JP2021051322A - Focusing state detection device and camera - Google Patents

Abstract

To provide a focusing state detection device capable of suitably detecting a focusing state, and a camera.SOLUTION: The focusing state detection device comprises: an image sensor that has a plurality of regions in an imaging plane to capture images formed by optical systems, the plurality of regions for detecting a focusing state of the images and the imaging plane, each region including a plurality of pixel arrays, and each pixel array having a first pixel receiving light passing through a first region of the optical system to output a signal and a second pixel receiving light passing through a second region of the optical system to output a signal; and a detection unit for detecting the focusing state based on the signals output from the pixel arrays in a smaller number than the number of the pixel arrays arranged in one region of the plurality of regions.SELECTED DRAWING: Figure 3

Description

The present invention relates to an in-focus state detection device and a camera.

Conventionally, in a focus detection device provided with a plurality of light receiving element groups, a defocus amount is calculated for each of the plurality of light receiving element groups, and one defocus amount is selected from the calculated plurality of defocus amounts. A technique for performing focus detection based on a selected defocus amount is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2003-215437

An object to be solved by the present invention is to provide a focusing state detecting device and a camera capable of suitably detecting a focusing state.

The present invention solves the above problems by the following solutions.

[1] The in-focus state detection device according to the present invention has a plurality of regions for detecting the in-focus state between the image and the image pickup surface on the image pickup surface for capturing the image formed by the optical system. Each of the regions is a first pixel that receives light passing through the first region of the optical system and outputs a signal, and a second pixel that receives light passing through a second region of the optical system and outputs a signal. An image sensor in which a plurality of pixel rows having the above are arranged, and a pixel array having a number smaller than the number of the arranged pixel rows among the pixel rows arranged in one of the plurality of regions. It is characterized by including a detection unit that detects the in-focus state based on the signal output from.
[2] In the in-focus state detection device, the detection unit is configured to detect the in-focus state based on one of the pixel rows arranged in a plurality of rows in the region. can do.
[3] In the in-focus state detection device, the detection unit uses the pixels for detecting the in-focus state based on the signals output from the pixel rows arranged in a plurality of rows in one of the regions. It can be configured to select columns.
[4] In the in-focus state detection device, the detection unit detects the in-focus state based on the contrast of the signals output from the pixel rows arranged in a plurality of rows in one of the regions. It can be configured to select a pixel sequence.
[5] In the in-focus state detection device, the detection unit can be configured to detect a value based on the amount of deviation between the image formed by the optical system and the imaging surface as the in-focus state. ..
[6] In the in-focus state detection device, the optical system has a lens that moves in the optical axis direction of the optical system, and the detection unit has an image formed by the optical system as the in-focus state and the above. It can be configured to detect a value related to the amount of movement of the lens calculated based on the amount of deviation from the imaging surface.
[7] In the focusing state detection device, the image sensor is instructed to perform a plurality of imagings at the same time interval, and the movement of the movement amount detected by the detection unit is performed at the same time interval as the time interval. It can be configured to instruct the lens.
[8] The focusing state detection device has an operation instruction unit that gives an instruction to execute the movement of the lens based on the detection of the detection unit by operating the control unit, and the control unit is the operation instruction unit. This can be configured to repeat the movement instruction based on the value related to the movement amount of the lens at the time interval while the instruction to execute the movement of the lens is given.
[9] The camera according to the present invention has the above-mentioned in-focus state detection device.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a front view showing an image pickup surface of the image pickup device shown in FIG. FIG. 3 is a front view schematically showing the arrangement of the image pickup pixel 221 and the focus detection pixels 222a and 222b by enlarging part III of FIG. 4 (A) is an enlarged front view showing one of the imaging pixels 221 and FIG. 4 (B) is an enlarged front view showing one of the first focus detection pixels 222a, FIG. 4 (C). Is an enlarged front view showing one of the second focus detection pixels 222b, FIG. 4 (D) is an enlarged cross-sectional view showing one of the imaging pixels 221 and FIG. 4 (E) is the first focus. An enlarged cross-sectional view showing one of the detection pixels 222a, FIG. 4 (F) is an enlarged cross-sectional view showing one of the second focus detection pixels 222b. FIG. 5 is a cross-sectional view taken along the line VV of FIG. FIG. 6 is a flowchart showing the operation of the camera according to the first embodiment. FIG. 7 is a diagram for explaining an operation example of the camera 1 according to the present embodiment. FIG. 8 is a diagram for explaining an operation example of a conventional camera. FIG. 9 is a diagram schematically showing the arrangement of the first focus detection pixel 222a and the second focus detection pixel 222b according to the present embodiment. FIG. 10A is a graph showing the relationship between the correlation amount and the shift amount in the present embodiment, and FIG. 10B is a graph showing the relationship between the correlation amount and the shift amount in the prior art. FIG. 11 is a flowchart showing the operation of the camera according to the second embodiment. FIG. 12 is a diagram showing an example of a frequency component included in the output of the focus detection pixel sequence. FIG. 13 is a diagram for explaining a method of calculating contrast information in the third embodiment. FIG. 14 is a configuration diagram showing a camera according to a fourth embodiment. FIG. 15 is a configuration diagram showing the focus detection module shown in FIG. FIG. 16 is a front view showing an image pickup surface of the image pickup device shown in FIG. FIG. 17 is an enlarged front view showing one of the focus detection regions 224 shown in FIG. FIG. 18A is an enlarged front view showing one of the imaging pixels 221a, and FIG. 18B is a cross-sectional view. FIG. 19 is a cross-sectional view taken along the line XIX-XIX of FIG. FIG. 20 is an enlarged front view showing one of the focus detection regions 224 shown in FIG. FIG. 21 is a diagram for explaining a method of calculating contrast information in the fourth embodiment. FIG. 22 is a diagram showing an example of frequency components in each group. FIG. 23 is a flowchart showing the operation of the camera according to the fourth embodiment. FIG. 24 is a diagram for explaining a method of calculating contrast information in the fifth embodiment. FIG. 25 is a flowchart showing the operation of the camera according to the fifth embodiment. FIG. 26 is a front view schematically showing an arrangement of focus detection pixels 222a and 222b according to another embodiment. FIG. 27 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b according to another embodiment. FIG. 28 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b according to still another embodiment.

Hereinafter, embodiments will be described with reference to the drawings.

<< First Embodiment >>
FIG. 1 is a configuration diagram of a main part showing a digital camera 1 according to an embodiment. The digital camera 1 of the present embodiment (hereinafter, simply referred to as a camera 1) is composed of a camera body 2 and a lens barrel 3, and the camera body 2 and the lens barrel 3 are detachably connected by a mount portion 4. There is.

The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. As shown in FIG. 1, the lens barrel 3 has a built-in photographing optical system including lenses 31, 32, 33, and an aperture 34.

The lens 32 is a focus lens, and the focal state of the photographing optical system can be adjusted by moving in the optical axis L1 direction. The focus lens 32 is movably provided along the optical axis L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 36 while its position is detected by the encoder 35.

The aperture 34 is configured so that the aperture diameter centered on the optical axis L1 can be adjusted in order to limit the amount of light of the light flux passing through the photographing optical system and reaching the image sensor 22 and to adjust the amount of blurring. The aperture diameter is adjusted by the aperture 34, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by a manual operation by the operation unit 28 provided on the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture aperture sensor (not shown), and the lens control unit 37 recognizes the current aperture diameter.

The lens control unit 37 executes control of the entire lens barrel 3 such as driving the focus lens 32 and adjusting the aperture diameter by the aperture 34 based on a command from the camera control unit 21.

On the other hand, the camera body 2 is provided with an image pickup element 22 that receives a light beam from the photographing optical system on the planned focal plane of the photographing optical system, and a shutter 23 is provided on the front surface thereof. The image sensor 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electric signal, and sends it to the camera control unit 21. The captured image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder (EVF) 26 of the observation optical system, and the release button (release button) provided on the operation unit 28. When (not shown) is fully pressed, the captured image information is recorded in the memory 24 which is a recording medium. As the memory 24, either a removable card type memory or a built-in type memory can be used. The details of the structure of the image sensor 22 will be described later.

The camera body 2 is provided with an observation optical system for observing the image captured by the image sensor 22. The observation optical system of the present embodiment includes an electronic viewfinder (EVF) 26 composed of a liquid crystal display element, a liquid crystal drive circuit 25 for driving the electronic viewfinder (EVF) 26, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the captured image information captured by the image sensor 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on the captured image information. This allows the user to observe the current captured image through the eyepiece 27. Instead of or in addition to the observation optical system based on the optical axis L2, a liquid crystal display may be provided on the back surface of the camera body 2 or the like, and a photographed image may be displayed on the liquid crystal display.

The camera body 2 is provided with a camera control unit 21. The camera control unit 21 receives various lens information and transmits information such as the defocus amount and the aperture aperture diameter to the lens control unit 37. Further, the camera control unit 21 reads the pixel output from the image sensor 22 as described above, and generates image information by performing predetermined information processing on the read pixel output as necessary, and the generated image information. Is output to the liquid crystal drive circuit 25 and the memory 24 of the electronic viewfinder 26. Further, the camera control unit 21 controls the entire camera 1 by correcting the image information from the image sensor 22, detecting the focus adjustment state and the aperture adjustment state of the lens barrel 3, and the like.

In addition to the above, the camera control unit 21 detects the focal state of the photographing optical system by the phase detection method and detects the focal state of the photographing optical system by the contrast detection method based on the pixel data read from the image pickup element 22. I do. A specific method for detecting the focal state will be described later.

The operation unit 28 is an input switch such as a shutter release button for the photographer to set various operation modes of the camera 1, and can switch between the autofocus mode and the manual focus mode. Various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21. Further, the shutter release button includes a first switch SW1 that is turned on when the button is half-pressed, and a second switch SW2 that is turned on when the button is fully pressed.

Next, the image pickup device 22 according to the present embodiment will be described.

FIG. 2 is a front view showing the image pickup surface of the image pickup device 22, and FIG. 3 is a front view schematically showing the arrangement of the image pickup pixels 221 and the focus detection pixels 222a and 222b by enlarging part III of FIG.

In the image pickup device 22 of the present embodiment, as shown in FIG. 3, a plurality of image pickup pixels 221 are arranged two-dimensionally on a plane of an image pickup surface, and a green pixel G having a color filter that transmits a green wavelength region is provided. A red pixel R having a color filter that transmits a red wavelength region and a blue pixel B having a color filter that transmits a blue wavelength region are arranged in a so-called Bayer Arrangement. That is, in the four adjacent pixel groups 223 (dense square grid array), two green pixels are arranged on one diagonal line, and one red pixel and one blue pixel are arranged on the other diagonal line. The image pickup device 22 is configured by repeatedly arranging the pixel group 223 on the image pickup surface of the image pickup device 22 in a two-dimensional manner with the Bayer-arranged pixel group 223 as a unit. In this embodiment, one pixel is composed of the four pixel groups 223.

The array of the unit pixel group 223 may be, for example, a dense hexagonal lattice array in addition to the dense square lattice shown in the figure. Further, the configuration and arrangement of the color filters are not limited to this, and an arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) can be adopted.

FIG. 4A is an enlarged front view showing one of the imaging pixels 221 and FIG. 4D is a cross-sectional view. One image pickup pixel 221 is composed of a microlens 2211, a photoelectric conversion unit 2212, and a color filter (not shown), and is formed on the surface of the semiconductor circuit board 2213 of the image pickup element 22 as shown in the cross-sectional view of FIG. 4 (D). A photoelectric conversion unit 2212 is built in, and a microlens 2211 is formed on the surface thereof. The photoelectric conversion unit 2212 is shaped to receive an imaging light beam passing through the exit pupil (for example, F1.0) of the photographing optical system 31 by the microlens 2211, and receives the imaging light beam.

Further, as shown in FIG. 2, the center of the image pickup surface of the image pickup element 22, the symmetrical position from the center, and the vertically symmetrical position thereof, a total of nine positions, instead of the above-mentioned image pickup pixel 221, focus detection pixels. Focus detection pixel sequence groups 22a to 22i in which 222a and 222b are arranged are provided. Then, as shown in FIG. 3, each focus detection pixel array group is composed of four focus detection pixel sequences L1 to L4, and each focus detection pixel array L1 to L4 includes a plurality of first focus detection pixel sequences 222a. And the second focus detection pixels 222b are arranged adjacent to each other and alternately arranged in a horizontal row. Further, as shown in FIG. 3, in the present embodiment, in the focus detection pixel sequences L1 and L3 and the focus detection pixel sequences L2 and L4, the focus detection pixels 222a and the focus detection pixels 222b are reversed in the X-axis direction. Is located in. Further, in the present embodiment, as shown in FIG. 3, the first focus detection pixel 222a and the second focus detection pixel 222b have a gap between the green pixel G and the blue pixel B of the Bayer-arranged image pickup pixel 221. It is densely arranged without being provided.

The positions of the focus detection pixel train groups 22a to 22i shown in FIG. 2 are not limited to the positions shown in the drawing, and may be any one or 2 to 8 positions, and may be arranged at 10 or more positions. You can also do it. Further, in the actual focus detection, the photographer manually operates the operation unit 28 to adjust the focus of the desired focus detection pixel group from the plurality of focus detection pixel groups 22a to 22i arranged. It can also be selected as the focus detection area AFP of.

FIG. 4B is an enlarged front view showing one of the first focus detection pixels 222a, and FIG. 4E is a cross-sectional view of the first focus detection pixel 222a. Further, FIG. 4C is an enlarged front view showing one of the second focus detection pixels 222b, and FIG. 4F is a cross-sectional view of the second focus detection pixel 222b. As shown in FIG. 4B, the first focus detection pixel 222a is composed of a microlens 2221a and a rectangular photoelectric conversion unit 2222a, and is an imaging element as shown in the cross-sectional view of FIG. 4E. A photoelectric conversion unit 2222a is built on the surface of the semiconductor circuit board 2213 of 22, and a microlens 2221a is formed on the surface thereof. Further, the second focus detection pixel 222b is composed of a microlens 2221b and a photoelectric conversion unit 2222b as shown in FIG. 4C, and is composed of an imaging element 22 as shown in a cross-sectional view of FIG. 4F. A photoelectric conversion unit 2222b is built on the surface of the semiconductor circuit board 2213, and a microlens 2221b is formed on the surface thereof. Then, as shown in FIG. 3, these focus detection pixels 222a and 222b are arranged adjacent to each other in a horizontal row alternately to form the focus detection pixel rows L1 to L4.

The photoelectric conversion units 2222a and 2222b of the first focus detection pixel 222a and the second focus detection pixel 222b are light fluxes that pass through a predetermined region (for example, F2.8) of the exit pupil of the photographing optical system by the microlenses 2221a and 2221b. It is shaped to receive light. Further, the first focus detection pixel 222a and the second focus detection pixel 222b are not provided with a color filter, and their spectral characteristics are the spectral characteristics of a photodiode that performs photoelectric conversion and the spectroscopy of an infrared cut filter (not shown). It is a comprehensive version of the characteristics. However, it may be configured to include one of the same color filters as the imaging pixel 221, for example, a green filter.

Further, although the photoelectric conversion units 2222a and 2222b of the first focus detection pixel 222a and the second focus detection pixel 222b shown in FIGS. 4 (B) and 4 (C) are rectangular, the shapes of the photoelectric conversion units 2222a and 2222b are formed. Is not limited to this, and other shapes such as a semicircular shape, an elliptical shape, and a polygonal shape can be used.

Next, a so-called phase difference detection method for detecting the focal state of the photographing optical system based on the pixel outputs of the focal detection pixels 222a and 222b described above will be described.

FIG. 5 is a cross-sectional view taken along the line VV of FIG. 3, in which focus detection pixels 222a-1,222b-1,222a-2, 222b-2 arranged in the vicinity of the photographing optical axis L1 and adjacent to each other are arranged. It is shown that the light fluxes AB1-1, AB2-1, AB1-2, and AB2-2 emitted from the distance measuring pupils 351 and 352 of the exit pupil 350 are received, respectively. Note that, in FIG. 5, of the plurality of focus detection pixels 222a and 222b, only those located near the photographing optical axis L1 are shown as an example, but other focus detection pixels other than the focus detection pixels shown in FIG. 5 are shown. Similarly, the light beam emitted from the pair of ranging pupils 351 and 352 is also configured to receive light.

Here, the exit pupil 350 is an image set at a distance D in front of the microlenses 2221a and 2221b of the focus detection pixels 222a and 222b arranged on the planned focal plane of the photographing optical system. The distance D is a value uniquely determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and the like, and this distance D is referred to as a distance measuring pupil distance. Further, the distance measuring pupils 351 and 352 refer to images of the photoelectric conversion units 2222a and 2222b projected by the microlenses 2221a and 2221b of the focus detection pixels 222a and 222b, respectively.

In FIG. 5, the arrangement directions of the focus detection pixels 222a-1,222b-1,222a-2, 222b-2 coincide with the arrangement directions of the pair of ranging pupils 351 and 352.

Further, as shown in FIG. 5, the microlenses 2221a-1,2221b-1,2221a-2, 2221b-2 of the focus detection pixels 222a-1,222b-1,222a-2, 222b-2 are the photographing optical systems. It is located near the planned focal plane of. Then, the shapes of the photoelectric conversion units 2222a-1,2222b-1,2222a-2, 2222b-2 arranged behind the microlenses 2221a-1,221b-1,2221a-2, 2221b-2 are microscopic. It is projected onto the exit pupil 350, which is separated by the distance measurement distance D from the lenses 2221a-1,221b-1,2221a-2, 2221b-2, and the projected shape forms the distance measurement pupils 351 and 352.

That is, the microlens and the photoelectric conversion unit in each focus detection pixel match so that the projection shapes (distance measurement pupils 351 and 352) of the photoelectric conversion unit of each focus detection pixel match on the ejection pupil 350 at the distance measurement distance D. The relative positional relationship between the two is determined, and the projection direction of the photoelectric conversion unit in each focus detection pixel is determined accordingly.

As shown in FIG. 5, the photoelectric conversion unit 2222a-1 of the first focus detection pixel 222a-1 passes through the ranging pupil 351 and is on the microlens 2221a-1 by the luminous flux AB1-1 toward the microlens 2221a-1. Outputs a signal corresponding to the intensity of the image formed in. Similarly, the photoelectric conversion unit 2222a-2 of the first focus detection pixel 222a-2 passes through the ranging pupil 351 and is formed on the microlens 2221a-2 by the luminous flux AB1-2 toward the microlens 2221a-2. Outputs a signal corresponding to the intensity of.

Further, the photoelectric conversion unit 2222b-1 of the second focus detection pixel 222b-1 passes through the ranging pupil 352, and the image formed on the microlens 2221b-1 by the luminous flux AB2-1 toward the microlens 2221b-1. Outputs a signal corresponding to the intensity. Similarly, the photoelectric conversion unit 2222b-2 of the second focus detection pixel 222b-2 passes through the ranging pupil 352 and is formed on the microlens 2221b-2 by the luminous flux AB2-2 directed toward the microlens 2221b-2. Outputs a signal corresponding to the intensity of.

Then, by grouping the outputs of the photoelectric conversion units 2222a and 2222b of the focal detection pixels 222a and 222b described above into output groups corresponding to the distance measuring pupil 351 and the distance measuring pupil 352, the distance measuring pupil 351 and the distance measuring pupil 351 and the distance measuring pupil 351 Data on the intensity distribution of a pair of images formed on the focus detection pixel sequence by the focus detection light flux passing through each of the pupils 352 is obtained.

Then, the camera control unit 21 obtains a data string relating to the intensity distribution of the pair of images, that is, a data string based on the first focus detection pixel 222a and a data string based on the second focus detection pixel 222b among the focus detection pixel strings. , Perform the correlation calculation shown in the following equation (1) while shifting relative to one dimension.
C (k) = Σ | I _{A (n + k)} -IB _(n) | ... (1)
In the above equation (1), the Σ operation indicates a cumulative operation (sum operation) for n, and is limited to the range in which the data of _{IA (n + k)} and IB _{(n) exist according to the image shift amount k.} Will be done. Further, the image shift amount k is an integer, and is a shift amount in units of the pixel intervals of the focus detection pixels 222a and 222b. In the calculation result of the above equation (1), the correlation amount C (k) becomes the minimum (the smaller the correlation, the higher the degree of correlation) in the shift amount in which the correlation between the pair of image data is high.

Then, the correlation amount C (k) is calculated according to the above equation (1), and the defocus amount df is calculated according to the following equation (2) based on the shift amount x at which the minimum value C (x) of the correlation amount is obtained. Is calculated. In the above equation (2), k is a conversion coefficient (k factor) for converting the shift amount x at which the minimum value C (x) of the correlation amount is obtained into the defocus amount.
df = x · k… (2)

Further, in the present embodiment, the camera control unit 21 detects contrast information from the outputs of the plurality of focus detection pixel sequences L1 to L4, and based on the detected contrast information, the focus detection pixels used for calculating the defocus amount. The row is determined as a specific focus detection pixel row.

Specifically, the camera control unit 21 acquires the output of each focus detection pixel sequence L1 to L4 from the image sensor 22, and filters the acquired output of the focus detection pixel sequence L1 to L4 with a high-frequency transmission filter. Then, the high frequency component is extracted from the output of the focus detection pixel strings L1 to L4. Then, the camera control unit 21 compares the high-frequency components of each focus detection pixel sequence L1 to L4, and based on the comparison result, corresponds to the subject having the highest contrast among the plurality of focus detection pixel sequences L1 to L4. The focus detection pixel string is determined as a specific focus detection pixel string. Further, the camera control unit 21 determines, among the plurality of focus detection pixel sequences L1 to L4, the focus detection pixel sequence in which the output contains the largest number of high-frequency components as the specific focus detection pixel sequence, based on the above comparison result. It may be configured.

In the present embodiment, the camera control unit 21 acquires the outputs of the plurality of focus detection pixel trains L1 to L4 from the image pickup element 22, thereby detecting the specific focus from the plurality of focus detection pixel trains L1 to L4. Although the configuration for determining the pixel sequence has been described as an example, the present invention is not limited to this configuration, and for example, the point detection pixel array is based on the output of each focus detection pixel array L1 to L4 by the arithmetic unit included in the image pickup element 22. Contrast information is detected for each of L1 to L4, and a specific focus detection pixel string is determined from a plurality of focus detection pixel sequences L1 to L4 based on the detected contrast information. The information may be transmitted to the camera control unit 21.

Then, the camera control unit 21 calculates the defocus amount based on the output of the determined specific focus detection pixel string. As described above, in the present embodiment, the defocus amount is calculated based only on the output of the focus detection pixel row determined as the specific focus output pixel row among the plurality of focus detection pixel rows L1 to L4. , The time required to calculate the defocus amount can be shortened.

That is, conventionally, when there are a plurality of focus detection pixel strings, the defocus amount is calculated for all the focus detection pixel strings, and the defocus amount used for driving the focus lens 32 is used from the calculated plurality of defocus amounts. The focus amount was selected. Therefore, conventionally, not only the calculation for the defocus amount other than the selected defocus amount is wasted, but also the defocus amount is calculated for all of the plurality of focus detection pixel strings L1 to L4, so that the defocus amount is calculated. There was a problem that the calculation time of was long. On the other hand, in the present embodiment, the defocus amount is calculated based only on the output of the focus detection pixel string determined as the specific focus output pixel string, so that the time required for calculating the defocus amount is shortened. As a result, the time required for focus detection can be reduced.

In the present embodiment, a plurality of focus detection areas AFP are set in the shooting screen of the shooting optical system corresponding to the focus detection pixel sequence groups 22a to 22i of the image sensor 22, and the photographer operates. The focus detection area AFP used for focus adjustment can be set via the unit 28. For example, when the photographer selects the focus detection area AFP corresponding to the focus detection pixel group 22a as the focus detection area AFP used for focus adjustment, the camera control unit 21 is included in the focus detection pixel group 22a. The defocus amount is calculated based on the outputs of the focus detection pixel strings L1 to L4. Further, the method of setting the focus detection area AFP is not limited to the method selected by the photographer. For example, the camera control unit 21 performs face recognition processing based on the image data output from the image sensor 22. The focus detection area AFP corresponding to the face of the subject may be set as the focus detection area AFP used for focus adjustment. Alternatively, the output of the focus detection pixel strings L1 to L4 in all the focus detection areas AFP set in the shooting screen is acquired, and the focus used for focus adjustment is used based on the acquired output of the focus detection pixel strings L1 to L4. The detection area AFP may be set.

Further, in the present embodiment, the camera control unit 21 also performs focus detection by the contrast detection method in addition to the focus detection by the phase difference detection method described above. Specifically, the camera control unit 21 reads out the output of the image pickup pixel 221 of the image pickup element 22, and calculates the focus evaluation value based on the read pixel output. This focus evaluation value can be obtained, for example, by extracting the high-frequency component of the image output from the image pickup pixel 221 of the image pickup device 22 using a high-frequency transmission filter and integrating the high-frequency components. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies and integrating each of them.

Then, the camera control unit 21 sends a control signal to the lens control unit 37 to drive the focus lens 32 at a predetermined sampling interval (distance), obtains a focus evaluation value at each position, and the focus evaluation value is the maximum. The position of the focus lens 32 is obtained as the focusing position. It should be noted that this focusing position is determined when, for example, when the focus evaluation value is calculated while driving the focus lens 32, the focus evaluation value increases twice and then decreases twice. It can be obtained by performing an operation such as an interpolation method using the focus evaluation value of.

Next, an operation example of the camera 1 in this embodiment will be described with reference to the flowchart shown in FIG.

First, in step S101, the image sensor 22 acquires the output data of the image pickup pixels 221 and the first focus detection pixels 222a and the second focus detection pixels 222b constituting the plurality of focus detection pixel rows L1 to L4. ..

In step S102, the camera control unit 21 selects the focus detection area AFP for use in focus adjustment. For example, when the photographer sets the focus detection area AFP used for focus adjustment via the operation unit 28, the camera control unit 21 uses the focus detection area AFP set by the photographer for the focus adjustment. It can be selected as the detection area AFP. Further, the camera control unit 21 performs face recognition processing on the image data output from the image sensor 22, and uses the focus detection area AFP corresponding to the face of the subject as the focus detection area AFP used for focus adjustment. It may be a configuration to be selected. Alternatively, the camera control unit 21 selects the focus detection area AFP used for focus adjustment by analyzing the outputs of the focus detection pixel strings L1 to L4 of all the focus detection areas AFP set in the shooting screen. May be.

In step S103, the camera control unit 21 detects the contrast information for each focus detection pixel sequence L1 to L4 based on the output of each focus detection pixel sequence L1 to L4. Specifically, the camera control unit 21 filters the outputs of the plurality of focus detection pixel sequences L1 to L4 corresponding to the focus detection area AFP selected in step S102 by a high-frequency transmission filter, thereby performing the focus detection pixel array. High frequency components are extracted from the pixel outputs of L1 to L4. Then, the camera control unit 21 detects information including the amount and intensity of the extracted high-frequency component for each focus detection pixel sequence L1 to L4 as contrast information.

In step S104, the camera control unit 21 determines the specific focus detection pixel sequence. Specifically, the camera control unit 21 corresponds to the subject having the highest contrast among the plurality of focus detection pixel rows L1 to L4, based on the contrast information for each focus detection pixel train L1 to L4 detected in step S103. The focus detection pixel string to be used or the focus detection pixel string in which the pixel output contains the largest amount of high-frequency components is determined as the specific focus detection pixel string.

Then, in step S105, the camera control unit 21 calculates the defocus amount based on the output of the specific focus detection pixel string determined in step S104. Then, in step S106, the drive amount of the focus lens 32 is calculated and the focus lens 32 is driven based on the defocus amount calculated in step S105.

As described above, the focus detection of the optical system according to the first embodiment is performed.

Next, an operation example of the camera 1 according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram for explaining an operation example of the camera 1 according to the present embodiment. Further, in FIG. 7, time is shown on the horizontal axis, and a scene in which the shutter release button is half-pressed at time t5 is shown. For example, in the example shown in FIG. 7, at time t1, the focus detection pixels 222a and 222b of the image sensor 22 start accumulating charges according to the incident light. Further, in the present embodiment, the focus detection pixels 222a and 222b are, for example, CMOS image sensors, and in parallel with the accumulation of electric charges, the transfer of pixel signals according to the amount of electric charges accumulated after time t1 is started. To. Then, at time t3, the transfer of the pixel signal started at time t2 is completed, and the contrast information is detected and the specific focus detection pixel sequence is determined (steps S103 and S104). Then, at time t4, the calculation of the defocus amount is started based on the output of the determined specific focus detection pixel string (step S105). As a result, the lens drive amount is calculated, and after the lens drive amount is calculated, the lens drive instruction is transmitted to the lens barrel 3 at time t6, and the focus lens 32 is driven. Here, in the example shown in FIG. 7, since the shutter release button is half-pressed at the time t5 before the lens drive instruction is given, the focus lens 32 is based on the lens drive instruction at the time t6. Is started to drive.

Further, in the present embodiment, even after the shutter release button is pressed halfway, the defocus amount is repeatedly calculated according to the frame rate of the image sensor 22, and the focus lens is based on the calculated defocus amount. The drive instruction of 32 is repeated. For example, in the example shown in FIG. 7, the accumulation of the charge in the second frame is started at time t2, and as a result, the defocus amount in the second frame is calculated at time t7, and the defocus amount in the second frame is calculated at time t8. The drive instruction of the focus lens 32 is given based on the output results of the focus detection pixel strings L1 to L4 of the eye. Similarly, in the third and subsequent frames as well, the calculation of the defocus amount and the driving of the focus lens 32 based on the defocus amount are repeated for each frame based on the outputs of the focus detection pixel strings L1 to L4.

As described above, in the present embodiment, the calculation of the defocus amount and the driving of the focus lens 32 based on the defocus amount are repeated for each frame according to the frame rate of the image sensor 22. In this way, in order to calculate the defocus amount for each frame and instruct the drive of the focus lens 32, it is necessary to perform the process from the calculation of the defocus amount to the drive instruction of the focus lens 32 within the time of one frame. There is. In this regard, in the present embodiment, one specific focus detection pixel string is determined based on the contrast information, and the defocus amount is calculated only for the output of the specific focus detection pixel string, as shown in FIG. Since the time required for calculating the defocus amount can be shortened, the defocus amount can be calculated within one frame time, and the focus lens 32 can be driven based on the calculated defocus amount.

On the other hand, FIG. 8 is a diagram for explaining an operation example of a conventional camera, and like FIG. 7, time is shown on the horizontal axis. In the example shown in FIG. 8, since the calculation of the defocus amount, which takes a relatively long time, is performed for all the focus detection pixel strings L1 to L4, the calculation time of the defocus amount is compared with the present embodiment shown in FIG. become longer. As a result, in the example shown in FIG. 8, the time required from the calculation of the defocus amount to the lens drive instruction is longer than the time for one frame of the frame rate, as compared with the present embodiment shown in FIG. In some cases, it may not be possible to give lens drive instructions for each frame. Specifically, in the example shown in FIG. 8, since it is not possible to perform the defocus amount calculation and the lens drive instruction within the time for one frame, compared with the time lag T1 of the present embodiment shown in FIG. The time lag T2 from the accumulation of electric charge to the drive instruction of the focus lens 32 is doubled.

As a result, in the example shown in FIG. 8, at time 12, the drive of the focus lens 32 is instructed based on the focal state of the optical system at time t11, so that the focus lens 32 is far beyond the in-focus position. In some cases, it was driven, and in some cases, the ability to follow the subject was reduced. On the other hand, in the present embodiment, as shown in FIG. 7, the drive instruction of the focus lens 32 can be given at the time t10 with a small time lag based on the focal state of the optical system at the time t9. Compared with the conventional example shown in FIG. 8, the focus lens 32 can be appropriately driven to the in-focus position.

As described above, in the first embodiment, the contrast information is detected for each focus detection pixel sequence L1 to L4 based on the output of each focus detection pixel sequence L1 to L4 in the focus detection area AFP. Then, the focus detection pixel sequence used for focus detection is determined based on the detected contrast information. That is, among the plurality of focus detection pixel sequences L1 to L4, the focus detection pixel array corresponding to the subject having the highest contrast or the focus detection pixel array containing the largest amount of high-frequency components in the pixel output is detected as a specific focus. It is determined as a pixel string, and the defocus amount is determined only for this specific focus detection pixel string. As a result, it is possible to detect the focal state of the optical system for the subject having the highest contrast or the subject having the highest high-frequency component, and as in the conventional case, all of the plurality of focus detection pixel trains L1 to L4 are displayed. Compared with the case of calculating the focus amount, the time required for calculating the defocus amount can be shortened, and the focus state can be detected repeatedly at an appropriate timing.

Further, in the first embodiment, since the defocus amount is calculated based on the output of one focus detection pixel string among the outputs of the plurality of focus detection pixel sequences L1 to L4, a plurality of focus detection pixel sequences Compared with the case where the outputs of L1 to L4 are added or averaged, the following effects can be obtained. That is, when the subject has contrast in the oblique direction of the image pickup pixel 221 and the outputs of the plurality of focus detection pixel rows L1 to L4 are added or averaged, the contrast may rather decrease, and the subject may be affected. It may not be detected properly. On the other hand, in the present embodiment, since the defocus amount is calculated based on the output of one specific focus detection pixel string, even in such a case, it is possible to prevent a decrease in contrast and make the subject appropriate. It can have the effect of being able to detect.

<< Second Embodiment >>
Next, the second embodiment will be described. The second embodiment has the same configuration as that of the first embodiment described above, except that the camera 1 shown in FIG. 1 operates as described below.

In the second embodiment, the camera control unit 21 includes a plurality of filters that transmit frequency components of different frequency bands, and extracts frequency components of a plurality of different frequency bands from the outputs of the focus detection pixel strings L1 to L4. Then, based on the extracted plurality of frequency components, a plurality of contrast information is detected for each focus detection pixel sequence L1 to L4. For example, when the camera control unit 21 has three filters for extracting frequency components of three different frequency bands, the camera control unit 21 detects three contrast information from the output of one focus detection pixel string. can do. The frequency band of the frequency component extracted in the second embodiment is not particularly limited, and may be any frequency band from the low frequency band to the high frequency band.

Then, the camera control unit 21 selects one or a plurality of focus detection pixel trains L1 to L4 used for focus detection from the plurality of focus detection pixel trains L1 to L4 based on the plurality of contrast information. Detect as a column. For example, the camera control unit 21 selects one or a plurality of focus detection pixel sequences whose contrast magnitude of the corresponding subject is equal to or greater than a predetermined value from among the plurality of focus detection pixel sequences L1 to L4. Can be detected as. Alternatively, the camera control unit 21 can detect one or a plurality of focus detection pixel strings in which the amount of high frequency components contained in the output is equal to or greater than a predetermined value as a specific focus detection pixel string.

When the camera control unit 21 determines the specific focus detection pixel sequence, the number of the specific focus detection pixel strings is smaller than the number of the focus detection pixel sequences L1 to L4 corresponding to the focus detection area AFP. In addition, the specific focus detection pixel sequence is determined. For example, in the present embodiment, since the four focus detection pixel strings L1 to L4 are arranged in the focus detection area AFP, the camera control unit 21 has at least three or less specific focus detection pixel strings. In addition, the specific focus detection pixel sequence is determined.

Then, when the camera control unit 21 determines the plurality of focus detection pixel strings as the specific focus detection pixel strings, the camera control unit 21 adds or averages the outputs of the plurality of specific focus detection pixel strings, and adds or averages the outputs of the plurality of specific focus detection pixel strings. The defocus amount is calculated based on the output of the focus detection pixel string. Here, FIG. 9 shows only the first focus detection pixels 222a and the second focus detection pixels 222b constituting the four focus detection pixel trains L1 to L4, excluding the image pickup pixels 221 from the image pickup surface of the image pickup element 22 shown in FIG. Is a diagram schematically showing. For example, when adding the outputs of a plurality of specific focus detection pixel trains, the camera control unit 21 uses the output of pixels A1 _L1 of the first focus detection pixel train L1 shown in FIG. 9 and the same ranging pupil. receiving focus detection light fluxes passing through the output of the pixel _{A1 L2} of the second focus detection pixel row L2, the output of the pixel _{A1 L3} of the third focus detection pixel row L3, the pixels _{A1 L4} of the fourth focus detection pixel row L4 Is added to obtain the pixel addition output I _{A1. Similarly, the output of the pixel B1 L1} of the first focus detection pixel array L1 _{and the output of the pixel B1 L2} of the second focus detection pixel array L2 that receives the focus detection light beam passing through the same ranging pupil, and the first _{The output of the pixel B1 L3} of the three-focus detection pixel string L3 and the output of the pixel B1 _L4 of the fourth focus detection pixel string L4 are added to obtain the pixel addition output _IB1. Similarly, _{I A2} is obtained from the outputs of _{A2 L1} , A2 _L2 , A2 _L3, and A2 _{L4 , I B2} is obtained from the outputs of _{B2 L1} , B2 _L2 , B2 _L3, and B2 _{L4, and A3 L1} and A3 _L2 and A3. Obtain _{I A3} from the outputs of _L3 and A3 _{L4, and obtain I B3} from the outputs of B3 _L1 , B3 _L2 , B3 _L3, and B3 _L4.

Then, the camera control unit 21 uses the obtained pixel addition output to obtain a data sequence based on the first focus detection pixel 222a, that is, the first image data sequence I _A1 , I _A2 , I _A3 ,. .. .. , I _An and a data sequence based on the second focus detection pixel 222b, that is, the second image data sequence _IB1 , _IB2 , _IB3 ,. .. .. , _IBn are relatively shifted in a one-dimensional manner, and the correlation calculation shown in the above equation (1) is performed.

Here, as shown in FIG. 3, in the focus detection pixel trains L1 to L4, the first focus detection pixel 222a and the second focus detection pixel 222b are arranged at positions shifted by 0.5 pixels, respectively. There is. Conventionally, since only one of the first focus detection pixel string L1 and the second focus detection pixel string L2 of the present embodiment is used as the focus detection pixel string, the first focus detection pixel 222a and the first focus detection pixel string 222a. The two focus detection pixels 222b are located at positions offset by 0.5 pixels from each other, and the first image data sequences I _A1 , I _A2 , and I _A3 obtained by using these focus detection pixels ,. .. .. , I _An and the second image data sequence _IB1 , _IB2 , _IB3 ,. .. .. , _IBn are data that are 0.5 pixels out of alignment with each other. Therefore, when the correlation calculation is performed, as shown in FIG. 10B, the minimum value of the correlation amount C (k) is also shifted by 0.5 pixels. In such a case, in order to calculate the shift amount and the defocus amount at which the correlation amount C (k) shows the minimum value, it is necessary to use interpolation calculation or the like, and as a result, the focus detection accuracy is lowered. There was a case that it ended up. In particular, such a problem tends to become remarkable when the contrast level of the output detected by the focus detection pixel is low.

On the other hand, in the present embodiment, in the focus detection pixel rows L1 and L3 and the focus detection pixel rows L2 and L4, the first focus detection pixel 222a and the second focus detection pixel 222b are 0. Since they are arranged at positions shifted by 5 pixels, when the pixel addition output obtained by adding the pixel outputs is used, the focus state (defocus amount is zero) as shown in FIG. 10 (A). The shift amount that gives the minimum value of the correlation amount C (k) can be accurately obtained, and thus the focus detection accuracy can be appropriately improved.

Next, the operation of the camera 1 according to the second embodiment will be described with reference to FIG. FIG. 11 is a flowchart showing an operation example of the camera 1 according to the second embodiment.

In step S201, similarly to step S101 of the first embodiment, the image sensor 22 causes the image pickup pixels 221 and the first focus detection pixels 222a and the second focus detection pixels constituting the plurality of focus detection pixel rows L1 to L4. The output data of 222b is acquired. Further, in step S202, similarly to step S102 of the first embodiment, the camera control unit 21 selects the focus detection area AFP to be used for focus adjustment.

Then, in step S203, the camera control unit 21 detects the contrast information. In the second embodiment, the camera control unit 21 filters the outputs of the focus detection pixel sequences L1 to L4 by using a plurality of filters that extract frequency components in different frequency bands, so that each focus detection pixel A plurality of frequency components are extracted from each output of columns L1 to L4. Then, the camera control unit 21 detects information including the amount and intensity of the extracted frequency component as contrast information.

In step S204, the camera control unit 21 determines the specific focus detection pixel sequence based on the plurality of contrast information detected in step S203. Specifically, the camera control unit 21 has one or a plurality of focal points in which the contrast of the corresponding subject is equal to or higher than a predetermined value among the plurality of focus detection pixel sequences L1 to L4 based on the contrast information detected in step S203. The detection pixel string is determined as the specific focus detection pixel string. Alternatively, the camera control unit 21 may use one or more of the plurality of focus detection pixel sequences L1 to L4 in which the amount of high frequency components contained in the output is equal to or greater than a predetermined value based on the plurality of contrast information detected in step S203. The focus detection pixel sequence of is determined as a specific focus detection pixel sequence.

Then, in step S205, the camera control unit 21 calculates the defocus amount used for driving the focus lens 32 based on one or a plurality of specific focus detection pixel sequences determined in step S204. For example, when the camera control unit 21 determines a plurality of focus detection pixel strings as specific focus detection pixel strings, the camera control unit 21 calculates the output of 1 by adding or averaging the outputs of the plurality of specific focus detection pixel strings. Then, based on this output, the amount of defocus used to drive the focus lens 32 can be calculated.

In step S206, similarly to step S106 of the first embodiment, the drive amount of the focus lens 32 is calculated and the focus lens 32 is driven based on the defocus amount calculated in step S205.

As described above, the focus detection of the optical system according to the second embodiment is performed.

As described above, in the second embodiment, the frequency components of different frequency bands are extracted for each of the focus detection pixel strings L1 to L4 based on the outputs of the focus detection pixel strings L1 to L4, and the extracted frequency components are combined with the extracted frequency components. Based on this, multiple contrast information is detected. Then, one or a plurality of specific focus detection pixel strings are determined from the focus detection pixel sequences L1 to L4 based on the plurality of contrast information, and defocus is performed based on the pixel output of the determined specific focus detection pixel strings. Determine the amount. As described above, in the second embodiment, the defocus amount is not calculated for all the focus detection pixel sequences L1 to L4, but for a number of specific focus detection pixel sequences smaller than the number of the focus detection pixel sequences L1 to L4. By calculating the defocus amount, the calculation time of the defocus amount can be shortened, and as a result, the detection of the focus state can be repeatedly performed at an appropriate timing.

<< Third Embodiment >>
Next, the third embodiment will be described. The third embodiment has the same configuration as that of the first embodiment described above, except that the camera 1 shown in FIG. 1 operates as described below.

In the third embodiment, the camera control unit 21 uses a predetermined bandpass filter for the outputs of the focus detection pixel strings L1 to L4 acquired from the image sensor 22 when detecting the focal state of the optical system. By performing the filter processing, the frequency component corresponding to the subject is extracted from the outputs of the focus detection pixel strings L1 to L4. For example, the camera control unit 21 converts the outputs of the focus detection pixel strings L1 to L4 by using the Fourier transform, so that the frequency components included in the outputs of the focus detection pixel strings L1 to L4 can be used as a background or the like. The low frequency component caused by the noise and the high frequency component corresponding to noise are removed, and the frequency component corresponding to the subject is extracted. Then, as shown in FIG. 12, the camera control unit 21 uses the data obtained by filtering the outputs of the focus detection pixel trains L1 to L4 as the frequency components included in the outputs of the focus detection pixel trains L1 to L4. It is detected as the contrast information to be represented. Note that FIG. 12 is a graph showing an example of frequency components extracted from the outputs of the focus detection pixel strings L1 to L4.

Further, the camera control unit 21 obtains the sum of the differences in the continuous output values of the detected frequency components based on the contrast information of the detected frequency components, so that the frequency components included in the outputs of the focus detection pixel strings L1 to L4 are included. Information indicating the amount and intensity of the frequency component is calculated as the contrast amount of the frequency component. Specifically, the camera control unit 21 calculates the contrast amount of the frequency component based on the following equation (3).
Contrast amount = Σ | a _m- a _m-1 | ... (3)
In the above formula (3), a _m is, m-th (focus detection m-th in the arrangement direction of pixel columns) focus detection pixels located 222a, the output value of the frequency component corresponding to the output of 222b, a _m-1 is an output value of a frequency component corresponding to the output of the focus detection pixels 222a and 222b located at the m-1st position.

That is, the outputs of the focus detection pixel strings L1 to L4 are column data composed of the outputs of the plurality of focus detection pixels 222a and 222b arranged in the horizontal direction (X direction), and are the output of the focus detection pixel strings L1 to L4. As shown in FIG. 12, the frequency component included in the output also has output values corresponding to the outputs of the focus detection pixels 222a and 222b constituting the focus detection pixel sequences L1 to L4, respectively. Therefore, as shown in the above equation (3), the camera control unit 21 sets the output value of the frequency component corresponding to the output of the focus detection pixels 222a and 222b located second in the focus detection pixel trains L1 to L4 and 1 The difference from the output value of the frequency component corresponding to the output of the focus detection pixels 222a and 222b located at the second position can be calculated, and similarly, the output of the frequency component corresponding to the output of the continuous focus detection pixels 222a and 222b can be calculated. value a _m, a _m-1 can be calculated difference _(hereinafter also referred to as output value continuously in the frequency components). Then, by obtaining the sum of the output values a _m, a difference of a _m-1 consecutive in the frequency components, it is possible to calculate the contrast of the frequency components included in the output of the focus detection pixel row L1 to L4.

The contrast amount of the frequency component increases as the intensity (amplitude) of the frequency component increases, and increases as the amount (frequency) of the frequency component increases. For example, when the contrast of the subject corresponding to the focus detection pixel sequence is high and the intensity of the output value near the center of the frequency component becomes large as shown in FIG. 13 (A), as shown in FIG. 13 (B). In addition, the difference in continuous output values near the center of the frequency component also becomes large, and as a result, the contrast amount of the frequency component also becomes large. Further, as the amount of the frequency component increases (for example, in the example shown in FIG. 12, the focus detection pixel array L3 has a larger amount of the frequency component than the focus detection pixel array L1), the output value of the frequency component increases. Since the frequency of fluctuation increases, the contrast amount of the frequency component, which is the sum of the differences between the continuous output values in the frequency component, also increases. In this way, by calculating the sum of the differences between the continuous output values in the frequency component as the contrast amount of the frequency component, the contrast amount of the frequency component can be calculated as a value representing the amount and intensity of the frequency component. Note that FIG. 13A is a diagram showing an example of an output value of a frequency component included in the output of the focus detection pixel sequence, and FIG. 13B is a diagram showing the frequency component shown in FIG. 13A. It is a graph which shows the difference of the continuous output value.

In this way, the camera control unit 21 extracts predetermined frequency components corresponding to the subject from the outputs of the focus detection pixel strings L1 to L4, and sets the contrast amount of the extracted frequency components for each focus detection pixel sequence L1 to L4. Calculate to. Then, the camera control unit 21 determines the focus detection pixel sequence having the highest contrast amount among the focus detection pixel sequences L1 to L4 as the specific focus detection pixel sequence. For example, in the example shown in FIG. 12, among the focus detection pixel rows L1 to L4, the amount and intensity of the frequency component included in the output of the focus detection pixel row L3 are the largest, and as a result, the output of the focus detection pixel row L3 Since the contrast amount of the contained frequency component is the highest, the focus detection pixel string L3 is determined as the specific focus detection pixel string. Then, the camera control unit 21 calculates the defocus amount based on the output of the determined specific focus detection pixel string.

As described above, in the third embodiment, as shown in the above equation (3), the output values of the frequency components corresponding to the outputs of the focus detection pixels 222a and 222b continuous in the alignment direction in the focus detection pixel sequences L1 to L4. By calculating the sum of the differences as the contrast amount of the frequency components included in the outputs of the focus detection pixel trains L1 to L4, the contrast amount of the frequency components is appropriate according to the amount and intensity of the frequency components caused by the subject. Can be calculated in. Then, by calculating the defocus amount based on the output of the focus detection pixel string having the largest contrast amount, it is possible to perform focus detection based on the output of the focus detection pixel string that is likely to correspond to the subject. As a result, the focus adjustment state of the optical system with respect to the subject can be detected with higher accuracy.

<< Fourth Embodiment >>
Next, the fourth embodiment will be described. FIG. 14 is a diagram showing the configuration of the camera 1a according to the fourth embodiment. The fourth embodiment has the same configuration as that of the first embodiment described above, except that the camera 1a shown in FIG. 14 operates as described below.

First, the camera 1a according to the fourth embodiment will be described. The camera 1a has a camera body 2a and a lens barrel 3. The camera body 2a is a single-lens reflex digital camera, and includes an image sensor 220, an optical viewfinder 235, a photometric sensor 237, and a mirror system 250 for guiding a luminous flux from a subject to a focus detection module 261. The mirror system 250 includes a quick return mirror 251 that rotates by a predetermined angle between an observation position and an imaging position of a subject about a rotation axis 253, and a rotation of the quick return mirror 251 that is pivotally supported by the quick return mirror 251. It includes a sub mirror 252 that rotates according to the movement. In FIG. 14, the state in which the mirror system 250 is in the observation position of the subject is shown by a solid line, and the state in which the mirror system 250 is in the imaging position of the subject is shown by a two-dot chain line.

The mirror system 250 is inserted into the optical path of the optical axis L1 when it is in the observation position of the subject, and rotates so as to retract from the optical path of the optical axis L1 when it is in the imaging position of the subject.

The quick return mirror 251 is composed of a half mirror, and when the subject is in the observation position, the quick return mirror 251 reflects a part of the luminous flux (optical axis L2, L3) of the luminous flux (optical axis L1) from the subject. It is guided to the optical finder 235 and the photometric sensor 237, and a part of the luminous flux (optical axis L4) is transmitted and guided to the sub-mirror 252. On the other hand, the sub mirror 252 is composed of a total reflection mirror, and guides the luminous flux (optical axis L4) transmitted through the quick return mirror 251 to the focus detection module 261.

Therefore, when the mirror system 250 is in the observation position, the luminous flux (optical axis L1) from the subject is guided to the optical finder 235, the photometric sensor 237, and the focus detection module 261 to be observed by the photographer and exposed. The calculation and the detection of the focus adjustment state of the focus lens 32 by the focus detection module 261 are executed. Then, when the photographer fully presses the release button, the mirror system 250 rotates to the shooting position, all the luminous flux (optical axis L1) from the subject is guided to the image sensor 220, and the captured image data is stored in the camera memory 24. It is saved in.

The luminous flux (optical axis L2) from the subject reflected by the quick return mirror 251 is imaged on the focal plate 231 arranged on a surface optically equivalent to the image sensor 220, and the pentaprism 233 and the eyepiece 27 are formed. It is observable through. At this time, the transmissive liquid crystal display 232 superimposes the focus detection area mark and the like on the subject image on the focal plate 231 and displays the subject image and the shutter speed, the aperture value, the number of shots, and the like in the area outside the subject image. Display information. As a result, the photographer can observe the subject, its background, shooting-related information, and the like through the optical finder 235 in the shooting preparation state.

The photometric sensor 237 is composed of a two-dimensional color CCD image sensor or the like, and in order to calculate the exposure value at the time of shooting, the shooting screen is divided into a plurality of areas and a photometric signal corresponding to the brightness of each area is output. The signal detected by the photometric sensor 237 is output to the camera control unit 21 and used for automatic exposure control, recognition of a specific subject (for example, face recognition), and the like.

The focus detection module 261 is a dedicated focus detection element that executes automatic focusing control by a phase difference detection method, and is optically equivalent to the image pickup surface of the image pickup element 220 of the luminous flux (optical axis L4) reflected by the sub mirror 252. It is fixed in a proper position.

FIG. 15 is a diagram showing a configuration example of the focus detection module 261 shown in FIG. The focus detection module 261 of the present embodiment includes a condenser lens 261a, an aperture mask 261b having a pair of apertures formed, a pair of reimaging lenses 261c, and a pair of line sensors 261d. Further, although not shown, in the line sensor 261d of the present embodiment, a pixel having a microlens arranged near the planned focal plane of the imaging optical system and a photoelectric conversion unit arranged with respect to the microlens is provided. It has a plurality of arranged pixel sequences. A pair of image signals can be acquired by receiving a pair of light fluxes passing through a pair of regions having different exit pupils of the focus lens 32 by each pixel arranged on the pair of line sensors 261d. Then, the focus adjustment state can be detected by obtaining the phase shift of the pair of image signals acquired by the pair of line sensors 261d by a correlation calculation described later.

For example, as shown in FIG. 15, when the subject P is imaged on the equivalent surface (planned imaging surface) 261e of the image sensor 220, the focus lens 32 is in focus, but the focus lens 32 moves in the optical axis L1 direction. When the image pickup point shifts from the equivalent surface 261e to the subject side (called the front focus) or shifts to the camera body side (called the rear focus), the focus shift state occurs.

Subsequently, the image pickup device 220 according to the fourth embodiment will be described. FIG. 16 is a front view showing the image sensor 220 according to the fourth embodiment, and FIG. 17 is an enlarged front view showing one of the focus detection regions 224 shown in FIG. As shown in FIG. 16, the image sensor 220 according to the fourth embodiment has a position corresponding to the focus detection area AFP set on the shooting screen, that is, the center of the image pickup surface of the image sensor 220 and symmetrical from the center. Focus detection areas 224a to 224i for performing focus detection are set at a total of nine positions and their vertically symmetrical positions.

In the focus detection regions 224a to 224i, as shown in FIG. 17, a plurality of imaging pixels 221a are arranged two-dimensionally on the plane of the imaging surface. The imaging pixel 221a includes a green pixel G having a color filter that transmits a green wavelength region, a red pixel R that has a color filter that transmits a red wavelength region, and a blue that has a color filter that transmits a blue wavelength region. There is a pixel B, and each pixel is arranged by a Bayer arrangement.

Next, the configuration of the imaging pixel 221a will be described. FIG. 18A is an enlarged front view showing one of the imaging pixels 221a, and FIG. 18B is a cross-sectional view. As shown in FIG. 18A, the imaging pixel 221a is composed of a microlens 2211, a pair of photoelectric conversion units 2214 and 2215, and a color filter (not shown), and is as shown in the cross-sectional view of FIG. 18B. The photoelectric conversion units 2214 and 2215 are built on the surface of the semiconductor circuit board 2213 of the image pickup element 220, and the microlens 2211 is formed on the surface thereof. The pair of photoelectric conversion units 2214 and 2215 have the same size and are arranged symmetrically with respect to the optical axis of the microlens 2211. Further, the pair of photoelectric conversion units 2214 and 2215 are each shaped to receive an imaging light beam passing through the exit pupil (for example, F1.0) of the photographing optical system 31 by the microlens 2211. As shown in FIG. 18B, one photoelectric conversion unit 2215 of the image pickup pixel 221a receives the light flux AB1 of one, while the other photoelectric conversion unit 2214 of the image pickup pixel 221a is on the optical axis of the microlens 2211. On the other hand, the light flux AB2, which is symmetrical to the light flux AB1, is received.

Then, the photoelectric conversion units 2214 and 2215 of each imaging pixel 221a receive a pair of light fluxes AB1 and AB2, and output a pair of image signals corresponding to the intensities of the light fluxes AB1 and AB2 to be received. In other words, the photoelectric conversion units 2214 and 2215 output a pair of image signals according to the intensity of the image formed on the microlens 2211 by the luminous fluxes AB1 and AB2. Then, in the present embodiment, the pixel signal of the image pickup pixel 221a is generated by adding the pair of image signals output from the photoelectric conversion units 2214 and 2215 of the image pickup pixel 221a, and the pixel signal of the plurality of image pickup pixels 221a is used. Image data is generated.

Although the photoelectric conversion units 2214 and 2215 shown in FIG. 18A are rectangular, the shapes of the photoelectric conversion units 2214 and 2215 are not limited to this, and other shapes such as an elliptical shape and a semicircular shape are used. It can also be polygonal.

Next, a phase difference type focus detection (hereinafter, also referred to as image plane phase difference detection) using a pair of image signals output from the photoelectric conversion units 2214 and 2215 of the imaging pixel 221a will be described. In the following, as shown in FIG. 17, a plurality of imaging pixels 221a arranged in the horizontal direction (X direction) are designated as imaging pixel rows 225, and as will be described later, each imaging pixel constituting the imaging pixel row 225 By summarizing the outputs of the photoelectric conversion units 2214 and 2215 of 221a, a pair of image data is generated from one imaging pixel array 225, and the defocus amount is calculated based on the generated pair of image data.

FIG. 19 is a cross-sectional view taken along the line XIX-XIX of FIG. 17, in which the imaging pixel 221a-1 arranged on the photographing optical axis L and the imaging pixel 221a-2 adjacent thereto measure the exit pupil 340. It is shown that the light flux AB1-1, AB1-2, AB2-1, AB2-2 emitted from the distance pupils 341, 342 is received. However, although not shown, the pair of photoelectric conversion units also receive a pair of light fluxes emitted from the pair of ranging pupils 341 and 342 for other imaging pixels. In FIG. 19, the arrangement directions of the photoelectric conversion units 2214-1,225-1,214-2,2215-2 of the imaging pixel 221a coincide with the arrangement directions of the pair of ranging pupils 351 and 352.

The photoelectric conversion unit 2214-1 of the imaging pixel 221a-1 passes through one ranging pupil 341 and heads toward the microlens 2211-1, and the intensity of the image formed on the microlens 2211-1 by the other AB1-1. Outputs the signal corresponding to. On the other hand, the photoelectric conversion unit 2215-1 has the intensity of the image formed on the microlens 2211-1 by the other luminous flux AB2-1 passing through the other ranging pupil 342 and heading toward the microlens 2211-1. Outputs the signal corresponding to.

Similarly, the photoelectric conversion unit 2214-2 of the imaging pixel 221a-2 is formed on the microlens 2211-2 by the light flux AB1-2 of the one passing through the ranging pupil 341 and toward the microlens 2211-2. Outputs a signal corresponding to the intensity of the image. On the other hand, the photoelectric conversion unit 2215-2 has the intensity of the image formed on the microlens 2211-2 by the other luminous flux AB2-2 passing through the other ranging pupil 342 and heading toward the microlens 2211-2. Outputs the signal corresponding to.

Then, the outputs of the photoelectric conversion units 2214 and 2215 of each imaging pixel 221a constituting the imaging pixel train 225 are grouped into output groups corresponding to the ranging pupil 341 and the ranging pupil 342, thereby forming the ranging pupil 341. It is possible to obtain data on the intensity distribution of a pair of images formed on the imaging pixel array 225 by the luminous fluxes AB1 and AB2 passing through each of the distance measuring pupils 342, that is, a pair of image data. For example, in the example shown in FIG. 17, eight or more image pickup pixel rows 225 are set, and the camera control unit 21 can obtain a pair of image data from each image pickup pixel row 225.

Then, the camera control unit 21 performs pupil division phase difference detection by performing image shift detection calculation processing such as correlation calculation processing or phase difference detection processing on the pair of image data obtained from each imaging pixel row 225. The amount of image deviation by the method can be detected. Then, the camera control unit 21 can obtain the defocus amount by performing a conversion operation on the obtained image deviation amount according to the distance between the centers of gravity of the pair of ranging pupils.

In this way, the camera control unit 21 can calculate the defocus amount for each image pickup pixel row 225 based on the pair of image data obtained from each image pickup pixel row 225. However, in the fourth embodiment, the camera control unit 21 identifies the image pickup pixel sequence 225 used for focus detection and identifies the image pickup pixel sequence in order to shorten the time required for focus detection and perform focus detection at an appropriate timing. The defocus amount is calculated based only on the output of 225.

Specifically, the camera control unit 21 first extracts a frequency component corresponding to the subject from the output of each image pickup pixel row 225, and detects information on the extracted frequency component as contrast information. For example, as in the third embodiment, the camera control unit 21 filters the output of each image pickup pixel sequence 225 by using a predetermined bandpass filter, so that the output is included in the output of the image pickup pixel sequence 225. The low frequency component caused by the background and the high frequency component corresponding to noise are removed from the frequency components, and the frequency component corresponding to the subject is extracted. Then, the camera control unit 21 can detect, for example, the data obtained by filtering the output of the image pickup pixel array 225 as the contrast information of the frequency component included in the output of the image pickup pixel array 225.

Further, the camera control unit 21 calculates a contrast amount representing the amount and intensity of the frequency component based on the contrast information of the extracted frequency component. Here, FIG. 20 is an enlarged front view showing one of the focus detection regions 224a to 224i shown in FIG. 16, similarly to FIG. 17, and FIG. 21 is an image of the first group LA shown in FIG. 20. It is a figure which shows the pixel 221a schematically. In addition, in FIG. 20 and FIG. 21, the image pickup pixel sequence 225 is represented as the image pickup pixel sequence A1 to A5, B1 to B5, C1 to C5, D1 to D5, and E1 to E5, respectively. Further, in the examples shown in FIGS. 21 (A) and 21 (B), it is assumed that each imaging pixel sequence has 12 imaging pixels 221a.

First, the camera control unit 21 groups a plurality of image pickup pixel rows 225 set in the focus detection region 224 into a predetermined number of image pickup pixel rows 225 (for example, five image pickup pixel rows 225). For example, in the example shown in FIG. 20, the camera control unit 21 has a first group LA composed of imaging pixel rows A1 to A5 and an imaging pixel row B1 for each of five imaging pixel rows 225 that are continuous in the vertical direction (Y direction). Like the second group LB consisting of ~ B5, the third group LC consisting of imaging pixel sequences C1 to C5, the fourth group LD consisting of imaging pixel sequences D1 to D5, and the fifth group LE consisting of imaging pixel sequences E1 to E5. , Each imaging pixel row 225 is grouped. The number of image pickup pixel rows 225 to be grouped is not limited to five, and can be set as appropriate.

Then, the camera control unit 21 calculates the output value of the frequency component in each group by adding the output value of each frequency component included in the output of the imaging pixel sequence 225 belonging to the same group for each group, and each of them. It is detected as the contrast information of the frequency component in the group. For example, in the example shown in FIG. 21A, the camera control unit 21 adds the output values of the frequency components corresponding to the outputs of the first imaging pixels 221a in the imaging pixel sequences A1 to A5 to obtain the output values. Calculate a1. Similarly, the camera control unit 21 calculates the output value a2 by adding the output values of the frequency components corresponding to the outputs of the second image pickup pixels 221a in the image pickup pixel rows A1 to A5, respectively. Similarly, the camera control unit 21 also has a frequency component corresponding to the output of the image pickup pixels 221a arranged at the same position in the lateral direction (X direction) for the third and subsequent image pickup pixels 221a in the image pickup pixel rows A1 to A5, respectively. By adding the output values of, the output values a3, a4, ..., A12 are calculated. As a result, the camera control unit 21 can detect the output value including a1, a2, a3, ..., A12 as the contrast information of the frequency component in the first group LA.

Further, the camera control unit 21 also detects the contrast information of the frequency components in the second group LB, the third group LC, the fourth group LD, ..., Similar to the first group LA. Then, the camera control unit 21 calculates the contrast amount of the frequency component in each group based on the contrast information of the frequency component of each group. For example, in the example shown in FIG. 21 (A), the camera control unit 21 sets the output values a1, a2, a3, ..., A12 of the frequency components in the first group LA as shown in the above equation (3). The amount of contrast of the frequency component in the first group LA can be calculated by obtaining the sum of the difference between a1 and a2, the difference between a2 and a3, ..., The difference between a11 and a12. ..

In the above example, the output value of the frequency component in each group is calculated by adding the output values of the frequency components corresponding to the outputs of the imaging pixels 221a arranged at the same position in the horizontal direction (X direction). Although the configuration is illustrated, the configuration is not limited to this configuration, and for example, by averaging the output values of the frequency components corresponding to the outputs of the imaging pixels 221a arranged at the same position in the lateral direction (X direction), each group The output value of the frequency component in the above may be calculated. For example, when the brightness or contrast of the subject is relatively low, the output value of the frequency component corresponding to the output of the imaging pixel 221a is added to calculate the output value of the frequency component in each group, and the brightness or contrast of the subject is calculated. When is relatively high, the output values of the frequency components corresponding to the outputs of the imaging pixels 221a can be averaged to calculate the output values of the frequency components in each group.

Further, as shown in FIG. 21 (B), the output values of the frequency components corresponding to the outputs of the photoelectric conversion units 2214 and 2215 arranged at the same position in the horizontal direction (X direction) are added or averaged. Therefore, the output value of the frequency component in each group may be calculated. That is, as shown in FIG. 21B, the camera control unit 21 sets the output value of the frequency component corresponding to the output of the photoelectric conversion unit 2214 of the first imaging pixel 221a in each imaging pixel sequence A1 to A5. The output value b1 is calculated by adding or averaging. Similarly, the camera control unit 21 adds or averages the output values of the frequency components corresponding to the outputs of the photoelectric conversion unit 2215 of the first imaging pixel 221a in each of the pixel rows A1 to A5, thereby adding or averaging the output values. Calculate c1. Similarly, the camera control unit 21 is also arranged at the same position in the lateral direction (X direction) in each of the pixel rows A1 to A5 with respect to the photoelectric conversion unit 2214 and the photoelectric conversion unit 2215 included in the second and subsequent imaging pixels 221a. The output values b2, c2, b3, c3, ..., B12, c12 are calculated by adding or averaging the output values of the frequency components corresponding to the outputs of the photoelectric conversion units 2214 and 2215. As a result, the camera control unit 21 can acquire an output value including b1, c1, b2, c2, b3, c3, ..., B12, c12 as the contrast information of the frequency component in the first group LA. .. Similarly, as shown in FIG. 22, the camera control unit 21 acquires the contrast information of the frequency components in the groups LB, LC, LD, LE, .... Note that FIG. 22 is a diagram showing an example of frequency components in each group LA, LB, ... LE shown in FIG. 20.

Then, the camera control unit 21 calculates the contrast amount of the frequency component in each group based on the contrast information of the frequency component in each group. For example, in the example shown in FIG. 21 (B), the camera control unit 21 has the output values b1, c1, b2, c2, b3, c3 of the frequency components in the first group LA as shown in the above equation (3). The sum of the differences between consecutive output values among b12 and c12 can be calculated as the contrast amount of the frequency component. Further, the camera control unit 21 calculates column data obtained by adding the output values b1, c1, b2, c2, b3, c3, ..., B12 and c12, respectively, and the difference between the calculated column data is a continuous value. May be configured to calculate the sum of the above as the amount of contrast of the frequency component. Alternatively, the camera control unit 21 sets the output values b1, c1, b2, c2, b3, c3, ..., B12, c12 as column data consisting of the output values b1, b2, b3, ..., B12. The contrast amount of the frequency component in each column data is calculated separately from the column data consisting of the output values c1, c2, c3, ..., C12, and the contrast amount of the larger value or the contrast of the smaller value is calculated. The amount may be calculated as the contrast amount of the frequency component in each group.

Further, in the above-described example, a configuration is exemplified in which the contrast information of the frequency components in each group is detected by adding or averaging all the frequency components included in the outputs of all the imaging pixel strings 225 belonging to the same group. However, the configuration is not limited to this, and the number of frequency components to be added or averaged may be changed based on, for example, the brightness of the field of view, the brightness of the image, or the contrast of the image. For example, the higher the brightness of the field, the brightness of the image, or the contrast of the image, the smaller the number of frequency components to be added, and the lower the brightness of the field, the brightness of the image, or the contrast of the image, the lower the number of frequency components to be added. The number of frequency components to be added can be increased.

Then, the camera control unit 21 determines the group having the largest contrast amount among the contrast amounts of the frequency components calculated for each group as a specific group, and defocuses based on the output of the imaging pixel 221a included in the specific group. Calculate the amount. For example, in the example shown in FIG. 22, since the amount and intensity of the frequency component in the third group LC are large, the contrast amount of the frequency component in the third group LC is the largest among the groups LA to LE. In this case, the camera control unit 21 specifies the third group LC as a specific group, and calculates the defocus amount based on the output of the imaging pixels 221a included in the third group.

For example, as shown in FIG. 21B, the camera control unit 21 is a photoelectric conversion unit arranged at the same position in the lateral direction (X direction) among the outputs of the photoelectric conversion units 2214 and 2215 included in the specific group. By adding or averaging the outputs of 2214 and 2215, an image data consisting of a pair of image data (output values b1, b2, b3, ...) And an image consisting of output values c1, c2, c3, ... Data and) are calculated. Then, as shown in the above equation (1), the camera control unit 21 performs the correlation calculation while relatively shifting the calculated pair of image data to obtain the correlation amount C (k) of the pair of image data. Based on the calculated correlation amount C (k), the defocus amount can be calculated as shown in the above equation (2). Then, the camera control unit 21 can adjust the focus of the optical system by driving the focus lens 32 based on the calculated defocus amount.

In the fourth embodiment, the camera control unit 21 can also control the drive of the focus lens 32 based on the defocus amount calculated by the focus detection module 261 and also based on the output of the image sensor 220. It is also possible to control the drive of the focus lens 32 based on the defocus amount calculated in the above. For example, when the brightness of the light received by the image sensor 220 is low, the camera control unit 21 can control the drive of the focus lens 32 based on the defocus amount calculated by the focus detection module 261. .. Since the size of each pixel constituting the line sensor 261d of the focus detection module 261 is designed to be larger than that of the image pickup pixel 221a, focus detection is performed with relatively high accuracy even when the light intensity of the luminous flux is relatively weak. Because it is possible to do. On the other hand, for example, when shooting a moving image, the drive of the focus lens 32 can be controlled based on the defocus amount calculated based on the output of the image sensor 220. This is because in the image plane phase difference detection based on the output of the image sensor 220, the focus of the optical system can be detected while the image sensor 220 captures an image even during moving image shooting.

Next, the operation of the camera 1a according to the fourth embodiment will be described. FIG. 23 is a flowchart showing an operation example of the camera 1a according to the fourth embodiment. In the operation example of the camera 1a shown in FIG. 23, a scene in which the camera control unit 21 performs focus detection based on the output of the image sensor 220 will be described as an example.

First, in step S401, the image sensor 220 acquires the output data of the image pickup pixels 221a (photoelectric conversion units 2214 and 2215 of the image pickup pixels 221a). Further, in step S402, the camera control unit 21 selects the focus detection area AFP for use in focus adjustment. For example, the photographer can select the focus detection area AFP for adjusting the focus by manually operating the operation unit 28. As a result, the camera control unit 21 determines the focus detection area 224 corresponding to the selected focus detection area AFP as the focus detection area 224 for performing focus detection.

Then, in step S403, the camera control unit 21 sets a plurality of imaging pixels 221a arranged one-dimensionally in the lateral direction (X direction) as the imaging pixel row 225 in the focus detection region 224 determined in step S402. , The contrast information of the frequency component included in the output of each image pickup pixel sequence 225 is detected.

Then, in step S404, the camera control unit 21 groups a plurality of image pickup pixel rows 225 in the focus detection region 224 into a predetermined number of image pickup pixel rows 225. For example, as shown in FIG. 20, the camera control unit 21 groups a plurality of image pickup pixel sequences 225 into groups LA, LB, LC, LD, LE, ... For each of the five image pickup pixel sequences. Can be done.

In step S405, the camera control unit 21 adds the output values of the frequency components included in the output of the imaging pixel sequence 225 belonging to the same group, whereby the contrast information of the frequency components in each group is detected. Specifically, as shown in FIG. 21A, the camera control unit 21 has image pickup pixels 221a arranged at the same positions in the lateral direction (X direction) in a plurality of imaging pixel rows 225 belonging to the same group. By adding the output values of the frequency components corresponding to the outputs, the contrast information of the frequency components in each group is detected.

Then, in step S406, the camera control unit 21 calculates the contrast amount of the frequency component in each group based on the contrast information of the frequency component in each group detected in step S405. For example, the camera control unit 21 can calculate the contrast amount of the frequency component in each group from the output value of the frequency component in each group based on the above equation (3).

In step S407, the camera control unit 21 compares the contrast amounts of the frequency components calculated for each group in step S406, and the group having the highest contrast amount is determined as a specific group for performing focus detection. Then, in step S408, the camera control unit 21 calculates the defocus amount based on the output of the imaging pixels 221a included in the specific group determined in step S407. For example, as shown in FIG. 21 (B), the camera control unit 21 is a photoelectric conversion unit 2214, 2215 arranged at the same position in the lateral direction (X direction) in each imaging pixel row 225 in the specific group. A pair of image data is calculated by adding the outputs. Then, the camera control unit 21 performs a correlation calculation of the calculated pair of image data, and calculates the defocus amount based on the calculation result. Then, in step S409, the camera control unit 21 drives the focus lens 32 based on the defocus amount calculated in step S408.

As described above, the focus detection of the optical system according to the fourth embodiment is performed.

As described above, in the fourth embodiment, as shown in FIG. 17, a plurality of imaging pixels 221a having a pair of photoelectric conversion units 2214 and 2215 are arranged in a two-dimensional manner on the image sensor 220. Then, among the plurality of imaging pixels 221a, a plurality of imaging pixels 221a arranged in the horizontal direction (X direction) are set as the imaging pixel rows 225, and the photoelectric conversion unit 2214 of the imaging pixels 221a constituting each imaging pixel row 225 is set. , 2215 are grouped into output groups corresponding to the distance measuring pupil 351 and the distance measuring pupil 352 to acquire a pair of image data, and the defocus amount is calculated based on the acquired pair of image data. Performs phase difference detection. Thereby, in the fourth embodiment, the focal state of the optical system can be appropriately detected even during, for example, moving image shooting.

Further, in the fourth embodiment, each imaging pixel row 225 is grouped by a predetermined number of imaging pixel rows 225, and the output value of each frequency component included in the output of the imaging pixel row 225 belonging to the same group is set for each group. By adding to, the contrast information of the frequency components in each group is detected. Then, the contrast amount of the frequency component in each group is calculated based on the contrast information of the frequency component in each group, the group having the highest contrast amount is determined as a specific group, and based on the output of the imaging pixel 221a in the specific group. , Performs focus detection. As a result, in the fourth embodiment, the focus can be detected in a group containing a large amount of high-frequency components and in which the subject is likely to exist, so that the focal state of the optical system with respect to the subject can be detected more appropriately. .. Further, in the fourth embodiment, the group having the highest contrast amount is determined as a specific group, and the image plane phase difference is detected based on the output of the imaging pixels 221a in the specific group, so that the output of all the imaging pixels 221a is obtained. Compared with the case where the defocus amount is calculated based on the defocus amount, the time required for calculating the defocus amount can be shortened, whereby the focus can be detected at an appropriate timing.

<< Fifth Embodiment >>
Next, the fifth embodiment will be described. The fifth embodiment has the same configuration as the fourth embodiment described above, except that the camera 1a shown in FIG. 14 operates as described below.

In the image pickup device 220 according to the fifth embodiment, as in the fourth embodiment, the image pickup element 220 has two-dimensionally arranged image pickup pixels 221a having a pair of photoelectric conversion units 2214 and 2215. Then, in the fifth embodiment, the camera control unit 21 detects a specific subject such as a person's face and extracts the output of the imaging pixel 221a corresponding to the specific subject at a ratio corresponding to the color indicating the specific subject. Then, the frequency component corresponding to the specific subject is extracted.

Specifically, the camera control unit 21 first detects a specific subject such as a person's face by performing template matching using a template image such as a person's face. Then, the camera control unit 21 specifies the region of the image sensor 220 corresponding to the specific subject as the target region. The camera control unit 21 may be configured to specify the target region within the focus detection regions 224a to 224i, or may be configured to specify the target region in the entire image sensor 220.

Then, the camera control unit 21 detects whether or not the target area exists in the focus detection area 224 selected by the user or the camera control unit 21. That is, when the focus detection area AFP for performing focus adjustment is selected by the user or the camera control unit 21, the camera control unit 21 determines the focus detection area 224 corresponding to the focus detection area, and determines the focus detection area 224. It is determined whether or not the target area exists in the area 224. Then, when the target area exists in the focus detection area 224, the camera control unit 21 identifies the pixel group 223 corresponding to the target area in the focus detection area 224. Further, the camera control unit 21 sets a pixel group sequence 226 including a pixel group 223 corresponding to the target region. For example, as shown in FIG. 24, the camera control unit 21 arranges a plurality of pixel groups 223 including the pixel group 223 corresponding to the target region in a horizontal direction (X direction) in a one-dimensional manner. It can be set as 226. Note that FIG. 24 is a diagram schematically showing the imaging pixels 221a of the first group LA shown in FIG. 20. Further, in the example shown in FIG. 24, the pixel string 226 will be described as having six pixel groups 223.

Then, the camera control unit 21 extracts the frequency component corresponding to the pixel group sequence 226 from the output of the pixel group sequence 226, and detects the contrast information regarding the extracted frequency component. Specifically, the camera control unit 21 first indicates the output values of the four imaging pixels 221a (including the R pixel, G pixel, and B pixel) constituting the pixel group 223 to indicate a specific subject such as a person's face. Extract at a ratio according to the color (for example, the skin color of a specific subject). For example, the camera control unit 21 can extract the output values of the R pixel and the G pixel higher than the output of the B pixel so that the ratio corresponds to the skin color of the specific subject. Then, the camera control unit 21 adds or averages the output values extracted from the four imaging pixels 221a (R pixel, G pixel, B pixel) constituting the pixel group 223 to obtain the output value of the pixel group 223. To detect. Further, the camera control unit 21 detects the output value of the pixel group 223 constituting each pixel group 226 along the arrangement direction of the pixel group 223, so that the pixel group 226 composed of a plurality of pixel groups 223 Detect the output. Then, the camera control unit 21 extracts the frequency component corresponding to the subject from the output of the pixel group 226 by performing a filter process using a predetermined bandpass filter on the output of the pixel group 226. The contrast information of the extracted frequency component is detected.

Further, the camera control unit 21 groups a plurality of pixel group rows 226 corresponding to the target area into a predetermined number of pixel group rows 226, and adds a frequency component corresponding to the output of the pixel group rows 226 belonging to the same group. By doing so, the contrast information of the frequency component in each group is detected. For example, in the example shown in FIG. 24, the pixel group rows 226 belonging to the same group are represented by A1'to A3'. In this case, the camera control unit 21 acquires the output value d1 by adding the output values of the frequency components corresponding to the outputs of the first pixel group 223 in each pixel group sequence A1'to A3'. Similarly, the camera control unit 21 acquires the output value d2 by adding the output values of the frequency components corresponding to the outputs of the second pixel group 223 in each pixel group sequence A1'to A3'. Similarly, the camera control unit 21 also adds the output values of the frequency components corresponding to the outputs of the respective pixel groups 223 for the third and subsequent pixel groups 223 from the left, so that the output values d3, d4, d5, and so on are added. d6 can be acquired, and the acquired output values d1, d2, d3, d4, d5, d6 can be detected as contrast information of frequency components in the group. The camera control unit 21 averages the output values of the frequency components corresponding to the outputs of the pixel groups 223 arranged at the same positions in the horizontal direction (X direction) to obtain the contrast information of the frequency components in each group. It may be configured to detect.

Then, the camera control unit 21 calculates the contrast amount of the frequency component in each group based on the contrast information of the frequency component in each group. Further, when a plurality of groups corresponding to the target area exist in the focus detection area 224, the camera control unit 21 similarly calculates the contrast amount of the frequency component in the other groups. Then, the camera control unit 21 determines the group having the highest contrast amount among the groups for which the contrast amount has been calculated as a specific group, and calculates the defocus amount based on the output of the imaging pixel 221a in the specific group. The method of calculating the defocus amount in the specific group can be performed in the same manner as in the fourth embodiment.

Next, the operation of the camera 1 according to the fifth embodiment will be described with reference to FIG. 25. Note that FIG. 25 is a flowchart showing an operation example of the camera 1 according to the fifth embodiment.

First, in step S501, the camera control unit 21 detects the target area corresponding to the specific subject. For example, the camera control unit 21 detects a specific subject by performing template matching using a template image of a specific subject such as a person's face, and sets the region of the image sensor 220 corresponding to the detected specific subject as a target region. Can be detected as.

Then, in step S502, similarly to step S402 of the fourth embodiment, the focus detection area AFP to be used for focus adjustment is selected, whereby the focus detection area 224 corresponding to the selected focus detection area AFP is selected. Is determined as the focus detection area 224 for performing focus detection.

In step S503, the camera control unit 21 determines whether or not the target area detected in step S501 exists in the focus detection area 224 selected in step S502. If the target area exists in the focus detection area 224, the process proceeds to step S504, while if the target area does not exist in the focus detection area 224, the process proceeds to step S513. In steps S513 to S515, the contrast information of the imaging pixel row 225 set in the focus detection region 224 is detected (step S513), and each imaging pixel row 225 is detected, as in steps S403 to S405 of the fourth embodiment. The frequency components in each group are grouped by a predetermined number of imaging pixel rows (step S514), and the output values of the frequency components included in the output of the imaging pixel row 225 belonging to the same group are added to each group. Contrast information is detected. (Step S515).

On the other hand, if the target area is detected in the focus detection area 224 in step S503 (step S503 = Yes), the process proceeds to step S504. In step S504, the camera control unit 21 extracts the output values of the four imaging pixels 221a constituting each pixel group 223 in the target area at a ratio corresponding to the color indicating the specific subject (for example, the skin color of the specific subject). .. Then, in step S505, the camera control unit 21 detects the output of each pixel group 223 included in the target area based on the output of the image pickup pixel 221a extracted in step S504, and each of the plurality of pixel groups 223 is composed of the plurality of pixel groups 223. The output of the pixel group 226 is detected. That is, the camera control unit 21 adds or averages the output values of the imaging pixels 221a extracted at a ratio corresponding to the color indicating the specific subject in units of 223 pixel groups, so that the pixel group corresponding to the skin color of the specific subject is obtained. The output value of 223 is detected. Then, the camera control unit 21 detects the output values of the plurality of pixel groups 223 constituting the pixel group row 226 along the arrangement direction of the pixel group 223 in the pixel group row 226, thereby outputting the pixel group row 226. Is detected.

Further, in step S506, the camera control unit 21 detects the contrast information of the frequency component included in the output of the pixel group 226 based on the output of the pixel group 226 detected in step S505. For example, the camera control unit 21 extracts a frequency component corresponding to the subject from the output of the pixel group 226 by performing a predetermined filter process on the output of the pixel group 226, and contrast information of the extracted frequency component. Is detected.

In step S507, the camera control unit 21 groups the pixel group rows 226 corresponding to the target area into a predetermined number of pixel group rows 226. Then, in step S508, the camera control unit 21 adds the output values of the frequency components included in the output of the pixel group sequence 226 belonging to the same group to detect the contrast information of the frequency components in each group.

In step S509, based on the contrast information of the frequency components in each group detected by the camera control unit 21 in step S509 or step S515, for example, as shown in the above equation (3), the contrast amount of the frequency components in each group. Is calculated.

Then, in steps S510 to S512, the group having the highest contrast amount is determined as the specific group as in S407 to S409 of the fourth embodiment (step S510), and based on the output of the imaging pixels 221a included in the specific group, the group is determined. The defocus amount is calculated (step S511). Then, the focus lens 32 is driven based on the calculated defocus amount (step S512).

As described above, in the fifth embodiment, by extracting the output of each imaging pixel 221a at a ratio corresponding to the color indicating the specific subject, the frequency component caused by the specific subject such as the face of a person is extracted with higher accuracy. can do. Then, a group to perform focus detection is determined based on the frequency component extracted in this way, and focus detection is performed based on the output of the imaging pixel 221a in the group to further obtain the focal state of the optical system for a specific subject. It becomes possible to detect appropriately.

Although the embodiments have been described above, the above-described embodiments are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-described embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, in the first to third embodiments described above, a configuration in which four focus detection pixel sequences L1 to L4 are provided for one focus detection area AFP has been illustrated, but the number of focus detection pixel sequences is the same. The number of focus detection pixel rows in one focus detection area is not limited, and may be 2 or 3, or may be 5 or more. Further, in the fourth embodiment and the fifth embodiment described above, the configuration in which the image pickup pixels 221 having the pair of photoelectric conversion units 2214 and 2215 are arranged in the focus detection regions 224a to 224i has been illustrated. The image pickup pixels 221 may be arranged on the entire 220.

Further, in the first to third embodiments described above, the image sensor 22 is provided with the focus detection pixel strings L1 to L4, and the defocus amount is calculated based on the output of the focus detection pixel strings L1 to L4. Although illustrated, the configuration is not limited to this. For example, a phase difference AF detection module is provided separately from the image sensor 22, and the defocus amount is calculated based on the light receiving signal received by the phase difference AF detection module. It may be configured to be used. Specifically, the phase difference AF detection module has a plurality of pairs of line sensors that receive light flux passing through the optical system, detects contrast information for each line sensor, and is based on the detected contrast information. , A pair of line sensors used for focus detection may be determined from a plurality of line sensors. When determining the pair of line sensors used for focus detection, the arithmetic unit included in the phase difference detection module may be configured to determine the pair of line sensors used for focus detection, or the camera control unit 21. However, the pair of line sensors used for focus detection may be determined by acquiring the outputs of each pair of line sensors.

As described above, the "light receiving element group" may be, for example, the focus detection pixel trains L1 to L4, or the pair of line sensors described above. Further, the "focus detection device" may be, for example, an image sensor 22, 220 or a camera 1 including the image sensor 22, or a phase difference AF detection module or a camera 1 including the same.

Further, in the first to third embodiments described above, in the focus detection pixel sequences L1 and L3 and the focus detection pixel sequences L2 and L4, the first focus detection pixel 222a and the second focus detection pixel 222b are in the X-axis direction. However, the configuration is not limited to this, and for example, as shown in FIG. 26, the focus detection pixels 222a and 222b constituting the focus detection pixel rows L1a to L4a are the same in the X-axis direction. It may be configured to be arranged so as to be in a position.

Further, as shown in the focus detection pixel rows L1b and L2b of FIG. 27, the focus detection pixels 222a and 222b may be configured to include a pair of photoelectric conversion units 2222a and 2222b. Specifically, as shown in FIG. 27, in each focus detection pixel 222a, 222b, a pair of photoelectric conversion units 2222a, 2222b are arranged in the X-axis direction, and a pair of luminous fluxes emitted from the distance measuring pupil 351 are paired. The light flux received by one of the photoelectric conversion units 2222a and 2222b and emitted from the distance measuring pupil 352 is received by the other photoelectric conversion unit. Thereby, a pair of image data strings can be output in each focus detection pixel sequence L1b and L2b, respectively. In FIG. 27, the photoelectric conversion unit that receives the light flux emitted from the distance measuring pupil 351 is shown in gray, and the photoelectric conversion unit that receives the light flux emitted from the distance measuring pupil 352 is shown in white. Further, in the example shown in FIG. 27, a configuration having two focus detection pixel rows L1b and two L2b is illustrated, but the configuration is not limited to this configuration, and for example, a configuration having only one focus detection pixel row L1b and L2b. Or it may be configured to have three or more rows.

Further, the arrangement of the first focus detection pixel 222a and the second focus detection pixel 222b constituting each focus detection pixel row may be at least alternately arranged on the same row, for example, FIG. 28. The focus detection pixel array L1c to L4c shown in the above may be configured so that the normal image pickup pixel 221 is included in the focus detection pixel array.

Further, in addition to the above-described embodiment, when the contrast of the subject (or the brightness of the subject) is equal to or higher than a predetermined value, the contrast among the focus detection pixel sequences L1 to L4 is as shown in the first embodiment. The focus detection pixel string corresponding to the largest subject or the focus detection pixel string containing the largest amount of high-frequency components in the output is determined as the specific focus detection pixel string, while the contrast of the subject (or the brightness of the subject) is predetermined. If it is less than the value, as shown in the second embodiment, one or a plurality of focus detection pixel strings L1 to L4 in which the contrast of the corresponding subject is equal to or higher than a predetermined value, or One or a plurality of focus detection pixel strings in which the amount of the high frequency component contained in the output is equal to or greater than a predetermined value may be determined as the specific focus detection pixel string.

Further, in the fourth embodiment described above, the frequency component corresponding to the output of each image pickup pixel row 225 is added for each group to calculate the contrast amount of the frequency component for each group, and the group has the highest contrast amount. Although a configuration for calculating the defocus amount based on the output of the included imaging pixel 221a has been illustrated, the configuration is not limited to this configuration and can be configured as follows. That is, the contrast amount of the frequency component is calculated for each image pickup pixel row 225 from the frequency component corresponding to the image pickup pixel row 225, and the image pickup pixel having the highest contrast amount among the plurality of image pickup pixel rows 225 included in the same group. Column 225 is specified for each group. Then, the defocus amount is calculated for each group based on the output of the image pickup pixel 221a included in the image pickup pixel row 225 having the highest contrast amount, and the focus of the optical system is adjusted based on these defocus amounts. You can also do it. Further, the contrast amount of the frequency component is calculated for each image pickup pixel row 225, the defocus amount is calculated for each image pickup pixel row 225, and the optical system is based on the defocus amount of the image pickup pixel row 225 having the highest contrast amount. It may be configured to adjust the focus of.

Further, in the fourth embodiment and the fifth embodiment described above, a configuration in which the defocus amount is calculated based on the output of the imaging pixel 221a included in the group having the highest contrast amount of the frequency component has been exemplified. For example, the output of the imaging pixel 221a in each group is weighted based on the magnitude of the contrast amount of the frequency component in each group, and the defocus amount is determined based on the output of the weighted imaging pixel 221a. It can be configured to be calculated. In this case, the camera control unit 21 can increase the weight of the output of the imaging pixel 221a in the group as the contrast amount of the frequency component in the group increases. Further, the camera control unit 21 calculates the defocus amount for each group, weights the calculated defocus amount according to the contrast amount of the frequency component in each group, and calculates the defocus amount used for the focus adjustment. It can also be configured.

Further, in the fourth embodiment and the fifth embodiment described above, a configuration in which a plurality of imaging pixels 221a are arranged in a two-dimensional manner in each focus detection region 224a to 224i has been illustrated, but the configuration is not limited to this configuration, and for example. The focus detection regions 224a to 224i may have only a single imaging pixel array 225, or may have two or more discrete or continuous imaging pixel sequences 225. Further, in the first to third embodiments described above, the configuration in which the focus detection pixels 222a and 222b are arranged in the lateral direction (X direction) in the focus detection pixel rows L1 to L4 has been illustrated, but the configuration is limited to this configuration. However, for example, the focus detection pixels 222a and 222b can be arranged in the vertical direction (Y direction). Further, also in the fourth embodiment and the fifth embodiment described above, a plurality of imaging pixels 221a arranged in the vertical direction (Y direction) may be configured as an imaging pixel row 225. In this case, in each imaging pixel row 225 belonging to the same group, the output values of the frequency components corresponding to the outputs of the imaging pixels 221a arranged at the same position in the vertical direction (Y direction) are added to each group. The output value of the frequency component can be calculated.

In addition, in the fourth and fifth embodiments described above, the single-lens reflex digital camera 1a provided with the image sensor 220 has been described as an example, but the present invention is not limited to this configuration, and for example, the digital camera 1 shown in FIG. In the configuration, the image sensor 220 may be provided. In this case as well, focus detection can be performed in the same manner as in the fourth and fifth embodiments.

1,1a ... Digital camera 2,2a ... Camera body 21,220 ... Camera control unit 22 ... Imaging element 221,221a ... Imaging pixels L1 to L4 ... Focus detection pixel sequence 225 ... Imaging pixel sequence 226 ... Pixel group sequence 222a, 222b ... Focus detection pixel 3 ... Lens lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control unit

Claims (1)

The imaging surface for imaging the image formed by the optical system has a plurality of regions for detecting the in-focus state between the image and the imaging surface, and each of the regions has a first region of the optical system. An image sensor in which a plurality of pixel rows having a first pixel that receives light passing through and outputs a signal and a second pixel that receives light passing through a second region of the optical system and outputs a signal are arranged.
The in-focus state based on the signal output from the pixel array in a number smaller than the number of the pixel array arranged in the pixel array arranged in one of the plurality of areas. With a detector that detects
A focusing state detector equipped with.

Images