JP2019061264A - Focus detector, camera, and electronic apparatus - Google Patents

Abstract

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

Description

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

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

Unexamined-Japanese-Patent No. 2003-215437

  However, in the prior art, since the defocus amount is calculated for all the plurality of light receiving sensors, it takes time to calculate the defocus amount, and as a result, it is possible to repeatedly detect the focus state of the optical system at appropriate timing. I could not do it.

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

  The present invention solves the above-mentioned subject by the following solution means.

[1] A focus detection device according to the present invention has a plurality of regions in which a plurality of pixel groups each including a plurality of pixels that receives light of an object passing through an optical system and outputs a signal based on the received light are arranged. Based on the imaging element and the signals output from a number of pixel groups smaller 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 group And a detection unit that detects the in-focus state of the image of the subject formed by the optical system.
[2] In the invention according to the above-described 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 deviation between the position of the image of the subject and the imaging surface of the imaging device. It is also good.
[3] In the invention according to the focus detection device, the detection unit may select one of the pixel groups, and calculate the defocus amount based only on the signal output from the selected pixel group. .
[4] In the invention according to the focus detection device, the detection unit selects a plurality of the pixel groups whose number is smaller than the number of the pixel groups arranged in one focus detection area, and the selected pixel group The defocus amount may be calculated based on any one of an added value and an average value of the output signals of
[5] In the invention according 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 the signal output from the pixel group. May be
[6] In the invention relating to the focus detection device, the pixel group includes a plurality of pixels for receiving light passing through the first pupil of the optical system, and light passing through the second pupil of the optical system. It may have a plurality of light receiving pixels.
[7] In the invention according to the above-described focus detection device, the detection unit selects the pixel group for calculating the defocus amount from among the plurality of parallel pixel groups arranged in one area. It is also good.
[8] A camera according to the present invention includes the above-described focus detection device.
[9] An electronic device according to the present invention includes the above-described focus detection device.

  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 the present embodiment. FIG. 2 is a front view showing an imaging surface of the imaging device shown in FIG. FIG. 3 is a front view schematically showing an arrangement of the imaging pixel 221 and the focus detection pixels 222a and 222b by enlarging the part III 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. 4C. 4A is a front view showing an enlarged view of one of the second focus detection pixels 222b, FIG. 4D is a sectional view showing an enlarged view of one of the imaging pixels 221, and FIG. 4E shows a first focus FIG. 4F is a cross-sectional view showing one of the second focus detection pixels 222b in an enlarged manner. 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 view schematically showing the arrangement of the first focus detection pixels 222a and the second focus detection pixels 222b according to the present embodiment. FIG. 10 (A) is a graph showing the relationship between the correlation amount and the shift amount in the present embodiment, and FIG. 10 (B) 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 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.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

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

  The lens barrel 3 is an interchangeable lens that is detachable 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 34.

  The lens 32 is a focus lens, and can move in the direction of the optical axis L1 to adjust the focus state of the photographing optical system. The focus lens 32 is provided so as to be movable 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 to adjust the aperture diameter centered on the optical axis L1 in order to limit the light amount of the light flux passing through the imaging optical system and reaching the imaging device 22 and to adjust the blur amount. Adjustment of the aperture diameter by the aperture stop 34 is performed, for example, by transmitting 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 the manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the diaphragm 34 is detected by a diaphragm aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

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

  On the other hand, in the camera body 2, an image pickup element 22 for receiving the light flux from the photographing optical system is provided on a planned focal plane of the photographing optical system, and a shutter 23 is provided in front of it. The imaging device 22 is configured of a device such as a CCD or a CMOS, converts the received light signal into an electric signal, and sends it to the camera control unit 21. The photographed 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 (provided in the operation unit 28) When the full depression (not shown) is performed, the photographed image information is recorded in the memory 24 which is a recording medium. The memory 24 may be either a removable card type memory or a built-in type memory. 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 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 same, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the photographed image information picked up by the image pickup device 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on this. Thus, the user can observe the current captured image through the eyepiece 27. A liquid crystal display may be provided on the back surface of the camera body 2 or the like instead of or in addition to the above observation optical system according to the optical axis L2, and a photographed image may be displayed on the liquid crystal display.

  A camera control unit 21 is provided in the camera body 2. The camera control unit 21 receives various lens information and transmits information such as the defocus amount and the aperture diameter to the lens control unit 37. In addition, as described above, the camera control unit 21 reads out the pixel output from the imaging device 22 and generates image information by performing predetermined information processing on the read out pixel output as necessary, and the generated image information Are 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 such as correction of image information from the image pickup device 22 and detection of a focusing state of the lens barrel 3, an aperture adjusting state, and the like.

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

  The operation unit 28 is an input switch for a photographer such as a shutter release button to set various operation modes of the camera 1, and can switch between an auto focus mode and a manual focus mode. The 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 which is turned on when the button is half pressed, and a second switch SW2 which is turned on when the button is fully pressed.

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

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

  As shown in FIG. 3, in the imaging device 22 of the present embodiment, a plurality of imaging pixels 221 are two-dimensionally arranged on a plane of an imaging surface, and a green pixel G having a color filter transmitting a green wavelength region And a red pixel R having a color filter transmitting the red wavelength region and a blue pixel B having a color filter transmitting the blue wavelength region are what is called a Bayer arrangement. That is, two green pixels are arranged on one diagonal line in adjacent four pixel groups 223 (a dense square lattice array), and one red pixel and one blue pixel are arranged on the other diagonal line. The imaging element 22 is configured by repeatedly arranging the pixel group 223 two-dimensionally on the imaging surface of the imaging element 22 in units of the pixel group 223 in which the Bayer arrangement is performed. In the present embodiment, one pixel is formed by the four pixel groups 223.

  The arrangement of the unit pixel groups 223 may be, for example, a close hexagonal lattice arrangement, as well as the close square lattice shown in the drawing. Further, the configuration and arrangement of the color filter are not limited to this, and an arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) can also 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 imaging pixel 221 includes a microlens 2211, a photoelectric conversion unit 2212, and a color filter (not shown), and as shown in the cross-sectional view of FIG. 4D, on the surface of the semiconductor circuit substrate 2213 of the imaging element 22. The photoelectric conversion portion 2212 is fabricated, and the micro lens 2211 is formed on the surface thereof. The photoelectric conversion unit 2212 is shaped so as to receive the imaging light flux passing through the exit pupil (for example, F1.0) of the photographing optical system 31 by the microlens 2211 and receives the imaging light flux.

  Further, as shown in FIG. 2, in place of the imaging pixel 221 described above at the center of the imaging surface of the imaging device 22 and positions symmetrical to the left and right from the center and their vertically symmetrical positions, focus detection pixels are substituted. Focus detection pixel column groups 22a to 22i in which 222a and 222b are arranged are provided. Then, as shown in FIG. 3, each focus detection pixel column group includes four focus detection pixel columns L1 to L4, and each focus detection pixel column L1 to L4 includes a plurality of first focus detection pixels 222a. The second focus detection pixels 222b are arranged adjacent to each other and alternately arranged in a line. Further, as shown in FIG. 3, in the present embodiment, the focus detection pixels 222a and the focus detection pixels 222b are reversed in the X-axis direction in the focus detection pixel arrays L1 and L3 and the focus detection pixel arrays L2 and L4. Is located in Furthermore, in the present embodiment, as shown in FIG. 3, the first focus detection pixel 222a and the second focus detection pixel 222b form a gap at the positions of the green pixel G and the blue pixel B of the imaging pixel 221 in Bayer arrangement. They are closely arranged without provision.

  Note that the positions of the focus detection pixel column groups 22a to 22i shown in FIG. 2 are not limited to the positions shown in the figure, but may be any one position or 2 to 8 positions, etc. You can also Further, at the time of actual focus detection, in order to perform focus adjustment of a desired focus detection pixel group by the photographer manually operating the operation unit 28 among the plurality of arranged focus detection pixel column groups 22a to 22i. It 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 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. The first focus detection pixel 222a includes a micro lens 2221a and a rectangular photoelectric conversion unit 2222a as shown in FIG. 4B, and as shown in the cross sectional view of FIG. A photoelectric conversion portion 2222a is formed on the surface of the twenty-two semiconductor circuit substrates 2213, and a micro lens 2221a is formed on the surface. The second focus detection pixel 222b is composed of a micro lens 2221b and a photoelectric conversion unit 2222b as shown in FIG. 4C, and as shown in the cross sectional view of FIG. The photoelectric conversion portion 2222 b is formed on the surface of the semiconductor circuit substrate 2213, and the micro lens 2221 b is formed on the surface. The focus detection pixels 222a and 222b are arranged adjacent to each other and alternately in a horizontal row, as shown in FIG. 3, to form each focus detection pixel row 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 luminous fluxes passing through a predetermined area (for example, F2.8) of the exit pupil of the photographing optical system by the micro lenses 2221a and 2221b. Is shaped to receive light. Further, no color filter is provided in the first focus detection pixel 222a and the second focus detection pixel 222b, and the 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 has become a synthesis of the characteristics. However, one of the same color filters as the imaging pixel 221, for example, a green filter may be provided.

  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. 4B and 4C are rectangular, the shapes of the photoelectric conversion units 2222a and 2222b are shown. Is not limited to this, and may be another shape, for example, a semicircular shape, an elliptical shape, or a polygonal shape.

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

  FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 3 and is disposed in the vicinity of the photographing optical axis L1 and the focus detection pixels 222a-1, 222b-1, 222a-2, 222b-2 adjacent to each other are It shows that light beams AB1-1, AB2-1, AB1-2, and AB2-2 emitted from the focusing pupils 351 and 352 of the exit pupil 350 are respectively received. Although FIG. 5 illustrates only one of the plurality of focus detection pixels 222a and 222b located in the vicinity of the photographing optical axis L1, other focus detection pixels other than the focus detection pixels shown in FIG. 5 are shown. Similarly, the light beams emitted from the pair of distance measuring pupils 351 and 352 are also received.

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

  In FIG. 5, the arrangement direction of the focus detection pixels 222 a-1, 222 b-1, 222 a-2 and 222 b-2 coincides with the arrangement direction of the pair of distance measurement pupils 351 and 352.

  In addition, 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 photographing optical systems. It is placed near the planned focal plane of. The shape of each of the photoelectric conversion units 2222a-1, 2222b-1, 2222a-2, 2222b-2 disposed behind the microlenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 is The light is projected onto the exit pupil 350 separated by the distance measurement distance D from the lenses 2221a-1 and 2221b-1, and 2221a-2 and 2221b-2, and the projected shapes form distance measurement pupils 351 and 352.

  That is, on the exit pupil 350 located at the distance measurement distance D, the microlenses and photoelectric conversion units in each focus detection pixel are matched so that the projection shapes (distance measurement pupils 351, 352) of the photoelectric conversion units of each focus detection pixel match. The relative positional relationship of is determined, whereby the projection direction of the photoelectric conversion unit at each focus detection pixel is determined.

  As shown in FIG. 5, the photoelectric conversion unit 2222 a-1 of the first focus detection pixel 222 a-1 passes through the distance measurement pupil 351 and is directed to the microlens 2221 a-1 by the light beam AB 1-1 directed to the microlens 2221 a-1. Output 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 distance measuring pupil 351 and forms an image formed on the microlens 2221a-2 by the light beam AB1-2 directed to the microlens 2221a-2. Output a signal corresponding to the intensity of

  In addition, the photoelectric conversion unit 2222b-1 of the second focus detection pixel 222b-1 passes through the distance measurement pupil 352, and an image formed on the microlens 2221b-1 by the light beam AB2-1 directed to the microlens 2221b-1. Output a signal corresponding to the intensity. Similarly, the photoelectric conversion unit 2222b-2 of the second focus detection pixel 222b-2 passes through the distance measurement pupil 352, and forms an image formed on the microlens 2221b-2 by the light beam AB2-2 directed to the microlens 2221b-2. Output a signal corresponding to the intensity of

  Then, by combining the outputs of the photoelectric conversion units 2222 a and 2222 b of the focus detection pixels 222 a and 222 b 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 Data regarding the intensity distribution of a pair of images formed on the focus detection pixel array by focus detection light beams passing through each of the pupils 352 is obtained.

Then, the camera control unit 21 generates 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 in the focus detection pixel string and a data string based on the second focus detection pixel 222b. The correlation operation shown in the following equation (1) is performed while relatively shifting in a one-dimensional manner.
C (k) =. SIGMA. | IA _{(n + k)} -IB _(n) | (1)
In the above equation (1), the Σ operation represents the cumulative operation (phase-sum operation) for _{n, and} in the range in which data of I _{A (n + k)} and I _{B (n)} exist according to the image shift amount k. It is limited. The image shift amount k is an integer, and is a shift amount in units of the pixel interval of each of the focus detection pixels 222a and 222b. In the calculation result of the equation (1), the correlation amount C (k) becomes minimum (the smaller the degree of correlation, the higher the degree of correlation) in the shift amount where 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) on the basis of the shift amount x from which the minimum value C (x) of the correlation amount is obtained. Calculate In the above equation (2), k is a conversion factor (k factor) for converting the shift amount x for obtaining 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 arrays L1 to L4, and the focus detection pixels used to calculate the defocus amount based on the detected contrast information. A row is determined as a specific focus detection pixel row.

  Specifically, the camera control unit 21 obtains the output of each of the focus detection pixel rows L1 to L4 from the imaging element 22, and filters the obtained output of the focus detection pixel rows L1 to L4 with a high frequency transmission filter. Then, 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 comparison result, corresponds to the subject with the largest contrast among the plurality of focus detection pixel rows L1 to L4. The focus detection pixel row is determined as the specific focus detection pixel row. Further, the camera control unit 21 determines, as the specific focus detection pixel row, the focus detection pixel row whose output includes the most high frequency components among the plurality of focus detection pixel rows L1 to L4 based on the comparison result. It is good also as composition.

  In the present embodiment, the camera control unit 21 obtains the outputs of the plurality of focus detection pixel rows L1 to L4 from the imaging device 22 to detect a specific focus from among the plurality of focus detection pixel rows L1 to L4. Although the configuration for determining the pixel array has been described as an example, the present invention is not limited to this configuration, and for example, the point detection pixel array may be calculated by the operation unit of the imaging device 22 based on the outputs of the focus detection pixel arrays L1 to L4. Contrast information is detected for each of L1 to L4, and 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 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 row. As described above, in the present embodiment, the defocus amount is calculated based on only the output of the focus detection pixel row determined as the specific focus out 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 arrays, the defocus amount is calculated for all the focus detection pixel arrays, and the defocus lens used for driving the focus lens 32 among the calculated 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 arrays L1 to L4. There was a problem that the calculation time of would be long. On the other hand, in the present embodiment, calculation of the defocus amount is performed based only on the output of the focus detection pixel row determined as the specific focus out pixel row, so the time taken to calculate the defocus amount is shortened. As a result, the time required for focus detection can be shortened.

  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 column groups 22a to 22i of the image sensor 22, and the photographer performs the operation The focus detection area AFP used for focusing can be set via the unit 28. For example, when the photographer selects the focus detection area AFP corresponding to the focus detection pixel array group 22a as the focus detection area AFP used for focusing, the camera control unit 21 is included in the focus detection pixel array group 22a. The defocus amount is calculated on the basis of the outputs of the focus detection pixel arrays L1 to L4 to be obtained. 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 image data output from the imaging device 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 outputs of the focus detection pixel arrays L1 to L4 in all the focus detection areas AFP set in the shooting screen are acquired, and the focus used for focusing based on the acquired outputs of the focus detection pixel arrays L1 to L4. The detection area AFP may be set.

  Further, in the present embodiment, in addition to the focus detection by the phase difference detection method described above, the camera control unit 21 also performs the focus detection by the contrast detection method. Specifically, the camera control unit 21 reads the output of the imaging pixel 221 of the imaging element 22, and calculates the focus evaluation value based on the read pixel output. The focus evaluation value can be obtained, for example, by extracting the high frequency component of the image output from the imaging pixel 221 of the image sensor 22 using a high frequency transmission filter and integrating the same. It can also be determined 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) to obtain a focus evaluation value at each position, and the focus evaluation value is maximum. The position of the focus lens 32 which becomes is determined as the in-focus position. It should be noted that, for example, when the focus evaluation value is calculated while driving the focus lens 32, the in-focus position is further lowered twice after the focus evaluation value rises twice. It can obtain | require by performing calculations, such as an interpolation method, using the focus evaluation value of.

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

  First, in step S101, output data of the imaging pixel 221 and each of the first focus detection pixels 222a and the second focus detection pixels 222b constituting the plurality of focus detection pixel rows L1 to L4 is acquired by the imaging element 22. .

  In step S102, the camera control unit 21 selects a focus detection area AFP to be used for focusing. For example, when the photographer sets the focus detection area AFP used for focusing through the operation unit 28, the camera control unit 21 uses the focus detection area AFP set by the photographer for focusing. It can be selected as the detection area AFP. Further, the camera control unit 21 performs a face recognition process on the image data output from the imaging 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 may be a configuration to select. Alternatively, the camera control unit 21 selects the focus detection area AFP used for focusing 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. It 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 rows L1 to L4 corresponding to the focus detection area AFP selected in step S102 by using a high frequency transmission filter to obtain a focus detection pixel row The 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 the intensity of the extracted high-frequency component as contrast information for each of the focus detection pixel arrays 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 largest contrast among the plurality of focus detection pixel rows L1 to L4. The focus detection pixel row to be set or the focus detection pixel row in which the high frequency component is most included in the pixel output is determined as the specific focus detection pixel row.

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

  As described above, 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 based on FIG. 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 has been half-pressed at time t5 is shown. For example, in the example illustrated in FIG. 7, at time t1, the focus detection pixels 222a and 222b of the image sensor 22 start to store charges according to incident light. Further, in the present embodiment, the focus detection pixels 222a and 222b are, for example, CMOS image sensors, and transfer of pixel signals according to the amount of charges accumulated after time t1 is started in parallel with the accumulation of charges. Ru. Then, at time t3, transfer of the pixel signal started at time t2 is ended, and detection of contrast information and determination of a specific focus detection pixel row are performed (steps S103 and S104). Then, at time t4, calculation of the defocus amount is started based on the output of the determined specific focus detection pixel column (step S105). As a result, the lens drive amount is calculated, and after the lens drive amount is calculated, at time t6, a lens drive instruction is transmitted to the lens barrel 3 and the focus lens 32 is driven. Here, in the example shown in FIG. 7, since the shutter release button is pressed halfway at time t5 before the lens drive instruction is issued, the focus lens 32 is selected based on the lens drive instruction at time t6. Driving of is started.

  Further, in the present embodiment, the defocus amount is repeatedly calculated according to the frame rate of the image sensor 22 even after the shutter release button is half-pressed, and the focus lens is calculated based on the calculated defocus amount. 32 driving instructions are repeatedly performed. For example, in the example shown in FIG. 7, the accumulation of the charge of the second frame is started at time t2, and as a result, the defocus amount of the second frame is calculated at time t7. An instruction to drive the focus lens 32 is issued based on the output results of the focus detection pixel arrays L1 to L4 of the eyes. Similarly, in the third and subsequent frames, calculation of the defocus amount and drive of the focus lens 32 based on the defocus amount are repeated for each frame based on the outputs of the focus detection pixel arrays 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 imaging device 22. As described above, 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 to the drive instruction of the focus lens 32 within one frame time. There is. In this respect, in the present embodiment, one specific focus detection pixel row is determined based on the contrast information, and the defocus amount is calculated only for the output of the 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 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 figure for demonstrating the operation example of the conventional camera, and has shown time on the horizontal axis similarly to FIG. In the example shown in FIG. 8, the calculation of the defocus amount which takes a relatively long time is performed for all of the focus detection pixel arrays L1 to L4, so 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, compared to the present embodiment shown in FIG. 7, the required time from the calculation of the defocus amount to the lens drive instruction becomes longer than the time for one frame rate. The lens drive instruction may not be able to be issued for each frame. Specifically, in the example shown in FIG. 8, since it is not possible to perform operations from the calculation of the defocus amount to the lens drive instruction within one frame's worth of time, compared to the time lag T1 of this embodiment shown in FIG. The time lag T2 from the charge accumulation to the drive instruction of the focus lens 32 is twice as large.

  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 focus state of the optical system at time t 11, so the position where the focus lens 32 greatly exceeds the in-focus position In some cases, the camera may be driven, or the ability to follow the subject may be 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, the drive instruction of the focus lens 32 can be issued at time t10 with a small time lag. Compared to the conventional example shown in FIG. 8, the focus lens 32 can be properly driven to the in-focus position.

  As described above, in the first embodiment, the 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 in the focus detection area AFP. Then, based on the detected contrast information, the focus detection pixel row used for focus detection is determined. That is, among the plurality of focus detection pixel rows L1 to L4, the focus detection pixel row corresponding to the subject with the largest contrast, or the focus detection pixel row in which the high frequency component is most included in the pixel output The defocus amount is determined for only the specific focus detection pixel row. This makes it possible to detect the focus state of the optical system with respect to a subject with the largest contrast or a subject with the largest number of high frequency components, and, as in the prior art, for all of the plurality of focus detection pixel arrays L1 to L4. As compared with the case of calculating the focus amount, the time required to calculate the defocus amount can be shortened, and detection of the focus state can be repeatedly performed at appropriate timing.

  Further, in the first embodiment, since 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 plurality of focus detection pixel rows The following effects can be achieved as compared with the case of adding or averaging the outputs of L1 to L4. That is, when the subject has a contrast in the oblique direction of the imaging pixel 221, if the outputs of the plurality of focus detection pixel lines L1 to L4 are added or averaged, the contrast may be reduced rather than the subject. 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 row, even in such a case, a drop in contrast can be prevented, and the subject is appropriately selected. Can be detected.

Second Embodiment
Next, a second embodiment of the present invention will be described. In the second embodiment, the camera 1 shown in FIG. 1 has the same configuration as that of the above-described first embodiment 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 different frequency bands from the outputs of the focus detection pixel arrays L1 to L4. Then, on the basis of the plurality of extracted frequency components, a plurality of contrast information is detected for each of the focus detection pixel arrays L1 to L4. For example, when the camera control unit 21 includes three filters for extracting frequency components in three different frequency bands, the camera control unit 21 detects three contrast information from the output of one focus detection pixel row can do. The frequency band of the frequency component extracted in the second embodiment is not particularly limited, and can be an arbitrary 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 contrast information as specific focus detection pixels. Detect as a column. For example, among the plurality of focus detection pixel rows L1 to L4, the camera control unit 21 selects one or a plurality of focus detection pixel rows whose contrast magnitude of the corresponding subject is equal to or more than a predetermined value. Can be detected. Alternatively, the camera control unit 21 can detect one or a plurality of focus detection pixel rows whose amount of high frequency components included in the output is equal to or more than a predetermined value as a specific focus detection pixel row.

  When the camera control unit 21 determines the specific focus detection pixel row, the number of specific focus detection pixel rows is smaller than the number of focus detection pixel rows L1 to L4 corresponding to the focus detection area AFP. Then, the 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, at least the number of the specific focus detection pixel rows is three or less. Then, the specific focus detection pixel row is determined.

Then, when the camera control unit 21 determines the plurality of focus detection pixel rows as the specific focus detection pixel rows, the outputs of the plurality of specific focus detection pixel rows are added or averaged, and the plurality of specified or summed outputs are averaged. The defocus amount is calculated based on the output of the focus detection pixel column. Here, FIG. 9 excludes the imaging pixel 221 from the imaging surface of the imaging device 22 shown in FIG. 3, and only the first focus detection pixel 222a and the second focus detection pixel 222b that constitute four focus detection pixel rows L1 to L4. Are schematically shown. For example, when adding the outputs of a plurality of specific focus detection pixel rows, the camera control unit 21 outputs the output of the pixel A1 _L1 of the first focus detection pixel row L1 shown in FIG. 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 L3} of the fourth focus detection pixel row L4 And the output of the pixel addition circuit to obtain a pixel addition output _I.sub.A1 . Similarly, the output of the pixel B1 _L2 of the second focus detection pixel row L2 that receives the output of the pixel B1 _L1 of the first focus detection pixel row L1 and the focus detection light flux that passes through the same focusing pupil The output of the pixel B1 _L3 of the three focus detection pixel row L3 and the output of the pixel B1 _L4 of the fourth focus detection pixel row L4 are added to obtain a pixel addition output _IB1 . Hereinafter, similarly, _{A2 L1} and the _{I A2} from the output of _{A2 L2} and _{A2 L3} and _{A2 L4,} the _{I B2} from the output of the _{B2 L1} and _{B2 L2} and _{B2 L3} and _{B2 L4, A3 L1} and _{A3 L2} and A3 the _{I A3} from output of _L3 and _{A3 L4,} obtain _{I B3} from the output of the _{B3 L1} and _{B3 L2} and _{B3 L3} and _{B3 L4.}

Then, the camera control unit 21 uses the obtained pixel addition output to generate a data string based on the first focus detection pixel 222a, that is, the first image data string I _A1 , I _A2 , I _A3,. . . , I _An and a data string based on the second focus detection pixel 222 b, that is, a second image data string I _B1 , I _B2 , I _B3,. . . , I _Bn 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 arrays L1 to L4, the first focus detection pixels 222a and the second focus detection pixels 222b are disposed at positions shifted by 0.5 pixels, respectively. 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 a focus detection pixel row, so the first focus detection pixels 222a and The two image point detection pixels 222b and the two focus detection pixels 222b are offset from each other by 0.5 pixels, and the first image data strings I _A1 , I _A2 , I _A3,. . . , I _An and second image data strings I _B1 , I _B2 , I _B3,. . . , I _Bn have become data mutually shifted by 0.5 pixels. Therefore, when the correlation operation 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) exhibits a local minimum value, it is necessary to use an interpolation operation or the like, and as a result, the focus detection accuracy decreases. There was a case that Such a problem tends to be noticeable particularly 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 have the 0.. As shown in FIG. 10A, when the pixel addition output obtained by adding the pixel outputs is used, the in-focus state (the defocus amount is zero, because it is arranged at a position shifted by 5 pixels. In the state (1), the shift amount at which the correlation amount C (k) gives the local minimum value can be accurately determined, whereby the focus detection accuracy can be appropriately enhanced.

  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, as in step S101 of the first embodiment, the imaging element 22 performs imaging pixels 221 and each of the first focus detection pixels 222a and the second focus detection pixels that constitute the plurality of focus detection pixel arrays L1 to L4. Acquisition of the output data of 222b is performed. In step S202, as in step S102 in the first embodiment, the camera control unit 21 selects a focus detection area AFP to be used for focusing.

  Then, in step S203, the camera control unit 21 detects contrast information. In the second embodiment, the camera control unit 21 performs filter processing on the output of each of the focus detection pixel arrays L1 to L4 using a plurality of filters for extracting frequency components in different frequency bands, thereby each focus detection pixel A plurality of frequency components are extracted from the output of each of the columns L1 to L4. Then, the camera control unit 21 detects information including the amount and the 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 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 of the plurality of focus detection pixel arrays L1 to L4 for which the contrast of the corresponding subject is equal to or greater than a predetermined value. A detection pixel row is determined as a specific focus detection pixel row. Alternatively, based on the plurality of contrast information detected in step S203, the camera control unit 21 selects one or more of the plurality of focus detection pixel arrays L1 to L4 in which the amount of high frequency components included in the output is equal to or more than a predetermined value. The focus detection pixel row of is determined as the 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 a plurality of specific focus detection pixel arrays determined in step S204. For example, when the plurality of focus detection pixel arrays are determined as the specific focus detection pixel arrays, the camera control unit 21 calculates an output of 1 by adding or averaging the outputs of the plurality of specific focus detection pixel arrays. Then, based on this output, it is possible to calculate the defocus amount used for driving the focus lens 32.

  In step S206, as in step S106 of the first embodiment, calculation of the drive amount of the focus lens 32 and drive of the focus lens 32 are performed based on the defocus amount calculated in step S205.

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

  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 a plurality of extracted frequency components are extracted. Based on the detection of a plurality of contrast information. Then, one or more specific focus detection pixel lines are determined from the focus detection pixel lines L1 to L4 based on the plurality of contrast information, and defocusing is performed based on the determined pixel output of the specific focus detection pixel lines. Determine the amount. As described above, in the second embodiment, the defocus amount is not calculated for all the focus detection pixel rows L1 to L4, and the number of specific focus detection pixel rows smaller than the number of the focus detection pixel rows L1 to L4 is described. By calculating the defocus amount, it is possible to shorten the calculation time of the defocus amount, and as a result, it becomes possible to repeatedly detect the focus state at an appropriate timing.

  As mentioned above, although embodiment of this invention was described, embodiment mentioned above is described in order to facilitate an understanding of this invention, and is not described in order to limit this invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

  For example, in the above-described embodiment, a configuration in which four focus detection pixel rows L1 to L4 are provided in one focus detection area AFP is exemplified, 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 two or three, or five or more.

  In the above-described embodiment, the imaging element 22 includes the focus detection pixel arrays L1 to L4, and the defocus amount is calculated based on the outputs of the focus detection pixel arrays L1 to L4. 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 light reception signal received by the phase difference AF detection module. Specifically, the phase difference AF detection module has a plurality of pair of line sensors that receive a light flux passing through the optical system, detects contrast information for each line sensor, and detects the contrast information based on the detected contrast information. Among the plurality of line sensors, a pair of line sensors used for focus detection may be determined. When the pair of line sensors to be used for focus detection is determined, the operation unit of the phase difference detection module may be configured to determine the pair of line sensors to be used for focus detection, or the camera control unit 21 However, a pair of line sensors used for focus detection may be determined by acquiring the output of each pair of line sensors.

  As described above, the “light receiving sensor” in the present invention may be the focus detection pixel rows 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 imaging device 22 or the camera 1 including the same, or may be the phase difference AF detection module or the camera 1 including the same.

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

  Further, as shown in the focus detection pixel rows L1b and L2b in FIG. 13, each focus detection pixel 222a and 222b may be configured to include 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 a light beam emitted from the focusing pupil 351 is a pair. A light flux received by one of the photoelectric conversion units 2222 a and 2222 b and emitted from the distance measuring pupil 352 is received by the other photoelectric conversion unit. Thus, in each of the focus detection pixel arrays L1b and L2b, a pair of image data arrays can be output. In FIG. 13, the photoelectric conversion unit that receives the light flux emitted from the distance measurement pupil 351 is grayed out, and the photoelectric conversion unit that receives the light flux emitted from the distance measurement pupil 352 is white.

  Furthermore, the arrangement of the first focus detection pixels 222a and the second focus detection pixels 222b constituting each focus detection pixel row may be at least those alternately arranged on the same row, for example, as shown in FIG. As in the focus detection pixel rows L1c to L4c shown in FIG. 5, a configuration may be made such that a normal imaging pixel 221 is included in the focus detection pixel row.

  Further, in addition to the embodiment described above, when the contrast of the subject (or the luminance of the subject) is equal to or more than a predetermined value, as shown in the first embodiment, the contrast of the focus detection pixel row L1 to L4 is The focus detection pixel row corresponding to the largest subject, or the focus detection pixel row in which the high frequency component is most included in the output is determined as the specific focus detection pixel row, while the contrast of the subject (or the brightness of the subject) is predetermined. If the value is less than the value, as described in the second embodiment, among the focus detection pixel lines L1 to L4, one or a plurality of focus detection pixel lines whose contrast of the corresponding subject is a predetermined value or more, or One or a plurality of focus detection pixel rows in which the amount of high frequency components included in the output is equal to or more than a predetermined value may be determined as the specific focus detection pixel row.

Reference Signs List 1 digital camera 2 camera body 21 camera control unit 22 imaging element 221 imaging pixel L1 to 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

Claims (9)

An image pickup device having a plurality of regions in which a plurality of pixel groups each including a plurality of pixels that receives light of an object that has passed through an optical system and outputs a signal based on the received light;
The optical system is based on the signals output from a number of pixel groups smaller than the number of the pixel groups arranged in one area selected based on the contrast of the signals output from the pixel group. And a detection unit configured to detect a focus state of the image of the subject formed by a system. In the focus detection device according to claim 1,
The focus detection device, wherein the in-focus state of the image of the subject detected by the detection unit is a defocus amount that is a deviation between the position of the image of the subject and the imaging surface of the imaging device. In the focus detection device according to claim 2,
The detection unit selects one of the pixel groups and calculates the defocus amount based on only the signal output from the selected pixel group. In the focus detection device according to claim 2,
The detection unit selects a plurality of the pixel groups whose number is smaller than the number of the pixel groups arranged in one focus detection area, and either the addition value or the average value of the output signals of the selected pixel group The focus detection apparatus which calculates the said defocusing amount based on. In the focus detection device according to any one of claims 2 to 4,
The focus detection apparatus selects the pixel group for calculating the defocus amount based on contrast information of a plurality of different frequency components of a signal output from the pixel group. In the focus detection device according to any one of claims 1 to 5,
The pixel group includes a plurality of pixels for receiving light passing through a first pupil of the optical system, and a plurality of pixels for receiving light passing through a second pupil of the optical system. In the focus detection device according to any one of claims 1 to 6,
The focus detection apparatus according to claim 1, wherein the detection unit selects the pixel group for calculating a defocus amount from among a plurality of parallel pixel groups arranged in one area.   A camera comprising the focus detection device according to any one of claims 1 to 7.   The electronic device provided with the focus detection apparatus in any one of Claims 1-7.

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