JP5792349B2 - IMAGING DEVICE AND IMAGING DEVICE CONTROL METHOD - Google Patents

Description

  The present invention relates to an imaging apparatus that detects a focus state by using a part of pixels as a phase difference detection element of a phase difference method, and a control method thereof.

  For example, Patent Document 1 discloses a proposal relating to an imaging apparatus that detects a focus state by using a part of pixels of an imaging element as a phase difference detection element. In Patent Document 1, a part of pixels of an image sensor is set as a phase difference detection pixel, and a subject light flux that has passed through a different pupil region symmetric with respect to the optical axis center of the photographing lens is formed on a plurality of phase difference detection pixels. The focus state of the photographing lens is detected by detecting the phase difference between the subject light fluxes.

  Here, in the phase difference detection pixel, for example, a part of the region is shielded from light so that one of the subject light fluxes passing through different pupil regions of the photographing lens can be received. For this reason, the phase difference detection pixel becomes a defective pixel that cannot be used as an image as it is. Therefore, in Patent Document 1, the output signal of the phase difference detection pixel is subjected to interpolation processing using the output signal of the surrounding same color pixel. However, if such an interpolation process is performed on a subject having a high spatial frequency, the sharpness of the image is lowered. Therefore, the imaging device disclosed in Patent Document 2 detects signal variations (spatial frequency) of pixels around the phase difference detection pixel, and determines the ratio between the gain adjustment amount and the interpolation correction amount based on the detection result. Like to do.

Japanese Patent No. 3592147 JP 2010-062640 A

  In Patent Document 2 described above, the ratio between the gain adjustment amount and the interpolation correction amount is changed according to variations in output signals of pixels around the phase difference detection pixel. Here, if the ratio of the correction amount is changed with uniform judgment for each phase difference detection pixel, overcorrection may occur depending on the method of signal readout from the image sensor, and image quality may be deteriorated more than when correction is not performed. is there.

  The present invention has been made in view of the above circumstances, and in an imaging apparatus including an imaging element having a phase difference detection pixel, an imaging apparatus capable of suppressing deterioration in image quality due to the phase difference detection pixel and a control method thereof The purpose is to provide.

In order to achieve the above object, an imaging device according to a first aspect of the present invention includes an imaging device in which a phase difference detection pixel for focus detection is arranged at a partial position of the imaging pixel, and the imaging device. A reading method setting unit that sets a reading method when reading pixel data from the imaging pixel and the phase difference detection pixel, and an image processing unit that corrects the pixel data of the phase difference detection pixel. The processing unit includes: a gain adjusting unit that adjusts the gain of the pixel data of the phase difference detection pixel read according to the reading method set by the reading method setting unit; and the gain-adjusted phase difference detection pixel A pixel interpolation unit that weights and adds pixel data and pixel data of imaging pixels around the phase difference detection pixel, and the reading method set by the reading method setting unit An interpolation ratio determining unit that determines a weighting coefficient at the time of add-adding, and the interpolation ratio determining unit is configured when the readout method set by the readout method setting unit is a method of mixing a plurality of pixels. Is the mixing rate determined by the arrangement of the phase difference detection pixels included in the pixel to be mixed, and the pixel data of the phase difference detection pixel in the pixel data read out according to the readout method is high. As it is , the weighting coefficient of the pixel data of the phase difference detection pixel whose gain has been adjusted is reduced, or the weighting coefficient of the pixel data of the imaging pixels around the phase difference detection pixel is increased .

In order to achieve the above-described object, the imaging apparatus control method according to the second aspect of the present invention provides imaging of an imaging device in which phase difference detection pixels for focus detection are arranged at some positions of the imaging device. A readout method for reading out pixel data from the pixel and the phase difference detection pixel is set, and the gain adjustment of the pixel data of the phase difference detection pixel read out according to the set readout method is performed, and the gain adjustment is performed. When the pixel data of the detected phase difference detection pixel and the pixel data of the imaging pixels around the phase difference detection pixel are weighted and added, and the weighting coefficient for the weighted addition is determined according to the set readout method In addition, when the set readout method is a method of mixing a plurality of pixels, the mixing rate determined by the arrangement of the phase difference detection pixels included in the pixels to be mixed is Higher mixing rate of the pixel data of the phase difference detection pixels in the pixel data read out in response to a read mode is high, to reduce the weighting factor of the pixel data of the gain-adjusted phase difference detection pixel, or the position The weighting coefficient of the pixel data of the imaging pixels around the phase difference detection pixel is increased .

  ADVANTAGE OF THE INVENTION According to this invention, in the imaging device provided with the imaging device which has a phase difference detection pixel, the imaging device which can suppress the fall of the image quality by a phase difference detection pixel, and its control method can be provided.

1 is a block diagram illustrating a configuration of a digital camera as an example of an imaging apparatus according to an embodiment of the present invention. It is a figure which shows the detailed structure of an imaging control circuit and an image process part. It is the figure which showed the pixel arrangement | sequence of an image pick-up element. FIG. 4A is a diagram illustrating the image formation state of the image in the imaging pixel, and FIG. 4B is a diagram illustrating the image formation state of the image in the phase difference detection pixel. It is a flowchart which shows the process of the moving image recording operation | movement by an imaging device. FIG. 6A is a diagram showing a pixel arrangement before 2 × 2 pixel mixed readout, and FIG. 6B is a diagram showing a pixel arrangement after 2 × 2 pixel mixed readout. FIG. 7A is a diagram showing a pixel arrangement before 3 × 3 pixel mixed readout, and FIG. 7B is a diagram showing a pixel arrangement after 3 × 3 pixel mixed readout. It is a flowchart which shows a pixel interpolation process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a digital camera (hereinafter simply referred to as a camera) as an example of an imaging apparatus according to an embodiment of the present invention. Here, in FIG. 1, a solid line with an arrow indicates a data flow, and a broken line with an arrow indicates a control signal flow.

  A camera 1 shown in FIG. 1 includes a photographing lens 11, a diaphragm 13, a mechanical shutter 15, a drive unit 17, an operation unit 19, an image sensor 21, an imaging control circuit 23, an A-AMP 25, and analog-digital conversion. Unit (ADC) 27, CPU (Central Processing Unit) 29, image processing unit 31, focus detection circuit 33, video encoder 35, display unit 37, bus 39, DRAM (Dynamic Random Access Memory) 41 And a ROM (Read Only Memory) 43 and a recording medium 45.

  The photographing lens 11 is composed of a single lens or a plurality of lenses for forming an image from the subject 100 on the image sensor 21. The taking lens 11 may be a single focus lens or a zoom lens.

  The aperture 13 is disposed on the optical axis of the photographic lens 11, and its aperture is variable. The diaphragm 13 limits the amount of light flux from the subject 100 that has passed through the photographing lens 11.

  The mechanical shutter 15 is disposed behind the diaphragm 13 and is configured to be freely opened and closed. The mechanical shutter 15 adjusts the incident time of the subject luminous flux from the subject 100 to the image sensor 21 (exposure time of the image sensor 21) by adjusting the opening time. As the mechanical shutter 15, a known focal plane shutter, lens shutter, or the like can be employed.

  Based on a control signal from the CPU 29, the driving unit 17 performs focus adjustment of the photographing lens 11, aperture diameter control of the diaphragm 13, and opening / closing control of the mechanical shutter 15.

  The operation unit 19 includes various operation buttons such as a power button, a release button, a reproduction button, and a menu button, and various operation members such as a touch panel. The operation unit 19 detects operation states of various operation members and outputs a signal indicating the detection result to the CPU 29. Here, the shooting mode of the camera 1 can be selected by the operation unit 19 of the present embodiment. That is, the user can select the shooting mode of the camera 1 from either the still image shooting mode or the moving image shooting mode by operating a shooting mode dial as an operation member included in the operation unit 19. The still image shooting mode is a shooting mode for shooting a still image, and the moving image shooting mode is a shooting mode for shooting a moving image. Here, an example of selecting with a dial is shown, but for example, a shooting mode may be selected by operating, for example, a touch panel on a menu screen.

  The imaging element 21 is disposed on the optical axis of the photographing lens 11, behind the mechanical shutter 15, and at a position where the subject light beam is imaged by the photographing lens 11. The image sensor 21 is configured by two-dimensionally arranging photodiodes that constitute pixels. Here, the image sensor 21 in the present embodiment includes an image pickup pixel for acquiring an image for recording and display and a phase difference detection pixel for focus detection.

  The photodiode that constitutes the image sensor 21 generates a charge corresponding to the amount of received light. The electric charge generated in the photodiode is accumulated in a capacitor connected to each photodiode. The electric charge accumulated in this capacitor is read out as an image signal.

  Here, the image sensor 21 in the present embodiment has a plurality of different charge readout methods. The charge accumulated in the image sensor 21 is read according to a control signal from the image capture control circuit 23.

Also, for example, a Bayer array color filter is disposed on the front surface of the photodiode constituting the pixel. The Bayer array has a line in which R pixels and G (Gr) pixels are alternately arranged in the horizontal direction, and a line in which G (Gb) pixels and B pixels are alternately arranged.
In the present embodiment, the phase difference detection pixels are arranged at some positions of the imaging pixels. Unlike other pixels, pixels used as phase difference detection pixels shield light from a part of the region. Details of the image sensor 21 will be described later.

  The imaging control circuit 23 sets the readout method of the imaging element 21 according to the control signal from the CPU 29, and controls the readout of the image signal from the imaging element 21 according to the set readout method. Details of the imaging control circuit 23 will be described later in detail.

  The A-AMP 25 performs analog gain adjustment of the image signal output from the image sensor 21.

  The ADC 27 is an analog-digital converter, and converts the image signal whose analog gain has been adjusted by the A-AMP 25 into a digital image signal (pixel data). Hereinafter, a collection of a plurality of pixel data is referred to as imaging data in this specification.

  The CPU 29 performs overall control of the camera 1 according to a program stored in the ROM 43 described later.

  The image processing unit 31 performs various types of image processing on the captured data to generate image data. For example, when recording a still image, the image processing unit 31 performs still image recording image processing to generate still image data. Similarly, when recording a moving image, the image processing unit 31 performs moving image recording image processing to generate moving image data. Furthermore, the image processing unit 31 performs display image processing during live view display to generate display image data. The detailed configuration of the image processing unit 31 will be described in detail later.

  The focus detection circuit 33 acquires pixel data from the phase difference detection pixel, and calculates a defocus direction and a defocus amount with respect to the in-focus position of the photographing lens 11 using a known phase difference method based on the acquired pixel data. To do.

  The video encoder 35 reads the display image data generated by the image processing unit 31 and temporarily stored in the DRAM 41, and outputs the read display image data to the display unit 37.

  The display unit 37 is a display unit such as a liquid crystal display or an organic EL display, and is disposed on the back surface of the camera 1, for example. The display unit 37 displays an image according to the display image data input from the video encoder 35. The display unit 37 is used for live view display, display of recorded images, and the like.

  The bus 39 is connected to the ADC 27, the CPU 29, the image processing unit 31, the focus detection circuit 33, the video encoder 35, the DRAM 41, the ROM 43, and the recording medium 45, and various data generated in these blocks are transferred.

  The DRAM 41 is an electrically rewritable memory, and temporarily stores various data such as the above-described imaging data (pixel data), recording image data, display image data, and processing data in the CPU 29. Note that an SDRAM (Synchronous Dynamic Random Access Memory) may be used for temporary storage.

  The ROM 43 is a non-volatile memory such as a mask ROM or a flash memory. The ROM 43 stores various data such as a program used by the CPU 29 and adjustment values of the camera 1.

  The recording medium 45 is configured to be built in or freely loaded in the camera 1 and records recording image data as an image file of a predetermined format.

  FIG. 2 is a diagram illustrating a detailed configuration of the imaging control circuit 23 and the image processing unit 31. In FIG. 2, illustrations of blocks other than the imaging control circuit 23 and the image processing unit 31 are omitted. Here, in FIG. 2, a solid line with an arrow indicates a flow of imaging data (pixel data). A broken line with an arrow indicates a flow of setting data for the imaging control circuit 23, an alternate long and short dash line with an arrow indicates a flow of RGB data (a result of simultaneous processing of imaging data), and a two-dot chain line with an arrow indicates YC data ( The flow of RGB data) is represented respectively. RGB data or YC data corresponds to the image data described above.

  Various settings are made in the image pickup control circuit 23 in accordance with a method for reading out pixel data from the image pickup device 21, and a control signal for reading out pixel data from the image pickup device 21 is sent to the image pickup device 21 in accordance with this setting. Output.

  The imaging control circuit 23 includes a readout method setting unit 231 and a mixing rate setting unit 232.

  The readout method setting unit 231 sets the readout method of pixel data from the image sensor 21 according to the setting data from the CPU 29. The readout method is set according to the operating state of the camera 1. For example, when real-time performance is required for reading pixel data from the image sensor 21 (for example, during live view display or moving image recording), pixel data from a plurality of pixels of the same color is used so that the pixel data can be read at high speed. Are read out, or the pixel data of a specific pixel is read out. On the other hand, when image quality is required rather than real-time characteristics (for example, when recording a still image), resolution is maintained by reading pixel data of all pixels without performing mixed readout or thinning readout. The CPU 29 determines the operating state of the camera 1 and generates setting data so that a reading method according to the determined result is obtained.

  The mixing rate setting unit 232 sets horizontal and vertical pixel reading intervals when mixing pixel data or thinning out pixel data. For example, a readout method (2 × 2 pixel mixed readout) in which a total of 4 pixels are mixed by 2 horizontal and vertical 2 pixels to 1 pixel, or a total of 4 pixels of 2 horizontal and 2 vertical pixels are thinned to 1 pixel. When the readout method (2 × 2 pixel thinning readout) is set in the readout method setting unit 231, 2 is set for each of the horizontal readout interval and the vertical readout interval.

  The image processing unit 31 includes a gain adjustment unit 311, an interpolation ratio determination unit 312, a pixel interpolation unit 313, a development processing unit 314, and a color conversion processing unit 315. In addition, although not shown, the image processing unit 31 also includes a compression / decompression processing unit and the like.

  The gain adjustment unit 311 performs gain adjustment of pixel data from the phase difference detection pixel. The phase difference detection pixel blocks a part of the area. For this reason, even in the case of imaging a part having the same luminance of the subject, the light amount of the phase difference detection pixel is smaller than that of the imaging pixel. The gain adjustment unit 311 performs correction to compensate for the dimming of pixel data that occurs by blocking a partial region of the phase difference detection pixel.

  The interpolation ratio determination unit 312 determines the pixel data of the phase difference detection pixel from the mixing rate calculated according to the reading method set in the reading method setting unit 231 and the horizontal / vertical reading interval set in the mixing rate setting unit 232. Determine the application rate. The application ratio is a weighting coefficient for weighted addition of the pixel data of the phase difference detection pixel subjected to gain adjustment processing and the pixel data around the phase difference detection pixel. Specifically, in the case of a readout method in which the pixel data mixture rate of the phase difference detection pixel is high, the pixel data of the phase difference detection pixel that has been subjected to gain adjustment processing by increasing the weighting coefficient of the pixel data of the peripheral pixels. Reduce the weighting coefficient.

  The pixel interpolation unit 313 performs a correction process on the pixel data of the phase difference detection pixel based on the application ratio (weighting coefficient) determined by the interpolation ratio determination unit 312.

  The development processing unit 314 performs synchronization processing (demosaicing processing), NR (Noise Reduction) processing, WB (White Balance) correction, edge enhancement processing, and the like on the imaging data including the pixel data interpolated by the pixel interpolation unit 313. Apply. In the imaging data output from the imaging device 21 provided with a Bayer array color filter, one pixel data corresponds to one color component. Such imaging data is converted into RGB data in which one pixel data has three components of RGB by a synchronization process.

  The color conversion processing unit 315 performs processing for generating display image data or recording image data from the RGB data obtained by the development processing unit 314. This processing includes, for example, processing for converting RGB data into YC data by matrix calculation, gamma correction processing for YC data, and the like.

  The configuration of the image sensor 21 will be described with reference to FIG. FIG. 3 is a diagram illustrating a pixel array of the image sensor 21. In addition, on the right side of FIG. 3, a part of the pixels is shown in an enlarged manner. FIG. 3 shows an example of the Bayer arrangement, but the arrangement of the color filters is not limited to the Bayer arrangement, and various arrangements can be applied.

  As described above, the Bayer array image sensor 21 has a line in which R pixels and G (Gr) pixels are alternately arranged in the horizontal direction and a line in which G (Gb) pixels and B pixels are alternately arranged. doing. In other words, in the Bayer array image sensor 21, a set of four pixels of the Gr pixel, the R pixel, the Gb pixel, and the B pixel shown in the enlarged view on the right side is repeatedly arranged in the horizontal and vertical directions.

  In the present embodiment, phase difference detection pixels are arranged at the positions of some imaging pixels. The phase difference detection pixel is, for example, a pixel in which one of the left and right regions is shielded by a light shielding film. In the example of FIG. 3, a row of phase difference detection pixels (hereinafter referred to as right opening phase difference detection pixels) in which the left half surface is shielded and a phase difference detection pixel (hereinafter referred to as left opening phase difference detection pixels) in which the right half surface is shielded. Are arranged close to each other along the vertical direction.

  In the case of an image sensor with a large number of pixels, the area of each pixel is small, so it can be considered that the same image is formed on pixels arranged close to each other. Therefore, as shown in FIG. By arranging the detection pixels, the phase difference can be detected by a pair of the phase difference detection pixels in the A row and the phase difference detection pixels in the B row in FIG. The phase difference can also be detected by a pair of phase difference detection pixels in the C row and phase difference detection pixels in the D row.

  Here, in the example of FIG. 3, the light shielding region in the phase difference detection pixel is set to either the left or right region. In this case, it is possible to detect the horizontal phase difference. On the other hand, it is also possible to detect a vertical phase difference or a phase difference in an oblique direction by setting a light shielding region as an upper or lower region or an oblique region. Further, as long as it has a certain area, the light shielding area may not be 1/2 of the pixel region. Further, in FIG. 3, the phase difference detection pixel is arranged in the G pixel, but it may be arranged in any of the R pixel and the B pixel other than the G pixel.

  The example of FIG. 3 shows an example in which pupil division is performed by shielding a partial area of the phase difference detection pixel 21b, but the phase difference detection pixel is a pair of pixels that have passed through different pupil areas of the photographing lens 11. It is only necessary to selectively receive one of the subject luminous fluxes forming For this reason, instead of a configuration in which a partial region is shielded from light, for example, pupil division may be performed by a pupil division microlens.

  The principle of focus detection by the phase difference method using the image sensor as shown in FIG. 3 will be described with reference to FIG. Here, FIG. 4A shows the image formation state of the image in the imaging pixel 21a. FIG. 4B shows the image formation state of the phase difference detection pixel 21b.

  Assuming that the subject is a point light source, when the photographing lens 11 is in a focused state, a pair of subject light beams emitted from the subject and passing through different pupil regions symmetric with respect to the optical axis center of the photographing lens 11 are imaged. An image is formed at the same position on the element 21.

  When viewed in the horizontal direction, the peak position of the image formed on the imaging pixel 21a matches the peak position of the image formed on the phase difference detection pixel 21b. However, since a part of the region of the phase difference detection pixel 21b is shielded from light, only the peak of one image of a pair of subject light beams is detected. For this reason, a decrease in the amount of light occurs in the phase difference detection pixel 21b.

  On the other hand, when the photographing lens 11 is out of focus, a pair of subject luminous fluxes emitted from the subject and passing through different pupil regions of the photographing lens 11 are imaged at different positions on the image sensor 21. In other words, there is a phase difference between images formed by these pairs of subject light fluxes. By detecting this phase difference from the correlation between the images detected by the right aperture phase difference detection pixel and the left aperture phase difference detection pixel, the defocus amount and the defocus direction of the photographing lens 11 are detected.

  When viewed in the horizontal direction, an image corresponding to each of the subject luminous fluxes that have passed through different pupil regions is formed on the imaging pixel 21a. On the other hand, only an image corresponding to one of the subject luminous fluxes passing through different pupil regions is formed on the phase difference detection pixel 21b. For this reason, the peak position of the image formed on the imaging pixel 21a and the peak position of the image formed on the phase difference detection pixel 21b do not coincide with each other, and an image shift occurs. In addition, since a part of the phase difference detection pixel 21b is shielded from light, the amount of light also decreases.

  When focus detection processing is performed during moving image shooting or live view display, the effect of image blur due to the phase difference detection pixel 21b appears as an image. The influence of this image shift is reduced by pixel interpolation processing described later.

  Hereinafter, a specific operation of the imaging apparatus according to the present embodiment will be described. FIG. 5 is a flowchart showing the process of moving image recording (moving image shooting) operation by the imaging apparatus. The moving image recording operation is started, for example, when the release button is pressed during the moving image shooting mode. 5 is executed by the CPU 29 according to a program stored in the ROM 43. Note that FIG. 5 shows the operation at the time of moving image recording, but the imaging control method of the present embodiment described below can also be applied at the time of still image recording or live view display.

  When the operation of the flowchart of FIG. 5 is started, the CPU 29 starts capturing of imaging data (step S101). Here, the CPU 29 inputs setting data corresponding to the current operation mode to the reading method setting unit 231 of the imaging control circuit 23. In accordance with the setting data, the imaging control circuit 23 controls reading of pixel data from the imaging element 21.

  In the example of FIG. 5, setting data corresponding to a reading method at the time of moving image recording is input. When the reading method is set in the reading method setting unit 231, the mixing rate setting unit 232 sets the horizontal and vertical pixel reading intervals when mixing or thinning out pixel data. For example, in the case of 2 × 2 pixel mixed readout or 2 × 2 pixel thinning readout, 2 is set for each of the horizontal readout interval and the vertical readout interval. In the case of 3 × 3 pixel mixed readout or 3 × 3 pixel thinning readout, 3 is set for each of the horizontal readout interval and the vertical readout interval.

  When the readout method is set in the imaging control circuit 23, an image signal in a state where pixel mixture or pixel thinning is performed is read from the imaging element 21 in accordance with the readout method set in the imaging control circuit 23. The image signal read from the image sensor 21 is digitized by the ADC 27 and then temporarily stored in the DRAM 41 as image data.

  Next, the CPU 29 performs focus detection processing (step S102). Here, the CPU 29 causes the focus detection circuit 33 to execute focus detection processing. Upon receiving an instruction to execute the focus detection process, the focus detection circuit 33 reads out pixel data corresponding to the phase difference detection pixel (mixed or thinned out) from the imaging data temporarily stored in the DRAM 41, and uses this pixel data as the pixel data. The defocus direction and defocus amount of the photographic lens 11 are calculated using a known phase difference method.

  Next, the CPU 29 performs a mixing rate calculation process (step S103). Here, the CPU 29 calculates the mixing rate, which is a value necessary for the interpolation rate determination unit 312 to determine the interpolation rate. The mixing rate is the mixing rate of the pixel data of the phase difference detection pixel in each pixel data after the pixel mixture reading or the pixel thinning-out reading.

  Hereinafter, a method for calculating the mixing rate will be described. For example, when mixed reading or thinning-out reading is used as a reading method of the image sensor 21, there is a possibility that pixel data of the phase difference detection pixel is mixed into the pixel data after reading. The mixing ratio of the pixel data of the phase difference detection pixel is calculated.

  FIG. 6A is a diagram showing a pixel arrangement before 2 × 2 pixel mixed readout. FIG. 6B is a diagram showing a pixel arrangement after 2 × 2 pixel mixed readout.

  The numbers given to the upper and left sides in FIGS. 6A and 6B indicate the coordinates of the pixels. In the following description, it is assumed that two horizontal and vertical pixels including R pixels with numbers are the same coordinates. In addition, r shown in FIG. 6A indicates a phase difference detection pixel (right opening phase difference detection pixel) whose left half face is shielded from light, and l shown in FIG. 6A shows that the right half face is shielded from light. It shows that it is a phase difference detection pixel (left aperture phase difference detection pixel). Further, r shown in the left diagram of FIG. 6B indicates that the right aperture phase difference detection pixel is mixed in the pixel, and l shown in the left diagram of FIG. 6B indicates the pixel. Indicates that the left aperture phase difference detection pixel is mixed. The numbers attached to r and l in FIG. 6B indicate the number of right aperture phase difference detection pixels or left aperture phase difference detection pixels mixed in the pixel, respectively. Furthermore, the numbers shown in the diagram on the right side of FIG. 6B indicate the total number of phase difference detection pixels mixed in each pixel.

  When 2 × 2 pixel mixed readout is performed for the pixel arrangement as shown in FIG. 6A, pixel data of the same color for both horizontal and vertical pixels are mixed. As a mixing method, for example, any one of addition average, integration, and weighted addition average can be considered.

  For example, by mixing pixel data of four R pixels of coordinates (1, 1), coordinates (1, 2), coordinates (2, 1), and coordinates (2, 2) shown in FIG. Pixel data of the R pixel at the coordinate (1, 1) in FIG. 6B is obtained. Other colors other than the R pixel are mixed in the same manner.

  Assuming that the phase difference detection pixel is arranged at the position of the G (Gb) pixel, when the Gb pixel of each coordinate is mixed, the pixel data of the phase difference detection pixel is mixed into the pixel data after the addition. Become. That is, when the pixel data in the thick frame in FIG. 6A are mixed, the pixel data of the phase difference detection pixel is mixed. As can be seen from FIG. 6B, in the case of 2 × 2 pixel mixed readout, pixel data of each phase difference detection pixel is mixed into the pixel data at each Gb position after mixing. A pixel mixed with pixel data of such a phase difference detection pixel can be used as a phase difference detection pixel even after mixed reading.

  FIG. 7A is a diagram showing pixel data before 3 × 3 pixel mixed readout. FIG. 7B is a diagram showing pixel data after 3 × 3 pixel mixed readout.

  When 3 × 3 pixel mixed readout is performed for the pixel arrangement shown in FIG. 7A, pixel data of the same color for each horizontal and vertical pixel is mixed.

  For example, the coordinates (2, 1), coordinates (2, 2), coordinates (2, 3), coordinates (3, 1), (3, 2), (3, 3), ( 4, 1), (4, 2), and (4, 3) of the nine R pixel data are mixed, so that the pixel data of the R pixel at the coordinates (1, 1) in FIG. can get. Other colors other than the R pixel are mixed in the same manner. In the example shown in FIGS. 7A and 7B, the pixel data of the first row is not used for mixing, but the pixel data of the first row may be used for mixing.

  As described above, assuming that the phase difference detection pixel is arranged at the position of the G (Gb) pixel, when the Gb pixel of each coordinate is mixed, the pixel data of the phase difference detection pixel is mixed in the pixel data after addition. Is done. That is, when the pixel data in the thick frame in FIG. 7A is mixed, the pixel data of the phase difference detection pixel is mixed. As can be seen from FIG. 7B, in the case of 3 × 3 pixel mixed readout, the number of pixel data of the phase difference detection pixels mixed depending on the position differs.

The number of pixel data of the phase difference detection pixels included in the pixel data after readout is n, the horizontal readout interval at the time of pixel mixing or pixel decimation is h, and the vertical readout interval at the time of pixel mixing or pixel decimation Assuming v, the mixing rate α in the present embodiment is calculated for each pixel position according to the following (Equation 1).
α = n / (h × v) (Formula 1)
For example, in the case of 2 × 2 pixel mixed readout, α is ¼ regardless of the position of the Gb pixel. In the case of 3 × 3 pixel mixed readout, α changes between 1/9 and 4/9 according to the position of the Gb pixel.

  Here, the above example shows an example in which the mixing rate is calculated for each moving image recording, but the mixing rate for each reading method may be calculated in advance. In this case, it is only necessary to acquire the corresponding mixing rate when the reading method is set.

  Returning to the description of FIG. Next, the CPU 29 performs gain adjustment processing (step S104). Here, the CPU 29 causes the gain adjustment unit 311 of the image processing unit 31 to perform gain adjustment. As described above, since the phase difference detection pixel 21b is shielded from light, incident light is attenuated. Therefore, in the gain adjustment process, correction of the dimming of the pixel data output from the phase difference detection pixel 21b is performed. However, each pixel data can include both the pixel data of the phase difference detection pixel and the pixel data of the imaging pixel. Therefore, the gain adjustment amount is determined in consideration of the pixel data mixing rate of the phase difference detection pixels. In order to simplify the description, assuming that the amount of light is 1/2 in a phase difference detection pixel that shields either the left or right region as shown in FIG. 3, the gain adjustment amount β is given by the following (formula 2). .

β = (h × v) / ((h × v) −n × 0.5) (Formula 2)
For example, in the case of 2 × 2 pixel mixed readout, β is 4 / 3.5 regardless of the position of the Gb pixel. On the other hand, in the case of 3 × 3 pixel mixed readout, β varies between 9 / 8.5 and 9/7 depending on the position of the Gb pixel.

  A specific process of the gain adjustment process is a process of multiplying the value of the pixel data of the phase difference detection pixel by the gain adjustment amount β obtained by (Equation 2).

  Here, (Equation 2) assumes that the amount of light is 1/2 in the phase difference detection pixel. Actually, the amount of light reduction varies depending on the aperture of the taking lens 11, the aperture of the diaphragm 13, and the like. Therefore, it is desirable that 0.5 in (Equation 2) is adaptively switched according to the aperture of the taking lens 11, the aperture of the diaphragm 13, and the like.

  Next, the CPU 29 performs pixel interpolation processing (step S105). Here, the CPU 29 causes the interpolation ratio determination unit 312 and the pixel interpolation unit 313 of the image processing unit 31 to perform pixel interpolation processing. The pixel interpolation process will be described in detail later.

  Next, the CPU 29 performs lens driving (step S106). Here, the CPU 29 controls the drive unit 17 based on the defocus direction and the defocus amount of the photographing lens 11 detected by the focus detection circuit 33 in step S102, and focuses the photographing lens 11.

  Next, the CPU 29 performs image processing (step S107). Here, the CPU 29 causes the development processing unit 314 and the color conversion processing unit 315 of the image processing unit 31 to execute the development processing and color conversion processing on the imaging data temporarily stored in the DRAM 41 as a result of the pixel interpolation processing in step S105. . Processing parameters used for development processing and color conversion processing are those for recording. The processing parameters for recording are stored in advance in the ROM 43, for example.

  Next, the CPU 29 records the image data temporarily stored in the DRAM 41 as a result of the image processing on the recording medium 45 (step S108).

  Next, the CPU 29 determines whether or not to stop moving image recording (step S109). Here, the CPU 29 determines the operation state of the release button of the operation unit 19. That is, when the release button is pressed again, the CPU 29 determines to stop moving image recording.

  If it is determined in step S109 that the moving image recording is not stopped, the CPU 29 returns the process to step S101 and continues the moving image recording. On the other hand, when it is determined in step S109 that the moving image recording is to be stopped, the CPU 29 ends the process of FIG.

  FIG. 8 is a flowchart showing details of the pixel interpolation processing. The pixel interpolation process is a process performed mainly by the interpolation ratio determination unit 312 and the pixel interpolation unit 313.

  When the operation of the flowchart of FIG. 8 is started, the interpolation ratio determination unit 312 determines whether or not pixel data of the phase difference detection pixel is included in the imaging data to be processed (step S201). The coordinate data of the phase difference detection pixel is stored in advance in the ROM 43, for example, and the interpolation ratio determination unit 312 determines whether or not the pixel data of the phase difference detection pixel is included in the imaging data to be processed from this coordinate data. judge. Here, as described above, whether or not the pixel data of the phase difference detection pixel is included in the pixel data after reading is also determined by the reading method. Therefore, in practice, the interpolation ratio determination unit 312 acquires the setting data of the readout method setting unit 231 and the mixing rate setting unit 232, refers to the coordinate data of the phase difference detection pixels according to the acquired setting data, and sets the imaging data. It is determined whether or not pixel data of the phase difference detection pixel is included.

  If it is determined in step S201 that the pixel data of the phase difference detection pixel is not included in the imaging data to be processed, the processing in FIG. 8 is terminated. In step S201, when it is determined that the imaging data to be processed includes the pixel data of the phase difference detection pixel, the interpolation ratio determination unit 312 determines the mixing rate α calculated by the above-described mixing rate calculation process. Is acquired (step S202).

Next, the interpolation ratio determining unit 312 determines the application ratio of interpolation (step S203). Assuming that the ratio of applying the pixel data of the phase difference detection pixel is af_pixel_weight and the ratio of applying the pixel data of the peripheral pixels is near_pixel_weight, these are given by (Equation 3) below.
af_pixel_weight = 1-α
near_pixel_weight = α (Formula 3)
Next, the pixel interpolation unit 313 weights and adds the pixel data of the phase detection pixel and the pixel data of the surrounding pixels according to the application ratio determined by the interpolation ratio determination unit (step S204). Here, weighted addition is performed according to the following (formula 4).
correct_pixel = af_pixel_weight × af_pixel + near_pixel_weight × (pixel_h_1 + pixel_h_2 + pixel_v_1 + pixel_v_2) (Formula 4)
“Correct_pixel” in (Expression 4) indicates the value of the corrected pixel data after weighted addition. Further, af_pixel indicates the value of pixel data of the phase difference detection pixel (actually pixel data of the pixel including the phase difference detection pixel). Also, pixel_h_1 indicates the value of pixel data of the same color pixel of the left + 1 pixel of the phase difference detection pixel (pixel data on the upper left in the case of the Bayer array). Also, pixel_h_2 indicates the value of pixel data of the same color pixel of the right + 1 pixel of the phase difference detection pixel (pixel data on the lower right in the case of the Bayer array). pixel_v_1 indicates the value of pixel data of the same color pixel of the upper +1 pixel of the phase difference detection pixel (pixel data on the upper right in the case of the Bayer array). Also, pixel_v_2 indicates the value of pixel data of the same color pixel of the lower +1 pixel of the phase difference detection pixel (pixel data on the lower left in the case of the Bayer array).

  The weighted addition shown in (Expression 4) is performed for each phase difference detection pixel. After the weighted addition shown in (Equation 4) is performed for all the phase difference detection pixels, the processing in FIG. 8 ends.

  As described above, in the present embodiment, when pixel mixing or pixel thinning is performed, according to the mixing ratio of the pixel data of the phase difference detection pixel in each phase difference detection pixel after pixel mixing or after pixel thinning, The application ratio between the pixel data of each phase difference detection pixel and the interpolation data from the surrounding pixel data is changed. As a result, when the pixel data mixture rate of the phase difference detection pixel is low, the application ratio of the pixel data of the phase difference detection pixel after gain adjustment is high, so that overcorrection does not occur and the sharpness of the image is reduced. Can be suppressed. On the contrary, when the pixel data mixture rate of the phase difference detection pixel is high, the application ratio of the pixel data of the peripheral pixels is high, so that it is possible to suppress the influence of image shift caused by using the phase difference detection pixel. It is.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. Further, in the description of each operation flowchart described above, the operation is described using “first”, “next”, and the like for convenience, but this does not mean that it is essential to perform the operations in this order. Absent.

  Moreover, each process by embodiment mentioned above can also be memorize | stored as a program which CPU29 can perform. In addition, memory cards (ROM cards, RAM cards, etc.), magnetic disks (floppy disks, hard disks, etc.), optical disks (CD-ROM, DVD, etc.), storage media of external storage devices such as semiconductor memories, etc. are distributed. be able to. Then, the CPU 29 can execute the above-described processing by reading a program stored in the storage medium of the external storage device and controlling the operation by the read program.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

  DESCRIPTION OF SYMBOLS 1 ... Camera, 11 ... Shooting lens, 13 ... Aperture, 15 ... Mechanical shutter, 17 ... Drive part, 19 ... Operation part, 21 ... Image sensor, 23 ... Imaging control circuit, 25 ... AMP, 27 ... Analog-digital converter (ADC) , 29 ... CPU, 31 ... Image processing unit, 33 ... Focus detection circuit, 35 ... Video encoder, 37 ... Display unit, 39 ... Bus, 41 ... DRAM, 43 ... ROM, 45 ... Recording medium, 231 ... Reading method setting 232: Mixing rate setting unit, 311 ... Gain adjusting unit, 312 ... Interpolation ratio determining unit, 313 ... Pixel interpolation unit, 314 ... Development processing unit, 315 ... Color conversion processing unit.

Claims (6)

An image sensor in which phase difference detection pixels for focus detection are arranged at some positions of the image pickup pixels;
A readout method setting unit for setting a readout method when reading out pixel data from the imaging pixel and the phase difference detection pixel of the imaging element;
An image processing unit for correcting pixel data of the phase difference detection pixels;
Comprising
The image processing unit
A gain adjusting unit that adjusts the gain of the pixel data of the phase difference detection pixels read according to the reading method set by the reading method setting unit;
A pixel interpolation unit that weights and adds pixel data of the phase difference detection pixel that has been gain-adjusted and pixel data of imaging pixels around the phase difference detection pixel;
An interpolation ratio determining unit that determines a weighting coefficient in the weighted addition according to the reading method set by the reading method setting unit;
Have
When the readout method set by the readout method setting unit is a method of mixing a plurality of pixels, the interpolation ratio determining unit is mixed depending on the arrangement of the phase difference detection pixels included in the mixed pixels higher mixing rate of the pixel data of the phase difference detection pixels in the pixel data read out in accordance with the reading method a rate increases to reduce the weighting factor of the pixel data of the gain-adjusted phase difference detection pixels Alternatively, an imaging apparatus characterized by increasing a weighting coefficient of pixel data of imaging pixels around the phase difference detection pixel .   The imaging apparatus according to claim 1, wherein the readout method setting unit sets a readout interval in the horizontal direction and a readout interval in the vertical direction of pixel data.   The imaging apparatus according to claim 1, wherein the readout method setting unit performs an averaging process, an integration process, or a weighted averaging process on pixel data read from the imaging element.   The imaging apparatus according to claim 1, wherein the interpolation ratio determination unit determines a mixing ratio according to the number of the phase difference detection pixels included in the mixed pixels.   The imaging apparatus according to claim 1, wherein the gain adjustment unit switches a gain adjustment amount according to the mixing rate. Set the readout method when reading out pixel data from the imaging pixel of the imaging element in which the phase difference detection pixel for performing focus detection at a partial position of the imaging element and the phase difference detection pixel are arranged,
Perform gain adjustment of the pixel data of the phase difference detection pixels read according to the set readout method,
Weighting and adding pixel data of the phase difference detection pixel that has been gain-adjusted and pixel data of imaging pixels around the phase difference detection pixel,
When determining the weighting coefficient for the weighted addition according to the set readout method,
When the set readout method is a method of mixing a plurality of pixels, the mixing rate determined by the arrangement of the phase difference detection pixels included in the pixels to be mixed is read according to the readout method. The weighting coefficient of the pixel data of the phase difference detection pixel whose gain has been adjusted is reduced, or the periphery of the phase difference detection pixel is imaged as the mixing ratio of the pixel data of the phase difference detection pixel in the obtained pixel data increases. A control method for an imaging apparatus, wherein a weighting coefficient of pixel data of a pixel is increased .

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