JP2011081201A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform accurate focus detection in an imaging apparatus having a camera shake correcting function. <P>SOLUTION: The imaging apparatus includes: a solid-state imaging device that has a first focus detecting pixel group to receive luminous flux passing through a first pupil area of a photographic lens, and a second focus detecting pixel group to receive luminous flux passing through a second pupil area of the photographic lens; a focus detection part that detects a focus state of the photographic lens based on a phase difference between a first image obtained from the first focus detecting pixel group and a second image obtained from the second focus detecting pixel group; a shake correction part that corrects shake of a subject image caused by shake of the imaging apparatus; a calculation part that calculates received light distribution of a first focus detecting pixel and a second focus detecting pixel when the shake is corrected by the shake correction part; and a control part that controls whether or not the shake correction part is operated based on the received light distribution calculated by the calculation part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for detecting a focus state of a photographic lens based on an image obtained from a solid-state imaging device for imaging.

  As one of methods for detecting the focus state of the photographing lens, Patent Document 1 discloses an apparatus that performs pupil division type focus detection using a two-dimensional image sensor in which a microlens is formed in each pixel. In the apparatus of Patent Document 1, the photoelectric conversion unit of each pixel constituting the image sensor is divided into a plurality of parts, and the divided photoelectric conversion unit receives different areas of the pupil of the photographing lens through the microlens. It is configured.

  Patent Document 2 discloses a solid-state imaging device that also serves as an image sensor in which pixels in which the relative positions of a microlens and a photoelectric conversion unit are displaced are two-dimensionally arranged. In the solid-state imaging device of Patent Document 2, when detecting the focus state of the photographic lens, the focus state of the photographic lens is detected based on an image generated by a pixel array having different relative displacement directions of the microlens and the photoelectric conversion unit. I'm doing it. On the other hand, when a normal image is captured, an image is generated by adding pixels having different relative displacement directions between the microlens and the photoelectric conversion unit.

  The solid-state imaging device of Patent Document 3 has a configuration in which some of the many pixels constituting the solid-state imaging device are divided into two photoelectric conversion units in order to detect the focus state of the photographic lens. . The photoelectric conversion unit is configured to receive light that has passed through a predetermined region of the pupil of the photographing lens via the microlens.

  FIG. 10A is an explanatory diagram of a light reception distribution of a pixel that performs focus detection located in the center of the solid-state imaging device disclosed in Patent Document 3, and each of the photoelectric conversion units divided into two can receive light. An area on the pupil of the photographing lens is shown. In the figure, the hatched portion in the circle indicates the exit pupil of the photographic lens, and the white area Sα and the area Sβ are areas that can be received by the photoelectric conversion unit divided into two, and the optical axis of the normal photographic lens (see FIG. It is set to be symmetric with respect to the intersection of the middle x axis and the y axis.

  In the camera, the focal state of the photographic lens is detected by performing a correlation operation between the image generated by the light beam transmitted through the region Sα on the pupil of the photographic lens and the image generated by the light beam transmitted through the region Sβ. A method of performing focus detection by performing correlation calculation of images generated from light beams transmitted through different pupil regions of the photographing lens is disclosed in Patent Document 4.

JP-A-58-24105 Japanese Patent No. 2959142 JP 2005-106994 A JP-A-5-127074

  However, when the imaging apparatus has a camera shake correction drive mechanism, the following problems occur in the focus detection method as described above.

  In a camera having the above-described focus detection pixels discretely on the entire surface of the solid-state imaging device, when detecting the focus state of the photographing lens, in general, not only the subject located at the center of the photographing screen but also the periphery of the photographing screen. It is possible to detect the focus even on the subject located at.

  However, depending on the design of the optical path of the photographing lens, vignetting of the light beam by the lens frame of the photographing lens, so-called vignetting, may occur at the peripheral position of the photographing screen. FIG. 10B is a diagram showing a light reception distribution of the focus detection pixels when vignetting occurs in the focus detection pixels located around the photographing screen. Due to vignetting, the area of the other light receiving region Sβ is narrower than the light receiving region Sα of one photoelectric conversion portion in the figure. For this reason, the degree of coincidence between the image generated by the light beam transmitted through the region Sα on the pupil of the photographing lens and the image generated by the light beam transmitted through the region Sβ is low. As a result, there is a drawback that accurate focus detection cannot be performed even if correlation calculation is performed based on an image generated by the light beam transmitted through the region Sα and an image generated by the light beam transmitted through the region Sβ.

  Here, the operation of the camera shake correction drive mechanism will be described. In general, the camera shake correction drive mechanism performs camera shake correction drive for the camera shake amount detected by a gyro sensor or the like, and the following two typical methods are known. The first is a lens shift system that adjusts the optical path by shifting a lens called a shift lens in the photographing optical system with respect to the detected shake amount. The second is an image sensor shift method in which correction is performed by moving a solid-state imaging device at the imaging position of a subject image with respect to a detected shake amount. However, in any of the camera shake correction methods, there is a possibility that new vignetting may occur around the shooting screen due to the change in the optical path, and as a result, the light receiving area of the focus detection pixel may change due to vignetting. .

  FIG. 10C is an explanatory diagram when a change in the light receiving region due to vignetting occurs from the state of FIG. 10A due to the camera shake correction drive. If the area of the light receiving region due to the vignetting of the lens frame is always constant, it may be possible to correct using the area ratio of the light receiving region, but if the light receiving region changes due to camera shake correction driving, the correction cannot be performed, Focus detection with high accuracy is not possible. Furthermore, in the case of the lens shift method, it is sufficient that only the shift lens frame for camera shake correction is designed with a diameter that allows for vignetting, but in the case of the image sensor shift method, all of the vignetting effects are generated. The design of the lens frame must be reviewed.

  The present invention has been made in view of the above-described problems, and an object thereof is to enable highly accurate focus detection even in an imaging apparatus having a camera shake correction function.

  An imaging apparatus according to the present invention is an imaging apparatus, which is a solid-state imaging device that photoelectrically converts a subject image formed by a photographing lens, and receives a light beam that passes through a first pupil region of the photographing lens. A plurality of second focus detection pixels that receive a light beam that passes through a first focus detection pixel group including a plurality of first focus detection pixels and a second pupil region different from the first pupil region of the photographing lens. A solid-state imaging device having a second focus detection pixel group including a plurality of focus detection pixels, a first image obtained from the first focus detection pixel group, and the second focus detection pixel group. By adjusting the optical path of the light beam that passes through the photographing lens and reaches the solid-state image sensor, and detecting the focus state of the photographing lens based on the phase difference of the second image obtained from Said due to shake of the imaging device A shake correction unit that corrects a shake of the subject image, and a light reception distribution of the first focus detection pixel and the second focus detection pixel when the optical path is adjusted by the shake correction unit. Computation means and control means for controlling whether or not to operate the shake correction means based on the received light distribution calculated by the computation means.

  According to the present invention, it is possible to perform focus detection with high accuracy even in an imaging apparatus having a camera shake correction function.

The block diagram of the digital still camera which is an example of the imaging device of this invention. The partial top view of the image sensor which is a CMOS type solid-state image sensor. The partial cross section figure of an image sensor. FIG. 4 is a distribution diagram of received light on a pupil of a photographing lens for focus detection pixels. The received light distribution diagram when vignetting occurs due to camera shake correction driving. The received light distribution diagram when vignetting occurs due to camera shake correction driving. The flowchart of imaging | photography operation | movement including a focus detection operation | movement. The flowchart of the imaging | photography operation | movement of 2nd Embodiment. Explanatory drawing of the liquid crystal display screen of 2nd Embodiment. Light reception distribution explanatory drawing of the conventional solid-state image sensor.

(First embodiment)
1 to 7 are diagrams showing a first embodiment of the present invention. FIG. 1 is a configuration diagram of a digital still camera which is an example of an imaging apparatus of the present invention. FIG. 2 is an image of a CMOS type solid-state imaging device. FIG. 3 is a partial cross-sectional view of the image sensor. FIG. 4 is a designed light reception distribution on the pupil of the photographing lens of the focus detection pixel, FIGS. 5 and 6 are light reception distributions when vignetting occurs due to camera shake correction driving, and FIG. 7 is a photographing including a focus detection operation. It is a flowchart of operation | movement.

  In FIG. 1, reference numeral 2 denotes an image sensor (solid-state image sensor), which is disposed on a planned imaging plane of a photographic lens 5 attached to a camera body 1 of a digital still camera. The camera body 1 includes a camera CPU 20 that controls the entire camera, an image sensor control circuit 21 that is a control unit that drives and controls the image sensor 2, and an image processing unit 24 that performs image processing on image signals captured by the image sensor 2. I have. Further, there are an internal liquid crystal display element 4 and a back liquid crystal display element 6 which are image display units for displaying an image processed image, and an internal liquid crystal display element drive circuit 25 and a back liquid crystal display element drive circuit 26 for driving each of them. I have. Further, an eyepiece 3 for observing the subject image displayed on the internal liquid crystal display element 4, a memory circuit 22 for recording an image taken by the image sensor 2, and an image processed by the image processing unit 24. An interface circuit 23 for outputting to the outside of the camera is also provided. The memory circuit 22 can also store the received light distribution of the image sensor 2.

  The photographic lens 5 is detachable from the camera body 1 and is illustrated with three lenses 5a, 5b, and 5c for convenience, but actually includes a plurality of lenses. The taking lens 5 receives the focus adjustment information sent from the camera CPU 20 of the camera body 1 by the lens CPU 50 via the electrical contact 26. Then, the lens CPU 50 moves the focal lens 5b by the focal lens driving mechanism 51 based on the received focal adjustment information and adjusts it to the in-focus state. Reference numeral 53 denotes an aperture device disposed in the vicinity of the pupil of the photographing lens 5, and is stopped down to a predetermined aperture value by the aperture drive mechanism 52. Further, the camera shake correction drive mechanism 54 having a gyro calculates the camera shake amount resulting from the hand shake of the user having the digital camera from the output of the gyro, and shifts the shift lens 5c in parallel on the xy plane to thereby change the optical path. Adjust to adjust camera shake.

  FIG. 2 is a partial plan view of the image sensor 2. In FIG. 2, 131 and 132 are electrodes. The area delimited by the electrodes 131 and 132 represents one pixel, and the letters “R”, “G”, and “B” written in one pixel represent the hue of the color filter of each pixel. Pixels with the letter “R” transmit red component light, pixels with the letter “G” transmit green component light, and pixels with the letter “B” written Transmits blue component light. In addition, each pixel on which the characters “R”, “G”, and “B” are written is configured to receive light that has passed through the entire pupil region of the photographic lens 5.

  When the color filter array is a Bayer array, one picture element is composed of “R” and “B” pixels and two “G” pixels, but the image sensor arranged in the digital still camera of this embodiment is Focus detection pixels that receive light that has passed through some of the pupil regions (the first pupil region and the second pupil region) of the photographing lens 5 are included in some of the pixels that should be “R” or “B”. Assigned. In the figure, Pα 1, Pβ 1, Pα 2, Pβ 2, Pα 3, and Pβ 3 are focus detection pixels for detecting the focus state of the taking lens 5, and the opening in the x direction is restricted by the electrode 131. The focus detection pixels that are discretely arranged in the screen of the image sensor 2 of the present embodiment include six types in which the opening center position in the x direction of the opening restricted by the electrode 131 is different from the pixel center. Is set.

  For example, a focus detection pixel having a similar electrode opening at a position adjacent to four pixels in the x direction with respect to the focus detection pixel Pα1 in which the opening determined by the electrode 131_3 and the electrode 131_4 is deviated in the + x direction with respect to the pixel center. Pixels are arranged. Pixels having similar electrode openings including these focus detection pixels Pα1 are defined as a first focus detection pixel group.

  In addition, a focus detection pixel Pβ1 in which an opening determined by the electrode 131_1 and the electrode 131_2 substantially coincides with the pixel center is disposed at a position obliquely adjacent to the focus detection pixel Pα1. Further, focus detection pixels having similar electrode openings are disposed at positions adjacent to the focus detection pixel Pβ1 by four pixels in the x direction. A pixel having the same electrode opening including these focus detection pixels Pβ1 is defined as a second focus detection pixel group. Similarly, focus detection pixel groups having the same electrode openings as Pα2, Pβ2, Pα3, and Pβ3 are designated as a third focus detection pixel group, a fourth focus detection pixel group, and a fifth focus detection pixel, respectively. Group, and a sixth focus detection pixel group.

  The focus detection calculation unit (camera CPU 20) provided in the digital still camera of the present embodiment is configured to output a first focus detection image (first image) from the first focus detection pixel group having the same electrode opening as the focus detection pixel Pα1. 1 image). Similarly, a second focus detection image (second image) is generated from the second focus detection pixel group having the same electrode opening as that of the focus detection pixel Pβ1. Further, the focus detection calculation unit (camera CPU 20) performs correlation calculation based on the phase difference between the first focus detection image and the second focus detection image, so that the focus detection pixels Pα1 and Pβ1 are located. The focus state of the taking lens 5 at is detected. A focus detection calculation unit that performs a correlation calculation based on the first focus detection image and the second focus detection image is defined as a first focus detection calculation unit.

  Similarly, the focus detection calculation unit (camera CPU 20) generates a third focus detection image from the third focus detection pixel group having the same electrode opening as that of the focus detection pixel Pα2. Similarly, a fourth focus detection image is generated from the fourth focus detection pixel group having the same electrode opening as that of the focus detection pixel Pβ2. Further, the focus detection calculation unit (camera CPU 20, second focus detection calculation unit) performs correlation calculation based on the third focus detection image and the fourth focus detection image, and thereby detects the focus detection pixel Pα 2. The focus state of the taking lens 5 in the region where Pβ2 is located is detected. A focus detection calculation unit that performs correlation calculation based on the third focus detection image (third image) and the fourth focus detection image (fourth image) is defined as a second focus detection calculation unit.

  Similarly, the focus detection calculation unit (camera CPU 20) generates a fifth focus detection image from the fifth focus detection pixel group having the same electrode opening as the focus detection pixel Pα3. Similarly, a sixth focus detection image is generated from a sixth focus detection pixel group having the same electrode opening as that of the focus detection pixel Pβ3. Further, the focus detection calculation unit (camera CPU 20) performs a correlation calculation based on the fifth focus detection image and the sixth focus detection image, thereby capturing an image in the region where the focus detection pixels Pα3 and Pβ3 are located. The focus state of the lens 5 is detected. A focus detection calculation unit that performs correlation calculation based on the fifth focus detection image and the sixth focus detection image is defined as a third focus detection calculation unit. Note that the first focus detection calculator, the second focus detection calculator, and the third focus detection calculator are all realized by the camera CPU 20.

  Further, the focus detection calculation unit (camera CPU 20) is configured to focus the photographing lens 5 in the region where the focus detection pixels Pα1 and Pβ1 are located, and the photographing lens in the region where the focus detection pixels Pα2 and Pβ2 and Pα3 and Pβ3 are located. Average each of the five focus states. Further, the focus detection calculation unit sends focus adjustment information to the focus lens driving mechanism 51 based on the focus detection result to adjust the focus of the photographing lens 5.

  On the other hand, when capturing a normal image, focus detection pixels whose pixel electrode openings are limited are treated as defective pixels, and image signals are generated by performing interpolation processing from pixels located around the focus detection pixels. The

  3 is a cross-sectional view of the A-A ′ plane shown in the partial plan view of the image sensor 2 in FIG. 2. The right pixel in FIG. 3 shows a pixel that can receive light that has passed through the entire pupil region of the photographic lens 5, and the left pixel in the drawing can receive a light beam from a part of the pupil region of the photographic lens 5. A focus detection pixel is shown. In the image sensor 2, a photoelectric conversion unit 111 is formed inside a silicon substrate 110. The signal charge generated in the photoelectric conversion unit 111 is output to the outside through a floating diffusion unit (not shown), the first electrode 131, and the second electrode 132. An interlayer insulating film 121 is formed between the photoelectric conversion unit 111 and the electrode 131, and an interlayer insulating film 122 is formed between the electrode 131 and the electrode 132. In addition, an interlayer insulating film 123 is formed on the light incident side of the electrode 132, and a passivation film 140 and a planarizing layer 150 are further formed. On the light incident side of the planarization layer 150, a color filter layer 151, a planarization layer 152, and a microlens 153 are formed. Here, the power of the microlens 153 is set so that the pupil of the photographing lens 5 and the photoelectric conversion unit 111 are substantially conjugate. In the pixel located at the center of the image sensor 2, the microlens 153 is disposed at the center of the pixel, and at the pixels located at the periphery, the microlens 153 is disposed deviated toward the optical axis side of the photographing lens 5.

  The subject light transmitted through the photographing lens 5 is condensed near the image sensor 2. Further, the light reaching each pixel of the image sensor 2 is refracted by the microlens 153 and condensed on the photoelectric conversion unit 111. In the pixel on the right side in the drawing used for normal imaging, the first electrode 131 and the second electrode 132 are provided so as not to block incident light. On the other hand, in the focus detection pixel that performs focus detection of the photographic lens 5 on the left side in the drawing, a part of the electrode 131 is configured to cover the photoelectric conversion unit 111. As a result, the focus detection pixel on the left side of the drawing can receive a light beam that passes through a part of the pupil of the photographing lens 5. Further, in order to prevent the output of the photoelectric conversion unit 111 from being reduced because the electrode 131 blocks a part of the incident light beam, the color filter layer 154 of the focus detection pixel has high transmittance that does not absorb light. It is made of resin.

  The focus detection pixels that are discretely arranged in the screen of the image sensor 2 receive light that has passed through the photographing lens 5 by making the relative position of the microlens 153 and the center of the opening of the electrode 131 different. It is comprised so that distribution may differ.

  FIG. 4 is a diagram showing a designed light reception distribution on the pupil of the photographing lens 5 of the focus detection pixels arranged in a part of the image sensor 2. FIG. 4A shows a design light distribution on the pupil of the photographing lens 5 of the focus detection pixel Pα1 shown in the partial plan view of the image sensor 2 in FIG. The center of the aperture determined by the electrode 131_3 and the electrode 131_4 of the focus detection pixel Pα1 is greatly displaced in the + x direction with respect to the center of the pixel. Therefore, the center of the light receiving region Sα1a of the photoelectric conversion unit of the focus detection pixel Pα1 is on the x axis in the drawing on the exit pupil of the photographing lens 5 with respect to the optical axis (intersection of the x axis and the y axis in the drawing). Is shifted by -xα1.

  FIG. 4B shows a design light distribution on the pupil of the photographing lens 5 of the focus detection pixel Pβ1 shown in the partial plan view of the image sensor 2 in FIG. The center of the aperture determined by the electrode 131_1 and the electrode 131_2 of the focus detection pixel Pβ1 substantially coincides with the center of the pixel. For this reason, the center of the light receiving region Sβ1a of the photoelectric conversion unit of the focus detection pixel Pβ1 is approximately the optical axis (intersection of the x axis and the y axis in the drawing) on the x axis in the drawing on the exit pupil of the photographing lens 5. Match.

  FIG. 4C shows a design light distribution on the pupil of the photographing lens 5 of the focus detection pixel Pα2 shown in the partial plan view of the image sensor 2 in FIG. The center of the opening determined by the electrode 131_3 and the electrode 131_4 of the focus detection pixel Pα2 is deviated by a predetermined amount in the + x direction with respect to the center of the pixel. Therefore, the center of the light receiving region Sα2a of the photoelectric conversion unit of the focus detection pixel Pα2 is on the x axis in the drawing on the exit pupil of the photographing lens 5 with respect to the optical axis (the intersection of the x axis and the y axis in the drawing). The distance is -xα2.

  FIG. 4D shows a design light distribution on the pupil of the photographing lens 5 of the focus detection pixel Pβ2 shown in the partial plan view of the image sensor 2 in FIG. The center of the aperture determined by the electrode 131_1 and the electrode 131_2 of the focus detection pixel Pβ2 is displaced by a predetermined amount in the −x direction with respect to the center of the pixel. Therefore, the center of the light receiving region Sβ2a of the photoelectric conversion unit of the focus detection pixel Pβ2 is on the x axis in the drawing on the exit pupil of the photographing lens 5 with respect to the optical axis (the intersection of the x axis and the y axis in the drawing). The distance xβ2 is deviated.

  FIG. 4E shows a designed light reception distribution on the pupil of the photographing lens 5 of the focus detection pixel Pα3 shown in the partial plan view of the image sensor 2 in FIG. The center of the aperture determined by the electrode 131_3 and the electrode 131_4 of the focus detection pixel Pα3 is substantially coincident with the center of the pixel. Therefore, the center of the light-receiving area Sα3a of the photoelectric conversion unit of the focus detection pixel Pα3 is substantially the same as the optical axis (intersection of the x axis and the y axis in the drawing) on the x axis in the drawing on the exit pupil of the photographing lens 5. Match. Here, the designed light reception distribution on the pupil of the photographing lens 5 of the focus detection pixel Pα3 is substantially the same as the designed light reception distribution on the pupil of the photographing lens 5 of the focus detection pixel Pβ1.

  FIG. 4F shows a design light distribution on the pupil of the photographing lens 5 of the focus detection pixel Pβ3 shown in the partial plan view of the image sensor 2 in FIG. The center of the aperture determined by the electrode 131_1 and the electrode 131_2 of the focus detection pixel Pβ3 is greatly displaced in the −x direction with respect to the center of the pixel. Therefore, the center of the light receiving region Sβ3a of the photoelectric conversion unit of the focus detection pixel Pβ3 is on the x axis in the drawing on the exit pupil of the photographing lens 5 with respect to the optical axis (the intersection of the x axis and the y axis in the drawing). The distance xβ3 is deviated.

  FIG. 4G shows a design light distribution on the pupil of the photographing lens 5 of the normal imaging pixels shown in the partial plan view of the image sensor 2 in FIG. Since the electrode 131 of the normal imaging pixel is configured not to shield the photoelectric conversion unit, the photoelectric conversion unit of the normal imaging pixel can receive the entire pupil region Sγ of the photographing lens 5. At this time, the center of the light-receiving area Sγ of the normal imaging pixel substantially coincides with the optical axis on the exit pupil of the photographing lens 5 (intersection of the x axis and the y axis in the figure). As described above, the image sensor 2 according to the present embodiment includes six types of focus detection pixel groups in which the center of the light reception distribution exists at different positions on the x-axis.

  FIG. 5 is an explanatory diagram of the light reception distribution of the focus detection pixels around the photographing screen when the camera shake correction drive mechanism 54 is operated. As shown in FIG. 5, vignetting (vignetting) may occur in the lens frame of the image stabilization drive mechanism 54 around the photographing screen, and the vignetting of the photoelectric conversion unit of the focus detection pixel shown in FIG. The light receiving area Sα1b is narrowed. Therefore, the degree of coincidence between the image generated by the light beam transmitted through the light receiving region Sα1b of the focus detection pixel in FIG. 5A and the image generated by the light beam transmitted through the light receiving region Sβ1b in FIG. As a result, the accuracy of the correlation calculation is reduced. However, since the center of the light receiving area of the focus detection pixel in FIGS. 5C and 5E is displaced in the + x direction with respect to the light reception area of the focus detection pixel in FIG. No vignetting due to the operation of the correction drive mechanism 54 occurs in the light receiving regions Sα2b and Sα3b. Therefore, in the peripheral area of the imaging screen where vignetting occurs as described above, the focus detection selection unit (camera CPU 20) is represented by the focus detection pixel Pα1 in which the light receiving area of the photoelectric conversion unit has an effect of vignetting. It is selected not to use the focus detection correlation calculation result based on the images obtained by the first focus detection pixel group and the second focus detection pixel group represented by Pβ1. Then, the correlation calculation of the focus detection is performed based on the images obtained by the third, fourth, fifth and sixth focus detection pixel groups represented by the remaining Pα2 and Pβ2 and Pα3 and Pβ3, respectively. Focus detection is performed by averaging the results. In this way, accurate focus detection can be performed even if vignetting occurs due to the lens frame.

  FIG. 6 shows a light reception distribution of focus detection pixels in the periphery of the photographing screen when the photographing correction driving mechanism 54 is driven when a photographing lens having a camera shake correction driving mechanism different from the photographing lens shown in FIG. 5 is attached. It is explanatory drawing of. In the photoelectric conversion unit of each focus detection pixel, the influence of vignetting becomes larger than that of the focus detection pixel shown in FIG. 5, and the light receiving region Sα1c of the focus detection pixel in FIG. It is narrower than the light receiving area Sα1b. Also, in the light receiving area Sα2c of FIG. 6C, the influence of vignetting is caused by the lens frame of the camera shake correction drive mechanism 54, which is narrower than the light receiving area Sα2b of FIG. 5C. Therefore, it is conceivable to perform correlation calculation for focus detection only based on an image obtained by a focus detection pixel group represented by focus detection pixels Pα3 and Pβ3 that are not affected by vignetting in the light receiving region of the photoelectric conversion unit. . However, the accuracy of focus detection is higher than that in the case of performing focus detection based on images obtained from focus detection pixel groups represented by focus detection pixels Pα1 and Pβ1, Pα2 and Pβ2, Pα3 and Pβ3. The result is reduced to 1/3. Therefore, the S / N of the focus detection result obtained by averaging the correlation calculation results is deteriorated. Therefore, in the present embodiment, two or more sets of focus among the focus detection pixel groups represented by the three sets of focus detection pixels Pα1 and Pβ1, Pα2 and Pβ2, Pα3, and Pβ3 by the operation of the camera shake correction drive mechanism 54. When it is estimated that vignetting occurs in the light receiving region of the detection pixel, the driving of the camera shake correction drive mechanism 54 is prohibited. Then, after the focus detection operation is completed, the operation of the camera shake correction drive mechanism 54 is permitted.

  The actual shooting operation in this embodiment will be described using the flowchart of FIG. When the photographing operation is started, the flowchart starts. In step S1001, the mounted photographing lens 5 is recognized, and optical information such as focal length information of the photographing lens 5, lens frame information, and a driving amount of the camera shake correction drive mechanism is read. At this time, the optical information of the photographic lens 5 may be recorded by providing a memory on the photographic lens 5 side, or stored in the memory on the digital still camera 1 side, and obtained by judging the attached lens. Also good.

  Next, in step S1002, the amount of vignetting that occurs when the camera shake correction mechanism 54 is driven is calculated using the optical information of the photographing lens 5 read in step S1001. Then, as shown in FIG. 6, two or more sets of focus detection are performed among the focus detection pixel groups represented by the three sets of focus detection pixels Pα1 and Pβ1, Pα2 and Pβ2, Pα3 and Pβ3 by camera shake correction driving. When it is estimated that vignetting occurs in the light receiving area of the pixel group for use, the vignetting determination unit (camera CPU 20) sets a flag indicating that there is an vignetting effect.

  In step S1003, when the user presses an operation button (not shown), a focus detection operation command is issued and the focus detection operation is started. In step S1004, it is determined whether the shooting mode is a camera shake correction drive mode. If it is determined that the camera shake correction drive mode is OFF, the focus detection operation is not affected by vignetting, and the process advances to step S1007. If it is determined in step S1004 that the shooting mode is the camera shake correction drive mode ON, the process proceeds to step S1005, and it is determined whether or not a flag indicating the influence of vignetting is caused by the camera shake correction drive. If the flag with vignetting is not set, the process proceeds to step S1007. If the vignetting flag is set, the process proceeds to step S1006, and the camera shake correction drive is temporarily stopped by the camera shake correction drive control unit (camera CPU 20). Actually, the vignetting depends on the amount of camera shake correction. Therefore, after the camera shake correction drive is stopped, the shift lens is returned to the center to eliminate the above-mentioned vignetting.

  Next, in step S1007, calculation for focus detection operation is performed. In step S1007, correlation calculation for focus detection is performed using the image obtained from the focus detection pixel group in the entire shooting screen. The subject distance of each subject imaged on the shooting screen is detected from the correlation calculation result, and the subject located closest to the user is determined as the target subject. In step S1008, the focus lens driving mechanism 51 is driven based on the focus detection result so that the target subject is focused. When the focus lens 5b is driven to the target position in step S1008, focus detection is performed again using the image from the focus detection pixel group in order to determine whether or not the target subject is in focus in step S1009. Correlation calculation for is performed. In step S1010, the process returns to step S1008 and the driving of the focus lens 5b and the focus detection calculation are repeated until it is determined that the target subject is in focus as a result of the correlation calculation. If it is determined in step S1010 that the target subject is in focus, the process proceeds to step S1011 to determine again whether the shooting mode is the camera shake correction drive mode. If it is determined in step S1011 that the camera shake correction drive mode is not selected, the process proceeds to step S1014. If the camera shake correction drive mode is selected, the process proceeds to step S1012, and in step S1004 it is determined whether camera shake correction drive is prohibited and stopped. To do. If it is determined in step S1012 that the camera shake correction drive mode is set and the camera shake correction drive is in operation, the process proceeds to S1014. If it is determined that the camera shake correction drive is stopped, the process proceeds to step S1013 and the camera shake correction drive is performed again. Is started.

  In step S1014, when an operation of turning on the shooting button is detected, the process proceeds to step S1015, and an exposure operation under shooting conditions such as an exposure time, that is, shooting is performed on the imaging surface of the image sensor 2. If the shooting button ON is not detected in step S1014, the flow with step S1016 is repeated until a predetermined time elapses, and the detection of the shooting button ON is awaited. When a predetermined time elapses in step S1016, it can be considered that the target subject has moved and is out of focus. Therefore, the process returns to step S1004 and the operation associated with focus detection is repeated again. When shooting is performed in step S1015, the flowchart ends.

  As described above, in the present embodiment, first, the amount of vignetting generated by the camera shake correction drive of the mounted photographic lens is calculated, and it is determined whether to prohibit the camera shake correction drive during the focus detection operation based on the degree of the vignetting amount. . If it is determined that the influence of vignetting due to the camera shake correction drive is large, the camera shake correction drive is temporarily stopped during the focus detection operation, and after the in-focus state is detected, the camera shake correction drive is started again to perform the photographing operation. Thereby, even when vignetting occurs due to camera shake correction driving, it is possible to perform focus detection with high accuracy.

  In the present embodiment, there are six types of focus detection pixel groups having different electrode opening shapes, two in three sets, but more combinations may be provided. For example, when there are 10 types of focus detection pixel groups each having 5 types of electrode openings, 3 or more sets of focus detection pixels in which the influence of vignetting due to camera shake correction driving is a majority of the 5 sets When the group is affected, it may be determined that the camera shake correction drive during the focus detection operation is prohibited. In addition, two sets of focus detection pixel groups having different electrode opening shapes may be used in two sets of four types. In such a case, when the focus detection pixel group has an electrode opening shape with only one set of vignetting, or when there is no vignetting, camera shake correction driving during focus detection operation is possible, and two sets of vignetting are affected. Camera shake correction drive during the focus detection operation is prohibited.

  In the present embodiment, the image pickup apparatus having the lens shift type camera shake correction drive mechanism has been described. However, the present invention can also be applied to an image pickup apparatus having an image sensor shift type or other camera shake correction drive mechanism that generates vignetting. It is.

  Although it has been described that the vignetting effect at the shooting screen position changes when the photographic lens changes, the vignetting effect also changes when the zoom state of the photographic lens changes. Although not shown in the photographic lens 5 of FIG. 1, when the photographic lens can change the optical path and adjust the focal length (when zooming is possible), the zoom state of the photographic lens is detected and the amount of vignetting is calculated. I need to fix it. Whether or not the camera shake correction drive mechanism can be driven during the focus detection operation is determined according to the amount of vignetting calculated again.

(Second Embodiment)
Hereinafter, the imaging apparatus according to the second embodiment will be described with reference to FIGS. 8 and 9. Since the configuration of the imaging apparatus of the second embodiment is the same as that of the imaging apparatus of the first embodiment, the description thereof is omitted. In the first embodiment, the amount of vignetting generated by the camera shake correction drive is calculated from the optical information of the mounted photographing lens, and the prohibition of the camera shake correction drive during the focus detection operation is determined according to the result. In the second embodiment, the vignetting amount at each position in the shooting screen generated by the camera shake correction drive is calculated from the optical information of the mounted shooting lens, and only the shooting screen range (screen range) that is not affected by the vignetting is calculated. Enables focus detection operation.

  FIG. 8 is a flowchart showing the shooting operation of the imaging apparatus according to the second embodiment. When the flow starts, first, in step S2001, the mounted photographing lens 5 is recognized, and optical information such as focal length information of the photographing lens 5, lens frame information, and a driving amount of the camera shake correction drive mechanism is read.

  Next, in step S2002, the amount of vignetting that occurs when the camera shake correction drive mechanism 54 is driven is calculated using the optical information of the photographing lens 5 read in step S2001. In step S2003, the vignetting determination unit (camera CPU 20) calculates a range affected by vignetting on the shooting screen, and calculates a focus detectable range. First, vignetting occurs in the light receiving areas of two or more focus detection pixels among the focus detection pixel groups represented by three pairs of focus detection pixels Pα1 and Pβ1, Pα2 and Pβ2, Pα3, and Pβ3. Calculate the range of the shooting screen where the occurs. The vignetting has a large effect in the peripheral area of the shooting screen, and the effect of vignetting is reduced or the vignetting does not occur when the image is close to the center of the shooting screen. Therefore, since the accuracy of the correlation calculation is lowered only in the peripheral area of the shooting screen where the influence of vignetting is large, the focus detection operation is set not to be performed. FIG. 9 is a schematic diagram of a shooting screen. The outside of the area 202 is greatly affected by vignetting, so that focus detection is not performed, and only the inside of the area 202 is set as a focus detectable range.

  In step S2004, when the user presses the operation button, a focus detection operation command is issued and the focus detection operation is started. In step S2005, it is determined whether the shooting mode is the camera shake correction drive mode. If it is determined in step S2005 that the shooting mode is not the camera shake correction drive mode, the process proceeds to step S2013, and since there is no vignetting effect due to the camera shake correction drive, the entire shooting screen is set as a focus detectable range. On the other hand, if it is determined that the camera shake correction drive mode is selected, the process proceeds to step S2006, and the result calculated in step S2003 is set as the focus detectable range by the focus detectable range determining unit (camera CPU 20). Then, the focus detectable range display unit (camera CPU 20) displays the focus detectable range on the internal liquid crystal display element 4 or the rear liquid crystal display element 6, and informs the user of the range in which the focus detection operation within the photographing screen can be performed.

  Next, in step S2007, correlation calculation for focus detection is performed using an image obtained from the focus detection pixel group in the focus detectable range. The subject distance of each subject imaged on the shooting screen is detected from the correlation calculation result, and the subject closest to the user is determined as the target subject. In step S2008, the focus lens driving mechanism 51 is driven based on the focus detection result so that the target subject is focused. When the focus lens 5b is driven to the target position in step S2008, focus detection is performed again using the image from the focus detection pixel group in order to determine whether or not the target subject is in focus in step S2009. Correlation calculation for is performed. Next, until it is determined in step S2010 that the target object is in focus as a result of the correlation calculation, the process returns to step S2008, and the driving of the focus lens 5b and the focus detection calculation are repeated.

  Hereinafter, the operations in steps S2011 to S2012 and step S2014 are the same as the operations in steps S1014 to S1015 and step S1016 of the first embodiment, and thus description thereof is omitted. When step S2012 ends, the flow ends.

  As described above, in the second embodiment, the amount of vignetting at each position in the shooting screen generated by the camera shake correction drive is calculated from the optical information of the mounted shooting lens, and the camera is in the camera shake correction drive mode. The focus detection operation can be performed only in the range of the shooting screen with less influence of vignetting. And it displays on a liquid crystal display device as a focus detectable range, and notifies the range which performs focus detection to a user. When not in the camera shake correction drive mode, the entire area of the shooting screen is set as a focus detectable range.

  In the second embodiment, the focus detection detectable range is set based on the calculated amount of vignetting at each position in the shooting screen, and the focus detection correlation calculation is performed only within the focus detection possible range. You may combine with form. For example, the operation of the first embodiment and the operation of the second embodiment may be set as different modes, and the focus detection operation may be switched according to a user setting.

Claims (5)

An imaging device,
A solid-state imaging device that photoelectrically converts a subject image formed by a photographic lens, and includes a first focus detection pixel that receives a light beam that passes through a first pupil region of the photographic lens. A second focus detection pixel comprising a focus detection pixel group and a plurality of second focus detection pixels that receive a light beam passing through a second pupil region different from the first pupil region of the photographing lens. A solid-state imaging device having a group;
A focus for detecting a focus state of the photographing lens based on a phase difference between a first image obtained from the first focus detection pixel group and a second image obtained from the second focus detection pixel group. Detection means;
A shake correction unit that corrects a shake of the subject image caused by a shake of the imaging device by adjusting an optical path of a light beam that passes through the photographing lens and reaches the solid-state imaging device;
Arithmetic means for calculating a light reception distribution of the first focus detection pixel and the second focus detection pixel when the optical path is adjusted by the shake correction means;
Control means for controlling whether to operate the shake correction means based on the received light distribution calculated by the calculation means;
An imaging apparatus comprising:   A third focus detection pixel group consisting of a plurality of third focus detection pixels whose opening positions are different from those of the first focus detection pixels, and the second focus detection pixels have an opening position. From a fourth focus detection pixel group including a plurality of different fourth focus detection pixels, a third image obtained from the third focus detection pixel group, and the fourth focus detection pixel group Second focus detection means for detecting the focus state of the photographing lens based on the phase difference of the obtained fourth image, and the calculation means includes a third focus detection pixel and the fourth focus detection. The light receiving distribution of the pixels is further calculated, and the control means uses the detection result of either the focus detecting means or the second focus detecting means based on the light receiving distribution calculated by the calculating means. Select whether to adjust the focus of the lens. The imaging apparatus according to claim 1. An imaging device,
A solid-state imaging device that photoelectrically converts a subject image formed by a photographic lens, and includes a first focus detection pixel that receives a light beam that passes through a first pupil region of the photographic lens. A second focus detection pixel comprising a focus detection pixel group and a plurality of second focus detection pixels that receive a light beam passing through a second pupil region different from the first pupil region of the photographing lens. A solid-state imaging device having a group;
A focus for detecting a focus state of the photographing lens based on a phase difference between a first image obtained from the first focus detection pixel group and a second image obtained from the second focus detection pixel group. Detection means;
A shake correction unit that corrects a shake of the subject image caused by a shake of the imaging device by adjusting an optical path of a light beam that passes through the photographing lens and reaches the solid-state imaging device;
Arithmetic means for calculating a light reception distribution of the first focus detection pixel and the second focus detection pixel when the optical path is adjusted by the shake correction means;
Control means for controlling a screen range used for focus detection within the screen of the solid-state imaging device, based on the received light distribution calculated by the computing means;
An imaging apparatus comprising:   The imaging apparatus according to claim 3, further comprising display means for displaying a screen range used for the focus detection.   A third focus detection pixel group consisting of a plurality of third focus detection pixels whose opening positions are different from those of the first focus detection pixels, and the second focus detection pixels have an opening position. From a fourth focus detection pixel group including a plurality of different fourth focus detection pixels, a third image obtained from the third focus detection pixel group, and the fourth focus detection pixel group Second focus detection means for detecting the focus state of the photographing lens based on the phase difference of the obtained fourth image, and the calculation means includes a third focus detection pixel and the fourth focus detection. The light receiving distribution of the pixels is further calculated, and the control means uses the detection result of either the focus detecting means or the second focus detecting means based on the light receiving distribution calculated by the calculating means. Select whether to adjust the focus of the lens. The imaging apparatus according to claim 3.

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