JP5737356B2 - Focus adjustment device and camera - Google Patents

Description

The present invention relates to a focus adjustment device and a camera.

In an imaging device that performs focus detection using a pupil division method using a microlens, the vignetting of the optical system occurs in the focus detection light beam that the photoelectric conversion unit should receive, and the pair of image outputs obtained by pupil division is uneven. May be. If the pair of image outputs are non-uniform, the accuracy of the phase difference calculated by the correlation calculation is lowered, and accurate focus detection becomes difficult.
Therefore, in Patent Document 1, a pair of image outputs when a uniform luminance surface is imaged with the same optical system is prepared in advance as reference data, and the pair of image outputs captured is corrected based on the reference data. An imaging apparatus that detects a focal position using a pair of corrected image outputs has been proposed.

JP 2002-131623 A

  However, because the reference data differs depending on the state of the optical system at the time of shooting due to the influence of the exit pupil position, pupil shape, aberration, and aperture at the time of shooting, and the shape and aberration of the microlens, It is necessary to prepare a plurality of reference data for each state. For example, in the case of an imaging apparatus of a lens exchange type, it is necessary to prepare reference data in advance according to the lens to be attached. In addition, when photographing is performed using a lens that does not have corresponding reference data, there is a problem that it is difficult to perform accurate focus detection.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a focus adjustment device and a camera that improve the accuracy of focus detection without preparing reference data in advance.

[1] In order to solve the above problem, the present invention provides a first focus detection sensor that receives a light beam from the first exit pupil region, and a second focus detection sensor that receives a light beam from the second exit pupil region. Corresponding to a first signal output from the first focus detection sensor and an image sensor having an image sensor provided near the first focus detection sensor and the second focus detection sensor and receiving a light beam from an exit pupil. the first image and the deviation between the third image corresponding to the third signal by the imaging sensor outputs, and a second image corresponding to the second signal, wherein the second focus detection sensor outputs a third image that of the arithmetic unit you calculating the deviation, the before and Ki演 calculated the first image that is calculated by the unit third image and the deviation, the first correction signal using the third signal and the first signal The deviation between the second image and the third image generated and calculated by the calculation unit Using a correction signal generator for generating a second correction signal using the third signal and the second signal, the first correction signal and the second correction signal, defocus calculation for calculating a defocus amount And a focus adjustment device.
[2] The present invention also receives a light beam from the first exit pupil region and outputs a first signal, and receives a light beam from the second exit pupil region and outputs a second signal. An image sensor comprising: a second focus detection sensor; and an image sensor provided in the vicinity of the first focus detection sensor and the second focus detection sensor for receiving a light beam from an exit pupil and outputting a third signal; A calculation unit that calculates a shift between one signal and the third signal and a shift between the second signal and the third signal; and the first signal and the third signal calculated by the calculation unit Deviation, the third signal and the first correction signal obtained using the first signal, the deviation between the second signal and the third signal calculated by the calculation unit, the third signal and the first signal The defocus amount using the second correction signal obtained by using the two signals A focusing device, characterized in that it comprises a defocus calculation unit that calculates.
[ 3 ] Further, the present invention is a camera characterized by including the focus adjustment device described above.

  According to the present invention, it is possible to improve the focus detection system without preparing reference data in advance.

It is a schematic block diagram which shows the structure of the imaging device 201 in the embodiment. It is a figure which shows the example of arrangement | positioning of the focus detection position of the imaging device 201 in the embodiment. FIG. 2 is a schematic diagram illustrating a configuration example of an image sensor 212 in the same embodiment. It is sectional drawing of the example of 1 structure of the image sensor 310 in the embodiment. It is sectional drawing of one structural example of the focus detection sensor 311 in the embodiment. It is a figure which shows the relationship between the imaging sensor 310 in the same embodiment, and an exit pupil. It is a figure which shows the relationship between the focus detection sensor 311 and the exit pupil in the embodiment. It is a figure which shows the light ray distribution in the light beam which the image sensor 310 of the image sensor 212 in the embodiment light-receives. It is a figure which shows the light ray distribution in the light beam which the focus detection sensor 311 of the image pick-up element 212 in the embodiment light-receives. It is a figure which shows the example of an output of the focus detection sensor 311 at the time of imaging the object of uniform brightness | luminance in the same embodiment. It is a figure showing an example of arrangement of image sensor 310 and focus detection sensor 311 in image sensor 212 in the embodiment. 4 is a graph showing spectral sensitivity characteristics of an imaging sensor 310 and a focus detection sensor 311 in the embodiment. 5 is a diagram illustrating an example of a reference signal from the imaging sensor 310 and a pair of first signal and second signal from the focus detection sensor 311 in a state where no vignetting occurs in the embodiment. FIG. It is a figure which shows an example of the reference signal in the state in which the vignetting has generate | occur | produced in the same embodiment, the 1st signal, and the 2nd signal. It is the figure which showed the area | region which calculates the output ratio of the reference signal shown in FIG. 14, and a 1st signal. FIG. 16 is a diagram illustrating an output ratio between the reference signal 1401 and the first signal 1402 illustrated in FIG. 15 and an output ratio between the reference signal 1401 and the second signal 1403; 4 is a flowchart showing focus detection processing of the imaging apparatus 201 in the embodiment. It is a figure which shows arrangement | positioning of the focus detection sensor 311 on the image pick-up element 212 in a modification.

Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic block diagram showing the configuration of the imaging apparatus 201 in the same embodiment. In the present embodiment, the case of an image pickup apparatus with interchangeable lenses will be described. As shown in the figure, an imaging lens 201 has an interchangeable lens 202 attached to a camera body 203 via a mount unit 204.

  The interchangeable lens 202 includes a lens 209, a zooming lens 208, a focusing lens 210, a diaphragm 211, and a lens drive control unit 206. The lens drive control unit 206 drives the zooming lens 208, the focusing lens 210, and the diaphragm 211 in accordance with a lens drive signal transmitted from the camera body 203 via the electrical contact 213 of the mount unit 204. Further, the drive control unit 206 moves the focusing lens 210 to a focal point based on information indicating the driving amount of the focusing lens 210 included in the lens driving signal.

The camera body 203 includes an imaging device 212, a body control unit 214, a display device driving unit 215, a display device 216, an eyepiece lens 217, and an image information memory 218.
The imaging element 212 is arranged on a planned imaging plane on which a light beam from a subject incident through the interchangeable lens 202 is imaged, and performs photoelectric conversion that outputs an electrical signal corresponding to the amount of light of the imaged image. In addition, in the imaging device 212, microlens imaging sensors are arranged in a matrix, and microlens focus detection sensors are arranged in regions corresponding to a plurality of focus detection positions.

The body control unit 214 controls the entire imaging apparatus 201, reads a signal photoelectrically converted from the imaging element 212, calculates a focus adjustment state (defocus amount) of the interchangeable lens 202 based on the read signal, A lens drive signal corresponding to the detected defocus amount is transmitted to the lens drive control unit 206 via the electrical contact 213 of the mount unit 204 to cause the lens drive control unit 206 to perform autofocus control. The lens drive signal includes information indicating a drive amount for moving the focusing lens 210 to a focal point. Further, by moving the focusing lens 210 to the in-focus point, the light flux from the subject incident through the interchangeable lens 202 forms an image on the image sensor 212.
In addition, the body control unit 214 reads out the photoelectrically converted signal from the image sensor 212, outputs image data based on the read signal to the display device driving unit 215, and stores the image data in the image information memory 218.

The body control unit 214 includes an image data generation unit 241, a deviation amount calculation unit 242, a signal correction unit 243, and an AF (Auto Focus) control unit 244.
The image data generation unit 241 generates a reference signal (third signal) from the signal read from the image sensor included in the image sensor 212, and uses the first signal used for focus detection from the signal read from the focus detection sensor included in the image sensor 212, and The second signal is output. Further, the image data generation unit 241 outputs image data based on the signal from the image sensor of the image sensor 212 to the display device drive unit 215 and stores the image data in the image information memory 218.

  The deviation amount calculation unit 242 calculates an image deviation amount s1 (first image deviation amount) indicating a relative deviation amount (phase difference) between the image indicated by the first signal and the image indicated by the reference signal by correlation calculation. . Further, similarly to the first signal, the shift amount calculation unit 242 calculates an image shift amount s2 (second image shift amount) of the second signal, and corrects the second signal using the calculated image shift amount s2. Second misalignment corrected image data is calculated. The calculation of the image displacement amount s1 and the image displacement amount s2 is specifically performed by obtaining the correlation value between the two images while relatively moving the two images in units of pixels, and the movement amount at which the correlation value becomes the highest. Is the amount of deviation. At this time, the shift amount calculation unit 242 does not move the entire image in units of pixels, but divides the image into predetermined regions, calculates a correlation value for each divided region, and reduces the calculation amount.

The signal correction unit 243 uses the image shift amount s1 calculated by the shift amount calculation unit 242, the first signal, and the reference signal to calculate a first correction value that corrects vignetting occurring in the first signal. . Then, the signal correction unit 243 calculates a first correction signal obtained by correcting the first signal with the calculated first correction value.
In addition, the signal correction unit 243 calculates a second correction value that corrects vignetting generated in the second signal, using the image shift amount s2, the second signal, and the reference signal. Then, the signal correction unit 243 corrects the second signal with the calculated second correction value to calculate a second correction value.

  Here, the vignetting is a focal point in this specification based on the position, shape, and lens aberration of the exit pupil of the interchangeable lens 202, the shape of the microlens provided in the image sensor 212, the lens aberration, the projection characteristics, and the like. It means that the amount of light decreases due to vignetting in the light beam received by the photoelectric conversion element of the detection sensor. The vignetting correction is to reduce the influence of the vignetting by correcting the decrease in the signal level output from the photoelectric conversion element by the vignetting by the first correction value and the second correction value and bringing it close to the signal level of the reference signal. It is.

The AF control unit 244 calculates an image shift amount s3 between the image indicated by the first correction signal and the image indicated by the second correction signal, and multiplies the calculated image shift amount s3 by a predetermined coefficient to determine the defocus amount. Is calculated. Further, the AF control unit 244 calculates a lens drive amount based on the calculated defocus amount, and transmits a lens drive signal including information indicating the calculated lens drive amount to the lens drive control unit 206.
Here, the coefficient used when calculating the defocus amount is a value indicating the correlation between the image shift amount s3 and the defocus amount, which are calculated in advance by simulation and actual measurement.

  The display device driving unit 215 displays the image data input from the body control unit 21 on the display device 216 of the electric viewfinder, and outputs a subject image or the like via the eyepiece 217. The photographer visually recognizes the subject displayed on the display device 216 through the eyepiece lens 217.

  FIG. 2 is a diagram illustrating an arrangement example of focus detection positions of the imaging apparatus 201 in the embodiment. As illustrated, the imaging apparatus 201 has five focus detection positions on the shooting screen 300. The imaging apparatus 201 has a focus detection position 301 in the center of the shooting screen 300, focus detection positions 302 and 303 in the upper and lower peripheral portions, and focus detection positions 304 and 305 in the left and right peripheral portions.

FIG. 3 is a schematic diagram illustrating a configuration example of the image sensor 212 in the embodiment. In the imaging element 212, imaging sensors 310 are arranged in a matrix, and focus detection sensors 311 are arranged in rows at the focus detection positions 301 to 305 shown in FIG. The image sensor 310 includes a microlens 10 and a photoelectric conversion element 11. The focus detection sensor 311 includes a microlens 10 and a pair of photoelectric conversion elements 12 and 13.
The imaging sensor 310 corresponds to each pixel of an image captured by the imaging device 201, for example. Note that a value interpolated based on a signal read from a nearby imaging sensor 310 is used for a pixel in which the focus detection sensor 311 is disposed.

FIG. 4 is a cross-sectional view of a configuration example of the image sensor 310 in the embodiment. In the imaging sensor 310, the microlens 10 is disposed in front of the photoelectric conversion element 11 for imaging (subject side).
FIG. 5 is a cross-sectional view of a configuration example of the focus detection sensor 311 in the same embodiment. In the focus detection sensor 311, the microlens 10 is disposed in front of the photoelectric conversion elements 12 and 13 for focus detection.

  FIG. 6 is a diagram illustrating a relationship between the imaging sensor 310 and the exit pupil in the embodiment. An imaging sensor 310 disposed on the optical axis 91 of the interchangeable lens 202 and having the microlens 50 (10) and the photoelectric conversion element 51 (11), and disposed outside the optical axis 91, and disposed on the microlens 60 (10) and the photoelectric sensor. The image sensor 310 having the conversion element 61 (11) will be schematically illustrated and described.

The virtual exit pupil 90 is set at a distance d4 in front of the microlenses (50, 60). This distance d4 is a distance determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion elements 51 and 61 (11), and the like.
The region 94 is a region in which the microlens 50 projects the photoelectric conversion element 51 on the virtual exit pupil 90 in the projection direction 57, and the microlens 60 projects the photoelectric conversion element 61 in the projection direction 67 on the virtual exit pupil 90. This is the area projected above. The projection direction 57 and the direction of the optical axis 91 are the same direction.

  The photoelectric conversion element 51 passes a region 94 on the virtual exit pupil 90 and outputs a signal corresponding to the intensity (light quantity) of the image formed on the microlens 50 by the imaging light flux 71 directed to the microlens 50. Similarly, the photoelectric conversion element 61 outputs a signal corresponding to the intensity of an image formed on the microlens 60 by the imaging light flux 81 that passes through the region 94 on the virtual exit pupil 90 and travels toward the microlens 60. Here, the intensity of the image is the light amount of the light beam incident on the photoelectric conversion element, and the photoelectric conversion elements 51 and 61 increase the level of the output signal as the incident light amount increases.

  The projection direction 67 of each microlens 60 of the image sensor 310 arranged at a position off the optical axis 91 indicates that the region where the photoelectric conversion element 61 of the image sensor 310 is projected onto the virtual exit pupil 90 is photoelectric. It is determined so as to coincide with the region 94 onto which the conversion element 51 is projected.

FIG. 7 is a diagram showing the relationship between the focus detection sensor 311 and the exit pupil in the same embodiment. A focus detection sensor 311 that is arranged on the optical axis 91 of the interchangeable lens 202 and has a microlens 50 (10) and a pair of photoelectric conversion elements 52 and 53 (12, 13), and a microlens that is arranged outside the optical axis 91. A focus detection sensor 311 having 60 (10) and a pair of photoelectric conversion elements 62 and 63 (12, 13) will be schematically illustrated and described. Note that the arrangement direction of the focus detection sensors 311 is the same as the arrangement direction of the pair of photoelectric conversion elements 52, 53, 62, and 63.
The virtual exit pupil 90 is set to a distance d4 in front of the microlenses (50, 60) as in the case of FIG.

The region 92 is a region in which the microlens 50 projects the photoelectric conversion element 52 on the virtual exit pupil 90 in the projection direction 57, and the microlens 60 projects the photoelectric conversion element 62 in the projection direction 67 on the virtual exit pupil 90. This is the area projected above.
The region 93 is a region in which the microlens 50 projects the photoelectric conversion element 53 on the virtual exit pupil 90 in the projection direction 57, and the microlens 60 projects the photoelectric conversion element 63 in the projection direction 67 on the virtual exit pupil 90. This is the area projected above.

The photoelectric conversion element 52 passes a region 92 on the virtual exit pupil 90 and outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 72 toward the microlens 50. The photoelectric conversion element 53 passes a region 93 on the virtual exit pupil 90 and outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 73 toward the microlens 50.
The photoelectric conversion element 62 passes a region 92 on the virtual exit pupil 90 and outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 82 toward the microlens 60. The photoelectric conversion element 63 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 83 that passes through the region 93 on the virtual exit pupil 90 and travels toward the microlens 60.

  In addition, the projection direction 67 of each microlens 60 of the focus detection sensor 311 arranged at a position off the optical axis 91 is that the region where the photoelectric conversion element 62 is projected onto the virtual exit pupil 90 is the photoelectric conversion element 52. And the area where the photoelectric conversion element 62 is projected onto the virtual exit pupil 90 is determined to coincide with the area 93 where the photoelectric conversion element 53 is projected.

  In the image sensor 212, focus detection sensors 311 are arranged in rows at focus detection positions 301 to 305. Then, the image data generation unit 241 reads out signals output by the focus detection sensor 311 receiving and outputting a pair of light beams from different regions (92, 93) on the exit pupil through the microlens, and a pair of signals used for focus detection. Output a signal. Specifically, the image data generation unit 241 includes a first signal obtained by sequentially arranging signals read from the photoelectric conversion elements 12 of the focus detection sensors 311 arranged at any of the focus detection positions 301 to 305, and the photoelectric conversion element 13. And a second signal in which the signals read from are sequentially arranged.

  This first signal indicates the intensity distribution of an image formed by the focus detection light beam passing through the region 92 on the virtual exit pupil 90 on the column of the focus detection sensors 311. The second signal indicates the intensity distribution of an image formed by the focus detection light beam passing through the region 93 on the virtual exit pupil 90 on the column of the focus detection sensors 311.

  FIG. 8 is a diagram showing a light distribution in a light beam received by the image sensor 310 of the image sensor 212 in the embodiment. FIG. 8 shows the relationship between the exit pupil 47 of the optical system on the virtual exit pupil plane and the region 33 on which the photoelectric conversion element 11 of the image sensor 310 is projected. The case where the exit pupil 47 of the optical system coincides with the virtual exit pupil plane will be described. On the imaging sensor 310 located off the optical axis of the optical system, the exit pupil 47 is projected from a circle to an ellipse according to the angle with respect to the optical axis. The region 33 is obtained by projecting the photoelectric conversion element 11 of the image sensor 310 onto a virtual exit pupil plane via the microlens 10.

The distribution of the amount of light in the region 33 is not uniform, and the amount of light decreases from the center toward the periphery due to diffraction and aberration of the microlens 10. In FIG. 8, the amount of light in the region 33 is shown by shading, the amount of light at the center is the largest, and the amount of light decreases toward the periphery.
Note that the positions of the microlens 10 and the photoelectric conversion element 11 are adjusted so that the region 33 on which the photoelectric conversion element 11 of the image sensor 310 is projected and the exit pupil 47 of the optical system substantially coincide.

  FIG. 9 is a diagram illustrating a light distribution in a light beam received by the focus detection sensor 311 of the image sensor 212 in the embodiment. FIG. 9 shows the relationship between the exit pupil 48 of the optical system on the virtual exit pupil plane and the regions 28 and 29 where the photoelectric conversion elements 12 and 13 of the focus detection sensor 311 are projected. In the focus detection sensor 311 located off the optical axis of the optical system, in addition to the exit pupil of the optical system aperture, the exit pupil corresponding to the outer shape of the lens restricts (shields) the light beam incident on the focus detection sensor 311. obtain.

  On the focus detection sensor 311 located off the optical axis of the optical system, the exit pupil 48 is deformed according to the angle with respect to the optical axis, and further deformed and projected by vignetting due to the outer shape of the lens. Further, the projection regions 28 and 29 obtained by projecting the pair of photoelectric conversion elements 12 and 13 onto the virtual exit pupil plane by the microlens do not have a uniform light distribution in the region due to the diffraction and aberration of the microlens, and the center. The amount of light decreases from the edge toward the periphery.

  In FIG. 9, the light amounts in the projection areas 28 and 29 are shown by shading, and the light amount in the central part is the largest and decreases toward the peripheral part. Note that the photoelectric conversion elements 12 and 13 of the focus detection sensor 311 have the positions of the photoelectric conversion elements 12 and 13 and the microlens 10 so that the overlap between the projection areas 28 and 29 and the exit pupil 48 of the optical system becomes large. The position is adjusted. In the focus detection sensor 311, the photoelectric conversion elements 12 and 13 are smaller in area than the photoelectric conversion element 11 of the image sensor 310, and thus are easily affected by vignetting.

  FIG. 10 is a diagram illustrating an output example of the focus detection sensor 311 when a subject with uniform brightness is imaged in the embodiment. The horizontal axis indicates the position of the focus detection sensor, and the vertical axis indicates the output level of the photoelectric conversion element. The output example indicated by reference numeral 1601 indicates the output of the focus detection sensor 311 row when vignetting does not occur. On the other hand, the output example indicated by reference numeral 1602 indicates the output of the focus detection sensor 311 row when vignetting occurs. Here, the output level of the focus detection sensor 311 is directly proportional to the overlapping ratio between the exit pupil 48 shown in FIG. 9 and the regions 28 and 29 where the photoelectric conversion elements are projected on the virtual exit pupil plane, and the light of the optical system. Decreases with distance from the axis.

FIG. 11 is a diagram illustrating an example of the arrangement of the image sensor 310 and the focus detection sensor 311 in the image sensor 212 in the embodiment. R, G, and B respectively indicate the arrangement of the imaging sensor 310 provided with a red filter (R), a green filter (G), and a blue filter (B). In the image sensor 212, an image sensor 310 provided with R, G, and B color filters forms a Bayer array. A shows the arrangement of the focus detection sensors 311.
A line 1007 indicates a row of focus detection sensors 311 for focus detection. Lines 1005 and 1006 indicate columns of the image sensor 310 arranged in the vicinity of the line 1007. Here, the image sensor 310 disposed in the vicinity of the line 1007 is a signal from which a signal serving as a base is read when calculating a reference signal corresponding to the focus detection sensor 311 included in the line 1007. The imaging sensor 310 may be the closest to the corresponding focus detection sensor 311 or may be determined in advance based on the result of simulation or measurement.

  The signals of the image sensors 310 on the lines 1005 and 1006 are the basis of a reference signal (third signal) used for focus detection. In this way, by using the two lines, the line 1005 and the line 1006, the reference signal is generated using the signals of the imaging sensor 310 having the R, G, and B color filters. For example, a reference signal corresponding to the focus detection sensor 311 is added to the focus detection sensor 311 of the line 1007 by adding signals output from the R, G, and B imaging sensors 310 closest to the focus detection sensors 311. Is calculated.

  Although the calculation of the reference signal in the case of the Bayer color filter is shown, the color filter configuration and arrangement are not limited to this. For example, a complementary color filter (G: green, Y: yellow, Mg: magenta, Cy: cyan) may be used. In this case, a combination is determined in advance according to the wavelength detected by the image sensor 310 provided with each color filter, and a reference signal is calculated using the output of the combined image sensor 310.

FIG. 12 is a graph showing the spectral sensitivity characteristics of the image sensor 310 and the focus detection sensor 311 in the embodiment. FIG. 12A shows the spectral sensitivity of the image sensor 310 provided with R, G, and B filters. FIG. 12B shows the spectral sensitivity of the focus detection sensor 311. The focus detection sensor 311 is not provided with a color filter like the image sensor 310 in order to avoid a decrease in the amount of light received, and has a spectral sensitivity that is a combination of the spectral sensitivity characteristics of the image sensor 310.
Note that when the reference signal is generated using the signal output from the image sensor 310, the amount of light reduction by the color filter provided in the image sensor 310 is corrected according to the spectral sensitivity characteristic shown in FIG.

FIG. 13 is a diagram illustrating an example of a reference signal from the imaging sensor 310 and a pair of first signal and second signal from the focus detection sensor 311 in a state where no vignetting occurs in the embodiment.
The image data generation unit 241 outputs a reference signal 1701 based on a signal read from the photoelectric conversion element 11 of the imaging sensor 310 on the lines 1005 and 1006, and based on a signal read from the photoelectric conversion element 12 of the focus detection sensor 311 on the line 1007. The first signal 1702 is output, and the second signal 1703 is output based on the signal read from the photoelectric conversion element 13 of the focus detection sensor 311 on the line 1007.

The first signal 1702 and the second signal 1703 coincide with the reference signal 1701 when focused on the planned imaging plane. The defocus amount in focus detection is represented by the sum of a deviation amount s1 between the reference signal 1701 and the second signal 1703 and a deviation amount s2 between the reference signal 1701 and the first signal 1702.
At this time, the photoelectric conversion element 12 receives a light beam that passes through the projection area 28 (FIG. 9), and the photoelectric conversion element 13 receives a light beam that passes through the projection area 29 (FIG. 9).

  FIG. 14 is a diagram illustrating an example of the reference signal, the first signal, and the second signal in a state where vignetting occurs in the embodiment. The horizontal axis indicates pixels corresponding to the imaging sensor 310 and the focus detection sensor 311, and the vertical axis indicates the output level of the photoelectric conversion element. A graph indicated by reference numeral 1401 is a reference signal, a graph indicated by reference numeral 1402 is a first signal, and a graph indicated by reference numeral 1403 is a second signal. When the first signal 1402 and the second signal 1403 are moved away from the center (optical axis of the optical system), the output level decreases due to the influence of vignetting.

FIG. 15 is a diagram showing a region for calculating the output ratio between the reference signal and the first signal shown in FIG. The deviation amount calculation unit 242 performs a correlation operation between the reference signal 1401 and the first signal 1402 to detect the area A1 of the first signal 1402 having the highest correlation value with respect to the area As of the reference signal 1401 and An image shift amount s1 is calculated.
At this time, the signal correction unit 243 calculates the output average value Es of the reference signal 1401 in the region As and the output average value E1 of the first signal 1402 in the region A1.

  The output average value Es of the reference signal and the output average value E1 of the first signal are calculated by the following equations (1) to (2), respectively. Further, an output ratio V1 that is a ratio of the output average values Es and E1 is expressed by Expression (3).

  Here, As and A1 indicate a set of pixels included in the area detected by the correlation calculation process, j indicates the position of the pixel, and the pixel position j indicates the area As for which the output average value is calculated, Included in A1. ds [i] indicates the output level of the reference signal at the pixel position i, d1 [i] indicates the output level of the first signal at the pixel position i, and n is included in the region detected by the correlation calculation process The number of pixels to be displayed is shown. s1 indicates the amount of deviation between the reference signal and the first signal calculated by the correlation calculation process.

  Further, the deviation amount calculation unit 242 detects a region having a high correlation value and calculates a deviation amount with respect to the second signal by the correlation calculation process with the reference signal, similarly to the first signal. In addition, the signal correction unit 243 calculates the output average values Es and E2 of the reference signal and the second signal based on the region detected by the deviation amount calculation unit 242 between the reference signal and the second signal and the deviation amount. An output ratio V2 that is a ratio of the calculated output average values Es and E2 is calculated.

In FIG. 15, one combination of regions having a high correlation value between the reference signal and the first signal is shown. However, in actual processing, combinations of a plurality of regions are detected and output for each combination of regions. The average value and output ratio are calculated. In addition, a combination of a plurality of areas is also detected in the reference signal and the second signal, and an output average value and an output ratio are calculated for each area combination.
Further, the signal correction unit 243 calculates the output ratio in at least three regions without calculating the output ratio over all the regions of the first signal and the second signal, and uses the calculated output ratio to perform spline interpolation. The output ratio of other regions may be complemented by Lagrange interpolation, least square approximation, or the like.

  FIG. 16 is a diagram illustrating output ratios of the reference signal 1401 and the first signal 1402 illustrated in FIG. 15 and output ratios of the reference signal 1401 and the second signal 1403. The signal correction unit 243 outputs the first distribution correction signal and the second distribution correction signal obtained by correcting the image intensities indicated by the first signal and the second signal using the correction values indicated by the reciprocals of the output ratios V1 and V2. calculate. Specifically, the output level reduced by the vignetting in the focus detection sensor 311 is corrected to the same output level as that of the reference signal by multiplying the correction value.

FIG. 17 is a flowchart showing a focus detection process of the imaging apparatus 201 in the embodiment.
First, focus detection processing is started by supplying power to the imaging apparatus 201 (step S100), and the image data generation unit 241 receives signals of the photoelectric conversion elements 12 and 13 included in the focus detection sensor 311 included in the line 1007. Read and output the first signal and the second signal (step S101), read the signal from the photoelectric conversion element 11 of the image sensor 310 included in the lines 1005 and 1006 (step S102), and calculate a reference signal with less vignetting. (Step S103).

  The deviation amount calculation unit 242 includes a combination of the image deviation amount s1 indicating the deviation between the intensity of the image indicated by the first signal output from the image data generation unit 241 and the intensity of the image indicated by the reference signal, and the regions As and A1. Calculation is performed by correlation calculation processing (step S104). The signal correction unit 243 calculates the output average values Es and E1 and the output ratio V1 using the combinations of the image shift amount s1 and the regions As and A1 calculated by the shift amount calculation unit 242 according to the equations (1) to (3). (Step S105).

The deviation amount calculation unit 242 also includes an image deviation amount s2 indicating a deviation between the intensity of the image indicated by the second signal output from the image data generation unit 241 and the intensity of the image indicated by the reference signal, and the regions As and A2. The combination is calculated by correlation calculation processing (step S106). The signal correction unit 243 uses the combination of the image shift amount s2 and the regions As and A2 calculated by the shift amount calculation unit 242 to calculate the output average values Es and E2 and the output ratio V2 as in the first signal ( Step S107).
The signal correction unit 243 calculates a first correction signal in which the intensity of the image indicated by the first signal is corrected using the calculated output ratio V1, and the intensity of the image indicated by the second signal using the calculated output ratio V2. A second correction signal obtained by correcting the above is calculated.

The AF control unit 244 calculates a deviation amount s3 between the image indicated by the first correction signal and the image indicated by the second correction signal by a known correlation calculation process (step S108), and according to the calculated image deviation amount s3. A defocus amount is calculated (step S109), a lens drive amount of the focusing lens 210 corresponding to the calculated defocus amount is calculated (step S110), and a control signal including the calculated lens drive amount is sent to the lens drive control unit 206. Send to.
The lens drive control unit 206 drives the focusing lens 210 in accordance with the lens drive amount included in the received control signal (step S111), and focuses the subject on the microlens 10 of the image sensor 212.
Thereafter, the imaging apparatus 201 repeats the operations from steps S101 to S111.

  As described above, the imaging apparatus 201 according to the present embodiment calculates the reference signal based on the output of the imaging sensor 310 arranged in the vicinity of the focus detection sensor 311, and uses the reference signal to detect the focus detection sensor 311. The correction value for correcting the first signal and the second signal output from is calculated. Thereby, the signal level of the first signal and the second signal can be reduced without preparing correction data for correcting the decrease in the signal level accompanying the decrease in the light amount due to vignetting (vignetting) by the optical system and the microlens. It can be corrected. Then, by detecting the image shift amount (phase difference) between the first correction signal and the second correction signal in which the influence of vignetting is reduced, the accuracy of calculation of the defocus amount and focus detection can be improved. Further, since the vignetting is corrected by the light flux that has passed through the interchangeable lens 202, the defocus amount can be calculated and the focus can be detected even if an interchangeable lens for which correction data is not prepared in advance is attached to the imaging apparatus 201. This can widen the range of selection of interchangeable lenses.

  Further, the image pickup apparatus 201 corrects the output level to the same output level as the reference signal even when the output level of the photoelectric conversion elements 12 and 13 of the focus detection sensor 311 decreases due to vignetting, so the output level is corrected. A change in signal intensity due to vignetting can be reduced from the first correction signal and the second correction signal, and the calculation accuracy of the image shift amount between the first correction signal and the second correction signal by the correlation calculation can be improved.

  In the imaging apparatus 201, the signal correction unit 243 calculates the output ratios V1 and V2 by using the average value of the outputs, so that the output of the focus detection sensor 311 is localized due to noise or the like. If the output fluctuates, the influence of noise on the correction value can be reduced, and the correction of vignetting for the first signal and the second signal can be stably performed to improve the calculation of the defocus amount and the accuracy of focus detection. be able to.

<Modification of one embodiment>
FIG. 18 is a diagram illustrating an arrangement of the focus detection sensors 311 on the image sensor 212 in a modification of the embodiment. The focus detection sensor 311 is disposed on a line 1101 indicated by reference numeral A1 and a line 1102 indicated by reference numeral A2. The focus detection sensor 311 arranged on the line 1101 detects a light beam that passes through the projection region 28 shown in FIG. On the other hand, the focus detection sensor 311 arranged on the line 1102 detects the light beam passing through the projection region 29 (FIG. 9). In this case, the image data generation unit 241 reads the output of the focus detection sensor 311 included in the line 1101 and outputs the first signal, reads the output of the focus detection sensor 311 included in the line 1102 and outputs the second signal. To do.

  As a result, the focus detection sensor 311 only needs to receive one of the pair of light beams, so there is no need to have two photoelectric conversion elements, and the photoelectric conversion element can be made larger than in the first embodiment. Then, the difference in output level between the first signal and the second signal and the reference signal can be reduced, and errors such as an image shift amount calculated by the shift amount calculation unit 242 can be reduced. As a result, the imaging apparatus 201 can improve the accuracy of defocus amount calculation and focus detection.

  In the above-described embodiment and its modification, the AF control unit 244 calculates a look-up table in which the image shift amount s3 and the defocus amount are associated with each other when calculating the defocus amount in step S109. A defocus amount may be calculated using the lookup table. Further, this lookup table may be provided for each interchangeable lens 202 to be attached. Thereby, the calculation amount of the AF control unit 244 can be reduced, and the time required for focus detection and focusing can be shortened.

  Moreover, in the focus detection process shown in FIG. 17, the order of steps S104 to S105 and steps S106 to S107 may be changed. Moreover, you may make it process the process of step S104-S105 and step S106-S107 in parallel. Thereby, the time required for processing by the deviation amount calculation unit 242 and the signal correction unit 243 can be reduced, and the time required for focus detection and focusing can be reduced.

  The AF control unit 244 may calculate the image shift amount s3 based on the image shift amounts s1 and s2 calculated by the shift amount calculation unit 242 in steps S104 and S106. Since the image shift amount s3 between the first correction signal and the second correction signal is a value close to the sum of the image shift amounts s1 and s2, the correlation calculation is performed on the vicinity of the sum of the image shift amounts s1 and s2. Thus, the time required for the correlation calculation processing can be reduced, and the time required for focus detection and focusing can be reduced.

  In addition, the signal correction unit 243 is configured to calculate the output average value and the output ratio for each region calculated by the deviation amount calculation unit 242, but even if the output average is calculated for each pixel without obtaining the output average value. Good. Thereby, the calculation amount of the signal correction unit 243 can be reduced, and the time required for calculating the defocus amount and detecting the focus can be reduced.

  Further, the signal correction unit 243 is configured to calculate the output ratio between the reference signal and the first signal and the output ratio between the reference signal and the second signal. Approximation may be performed to be symmetric with respect to the axis, and one of the two output ratios may be calculated and used for correction of the first signal and the second signal. Thereby, the time required for the signal correction unit 243 to calculate the output average value and the output ratio can be reduced, and the time required for focus detection and focusing can be reduced.

  The body control unit 214 described above may have a computer system inside. In this case, the focus detection process described above is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing this program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  DESCRIPTION OF SYMBOLS 10, 50, 60 ... Micro lens, 12, 13, 52, 53, 62, 63 ... Photoelectric conversion element, 92, 93 ... Area, 201 ... Imaging device, 212 ... Imaging element, 242 ... Deviation amount calculation part, 243 ... Signal correction unit, 244, AF control unit, 310, imaging sensor, 311, focus detection sensor

Claims (3)

A first focus detection sensor that receives a light beam from the first exit pupil region; a second focus detection sensor that receives a light beam from the second exit pupil region; and the first focus detection sensor and the second focus detection sensor. An imaging device having an imaging sensor provided in the vicinity and receiving a light beam from an exit pupil;
Deviation between the third image corresponding to the third signal, wherein the image sensor and the first image is output corresponding to the first signal by the first focus detection sensor outputs, and the second focus detection sensor outputs a computation unit and a second image corresponding to the second signal you calculating the deviation between the third image,
Wherein the front displacement between the first image computed by Ki演 calculation unit and the third image to generate a first correction signal using the third signal and the first signal, computed by the computing unit A correction signal generating unit configured to generate a second correction signal using a deviation between the second image and the third image, the third signal, and the second signal;
A focus adjustment apparatus comprising: a defocus calculation unit that calculates a defocus amount using the first correction signal and the second correction signal . A first focus detection sensor that receives a light beam from the first exit pupil region and outputs a first signal; a second focus detection sensor that receives a light beam from the second exit pupil region and outputs a second signal; An imaging device having an imaging sensor provided near the first focus detection sensor and the second focus detection sensor and receiving a light beam from an exit pupil and outputting a third signal ;
A calculation unit that calculates a shift between the first signal and the third signal and a shift between the second signal and the third signal;
Deviation between the first signal and the third signal calculated by the calculation unit, the first correction signal obtained using the third signal and the first signal, and the first correction signal calculated by the calculation unit A defocus operation unit that calculates a defocus amount using a deviation between two signals and the third signal, and a second correction signal obtained by using the third signal and the second signal. Focus adjustment device characterized. Camera, characterized in that it comprises a focusing device according to any one of claims 1 or claim 2.

Images