JP2012128101A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus using a phase difference distance measuring method, capable of consistently achieving highly accurate distance measurement, with a compact size and a small release time lag.SOLUTION: An imaging apparatus comprises: an imaging device which outputs a first subject image signal, and second and third subject image signals which are respectively photo-electrically converted from a second subject image and a third subject image formed by a pupil division method; a correlation calculation part which calculates a distance between the two images based on the second and the third subject image signals outputted from the imaging device identical to the imaging device to output the first subject image signal; a recognition part which recognizes the best image surface position, a correction value storage part which stores a correction value of the distance between the two images based on the information of the recognition result by the recognition part and the calculation result by the correlation calculation part; an imaging signal acquisition part which acquires the first subject image signal as an imaging signal; and an image construction part which creates image data based on the acquired imaging signal.

Description

  The present invention relates to an imaging apparatus.

In general, the distance measurement accuracy of phase difference autofocus (hereinafter referred to as “AF” as appropriate) is determined by the center of gravity Fno that can be captured by the AF sensor and the interval between focus detection pixels.
As an imaging apparatus using an element in which imaging pixels and focus detection pixels of a conventional example are two-dimensionally arranged, a configuration disclosed in Patent Document 1 below is known.

Patent No. 3592147

Conventional imaging apparatuses mainly have the following two distance measuring methods.
(1) Contrast method (2) Phase difference method The contrast method (1) employs a so-called hill-climbing method in which the contrast value is evaluated while changing the focusing state and performing wobbling. For this reason, the focusing time is long.

In the phase difference method (2), in principle, the defocus amount can be detected by one distance measurement. For this reason, the focusing time is short.
The phase difference method has an advantage of being compact and having a small release time lag.

In an imaging apparatus that employs a phase difference method, when exchanging lenses, if lens data is known and can be acquired, a correction value at the time of phase difference AF can be calculated. On the other hand, when data cannot be acquired from the lens itself, a correction value for phase difference AF cannot be calculated.
Therefore, it is desired that the phase difference AF can be performed with higher accuracy without impairing the advantages of the above-described compact and small release time lag.

  The present invention has been made in view of the above, and is an imaging apparatus that employs a phase difference ranging method, which is compact, has a small release time lag, and can always perform highly accurate focusing. The purpose is to provide.

In order to solve the above-described problems and achieve the object, the imaging apparatus of the present invention includes:
The first subject image signal formed by the light beam from the imaging optical system and the second light beam formed by dividing the pupil among the light beam from the imaging optical system, having a plurality of pixels arranged two-dimensionally. An image sensor that photoelectrically converts each of the subject image and the third subject image, and outputs a second subject image signal and a third subject image signal;
A correlation calculation unit that calculates an interval between two images based on a second subject image signal and a third subject image signal output from the same image sensor as the image sensor that outputs the first subject image signal;
A recognition unit that recognizes the best image plane position;
A correction value storage unit that stores a two-image interval as a correction value based on the recognition result information of the recognition unit and the calculation result of the correlation calculation unit;
An imaging signal acquisition unit that acquires a first subject image signal as an imaging signal;
An image constructing unit that generates image data based on the acquired imaging signal;
Have

  Further, according to a preferred aspect of the present invention, the recognition unit compares the distance measurement result by the contrast method and the distance measurement result by the phase difference method based on the signal from the same pixel of the image sensor to determine the best image plane position. It is desirable to recognize that.

  According to a preferred aspect of the present invention, it is desirable that the correction value storage unit stores the result of the correlation calculation unit when the recognition unit recognizes the best image plane position as a correction value.

  Further, according to a preferred aspect of the present invention, the correction value storage unit corrects the correction value when the distance to the subject corresponding to the first subject image signal is estimated to be infinite based on the calculation result of the correlation calculation unit. It is desirable to store separately the correction value when the distance is estimated to be the closest end and the correction value when the distance is estimated to be neither infinity nor the close end.

  According to the present invention, it is possible to provide an imaging apparatus that employs a phase difference ranging method, is compact, has a small release time lag, and can always perform highly accurate focusing.

It is a figure which shows the internal structure of the digital camera which concerns on embodiment of this invention. It is a figure which shows the structure of the exit pupil of the digital camera which concerns on this embodiment. It is a figure which shows the structure of the photoelectric conversion part of the image pick-up element in this embodiment. It is sectional drawing which shows the structure of two adjacent pixels of the image pick-up element in this embodiment. It is a figure which shows the internal structure of the image pick-up element in this embodiment. It is a figure which shows the internal structure of the image pick-up element in this embodiment. It is a top view which shows the structure (variation 1) of an image pick-up element. It is a top view which shows the structure (variation 2) of an image pick-up element. It is a top view which shows the structure (variation 3) of an image pick-up element. It is a top view which shows the structure (variation 4) of an image pick-up element. It is a functional block diagram which shows the structure of the digital camera which concerns on this embodiment. It is another functional block diagram which shows the structure of the digital camera which concerns on this embodiment. It is a figure explaining an element curve. It is a flowchart which shows the procedure which calculates a correction value. It is another flowchart which shows the procedure which calculates a correction value. It is another flowchart which shows the procedure which calculates a correction value.

  Hereinafter, embodiments of an imaging apparatus according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the following embodiment.

(Digital camera)
First, a camera including an imaging device according to an embodiment of the present invention will be described.
FIG. 1 is a diagram showing an internal configuration of a digital camera 11 according to an embodiment of the present invention.
The digital camera 11 includes an interchangeable lens 12 and a camera body 13, and the interchangeable lens 12 is attached to the camera body 13 by a mount unit 14.

The interchangeable lens 12 includes a lens control unit 30, a lens driving unit 16, a diaphragm driving unit 15, a zooming lens 18, a lens 19, a focusing lens 20, and a diaphragm 21. The lens control unit 30 includes peripheral components such as a microcomputer and a memory. The lens control unit 30 controls driving of the focusing lens 20 and the aperture 21, detects the state of the aperture 21, the zooming lens 18 and the focusing lens 20, and the body control unit 24. Lens information and camera information are received.
In addition to the lens state, specification values relating to the lens data itself are stored in the lens data storage unit 32.

  The aperture driving unit 15 controls the aperture diameter of the aperture 21 via the lens control unit 30 based on the signal from the body control unit 24. Further, the lens driving unit 16 drives the zooming lens 18 and the focusing lens 20 via the lens control unit 30 based on the signal from the body control unit 24.

  The camera body 13 includes an image sensor 22, a body control unit 24, a liquid crystal display element drive circuit 25, a liquid crystal display element 26, an eyepiece lens 27, a memory card 29, and the like. Pixels to be described later are arrayed two-dimensionally on the image sensor 22, and the subject image formed by the interchangeable lens 12 is captured by being arranged on the planned image formation surface of the interchangeable lens 12. Focus detection pixels (hereinafter referred to as “AF pixels” where appropriate) are arranged at predetermined focus detection positions of the image sensor 22.

  Here, the interchangeable lens 12 corresponds to an imaging optical system, and the imaging element 22 corresponds to an imaging element.

  The body control unit 24 includes peripheral components such as a microcomputer and a memory, and reads out an image signal from the image sensor 22, corrects the image signal, and detects the focus adjustment state of the interchangeable lens 12 via the image sensor drive circuit 28. In addition, it receives lens information from the lens control unit 30, transmits camera information (defocus amount), and controls the operation of the entire digital camera. The body control unit 24 and the lens control unit 30 communicate via the electrical contact unit 23 of the mount unit 14 to exchange various information.

  The liquid crystal display element driving circuit 25 drives the liquid crystal display element 26 of the liquid crystal viewfinder. The photographer observes an image displayed on the liquid crystal display element 26 through the eyepiece lens 27. The memory card 29 is removable from the camera body 13 and is a portable storage medium for storing and storing image signals.

  The subject image formed on the image sensor 22 through the interchangeable lens 12 is photoelectrically converted by the image sensor 22, and the output is sent to the body controller 24. The body control unit 24 calculates the lens drive amount based on the defocus amount at a predetermined focus detection position based on the output data (first image signal, second image signal) of the AF pixels on the image sensor 22. The lens driving amount is sent to the lens driving unit 16 via the lens control unit 30. The body control unit 24 stores the image signal generated based on the output of the image sensor 22 in the memory card 29 and sends the image signal to the liquid crystal display element driving circuit 25 to display the image on the liquid crystal display element 26. .

  The camera body 13 is provided with operation members (not shown) (shutter buttons, focus detection position setting members, etc.), and the body control unit 24 detects operation state signals from these operation members, and according to the detection results. The following operations (imaging operation, focus detection position setting operation, image processing operation) are controlled.

  The lens control unit 30 changes the lens information according to the focusing state, zooming state, aperture setting state, aperture opening F value, and the like. Specifically, the lens control unit 30 monitors the positions of the lens 18 and the focusing lens 20 and the aperture position of the aperture 21 and calculates lens information according to the monitor information, or a lookup table prepared in advance. For example, lens information corresponding to the monitor information is selected from the lens data storage unit 32. The lens control unit 30 drives the focusing lens 20 to a focal point by a driving source such as a motor (not shown) based on the received lens driving amount.

(Configuration of image sensor)
As for the configuration of the digital camera 11 described above, the configuration using the same reference numerals is common to all the following embodiments. Next, the configuration of the imaging element 22 of the imaging device included in the digital camera 11 will be described.

2A to 2E are diagrams illustrating the configuration of the exit pupil of the imaging apparatus according to the embodiment of the present invention. As shown in FIGS. 2A to 2E, the exit pupil P in the digital still camera 11 has focus detection pixels corresponding to at least two types of pupil regions of left, right, upper and lower.
Specific examples are as follows (1) to (5).

(1) The exit pupil P is vertically divided into two, and the left pupil detection pixel L and the right pupil detection pixel R are arranged (FIG. 2A).
(2) The exit pupil P is horizontally divided into two, and the upper pupil detection pixel U and the lower pupil detection pixel D are arranged (FIG. 2B)
(3) The left pupil detection pixel L and the right pupil detection pixel R are arranged on the left and right, and a part of them is overlapped (FIG. 2C).
(4) Upper pupil detection pixel U and lower pupil detection pixel D are arranged one above the other and partially overlapped (FIG. 2D)
(5) The left pupil detection pixel L and the lower pupil detection pixel D are arranged at arbitrary positions and a part thereof is overlapped (FIG. 2 (e)).

The shape of the distance measuring pupil is a semicircular shape or an elliptical shape. However, the shape is not limited to this, and other shapes such as a rectangular shape or a polygonal shape may be used.
2 (a) and 2 (b) may be combined to arrange the vertical and horizontal focus detection pixels, or FIG. 2 (c) and 2 (d) may be combined to arrange the vertical and horizontal focus detection pixels. Further, the focus detection pixels for detecting left and right and diagonal lines may be arranged by combining FIGS. 2C and 2E, but the present invention is not limited to this.

In the imaging apparatus according to the present embodiment, the first image signal obtained from the output of the photoelectric conversion unit that receives a light beam having a different pupil area and transmitted through one of the regions, and the light beam transmitted through the other region. The phase difference is detected based on the second image signal obtained from the output of the photoelectric conversion unit that receives the light, and the focus state of the photographing lens is detected.
A specific example of exit pupil division will be described below with reference to FIGS.

(Division of photoelectric conversion part)
First, an example in which the exit pupil is divided by dividing the photoelectric conversion unit of the image sensor 22 will be described with reference to FIG.
FIG. 3 is a diagram illustrating a configuration of the photoelectric conversion unit of the image sensor 22.
The imaging device 22 transfers the photocharges accumulated in the n-type regions 32α and 32β and the n-type regions 32α and 32β that generate and accumulate photocharges together with the p-type well 31 and the p-type well 31 formed in the substrate. Floating diffusion portion (not shown) (hereinafter referred to as “FD portion”), a surface p + layer that collects photocharges in order to efficiently transfer the photocharges accumulated in the n-type regions 32α and 32β to the FD portion. 33α, 33β, a transfer gate (not shown) for transferring photoelectric charges to the FD portion, a SiO ₂ film 34 as a gate insulating film, a Bayer array color filter 35, and a microlens 36 for collecting light from a subject, Is provided.

  The microlens 36 is formed in a shape and position so that the pupil of the interchangeable lens 12 (FIG. 1) and the surface p + layers 33α and 33β are substantially conjugate. Photoelectric charges are typically generated in the region 37.

  In the example shown in FIG. 3, the photoelectric conversion unit is divided into an n-type region 32α and a surface p + layer 33α, and an n-type region 32β and a surface p + layer 33β, thereby dividing the exit pupil. Light rays L31 and L32 enter the n-type region 32α and the surface p + layer 33α, and the n-type region 32β and the surface p + layer 33β, respectively.

(Eccentric opening)
Next, an example in which the exit pupil is divided by decentering the opening of the pixel of the image sensor 22 with respect to the center of the photoelectric conversion element will be described with reference to FIG.
FIG. 4 is a cross-sectional view showing the structure of two adjacent pixels of the image sensor 22.

  The pixel 41 has a microlens 42, a smooth layer 43 for forming a plane for forming the microlens 42, a light shielding film 44 for preventing color mixture of color pixels, and a color filter layer in order from the top. A smoothing layer 45 for flattening the surface and a photoelectric conversion element 46 are arranged. Similarly to the pixel 41, the pixel 51 also includes a micro lens 52, a smooth layer 53, a light shielding film 54, a smooth layer 55, and a photoelectric conversion element 56 in order from the top.

  Further, in these pixels 41 and 51, the light shielding films 44 and 54 have openings 48 and 58 that are eccentric to the outside from the central portions 47 and 57 of the photoelectric conversion elements 46 and 56, respectively.

  In the example shown in FIG. 4, the opening of the pixel of the image sensor 22 is decentered with respect to the center of the photoelectric conversion element. For this reason, since the light rays L41 and L51 are incident on the photoelectric conversion elements 46 and 56, respectively, the exit pupil is divided.

Next, an example in which the exit pupil is divided by decentering the lens will be described with reference to FIG. FIG. 5 is a diagram illustrating an internal configuration of the image sensor.
In the image sensor of FIG. 5, on-chip lenses 61, 62, 63, and 64 on each pixel are configured independently.
In FIG. 5, the optical axes 61a and 63a of the on-chip lenses 61 and 63 of the pixels in the pixel set A are shifted to the left from the center of the pixels. Further, the optical axes 62a and 64a of the on-chip lenses 62 and 64 of the pixels in the pixel set B are shifted to the right from the center of the pixels.
By comparing the outputs from the two pixel sets A and B, the focus amount of the lens 18 can be calculated.

  In the on-chip lenses 61, 62, 63, and 64, two parameters such as the refractive power and the shapes of the optical axes 61a, 62a, 63a, and 64a can be controlled independently. If the number of pixels is sufficiently large, the pixel set A and the pixel set B can obtain the same light intensity distribution, and the phase difference AF can be performed using this. At this time, since the defocus amount in the entire screen can be detected, the three-dimensional information of the subject can be acquired.

  In the example shown in FIG. 5, the on-chip lens of the image sensor 22 is decentered with respect to the center of the pixel. For this reason, the light rays L61 and L62 are incident on the on-chip lenses 61 and 62, respectively, thereby dividing the exit pupil.

Next, an example of dividing the exit pupil using DML (digital microlens) will be described with reference to FIG. FIG. 6 is a cross-sectional view showing the internal structure of the image sensor.
In the imaging device shown in FIG. 6, the on-chip lens is configured by DML. The pixel 70 and the pixel 80 are adjacent pixels that receive light beams from different regions.

  In FIG. 6, the imaging device includes DMLs 71 and 81, a color filter 72, an aluminum wiring 73, a signal transmission unit 74, a planarization layer 75, light receiving elements 76 and 86 (for example, Si photodiodes), and a Si substrate 77. As shown in FIG. 6, the aluminum wiring 73, the signal transmission unit 74, the smoothing layer 75, the light receiving elements 76 and 86, and the Si substrate 77 constitute a semiconductor integrated circuit 78. Here, the configurations of the pixel 70 and the pixel 80 are the same except for the DMLs 71 and 81.

  FIG. 6 shows a state of light beams incident on the light receiving elements 76 and 86, respectively, out of the entire incident light beam. By using the DMLs 71 and 81, the light beams L71 and L81 enter the light receiving element 76 of the pixel 70 and the light receiving element 86 of the pixel 80, respectively, and the exit pupil is divided.

  As an imaging device (imager), for example, a CCD (charge coupled device), a CMOS (Complementary Metal Oxide Semiconductor), a back-illuminated CMOS, a sensor that can capture all three colors of R, G, and B in one pixel. (Forveon X3) can be used.

  In the following embodiments, the focus detection pixel receives a light beam transmitted through a different position of the pupil of the photographing lens by decentering an on-chip lens formed on the photographing lens side of the photoelectric conversion unit from the center of the pixel. It is configured as follows. As described above, pupil division means uses a light shielding member for the center of the pixel to decenter the opening, uses DML, or provides two photoelectric conversion units in one pixel. But you can.

The focus detection pixels are configured to receive light beams transmitted through different positions of the pupil of the photographing lens. For this reason, the signal level from the focus detection pixel may be different from the signal level output from the imaging pixel in the vicinity of the focus detection pixel. In order to obtain an image signal at the position of the focus detection pixel, it is preferable to adopt the following method (1) or (2).
(1) The gain is adjusted so that the signal of the focus detection pixel is equivalent to the signal level of the surrounding imaging pixels, and the signal is used as the image signal at the position of the focus detection pixel.
(2) Pixel interpolation is performed based on the signal of the focus detection pixel and the signal of the imaging pixel in the vicinity of the focus detection pixel to obtain an image signal at the position of the focus detection pixel.

The gain adjustment method is performed as follows.
First, the signal level output from the focus detection pixel is compared with the signal level output from the imaging pixel in the vicinity of the focus detection pixel. Subsequently, the gain is adjusted so that the signal level output from the focus detection pixel approaches the signal level output from a nearby imaging pixel. Thereafter, demosaicing is performed by using the signal obtained by adjusting the gain of the focus detection pixel signal as an image signal to obtain a final image.

The pixel interpolation method is preferably any one of the following (a) to (c), but is not limited to these, and is not limited to simple average calculation (including weighting), but also linear interpolation, quadratic or higher order polynomials It may be obtained by interpolation or median processing.
(A) The signal at the position of the focus detection pixel is interpolated based on the signal of the imaging pixel in the vicinity of the focus detection pixel, and the signal obtained by the interpolation is used as the image signal at the position of the focus detection pixel. Perform mosaicing to get the final image.
(B) The signal at the position of the focus detection pixel is interpolated based on the signal of the focus detection pixel and the signal of the imaging pixel in the vicinity of the focus detection pixel, and the signal obtained by the interpolation is used for focus detection. Demosaicing is performed as an image signal at the pixel position to obtain a final image.
(C) Interpolate the signal at the position of the focus detection pixel based on the signal of the imaging pixel near the focus detection pixel, and based on the signal obtained by the interpolation and the signal of the position of the focus detection pixel Then, the signal obtained by the interpolation is demosaiced as an image signal at the position of the focus detection pixel to obtain a final image.

A plurality of color filters are respectively disposed in the plurality of pixels of the image sensor. In Examples 3 and 4 to be described later, the transmission characteristics of the plurality of color filters are R (red), G (green), and B (blue).
The B filter is a color filter having the transmission characteristic on the shortest wavelength side among the transmission characteristics having different R, G, and B, and the R filter is a color filter having the transmission characteristic on the longest wavelength side. Has other transmission characteristics.
The plurality of color filters may include other combinations as long as they include at least a part of the visible region and have at least three different transmission characteristics.

The focus detection pixel uses the G filter as a color filter that weights the luminance signal most among the plurality of color filters, and restricts the incident direction of the incident light beam.
Note that the focus detection pixel is not limited to the G filter, and at least a part of the color filter that weights the luminance signal most among the plurality of color filters or the pixel in which the color filter having the highest transmittance is arranged. The incident direction of the incident light beam can be limited.

(Pixel array variation 1)
FIG. 7 is a plan view conceptually showing a pixel arrangement in the imager of the first embodiment.
The imager (imaging device) illustrated in FIG. 7 has the pixel center illustrated in FIGS. 3, 4, 5, and 6 with the center of each pixel and the center of the pupil or the area center of gravity of each photoelectric conversion region in the upward direction and the downward direction. It is composed of a combination of pixels shifted in the direction, right direction, and left direction.

FIG. 7 shows a photoelectric conversion region as desired from the optical axis direction of each pixel.
FIG. 7 shows an example of 10 pixels in the vertical direction (L01 to L10) and 10 pixels in the horizontal direction (F01 to F10), for a total of 100 pixels. However, the number of pixels is not limited to this. For example, the total number of pixels may exceed 10 million pixels.

  In the example shown in FIG. 7, there are four types of directions in which the area center of the photoelectric conversion region is shifted with respect to the pixel center: right side, left side, upper side, and lower side. In the following description, they are referred to as a right pixel 120R, a left pixel 120L, an upper pixel 120U, and a lower pixel 120D, respectively.

In FIG. 7, in the row L01, the left pixel 120L, the imaging pixel 121, the left pixel 120L, and the imaging pixel 121 are repeatedly arranged in order from the left (from F01).
In the row L02, the imaging pixel 121, the upper pixel 120U, the imaging pixel 121, and the lower pixel 120D are repeatedly arranged in order from the left.
In the row L03, the right pixel 120R, the imaging pixel 121, the right pixel 120R, and the imaging pixel 121 are repeatedly arranged in order from the left.
In the row L04, the imaging pixel 121, the upper pixel 120U, the imaging pixel 121, and the lower pixel 120D are repeatedly arranged in order from the left.
The rows after L05 are arranged to repeat the patterns of L01, L02, L03, and L04.

The arrangement in FIG. 7 is viewed as follows from the columns F01 to F10.
In the column F01, the left pixel 120L, the shooting pixel 121, the right pixel 120R, and the shooting pixel 121 are repeatedly arranged in order from the top (from L01).
In the column F02, the imaging pixel 121, the upper pixel 120U, the imaging pixel 121, and the upper pixel 120U are repeatedly arranged in order from the top.
The columns after F03 are arranged to repeat the patterns F01 and F02.

  In the following description, row numbers L01 to L10 and column numbers F01 to F10 are shown side by side when a specific pixel is shown. For example, the pixel corresponding to the column F01 in the L01 row is represented by “L01F01”.

  In the example illustrated in FIG. 7, for example, one of L01F01 (left pixel 120L), L02F02 (upper pixel 120U), L03F01 (right pixel 120R), and L02F04 (lower pixel 120D) is calculated from the pixel pitch. The distance between the centers of the pupils or the distance between the centers of gravity is smaller than the distance between the pixels.

  In the imaging apparatus according to the first embodiment, the phase difference is determined from the output signals (signals for ranging) of the cell group including the left pixel 120L and another cell group including the right pixel 120R. Information can be calculated to adjust the focus of the optical system.

  For example, the output waveform obtained from L01F01, L01F03, L01F05, L01F07, and L01F09, which are the left pixels 120L in the L01 row, and the output obtained from L03F01, L03F03, L03F05, L03F07, and L03F09 that are the right pixels 120R in the L03 row By comparing the waveforms with each other, defocus information and in-focus position information can be acquired by a so-called phase difference detection formula.

(Pixel array variation 2)
Next, another configuration example of the imaging element included in the imaging device will be described.

  In the arrangement of FIG. 8, the L05F01 pixel and the L05F05 pixel are left pupil detection pixels. The L05F03 pixel is a right pupil detection pixel.

  Thereby, focus detection with high accuracy can be performed.

(Pixel array variation 3)
Next, another configuration example of the imaging element included in the imaging device will be described.

  The arrangement of the color filters in FIG. 9 repeats these combination patterns in the horizontal direction, with the L01F01 pixel as the green filter G and the L01F02 pixel as the red filter R.

Further, the L02F01 pixel is a blue filter B and the L02F02 pixel is a green filter G, and these combination patterns are repeated in the horizontal direction.
Then, the pattern of the L01 column and the pattern of the L02 column are repeated in the vertical direction.

  Here, the L05F01 pixel and the L05F09 pixel in which the green filter G is disposed are the left pupil detection pixels. The L05F05 pixel is a right pupil detection pixel.

  This makes it possible to perform focus detection with high accuracy regardless of the color of the subject. Note that the combination of the color filter and the photoelectric conversion region in the direction of deviation from the pixel center is not limited to this.

(Pixel array variation 4)
Next, still another configuration example of the imaging element included in the imaging device will be described.

  The arrangement of the color filters in FIG. 10 repeats these combination patterns in the horizontal direction, with the L01F01 pixel as the green filter G and the L01F02 pixel as the red filter R.

Further, the L02F01 pixel is a blue filter B and the L02F02 pixel is a green filter G, and these combination patterns are repeated in the horizontal direction.
Then, the pattern of the L01 column and the pattern of the L02 column are repeated in the vertical direction.

Here, the L01F01 pixel, the L01F09 pixel, the L09F01 pixel, and the L09F09 pixel in which the green filter G is arranged are left pupil detection pixels.
The L05F01 pixel and the L05F09 pixel are right pupil detection pixels.
The L01F05 pixel and the L09F05 pixel are upper pupil detection pixels.
Further, the L05F05 pixel is a lower pupil detection pixel.

  This makes it possible to perform focus detection with high accuracy regardless of the color of the subject. Note that the combination of the color filter and the photoelectric conversion region in the direction of deviation from the pixel center is not limited to this.

(Description of functional block)
In the present embodiment, the recognition unit 138 (FIGS. 11 and 12) recognizes the best image plane position, as will be described later. Regarding this recognition, there are the following two procedures (a) and (b).
(A) The photographer recognizes the best image plane position, that is, the most focused state using the manual focus (hereinafter referred to as “MF” as appropriate) mode.
(B) The best image plane position is recognized using the contrast AF method.

  FIG. 11 is a diagram illustrating functional blocks of the body control unit 24 of the imaging apparatus 11 that recognizes the best image plane using the MF mode when the interchangeable lens 12 is an AF non-AF lens that does not support AF. In addition, the same reference number is attached | subjected to the structure same as the structure shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  From the image sensor 22, a signal for identifying which signal is a signal from the imaging pixel, a signal from the focus detection pixel, the first image signal, or the second image signal passes through the line a. To the A / D converter 131.

  From the image sensor 22, a signal for identifying which signal is a signal from the imaging pixel, a signal from the focus detection pixel, the first image signal, or the second image signal is an A / D converter. Input to 131.

  The image signal acquisition unit (imaging signal acquisition unit) 133 acquires a signal that has passed through the A / D signal processing unit 131 and the signal processing unit 132. A signal from the imaging pixel is output to the liquid crystal display element driving circuit 25 by the display image forming unit 135. The liquid crystal display element (display unit) 26 displays an image for photographing. The photographer can observe an image for photographing through the eyepiece lens 27.

The recorded image configuration unit 134 configures recorded image data based on signals from the imaging pixels. The recorded image data is stored in the memory card 29.
The recorded image configuration unit 134 and the display image configuration unit 135 correspond to an image configuration unit that generates image data based on the acquired imaging signal.

  A signal from the focus detection pixel is output from the image signal acquisition unit 133 to the correlation calculation unit 136.

  The imaging element 22 has a plurality of pixels arranged two-dimensionally, and includes a first subject image signal formed by light beams from lenses 18, 19, and 20 that are imaging optical systems, and an imaging optical system. Of the luminous flux, the second subject image and the third subject image formed by pupil division are photoelectrically converted, and the second subject image signal and the third subject image signal are output. Details will be described later.

  The correlation calculation unit 136 performs a correlation calculation based on the first image signal and the second image signal. That is, the correlation calculation unit 136 determines the interval between the two images based on the second subject image signal and the third subject image signal output from the same image sensor 22 that outputs the first subject image signal. Is calculated.

  Further, the correction value storage unit 137 stores the two-image interval as a correction value based on the recognition result information of the recognition unit 138 and the calculation result of the correlation calculation unit 137.

  The correction value storage unit 137 stores the two-image interval as a correction value based on the recognition result information of the recognition unit 138 and the calculation result of the correlation calculation unit 137.

Here, the correction value storage unit 137 stores the result of the correlation calculation unit 137 when the recognition unit 138 recognizes the best image plane position as a correction value.
As a result, the result of the phase difference AF can be corrected and matched with the result of focusing in the manual focus mode.

  FIG. 12 is a diagram illustrating functional blocks of the body control unit 24 of the imaging apparatus 11 that recognizes the best image plane using the contrast AF mode when the interchangeable lens 12 is an AF lens that supports AF. In addition, the same reference number is attached | subjected to the structure same as the structure shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  From the image sensor 22, a signal for identifying which signal is a signal from the imaging pixel, a signal from the focus detection pixel, the first image signal, or the second image signal passes through the line a. To the A / D converter 131.

  From the image sensor 22, a signal for identifying which signal is a signal from the imaging pixel, a signal from the focus detection pixel, the first image signal, or the second image signal is an A / D converter. Input to 131.

  The image signal acquisition unit (imaging signal acquisition unit) 133 acquires a signal that has passed through the A / D signal processing unit 131 and the signal processing unit 132. A signal from the imaging pixel is output to the liquid crystal display element driving circuit 25 by the display image forming unit 135. The liquid crystal display element (display unit) 26 displays an image for photographing. The photographer can observe an image for photographing through the eyepiece lens 27.

The recorded image configuration unit 134 configures recorded image data based on signals from the imaging pixels. The recorded image data is stored in the memory card 29.
The recorded image configuration unit 134 and the display image configuration unit 135 correspond to an image configuration unit that generates image data based on the acquired imaging signal.

  A signal from the focus detection pixel is output from the image signal acquisition unit 133 to the correlation calculation unit 136.

  The imaging element 22 has a plurality of pixels arranged two-dimensionally, and includes a first subject image signal formed by light beams from lenses 18, 19, and 20 that are imaging optical systems, and an imaging optical system. Of the luminous flux, the second subject image and the third subject image formed by pupil division are photoelectrically converted, and the second subject image signal and the third subject image signal are output.

  The correlation calculation unit 136 performs a correlation calculation based on the first image signal and the second image signal. That is, the correlation calculation unit 136 determines the interval between the two images based on the second subject image signal and the third subject image signal output from the same image sensor 22 that outputs the first subject image signal. Is calculated.

  Further, the correction value storage unit 137 stores the two-image interval as a correction value based on the recognition result information of the recognition unit 138 and the calculation result of the correlation calculation unit 137.

Here, focusing is performed so that the best image plane position is obtained in the contrast AF mode.
The contrast AF control unit 141 controls the focus lens driving unit 16 and the aperture control unit 15 via the control unit 140. The contrast method employs a so-called hill-climbing method in which the contrast value is evaluated while changing the focusing state. Thereby, the state where the contrast of the captured image is the highest is detected.
In this state, the recognition unit 138 recognizes that it is the best image plane position.
The correction value storage unit 137 stores the two-image interval as a correction value based on the recognition result information of the recognition unit 138 and the calculation result of the correlation calculation unit 137.

  The recognizing unit 138 compares the distance measurement result by the contrast AF method and the distance measurement result by the phase difference AF method based on the signal from the same pixel of the image sensor 22, and recognizes the best image plane position. .

The correction value storage unit 137 estimates a two-image interval at a position that is deviated by a predetermined distance from the best image plane position, and a correlation calculation result at a position that deviates from the predetermined distance, the estimated two-image interval, and a predetermined distance. The correction value is calculated based on the above and stored as a correction value.
As a result, the result of the phase difference AF can be corrected and matched with the result of focusing in the contrast AF mode.

  Next, the content of correction using correction values will be described. FIGS. 13A, 13B, and 13C show the proportional relationship between the defocus amount (horizontal axis) and the interval between two images (vertical axis) (hereinafter referred to as “defocus element curve” as appropriate). FIG.

FIG. 13A shows a case where the defocus element is known for the conventional phase difference AF.
A two-image interval (EL) is calculated by correlation calculation. For example, the interval between two images is a predetermined distance a. Further, a defocus amount b corresponding to the interval between two images is obtained.
Based on this defocus amount, a lens drive amount is calculated to drive the lens.

Here, the intercept of the defocus element curve obtained from the correlation calculation does not pass 0 (zero). Therefore, correction is performed so that the intercept passes through 0 (zero) using the correction value.
In general, this correction value is not obtained by calculation at the time of photographing, but is stored as data.

FIG. 13B shows a case where the defocus element is unknown in the conventional configuration.
Since the defocus element curve is unknown, the slope and intercept are unknown. The slope and intercept cannot be calculated from the one-point correlation calculation result. That is, the correction value cannot be calculated.
A straight line indicated by a one-dot chain line and a two-dot chain line is shown as a reference for an unknown defocus element curve.

FIG. 13C shows a case where the defocus element is unknown in this embodiment.
Since the defocus element curve is unknown, the slope and intercept are unknown. As described above, the slope and the intercept cannot be calculated from the one-point correlation calculation result. That is, the correction value cannot be calculated.
In the present embodiment, the recognition unit 138 can define the defocus amount 0 (zero) by recognizing the best image plane position. The best image plane is recognized using the MF mode and the contrast AF mode as shown in the two functional block diagrams described above.
The intercept can be calculated from the correlation calculation result at the position of the defocus amount 0 (zero). That is, the correction value β can be calculated.

If the intercept can be calculated, the two-image interval EL at the best image plane position is always 0 (zero) even if the inclination of the defocus element curve is unknown.
A straight line indicated by a one-dot chain line and a two-dot chain line is shown as a reference for an unknown defocus element curve.

Next, the focusing correction operation in the present embodiment will be described in more detail using a flowchart.
FIG. 14 is a flowchart showing a rough flow of correction value calculation. In step S101, correction value calculation is started. In step S102, it is determined whether the photographer is in the manual focus mode or the contrast AF mode.

In the manual focus mode, the correction value calculation subroutine 1 is executed in step S103.
On the other hand, in the contrast AF mode, the correction value calculation subroutine 2 is executed in step S104.

  In step S <b> 202, the image signal acquisition unit 133 reads out two subject image signals (two image signals) from the pixels of the imaging element 22 that are divided into pupils.

In step S203, the correlation calculation unit 136 performs a correlation calculation of the two image signals. In step S204, the interval between the two images is calculated as a result of the correlation calculation.
In step S205, the correction value storage unit 137 stores the interval between two images as a correction value.

  FIG. 16 is a flowchart showing the procedure of the correction value calculation subroutine 2. In step S <b> 301, the image signal acquisition unit 133 reads the first subject image signal from the pixels of the image sensor 22 that are not pupil-divided.

  In step S302, contrast AF is executed, and the contrast AF control unit 141 (FIG. 12) calculates the peak value (maximum value) of the contrast AF evaluation value. In step S303, the recognition unit 138 recognizes the best image plane position (just focus position).

  In step S <b> 304, the image signal acquisition unit 133 reads out two subject image signals (two image signals) from the pixels of the imaging element 22 that are divided into pupils.

In step S305, the correlation calculation unit 136 performs a correlation calculation of the two image signals. In step S306, the interval between the two images is calculated as a result of the correlation calculation.
In step S307, the correction value storage unit 137 stores the interval between two images as a correction value.

  The pixel readout may be configured to perform all pixel readout and thinning readout processing. The image configuration includes interpolation processing of defective pixels. Alternatively, the pixel signal at the position of the focus detection target pixel may be obtained by pixel addition or pixel interpolation.

Moreover, it is not limited to the flow of the said figure.
For example, after the power is turned on, initial state detection, image sensor driving, preview image display, and the like may be performed. Alternatively, the flow of starting shooting may be shifted to the focus detection subroutine after half-pressing the shutter button, the confirmation image may be displayed after focusing, and the flow may be shifted to the shooting subroutine after the shutter button is fully pressed.

In the above embodiment, the state for calculating the correction value may be calculated in any shooting state in which the object point (subject) is between infinity and a close distance.
Further, the first correction value is calculated in the state of the object point at infinity, the second correction value is calculated in the state of the closest object point, and the correction value is calculated according to the shooting state and stored. It becomes possible to improve the ranging performance.
In this way, in addition to the correction values described above, the first correction value (closest end) and the second correction value (infinity) can be calculated and used in accordance with the shooting situation.

For example, the correction value storage unit 137 stores a correction value when the distance to the subject corresponding to the first subject image signal is estimated to be infinite based on the calculation result of the correlation calculation unit 136.
Further, the correction value storage unit 137 stores a correction value when the distance to the subject corresponding to the first subject image signal is estimated as the closest end (closest distance) based on the calculation result of the correlation calculation unit 136. To do.
Further, the correction value storage unit 137 calculates a correction value when it is estimated that the distance to the subject corresponding to the first subject image signal is neither infinity nor the closest end based on the calculation result of the correlation calculation unit 136. Store.
At this time, the correction value storage unit 137 stores the correction value for each subject distance separately.
As a result, when the subject distance at the time of new shooting is infinity or the close end, by selecting a correction value corresponding to each, a correction value corresponding to at least the difference in the situation such as infinity or the close end can be obtained. Can be used.

In this embodiment, there is no mechanical mechanism (half mirror, sub mirror) in the optical path. There is no influence of aberration due to this mechanical mechanism. Therefore, the correction described above may be performed once. On the other hand, in an imaging apparatus in which a mechanical mechanism (half mirror, sub mirror) exists in the optical path, correction needs to be performed multiple times due to the influence of aberration.
As described above, the present embodiment is an imaging apparatus that employs a phase difference ranging method, is compact, has a small release time lag, and can always perform highly accurate focusing.

  As described above, the present invention is suitable for a phase difference AF type imaging apparatus.

DESCRIPTION OF SYMBOLS 11 Digital still camera 12 Interchangeable lens 13 Camera body 15 Aperture drive part 16 Lens drive part 18 Zooming lens 19 Lens 20 Focusing lens 21 Variable aperture 22 Imaging element 24 Body control part 25 Liquid crystal display element drive circuit 26 Liquid crystal display element
27 eyepiece 28 image pickup device drive circuit 29 memory card 30 lens control unit 31a external input unit 31 p-type well 32α, 32β n-type region 33α, 33β surface p + layer 35 color filter 36 micro lens 41 pixel 42, 52 micro lens 44, 54 Light shielding film 48, 58 Aperture 61, 62, 63, 64 On-chip lens 61a, 62a, 63a, 64a Optical axis 70, 80 Pixel 71, 81 Refractive index distribution lens 72 Color filter 76, 86 Light receiving element 90 Moving / driving Unit 91 Dimming element 120L Left pupil detection pixel 120R Right pupil detection pixel 120U Upper pupil detection pixel 120D Lower pupil detection pixel 121 Imaging pixel 131 A / D conversion unit 132 Signal processing unit 133 Image signal acquisition unit 134 Recorded image configuration unit 135 Display image configuration unit 1 6 correlation calculator 137 correction value storage unit 138 recognition unit 139 phase difference AF control section 140 control section 141 contrast AF controller

Claims (4)

A first subject image signal formed by a light beam from the imaging optical system and a light beam from the imaging optical system, which has a plurality of pixels arranged two-dimensionally, and is formed by pupil division. An image sensor that photoelectrically converts each of the two subject images and the third subject image, and outputs a second subject image signal and a third subject image signal;
Correlation calculation for calculating an interval between two images based on the second subject image signal and the third subject image signal output from the same image pickup device that outputs the first subject image signal. And
A recognition unit that recognizes the best image plane position;
A correction value storage unit that stores a two-image interval as a correction value based on the recognition result information of the recognition unit and the calculation result of the correlation calculation unit;
An imaging signal acquisition unit that acquires the first subject image signal as an imaging signal;
An image constructing unit that generates image data based on the acquired imaging signal;
An image pickup apparatus comprising:   The recognition unit recognizes that the position is the best image plane position by comparing a distance measurement result by a contrast method and a distance measurement result by a phase difference method based on a signal from the same pixel of the image sensor. The imaging apparatus according to claim 1, wherein the imaging apparatus is characterized.   The imaging apparatus according to claim 1, wherein the correction value storage unit stores a result of the correlation calculation unit when the recognition unit recognizes the best image plane position as a correction value.   The correction value storage is close to the correction value when the distance to the subject corresponding to the first subject image signal is estimated to be infinite based on the calculation result of the correlation calculation unit. 3. The correction value at the time of being estimated as an end and the correction value at the time of being estimated that the distance is neither infinity nor the closest end are stored separately. The imaging device described in 1.

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