JP2017107064A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve focus detection accuracy.SOLUTION: An imaging device comprises: an image pick-up element that is a pixel having a first and second photoelectric conversion units receiving a first and second light fluxes passing through a different pupil area of an imaging optical system, and has a first pixel generating a signal due to light of a first color and a second pixel generating a signal due to light of a second color alternately arranged in a prescribed direction; and a focus detection unit that generates a focus detection signal using a signal from the first photoelectric conversion unit in a plurality of first pixels and a signal from the second photoelectric conversion unit in the plurality of first pixels, and detects focus of the imaging optical system on the basis of the focus detection signal. The focus detection unit is configured to generate a focus detection signal of a position of the second pixel of the focus detection signal, using the signal of the plurality of first pixels located around the second pixel.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an imaging apparatus.

  A technique is known that has focus detection pixels in a Bayer array and detects a focus by an image plane phase difference method (see Patent Document 1). This technique has a problem that the focus detection accuracy is lowered because the focus detection signal of the same color is generated every other pixel.

JP 2001-83407 A

An imaging apparatus according to a first aspect of the present invention is a pixel having first and second photoelectric conversion units that receive first and second light fluxes that have passed through different pupil regions of a photographing optical system, An image sensor in which a first pixel that generates a signal based on light of a color and a second pixel that generates a signal based on light of a second color are alternately arranged in a predetermined direction, and the first pixels in a plurality of the first pixels A focus detection signal is generated using a signal from one photoelectric conversion unit and signals from the second photoelectric conversion unit in a plurality of the first pixels, and the focus of the photographing optical system is based on the focus detection signal. A focus detection unit that detects the focus detection signal at the position of the second pixel in the focus detection signal, and the plurality of the first pixels positioned around the second pixel. Generated using pixel signals.
An imaging apparatus according to a second aspect of the present invention is a pixel having first and second photoelectric conversion units that receive first and second light fluxes that have passed through different pupil regions of a photographing optical system, An image sensor in which a first pixel that generates a signal based on light of a color and a second pixel that generates a signal based on light of a second color are alternately arranged in a predetermined direction, and the first pixels in a plurality of the first pixels A focus detection signal is generated using a signal from one photoelectric conversion unit and signals from the second photoelectric conversion unit in a plurality of the first pixels, and the focus of the photographing optical system is based on the focus detection signal. A focus detection unit that detects m, and n is an integer greater than or equal to 2 in the imaging device, and a reference range consisting of pixels of m rows and n columns is one pixel in the predetermined direction. Set multiple values by shifting each one of the multiple reference ranges. A plurality of focus detection signals corresponding to the plurality of focus detection signals are generated using the signals of the plurality of first pixels included in each reference range, and the center of gravity positions of the plurality of focus detection signals are It generates so that it may line up in a predetermined direction.
An imaging apparatus according to a third aspect of the present invention is a pixel having first and second photoelectric conversion units that receive first and second light fluxes that have passed through different pupil regions of a photographing optical system, An image sensor in which a first pixel that generates a signal based on light of a color and a second pixel that generates a signal based on light of a second color are alternately arranged in a predetermined direction, and the first pixels in a plurality of the first pixels A focus detection signal is generated using a signal from one photoelectric conversion unit and signals from the second photoelectric conversion unit in a plurality of the first pixels, and the focus of the photographing optical system is based on the focus detection signal. A focus detection unit that detects the focus detection signal at the position of the first pixel in the focus detection signal around the signal of the first pixel and the first pixel. It produces | generates using the signal of the said some 1st pixel located.

  According to the present invention, focus detection accuracy can be improved.

It is a block diagram which shows the structure of a digital camera. It is a figure which shows the structure of a body control circuit part. It is a front view which shows the detailed structure of an image pick-up element. It is sectional drawing which shows the structure of a pixel. It is a figure which shows the structure of the focus detection optical system of the pupil division type phase difference detection system using a micro lens. It is a figure explaining the pixel row | line | column which produces | generates a focus detection signal. It is a figure explaining a reference range. It is a figure explaining the weighting coefficient at the time of producing | generating a focus detection signal. It is a figure explaining a reference range. It is a figure explaining the weighting coefficient at the time of producing | generating a focus detection signal. (A) shows an example of a subject pattern, and (b) shows an example of a graph of a focus detection signal. (A) shows an example of a subject pattern, and (b) shows an example of a graph of a focus detection signal. 4 is a flowchart illustrating a flow of an imaging operation of a digital camera in the first embodiment. 9 is a flowchart illustrating a flow of an imaging operation of a digital camera in the second embodiment. It is a figure explaining the reference range at the time of producing | generating a focus detection signal from the signal of G pixel. It is a figure explaining the reference range at the time of producing | generating a focus detection signal from the signal of R pixel. It is a figure explaining the reference range at the time of producing | generating a focus detection signal from the signal of B pixel.

-First embodiment-
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a lens interchangeable digital camera that is an example of an imaging apparatus according to the present embodiment. The digital camera shown in FIG. 1 includes an interchangeable lens 110 and a camera body 100, and the interchangeable lens 110 is attached to the camera body 100 via a lens mounting portion 105.

  The interchangeable lens 110 includes a lens control circuit unit 111, a zoom lens 112, a focus lens 113, an anti-vibration lens 114, a diaphragm 115, a lens operation unit 116, and the like. The lens control circuit unit 111 includes a CPU and peripheral components such as a memory. The lens control circuit unit 111 controls the driving of the focus lens 113 and the diaphragm 115, detects the positions of the zoom lens 112 and the focus lens 113, transmits lens information to the camera body 100, and the camera. The camera information is received from the body 100.

  The camera body 100 includes an image sensor 101, a body control circuit unit 102, a body operation unit 103, a display unit 104, and the like. The image sensor 101 is disposed on the planned imaging plane (planned focal plane) of the interchangeable lens 110 and photoelectrically converts the subject image formed by the interchangeable lens 110. The body operation unit 103 includes a shutter button, a focus detection area setting member, and the like. The display unit 104 is a liquid crystal monitor (back monitor) mounted on the back surface of the camera body 100.

  The body control circuit unit 102 includes a CPU and peripheral components such as a memory. The body control circuit unit 102 controls the driving of the image sensor 101, reads out image signals and focus detection signals, performs focus detection calculation based on the focus detection signals and adjusts the focus of the interchangeable lens 110, processes and records image signals, and operates the digital camera. Control and so on. The body control circuit unit 102 communicates with the lens control circuit unit 111 via an electrical contact 106 provided in the lens mounting unit 105 to receive lens information and transmit camera information (defocus amount, aperture value, etc.). Do.

  FIG. 2 is a block diagram illustrating a configuration of the body control circuit unit 102. The body control circuit unit 102 includes an A / D conversion unit 202, a CPU 203, an image sensor driving circuit 204, an image processing circuit 205, a focus detection calculation circuit 206, a communication unit 210, and the like. In the image sensor 101, the timing (frame rate) of photoelectric conversion signal accumulation and signal readout is controlled by the image sensor driving circuit 204. An output signal from the image sensor 101 is converted into digital data by the A / D converter 202 and output to a memory (not shown) attached to the CPU 203.

  The focus detection calculation circuit 206 calculates a defocus amount based on an output signal corresponding to a predetermined focus detection area from the image sensor 101. The CPU 203 transmits the defocus amount calculated by the focus detection calculation circuit 206 to the lens control circuit unit 111 of the interchangeable lens 110 using the communication unit 210. The lens control circuit unit 111 calculates the drive amount of the focus lens 113 based on the defocus amount received from the camera body 100, and drives the focus lens 113 with a motor or the like (not shown) based on this drive amount to focus. Move to position.

  An output signal from the image sensor 101 is subjected to various image processing by the image processing circuit 205 and is generated as image data, and is displayed on the display unit 104 or recorded on the memory card 207.

  The CPU 203 detects an operation signal from the body operation unit 103 and controls operations (such as shooting processing and setting of a focus detection area) according to the detection result.

  FIG. 3 is a front view showing a detailed configuration of the image sensor 101, and is an enlarged view of a part of the image sensor 101. FIG. As shown in FIG. 3, the image sensor 101 includes a plurality of pixels 311 arranged in a two-dimensional manner. The pixel 311 includes a microlens 10 and a pair of photoelectric conversion units 12 and 13. In FIG. 3, the pair of photoelectric conversion units 12 and 13 are arranged side by side in the horizontal direction. Further, color filters (R: red filter, G: green filter, B: blue filter) are arranged at the position of each pixel 311 according to the rules of the Bayer array. That is, as the pixel 311, the R pixel having the spectral sensitivity of the red component (that is, the red filter is disposed), the G pixel having the spectral sensitivity of the green component (that is, the green filter is disposed), and the spectral sensitivity of the blue component. And a B pixel (that is, a blue filter is disposed). The pixel 311 serves as both a photographing pixel and a focus detection pixel, and the pixel 311 is disposed on the entire surface of the image sensor 101. Therefore, focus detection can be performed at an arbitrary position on the shooting screen. Further, at the time of photographing, it is possible to generate photographed image data by adding the outputs of the pair of photoelectric conversion units 12 and 13 of the pixel 311.

  FIG. 4 is a cross-sectional view illustrating a configuration of the pixel 311. In the pixel 311, the microlens 10 is disposed in front of the photoelectric conversion units 12 and 13, and the photoelectric conversion units 12 and 13 are projected forward by the microlens 10. The photoelectric conversion units 12 and 13 are formed on the semiconductor circuit substrate 29. A color filter (not shown) is disposed between the microlens 10 and the photoelectric conversion units 12 and 13.

  A focus detection method by a pupil division type phase difference detection method using a microlens will be described with reference to FIG. In FIG. 5, the exit pupil 90 is set to a distance d in front of the microlens arranged in the vicinity of the planned imaging plane of the interchangeable lens 110.

  In FIG. 5, a pixel (consisting of a microlens 50 and a pair of photoelectric conversion units 52 and 53) on the optical axis 91 of the interchangeable lens 110 and an adjacent pixel (from the microlens 60 and a pair of photoelectric conversion units 62 and 63). In other pixels as well, the pair of photoelectric conversion units receive light beams that arrive at each microlens from a pair of distance measurement pupils. In addition, the arrangement direction of the pixels is matched with the arrangement direction of the pair of distance measuring pupils.

  The microlenses 50 and 60 are disposed in the vicinity of the planned image formation surface of the interchangeable lens 110. The microlens 50 disposed on the optical axis 91 projects the shape of the pair of photoelectric conversion units 52 and 53 disposed behind the microlens 50 onto the exit pupil 90 separated from the microlens 50 by the projection distance d. The shape forms distance measuring pupils 92 and 93. On the other hand, the microlens 60 disposed away from the optical axis 91 projects the shape of the pair of photoelectric conversion units 62 and 63 disposed behind it onto the exit pupil 90 separated from the microlens 60 by the projection distance d. The projection shape forms distance measuring pupils 92 and 93. That is, the projection direction of each pixel is determined so that the projection shape (ranging pupil 92, 93) of the photoelectric conversion unit of each pixel matches on the exit pupil 90 at the projection distance d.

  The photoelectric conversion unit 52 outputs a signal corresponding to the intensity of an image formed on the microlens 50 by the focus detection light beam 72 passing through the distance measuring pupil 92 and directed to the microlens 50. In addition, the photoelectric conversion unit 53 outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 73 passing through the distance measuring pupil 93 and directed toward the microlens 50. On the other hand, the photoelectric conversion unit 62 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 82 that passes through the distance measuring pupil 92 and faces the microlens 60. In addition, the photoelectric conversion unit 63 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 83 that passes through the distance measuring pupil 93 and faces the microlens 60.

  By combining the outputs of the pair of photoelectric conversion units of each pixel into an output group corresponding to the distance measuring pupil 92 and the distance measuring pupil 93, the focus detection light fluxes that pass through each of the distance measuring pupil 92 and the distance measuring pupil 93 are converted into pixel rows. Information on the intensity distribution of the pair of images formed on the top is obtained. By performing a known image shift detection calculation process (correlation calculation process, phase difference detection process) on this information, the image shift amount of a pair of images is detected by a so-called pupil division phase difference detection method. Further, by performing a conversion operation according to the center-of-gravity interval of the pair of distance measuring pupils on the image shift amount, the current imaging plane with respect to the planned imaging plane (the focal point corresponding to the position of the microlens array on the planned imaging plane) The deviation (defocus amount) of the imaging plane at the detection position is calculated. In the above description, the distance measuring pupil has been described as being not limited by the aperture opening. However, the distance measuring pupil actually has a shape and size limited by the aperture opening.

<Generation of focus detection signal>
Next, a method for generating a focus detection signal for focus detection in the above-described pupil division type phase difference method will be described. First, an outline will be described. In the present embodiment, a focus detection signal is generated using an output signal from the G pixel. Since the G pixels are arranged every other pixel in the horizontal direction in the Bayer array, when the focus detection signal is obtained corresponding to only the position of the G pixel, the focus detection signal is obtained every other pixel, and the focus detection accuracy is obtained. Becomes worse. Therefore, in the present embodiment, even when there is no G pixel, the focus detection signal is generated and acquired for each pixel by interpolating from the output of the surrounding G pixels to generate the focus detection signal, thereby improving the focus detection accuracy. Raised. In the present embodiment, a focus detection signal is generated using the output of surrounding G pixels even at a position where the G pixels are present. By doing so, even when a high-frequency component is included in the subject image, focus detection errors due to the high-frequency component can be reduced, and a low-pass filter effect can be obtained in the focus detection signal.

  In other words, the signal values of the discretely arranged G pixels are averaged by using the focus detection signals of the surrounding G pixels, so that the subject image has a contrast such that the signal value changes sharply. Even so, the signal waveforms of the focus detection signal sequence from the first photoelectric conversion unit and the focus detection signal sequence from the second photoelectric conversion unit of the plurality of G pixels are rounded. As a result, it is suppressed that the signal waveform that changes sharply is different between the focus detection signal sequences, so that it is possible to reduce a focus detection error that easily occurs when performing a shift operation between the focus detection signal sequences. It should be noted that for the pixels at discrete positions where no G pixel is provided, the focus detection signal sequence at the pixel position is created using the signal values of the surrounding G pixels, so that the focus detection error is reduced as described above. Can be reduced.

  Hereinafter, generation of such a focus detection signal will be specifically described. Here, as illustrated in FIG. 6, a case where a focus detection signal corresponding to a pixel row L in which pixels P1 to P6 are arranged in the horizontal direction is generated will be described. In the pixel row L, R pixels (P1, P3, P5) and G pixels (P2, P4, P6) are alternately arranged. The body control circuit unit 102 generates a focus detection signal sequence including a plurality of focus detection signals respectively corresponding to the positions of the pixels P1 to P6. When the body control circuit unit 102 generates focus detection signals corresponding to the pixel positions, the body control circuit unit 102 generates focus detection signals a1 to a6 corresponding to the photoelectric conversion unit 12 on the left side in the drawing at the positions of the pixels P1 to P6. And a focus detection signal sequence made up of focus detection signals b1 to b6 corresponding to the photoelectric conversion unit 13 on the right side in the figure. The body control circuit unit 102 generates a focus detection signal corresponding to the position of each of the pixels P1 to P6 using the output signal of the G pixel.

  In FIG. 6, the position of the pixel P1 where the pixel other than the G pixel (here, the R pixel) is arranged, as shown in FIG. 7, is a reference range S1 made up of pixels of 3 rows and 3 columns centered on the pixel P1. And a weight detection signal corresponding to the position of the pixel P1 is obtained by weighting and adding pixel values of four G pixels included in the reference range S1 (that is, four G pixels vertically and horizontally adjacent to the pixel P1). Generate. Similarly, at the positions of the pixels P3 and P5 in which the R pixel is arranged, a reference range composed of pixels of 3 rows and 3 columns with the pixels P3 and P5 as the center is set, and the four G included in each reference range are set. The focus detection signals corresponding to the positions of the pixels P3 and P5 are respectively generated by weighted addition of the pixel values of the pixels. FIG. 8 is a diagram for explaining weighting coefficients when generating focus detection signals corresponding to the positions of pixels other than G pixels. As shown in FIG. 8, the position of the center pixel P is obtained by adding a weighting coefficient of ¼ to the pixel values of four G pixels adjacent to the center pixel P in the reference range S in the vertical and horizontal directions. A focus detection signal corresponding to is generated. The position of the center of gravity of the focus detection signal generated by weighting and adding in this way is the position of the central pixel P in the reference range S.

  As for the position of the pixel P2 where the G pixel is arranged in FIG. 6, as shown in FIG. 9, a reference range S2 composed of pixels of 3 rows and 3 columns centering on the pixel P2 is set, and the reference range S2 A focus detection signal corresponding to the position of the pixel P2 is generated by weighting and adding the pixel values of the five G pixels (G pixel at the four corners and G pixel P2 at the center) included in. Similarly, at the positions of the pixels P4 and P6 where the G pixel is arranged, a reference range composed of pixels of 3 rows and 3 columns with the pixels P4 and P6 as the center is set, and the five G included in each reference range are set. Focus detection signals corresponding to the positions of the pixels P4 and P6 are generated by weighting and adding the pixel values of the pixels. FIG. 10 is a diagram for explaining weighting coefficients when generating a focus detection signal corresponding to the position of such G pixel. As shown in FIG. 10, a weighting coefficient of 1/2 is applied to the pixel value of the central pixel P in the reference range S, and 1/8 is applied to the pixel values of the G pixels at the four corners of the reference range S. To generate a focus detection signal corresponding to the central pixel P. The position of the center of gravity of the focus detection signal generated by weighting and adding in this way is the position of the central pixel P in the reference range S.

  As described above, when the focus detection signal corresponding to the pixel position other than the G pixel is generated, as shown in FIG. 8, in the reference range S, the horizontal end columns (left and right columns) are arranged. Since there is one G pixel each, the weight is 1/4, and since there are two G pixels in the center column, the weight is 1/4 + 1/4 = 1/2. That is, the weighting is a ratio of 1: 2: 1 in the horizontal direction. Similarly, the weighting ratio is 1: 2: 1 in the vertical direction. On the other hand, when the focus detection signal corresponding to the pixel position of the G pixel is generated, as shown in FIG. 10, 1/8 in the horizontal end columns (left and right columns) within the reference range S. Since there are two weighted G pixels each, the weighting is 1/8 + 1/8 = 1/4, and there is one weighted G pixel in the center column, so the weighting is 1 / 2. That is, the weighting is a ratio of 1: 2: 1 in the horizontal direction. Similarly, the weighting ratio is 1: 2: 1 in the vertical direction. As described above, when the focus detection signal corresponding to the pixel position other than the G pixel is generated and when the focus detection signal corresponding to the pixel position of the G pixel is generated, the output signal of the G pixel is added. Is 1: 2: 1 in both the horizontal direction and the vertical direction (that is, the weighting ratio is the same), and the weighting increases toward the center of the reference range. As described above, since the weighting ratio is 1: 2: 1 in the horizontal direction, the focus detection accuracy is improved. Further, in the vertical direction, when the weight ratio is 1: 2: 1, interpolation is performed using pixels closer to the interpolation target pixel, so that the focus detection accuracy is further improved. Note that the weighting is not limited to the ratio of 1: 2: 1 in the horizontal direction and the vertical direction, and the weighting of the ratio of 1: 2: 1 may be performed only in the horizontal direction.

  When the body control circuit unit 102 generates focus detection signals corresponding to the positions of the pixels P1 to P6, the body control circuit unit 102 weights the output of the photoelectric conversion unit 12 positioned on the left side in the drawing of each G pixel included in the reference range. The focus detection signals a1 to a6 are generated by addition, and the focus detection signals b1 to b6 are generated by weighted addition of the outputs of the photoelectric conversion unit 13 located on the right side of each G pixel included in the reference range.

  As described above, when the focus detection signal corresponding to each pixel position is generated by weighted addition of the output signals of the surrounding G pixels, the center of gravity position of each focus detection signal is in the vertical direction, that is, the focus detection direction ( The weighting coefficient is set so as to be the same in the direction perpendicular to the (horizontal direction). Thus, by making the gravity center position of each focus detection signal the same in the vertical direction, errors in focus detection can be reduced and focus detection accuracy can be improved.

  Assuming that the focus detection signals are generated corresponding to the positions of the G pixels arranged in a zigzag pattern in the horizontal direction (that is, the positions in the vertical direction are staggered) as indicated by a thick circle in FIG. 11A. . In FIG. 11A, a region Im indicated by diagonal lines indicates a subject pattern. The edge of the subject pattern covers a part of the position of the G pixel from which the focus detection signal is acquired. An example of acquiring the focus detection signal in this way is shown in the graph of FIG. In this case, as shown in FIG. 11 (b), pixel values vary in G pixels whose vertical positions are staggered, an incorrect subject pattern appears in the focus detection signal, and a focus detection error occurs. End up. As described above, if the gravity center positions of the focus detection signals are not aligned in the direction perpendicular to the focus detection direction (here, the horizontal direction), that is, if they are not aligned in the focus detection direction, focus detection errors may occur.

  On the other hand, as shown by a thick circle in FIG. 12A, the subject pattern is arranged as shown in FIG. 12B by aligning the gravity center positions of the focus detection signals in the vertical direction, that is, in the focus detection direction. A focus detection signal that correctly reflects Im can be obtained, and focus detection accuracy can be improved.

  As described above, the body control circuit unit 102 generates a focus detection signal corresponding to each pixel position by weighted addition of the output signals of a plurality of G pixels located around each pixel position. Then, the body control circuit unit 102 performs known image shift detection calculation processing (correlation calculation processing, phase difference detection processing) based on the generated focus detection signal to detect the image shift amount, and based on the image shift amount. The defocus amount (the focus adjustment state of the interchangeable lens 110) is detected.

<Imaging operation>
FIG. 13 is a flowchart illustrating the flow of the imaging operation of the digital camera. The body control circuit unit 102 starts this imaging operation when the power of the digital camera is turned on.

  In step S101, the body control circuit unit 102 causes the image sensor 101 to start a periodic operation. In step S <b> 102, the body control circuit unit 102 reads an output signal from the image sensor 101. In step S103, the body control circuit unit 102 generates a focus detection signal corresponding to the set focus detection area based on the output signal of the image sensor 101 read in step S102. At this time, as described above, the body control circuit unit 102 generates a focus detection signal corresponding to each pixel position by weighting and adding the output signals of the G pixels.

  In step S104, the body control circuit unit 102 calculates the defocus amount based on the focus detection signal generated in step S103. In step S105, the body control circuit unit 102 determines whether or not the defocus amount calculated in step S104 is within a predetermined value, that is, whether it is in focus. If the body control circuit unit 102 determines that it is not in focus, the process proceeds to step 106, transmits the defocus amount to the lens control circuit unit 111, and drives the focus lens 113 of the interchangeable lens 110 to the in-focus position. Returning to step 102, the above-described operation is repeated.

  On the other hand, if it is determined that the subject is in focus, the body control circuit unit 102 proceeds to step 107 to determine whether or not a shutter release has been performed by operating a release button (not shown). If it is determined, the process returns to step 102 and the above-described operation is repeated.

  If it is determined that the shutter release has been performed, the body control circuit unit 102 proceeds to step 108, acquires captured image data based on the output signal from the image sensor 101, stores it in the memory card 207, and then proceeds to step 101. Return and repeat the above operation. As described above, the body control circuit unit 102 adds the output signals from the pair of photoelectric conversion units 12 and 13 in each pixel 311 of the image sensor 101 to obtain an image signal having a Bayer array. The body control circuit unit 102 obtains captured image data by performing a known Bayer interpolation process on the image signals in the Bayer array.

According to the first embodiment described above, the following operational effects are obtained.
(1) In the digital camera, the body control circuit unit 102 uses the focus detection signal corresponding to a pixel position other than the G pixel (the position of the R pixel or the position of the B pixel) (that is, the pixel position other than the G pixel as the center of gravity position). A focus detection signal is generated by weighted addition of output signals of a plurality of G pixels located around the position. Thereby, the focus detection signal is generated and acquired for each pixel, and the focus detection accuracy can be improved.

(2) In the digital camera, the body control circuit unit 102 also generates a focus detection signal corresponding to a certain position of the G pixel by weighted addition of the output signals of a plurality of G pixels located around the position. Thereby, a low-pass filter effect can be obtained in the focus detection signal.

(3) In the digital camera, the body control circuit unit 102 determines that the focus detection signal corresponding to each pixel position is in the horizontal direction (the alignment direction of the pair of photoelectric conversion units 12 and 13, that is, the focus detection). Generated in a direction perpendicular to (direction), that is, aligned in the focus detection direction. Thereby, focus detection accuracy can be improved.

(4) In the digital camera, when the body control circuit unit 102 generates a focus detection signal corresponding to each pixel position, the size of the reference range is the same. In the present embodiment, the focus detection signal is generated using the output signal of the G pixel included in the reference range including the pixels in 3 rows and 3 columns at any pixel position. Thereby, focus detection accuracy can be improved.

-Second Embodiment-
Next, a second embodiment of the present invention will be described. In the second embodiment, the configuration of the digital camera and the image sensor 101 (FIGS. 1 to 5) is the same as that of the first embodiment, and a description thereof will be omitted.

  FIG. 14 is a flowchart illustrating the flow of the imaging operation of the digital camera. The body control circuit unit 102 starts this imaging operation when the power of the digital camera is turned on.

  In step S201, the body control circuit unit 102 causes the image sensor 101 to start a periodic operation. In step S <b> 202, the body control circuit unit 102 reads an output signal from the image sensor 101.

  In step S203, the body control circuit unit 102 generates a focus detection signal corresponding to the set focus detection area based on the output signal of the image sensor 101 read in step S202. At this time, as in the first embodiment, the body control circuit unit 102 generates a focus detection signal corresponding to each pixel position by weighted addition of the output signals of the G pixels. In the first embodiment, an example in which the reference range when generating a focus detection signal is composed of pixels of 3 rows and 3 columns has been described, but in the second embodiment, the reference range is 6 rows and 6 columns. A case of pixels will be described. In this case, for example, as shown in FIG. 15, a reference range S11 composed of pixels of 6 rows and 6 columns is set, and the pixel values of 18 G pixels included in the reference range S11 are weighted and added, thereby obtaining the reference range. A focus detection signal corresponding to the center position C11 of S11 (that is, the center of gravity position is the center position C11) is generated. As described above, the position of the center of gravity of the focus detection signal does not necessarily have to be a pixel arrangement position, and may be a position between pixels.

  The body control circuit unit 102 sets a plurality of reference ranges composed of such pixels of 6 rows and 6 columns by shifting one pixel at a time in the horizontal direction, and outputs a plurality of focus detection signals respectively corresponding to the center positions of the plurality of reference ranges. , Using the output signals of a plurality of G pixels included in each reference range. Since the center position of the reference range is the centroid position of each focus detection signal, the centroid position of each focus detection signal is continuous at the pixel pitch in the horizontal direction and is the same position in the vertical direction.

  In step S204, the body control circuit unit 102 determines whether or not a focus detection signal sequence including a plurality of focus detection signals generated in step S203 satisfies a predetermined condition. Here, the predetermined condition is a condition for determining whether or not a focus detection signal sequence suitable for focus detection is obtained. For example, the contrast amount of the focus detection signal sequence generated in step S203. Is equal to or greater than a predetermined value, or whether the difference between the maximum value and the minimum value of the focus detection signal sequence is equal to or greater than a predetermined value. When such a condition is not satisfied, it is considered that the signal level of the focus detection signal is not sufficient and is not suitable for calculating the image shift amount.

  When the focus detection signal sequence generated in step S203 satisfies a predetermined condition, that is, when the focus detection signal sequence generated using the output signal of the G pixel is appropriate for performing focus detection, the body control circuit unit 102 Makes an affirmative decision in step S204 and proceeds to step S205. In step S205, the body control circuit unit 102 calculates the defocus amount based on the focus detection signal sequence generated in step S203 (that is, generated using the output signal of the G pixel).

  On the other hand, if the focus detection signal generated in step S203 does not satisfy the predetermined condition, that is, if the focus detection signal generated using the output signal of the G pixel is not appropriate for focus detection, the body control circuit unit 102 makes a negative determination in step S204 to proceed to step S206.

  In step S206, the body control circuit unit 102 generates a focus detection signal sequence using the output signal of the R pixel and a focus detection signal sequence using the output signal of the B pixel. At this time, these focus detection signal sequences are generated so that the position of the center of gravity is the same as the focus detection signal sequence generated in step S203 (that is, using the output signal of the G pixel). For example, when the focus detection signal corresponding to the center position C11 shown in FIG. 15 is generated using the output signal of the R pixel, as shown in FIG. 16, the same 6 × 6 pixels as in the case of the G pixel A reference range S11 consisting of Then, a focus detection signal corresponding to the position of the center position C11 (that is, the center of gravity position becomes the center position C11) is generated by weighting and adding the pixel values of the nine R pixels included in the reference range S11. Similarly, when the focus detection signal corresponding to the center position C11 shown in FIG. 15 is generated using the output signal of the B pixel, as shown in FIG. 17, the same 6 rows and 6 columns as in the case of the G pixel are used. A reference range S11 composed of pixels is set. Then, the focus detection signal corresponding to the center position C11 (that is, the center of gravity position becomes the center position C11) is generated by weighting and adding the pixel values of the nine B pixels included in the reference range S11. In this way, the focus detection signal sequence by the R pixel and the focus detection signal sequence by the B pixel are generated so that the center of gravity position is the same as the focus detection signal sequence by the G pixel.

  In step S207, the body control circuit unit 102 adds the focus detection signal sequence based on the G pixel generated in step S203 and the focus detection signal sequence based on the R pixel and the focus detection signal sequence based on the B pixel generated in step S206. A detection signal train is generated. In addition, when adding, the focus detection signals of the same gravity center position are added together. Further, the focus detection signals corresponding to the photoelectric conversion unit 12 and the focus detection signals corresponding to the photoelectric conversion unit 13 are added. In this way, by adding the focus detection signal sequence of the R pixel and the B pixel to the focus detection signal sequence of the G pixel, the signal level of the focus detection signal sequence is increased, and the focus detection signal suitable for calculating the image shift amount A column can be generated.

  In step S208, the body control circuit unit 102 is based on the focus detection signal sequence generated in step S207 (that is, generated by adding the focus detection signal sequence of R pixels and B pixels to the focus detection signal sequence of G pixels). Calculate the defocus amount.

  Since the operations in steps S209 to S212 are the same as those in steps S105 to S108 in the first embodiment described above, description thereof will be omitted.

  In the above description, the example in which both the focus detection signal sequence by the R pixel and the focus detection signal sequence by the B pixel are added to the focus detection signal sequence by the G pixel has been described, but either one is added. You may do it. Further, in the second embodiment, the case where the centroid position of the focus detection signal is a position between the pixels has been described. However, as in the first embodiment, the centroid position of the focus detection signal is the position of the pixel. In the case of the position, the process of FIG. 14 may be performed.

According to the second embodiment described above, the following operational effects can be obtained.
The body control circuit unit 102 determines whether or not the focus detection signal sequence generated using the output signal of the G pixel satisfies the predetermined condition. If the predetermined condition is not satisfied, a focus detection signal sequence using the output signal of the R pixel and a focus detection signal sequence using the output signal of the B pixel are generated. It adds to the focus detection signal sequence using the output signal of the pixel. Then, the focus adjustment state of the interchangeable lens 110 is detected using the focus detection signal sequence generated by the addition. As described above, when the focus detection signal sequence generated using the output signal of the G pixel is not appropriate for focus detection, the output signals of the R pixel and the B pixel are added to generate the focus detection signal sequence. By doing so, focus detection can be performed appropriately.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

(Modification 1)
In the above-described embodiment, the example in which the two photoelectric conversion units 12 and 13 are arranged in the horizontal direction in each pixel 311 and focus detection is performed in the horizontal direction has been described. However, the direction in which focus detection is performed may be a vertical direction or an oblique direction, and the photoelectric conversion unit may be arranged corresponding to the focus detection direction.

(Modification 2)
In the above-described embodiment, the example in which the two photoelectric conversion units 12 and 13 are provided in each pixel 311 has been described. However, the number of photoelectric conversion units in each pixel is not limited to two. Four photoelectric conversion units may be provided.

(Modification 3)
In the above-described embodiment, the example in which the size of the reference range when generating the focus detection signal is composed of pixels of 3 rows and 3 columns or 6 rows and 6 columns has been described. You may make it consist of a pixel of 4 rows 4 columns or 5 rows 5 columns.

(Modification 4)
In the embodiment described above, the example in which the focus detection signal is generated so that the position of the center of gravity of the focus detection signal becomes the center position of the reference range has been described, but other positions may be used. It is only necessary that the positions are aligned in each reference range. Further, the gravity center position of the focus detection signal may coincide with a specific pixel position as in the first embodiment, and the gravity center position of the focus detection signal is the pixel as in the second embodiment. And a position between the pixel and the pixel.

(Modification 5)
In the above-described embodiment, an example in which the focus detection pixels 311 are provided over the entire imaging surface has been described as an example of the imaging element 101. However, in the image sensor 101, the focus detection pixels 311 are arranged only at positions corresponding to the AF areas, and normal pixels (pixels each provided with one photoelectric conversion unit) are arranged at other positions. May be.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Camera body, 101 ... Image pick-up element, 102 ... Body control circuit part, 103 ... Body operation part, 104 ... Display part, 110 ... Interchangeable lens, 113 ... Focus lens, 202 ... A / D conversion part, 203 ... CPU, 204 ... Image sensor driving circuit, 205 ... Image processing circuit, 206 ... Focus detection calculation circuit, 210 ... Communication unit

Claims (10)

A first pixel that includes first and second photoelectric conversion units that receive first and second light fluxes that have passed through different pupil regions of the imaging optical system, and that generates a signal based on light of the first color; Image sensors in which second pixels that generate a signal of light of the second color are alternately arranged in a predetermined direction;
A focus detection signal is generated using a signal from the first photoelectric conversion unit in the plurality of first pixels and a signal from the second photoelectric conversion unit in the plurality of first pixels, and the focus detection signal A focus detection unit for detecting the focus of the photographing optical system based on
With
The focus detection unit is configured to generate a focus detection signal at the position of the second pixel in the focus detection signal using signals of the plurality of first pixels located around the second pixel. The imaging device according to claim 1,
The focus detection unit includes a focus detection signal at the position of the first pixel among the focus detection signals, a signal of the first pixel, and signals of a plurality of the first pixels located around the first pixel. An imaging device to be generated using. The imaging device according to claim 1 or 2,
The focus detection unit generates a focus detection signal at the position of the second pixel among the focus detection signals by weighted addition of the signals of the plurality of first pixels located around the second pixel. apparatus. The imaging device according to claim 2,
The focus detection unit includes a focus detection signal at the position of the first pixel among the focus detection signals, a signal of the first pixel, and signals of a plurality of the first pixels positioned around the first pixel. An imaging device generated by weighted addition. In the imaging device according to any one of claims 1 to 4,
The focus detection unit generates focus detection signals at the positions of the first pixels and the second pixels that are alternately arranged in a predetermined direction so that the gravity center positions of the focus detection signals are aligned in the predetermined direction. An imaging device. In the imaging device according to any one of claims 1 to 5,
In the imaging device, the focus detection unit sets m and n to integers of 2 or more, and sets a plurality of reference ranges including pixels in m rows and n columns so as to include each pixel position in the pixel column, When generating a plurality of focus detection signals corresponding to each pixel position of the pixel column by weighting and adding the signals of the plurality of first pixels included in each reference range. An imaging apparatus in which the size of each reference range is the same. The imaging device according to claim 6,
The focus detection unit, when generating the plurality of focus detection signals, weights and adds the signal of the first pixel so that the weight is increased toward the center of the reference range in the horizontal direction and the vertical direction. In the imaging device according to any one of claims 1 to 6,
The focus detection unit generates a first focus detection signal sequence including a plurality of focus detection signals corresponding to the respective pixel positions of the pixel sequence, using the signal from the first pixel. Second focus detection signal generation for generating a second focus detection signal sequence composed of a plurality of focus detection signals respectively corresponding to each pixel position of the pixel column, using a generation unit and a signal from the second pixel A first focus detection signal sequence and the second focus detection signal sequence are added to generate a third focus detection signal sequence, and the first focus detection signal sequence has a predetermined condition A determination unit that determines whether or not
The focus detection unit includes the first focus detection signal sequence and the second focus detection signal sequence, a barycentric position of a plurality of focus detection signals constituting the first focus detection signal sequence, and the second focus detection signal sequence. Generate a plurality of focus detection signals constituting the focus detection signal sequence so that the center of gravity positions are the same,
When the first focus detection signal sequence satisfies a predetermined condition, the focus detection unit detects a focus adjustment state of the photographing optical system based on the first focus detection signal sequence, and An imaging apparatus that detects a focus adjustment state of the photographing optical system based on the third focus detection signal sequence when one focus detection signal sequence does not satisfy a predetermined condition. A first pixel that includes first and second photoelectric conversion units that receive first and second light fluxes that have passed through different pupil regions of the imaging optical system, and that generates a signal based on light of the first color; Image sensors in which second pixels that generate a signal of light of the second color are alternately arranged in a predetermined direction;
A focus detection signal is generated using a signal from the first photoelectric conversion unit in the plurality of first pixels and a signal from the second photoelectric conversion unit in the plurality of first pixels, and the focus detection signal A focus detection unit for detecting the focus of the photographing optical system based on
With
In the imaging device, the focus detection unit sets m and n to integers of 2 or more, sets a plurality of reference ranges including pixels in m rows and n columns by shifting one pixel at a time in the predetermined direction, and sets a plurality of reference ranges. A plurality of focus detection signals corresponding to each of the plurality of focus detection signals are generated using signals of the plurality of first pixels included in each reference range. An imaging device that generates the images so as to line up in the predetermined direction. A first pixel that includes first and second photoelectric conversion units that receive first and second light fluxes that have passed through different pupil regions of the imaging optical system, and that generates a signal based on light of the first color; Image sensors in which second pixels that generate a signal of light of the second color are alternately arranged in a predetermined direction;
A focus detection signal is generated using a signal from the first photoelectric conversion unit in the plurality of first pixels and a signal from the second photoelectric conversion unit in the plurality of first pixels, and the focus detection signal A focus detection unit for detecting the focus of the photographing optical system based on
With
The focus detection unit outputs a focus detection signal at the position of the first pixel in the focus detection signal, a signal of the first pixel, and signals of the plurality of first pixels located around the first pixel. An imaging device to be generated using.

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