of distance measurement areas).

  The defocus amount calculation unit / reliability evaluation unit 37 determines (c [k], d [k]) (c [k], d [k] from the center (Xc [k], Yc [k]) of the distance measurement area. ] Is a numerical value determined in advance for each area, x and y direction range of correlation calculation), and the upper left coordinates (X1 [k], Y1 [k]) = (Xc [k] −c [k], Yc [K] −d [k]), lower right coordinates (Xr [k], Yr [k]) = (Xc [k] + c [k], Yc [k] + d [k]) The calculation for obtaining the defocus amount based on the phase difference AF described with reference to FIGS. 5 to 7 is performed.

  FIG. 6 is a diagram illustrating the principle of distance measurement for phase difference AF. A right aperture R and a left aperture L are provided in the luminous flux of the photographic lens 11, and an image OR corresponding to a pixel output based on the luminous flux of only the right aperture R on the image sensor 21 and a pixel output based on the luminous flux of only the left aperture L are provided. Comparing the corresponding images OL, if the images are not in focus, the images OR and OL are shifted by the shift amount ZR. Further, the two images IN coincide with each other at the in-focus position separated by the defocus amount d. Therefore, the shift amount ZR is obtained, the defocus amount d is obtained based on the shift amount ZR, and the photographing lens 11 is moved to the in-focus position based on the defocus amount d. In addition, the code | symbol G in FIG. 6 shows the distance between the gravity centers of right and left opening, and F shows the distance from an imaging surface to a pupil.

  5A and 5B show pixel values (pixel edge components) corresponding to the arrangement positions of the pixel arrays L1 to L (n) for left aperture phase difference AF detection (corresponding to the image OL in FIG. 6). To do). Further, (c) and (d) show pixel values (pixel edge components) corresponding to the arrangement positions of the pixel arrays R1 to R (n) for right aperture phase difference AF detection (corresponding to the image OR in FIG. 6). From this, the correlation of the subject image projected on the pixel array of the left and right openings is obtained. The difference in phase difference AF detection pixel position with the most similar object image shape is the shift amount (parallax) ZR.

  For example, the window corresponding to the pixel column of the image of the left aperture is fixed, and the window corresponding to the pixel column of the image of the right aperture is shifted pixel by pixel, and the left aperture phase difference AF detection in the window at this time is detected. The evaluation value Fm is obtained from the cumulative value of the difference between the pixel value for use and the right aperture phase difference AF detection pixel. The shift amount when the evaluation value Fm becomes the minimum value is the shift amount ZR. FIG. 7 is a graph showing the position and Fm of the phase difference AF detection pixel in the vicinity where the evaluation value Fm becomes the minimum value. In this graph, the evaluation value Fm is minimum when the position of the phase difference AF detection pixel is min. Here, since the evaluation value Fm is discrete data, interpolation processing is performed using a plurality of evaluation values Fm in the vicinity of the minimum value, the true minimum value is obtained, and the shift amount ZR is calculated.

When the shift amount ZR is obtained, the defocus amount d can be calculated from the shift amount ZR by the following equation.
d = F * ZR / (G-ZR)
Here, d: Defocus amount F: Distance from the image sensor to the pupil ZR: Shift amount G: Distance between the centers of gravity of the left and right apertures

  The defocus amount calculation unit / reliability evaluation unit 37 uses the correlation value gradient Fs of the evaluation value Fm as the reliability value of the phase difference AF. That is, in the example shown in FIG. 7, the slope Fs of the straight line passing through the larger evaluation value FM of the minimum value (FMIN) of the evaluation value Fm and the two Fm before and after the minimum value represents the reliability. Calculate and output as an evaluation value.

  Next, the relationship between the face detected by the face detection unit 22a and the distance measurement area set by the AF distance measurement point setting unit 33 will be described with reference to FIGS. FIG. 8 shows an example in which the distance measurement areas are arranged so as not to overlap. In FIG. 8, ranging areas a1 to d4 within a predetermined range from the face center Fc (center coordinate position) of the face Fa detected by the face detection unit 22a among the ranging areas of the image sensor 21 are AF ranging points. Set by the setting unit 33. As described above, the distance measurement areas a1 to d4 are set so as not to overlap each other. Note that Fe is an eye as a facial organ detected by the face detection unit 22a.

  FIG. 9 shows another example of the arrangement of the distance measurement areas. In FIG. 9, distance measuring areas e1 to e5 having the same size as the distance measuring areas a1 to d4 are densely arranged near the center of the face. The ranges of the ranging areas b2, b3, c2, and c3 are the same as those in FIG. The distance measuring area e1 is set so as to overlap the right half of the distance measuring area b2 and the left half of the distance measuring area b3. The ranging area e2 is set so as to overlap the lower half of the ranging area b2 and the upper half of the ranging area c2. The ranging area e3 is superimposed on the lower right quadrant of the ranging area b2, the lower left four half of the ranging area b3, the upper right half of the ranging area c2, and the upper left half of the ranging area c3. Is set. The distance measurement area e4 is set so as to overlap the lower half of the distance measurement area b3 and the upper half of the distance measurement area c3. The distance measurement area e5 is set so as to overlap the right half of the distance measurement area c2 and the left half of the distance measurement area c3.

  In FIG. 9, ranging areas are densely arranged near the center of the face. However, the present invention is not limited to this, and the distance measuring area may of course be densely arranged near the center of an organ such as the eyes, nose and mouth.

  As described above, the AF ranging point setting unit 33 performs a plurality of measurement in the vicinity based on the position of the subject of interest (the center position of the face or the specific position of the organ such as the eyes) detected by the face detection unit 22a. Set the distance area. Further, as shown in FIG. 9, the AF ranging point setting unit 33 sets the ranging points more densely in a specific area inside the area corresponding to the face than in other areas corresponding to the face. It has a function as a distance measuring point setting unit to be arranged in. The AF ranging point setting unit 33 also has a function as a ranging point setting unit that places the ranging points more densely in the region corresponding to the organ than in the region not corresponding to the organ.

  Next, the creation of a priority list of distance measurement areas performed by the distance measurement area priority order setting unit 35 will be described with reference to FIG. FIG. 10 shows an example of a priority list of ranging areas. FIG. 10A is an example in which priorities are assigned in order of increasing distance from the specific coordinates of organ detection detected by the face detection unit 22a. Here, b2, e1, e2,... Indicate the position of the distance measurement area shown in FIG. Thus, the distance measurement area priority order setting unit 35 has a function as priority order setting means for increasing the priority order of distance measurement points that are closer to the specific position of the subject of interest among the plurality of distance measurement points.

  FIG. 10B shows an example in which priorities are assigned in order of increasing distance from the subject center coordinates. FIG. 10C shows an example in which priorities are assigned in the order of defocus positions (closest order). Since the defocus amount calculation unit / reliability evaluation unit 37 calculates the defocus position for each distance measurement area, the information is obtained and ranked. In this case, the priority is higher in the distance measurement area where the subject close to the camera is located.

  Note that it is not necessary to create an ascending order list of all ranging areas. Further, in the list creation in the order closer to the specific coordinates or the center coordinates of the subject shown in FIGS. 10A and 10B, an area more than a certain distance (distance threshold) or the data shown in FIG. Areas that are less than the focus amount (threshold of the distance in the infinite direction) may be excluded from the list.

  Next, the selection of the optimum distance measurement area performed by the distance measurement point determination unit 38 will be described with reference to FIG. The ranging point determination unit 38 selects a ranging area by using the priority list of the ranging areas shown in FIG. 10 and the reliability evaluation weighting result of each area, and selects the selected ranging area. Output the defocus amount.

  In the example shown in FIG. 11, specific coordinates based on the organ detection result of FIG. 10A are used as the distance measurement area priority order list (“priority of distance measurement area” and “A” in FIG. 11). : Order close to specific coordinates "). Further, as the reliability evaluation value for weighting, the contrast value A of each ranging area calculated by the defocus amount calculation unit / reliability evaluation unit 37 is used (“B: Contrast value in FIG. 11). "reference). A weighting calculation 1 / (A * B) is performed using A and B in FIG. 11, and the area having the largest calculation result, that is, the distance measurement area e1 in FIG. 11 is selected.

  In the example shown in FIG. 11, the contrast value A is used as the reliability evaluation value for weighting. However, the present invention is not limited to this, and contrast is used instead of the contrast value A calculated by the reliability evaluation unit 36. The value B may be used, or the correlation value gradient Fs calculated by the defocus amount calculation unit / reliability evaluation unit 37 may be used. In this embodiment, weighting is performed by multiplication as 1 / (A * B). However, the present invention is not limited to this, and a plurality of reliability values may be weighted.

  Thus, in this embodiment, the priority set by the distance measurement area priority setting unit 35 and the reliability evaluation calculated by the reliability evaluation unit 36 or the defocus amount calculation unit / reliability evaluation unit 37 are calculated. Using the values (contrast value A, contrast value B, correlation value gradient Fs), the distance measuring point determination unit 38 selects a distance measuring point. For this reason, it is possible to select a distance measuring area that is close to the subject of interest and has high reliability in the defocus amount calculation result. Therefore, the distance measuring point determination unit 38 selects the distance measuring points based on the results obtained by weighting the priorities of the plurality of distance measuring points determined by the priority determining means and the reliability output by the reliability determining means. It has a function as a means.

  Next, the operation in this embodiment will be described with reference to the flowcharts shown in FIGS.

  When the distance measuring operation is started, first, the face center or specific coordinates are acquired, and these coordinates are set to (Xco, Yco) (S1). Here, when the face is centered by the face detection unit 22a, the center coordinates are acquired, and when the face organ (right eye, left eye, nose, mouth, etc.) is detected, the specific coordinates are acquired. The coordinates are (Xco, Yco). If the photographer can specify the facial organ or the like in advance on the menu screen or the like, the instruction is followed.

  Once the face center or specific coordinates are acquired, the number of distance measurement areas (Area_Num) is set (S3). As described with reference to FIGS. 8 and 9, the AF ranging point setting unit 33 sets a ranging area around the center coordinates or specific coordinates. In this step, the number of distance measurement areas set at this time is set.

  Once the number of ranging areas is set, the variable k is reset to 0 (S7). k indicates the number of the distance measurement area that has been set. In this step, the number of the distance measurement area is reset.

  When k indicating the distance measurement area number is reset to 0, it is next determined whether or not k = Area_num (S9). Area_num indicates the number of distance measurement areas. In this step, it is determined whether or not the defocus amount calculation in steps S11 to S21 has been performed for all the distance measurement areas.

If the result of determination in step S9 is not k = Area_num, the center coordinates of each distance measurement area are set (S11). The center coordinates (Xc [k], Yc [k]) of the distance measurement area are arbitrary lengths a [k], b [k] for each distance measurement area from the face center coordinates or specific coordinates (Xco, Yco). Since it is set as the position to which is added, it is obtained from the following formula.
(Xc [k], Yc [k]) = (Xco + a [k], Yco + b [k])

Once the center coordinates of each distance measurement area are set, the AF distance measurement point setting unit 33 next sets the area of each distance measurement area (S13). The area of each ranging area is obtained by adding and subtracting (c [k], d [k]) to the center coordinates (Xc [k], Yc [k]) of the ranging area to obtain the upper left coordinates (X1 [k], Y1 [k]) and lower right coordinates (Xr [k], Yr [k]) are obtained, and the coordinates are as follows.
(X1 [k], Y1 [k]) = (Xc [k] −c [k], Yc [k] −d [k])
(Xr [k], Yr [k]) = (Xc [k] + c [k], Yc [k] + d [k])

  When the center coordinates of each ranging area are set, the reliability evaluation unit 36 acquires the contrast value B in parallel with the area setting of each ranging area (S25). Here, the image data of the imaging pixel is input, and the contrast value B is calculated using the image data of the imaging pixel.

  Once the areas of each ranging area are set, the phase difference pixel generation unit 34 generates phase difference pixel rows Lk and Rk (S15). Here, the phase difference pixel columns Lk and Rk are generated within the range of the coordinates (X1 [k], Y1 [k]) to (Xr [k], Yr [k]) in the distance measurement area.

  When the area of each ranging area is set, the ranging area priority setting unit 35 generates each ranging area priority list in parallel with the generation of the phase difference pixel rows Lk and Rk (S27). For example, as shown in FIG. 10, a predetermined priority order is assigned, and a priority order list in which ranging areas are arranged sequentially from List [0] is generated.

  Once the phase difference pixel columns Lk and Rk are generated, the L or R column contrast value A is acquired (S17). Here, the cumulative value of the edge component of the L row or the R row is calculated. That is, the cumulative value of the difference values between adjacent phase difference AF detection pixels is calculated, and this value is stored in the memory as the contrast value A contrast_A [k].

  When the contrast value A of the L column or the R column is acquired, the defocus amount calculation unit / reliability evaluation unit 37 then acquires the correlation value change rate (slope) Fs [k] (S19). As shown in FIG. 7, as a result of performing a correlation operation between the image data of the left aperture phase difference AF detection pixel sequence and the right aperture phase difference AF detection pixel sequence, the minimum correlation value FMIN and The slope of the straight line passing through the larger correlation value FM among the left and right correlation values is defined as a change rate Fs [k].

When the correlation value change rate Fs is acquired, the defocus amount calculation unit / reliability evaluation unit 37 then acquires the defocus amount d [k] (S21). As described with reference to FIG. 6, the defocus amount d [k]
d = F * ZR / (G-ZR)
Calculate from
Here, d: defocus amount, F: distance from the image sensor to the pupil, ZR: shift amount, and G: distance between the centers of gravity of the left and right openings.

  Once the defocus amount is calculated in step S21, 1 is added to k indicating the distance measurement area number in step S23. When 1 is added to k in step S23, or the contrast value B is acquired in step S25, or each distance measurement area priority list is created in step S27, the process returns to step S9.

  As a result of the determination in step S9, when k indicating the distance measurement area number reaches Area_num indicating the number of distance measurement areas, a reliability evaluation value (S_k) is selected (S31). As described above, the reliability evaluation value Sk includes the contrast value A and the correlation value gradient Fs calculated by the defocus amount calculation unit / reliability evaluation unit 37, and the contrast value B calculated by the reliability evaluation unit 36. . Here, one of these three values is selected as S [k].

  When the reliability evaluation value S_k is selected, the distance measuring point determination unit 38 next calculates priority (List [k]) * reliability S [k] (S33). Here, as shown in the example of FIG. 11, in order to select an optimum distance measurement area, the priority is weighted with reliability.

  If the reliability weighting calculation is performed on the priority, the ranging point determination unit 38 next selects the optimum ranging area and selects the defocus amount calculated in the optimum ranging area (S35). When the defocus amount is selected, this flow ends.

  In step S31, only one reliability evaluation value (S_k) has been selected from the three types. However, the present invention is not limited to this, and an optimum ranging area is selected using all or some of the three types. You may make it. Further, as shown in FIG. 10, three types of priorities are assigned as priorities, but an optimal distance measurement area may be selected using all or some of the three types.

  As described above, in the embodiment of the present invention, the subject of interest is detected (face detection unit 22a, S1 in FIG. 12), and a plurality of distance measurement areas are set based on the positions of the subject of interest (AF The priority of the distance measurement areas is determined together with the distance measurement point setting unit 33 (S5 in FIG. 12) (range measurement area priority order setting unit 35, S27 in FIG. 12), and the defocus amount reliability of the set distance measurement area is determined. (Reliability evaluation unit 36, defocus amount calculation unit / reliability evaluation unit 37, S25, S17, S19 in FIG. 12). Then, an optimum distance measurement area is selected based on the priority of the distance measurement area and the reliability of the defocus amount (ranging point determination unit 38, S35 in FIG. 12), and the defocus of the selected distance measurement area is selected. Focusing is performed based on the amount. For this reason, in the present embodiment, it is possible to select a focus detection area of phase difference AF that is optimal for the subject of interest, and to detect the focal point with high accuracy.

  In the embodiment of the present invention, a digital camera has been described as an apparatus for photographing. However, the camera may be a digital single-lens reflex camera, a mirrorless camera, or a compact digital camera. A camera for moving images such as a camera may be used, and a camera built in a mobile phone, a smart phone, a personal digital assistant (PDA), a game device, or the like may be used. In any case, the present invention can be applied to any device having an image sensor that uses a part of the image sensor as a phase difference type focus detection element.

  In addition, regarding the operation flow in the claims, the specification, and the drawings, even if it is described using words expressing the order such as “first”, “next”, etc. It does not mean that it is essential to implement in this order.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, you may delete some components of all the components shown by embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 10 ... Interchangeable lens barrel, 11 ... Shooting lens, 12 ... Actuator, 13 ... Lens control part, 20 ... Camera body, 21 ... Imaging element, 21a ... Pixel value , 21c: ranging area center point, 21d: left aperture phase difference AF detection pixel, 21e: imaging pixel, 21f: right aperture phase difference AF detection pixel, 22: image Processing unit 22a ... Face detection unit 23 ... AF calculation unit 24 ... Recording unit 33 ... AF distance measuring point setting unit 34 ... Phase difference pixel generation unit 35 ... Distance measuring area order setting unit 36... Reliability evaluation unit 37 37 Defocus amount calculation unit / reliability evaluation unit 38. Distance measuring point determination unit Fc. ... Slope of correlation value, S ... Subject, ZR ... Shift amount, d ... Defocus amount

Claims (4)

A plurality of pixels having a photoelectric conversion unit that converts an optical image formed by the imaging optical system into an electric signal, and the plurality of pixels are configured to limit an incident direction of a light beam incident on the pixels. An image sensor including a detection pixel and an image pickup pixel configured such that a light beam incident on the pixel is not limited as compared with the focus detection pixel, and the image pickup element includes a plurality of pixels arranged in a two-dimensional manner. In the imaging device,
Subject-of-interest detection means for detecting the position of the subject of interest based on the pixel signal output from the image sensor;
Distance measuring point setting means for setting a plurality of distance measuring points corresponding to the position of the focus detection pixel based on the position of the subject of interest;
A computing means for computing a plurality of defocus amounts based on outputs of the focus detection pixels corresponding to the plurality of distance measuring points;
Priority order determining means for determining the priority order of the set distance measuring points;
Reliability determination means for determining the reliability of the defocus amount detected corresponding to the set ranging point;
Selection means for selecting a distance measuring point from among the plurality of distance measuring points set based on the output of the priority determining means and the output of the reliability determining means;
Have
The noted subject detection means detects an area corresponding to a face,
The ranging point setting means arranges the ranging points more densely in a specific area inside the area corresponding to the face than in other areas corresponding to the face .
An imaging apparatus characterized by that.   The imaging apparatus according to claim 1, wherein the priority order determination unit increases a priority order of a distance measuring point that is closer to a specific position of the subject of interest among the plurality of distance measuring points. The reliability determination means outputs a reliability evaluation value indicating the reliability of the defocus amount,
The selection means selects the distance measurement points based on the priority order of the plurality of distance measurement points determined by the priority order determination means and the result of weighting the reliability evaluation value output by the reliability determination means. The imaging apparatus according to claim 1, wherein the imaging apparatus is characterized. The noted subject detection means detects a region corresponding to a facial organ,
The ranging point setting means arranges the ranging points more densely in the area corresponding to the organ than in the area not corresponding to the organ.
The imaging apparatus according to any one of claims 1 to 3, wherein

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