JP2014074851A - Focus detection device and image capturing device - Google Patents

Abstract

A focus detection apparatus capable of appropriately detecting the focus of an optical system is provided.
An image shift signal corresponding to an image plane shift amount by the optical system is obtained from an image signal compressed at a first compression degree, and a plurality of filters excluding a first filter having the highest detectable frequency band. A filter capable of detecting a frequency band suitable for the acquired image shift signal is selected, and the shift amount is detected based on the image shift signal filtered by the selected filter, and the focus state of the optical system. Is determined to be in the vicinity of the in-focus position including the in-focus range, and the filter used when detecting the shift amount is the second filter having the second highest detectable frequency band. An image shift signal corresponding to the image plane shift amount by the optical system can be acquired from an image signal compressed at a second compression level lower than the first compression level or an uncompressed image signal, and can be detected. Frequency Based the frequency is highest first filter filtered image shift signals, the focus detection device and detects the shift amount.
[Selection] Figure 1

Description

  The present invention relates to a focus detection apparatus and an imaging apparatus.

  Conventionally, a focus detection pixel that receives a light beam that has passed through different areas of the imaging optical system is mixed in an image sensor for capturing an image by the photographing optical system, and the output of the focus detection pixel is output. A technique for detecting the focus state of a photographing optical system using the same is known (for example, see Patent Document 1).

JP 2009-75407 A

  However, in the prior art, since the calculation for detecting the focus state is performed using the output from the image sensor, the amount of data used for the calculation increases, and there is a problem that the calculation load is large.

  The problem to be solved by the present invention is to provide a focus detection apparatus capable of appropriately performing focus detection of an optical system.

  The present invention solves the above problems by the following means. In the following description, the reference numerals corresponding to the drawings showing the embodiments of the present invention are used for explanation, but these reference numerals are only for facilitating the understanding of the present invention and are not intended to limit the invention. Absent.

[1] The focus detection apparatus of the present invention captures an image by the optical system (31, 32, 33), generates an image signal corresponding to the captured image, and outputs the generated image signal (22). When,
The imaging unit is configured to generate an image signal compressed at a predetermined first compression degree, an image signal compressed at a second compression degree lower than the first compression degree, or an uncompressed image signal. And an image control unit (21) that controls the image, and based on the image signal output from the image pickup unit, the amount of displacement of the image plane by the optical system is detected using the phase difference, thereby focusing the optical system. A focus detection unit (21) for detecting the state, a determination unit (21) for determining whether the focus state of the optical system is in the vicinity of the in-focus position, and a detectable frequency band having a predetermined frequency band. A filter unit having one filter, a second filter whose detectable frequency band is lower than the first filter, and a third filter whose detectable frequency band is lower than the second filter ( 21) and The focus detection unit obtains an image shift signal corresponding to an image plane shift amount by the optical system from the image signal compressed at the first compression degree, and selects the first filter among the plurality of filters. A filter capable of detecting a frequency band suitable for the acquired image shift signal is selected from a plurality of filters excluding the filter, and the shift amount is detected based on the image shift signal filtered by the selected filter. The filter used when the determination unit determines that the focus state of the optical system is in the vicinity of the in-focus position and the shift amount is detected by the focus detection unit is the second filter. If there is, an image shift signal corresponding to an image plane shift amount by the optical system is acquired from the image signal compressed at the second compression degree or the image signal not compressed, and the image signal is acquired. Among the plurality of filter data section, by selecting the first filter, on the basis of the first filtered image shift signals by the filter, and detects the shift amount.

  [2] The focus detection apparatus of the present invention further includes a focus determination unit (21) that determines whether or not the focus state is in focus, and the focus determination unit is once configured to be the focus detection unit (21). Thus, after the detection of the shift amount is performed using the first filter, the focus determination is performed again by the focus detection unit until the detection of the shift amount is performed using the first filter. It can be configured not to.

  [3] In the focus detection apparatus of the present invention, the imaging control unit (21) adds the outputs of the photoelectric conversion elements provided in the imaging unit (22) or thins out the outputs of the photoelectric conversion elements. Thus, the imaging unit can be configured to generate a compressed image signal.

  [4] An imaging apparatus according to the present invention includes the focus detection apparatus.

  According to the present invention, focus detection of an optical system can be performed appropriately.

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 the arrangement of the focus detection pixels 222a and 222b by enlarging the vicinity of the focus detection pixel row 22a 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 focus detection pixels 222a, and FIG. FIG. 4D is an enlarged front view showing one of the focus detection pixels 222b, FIG. 4D is a cross-sectional view showing one of the imaging pixels 221 in an enlarged manner, and FIG. 4E is one of the focus detection pixels 222a. FIG. 4F is an enlarged sectional view showing one of the focus detection pixels 222b. FIG. 5 is a cross-sectional view taken along the line VV in FIG. FIG. 6 is a flowchart showing the operation of the camera according to the present embodiment.

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

  FIG. 1 is a main part configuration diagram showing a digital camera 1 according to an embodiment of the present invention. A digital camera 1 according to the present embodiment (hereinafter simply referred to as a camera 1) includes 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. Yes.

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

  The lens 32 is a focus lens, and can adjust the focal length of the photographing optical system by moving in the direction of the optical axis L1. 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. Note that the current position information of the focus lens 32 detected by the encoder 35 is sent to the camera control unit 21 to be described later via the lens control unit 37, and the focus lens drive motor 36 calculates the focus calculated based on this information. The driving position of the lens 32 is driven by being sent from the camera control unit 21 via the lens control unit 37.

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

  The lens control unit 37 is electrically connected to the camera control unit 21 by an electric signal contact unit 41 provided on the mount unit 4, and is driven by the focus lens 32 and opened by the diaphragm 34 based on a command from the camera control unit 21. In addition to adjusting the aperture, lens information such as the position of the focus lens 32 and the aperture diameter of the diaphragm 34 is transmitted to the camera control unit 21.

  On the other hand, the camera body 2 is provided with an imaging element 22 that receives the light beam L1 from the photographing optical system on a planned focal plane of the photographing optical system, and a shutter 23 is provided on the front surface thereof. The image sensor 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electrical signal, and sends it to the camera control unit 21. The captured image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder (EVF) 26 of the observation optical system, and a release button ( When (not shown) is fully pressed, the photographed image information is recorded in the camera memory 24 which is a recording medium. The camera memory 24 can be either a removable card type memory or a built-in memory. Details of the structure of the image sensor 22 will be described later.

  The camera body 2 is provided with an observation optical system for observing an image picked up by the image pickup device 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 driving circuit 25 that drives the electronic viewfinder (EVF) 26, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the captured image information captured by the image sensor 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on the read image information. Thereby, the user can observe the current captured image through the eyepiece lens 27. Note that, instead of or in addition to the observation optical system using the optical axis L2, a liquid crystal display may be provided on the back surface of the camera body 2, 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 is electrically connected to the lens control unit 37 through an electric signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and defocuses to the lens control unit 37. Send information such as volume and aperture diameter. The camera control unit 21 reads out the pixel output from the image sensor 22 as described above, generates image information by performing predetermined information processing on the read out pixel output as necessary, and generates the generated image information. Are output to the liquid crystal drive circuit 25 and the camera memory 24 of the electronic viewfinder 26. The camera control unit 21 controls the entire camera 1 such as correction of image information from the image sensor 22 and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 3.

  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 the focus state of the photographic optical system by the contrast detection method based on the pixel data read from the image sensor 22. I do. A specific focus state detection method will be described later.

  The operation unit 28 is an input switch for a photographer to set various operation modes of the camera 1 such as a shutter release button and a moving image shooting start switch. The operation unit 28 switches between an auto focus mode / manual focus mode and an auto focus mode. In particular, the one-shot mode / continuous mode can be switched. 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. The shutter release button includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that is turned on when the button is fully pressed.

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

  FIG. 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 focus detection pixels 222a and 222b by enlarging the vicinity of the focus detection pixel row 22a in FIG.

  As shown in FIG. 3, the imaging element 22 of the present embodiment includes a green pixel G having a color filter in which a plurality of imaging pixels 221 are two-dimensionally arranged on the plane of the imaging surface and transmit a green wavelength region. A red pixel R having a color filter that transmits a red wavelength region and a blue pixel B having a color filter that transmits a blue wavelength region are arranged in a so-called Bayer Arrangement. That is, in four adjacent pixel groups 223 (dense 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 sensor 22 is configured by repeatedly arranging the pixel group 223 on the imaging surface of the image sensor 22 in a two-dimensional manner with the Bayer array pixel group 223 as a unit.

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

  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 on the surface of the semiconductor circuit substrate 2213 of the imaging element 22 as shown in the cross-sectional view of FIG. A photoelectric conversion portion 2212 is built, and a microlens 2211 is formed on the surface thereof. The photoelectric conversion unit 2212 is configured to receive an imaging light beam that passes through an exit pupil (for example, F1.0) of the photographing optical system by the micro lens 2211, and receives the imaging light beam.

  Further, on the imaging surface of the imaging element 22, five focus detection pixel rows 22a to 22e in which focus detection pixels 222a and 222b are arranged instead of the above-described imaging pixel 221 are provided. As shown in FIG. 3, one focus detection pixel column is configured by a plurality of focus detection pixels 222 a and 222 b being alternately arranged adjacent to each other in a horizontal row. In the present embodiment, the focus detection pixels 222a and 222b are densely arranged without providing a gap at the position of the green pixel G and the blue pixel B of the image pickup pixel 221 arranged in the Bayer array.

  Note that the positions of the focus detection pixel rows 22a to 22e shown in FIG. 2 are not limited to the illustrated positions, and may be any one, two, three, or four locations, and more than six locations. It can also be arranged at the position. FIG. 3 shows an example in which the focus detection pixel array is configured by 16 focus detection pixels 222a and 222b, but the number of focus detection pixels configuring the focus detection pixel array is limited to this example. Is not to be done.

  4B is an enlarged front view of one of the focus detection pixels 222a, and FIG. 4E is a cross-sectional view of the focus detection pixel 222a. 4C is an enlarged front view showing one of the focus detection pixels 222b, and FIG. 4F is a cross-sectional view of the focus detection pixel 222b. As shown in FIG. 4B, the focus detection pixel 222a includes a micro lens 2221a and a semicircular photoelectric conversion unit 2222a. As shown in the cross-sectional view of FIG. A photoelectric conversion portion 2222a is formed on the surface of the semiconductor circuit substrate 2213, and a micro lens 2221a is formed on the surface. The focus detection pixel 222b includes a micro lens 2221b and a photoelectric conversion unit 2222b as shown in FIG. 4C, and a semiconductor of the image sensor 22 as shown in the cross-sectional view of FIG. A photoelectric conversion unit 2222b is formed on the surface of the circuit board 2213, and a microlens 2221b is formed on the surface. Then, as shown in FIG. 3, these focus detection pixels 222a and 222b are alternately arranged adjacent to each other in a horizontal row, thereby forming focus detection pixel rows 22a to 22c shown in FIG.

  The photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b have such a shape that the microlenses 2221a and 2221b receive a light beam that passes through a predetermined region (eg, F2.8) of the exit pupil of the photographing optical system. Is done. Further, the focus detection pixels 222a and 222b are not provided with color filters, and their spectral characteristics are the total of the spectral characteristics of a photodiode that performs photoelectric conversion and the spectral characteristics of an infrared cut filter (not shown). ing. However, it may be configured to include one of the same color filters as the imaging pixel 221, for example, a green filter.

  In addition, although the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b illustrated in FIGS. 4B and 4C have a semicircular shape, the shape of the photoelectric conversion units 2222a and 2222b is not limited thereto. Other shapes such as an elliptical shape, a rectangular shape, and a polygonal shape can also be used.

  Here, 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 taken along the line V-V in FIG. 3. It shows that light beams AB1-1, AB2-1, AB1-2, and AB2-2 irradiated from the distance measuring pupils 351 and 352 of the exit pupil 350 are received. In FIG. 5, only the focus detection pixels 222 a and 222 b that are located in the vicinity of the photographing optical axis L <b> 1 are illustrated, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 5 are illustrated. In the same manner, the light beams emitted from the pair of distance measuring pupils 351 and 352 are respectively received.

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

  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 photographic optical systems. Near the planned focal plane. The shapes of the photoelectric conversion units 2222a-1, 2222b-1, 2222a-2, 2222b-2 arranged behind the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 are the same as the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2. Projected onto the exit pupil 350 that is separated from the lenses 2221 a-1, 2221 b-1, 2221 a-2, and 2221 b-2 by a distance measurement distance D, and the projection shape forms distance measurement pupils 351 and 352.

  That is, the microlens and the photoelectric conversion unit in each focus detection pixel so that the projection shapes (distance measurement pupils 351 and 352) of the focus detection pixels coincide on the exit pupil 350 at the distance D. Is determined, and the projection direction of the photoelectric conversion unit in each focus detection pixel is thereby determined.

  As shown in FIG. 5, the photoelectric conversion unit 2222a-1 of the focus detection pixel 222a-1 is formed on the microlens 2221a-1 by a light beam AB1-1 that passes through the distance measuring pupil 351 and goes to the microlens 2221a-1. A signal corresponding to the intensity of the image to be output is output. Similarly, the photoelectric conversion unit 2222a-2 of the focus detection pixel 222a-2 passes through the distance measuring pupil 351, and the intensity of the image formed on the microlens 2221a-2 by the light beam AB1-2 toward the microlens 2221a-2. The signal corresponding to is output.

  Further, the photoelectric conversion unit 2222b-1 of the focus detection pixel 222b-1 passes through the distance measuring pupil 352, and the intensity of the image formed on the microlens 2221b-1 by the light beam AB2-1 directed to the microlens 2221b-1. Output the corresponding signal. Similarly, the photoelectric conversion unit 2222b-2 of the focus detection pixel 222b-2 passes through the distance measuring pupil 352, and the intensity of the image formed on the microlens 2221b-2 by the light beam AB2-2 toward the microlens 2221b-2. The signal corresponding to is output.

  Then, a plurality of the above-described two types of focus detection pixels 222a and 222b are arranged in a straight line as shown in FIG. 3, and the outputs of the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b are used as the distance measurement pupil 351. Of the pair of images formed on the focus detection pixel array by the focus detection light fluxes passing through each of the distance measurement pupil 351 and the distance measurement pupil 352. Data on the distribution is obtained. Next, filter processing is performed on the intensity distribution data of the pair of images to calculate post-filter processing data.

  Here, in the present embodiment, a plurality of detection filters having different detection frequency bands (that is, detectable frequency bands) are controlled by the camera so as to correspond to the spatial frequency of the subject corresponding to the intensity distribution data of the pair of images. Stored in the unit 21. That is, the camera control unit 21 stores a plurality of detection filters having different detection frequency bands so as to correspond to the spatial frequencies of all objects from a low-frequency subject to a high-frequency subject. Three or more detection filters having different detection frequencies are stored. For example, the first filter f1, the second filter f2, the third filter f3, the fourth filter f4, and the fifth filter f5 are arranged in order from the highest detection frequency band. Although it is possible to adopt a mode in which two filters are stored, the present invention is not particularly limited to this.

  In the present embodiment, for the intensity distribution data of the pair of images obtained above, one detection filter is selected from a plurality of detection filters having different detection frequency bands, and the selected detection filter is used. Then, the filtered data is calculated by performing the filtering process. A detection filter selection method will be described later. Then, an image shift detection calculation process (correlation calculation process) is performed on the obtained post-filter data, thereby calculating a defocus amount by a so-called phase difference detection method.

Specifically, the camera control unit 21 reads the first image data strings a ₁ , a ₂ ,... After filtering, which are read out from each focus detection pixel 222a and then obtained by filtering. . . , _An, and the filtered second image data sequence b ₁ , b ₂ ,. . . and b _n, while relatively shifting one-dimensionally, performs correlation calculation of the following formula (1).
C (k) = Σ | a (n + k) −b (n) | (1)
In the above equation (1), the Σ operation indicates a cumulative operation (phase sum operation) for n, and is limited to a range in which data of a (n + k) and b (n) exist according to the image shift amount k. The 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 the calculation result of the above formula (1), the correlation amount C (k) is minimal (the correlation degree is higher as it is smaller) in the shift amount where the correlation between the pair of image data is high.

Next, the camera control unit 21 calculates a minimum value of the correlation amount based on the calculated correlation amount C (k). In the present embodiment, for example, the minimum value C (x) and the minimum value C (x) with respect to the continuous correlation amount are obtained by using the three-point interpolation method shown in the following formulas (2) to (5). The shift amount x that gives is calculated as an image shift amount. Note that C (kj) shown in the following equation is C (k−1) ≧ C (k) and C (k + 1)> C (k) among the correlation amounts C (k) obtained in the above equation (1). ) Satisfying the condition of
D = {C (kj−1) −C (kj + 1)} / 2 (2)
C (x) = C (kj) − | D | (3)
x = kj + D / SLOP (4)
SLOP = MAX {C (kj + 1) -C (kj), C (kj-1) -C (kj)} (5)

Then, the camera control unit 21 calculates the defocus amount df according to the following equation (6) based on the shift amount x from which the minimum value C (x) of the correlation amount is obtained. In the above equation (6), k is a conversion coefficient (k factor) for converting the shift amount x from which the minimum value C (x) of the correlation amount is obtained into the defocus amount.
df = x · k (6)

  Further, the camera control unit 21 reads the output of the imaging pixel 221 of the imaging element 22 and calculates a focus evaluation value based on the read pixel output. This focus evaluation value can be obtained by, for example, extracting a high frequency component of an image output from the imaging pixel 221 of the imaging element 22 using a high frequency transmission filter and integrating the extracted high frequency component. 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) to obtain a focus evaluation value at each position, and the focus evaluation value is maximum. The focus detection by the contrast detection method is performed in which the position of the focus lens 32 is determined as the in-focus position. Note that this in-focus position is obtained when, for example, when the focus evaluation value is calculated while driving the focus lens 32, the focus evaluation value rises twice and then moves down twice. Can be obtained by performing an operation such as interpolation using the focus evaluation value.

  Next, an example of the operation of the camera 1 in the present embodiment will be described along the flowchart shown in FIG. The following operation is started when the camera 1 is turned on.

First, in step S1, generation of a through image by the camera control unit 21 and display of a through image by the electronic viewfinder 26 of the observation optical system are started. Specifically, the camera control unit 21 transmits a signal for causing the image sensor 22 to perform an exposure operation, whereby the exposure operation of the image sensor 22 is executed. At this time, the camera control unit 21 thins out a part of the pixel data of the plurality of imaging pixels 221 and the pixel data of the plurality of focus detection pixels 222a and 222b shown in FIG. Commands the camera control unit 21 to transmit. That is, the image sensor 22 thins out and reads out only pixel data of some of the pixel data of the plurality of imaging pixels 221 and the plurality of focus detection pixels 222a and 222b shown in FIG. , Pixel data partially thinned is output. For example, the focus detection pixels 222a and 222b will be described as an example. In FIG. 3, 16 focus detection pixels 222a and 222b are arranged alternately. Only pixel data from a total of eight focus detection pixels 222 a and 222 b can be output to the camera control unit 21. In this case, the image pickup pixel 221 can also be thinned out every two pixels in the vertical direction.
Alternatively, in step S1, the camera control unit 21 transmits the pixel data of the plurality of imaging pixels 221 and the pixel data of all the pixels of the plurality of focus detection pixels 222a and 222b illustrated in FIG. 3 to the camera control unit 21. The camera control unit 21 may acquire pixel data of all pixels, and the camera control unit 21 may thin out only the pixel data of some pixels.

  Then, the camera control unit 21 generates a through image based on the read data, and the generated through image is sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder 26 of the observation optical system. As a result, the user can view the moving image of the subject through the eyepiece lens 27. Note that such pixel data generation / output, through image generation, and through image display are repeatedly executed at predetermined intervals.

In step S2, the camera control unit 21 starts defocus amount detection processing by the phase difference detection method. In the present embodiment, the defocus amount detection processing by the phase difference detection method is performed as follows. That is, first, the camera control unit 21 uses a pair of image data (a pair of image data) corresponding to a pair of images from the pixel data of the focus detection pixels 222a and 222b constituting the five focus detection pixel rows 22a to 22d of the image sensor 22. Data on the intensity distribution of the image). At this time, as described above, since the pixel data output from the image sensor 21 is thinned out at a predetermined rate, the thinned pixel data is used.
Alternatively, in step S1, the camera control unit 21 acquires pixel data of all pixels, and the camera control unit 21 thins out only some pixel data. The unit 21 generates a pair of image data using the thinned pixel data.

  Then, the camera control unit 21 generates the generated pair of detection filters other than the detection filter having the highest detection frequency band among the plurality of detection filters having different detection frequency bands stored in the camera control unit 21. The detection filter suitable for the image data is selected. Here, as an example, the camera control unit 21 has a first filter f1, a second filter f2, a third filter f3, and a fourth filter in order from the highest detection frequency band as a plurality of detection filters having different detection frequency bands. The case where five filters of f4 and fifth filter f5 are stored will be described as an example. From the second to fifth filters f2 to f5 excluding the first filter f1 which is the detection filter having the highest detection frequency band. Then, a process of selecting a detection filter suitable for the generated pair of image data is performed. In the following, the case where the first to fifth filters f1 to f5 are provided will be described as an example.

  Moreover, as a method of selecting a detection filter suitable for the generated pair of image data from the second to fifth filters f2 to f5, for example, a method of selecting according to the frequency component included in the generated pair of image data Etc. That is, in this method, for example, as the frequency band of the frequency component included in the generated pair of image data is higher, a detection filter having a higher detection frequency band is selected. On the other hand, the frequency included in the generated pair of image data The detection filter with the lower detection frequency band is selected as the frequency band of the component is lower.

  Next, the camera control unit 21 performs a filtering process on the generated pair of image data using the detection filter selected from the second to fifth filters f2 to f5, and performs image processing based on the filtered data. A deviation detection calculation process (correlation calculation process) is executed. Specifically, the camera control unit 21 calculates the defocus amount by calculating the image shift amount according to the above-described method based on the filtered data, and further converting the image shift amount into the defocus amount. To do.

  Such defocus amount detection processing using a detection filter other than the first filter f1 is repeatedly executed at predetermined intervals.

  In step S3, the camera control unit 21 determines whether or not the shutter release button provided in the operation unit 28 is half-pressed (the first switch SW1 is turned on). If the first switch SW1 is turned on, the process proceeds to step S6. On the other hand, if the first switch SW1 is not turned on, step S5 is repeated until the first switch SW1 is turned on. In other words, until the first switch SW1 is turned on, the through image generation / display and the defocus amount detection processing by the phase difference detection method are repeatedly executed.

  In step S4, the camera control unit 21 determines whether or not the defocus amount has been calculated by the defocus amount detection process using the phase difference detection method. If the defocus amount can be calculated, it is determined that distance measurement is possible, and the process proceeds to step S5. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is impossible, and the process proceeds to step S13. In step S13, if it is determined that a predetermined time t has elapsed since the first switch SW1 was turned on, the process proceeds to step S16, the in-focus process is performed, and the predetermined time t has elapsed. If not, the process returns to step S4. In the present embodiment, even when the defocus amount can be calculated, if the reliability of the calculated defocus amount is low, it is treated that the defocus amount cannot be calculated, and the process proceeds to step S13. Let's go ahead. In the present embodiment, for example, when the subject has a low contrast, the subject is an ultra-low brightness subject, or the subject is an ultra-high brightness subject, it is determined that the reliability of the defocus amount is low. . Further, as the out-of-focus processing performed in step S16, for example, a display indicating out-of-focus is displayed on the electronic viewfinder 26 and the focus lens 32 is driven to a predetermined position. Is done.

  In step S5, a process of starting driving the focus lens 33 is performed based on the defocus amount calculated by the defocus amount detection process using the phase difference detection method. Specifically, the camera control unit 21 calculates and calculates the lens driving amount necessary to drive the focus lens 33 to the in-focus position from the defocus amount calculated by the phase difference detection method. The lens driving amount is sent to the lens driving motor 36 via the lens control unit 36. Then, the lens driving motor 36 drives the focus lens 33 to the in-focus position based on the lens driving amount calculated by the camera control unit 21. In the present embodiment, the camera control unit 21 repeatedly calculates the defocus amount by the phase difference detection method even while the lens driving motor 36 is driven and the focus lens 33 is driven to the in-focus position. As a result, when a new defocus amount is calculated as a result, the camera control unit 21 drives the focus lens 33 based on the new defocus amount.

In step S6, the camera control unit 21 based on the defocus amount calculated by the process of detecting the defocus amount by the phase difference detection method, the focus state of the optical system, a predetermined first within the focusing range D _alpha A determination is made whether or not there is. Focus state of the optical system, when it is determined that in the first focusing range D _alpha, the process proceeds to step S7. On the other hand, the focus state of the optical system, when it is determined not in the first focusing range D _alpha, the process proceeds to step S14. In step S14, if it is determined that a predetermined time t has elapsed since the first switch SW1 was turned on, the process proceeds to step S16, the in-focus process is performed, and the predetermined time t has elapsed. If not, the process returns to step S6. Incidentally, the first focusing range D _alpha, focus position near containing focusing range, for example, it can be two times the depth of field or depth of focus.

Next, in step S7, the defocus amount detection process performed immediately before by the phase difference detection method is performed as a detection filter using the second filter f2 (that is, among the plurality of detection filters stored in the camera control unit 21). It is determined whether or not the detection is performed using a detection filter having the second highest detection frequency band. When the detection process of the defocus amount by the phase difference detection method is performed using the second filter f2 as the detection filter, the process proceeds to step S8. On the other hand, a defocus by the phase difference detection method using a detection filter other than the second filter f2, that is, the third to fifth filters f3 to f5 (that is, a detection filter having a detection frequency band lower than that of the second filter f2). If the amount detection process is performed, the process proceeds to step 12. In step S12, it is determined that the subject is in focus, and focus lock (processing for prohibiting driving of the focus lens 32) is performed. In this case, the electronic viewfinder 26 may be configured to perform in-focus display. Further, when the detection filter other than the second filter f2, that is, the third to fifth filters f3 to f5, is used to detect the defocus amount by the phase difference detection method, the focus state of the optical system but than the first focusing range D _alpha, after a third within the focusing range D _gamma is a narrower range may be configured as perform focus lock. Here, the third in-focus range D _γ can be set to, for example, a depth of field or a depth of focus or less (a range of depth of field or less than 1 time of the depth of focus).

  In the present embodiment, when it is determined in step S7 that the defocus amount detection processing by the phase difference detection method performed immediately before is performed using the second filter f2 as a detection filter. Therefore, it is considered that there is a high possibility that the main subject for which the defocus amount is to be detected is a subject having a high frequency component with a high spatial frequency. Therefore, in this embodiment, in such a case, as described below, the defocus amount is detected by the phase difference detection method using the first filter f1 that is the detection filter having the highest detection frequency band. Process.

  That is, first, in step S8, the camera control unit 21 sends the pixel data of the plurality of imaging pixels 221 and the pixel data of all the pixels of the plurality of focus detection pixels 222a and 222b shown in FIG. Commands the control unit 21 to transmit. That is, in step S8, the camera control unit 21 thins out part of the pixel data of the plurality of imaging pixels 221 and the pixel data of the plurality of focus detection pixels 222a and 222b illustrated in FIG. In contrast to outputting pixel data, it instructs to output pixel data of all pixels. In step S8 and subsequent steps, the process of generating and outputting the pixel data of all the pixels is repeatedly executed at predetermined intervals together with the generation of the through image and the display of the through image.

  Next, the process proceeds to step S9. In step S9, the camera control unit 21 causes the first filter f1 (that is, the detection filter having the highest detection frequency band among the plurality of detection filters stored in the camera control unit 21). Detection processing of the used defocus amount is started. That is, in step S9, the defocus amount detection process using the detection filter other than the first filter f1 is terminated, and the defocus amount detection process using the first filter f1 is started. The detection process of the defocus amount using the first filter f1 uses a detection filter other than the first filter f1 except that the first filter f1 is used instead of the second to fifth filters f2 to f5. This is performed in the same manner as the defocus amount detection process. At this time, as described above, since the pixel data output from the image sensor 21 is pixel data of all the pixels that are not thinned out, the plurality of focus detection pixels 222a and 222b shown in FIG. When generating a pair of image data corresponding to a pair of images from the pixel data, all pixel data not thinned out are used as the pixel data of the focus detection pixels 222a and 222b. After step S9, the defocus amount detection process using the first filter f1 is repeatedly executed at predetermined intervals.

Next, in step S10, the focus state of the optical system is set to a predetermined second focusing range based on the defocus amount calculated by the defocus amount detection process using the first filter f1 by the camera control unit 21. A determination is made whether it is within _Dβ . Focus state of the optical system, when it is determined that the second within the focusing range D _beta, the process proceeds to step S7. On the other hand, the focus state of the optical system, when it is determined not within the second focusing range D _beta, the process proceeds to step S15. In step S15, if it is determined that a predetermined time t has elapsed since the first switch SW1 was turned on, the process proceeds to step S16, the in-focus process is performed, and the predetermined time t has elapsed. If not, the process returns to step S10. Note that the second focus range _Dβ can be set to, for example, a range equal to or less than the depth of field or the depth of focus (a range equal to or less than one time the depth of field or the depth of focus).

  Next, in step S11, the camera control unit 21 determines whether or not the defocus amount detection process using the first filter f1 has been executed twice or more. If the defocus amount detection process using the first filter f1 has been executed twice or more, the process proceeds to step S12. In step S12, it is determined that the in-focus state is achieved, and the focus lock is performed. On the other hand, if the defocus amount detection process using the first filter f1 has been performed only once, the process returns to step S10. In other words, in the present embodiment, when the main subject to be detected for the defocus amount is a subject having a high frequency component with a high spatial frequency, the defocus amount detection process using the first filter f1 is performed. It can be expected that the detection accuracy of the defocus amount is improved. Therefore, in the present embodiment, when the defocus amount detection process using the first filter f1 is performed only once, the focus lens 32 is driven based on the result of the detection process, and again, After performing the defocus amount detection process using the first filter f1 (that is, step S11 = Yes), it is determined that the in-focus state is achieved.

  As described above, the camera 1 according to this embodiment operates.

  In the present embodiment, when performing the defocus amount detection process by the phase difference detection method, pixel data partially thinned out of the pixel data of the plurality of focus detection pixels 222a and 222b shown in FIG. To generate a pair of image data, and when filtering the pair of image data using a detection filter, a detection filter other than the first filter f1, which is a detection filter having the highest detection frequency band, that is, The second to fifth filters f2 to f5 are used (see steps S1 and S2 described above). According to the present embodiment, when performing the defocus amount detection process by the phase difference detection method, a part of the pixel data of the plurality of focus detection pixels 222a and 222b shown in FIG. 3 is thinned out. Therefore, the calculation load required for the defocus amount detection processing by the phase difference detection method can be reduced, and further, the first filter f1 that is the detection filter having the highest detection frequency band is not used. Accordingly, it is possible to effectively prevent a high frequency component such as a noise component from being erroneously detected. In particular, when detecting a low-frequency subject having a relatively low spatial frequency, even if pixel data obtained by thinning out a part of the pixel data of the focus detection pixels 222a and 222b can be detected satisfactorily, Even when pixel data with thinned portions is used, the focus state can be detected with high accuracy.

In addition, in the present embodiment, when the detection process other than the first filter f1 is used to detect the defocus amount by the phase difference detection method, the focus state of the optical system is the first focus range. When the second filter f2 is used as a detection filter within D _α (see Steps S6 and S7 described above), the main subject for which the defocus amount is to be detected is the space. Since there is a high possibility that the subject is a high-frequency subject having a high frequency, all the pixel data not thinned out are used as the pixel data of the focus detection pixels 222a and 222b, and the detection filter having the highest detection frequency band is used as the detection filter. A defocus amount detection process is performed by a phase difference detection method using a certain first filter f1 (see steps S8 and S9 described above). According to the present embodiment, by using all pixel data that has not been thinned out as pixel data of the focus detection pixels 222a and 222b, a pair of image data corresponding to a high-frequency subject having a relatively high spatial frequency is obtained. High-frequency subjects can be detected satisfactorily because the filter processing is performed using a detection filter suitable for high-frequency subjects, and even in this case, the focus state can be detected with high accuracy. Can do.

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

For example, in the above-described embodiment, when the detection process other than the first filter f1 is used to detect the defocus amount by the phase difference detection method, every two focus detection pixels 222a and 222b are detected. Although an example has been shown in which pixel data is thinned out and pixel data thinned out every second number is used (see step S1 above), for example, pixel data is thinned out every fourth piece and thinned out every fourth piece. It is also possible to use such pixel data. Further, in such a case, when performing the defocus amount detection process by the phase difference detection method using the first filter f1, the pixel data is not thinned out for the focus detection pixels 222a and 222b. Although an example using pixel data that has not been thinned out has been shown (see step S8 above), for example, every second pixel data is thinned, and every second thinned pixel data is used. It can be.
In this case, the same applies to the case where the camera control unit 21 acquires the pixel data of all the pixels and the camera control unit 21 thins out only some of the pixel data. The thinning number can be changed.

In the above-described embodiment, pixel data is thinned out for the focus detection pixels 222a and 222b when the detection filter other than the first filter f1 is used to perform the defocus amount detection process by the phase difference detection method. Although an example of performing is shown (see step S1 above), the pixel data may be compressed by performing a process of adding the pixel data instead of thinning out the pixel data. In this case, in the defocus amount detection processing by the phase difference detection method using the first filter f1, pixel data that has not been subjected to addition processing may be used, or the first filter f1 may be used. Compared with the case where the detection filter other than the filter f1 is used to detect the defocus amount by the phase difference detection method, the pixel data subjected to the addition processing in a mode in which the addition degree is low (compression degree is low) is used. It can be set as such an aspect.
Even in this case, the camera control unit 21 transmits the pixel data of the plurality of imaging pixels 221 and the pixel data of all the pixels of the plurality of focus detection pixels 222a and 222b illustrated in FIG. 3 to the camera control unit 21. The camera control unit 21 can acquire the pixel data of all the pixels, and the camera control unit 21 can add the pixel data.

  Further, in the above-described embodiment, when performing detection processing of the defocus amount by the phase difference detection method using the detection filter other than the first filter f1, the pixel data of the focus detection pixels 222a and 222b is converted into a pair of images. A corresponding pair of image data (data relating to the intensity distribution of the pair of images) is generated, a detection filter suitable for the generated image data is selected from the second to fifth filters f2 to f5, and the selected detection filter is selected. Although an example in which filter processing is performed on a pair of image data using only the image data is illustrated, for example, the following aspect may be adopted. That is, for example, the generated image data is filtered using each of the second to fifth filters f2 to f5, four pieces of filtered data are calculated, and the calculated four pieces of filtered data are calculated. Then, four defocus amounts are calculated by performing image shift detection calculation processing (correlation calculation processing). Then, a detection filter having a detection frequency band suitable for the corresponding subject is selected from the second to fifth filters f2 to f5 based on the calculation result in the correlation calculation processing, and the detection filter is used. The defocus amount may be determined as the final defocus amount.

In the embodiment described above, the camera control unit 21 stores the first to fifth filters f1 to f5, and these detection filters are used to detect the defocus amount by the phase difference detection method. In this embodiment, in addition to the first to fifth filters f1 to f5, a sixth filter f6 having a detection frequency band lower than the first filter f1 and higher than the second filter f2 is further provided. It is good also as a simple structure. In this case, first, detection processing of the defocus amount by the phase difference detection method is performed using the detection filters excluding the first filter f1 and the sixth filter f6, that is, the second to fifth filters f2 to f5. performed, the focus state of the optical system is a first in-focus range D _alpha, and, as a detection filter, when made using the second filter f2, the first filter f1 and the sixth filter f6 Any one of them may be used to perform a defocus amount detection process using a phase difference detection method. In this case, the second to fifth filters f2 to f5 are used when performing the defocus amount detection process by the phase difference detection method using either the first filter f1 or the sixth filter f6. Similarly to the case, a mode in which a detection filter suitable for the generated pair of image data is selected from the first filter f1 and the sixth filter f6 may be used.

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Camera body 21 ... Camera control part 22 ... Imaging device 221 ... Imaging pixel 222a, 222b ... Focus detection pixel 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control part

Claims (4)

An imaging unit that captures an image by the optical system, generates an image signal corresponding to the captured image, and outputs the generated image signal;
The imaging unit is configured to generate an image signal compressed at a predetermined first compression degree, an image signal compressed at a second compression degree lower than the first compression degree, or an uncompressed image signal. An imaging control unit for controlling
A focus detection unit that detects a focus state of the optical system by detecting a shift amount of an image plane by the optical system using a phase difference based on an image signal output by the imaging unit;
A determination unit that determines whether or not a focus state of the optical system is in the vicinity of a focus position;
A first filter whose detectable frequency band is a predetermined frequency band, a second filter whose detectable frequency band is lower than the first filter, and a frequency whose detectable frequency band is lower than the second filter A filter unit having a third filter which is
The focus detection unit acquires an image shift signal corresponding to an image plane shift amount by the optical system from an image signal compressed at the first compression degree, and removes the first filter from the plurality of filters. Select a filter capable of detecting a frequency band suitable for the acquired image shift signal from a plurality of filters, detect the shift amount based on the image shift signal filtered by the selected filter,
The filter used when the determination unit determines that the focus state of the optical system is in the vicinity of the in-focus position and the shift amount is detected by the focus detection unit is the second filter. In this case, an image shift signal corresponding to an image plane shift amount by the optical system is acquired from an image signal compressed at the second compression degree or an image signal not compressed, and the filter unit A focus detection apparatus, wherein the first filter is selected from among a plurality of filters, and the shift amount is detected based on an image shift signal filtered by the first filter. The focus detection apparatus according to claim 1,
It further has a focus determination unit that determines whether or not it is in focus,
The focus determination unit is configured to detect the shift amount by the focus detection unit again after the detection of the shift amount is performed by the focus detection unit using the first filter. A focus detection apparatus that does not perform focus determination until it is performed using a filter. The focus detection apparatus according to claim 1 or 2,
The imaging control unit causes the imaging unit to generate a compressed image signal by a process of adding the outputs of the photoelectric conversion elements provided in the imaging unit or a process of thinning out the outputs of the photoelectric conversion elements. A focus detection apparatus.   The imaging device provided with the focus detection apparatus in any one of Claims 1-3.

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