JP2016018034A - Imaging device, control method of the same, program and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanism that performs focus adjustments during a consecutive shooting, and can reduce a change in time between exposures during the consecutive shooting, in imaging devices provided with image pick-up elements having focus detection pixels.SOLUTION: An imaging device 100 comprises an image pick-up element 107 that has a focus detection pixel photoelectrically converting a flux of light passing through a pair of pupil areas different in an area of an exit pupil of an imaging optical system and outputting an image signal, and an imaging pixel photoelectrically converting a flux of light passing through the exit pupil of the imaging optical system and outputting an image signal. Time adjustment means 121d between-exposures is configured to, when performing a consecutively photograph of making sequential exposures of the image pick-up element 107, adjust a time between actual exposures on the basis of a detection result of focus detection means 121a performing a focus detection by use of an image signal of the focus detection pixel and an exposure condition set by exposure processing means 121c.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus having an imaging optical system such as a digital single-lens reflex camera.

  A single-lens reflex camera or the like has a mirror part composed of a main mirror and a sub mirror that can be driven. When the mirror is down, the subject light flux that has passed through the imaging optical system enters the phase difference detection AF unit and optical viewfinder, and when the mirror is up Subject light flux enters the imaging surface.

  In the case of continuous shooting with such a single-lens reflex camera, it is possible to perform phase difference AF using an AF unit of a phase difference detection method by raising and lowering the mirror portion between exposures to the image sensor. .

  However, in phase difference AF during continuous shooting, the mirror unit must be driven up and down to expose the AF unit and the image sensor. For this reason, even when the readout time of the image sensor is high, the drive time of the mirror unit is required, and high-speed continuous shooting is difficult.

  As means for solving the above problem, there has been proposed an imaging apparatus that performs continuous shooting by performing phase difference AF on an imaging surface using an imaging element having focus detection pixels (Patent Document 1). This imaging apparatus includes an imaging element having a focus detection pixel row in which a pair of pixels that receive each of the subject light fluxes that have passed through a pair of partial areas in the exit pupil of the imaging optical system are arranged in the horizontal direction. .

  At the time of continuous shooting, a phase difference AF calculation process (AF calculation) is performed using a signal generated by the focus detection pixel array by the main exposure to the image sensor, and a focus shift amount (defocus amount) is calculated. . After that, by moving the focus lens to the in-focus position based on the calculated defocus amount, phase difference AF can be performed during continuous shooting without performing up-down driving of the mirror unit.

JP 2009-109631 A

  However, in Patent Document 1, the focus detection pixel columns of the image sensor are discretely arranged in the row direction, and an error occurs in the defocus amount, which is the AF calculation result, depending on subject conditions and photographing conditions. Therefore, there is a case where the driving of the image sensor is switched and the AF operation is performed on the live view image that is a sequential display image. As a result, the focus detection method based on the main exposure image that is a captured image and the live view image is selectively used, and the time between the main exposures varies greatly in continuous shooting.

  In view of this, the present invention provides a mechanism capable of performing focus adjustment during continuous shooting and reducing fluctuations in time between exposures during continuous shooting in an imaging device including an image sensor having focus detection pixels. The purpose is to provide.

  In order to achieve the above object, the present invention provides a focus detection pixel that photoelectrically converts light beams passing through different pairs of pupil regions of an exit pupil region of a photographing optical system and outputs a pair of image signals, and the photographing optical An image pickup apparatus including an image pickup device having an image pickup pixel that photoelectrically converts a light beam passing through the exit pupil of a system and outputs an image signal, and performs focus detection using an image signal of the focus detection pixel of the image pickup device. A focus detection unit that performs the focus adjustment by driving a focus lens based on a detection result of the focus detection unit, an exposure processing unit that sets an exposure condition at the time of photographing, and the image sensor is sequentially exposed. A determination unit that determines whether or not continuous shooting is to be performed, and continuous shooting based on a detection result of the focus detection unit and an exposure condition set by the exposure processing unit when the determination unit determines that continuous shooting is to be performed. When shooting Characterized in that it comprises a exposure between time adjustment unit that performs time adjustment between exposure.

  Further, the present invention provides a focus detection pixel that photoelectrically converts light beams passing through different pairs of pupil regions in the exit pupil region of the photographing optical system and outputs a pair of image signals, and the exit pupil of the photographing optical system. An image pickup apparatus including an image pickup device having an image pickup pixel that photoelectrically converts a passing light beam and outputs an image signal, wherein focus detection is performed using an image signal of the focus detection pixel of the image pickup device. A focus lens based on a detection result of the first focus detection means or the second focus detection means, and a second focus detection means for performing focus detection by a method different from the first focus detection means. A focus adjusting means for adjusting the focus by driving, an exposure processing means for setting an exposure condition at the time of shooting, a determining means for determining whether or not continuous shooting for sequentially exposing the image sensor, and the determining means When it is judged as continuous shooting Inter-exposure time adjusting means for adjusting the time between exposures in continuous shooting based on the detection result of the first focus detection means and the exposure condition set by the exposure processing means. .

  ADVANTAGE OF THE INVENTION According to this invention, in an imaging device provided with the image pick-up element which has a focus detection pixel, focus adjustment can be performed during continuous shooting, and the fluctuation | variation of the time between exposures during continuous shooting can be reduced.

1 is a block diagram illustrating a system configuration example of a digital camera that is an example of an embodiment of an imaging apparatus of the present invention. It is a block diagram which shows the structural example of an image pick-up element (solid-state image sensor). (A) is a top view of an imaging pixel of 2 rows x 2 columns, (b) is an AA line sectional view of (a). (A) is a top view of the pixel of 2 rows x 2 columns containing a focus detection pixel, (b) is the sectional view on the AA line of (a). (A) is a figure which shows a mode that a light beam is restrict | limited by the aperture_diaphragm | restriction of the imaging optical system in the position of an exit pupil surface with respect to the pixel of the center vicinity of an image pick-up element, (b) is an image pick-up element in (a). It is a figure explaining the change of the gravity center position by the vignetting in the exit pupil plane of the focus detection pixel in the center of. FIG. 5A is a diagram showing sensitivity distributions of the A image pixel, the B image pixel, and the imaging pixel in the cross section along the line AA in FIG. 5B when the aperture is opened, and FIG. It is a figure which shows the sensitivity distribution of A image pixel, B image pixel, and imaging pixel in the AA line cross section of FIG.5 (b) in the case. It is a figure which shows the example of arrangement | positioning of the imaging pixel and focus detection pixel in an image sensor. It is a figure which shows the operation | movement sequence of the digital camera at the time of the continuous shooting which exposes an image pick-up element sequentially. It is a figure which shows the operation | movement sequence of the digital camera at the time of continuous shooting in the case of performing AF processing by focus detection during live view image display. It is a figure which shows the operation | movement sequence of the digital camera at the time of continuous shooting at the time of performing the time adjustment between exposures when performing focus detection using a live view image. It is a figure which shows the operation | movement sequence of the digital camera at the time of continuous shooting at the time of performing the time adjustment between exposures when performing focus detection with a picked-up image. It is a flowchart figure explaining the continuous shooting imaging | photography operation | movement of a digital camera. FIG. 13 is a flowchart for explaining AF processing (LV_AF processing) in step S1100 of FIG.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a system configuration example of a digital camera which is an example of an embodiment of an imaging apparatus of the present invention. In the present embodiment, a digital camera in which a camera body and a photographing optical system are integrally formed is exemplified. However, a digital camera in which a lens barrel constituting the photographing optical system is mounted on the camera body in a replaceable manner. It can also be applied to cameras.

  As shown in FIG. 1, the digital camera 100 of the present embodiment includes a first lens group 101, a second lens group 103, and a third lens group 105 that are arranged in order from the subject side to the image plane side. The first lens group 101, the second lens group 103, and the third lens group 105 constitute a photographing optical system, and are respectively held by a lens holding unit (not shown) so as to be movable in the optical axis direction.

  A diaphragm / shutter 102 is provided on the subject side of the second lens group 103, and the diaphragm / shutter 102 adjusts the light amount during photographing by adjusting the aperture diameter. The aperture / shutter 102 and the second lens group 103 integrally move forward and backward in the optical axis direction, and perform a zooming operation in conjunction with the forward and backward movement of the first lens group 101.

  The subject luminous flux that has passed through the photographing optical system forms an image on the image sensor 107 via the optical low-pass filter 106. The optical low-pass filter 106 is an optical element for reducing false colors and moire in the captured image.

  The image sensor 107 includes a CMOS sensor and its peripheral circuits, and photoelectrically converts a subject image formed on the image pickup surface to output an image signal. The image sensor 107 is a two-dimensional single-plate color sensor in which a Bayer array primary color mosaic filter is formed on-chip on light receiving pixels of m pixels in the horizontal direction and n pixels in the vertical direction.

  As will be described later, the image sensor 107 includes a plurality of focus detection pixels and a plurality of imaging pixels. The plurality of focus detection pixels receive light beams that have passed through different pupil regions of the photographing optical system and output a first pixel signal. The plurality of imaging pixels receive a light beam that has passed through the same pupil region of the photographing optical system and output a second pixel signal.

  The zoom actuator 111 rotates the cam cylinder (not shown) to drive the first lens group 101, the second lens group 103, and the third lens group 105 forward and backward in the optical axis direction, thereby performing a zooming operation. The aperture shutter actuator 112 controls the aperture diameter of the aperture / shutter 102 to adjust the amount of photographing light (aperture adjustment), and performs exposure time control during still image shooting. The focus actuator 114 performs focus adjustment by driving the third lens group 105 as a focus lens back and forth in the optical axis direction.

  The electronic flash 115 is used for subject illumination during photographing. As the electronic flash 115, a flash illumination device using a xenon tube is suitable, but an illumination device including LEDs that emit light continuously may be used. The AF auxiliary light means 116 projects a mask image having a predetermined aperture pattern onto the object field via the light projection lens, and improves the focus detection capability for a dark subject or a low-contrast subject.

  The camera control circuit 121 includes a calculation unit, a ROM, a RAM, an A / D converter, a D / A converter, a communication interface circuit, and the like in addition to a CPU that controls the entire camera. A program stored in a ROM or the like of the camera control circuit 121 is expanded in the RAM, and a series of processing such as AF, shooting, image processing, and recording is executed by the CPU.

  The camera control circuit 121 includes a focus detection unit 121a, a contrast evaluation value generation unit 121b, an exposure processing unit 121c, and an inter-exposure time adjustment unit 121d. The focus detection unit 121a corresponds to an example of the first focus detection unit of the present invention, and the contrast evaluation value generation unit 121b corresponds to an example of the second focus detection unit of the present invention.

  The focus detection unit 121 a performs focus detection using the focus detection pixels of the image sensor 107. Details of the focus detection method by the focus detection means 121a will be described later. The contrast evaluation value generation unit 121b generates a contrast evaluation value by extracting a high-frequency component signal from the imaging signal from the imaging element 107 by γ processing and various filter processing. The exposure processing unit 121c performs processing for setting an aperture value, a digital gain (ISO sensitivity), a shutter speed, and the like, which are exposure conditions set in the main exposure based on the image signal obtained from the image sensor 107. The inter-exposure time adjustment unit 121d adjusts the time between exposures based on the focus detection result by the focus detection unit 121 and the exposure condition set by the exposure processing unit 121c.

  The electronic flash control circuit 122 controls the light emission of the electronic flash 115 in synchronization with the photographing operation. The auxiliary light drive circuit 123 controls the AF auxiliary light unit 116 to emit light in synchronization with the focus detection operation. The image sensor driving circuit 124 controls the image capturing operation of the image sensor 107 and A / D converts the image signal output from the image sensor 107 and transmits the image signal to the camera control circuit 121. The image processing circuit 125 performs image processing such as γ conversion, color interpolation, and JPEG compression on the image signal obtained from the image sensor 107.

  The focus drive circuit 126 controls the focus actuator 114 based on the focus detection result, and adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction. The shutter drive circuit 128 controls the aperture shutter actuator 112 to control the aperture of the aperture / shutter 102. The zoom drive circuit 129 drives the zoom actuator 111 according to the zoom operation of the photographer.

  The display 131 is composed of an LCD or the like and performs live view display, and also displays information related to the shooting mode of the camera, a preview image before shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. To do. The operation switch group 132 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The flash memory 133 is detachable and records captured images.

  FIG. 2 is a block diagram illustrating a configuration example of the image sensor 107. Note that FIG. 2 shows the minimum configuration necessary for the description of the image signal readout operation, and the pixel reset signal and the like are not shown.

  In FIG. 2, the photoelectric conversion unit 201 (PDmn) includes a photodiode, a pixel amplifier, a reset switch, and the like. M of the photoelectric conversion unit 201 (PDmn) is an X-direction address, and m = 0, 1,. N is a Y-direction address, and n = 0, 1,..., N−1. The image sensor 107 of the present embodiment is configured by arranging m × n photoelectric conversion units 201 in two dimensions. In addition, the code | symbol of m of the photoelectric conversion part 201 (PDmn) is attached | subjected only to the photoelectric conversion part 201 (PD00) periphery of the upper left of a figure for convenience of explanation.

  The switch 202 is a switch that selects the output of the photoelectric conversion unit 201 (PDmn), and is selected for each row by the vertical scanning circuit 208. The line memory (MEM) 203 is a memory that temporarily stores the output of the photoelectric conversion unit 201 (PDmn), and stores the output of the photoelectric conversion unit 201 (PDmn) for one row selected by the vertical scanning circuit 208. To do. As the line memory 203, a capacitor is usually used.

  The switch 204 is controlled by the signal HRST, is connected to the horizontal output line, and resets the horizontal output line to a predetermined potential VHRST. The switch 205 (H0 to Hm-1) sequentially outputs the output of the photoelectric conversion unit 201 (PDmn) stored in the line memory 203 to the horizontal output line. By sequentially scanning the switch 205 (H0 to Hm-1) by a horizontal scanning circuit 206 described later, the output of the photoelectric conversion unit 201 (PDmn) for one row is read.

  The horizontal scanning circuit 206 sequentially operates the output of the photoelectric conversion unit 201 (PDmn) stored in the line memory 203 and outputs it to the horizontal output line. The signal PHST is a data input of the horizontal scanning circuit 206, PH1 and PH2 are shift clock inputs, data is set when PH1 = H, and data is latched at PH2. By inputting the shift clock to the shift clock inputs PH1 and PH2, the signal PHST can be sequentially shifted and the switches 205 (H0 to Hm-1) can be sequentially turned on. The signal SKIP is a control input signal for performing setting during thinning readout. By setting the signal SKIP to H level, the horizontal scanning circuit 206 can be skipped at predetermined intervals. The amplifier AMP207 amplifies the signal on the horizontal output line and outputs it to the terminal VOUT.

  The vertical scanning circuit 208 can select the selection switch 202 of the photoelectric conversion unit 201 (PDmn) by sequentially scanning and outputting the control signals V0 to Vn-1. As in the case of the horizontal scanning circuit 206, the control signals V0 to Vn-1 are controlled by a signal PVST, shift clocks PV1 and PV2, which are data inputs, and a signal SKIP for performing thinning-out reading settings. Note that the details of the operation of the vertical scanning circuit 208 are the same as those of the horizontal scanning circuit 206, and thus description thereof is omitted.

  Next, a phase difference detection method using focus detection pixels will be described. 3 to 6 are diagrams for describing the structures of the imaging pixels and the focus detection pixels of the imaging element 107. In this embodiment, out of 4 pixels of 2 × 2, pixels having G (green) spectral sensitivity are arranged in two diagonal pixels, and R (red) and B (blue) spectral sensitivity are arranged in the other two pixels. A Bayer array in which one pixel having each of the above is arranged is employed. In addition, focus detection pixels having a structure to be described later are distributed and arranged according to a predetermined rule between the Bayer arrays.

  FIG. 3A is a plan view of 2 × 2 imaging pixels. As is well known, in the Bayer array, G (Green) pixels are arranged in a diagonal direction, and R (Red) and B (Blue) pixels are arranged in the other two pixels. The 2 rows × 2 columns structure is repeatedly arranged.

  FIG.3 (b) is the sectional view on the AA line of Fig.3 (a). In FIG. 3B, ML is an on-chip microlens disposed on the forefront of each pixel, CFR is an R color filter, and CFG is a G color filter. PD schematically shows a photoelectric conversion unit of the CMOS sensor, and CL is a wiring layer for forming signal lines for transmitting various signals in the CMOS sensor. TL schematically shows a photographing optical system.

  The on-chip microlens ML and the photoelectric conversion unit PD of the imaging pixel are configured to capture the light flux that has passed through the photographing optical system TL as effectively as possible. In other words, the exit pupil EP of the photographic optical system TL and the photoelectric conversion unit PD are designed to have a conjugate relationship by the microlens ML, and the effective area of the photoelectric conversion unit PD is large. In FIG. 3B, the incident light beam of the G pixel has been described, but the R pixel and the B pixel also have the same structure. Accordingly, the exit pupil EP corresponding to each of the RGB imaging pixels has a large diameter, and the S / N of the image signal is improved by efficiently capturing the light flux from the subject.

  FIG. 4 is a diagram for explaining the arrangement and structure of focus detection pixels for performing pupil division in the horizontal direction (left-right direction in FIG. 4) of the photographing optical system. Here, the horizontal direction refers to a direction along a straight line that is orthogonal to the optical axis and extends in the horizontal direction when the camera is held so that the optical axis of the photographing optical system is horizontal.

  FIG. 4A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. When obtaining an image signal for recording or viewing, the main component of luminance information is acquired by G pixels. Since human image recognition characteristics are sensitive to luminance information, image quality degradation is easily recognized when G pixels are lost. On the other hand, the R pixel and the B pixel are pixels that acquire color information (color difference information), but human visual characteristics are insensitive to color information. For this reason, it is difficult for pixels for obtaining color information to recognize image quality degradation even if some defects occur. Therefore, in the present embodiment, among the pixels of 2 rows × 2 columns, the G pixel is left as an imaging pixel, and the R and B pixels are replaced with focus detection pixels. This is indicated by SA and SB in FIG.

  FIG. 4B is a cross-sectional view taken along line AA in FIG. The micro lens ML and the photoelectric conversion unit PD of the focus detection pixel illustrated in FIG. 4B have the same structure as the imaging pixel illustrated in FIG. In the present embodiment, the focus detection pixel is configured by arranging a color filter CFG (Green) of G pixel at the pixel position of B pixel. Further, since pupil division is performed by the image sensor 107, the opening of the wiring layer CL is deviated in one direction with respect to the center line of the microlens ML.

  Specifically, since the opening OPHA of the pixel SA is biased to the right side, the light beam that has passed through the left exit pupil EPHA of the imaging optical system TL is received. Similarly, since the opening OPHB of the pixel SB is biased to the left side, the light beam that has passed through the right exit pupil EPHB of the imaging optical system TL is received. The pixels SA are regularly arranged in the horizontal direction, and a subject image acquired by these pixel groups is defined as an A image. The pixels SB are also regularly arranged in the horizontal direction, and the subject image acquired by these pixel groups is defined as a B image.

  Then, by detecting the relative positions of the A image and the B image and multiplying the shift amount of the image by a conversion coefficient, the focus shift amount (defocus amount) of the subject image can be calculated.

  Next, a method for obtaining a conversion coefficient for calculating the defocus amount from the image shift amount will be described. The conversion coefficient is calculated based on the aperture information of the imaging optical system and the sensitivity distribution of the focus detection pixels. The image sensor 107 (image sensor) receives a light beam limited by several constituent members such as the lens holding frame of the photographing lens TL and the diaphragm 102.

  FIG. 5 and FIG. 6 are diagrams illustrating a state in which the focus detection light beam is limited by the vignetting of the photographing optical system. FIG. 5A is a diagram showing a state in which the light beam is restricted by the stop 102 of the imaging optical system at the position of the exit pupil plane 501 with respect to the pixel near the center of the image sensor 107.

  In FIG. 5A, an image sensor 107a indicated by a solid line is an image sensor at the planned image plane position. The position 506 is the position of the optical axis 505 on the image sensor 107a at the planned imaging plane position. Light beams 507 and 508 are light beams when the diaphragm 102 is restricted by the diaphragm 102, respectively. The luminous fluxes 509 and 510 are luminous fluxes that are not limited by the diaphragm 102 when the diaphragm 102 is opened. Light beams 511 and 512 are focus detection light beams for the light beams 507 and 508, respectively. The barycentric positions 515 and 516 are barycentric positions of the focus detection light beams 511 and 512, respectively.

  Similarly, light beams 513 and 514 are focus detection light beams for light beams 509 and 510, respectively. The gravity center positions 517 and 518 are the gravity center positions of the focus detection light beams 513 and 514, respectively. Reference numeral 530 denotes a lens holding frame on the side closest to the image sensor, and 531 denotes a lens holding frame on the side closest to the subject.

  FIG. 5B is a diagram for explaining a change in the center of gravity due to vignetting on the exit pupil plane 501 of the focus detection pixel at the center of the image sensor 107b indicated by the broken line in FIG. In FIG. 5B, pupil areas 523 and 524 are pupils of light beams 507 and 508 restricted by the diaphragm 102 with respect to the central pixel of the image sensor 107b, and light beams 509 and 510 not restricted by the diaphragm 102, respectively. Indicates the area. Incident angle characteristics 525 and 526 indicate the incident angle characteristics of the focus detection pixels SA and SB, respectively.

  Light beams that have passed through the inside of the pupil regions 523 and 524 are incident on the focus detection pixels SA and SB with a sensitivity distribution indicated by the incident angle characteristics 525 and 526. Therefore, by obtaining the distribution centroids of the focus detection light fluxes that have passed through the inside of the pupil regions 523 and 524, the focus detection light flux is restricted by the stop 102, and the focus detection light flux is not restricted by the stop 102. Can be calculated.

  And each base line length can be calculated | required from the calculated center-of-gravity space | interval. Obtaining the conversion coefficient for calculating the defocus amount from the image shift amount by obtaining the sensitivity distribution information of the focus detection pixel and the aperture information of the imaging optical system from the measurement and calculation and storing them in a memory in advance. Can do.

  In FIG. 5A, the defocus amount 519 is DEF, and the distance 520 from the image sensor 107a to the exit pupil plane 501 is L. In addition, the base lengths (center-of-gravity distances) when the focus detection light beam is restricted by the diaphragm 102 and when it is not restricted are G1 (distance between centroid positions 515 and 516) and G2 (distance between centroid positions 517 and 518), respectively. ). In addition, the image shift amounts 521 and 522 are set to PRED1 and PRED2, respectively, and conversion coefficients for converting the image shift amounts 521 and 522 to the defocus amount DEF are set to K1 and K2, respectively.

  At this time, the defocus amount DEF can be obtained by the following equation (1).

DEF = K1 × PRED1 = K2 × PRED2 (1)
Also, conversion coefficients K1 and K2 for converting the image shift amounts 521 and 522 into the defocus amount DEF are obtained by the following equations (2) and (3), respectively.

K1 = L / G1 (2)
K2 = L / G2 (3)
Here, K1 <K2. Therefore, comparing the case where the aperture 102 is opened and the case where the aperture 102 is stopped, an error equivalent to the image misalignment amount occurs when the image misalignment amount is calculated, and the aperture 102 is reduced. In the case where there is an error, an error of K2 / K1 times occurs as the defocus amount.

  FIG. 6A is a diagram illustrating sensitivity distributions of the A image pixel 530, the B image pixel 531, and the imaging pixel 532 in the cross section along the line AA in FIG. 5B when the diaphragm 102 is opened. FIG. 6B is a diagram illustrating sensitivity distributions of the A image pixel 530, the B image pixel 531, and the imaging pixel 532 in the cross section along the line AA in FIG.

  In FIG. 6, the horizontal axis indicates the light incident angle, and the vertical axis indicates the sensitivity distribution. Comparing FIG. 6 (a) and FIG. 6 (b), the base length G1 is longer and the incident angle width with sensitivity is wider when the aperture is opened as shown in FIG. 6 (a). Since the base line length is proportional to the image shift amounts of the A and B images with respect to the defocus amount, the sensitivity of the image shift amount to the defocus amount increases as the base line length increases. Further, when the incident angle width having sensitivity is increased, the blur amount and image vignetting of the A image and the B image with respect to the defocus amount are increased. In general, as an image signal by a focus detection pixel, an image signal having a high sensitivity of an image shift amount with respect to a defocus amount and a small blur amount and image vignetting is desired.

  FIG. 7 is a diagram illustrating an arrangement example of imaging pixels and focus detection pixels in the imaging element 107. In FIG. 7, pixels G, GA, GB have a green color filter (green filter), pixel R has a red color filter (red filter), and pixel B has a blue color filter (blue filter). Filter).

  The focus detection pixel SA is a reference pixel group that is formed by biasing the opening of the pixel portion in the horizontal direction and detects the image shift amount in the horizontal direction with respect to the focus detection pixel SB. The focus detection pixel SB is a reference pixel group that is formed by biasing an opening of a pixel in a direction opposite to the focus detection pixel SA, and for detecting an image shift amount in the horizontal direction with respect to the focus detection pixel SA. The white portions of the focus detection pixels SA and SB indicate the opening positions of the biased pixels. The focus detection pixels SA and SB are arranged from the AF line 1 to the AF line 4.

  In order to detect the focus state near the in-focus position with high accuracy, it is necessary to arrange the focus detection pixels densely. On the other hand, the image signal (pixel signal) at the position of the focus detection pixel needs to be generated by interpolation processing using the output signal of the surrounding imaging pixels and the output signal of the focus detection pixel. For this reason, when the influence of image quality degradation is taken into consideration, it is desirable to arrange focus detection pixels sparsely.

  In FIG. 7A, the focus detection pixels SA and SB are arranged at the position of the B pixel where the image quality deterioration due to the defect is difficult to be recognized in consideration of the influence of the image quality deterioration. On the other hand, in FIG. 7B, since the focus detection pixels SA and SB are provided with a large number of imaging pixels of the same color in the periphery, the G pixel that makes it relatively easy to perform interpolation of the image signal at the position of the focus detection pixel It is arranged at the position. In the present embodiment, the focus detection process and the correction process of the focus detection result are performed using the signal obtained from the focus detection pixel. The arrangement of the focus detection pixels at that time is shown in FIGS. It is not limited to the two examples shown in b).

  Next, a focus detection method using a contrast detection method using imaging pixels will be described. The contrast evaluation value generated by the contrast evaluation value generation unit 121b of the camera control circuit 121 is a value representing the sharpness (contrast magnitude) of the image generated based on the output signal from the image sensor 107. Since the sharpness of the focused image is high and the sharpness of the blurred image is low, the contrast evaluation value can be used as a value representing the focus state of the imaging optical system. However, since the defocus amount is not known as in the phase difference detection method using the focus detection pixels described above, it is necessary to search for the focus position where the contrast evaluation value becomes the peak value.

  With reference to FIGS. 8 to 11, an example of operation of the digital camera 100 during continuous shooting will be described. 8 to 11 show the operation sequence for each item of the release switch (SW2) ON, the image sensor 107, AF processing, and the focus lens (third lens group) 105. Further, when the photographer presses a release button (not shown) halfway to turn on the release switch (SW1), AF processing is performed, and when the release button (SW2) is turned on by further pressing the release button, a falling signal is generated. This is shown as the start position. In the present embodiment, the second continuous shooting operation will be described after accumulating and reading the main exposure once after the start position.

  FIG. 8 is a diagram illustrating an operation sequence during continuous shooting in which the image sensor 107 of the digital camera 100 is sequentially exposed. The image sensor 107 performs accumulation that is the main exposure, starts reading of the imaging pixels, and reads the focus detection pixels in parallel. As described above, since the focus detection pixels are arranged in a range in which the image height is limited with respect to the imaging pixel range, the readout of the focus detection pixels is completed before the readout of the imaging pixels. The distance measurement range used for focus detection is set from a captured image or live view image of continuous shooting of the previous frame.

  After completing the readout of the focus detection pixels and setting the distance measurement range, AF calculation is performed. Then, correlation calculation is performed on the focus detection pixels, a defocus amount is obtained from the calculated image shift amount, and the focus lens 105 is moved to the in-focus position by the focus actuator 114 based on the calculated defocus amount.

  After the focus lens 105 is moved to the in-focus position, accumulation as main exposure is started, and the above-described continuous shooting operation sequence is repeated again.

  By performing the focus detection and the focus adjustment using the captured image by the continuous shooting sequence described above, the time between the main exposures can be shortened, and a high-speed continuous shooting operation can be performed.

  However, in the captured image, the exposure conditions such as the aperture value and ISO sensitivity are optimized for shooting, so that the exposure conditions suitable for focus detection cannot be obtained. Further, as described above, when the aperture value is reduced, the error of the defocus amount becomes large. However, in the live view image, since it is possible to set an exposure condition suitable for focus detection, for example, focus detection can be performed with the aperture opened.

  As a result, it is possible to expand the range in which the focus detection by the live view image can detect the focus compared to the focus detection by the captured image.

  Next, an operation sequence of the digital camera 100 at the time of continuous shooting when the AF process is performed by focus detection during live view image display will be described with reference to FIG.

  FIG. 9 shows a case where focus detection is performed from a live view image to adjust the focus. After accumulation by the main exposure, the defocus amount is calculated from the AF calculation result obtained by reading out the focus detection pixels, and the focus lens is moved to a predetermined position based on the defocus amount. The predetermined position here is not a focus position but a predetermined defocus position in order to enable focus detection by a contrast detection method.

  Specifically, the defocus position is set so as to be a value of 2.2 × Fδ or more when the permissible circle of confusion δ and the value Fδ indicated by the aperture value F are used as an index of the defocus amount. After the focus lens 105 is moved to a predetermined position, a live view image is displayed, and AF calculation is performed by reading out focus detection pixels from the live view image.

  When the defocus amount after the AF calculation can be focused with a predetermined error or less (for example, 1Fδ or less), the focus lens 105 is moved to the in-focus position using an AF method based on a phase difference detection method using focus detection pixels. And accumulation by the next main exposure is performed. When the defocus amount after the AF calculation exceeds a predetermined error, focus detection is performed using a contrast detection method.

  Then, while driving the focus lens 105, a plurality of contrast evaluation values are acquired and a peak value is detected. The focus determination uses the top three or four points with the largest contrast evaluation values, and performs interpolation calculation from the positions of the focus lens 105 corresponding to those evaluation values, thereby calculating the position of the focus lens 105 that is in focus. The focus lens 105 is moved to that position.

  As described above, by performing focus detection using the live view image, it is possible to expand the AF-capable shooting conditions even when focusing is not possible as a result of reading out the focus detection pixels of the captured image and performing AF calculation.

  However, the time required for focus adjustment differs between the phase difference detection method and the contrast detection method. Specifically, the contrast detection method has a longer focus adjustment time than the phase difference detection method. For this reason, the time between exposures in continuous shooting varies because the AF adjustment time varies depending on the subject conditions (brightness, contrast) and shooting conditions (aperture value, ISO sensitivity).

  Therefore, in this embodiment, a standby time is provided between exposures using the inter-exposure time adjusting unit 121d. Specifically, an upper limit value in which a phase difference detection method is possible (aperture value is within a predetermined value (for example, F11)), ISO sensitivity is within a predetermined value (for example, ISO 1600), and brightness is within a predetermined value (for example, Ev6). If it is in the vicinity, a waiting time is provided between exposures.

  FIG. 10 is a diagram illustrating an operation sequence of the digital camera 100 during continuous shooting when performing time adjustment between exposures when focus detection is performed using a live view image. In the case of the phase difference detection method using the focus detection pixels of the live view image and in the vicinity of the above-described upper limit value in the range that can be focused by the phase difference detection method, the inter-exposure time adjustment unit 121d waits between exposures. Provide time. Then, after the standby time elapses, preparation for shooting is started, accumulation by main exposure is performed, and continuous shooting operation is started again.

  As a result, in a range where the AF method varies depending on the subject conditions and photographing conditions, the standby time is provided by the inter-exposure time adjusting unit 121d, so that the focus adjustment time can be made constant, and continuous shooting for displaying live view images is possible. Time variation between exposures during shooting can be reduced.

  FIG. 11 is a diagram illustrating an operation sequence of the digital camera 100 during continuous shooting when performing time adjustment between exposures when focus detection is performed on a captured image. As in the case of the live view image of FIG. 10 described above, the time between exposures can be adjusted in the case where the focus detection can be performed on the captured image and the vicinity of the above-described upper limit of the range that can be focused by the phase difference detection method. A waiting time is provided between exposures by means 121d. Then, after the standby time has elapsed, preparation for shooting is started, accumulation by main exposure is performed, and continuous shooting operation is started again.

  As a result, in a range where the AF method varies depending on the subject condition and photographing conditions, the inter-exposure time adjusting unit 121d can provide a standby time between exposures, thereby making the focus adjustment time constant, and continuous shooting. Time variation between exposures can be reduced.

  Next, the continuous shooting operation of the digital camera 100 will be described with reference to FIG. Each process in FIG. 12 is executed by the CPU after the program stored in the ROM or the like of the camera control circuit 121 is expanded in the RAM.

  In FIG. 12, in step S1001, the camera control circuit 121 performs an AF operation when the photographer turns on the release switch (SW1) by half-pressing a release button (not shown). Specifically, the camera control circuit 121 performs a phase difference detection AF operation by reading out focus detection pixels in the live view image, moves the focus lens 105 to the in-focus position, and proceeds to step S1002.

  In step S1002, when the photographer fully presses the release button and the release switch (SW2) is turned on, the camera control circuit 121 proceeds to step S1003.

  In step S1003, the camera control circuit 121 performs shooting preparation such as exposure condition setting, and the process advances to step S1004.

  In step S <b> 1004, the camera control circuit 121 performs accumulation as main exposure for acquiring a captured image by the image sensor 107, and the process proceeds to step S <b> 1005.

  In step S1005, the camera control circuit 121 starts reading the imaging pixels and the focus detection pixels, and proceeds to step S1006, step S1007, and step S1008.

  In step S1006, the camera control circuit 121 determines whether reading of the focus detection pixel is completed. If completed, the process proceeds to step S1009.

  In step S1009, the camera control circuit 121 performs a phase difference detection type AF calculation using focus detection pixels, calculates a defocus amount, and proceeds to step S1010.

  In step S1010, the camera control circuit 121 determines the reliability of the defocus amount, which is the AF calculation result in step S1009. If the focus is possible, the process proceeds to step S1011. The process proceeds to S1100.

  In step S1100, the camera control circuit 121 performs AF processing (LV_AF processing) during live view image display, and the process proceeds to step S1016. Details of the AF processing (LV_AF processing) here will be described later with reference to FIG.

  On the other hand, in step S1007, the camera control circuit 121 determines whether the release switch (SW2) is on. If the release switch (SW2) is on, the camera control circuit 121 determines that continuous shooting is in progress and proceeds to step S1014. If the release switch (SW2) is off, End all processing.

  In step S1014, the camera control circuit 121 determines whether reading of the captured image is completed. If completed, the process proceeds to step S1015.

  In step S1015, the camera control circuit 121 performs shooting preparation processing for the image sensor 107, and the process proceeds to step S1016.

  In step S1008, the camera control circuit 121 performs exposure processing from the previous captured image or live view image, sets an aperture value, ISO sensitivity, shutter speed, and the like to determine shooting conditions, and proceeds to step S1011.

  In step S1011, the camera control circuit 121 sets a standby time for adjusting the time between exposures by the inter-exposure time adjusting unit 121d. Specifically, the camera control circuit 121 detects a shooting condition range (aperture value, ISO sensitivity, subject brightness, etc.) that allows focus detection based on the reliability of the exposure processing result in step S1008 and the AF calculation result in step S1010. It is determined whether it is the upper limit value. The camera control circuit 121 sets a standby time in order to adjust the time between exposures when it is equal to or less than the upper limit value of the photographing condition range in which focus detection is possible, and proceeds to step S1012. .

  In step S1012, the camera control circuit 121 drives the focus lens 105 based on the defocus amount calculated in step S1009, and waits for the standby time set by the inter-exposure time adjusting unit 121d in step S1011. Proceed to

  In step S1013, the camera control circuit 121 performs aperture driving based on the exposure processing result in step S1011 and proceeds to step S1016.

  In step S1016, the camera control circuit 121 determines whether or not preparation for shooting has been completed. If not completed, the process returns to step S1015. If completed, the process returns to step S1004, and accumulation by main exposure is performed again. Start again.

  Next, the AF process (LV_AF process) in step S1100 of FIG. 12 will be described with reference to FIG.

  In FIG. 13, in step S1101, the driving of the image sensor (sensor) 107 is switched to live view image display, which is sequential image display, and the process proceeds to step S1102.

  In step S1102, the camera control circuit 121 moves the focus lens 105 to a predetermined defocus position that is an AF start position based on the defocus amount calculated in step S1009, and the process proceeds to step S1103.

  In step S1103, the camera control circuit 121 determines whether or not the drive switching of the image sensor 107 is completed and the live view image display is possible. If the drive switching of the image sensor 107 is completed, the process proceeds to step S1104. .

  In step S1104, the camera control circuit 121 starts scan driving for driving the focus lens 105 at a constant speed, and proceeds to step S1105.

  In step S1105, the camera control circuit 121 drives the live view image display of the image sensor 107, sequentially performs accumulation and readout, and proceeds to step S1106 and step S1107.

  In step S1106, the camera control circuit 121 performs a phase difference detection type AF calculation using focus detection pixels to calculate a defocus amount, and the process advances to step S1108.

  In step S1108, the camera control circuit 121 determines whether focusing is possible based on the defocus amount calculated in step S1106. If focusing is possible, the process proceeds to step S1110. The process proceeds to step S1109.

  In step S1110, the camera control circuit 121 sets a standby time for adjusting the time between exposures by the inter-exposure time adjusting unit 121d, as in step S1011 of FIG. move on.

  On the other hand, in step S1107, the camera control circuit 121 generates a contrast evaluation value by the imaging pixel in parallel with the AF calculation by the focus detection pixel in step S1106, and the process proceeds to step S1109.

  In step S1109, the camera control circuit 121 determines whether the contrast evaluation value generated in step S1107 has acquired a peak value. If the contrast evaluation value has not acquired a peak value, the camera control circuit 121 returns to step S1104 and continues scan driving. Further, when the contrast evaluation value obtains a peak value, the camera control circuit 121 calculates a focus lens position (in-focus position) that is in focus based on the peak value of the contrast evaluation value and three points nearby. And proceed to step S1111.

  In step S <b> 1111, the camera control circuit 121 stops driving the focus lens 105 and proceeds to step S <b> 1112.

  In step S1112, the camera control circuit 121 moves the focus lens 105 to the in-focus position and returns to the main flow in FIG.

  As described above, in the present embodiment, in the imaging apparatus including the imaging element including the focus detection pixel and the imaging pixel, the continuous shooting time can be maintained and the exposure process can be performed. For this reason, it is possible to perform focus adjustment during continuous shooting and to reduce time fluctuation between main exposures during continuous shooting.

  In addition, this invention is not limited to what was illustrated to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. It can also be realized by executing software (program) acquired via a network or various storage media on a personal computer (CPU, processor).

DESCRIPTION OF SYMBOLS 100 Digital camera 105 Focus lens 107 Image pick-up element 121 Camera control circuit 121a Focus detection means 121b Contrast evaluation value generation means 121c Exposure processing means 121d Inter-exposure time adjustment means 126 Focus drive circuit

Claims (17)

Focus detection pixels that photoelectrically convert light beams that pass through different pairs of pupil areas in the exit pupil area of the imaging optical system and output a pair of image signals, and photoelectric conversion of light beams that pass through the exit pupil of the imaging optical system An image pickup apparatus including an image pickup element having an image pickup pixel that outputs an image signal,
Focus detection means for performing focus detection using an image signal of the focus detection pixel of the image sensor;
A focus adjusting means for adjusting the focus by driving a focus lens based on the detection result of the focus detecting means;
Exposure processing means for setting exposure conditions at the time of shooting;
Determining means for determining whether or not continuous shooting for sequentially exposing the image sensor;
Inter-exposure time adjustment that adjusts the time between exposures during continuous shooting based on the detection result of the focus detection unit and the exposure condition set by the exposure processing unit when the determination unit determines that continuous shooting is performed. And an imaging device.   The inter-exposure time adjustment means adjusts the time between exposures when the result of focus detection using the image signal of the focus detection pixel of the photographed image by the focus detection means is in focus. The imaging apparatus according to claim 1.   The inter-exposure time adjusting means is capable of focusing on a result of focus detection using the image signal of the focus detection pixel of the photographed image by the focus detection means, and an aperture of an exposure condition set by the exposure processing means The imaging apparatus according to claim 1, wherein the time adjustment between the exposures is performed when the value is within a predetermined range.   The inter-exposure time adjusting means is capable of focusing a result of focus detection using an image signal of the focus detection pixel of the photographed image by the focus detecting means, and ISO of an exposure condition set by the exposure processing means. The imaging apparatus according to claim 1, wherein time adjustment between the exposures is performed when the sensitivity is a value in a predetermined range.   The inter-exposure time adjusting means is capable of focusing a result of focus detection using an image signal of the focus detection pixel of the photographed image by the focus detection means, and an object with an exposure condition set by the exposure processing means The imaging apparatus according to claim 1, wherein the time adjustment between the exposures is performed when the brightness of the light falls within a predetermined range. Focus detection pixels that photoelectrically convert light beams that pass through different pairs of pupil areas in the exit pupil area of the imaging optical system and output a pair of image signals, and photoelectric conversion of light beams that pass through the exit pupil of the imaging optical system An image pickup apparatus including an image pickup element having an image pickup pixel that outputs an image signal,
First focus detection means for performing focus detection using an image signal of the focus detection pixel of the image sensor;
Second focus detection means for performing focus detection in a manner different from the first focus detection means;
Focus adjusting means for adjusting the focus by driving a focus lens based on the detection result of the first focus detecting means or the second focus detecting means;
Exposure processing means for setting exposure conditions at the time of shooting;
Determining means for determining whether or not continuous shooting for sequentially exposing the image sensor;
Exposure that adjusts the time between exposures in continuous shooting based on the detection result of the first focus detection unit and the exposure condition set by the exposure processing unit when the determination unit determines that continuous shooting is performed. An imaging apparatus comprising: an inter-time adjusting means.   The imaging apparatus according to claim 6, wherein the first focus detection unit performs focus detection using an image signal of the focus detection pixel of a captured image or a live view image.   The inter-exposure time adjusting means adjusts the inter-exposure time when the result of focus detection using the image signal of the focus detection pixel of the live view image by the first focus detection means is in focus. The imaging apparatus according to claim 6.   The inter-exposure time adjusting means can focus the result of focus detection using the image signal of the focus detection pixel of the live view image by the first focus detection means, and is set by the exposure processing means The imaging apparatus according to claim 6, wherein time adjustment between the exposures is performed when an aperture value of an exposure condition is within a predetermined range.   The inter-exposure time adjusting means can focus the result of focus detection using the image signal of the focus detection pixel of the live view image by the first focus detection means, and is set by the exposure processing means The imaging apparatus according to claim 6, wherein time adjustment between the exposures is performed when the ISO sensitivity of the exposure condition is a value in a predetermined range.   The inter-exposure time adjusting means can focus the result of focus detection using the image signal of the focus detection pixel of the live view image by the first focus detection means, and is set by the exposure processing means The imaging apparatus according to claim 6, wherein the time between exposures is adjusted when the brightness of the exposure condition is a value in a predetermined range. Focus detection pixels that photoelectrically convert light beams that pass through different pairs of pupil areas in the exit pupil area of the imaging optical system and output a pair of image signals, and photoelectric conversion of light beams that pass through the exit pupil of the imaging optical system A method for controlling an image pickup apparatus including an image pickup element having an image pickup pixel that outputs an image signal,
A focus detection step of performing focus detection using an image signal of the focus detection pixel of the image sensor;
A focus adjustment step of performing focus adjustment by driving a focus lens based on the detection result in the focus detection step;
An exposure processing step for setting exposure conditions during shooting,
A determination step of determining whether or not continuous shooting for sequentially exposing the image sensor;
When the continuous shooting is determined in the determination step, the time interval between exposures in the continuous shooting is adjusted based on the detection result in the focus detection step and the exposure condition set in the exposure processing step. A method for controlling the imaging apparatus, comprising: a time adjustment step. Focus detection pixels that photoelectrically convert light beams that pass through different pairs of pupil areas in the exit pupil area of the imaging optical system and output a pair of image signals, and photoelectric conversion of light beams that pass through the exit pupil of the imaging optical system A method for controlling an image pickup apparatus including an image pickup element having an image pickup pixel that outputs an image signal,
A first focus detection step of performing focus detection using an image signal of the focus detection pixel of the image sensor;
A second focus detection step for performing focus detection in a manner different from the first focus detection step;
A focus adjustment step of performing focus adjustment by driving a focus lens based on a detection result in the first focus detection step or the second focus detection step;
An exposure processing step for setting exposure conditions during shooting,
A determination step of determining whether or not continuous shooting for sequentially exposing the image sensor;
When it is determined in the determination step that continuous shooting is performed, time adjustment between exposures in continuous shooting is performed based on the detection result in the first focus detection step and the exposure condition set in the exposure processing step. And an inter-exposure time adjustment step to be performed.   A program for causing a computer to execute each step of the method for controlling an imaging apparatus according to claim 12.   A program for causing a computer to execute each step of the control method for an imaging apparatus according to claim 13.   A computer-readable storage medium, wherein the program according to claim 14 is stored.   A computer-readable storage medium storing the program according to claim 15.