JP2022121474A - Focus detector, camera, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detector capable of repeating detection of the focus state of an optical system at appropriate timing.

SOLUTION: A focus detector includes: an imaging element including a plurality of areas where a plurality of pixel groups are disposed, each pixel group made up of a plurality of pixels that receive light of a subject passing through an optical system and output a signal based on the received light; and a detection unit that detects the focus state of an image of the subject formed by the optical system on the basis of the signal output from pixel groups the number of which is fewer than the pixel groups disposed in one of the areas selected on the basis of contrast of the signal output from the pixel groups.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to focus detection devices, cameras, and electronic devices.

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

Japanese Patent Application Laid-Open No. 2003-215437

However, in the prior art, since the defocus amount is calculated for all of the plurality of light receiving sensors, it takes time to calculate the defocus amount. Sometimes I couldn't.

A problem to be solved by the present invention is to provide a focus detection device, a camera, and an electronic device that can repeatedly detect the focus state of an optical system at appropriate timing.

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

[1] A focus detection device according to the present invention has a plurality of regions in which a plurality of pixel groups are arranged to receive light from a subject that has passed through an optical system and output a signal based on the received light. Based on the signals output from the image sensor and the pixel groups less than the number of the pixel groups arranged in one region, selected based on the contrast of the signals output from the pixel groups and a detection unit that detects a focused state of the image of the subject formed by the optical system.
[2] In the invention related to the focus detection device, the in-focus state of the image of the subject detected by the detection unit is a defocus amount that is a shift between the position of the image of the subject and the imaging surface of the imaging device. good too.
[3] In the focus detection device, the detection unit may select one pixel group and calculate the defocus amount based only on signals output from the selected pixel group. .
[4] In the invention related to the focus detection device, the detection unit selects a plurality of the pixel groups, the number of which is smaller than the number of the pixel groups arranged in one focus detection area, and the selected pixel groups. The defocus amount may be calculated based on either an added value or an average value of the output signals of .
[5] In the invention related to the focus detection device, the detection unit selects the pixel group for calculating the defocus amount based on contrast information of a plurality of different frequency components of signals output from the pixel group. may
[6] In the invention related to the focus detection device, the pixel group includes a plurality of pixels that receive light that has passed through a first pupil of the optical system, and a plurality of pixels that receive light that has passed through a second pupil of the optical system. It may have a plurality of pixels that receive light.
[7] In the focus detection device described above, the detection unit selects the pixel group for calculating the defocus amount from among the plurality of parallel pixel groups arranged in one region. good too.
[8] A camera according to the present invention includes the above focus detection device.
[9] An electronic device according to the present invention includes the focus detection device described above.

According to the present invention, detection of the focus state of the optical system can be repeatedly performed at appropriate timing.

FIG. 1 is a block diagram showing a camera according to this embodiment. 2 is a front view showing an imaging surface of the imaging device shown in FIG. 1. FIG. FIG. 3 is a front view schematically showing the arrangement of the imaging pixels 221 and the focus detection pixels 222a and 222b by enlarging the III section of FIG. 4A is an enlarged front view showing one of the imaging pixels 221, FIG. 4B is an enlarged front view showing one of the first focus detection pixels 222a, and FIG. is a front view showing an enlarged one of the second focus detection pixels 222b, FIG. 4D is a cross-sectional view showing an enlarged one of the imaging pixels 221, and FIG. FIG. 4F is a cross-sectional view showing an enlarged view of one of the detection pixels 222a, and FIG. 4F is a cross-sectional view showing an enlarged view of one of the second focus detection pixels 222b. 5 is a cross-sectional view taken along line V-V of FIG. 3. FIG. FIG. 6 is a flow chart 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 this 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 pixels 222a and the second focus detection pixels 222b according to this embodiment. FIG. 10A is a graph showing the relationship between the correlation amount and the shift amount in this 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 flow chart showing the operation of the camera according to the second embodiment. FIG. 12 is a front view schematically showing the arrangement of focus detection pixels 222a and 222b according to another embodiment. FIG. 13 is a front view schematically showing the arrangement of focus detection pixels 222a and 222b according to another embodiment. FIG. 14 is a front view schematically showing the arrangement of focus detection pixels 222a and 222b according to still another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

<<1st Embodiment>>
FIG. 1 is a configuration diagram of a main part showing a digital camera 1 according to an embodiment of the invention. A digital camera 1 (hereinafter simply referred to as camera 1) of this embodiment comprises a camera body 2 and a lens barrel 3. The camera body 2 and lens barrel 3 are detachably connected by a mount portion 4. there is

A 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 incorporates a photographing optical system including lenses 31, 32, 33 and a diaphragm .

The lens 32 is a focus lens, and by moving in the direction of the optical axis L1, it is possible to adjust the focal state of the photographing optical system. The focus lens 32 is provided movably along the optical axis L<b>1 of the lens barrel 3 , and its position is adjusted by a focus lens drive motor 36 while its position is detected by an encoder 35 .

The diaphragm 34 is configured so that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light that passes through the photographing optical system and reach the imaging device 22 and to adjust the amount of blurring. Adjustment of the aperture diameter by the diaphragm 34 is performed by sending an appropriate aperture diameter calculated in the automatic exposure mode, for example, from the camera controller 21 via the lens controller 37 . Further, the set aperture diameter is input from the camera control section 21 to the lens control section 37 by manual operation using the operation section 28 provided in the camera body 2 . The aperture diameter of the aperture 34 is detected by an aperture aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

Based on commands from the camera control unit 21 , the lens control unit 37 controls the entire lens barrel 3 , such as driving the focus lens 32 and adjusting the aperture diameter of the diaphragm 34 .

On the other hand, the camera body 2 is provided with an imaging device 22 for receiving the light flux from the photographic optical system on the predetermined focal plane of the photographic optical system, and a shutter 23 is provided on the front surface thereof. The imaging element 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electrical signal, and sends the electrical signal to the camera control section 21 . The captured image information transmitted to the camera control unit 21 is sequentially transmitted to the liquid crystal drive circuit 25 and displayed in the electronic viewfinder (EVF) 26 of the observation optical system, and the release button ( (not shown) is fully pressed, the captured image information is recorded in the memory 24, which is a recording medium. Note that the memory 24 can be either a detachable card-type memory or a built-in memory. Further, the details of the structure of the imaging device 22 will be described later.

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

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

In addition to the above, the camera control unit 21 detects the focus state of the photographic optical system by the phase detection method and detects the focus state of the photographic optical system by the contrast detection method based on the pixel data read from the imaging device 22. I do. A specific focus state detection method will be described later.

The operation unit 28 is an input switch such as a shutter release button for setting various operation modes of the camera 1 by the photographer, and can switch between autofocus mode and manual focus mode. Various modes set by the operation section 28 are sent to the camera control section 21, and the operation of the camera 1 as a whole is controlled by the camera control section 21. FIG. The shutter release button also 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 imaging device 22 according to this embodiment will be described.

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

As shown in FIG. 3, the imaging device 22 of the present embodiment has a plurality of imaging pixels 221 arranged two-dimensionally on the plane of the imaging surface, and a green pixel G having a color filter that transmits a green wavelength region. , a so-called Bayer arrangement of a red pixel R having a color filter transmitting a red wavelength region and a blue pixel B having a color filter transmitting a blue wavelength region. That is, in four adjacent pixel groups 223 (close-packed square lattice arrangement), 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 groups 223 in a two-dimensional manner on the image pickup surface of the image pickup device 22 with the Bayer-arranged pixel groups 223 as a unit. In this embodiment, the four pixel groups 223 form one pixel.

The arrangement of the unit pixel group 223 may be, for example, a hexagonal lattice arrangement other than the illustrated close-packed square lattice. Also, 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 employed.

FIG. 4A is a front view showing an enlarged image of one of the imaging pixels 221, and FIG. 4D is a cross-sectional view. One imaging pixel 221 is composed of a microlens 2211, a photoelectric conversion unit 2212, and a color filter (not shown). As shown in the cross-sectional view of FIG. A photoelectric conversion portion 2212 is built in, and a microlens 2211 is formed on its surface. The photoelectric conversion unit 2212 is shaped to receive the imaging light flux passing through the exit pupil (for example, F1.0) of the imaging optical system 31 through the microlens 2211, and receives the imaging light flux.

In addition, as shown in FIG. 2, instead of the above-described imaging pixels 221, focus detection pixels are provided at a total of nine locations, i. Focus detection pixel array groups 22a to 22i in which 222a and 222b are arranged are provided. As shown in FIG. 3, each focus detection pixel array group is composed of four focus detection pixel arrays L1 to L4, and each focus detection pixel array L1 to L4 includes a plurality of first focus detection pixels 222a. and second focus detection pixels 222b are arranged adjacent to each other alternately in a horizontal row. Further, as shown in FIG. 3, in the present embodiment, the focus detection pixels 222a and 222b are reversed in the X-axis direction between the focus detection pixel rows L1 and L3 and the focus detection pixel rows L2 and L4. are placed in Furthermore, 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 imaging pixels 221 arranged in the Bayer array. They are densely arranged without any gaps.

Note that the positions of the focus detection pixel array groups 22a to 22i shown in FIG. 2 are not limited to the positions shown in the figure, and may be any one position or two to eight positions, or may be arranged at ten or more positions. You can also In actual focus detection, a desired focus detection pixel group is selected from among the plurality of focus detection pixel array groups 22a to 22i by manually operating the operation unit 28. can also be selected as the focus detection area AFP.

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. 4C is a front view showing an enlarged 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. A photoelectric conversion portion 2222a is formed on the surface of a semiconductor circuit board 2213 of No. 22, and a microlens 2221a is formed on the surface thereof. 4C, the second focus detection pixel 222b is composed of a microlens 2221b and a photoelectric conversion unit 2222b. A photoelectric conversion portion 2222b is formed on the surface of a semiconductor circuit board 2213, and a microlens 2221b is formed on the surface. As shown in FIG. 3, these focus detection pixels 222a and 222b are arranged adjacent to each other alternately in a horizontal row to form focus detection pixel rows L1 to L4.

Note that the photoelectric conversion units 2222a and 2222b of the first focus detection pixel 222a and the second focus detection pixel 222b convert the luminous flux passing through a predetermined region (for example, F2.8) of the exit pupil of the imaging optical system by the microlenses 2221a and 2221b. is shaped to receive the 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 spectral characteristics of an infrared cut filter (not shown). It is a combination of characteristics. However, it can also 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. is not limited to this, and may be other shapes such as a semicircular shape, an elliptical shape, and a polygonal shape.

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

FIG. 5 is a cross-sectional view along line VV in FIG. 3, in which focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 adjacent to each other are arranged near the imaging optical axis L1. Light beams AB1-1, AB2-1, AB1-2, and AB2-2 emitted from ranging pupils 351 and 352 of exit pupil 350 are received, respectively. Although FIG. 5 illustrates only the focus detection pixels 222a and 222b located near the imaging optical axis L1 among the plurality of focus detection pixels 222a and 222b, other focus detection pixels other than the focus detection pixels shown in FIG. are also configured to receive light beams emitted from a pair of distance measuring pupils 351 and 352, respectively.

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 intended focal plane of the imaging optical system. The distance D is a value that is uniquely determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, etc. This distance D is referred to as the ranging pupil distance. Also, the ranging 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 alignment direction of the focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 matches the alignment direction of the pair of distance measuring pupils 351 and 352. FIG.

Further, as shown in FIG. 5, the microlenses 2221a-1, 2221b-1, 2221a-2, and 2221b-2 of the focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 are the imaging optical system. is located near the intended focal plane of . The photoelectric conversion units 2222a-1, 2222b-1, 2222a-2, and 2222b-2 arranged behind the microlenses 2221a-1, 2221b-1, 2221a-2, and 2221b-2 have different shapes. It is projected onto the exit pupil 350 which is separated from the lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 by the range-finding distance D, and the projected shape forms range-finding pupils 351, 352. FIG.

That is, on the exit pupil 350 at the ranging distance D, the microlenses and the photoelectric conversion sections of the focus detection pixels are arranged so that the projection shapes (ranging pupils 351 and 352) of the photoelectric conversion sections of the focus detection pixels match. are determined, and thereby the projection direction of the photoelectric conversion unit in each focus detection pixel is determined.

As shown in FIG. 5, the photoelectric conversion unit 2222a-1 of the first focus detection pixel 222a-1 passes through the rangefinding pupil 351, and the light beam AB1-1 directed to the microlens 2221a-1 causes a outputs a signal corresponding to the intensity of the image formed on the Similarly, the photoelectric conversion unit 2222a-2 of the first focus detection pixel 222a-2 passes through the range finding pupil 351, and the image formed on the microlens 2221a-2 by the light flux AB1-2 directed toward the microlens 2221a-2. output 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 distance measuring pupil 352 and converts the image formed on the microlens 2221b-1 by the light 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 range finding pupil 352, and the image formed on the microlens 2221b-2 by the light flux AB2-2 directed toward the microlens 2221b-2. output a signal corresponding to the intensity of

By grouping the outputs of the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b described above into output groups corresponding to the distance measurement pupil 351 and the distance measurement pupil 352, respectively, Data on the intensity distribution of a pair of images formed on the focus detection pixel row by the focus detection light beams passing through the pupil 352 is obtained.

Then, the camera control unit 21 converts a data string related 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. , while relatively shifting one-dimensionally, the correlation calculation shown in the following equation (1) is performed.
C(k)=Σ|IA _(n+k) −IB _(n) | (1)
In the above equation (1), the Σ operation indicates the cumulative operation (phase sum operation) for n, and the range in which the data of I _{A (n+k)} and I _{B (n)} exist according to the image shift amount k. Limited. Also, the image shift amount k is an integer and is a shift amount in units of pixel intervals between the focus detection pixels 222a and 222b. In addition, in the calculation result of the above formula (1), the amount of correlation C(k) is minimal (the smaller the amount of shift, the higher the degree of correlation) at the amount of shift in which the pair of image data are highly correlated.

Then, the correlation amount C(k) is calculated according to the above equation (1), and the defocus amount df Calculate In the above equation (2), k is a conversion coefficient (k factor) for converting the shift amount x that gives the minimum value C(x) of the correlation amount into the defocus amount.
df=x·k (2)

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

Specifically, the camera control unit 21 acquires the outputs of the focus detection pixel rows L1 to L4 from the image sensor 22, and filters the acquired outputs of the focus detection pixel rows L1 to L4 with a high-frequency transmission filter. , high-frequency components are extracted from the outputs of the focus detection pixel arrays L1 to L4. Then, the camera control unit 21 compares the high-frequency components of the focus detection pixel rows L1 to L4, and, based on the result of the comparison, selects the subject with the highest contrast among the plurality of focus detection pixel rows L1 to L4. A focus detection pixel row is determined as a specific focus detection pixel row. Further, based on the above comparison result, the camera control unit 21 determines the focus detection pixel row whose output contains the most high-frequency components among the plurality of focus detection pixel rows L1 to L4 as the specific focus detection pixel row. may be configured.

In this embodiment, the camera control unit 21 obtains the outputs of the plurality of focus detection pixel arrays L1 to L4 from the image pickup device 22, thereby performing specific focus detection from among the plurality of focus detection pixel arrays L1 to L4. Although the configuration for determining the pixel row has been described as an example, it is not limited to this configuration. Contrast information is detected for each of L1 to L4, a specific focus detection pixel row is determined from among the plurality of focus detection pixel rows L1 to L4 based on the detected contrast information, and the determined specific focus detection pixel row is selected. Information may be configured to be transmitted to the camera control unit 21 .

Then, the camera control unit 21 calculates the defocus amount based on the determined output of the specific focus detection pixel row. 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 detection 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 rows, defocus amounts are calculated for all of the focus detection pixel rows, and the defocus amount used for driving the focus lens 32 is selected from the calculated plurality of defocus amounts. I was choosing the amount of focus. Therefore, conventionally, calculations for defocus amounts other than the selected defocus amount are wasted. However, there is a problem that the calculation time of In contrast, in the present embodiment, the defocus amount is calculated based only on the output of the focus detection pixel row determined as the specific focused pixel row, thereby shortening the time required to calculate the defocus amount. As a result, the time required for focus detection can be shortened.

In this embodiment, a plurality of focus detection areas AFP are set in the imaging screen of the imaging optical system corresponding to the focus detection pixel row groups 22a to 22i of the imaging element 22. A 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 row group 22a as the focus detection area AFP used for focus adjustment, the camera control unit 21 A defocus amount is calculated based on the outputs of the focus detection pixel arrays L1 to L4. Also, the method of setting the focus detection area AFP is not limited to the method selected by the photographer. Alternatively, the focus detection area AFP corresponding to the subject's face may be set as the focus detection area AFP used for focus adjustment. Alternatively, the outputs of the focus detection pixel rows L1 to L4 in all the focus detection areas AFP set in the shooting screen are acquired, and based on the acquired outputs of the focus detection pixel rows L1 to L4, the focus used for focus adjustment is determined. A configuration in which the detection area AFP is set may also be used.

Further, in the present embodiment, the camera control unit 21 performs focus detection by the contrast detection method in addition to focus detection by the phase difference detection method described above. Specifically, the camera control unit 21 reads the output of the image pickup pixel 221 of the image sensor 22, and calculates the focus evaluation value based on the read pixel output. This focus evaluation value can be obtained, for example, by extracting high-frequency components of the image output from the imaging pixels 221 of the imaging device 22 using a high-frequency transmission filter and integrating them. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies and integrating 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 the focus evaluation value at each position, and obtains the focus evaluation value at the maximum. The position of the focus lens 32 where is obtained as the in-focus position. 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. can be obtained by performing a calculation such as an interpolation method using the focus evaluation value of .

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

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

In step S102, the camera control unit 21 selects the focus detection area AFP to be used for focus adjustment. For example, when the photographer sets the focus detection area AFP to be used for focus adjustment via the operation unit 28, the camera control unit 21 sets the focus detection area AFP set by the photographer to the focal point to be used for focus adjustment. It can be selected as detection area AFP. In addition, the camera control unit 21 performs face recognition processing on the image data output from the image pickup device 22 to set the focus detection area AFP corresponding to the face of the subject as the focus detection area AFP used for focus adjustment. It is good also as a structure which selects. Alternatively, the camera control unit 21 selects the focus detection area AFP to be used for focus adjustment by analyzing the outputs of the focus detection pixel arrays 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 contrast information for each of the focus detection pixel rows L1 to L4 based on the outputs of the focus detection pixel rows L1 to L4. Specifically, the camera control unit 21 filters the outputs of the plurality of focus detection pixel arrays L1 to L4 corresponding to the focus detection area AFP selected in step S102 using a high-frequency transmission filter, so that 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 as contrast information for each of the focus detection pixel rows L1 to L4.

In step S104, the camera control unit 21 determines the specific focus detection pixel row. Specifically, based on the contrast information for each of the focus detection pixel rows L1 to L4 detected in step S103, the camera control unit 21 corresponds to the subject with the highest contrast among the plurality of focus detection pixel rows L1 to L4. or the focus detection pixel line whose pixel output contains the most high-frequency components is determined as the specific focus detection pixel line.

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

Focus detection of the optical system according to the first embodiment is performed as described above.

Next, an operation example of the camera 1 according to this embodiment will be described with reference to FIG. FIG. 7 is a diagram for explaining an operation example of the camera 1 according to this embodiment. Also, in FIG. 7, the horizontal axis indicates time, showing a scene where the shutter release button is half-pressed at time t5. 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 electric charges corresponding to incident light. Further, in the present embodiment, the focus detection pixels 222a and 222b are, for example, CMOS image sensors, and in parallel with charge accumulation, transfer of pixel signals corresponding to the amount of charge accumulated after time t1 is started. be. Then, at time t3, the transfer of pixel signals started at time t2 is completed, and contrast information detection and specific focus detection pixel rows are determined (steps S103 and S104). Then, at time t4, calculation of the defocus amount is started based on the determined output of the specific focus detection pixel row (step S105). As a result, the lens drive amount is calculated, and at time t6 after the lens drive amount is calculated, a lens drive instruction is sent to the lens barrel 3, and the focus lens 32 is driven. Here, in the example shown in FIG. 7, the shutter release button is half-pressed at time t5 before the instruction to drive the lens is issued. starts to drive.

Further, in the present embodiment, even after the shutter release button is half-pressed, the calculation of the defocus amount is repeatedly performed according to the frame rate of the image sensor 22, and based on the calculated defocus amount, the focus lens 32 driving instructions are repeated. For example, in the example shown in FIG. 7, at time t2, the charge accumulation for the second frame is started, and as a result, the defocus amount for the second frame is calculated at time t7, and the second frame A drive instruction for the focus lens 32 is issued based on the output results of the eye focus detection pixel arrays L1 to L4. Similarly, from the third frame onward, calculation of the defocus amount and 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 rows L1 to L4.

As described above, in this embodiment, calculation of the defocus amount and driving of the focus lens 32 based on the defocus amount are repeated for each frame according to the frame rate of the imaging device 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 calculation of the defocus amount and the instruction to drive the focus lens 32 within the time of one frame. There is In this regard, in the present embodiment, one specific focus detection pixel row is determined based on contrast information, and the defocus amount is calculated only for the output of this specific focus detection pixel row, as shown in FIG. Since the time required to calculate the defocus amount can be shortened, the defocus amount can be calculated within the time of one frame, 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, the horizontal axis indicates time. In the example shown in FIG. 8, the calculation of the defocus amount, which takes a relatively long time, is performed for all the focus detection pixel rows L1 to L4. become longer. As a result, in the example shown in FIG. 8, compared to the present embodiment shown in FIG. 7, the time required from the calculation of the defocus amount to the instruction to drive the lens is longer than the time for one frame of the frame rate. , it may become impossible to issue a lens driving instruction for each frame. Specifically, in the example shown in FIG. 8, it is not possible to perform operations from the calculation of the defocus amount to the instruction to drive the lens within the time for one frame. , the time lag T2 from the charge accumulation to the instruction to drive the focus lens 32 is doubled.

As a result, in the example shown in FIG. 8, at time t12, driving of the focus lens 32 is instructed based on the focus state of the optical system at time t11. There have been cases where the camera is driven, and there are cases where the ability to follow the subject is degraded. On the other hand, in the present embodiment, as shown in FIG. 7, based on the focus state of the optical system at time t9, at time t10 with little time lag, the focus lens 32 can be instructed to drive. As 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, contrast information is detected for each of the focus detection pixel rows L1 to L4 based on the outputs of the focus detection pixel rows L1 to L4 within the focus detection area AFP. Then, a focus detection pixel row to be used for focus detection is determined based on the detected contrast information. That is, among the plurality of focus detection pixel rows L1 to L4, the focus detection pixel row corresponding to the subject with the highest contrast or the focus detection pixel row whose pixel output contains the most high frequency components is selected for specific focus detection. A pixel row is determined, and the defocus amount is determined only for this specific focus detection pixel row. As a result, it is possible to detect the focus state of the optical system for a subject with the highest contrast or a subject with the highest number of high-frequency components. Compared to the case of calculating the focus amount, the time required for calculating the defocus amount can be shortened, and the detection of the focus state can be repeatedly performed at appropriate timing.

In addition, in the first embodiment, the defocus amount is calculated based on the output of one focus detection pixel row among the outputs of the plurality of focus detection pixel rows L1 to L4. The following effects can be obtained as compared with the case of adding or averaging the outputs of L1 to L4. That is, when the subject has contrast in the oblique direction of the imaging pixels 221, adding or averaging the outputs of the plurality of focus detection pixel arrays L1 to L4 may rather reduce the contrast. It may not be detected properly. In contrast, in the present embodiment, the defocus amount is calculated based on the output of one specific focus detection pixel row. can be effectively detected.

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

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

Then, the camera control unit 21 selects one or a plurality of focus detection pixel rows L1 to L4 used for focus detection from among the plurality of focus detection pixel rows L1 to L4 based on the plurality of pieces of contrast information as specific focus detection pixels. Detect as columns. For example, the camera control unit 21 selects one or a plurality of focus detection pixel rows for which the magnitude of the contrast of the corresponding object is equal to or greater than a predetermined value from among the plurality of focus detection pixel rows L1 to L4 as a specific focus detection pixel row. can be detected as Alternatively, the camera control unit 21 can detect one or a plurality of focus detection pixel rows whose output contains a high-frequency component amount equal to or greater than a predetermined value as a specific focus detection pixel row.

When determining the specific focus detection pixel array, the camera control unit 21 sets the number of specific focus detection pixel arrays to be less than the number of focus detection pixel arrays L1 to L4 corresponding to the focus detection area AFP. Next, a specific focus detection pixel row is determined. For example, in the present embodiment, since four focus detection pixel rows L1 to L4 are arranged in the focus detection area AFP, the camera control unit 21 controls the number of specific focus detection pixel rows to be at least three or less. Next, a specific focus detection pixel row is determined.

Then, when a plurality of focus detection pixel rows are determined as specific focus detection pixel rows, the camera control unit 21 adds or averages the outputs of the plurality of specific focus detection pixel rows, and adds or averages the outputs of the plurality of specific focus detection pixel rows. A defocus amount is calculated based on the output of the focus detection pixel array. Here, FIG. 9 shows only the first focus detection pixel 222a and the second focus detection pixel 222b that constitute the four focus detection pixel rows L1 to L4, excluding the imaging pixel 221 from the imaging surface of the imaging device 22 shown in FIG. It is a diagram schematically showing the. For example, when adding the outputs of a plurality of specific focus detection pixel arrays, the camera control unit 21 sets the outputs of the pixels A1 to _L1 of the first focus detection pixel array L1 shown in FIG. The outputs of the pixels A1 to _L2 of the second focus detection pixel row L2, the outputs of the pixels A1 to L3 of the third focus detection pixel row _L3 , and the pixels A1 to _L3 of the fourth focus detection pixel row L4, which receive the passing focus detection light flux. to obtain the pixel sum output I _A1 . Similarly, the outputs of the pixels B1 to _L1 of the first focus detection pixel row L1, the outputs of the pixels B1 to _L2 of the second focus detection pixel row L2 that receive the focus detection light flux passing through the same ranging pupil, and the The outputs of the pixels B1 to _L3 of the 3rd focus detection pixel array L3 and the outputs of the pixels _B1 to _L4 of the 4th focus detection pixel array L4 are added to obtain the pixel added output IB1. Similarly, I _A2 is generated from the outputs of A2 _L1 , A2 _L2 , A2 _L3 , and A2 _L4 , I _B2 is generated from the outputs of B2 _L1 , B2 _L2 , B2 _L3 , and B2 _L4 , and A3 _L1 , A3 _L2 , and A3 I _A3 is obtained from the outputs of _L3 and A3 _L4 , and I _B3 is obtained 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 generate data strings based on the first focus detection pixels 222a, that is, the first image data strings I _A1 , I _A2 , I _A3 , . . . , I _An and a data string based on the second focus detection pixels 222b, that is, the second image data strings I _B1 , I _B2 , I _B3 , . . . , I _Bn are relatively shifted one-dimensionally, and the correlation calculation shown in the above equation (1) is performed.

Here, as shown in FIG. 3, in the focus detection pixel rows 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. there is Conventionally, only one of the first focus detection pixel row L1 and the second focus detection pixel row L2 of the present embodiment is used as the focus detection pixel row. 2 focus detection pixels 222b are present at positions shifted by 0.5 pixels from each other, and the first image data arrays I _A1 , I _A2 , I _A3 , . . . , I _An and the second image data sequences I _B1 , I _B2 , I _B3 , . . . , and _IBn are data shifted by 0.5 pixels from 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, it is necessary to use an interpolation operation or the like in order to calculate the shift amount and the defocus amount at which the correlation amount C(k) exhibits the minimum value. There was a case. In particular, when the contrast level of the output detected by the focus detection pixels is low, such a problem tends to become conspicuous.

In contrast, in the present embodiment, in the focus detection pixel rows L1, L3 and the focus detection pixel rows L2, L4, the first focus detection pixel 222a and the second focus detection pixel 222b are 0.0 in the X-axis direction. Since the positions are shifted by 5 pixels, when the pixel added output obtained by adding the pixel outputs is used, as shown in FIG. ), the amount of shift that gives the minimum value of the correlation amount C(k) can be accurately obtained, thereby appropriately enhancing the accuracy of focus detection.

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

In step S201, as in step S101 of the first embodiment, the imaging element 22 detects the image pickup pixel 221, and the first focus detection pixels 222a and the second focus detection pixels 222a and 222a forming the plurality of focus detection pixel rows L1 to L4. 222b output data acquisition is performed. Also, in step S202, the camera control unit 21 selects the focus detection area AFP to be used for focus adjustment, as in step S102 of the first embodiment.

Then, in step S203, the camera control unit 21 detects contrast information. In the second embodiment, the camera control unit 21 uses a plurality of filters for extracting frequency components in different frequency bands to filter the outputs of the focus detection pixel arrays L1 to L4, so that each focus detection pixel A plurality of frequency components are extracted from each output of columns L1-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 a specific focus detection pixel row based on the plurality of pieces of contrast information detected in step S203. Specifically, based on the contrast information detected in step S203, the camera control unit 21 selects one or more focal points for which the contrast of the corresponding object is equal to or higher than a predetermined value among the plurality of focus detection pixel rows L1 to L4. A detection pixel row is determined as a specific focus detection pixel row. Alternatively, the camera control unit 21 selects, based on the plurality of pieces of contrast information detected in step S203, one or more of the plurality of focus detection pixel rows L1 to L4 whose output contains a high-frequency component amount equal to or greater than a predetermined value. is determined as a specific focus detection pixel row.

Then, in step S205, the camera control unit 21 calculates the defocus amount used to drive the focus lens 32 based on the one or more specific focus detection pixel rows determined in step S204. For example, when a plurality of focus detection pixel rows are determined as specific focus detection pixel rows, the camera control unit 21 adds or averages the outputs of the plurality of specific focus detection pixel rows to calculate an output of 1. Then, based on this output, the defocus amount used for driving the focus lens 32 can be calculated.

In step S206, the driving 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 in step S106 of the first embodiment.

Focus detection of the optical system according to the second embodiment is performed as described above.

As described above, in the second embodiment, frequency components in different frequency bands are extracted based on the outputs of the focus detection pixel arrays L1 to L4 for each of the focus detection pixel arrays L1 to L4, and the extracted frequency components are divided into Based on this, a plurality of pieces of contrast information are detected. Then, based on the plurality of pieces of contrast information, one or more specific focus detection pixel rows are determined from among the focus detection pixel rows L1 to L4, and defocus is performed based on the pixel output of the determined specific focus detection pixel row. Determine quantity. Thus, in the second embodiment, the defocus amount is not calculated for all the focus detection pixel rows L1 to L4, but for specific focus detection pixel rows less than the number of focus detection pixel rows L1 to L4. By calculating the defocus amount, it is possible to shorten the calculation time of the defocus amount, and as a result, it is possible to repeatedly detect the focus state at an appropriate timing.

Although the embodiments of the present invention have been described above, the above-described embodiments are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, in the above-described embodiment, one focus detection area AFP includes four focus detection pixel rows L1 to L4, but the number of focus detection pixel rows is not limited to this. The number of focus detection pixel rows in the focus detection area may be 2 or 3, or may be 5 or more.

Further, in the above-described embodiment, the image sensor 22 is provided with the focus detection pixel rows L1 to L4, and the defocus amount is calculated based on the outputs of the focus detection pixel rows L1 to L4. Without limitation, for example, a phase difference AF detection module may be provided separately from the imaging device 22, and the defocus amount may be calculated based on the received light signal received by this phase difference AF detection module. Specifically, the phase-difference AF detection module has a plurality of pairs of line sensors that receive light beams passing through the optical system, detects contrast information for each line sensor, and detects contrast information based on the detected contrast information. A pair of line sensors to be used for focus detection may be determined from among a plurality of line sensors. When determining the pair of line sensors to be used for focus detection, the pair of line sensors to be used for focus detection may be determined by a calculation unit provided in the phase difference detection module, or the camera control unit 21 However, the pair of line sensors to be used for focus detection may be determined by acquiring the output of each pair of line sensors.

Thus, the "light receiving sensor" of the present invention may be the focus detection pixel arrays L1 to L4, or may be the pair of line sensors described above. Further, the "focus detection device" of the present invention may be the image sensor 22 or the camera 1 including it, or may be the phase difference AF detection module or the camera 1 including it.

Furthermore, in the above-described embodiment, the first focus detection pixel 222a and the second focus detection pixel 222b are arranged oppositely in the X-axis direction in the focus detection pixel rows L1, L3 and the focus detection pixel rows L2, L4. However, it is not limited to this configuration. For example, as shown in FIG. 12, focus detection pixels 222a and 222b constituting focus detection pixel rows L1a to L4a are arranged at the same position in the X-axis direction. may be configured.

Also, as shown in the focus detection pixel rows L1b and L2b in FIG. 13, each of the focus detection pixels 222a and 222b may have a pair of photoelectric conversion units 2222a and 2222b. Specifically, as shown in FIG. 13, in each of the focus detection pixels 222a and 222b, a pair of photoelectric conversion units 2222a and 2222b are arranged in the X-axis direction, and the luminous flux emitted from the distance measuring pupil 351 is converted into a pair of A light beam 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. As a result, a pair of image data columns can be output from each of the focus detection pixel columns L1b and L2b. In FIG. 13, the photoelectric conversion units that receive the light beam emitted from the ranging pupil 351 are indicated in gray, and the photoelectric conversion units that receive the light beam emitted from the ranging pupil 352 are indicated in white.

Furthermore, the arrangement of the first focus detection pixels 222a and the second focus detection pixels 222b that constitute each focus detection pixel row may be at least as long as they are arranged alternately on the same row. 3, the focus detection pixel arrays may include normal imaging pixels 221, such as the focus detection pixel arrays L1c to L4c shown in FIG.

Further, in addition to the above-described embodiments, when the contrast of the subject (or the brightness of the subject) is equal to or higher than a predetermined value, as shown in the first embodiment, among the focus detection pixel rows L1 to L4, the contrast is The focus detection pixel row corresponding to the largest subject or the focus detection pixel row whose output contains the most high-frequency components is determined as the specific focus detection pixel row. If it is less than the value, as shown in the second embodiment, one or a plurality of focus detection pixel rows among the focus detection pixel rows L1 to L4 for which the contrast of the corresponding object is equal to or higher than a predetermined value, or A configuration may be adopted in which one or a plurality of focus detection pixel rows whose outputs contain high-frequency components equal to or greater than a predetermined value are determined as specific focus detection pixel rows.

DESCRIPTION OF SYMBOLS 1... Digital camera 2... Camera body 21... Camera control part 22... Imaging element 221... Imaging pixel L1-L4... Focus detection pixel row 222a, 222b... Focus detection pixel 3... Lens barrel 32... Focus lens 36... Focus lens drive Motor 37... Lens control unit

[1] A focus detection device according to the present invention receives light that has passed through an optical system, outputs a signal used for focus detection by the optical system, and detects a plurality of pixels included in a first region or a second region. and an imaging element included in the first region based on signals output from the plurality of pixels included in the first region and signals output from the plurality of pixels included in the second region a detection unit that selects signals output from the plurality of pixels or signals output from the plurality of pixels included in the second region to perform focus detection of the optical system .
[2] In the invention related to the focus detection device, the detection unit includes signals output from the plurality of pixels included in the first region and signals output from the plurality of pixels included in the second region. Based on the magnitude of the signal, signals output from the plurality of pixels included in the first region or signals output from the plurality of pixels included in the second region are selected to focus the optical system. Detection may be performed.
[3] In the invention related to the focus detection device, the detection unit includes signals output from the plurality of pixels included in the first region and signals output from the plurality of pixels included in the second region. The focus detection of the optical system may be performed by selecting the larger signal among the signals .
[4] In the invention related to the focus detection device, the detection unit includes signals output from the plurality of pixels included in the first region and signals output from the plurality of pixels included in the second region. Focus of the optical system by selecting signals output from the plurality of pixels included in the first region or signals output from the plurality of pixels included in the second region based on high frequency components of the signals Detection may be performed .
[5] In the invention related to the focus detection device, the detection unit includes signals output from the plurality of pixels included in the first region and signals output from the plurality of pixels included in the second region. Based on different frequency components of the signals, the signals output from the plurality of pixels included in the first region or the signals output from the plurality of pixels included in the second region are selected to operate the optical system. Focus detection may be performed.
[6] The focus detection device may include a face detection section for detecting a face, and the first area and the second area may be included in areas where the face is detected by the face detection section.
[7] In the invention related to the focus detection device, a designating unit for designating a specific region among the imaging regions of the imaging element is provided, and the first region and the second region are designated by the designating unit. may be included in the area.
[8] In the invention related to the focus detection device, the plurality of pixels include pixels that receive light that has passed through a first pupil of the optical system and pixels that receive light that has passed through a second pupil of the optical system. It may have pixels that
[9] A focus detection device according to the present invention receives light that has passed through an optical system, outputs a signal used for focus detection by the optical system, and detects a plurality of pixels included in a first region or a second region. and an imaging unit included in the first region based on signals output from the plurality of pixels included in the first region and signals output from the plurality of pixels included in the second region an output unit that selects and outputs signals output from the plurality of pixels or signals output from the plurality of pixels included in the second region.

Claims (1)

an image pickup device having a plurality of regions in which a plurality of pixel groups each composed of a plurality of pixels for receiving light from an object that has passed through an optical system and outputting a signal based on the received light are arranged;
based on the signals output from the pixel groups less than the number of the pixel groups arranged in one of the regions, selected based on the contrast of the signals output from the pixel groups; A focus detection device, comprising: a detection unit that detects the focus state of the image of the subject formed by the system.

Images