JP2021131513A - Controller, imaging device, control method, and program - Google Patents

Abstract

To provide a controller which can detect a focus quickly with high accuracy.SOLUTION: Provided is a controller (121) for detecting a focus on the basis of a pixel signal obtained by photoelectrically converting the light passing through mutually different pupil areas of an imaging optical system. The controller comprises: an exposure control unit (121a) for exercising exposure control on the basis of an exposure control value that includes an exposure time, imaging sensitivity and aperture value: and an exposure condition acquisition unit (121b) for acquiring an exposure condition for focus detection on the basis of information based on a base line length. The exposure condition is an exposure condition that constitute a first exposure target value in information based on a first base line length and an exposure condition that constitutes a second exposure target value different from the first exposure target value in information based on a second base line length, and the exposure control unit exercises exposure control so that th exposure condition is established.SELECTED DRAWING: Figure 7

Description

The present invention relates to an imaging device.

A phase difference focus detection method (phase difference AF) is known as an automatic focus detection (AF) method for an image pickup apparatus. The phase-difference AF is an AF that is often used in digital still cameras, and there are some that use an image sensor as a focus detection sensor. Patent Document 1 discloses an image pickup device in which some pixels are used as focus detection pixels for performing pupil division type focus detection. In the case of such a focus detection method, the baseline length of the pair of focus detection pixels separated by pupil affects the focus detection accuracy.

Further, in general, when performing focus detection, it is necessary to set an exposure condition (exposure target value) at which an appropriate exposure is obtained. Therefore, when the exposure is not suitable for focus detection, the focus is detected by setting the exposure condition to be appropriate by the photometric means. In Patent Document 2, when the release button is half-pressed to perform focus detection, the presence / absence of light measurement and exposure conditions are described according to the reliability of the focus detection result immediately before the half-press so that the focus detection can be quickly performed. An imaging device for changing the setting of is disclosed.

Japanese Unexamined Patent Publication No. 2008-52009 Japanese Unexamined Patent Publication No. 2013-25132

The focus detection accuracy of phase-difference AF is determined by various factors such as the baseline length determined by the aperture diameter (F value) of the imaging optical system, the contrast of the subject, and the amount of signal acquired by the exposure setting. The baseline length changes according to the aperture diameter (F value) of the imaging optical system. Generally, as the F value increases, the baseline length decreases, so that the focus detection accuracy decreases. However, in the prior art, the presence / absence of metering and the exposure target value do not consider the baseline length that affects the focus detection accuracy of the phase difference AF, and the emphasis is on acquiring a constant signal amount by metering. There is. Therefore, if the baseline length is taken into consideration, even if the focus can be detected, there is a possibility that the focus cannot be detected quickly and accurately.

Therefore, an object of the present invention is to provide a control device, an image pickup device, a control method, and a program capable of quick and highly accurate focus detection.

The control device as one aspect of the present invention is a control device that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system, and is an exposure time and imaging sensitivity. , And an exposure control unit that performs exposure control based on the exposure control value including the aperture value, and an exposure condition acquisition unit that acquires the exposure condition for the focus detection based on the information based on the baseline length. The exposure condition is an exposure condition that is the first exposure target value in the information based on the first baseline length, and is different from the first exposure target value in the information based on the second baseline length. It is an exposure condition that is an exposure target value, and the exposure control unit performs the exposure control so as to be the exposure condition.

The control device as another aspect of the present invention is a control device that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system, and is an exposure time and imaging. At least at the time of the exposure control unit that controls the exposure based on the sensitivity and the exposure control value including the aperture value, the focus adjustment unit that adjusts the focus of the imaging optical system, and the focus adjustment by the focus adjustment unit. It has an exposure change determination unit that determines whether or not the exposure control needs to be performed based on the current brightness information and information based on the baseline length, and the exposure change determination unit is based on the information based on the first baseline length. The first exposure determination condition has a second exposure determination condition that is different from the first exposure determination condition in the information based on the second baseline length, and the exposure control unit has the exposure change determination unit. When it is determined that the control is to be performed, the exposure control is performed.

Other objects and features of the present invention will be described in the following embodiments.

According to the present invention, it is possible to provide a control device, an image pickup device, a control method, and a program capable of quick and highly accurate focus detection.

It is a block diagram of the image pickup apparatus in each embodiment. It is a figure which shows the pixel array in each embodiment. It is a figure which shows the pixel structure in each embodiment. It is explanatory drawing of the image sensor and pupil division function in each embodiment. It is explanatory drawing of the image sensor and pupil division function in each embodiment. It is a relationship diagram with the defocus amount and the image shift amount in each embodiment. It is a flowchart which shows the focus adjustment processing in 1st Embodiment. It is a figure which shows the exposure aim value in 1st Embodiment. It is a flowchart which shows the focus adjustment process in 2nd Embodiment. It is a timing chart in 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Each embodiment has a specific and specific configuration in order to facilitate understanding and explanation of the invention, but the present invention is not limited to such a specific configuration. For example, although the embodiment in which the present invention is applied to a single-lens reflex type digital camera having an interchangeable lens will be described below, the present invention can also be applied to a digital camera of a non-interchangeable lens type and a video camera. It can also be carried out on any electronic device equipped with a camera, such as a mobile phone, a personal computer (laptop, tablet, desktop type, etc.), a game machine, or the like.

(First Embodiment)
First, the schematic configuration of the image pickup apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the image pickup apparatus 100 according to the present embodiment. The image pickup apparatus 100 is a digital camera system including a camera body and an interchangeable lens (imaging optical system or imaging optical system) that can be attached to and detached from the camera body. However, the present embodiment is not limited to this, and can be applied to an imaging device in which a camera body and a lens are integrally configured.

The first lens group 101 is arranged in the frontmost position (subject side) of the plurality of lens groups constituting the photographing lens (imaging optical system), and can move forward and backward in the direction of the optical axis OA (optical axis direction). It is held in the lens barrel. The diaphragm combined shutter (aperture) 102 adjusts the amount of light at the time of shooting by adjusting the aperture diameter thereof, and also functions as a shutter for adjusting the exposure time at the time of shooting a still image. The second lens group 103 has a zoom function that advances and retreats in the optical axis direction integrally with the shutter 102 that also serves as an aperture, and performs a variable magnification operation in conjunction with the advance and retreat operation of the first lens group 101. The third lens group 105 is a focus lens group that adjusts the focus (focus operation) by moving forward and backward in the optical axis direction. The optical low-pass filter 106 is an optical element for reducing false color and moire of a captured image.

The image pickup device 107 performs photoelectric conversion of a subject image (optical image) via an image pickup optical system, and is composed of a two-dimensional photo sensor such as a CMOS sensor or a CCD sensor and peripheral circuits thereof, and forms an image of the image pickup optical system. Placed on the surface. As the image pickup element 107, for example, a two-dimensional single plate color sensor in which a Bayer-arranged primary color mosaic filter is formed on-chip on a light receiving pixel having m pixels in the horizontal direction and n pixels in the vertical direction is used. Be done.

The zoom actuator 111 performs a scaling operation by rotating (driving) a cam cylinder (not shown) to move the first lens group 101 to the second lens group 103 along the optical axis direction. The aperture shutter actuator 112 controls the aperture diameter of the aperture and shutter 102 to adjust the amount of light (captured light amount) and also controls the exposure time during still image photographing. The focus actuator 114 adjusts the focus by moving the third lens group 105 in the optical axis direction.

The electronic flash 115 is a lighting device used to illuminate a subject. As the electronic flash 115, a flash illumination device provided with a xenon tube or an illumination device provided with an LED (light emitting diode) that continuously emits light is used. The AF auxiliary light means 116 projects an image of a mask having a predetermined aperture pattern onto a subject via a light projecting lens. As a result, the focus detection ability for a dark subject or a low-contrast subject can be improved.

The CPU 121 is a control device (control means) that controls various controls of the image pickup device 100. The CPU 121 includes a calculation unit, a ROM, a RAM, an A / D converter, a D / A converter, a communication interface circuit, and the like. The CPU 121 drives various circuits of the image pickup apparatus 100 by reading and executing a predetermined program stored in the ROM, and controls a series of operations such as focus detection (AF), shooting, image processing, and recording. do. The communication interface circuit can perform not only communication using a cable such as USB or a wired LAN but also communication using a wireless technology such as a wireless LAN.

The CPU 121 is a control device that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system. The CPU 121 includes an exposure control unit 121a, an exposure condition acquisition unit 121b, a focus adjustment unit 121c, and an exposure change determination unit 121d. The exposure control unit 121a controls the exposure based on the exposure control value including the exposure time, the imaging sensitivity, and the aperture value. The exposure condition acquisition unit 121b acquires the exposure condition for focus detection based on the information based on the baseline length. The focus adjustment unit 121c controls the focus drive circuit 126 to perform focus adjustment (focus control) of the imaging optical system.

The CPU 121 stores a coefficient (correction value calculation coefficient) for calculating the correction value Kgain required for calculating the defocus amount in its internal memory. The correction value calculation coefficient is, for example, a focus state corresponding to the position of the third lens group 105, a zoom state corresponding to the position of the first lens group 101 to the second lens group 103, an F value of the image pickup optical system, and an image sensor. Multiple lenses are prepared for each set pupil distance and pixel size. When adjusting the focus, the CPU 121 is optimal according to the combination of the focus adjustment state (focus state, zoom state) and aperture value (F value) of the imaging optical system, the set pupil distance of the imaging element, and the pixel size. Select the correction value calculation coefficient. Then, the CPU 121 calculates the correction value based on the selected correction value calculation coefficient and the image height of the image sensor.

In the present embodiment, the correction value calculation coefficient is stored in the internal memory of the CPU 121, but is not limited to this. The correction value calculation coefficient may be stored in a memory provided outside the CPU 121. Further, in the interchangeable lens type imaging device, the interchangeable lens having the imaging optical system may have a non-volatile memory, and the correction value calculation coefficient may be stored in the memory. In this case, the correction value calculation coefficient may be transmitted to the image pickup apparatus according to the focus adjustment state of the image pickup optical system.

The electronic flash control circuit 122 controls the lighting of the electronic flash 115 in synchronization with the shooting operation. The auxiliary light drive circuit 123 controls the lighting of the AF auxiliary light means 116 in synchronization with the focus detection operation. The image sensor drive circuit 124 controls image pickup operations such as vertical and horizontal scanning of the image sensor 107, and A / D-converts the acquired image signal and transmits it to the CPU 121. The A / D conversion circuit may be provided in the image sensor 107. The image processing circuit 125 performs processing such as γ (gamma) conversion, color interpolation, and JPEG (Joint Photographic Experts Group) compression of the image data output from the image sensor 107.

The focus drive circuit 126 drives the focus actuator 114 based on the focus detection result, and adjusts the focus by moving the third lens group 105 along the optical axis direction. The aperture shutter drive circuit 128 drives the aperture shutter actuator 112 to control the aperture diameter 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 configured to include, for example, an LCD (liquid crystal display). The display 131 displays information about the shooting mode of the image pickup apparatus 100, a preview image before shooting, a confirmation image after shooting, an in-focus state display image at the time of focus detection, and the like. The operation unit (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 release switch has a two-stage switch of a half-pressed state (SW1 is ON state) and a full-pressed state (SW2 is ON state). The recording medium 133 is, for example, a flash memory that can be attached to and detached from the image pickup apparatus 100, and records captured images (image data). Further, the operation unit 132 may include a touch panel or the like so that the operation unit 132 can be operated using the touch panel.

Next, the pixel arrangement and the pixel structure of the image pickup device 107 in the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing a pixel arrangement of the image sensor 107. FIG. 3 is a diagram showing a pixel structure of the image sensor 107, FIG. 3 (a) is a plan view (viewed from the + z direction) of the pixel 200G of the image sensor 107, and FIG. 3 (b) is FIG. 3 (a). ) Are cross-sectional views (viewed from the −y direction) of lines aa.

FIG. 2 shows the pixel arrangement (arrangement of photographing pixels) of the image sensor (two-dimensional CMOS sensor) 107 in the range of 4 columns × 4 rows. In the present embodiment, each imaging pixel (pixels 200R, 200G, 200B) is composed of two sub-pixels 201 and 202 (two focus detection pixels). Therefore, in FIG. 2, the arrangement of the sub-pixels is shown in the range of 8 columns × 4 rows.

As shown in FIG. 2, in the pixel group 200 of 2 columns × 2 rows, pixels 200R, 200G, and 200B are arranged in a Bayer array. That is, among the pixel group 200, the pixel 200R having the spectral sensitivity of R (red) is in the upper left, the pixel 200G having the spectral sensitivity of G (green) is in the upper right and the lower left, and the pixel 200B having the spectral sensitivity of B (blue). Are placed in the lower right corner. Each pixel 200R, 200G, 200B (each imaging pixel) is composed of a sub-pixel 201 (first focus detection pixel) and a sub-pixel 202 (second focus detection pixel) arranged in two columns × one row. The sub-pixel 201 is a pixel that receives the light flux that has passed through the first pupil portion region of the imaging optical system. The sub-pixel 202 is a pixel that receives the light flux that has passed through the second pupil portion region of the imaging optical system. The plurality of sub-pixels 201 form the first pixel group, and the plurality of sub-pixels 202 form the second pixel group. The image sensor 107 is configured by arranging a large number of imaging pixels (8 columns × 4 rows of sub-pixels) in 4 columns × 4 rows on a surface, and outputs an imaging signal (sub-pixel signal or focus detection signal). ..

As shown in FIG. 3B, the pixel 200G of the present embodiment is provided with a microlens 305 for condensing incident light on the light receiving surface side of the pixel. A plurality of microlenses 305 are arranged two-dimensionally, and are arranged at positions separated by a predetermined distance in the z-axis direction (direction of the optical axis OA) from the light receiving surface. Also in the pixel 200G is, _{N H} divided in the x direction (divided into two), _{N V} division (first division) by photoelectric conversion unit 301 and the photoelectric conversion portion 302 is formed in the y-direction. The photoelectric conversion unit 301 and the photoelectric conversion unit 302 correspond to the sub-pixel 201 and the sub-pixel 202, respectively. As described above, the image sensor 107 has a plurality of photoelectric conversion units for one microlens, and the microlenses are arranged two-dimensionally. The photoelectric conversion unit 301 and the photoelectric conversion unit 302 are each configured as a pin-structured photodiode in which an intrinsic layer is sandwiched between a p-type layer and an n-type layer. If necessary, the intrinsic layer may be omitted and the photodiode may be configured as a pn junction.

In the pixel 200G (each pixel), a G (green) color filter 306 is provided between the microlens 305 and the photoelectric conversion unit 301 and the photoelectric conversion unit 302. Similarly, the pixels 200R and 200B (each pixel) are provided with R (red) and B (blue) color filters 306 between the microlens 305 and the photoelectric conversion unit 301 and the photoelectric conversion unit 302, respectively. .. If necessary, the spectral transmittance of the color filter 306 can be changed for each sub-pixel, or the color filter may be omitted.

As shown in FIG. 3, the light incident on the pixels 200G (200R, 200B) is collected by the microlens 305, separated by the G color filter 306 (R, B color filter 306), and then photoelectric. Light is received by the conversion unit 301 and the photoelectric conversion unit 302. In the photoelectric conversion unit 301 and the photoelectric conversion unit 302, pairs of electrons and holes are generated according to the amount of light received, and after they are separated by the depletion layer, negatively charged electrons are accumulated in the n-type layer. On the other hand, the hole is discharged to the outside of the image sensor 107 through a p-type layer connected to a constant voltage source (not shown). The electrons accumulated in the photoelectric conversion unit 301 and the n-type layer of the photoelectric conversion unit 302 are transferred to the capacitance unit (FD) via the transfer gate based on the scanning control by the image pickup element drive circuit 124, and the voltage is transferred. Converted to a signal.

Next, the pupil division function of the image pickup device 107 will be described with reference to FIG. FIG. 4 is an explanatory diagram of the pupil division function of the image sensor 107, and shows the state of pupil division in one pixel portion. FIG. 4 shows a cross-sectional view of the aa cross section of the pixel structure shown in FIG. 3A as viewed from the + y side, and the exit pupil surface of the imaging optical system. In FIG. 4, the x-axis and the y-axis of the cross-sectional view are inverted with respect to the x-axis and the y-axis of FIG. 3, respectively, in order to correspond to the coordinate axes of the exit pupil surface.

In FIG. 4, the pupil portion region (first pupil portion region) 501 of the sub-pixel (first focus detection pixel) 201 includes the light receiving surface of the photoelectric conversion unit 301 whose center of gravity is eccentric in the −x direction and the microlens 305. There is a substantially conjugated relationship through this. Therefore, the pupil region 501 represents the pupil region that can be received by the sub-pixel 201. The center of gravity of the pupil portion region 501 of the sub-pixel 201 is eccentric to the + X side on the pupil surface. Further, the pupil portion region (second pupil portion region) 502 of the sub-pixel (second focus detection pixel) 202 is omitted via the light receiving surface of the photoelectric conversion unit 302 whose center of gravity is eccentric in the + x direction and the microlens 305. It has a conjugate relationship. Therefore, the pupil region 502 represents a pupil region that can be received by the sub-pixel 202. The center of gravity of the pupil portion region 502 of the sub-pixel 202 is eccentric to the −X side on the pupil surface. The pupil region 500 is a pupil region in which light can be received by the entire pixel 200G when all the photoelectric conversion units 301 and 302 (sub-pixels 201 and 202) are combined.

The difference between the center of gravity of the pupil region 501 of the sub-pixel 201 and the center of gravity of the pupil region 502 of the sub-pixel 202 corresponds to the baseline length. The longer the baseline length, the higher the separation performance of the pair of signals. Here, since the baseline length becomes longer as the aperture diameter becomes larger, the focus detection accuracy becomes higher as the F value becomes smaller. On the other hand, the smaller the aperture diameter, the shorter the baseline length, and the larger the F-number, the lower the focus detection accuracy.

Next, the correspondence between the image pickup device 107 and the pupil division will be described with reference to FIG. FIG. 5 is an explanatory diagram of the image sensor 107 and the pupil division function. Luminous fluxes that have passed through different pupil regions 501 and 502 of the pupil regions of the imaging optical system are incident on the imaging surface 800 of the imaging element 107 at different angles to each pixel of the imaging element 107, and are divided into 2 × 1. The light is received by the sub-pixels 201 and 202. In the present embodiment, an example in which the pupil region is divided into two in the horizontal direction is described, but the present invention is not limited to this, and the pupil region may be divided in the vertical direction if necessary. ..

In the present embodiment, the image pickup element 107 has a first focus detection pixel that receives a light flux passing through a first pupil portion region that receives a light flux passing through a first pupil portion region of an imaging optical system (photographing lens). Further, the image pickup device 107 has a second focus detection pixel that receives a light beam passing through a second pupil portion region different from the first pupil portion region of the image pickup optical system. Further, the image pickup device 107 is arranged with a plurality of imaging pixels that receive a light beam passing through a pupil region that is a combination of the first pupil portion region and the second pupil portion region of the imaging optical system. In the present embodiment, each imaging pixel (pixel 200) is composed of a first focus detection pixel (sub-pixel 201) and a second focus detection pixel (sub-pixel 202). If necessary, the imaging pixel, the first focus detection pixel, and the second focus detection pixel may be composed of separate pixels. At this time, the first focus detection pixel and the second focus detection pixel are configured to be partially (discretely) arranged in a part of the imaging pixel array.

In the present embodiment, the image pickup device 100 collects the light receiving signals of the first focus detection pixels (secondary focus detection pixels 201) of each pixel of the image pickup element 107 to generate a first focus detection signal, and the second focus detection pixel of each pixel. The received signal of (sub-pixel 202) is collected to generate a second focus detection signal to perform focus detection. Further, the image pickup device 100 adds (sums) the signals of the first focus detection pixel and the second focus detection pixel for each pixel of the image pickup element 107 to obtain an image pickup signal (image image) having a resolution of N effective pixels. To generate.

Next, with reference to FIG. 6, the relationship between the defocus amount and the image shift amount of the first focus detection signal acquired from the sub-pixel 201 of the image sensor 107 and the second focus detection signal acquired from the sub-pixel 202. Will be described. FIG. 6 is a diagram showing the relationship between the defocus amount and the image shift amount. In FIG. 6, the image pickup device 107 is arranged on the image pickup surface 800, and similarly to FIGS. 4 and 5, it is shown that the exit pupil of the image pickup optical system is divided into two pupil region regions 501 and 502. There is.

For the defocus amount d, the distance from the imaging position of the subject to the imaging surface 800 is | d |, the front pin state in which the imaging position is closer to the subject than the imaging surface 800 is a negative sign (d <0), and imaging is performed. The rear pin state in which the position is on the opposite side of the subject from the imaging surface 800 is defined as a positive sign (d> 0). The defocus amount d = 0 is established in the focused state in which the imaging position of the subject is on the imaging surface 800 (focusing position). In FIG. 6, the subject 801 in the in-focus state (d = 0) and the subject 802 in the front pin state (d <0) are shown, respectively. The front pin state (d <0) and the rear pin state (d> 0) are collectively referred to as a defocus state (| d |> 0).

In the front pin state (d <0), among the luminous fluxes from the subject 802, the luminous flux that has passed through the pupil region 501 (or the pupil region 502) is once focused. After that, the luminous flux spreads over the width Γ1 (Γ2) centered on the center of gravity position G1 (G2) of the luminous flux, and the image becomes blurred on the imaging surface 800. The blurred image is received by the sub-pixel 201 (sub-pixel 202) constituting each pixel arranged in the image sensor 107, and the first focus detection signal (second focus detection signal) is generated. Therefore, the first focus detection signal (second focus detection signal) is recorded at the center of gravity position G1 (G2) on the imaging surface 800 as a subject image in which the subject 802 is blurred to the width Γ1 (Γ2). The blur width Γ1 (Γ2) of the subject image increases substantially proportionally as the magnitude | d | of the defocus amount d increases. Similarly, the magnitude of the image shift amount p (= difference in the position of the center of gravity of the luminous flux G1-G2) of the subject image between the first focus detection signal and the second focus detection signal | p | is also the defocus amount d. As the magnitude | d | increases, it generally increases proportionally. The same applies to the rear focus state (d> 0), but the image shift direction of the subject image between the first focus detection signal and the second focus detection signal is opposite to that of the front focus state.

Therefore, in the present embodiment, the conversion coefficient K for converting the image shift amount p obtained in advance to the defocus amount d and the image of the subject image between the first focus detection signal and the second focus detection signal. It is possible to calculate the defocus amount d based on the deviation amount p. Then, when the defocus amount d = 0, the focus is achieved.

Since the conversion coefficient K is proportional to the reciprocal of the baseline length, the information is based on the baseline length. When calculating the image shift amount p, it is affected by the variation error due to the S / N of the acquired signal. If the variation error of the image shift amount p is constant, the smaller the conversion coefficient K, the smaller the variation. That is, the focus detection variation is smaller and the focusing accuracy is higher under the condition that the baseline length is long and the F value is small. However, the focus detection accuracy of phase-difference AF is not only determined by the baseline length, but also by the contrast of the subject and the amount of signal acquired by the exposure setting. In particular, if the S / N of the signal is increased by acquiring a large signal, the variation error at the time of calculating the image shift amount p is reduced. Therefore, the signal amount may be small under the condition that the baseline length is long and the F value is small, but it is preferable that the signal amount is large under the condition that the baseline length is short and the F value is large. Such a tendency becomes more remarkable in a low-contrast subject where it is difficult to improve the focus detection accuracy.

Next, with reference to FIG. 7, the flow of the focus adjustment process during the live view in the present embodiment will be described. FIG. 7 is a flowchart showing the focus adjustment process in the present embodiment. Each step of FIG. 7 is mainly executed by the CPU 121.

Focus adjustment processing starts when the release button is pressed halfway during live view. First, in step S701, the CPU 121 acquires the focus detection result. When the CPU 121 acquires the focus detection result during standby, the result immediately before the release button is half-pressed may be used. The focus adjustment process is not limited to the case where the focus adjustment process is started by pressing the release button halfway, and the focus adjustment process may be started by pressing the button to which the AF function is assigned.

Subsequently, in step S702, the CPU 121 determines whether or not the focus detection result acquired in step S701 is reliable (whether or not it is reliable). If it is determined that the focus detection result is reliable, the process proceeds to step S707. In step S707, the CPU 121 drives the lens (focus control) based on the focus detection result. On the other hand, if it is determined in step S702 that the focus detection result is unreliable, the process proceeds to step S703. In step S703, the CPU 121 acquires the luminance information by photometry.

Subsequently, in step S704, the CPU 121 (exposure condition acquisition unit 121a) acquires AF exposure conditions (exposure conditions suitable for AF). As described above, the focus detection accuracy of the phase difference AF depends on the baseline length. Therefore, as shown in FIG. 8, the image pickup apparatus 100 of the present embodiment has a condition setting table for setting an appropriate exposure condition (exposure target value) as AF according to the F value. FIG. 8 is a diagram in which a general exposure condition (exposure target value) is standardized as an appropriate exposure (image), and an appropriate exposure condition as AF is shown as an appropriate exposure (AF). In FIG. 8, the horizontal axis represents the F value and the vertical axis represents the exposure ratio. In the present embodiment, the S / N of the signal is increased by taking a signal larger than the conventional one in a range darker than F2.8, which is an F value that makes it difficult to obtain the baseline length.

Subsequently, in step S705, the CPU 121 (exposure control unit 121a) sets AF exposure conditions (exposure conditions that realize an exposure target value suitable for AF). In the present embodiment, the exposure conditions are, but are not limited to, an exposure time, an imaging sensitivity, and an aperture value (F value). The CPU 121 determines the exposure condition according to a program diagram prepared in advance based on the luminance information acquired in step S703 and the AF exposure condition acquired in step S704. Table 1 shows, as an example, a comparison in the case where the conventional suitable exposure (image) is 1/350 of the exposure time, the imaging sensitivity is 100, and the aperture value is F5.6 in the lens with the maximum aperture of F5.6. From FIG. 8, since the AF exposure condition (AF exposure target value) in the present embodiment is 1.4 times the appropriate exposure (image) in F5.6, it is appropriate to extend the exposure time by 1.4 times. Exposure (AF) conditions. In Table 1, the adjustment is made according to the exposure conditions, but the adjustment may be made according to the imaging sensitivity.

Subsequently, in step S706, the CPU 121 acquires the focus detection result based on the AF exposure condition (AF exposure target value) set in step S705. Here, when a reliable focus detection result is obtained, in step S707, the CPU 121 performs lens drive (focus control) based on the focus detection result acquired in step S706. On the other hand, if a reliable focus detection result cannot be obtained, in step S707, the CPU 121 drives the lens as a search.

If the subject brightness changes during the lens drive in step S707, the CPU 121 (exposure control unit 121a) may perform exposure control by photometry during the focus adjustment process. Also in the exposure control in this case, it is preferable to perform the exposure control suitable for AF.

As described above, in the present embodiment, the exposure condition acquisition unit 121b acquires the exposure condition for focus detection based on the information based on the baseline length. The exposure condition is an exposure condition that is the first exposure target value in the information based on the first baseline length, and is a second exposure target value different from the first exposure target value in the information based on the second baseline length. This is the exposure condition. Then, the exposure control unit 121a performs exposure control so as to obtain the exposure condition acquired by the exposure condition acquisition unit 121b.

Preferably, the first baseline length is shorter than the second baseline length, and the first exposure target value is higher than the second exposure target value (that is, the information based on the baseline length makes it difficult to obtain the baseline length. , High exposure under exposure conditions suitable for focus detection). Further, preferably, the exposure condition acquisition unit 121b acquires the exposure condition based on the information based on the contrast of the subject. Further, preferably, the exposure control unit 121a performs exposure control based on the change in the subject brightness while the focus adjustment unit 121c is performing the focus adjustment. Also preferably, the information based on the baseline length is a value proportional to the baseline length or a value proportional to the reciprocal of the baseline length. Further, preferably, the information based on the baseline length is the aperture value (F value), the image height, or the lens ID.

According to this embodiment, highly accurate focus detection can be performed by setting the exposure condition (exposure aim value) based on the information based on the baseline length. In the present embodiment, since there is a correlation between the baseline length and Fno (aperture value), focusing accuracy can be improved by changing the exposure condition according to Fno as information based on the baseline length. The focusing accuracy of the phase difference AF also depends on the contrast of the subject. Therefore, for example, when the contrast is high, the conventional appropriate exposure (image) condition may be set, and when the contrast is low, the AF may be set as the appropriate exposure condition. To calculate the contrast of the subject, there is a method of observing the change in brightness in the imaging signal and the spatial frequency component of the subject.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In an image pickup device provided with an electronic display device such as a rear liquid crystal display or an electronic viewfinder, an electric signal received by the image pickup device is displayed on the electronic display device. Further, the electric signal may also serve as a signal for imaging surface phase-difference AF. Therefore, if the exposure setting is changed when the focus adjustment process is started by pressing the release button halfway, the electronic display device may become brighter or darker, and the visibility may be impaired. In the present embodiment, the condition (exposure determination condition) for determining the necessity of performing exposure control based on the value of the conversion coefficient K is changed as the information based on the baseline length, and the phase difference AF with good visibility and high accuracy is changed. To realize.

The problem of visibility due to the change of the exposure setting when the focus adjustment process is started can be improved by reducing the frequency of the exposure change. For example, even if the exposure immediately before the start of the focus adjustment process is two steps lower than the appropriate one, the decrease in visibility can be avoided by omitting the exposure change and starting the focus adjustment process if the distance can be measured.

As described above, the baseline length has a great influence on the distance measurement performance of the phase-difference AF. If the baseline length is long, distance measurement is possible even if the exposure is low. On the other hand, if the baseline length cannot be long, distance measurement may not be possible if the exposure remains low.

Therefore, in the present embodiment, the condition (exposure determination condition) for determining the necessity of performing exposure control based on the value of the conversion coefficient K is changed as the information based on the baseline length, and AF with good visibility and high accuracy is performed. Realize. More specifically, the smaller the value of the conversion coefficient K, the more visible and highly accurate phase-difference AF is realized by allowing distance measurement at an exposure lower than appropriate.

The flow of the focus adjustment process during the live view in the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing the focus adjustment process in the present embodiment. Each step of FIG. 9 is mainly executed by the CPU 121.

Focus adjustment processing starts when the release button is pressed halfway during live view. First, in step S901, the CPU 121 acquires the focus detection result. When the CPU 121 acquires the focus detection result during standby, the result immediately before the release button is half-pressed may be used. The focus adjustment process is not limited to the case where the focus adjustment process is started by pressing the release button halfway, and the focus adjustment process may be started by pressing the button to which the AF function is assigned.

Subsequently, in step S902, the CPU 121 determines whether or not the focus detection result acquired in step S901 is reliable (whether or not it is reliable). If it is determined that the focus detection result is reliable, the process proceeds to step S907. In step S907, the CPU 121 drives the lens (focus control) based on the focus detection result. On the other hand, if it is determined in step S902 that the focus detection result is unreliable, the process proceeds to step S903. In step S903, the CPU 121 acquires the luminance information by photometry.

Subsequently, in step S904, the CPU 121 acquires an exposure control determination condition (determination condition for whether or not to change the exposure). In the present embodiment, the exposure control determination condition is changed based on the conversion coefficient K. The CPU 121 acquires, for example, the conditions shown in Table 2, and acquires the conditions for whether or not to execute the exposure change in relation to the conversion coefficient K and the threshold value Thr0. When the conversion coefficient K is small (K <Thr0), the baseline length is long, so even if the difference between the current luminance information and the appropriate exposure (AF) is large, it is acceptable. On the other hand, when the conversion coefficient K is large (K ≧ Thr0), the baseline length is not long, so the width that allows the difference between the current luminance information and the appropriate exposure (AF) is reduced.

Subsequently, in step S905, the CPU 121 (exposure change determination unit 121d) determines whether or not to carry out the exposure change. That is, the CPU 121 determines whether or not to change the exposure based on the luminance information acquired in step S903, the conversion coefficient K acquired in step S904, and the exposure control determination condition. When the CPU 121 determines that the exposure change is not performed, the process proceeds to step S907, and the lens drive (search drive) is performed while maintaining the exposure. On the other hand, when the CPU 121 determines that the exposure change is to be performed, the CPU 121 proceeds to step S906. In step S906, the CPU 121 controls the exposure so as to change the exposure to an appropriate exposure (AF). Then, in step S907, the CPU 121 drives the lens.

As described above, the exposure change determination unit 121d determines whether or not the exposure control should be performed when the focus adjustment unit 121c adjusts the focus, at least based on the current luminance information and the information based on the baseline length. Further, the exposure change determination unit 121d sets the first exposure determination condition in the information based on the first baseline length, and the second exposure determination condition different from the first exposure determination condition in the information based on the second baseline length. Have. Then, when the exposure change determination unit 121d determines that the exposure control is to be performed, the exposure control unit 121a performs the exposure control. Preferably, the first baseline length is shorter than the second baseline length, and the first exposure determination condition is a determination condition for adjusting to an exposure condition more suitable for focus detection than the second exposure determination condition. ..

According to the present embodiment, by performing the focus detection process as described above, it is possible to reduce unnecessary exposure changes and realize highly accurate phase-difference AF with good visibility. Considering that the depth of field changes according to the aperture value, the threshold value Thr0 may be changed based on the aperture value. The exposure conditions include exposure time (tv), imaging sensitivity (ISO), and aperture value (Fno), but even if individual exposure conditions are changed, if the exposure is not changed, the exposure is maintained. .. For example, Tv = 1/240, ISO = 100, Fno = 2.0 and Tv = 1/60, ISO = 100, Fno = 4.0 are the same exposure target values.

The image pickup apparatus 100 of the present embodiment enables quick and highly accurate focus detection by setting the presence / absence of photometric measurement and the exposure condition (exposure target value) using the information based on the baseline length. The information based on the baseline length is Fno in the first embodiment and the conversion coefficient K in the present embodiment, but the determination is not limited to these, and the determination may be made based on, for example, the baseline length itself. Further, the image height and the lens ID can be used as the information based on the baseline length. The baseline length is determined by the relationship between the imaging optical system and the image sensor, but the higher the image height, the more difficult it is to obtain the baseline length due to the effect of pupil displacement. good. Further, in the case of an interchangeable lens system, since some lenses have a base line length that is easy to take and some lenses have a base line length that is difficult to take, the presence / absence of photometric measurement and the setting of exposure conditions may be changed by using the lens ID as information based on the base line length.

(Third Embodiment)
Next, a third embodiment of the present invention will be described. In the first embodiment and the second embodiment, a so-called one-shot mode in which the user presses the release button or the like halfway to perform focus detection has been described. However, the present invention realizes quick and highly accurate AF by considering the baseline length for exposure control during AF, and is not limited to one shot. The present invention can also be applied to each mode provided in the image pickup apparatus such as during continuous shooting, standby for moving images, and recording of moving images. In this embodiment, an example of applying the present invention during continuous shooting will be described.

FIG. 10 is an example of a timing chart during continuous shooting. In FIG. 10, the high resolution first image is used for recording a still image. The second image, which has a lower resolution than the first image, is displayed on an electronic display device such as a rear liquid crystal display or an electronic viewfinder, and is used for focus detection (focus adjustment processing) as a focus detection image.

The first image used for recording is preferably exposed with an appropriate exposure (image), and the second image used for focus detection is preferably exposed with an appropriate exposure (AF). In the present embodiment, as in the first embodiment, Fno is used as information based on the baseline length, and AF is performed at the exposure target value shown in FIG. Therefore, when continuous shooting is performed under conditions brighter than F2.8, the exposure target values of the first image and the second image are the same. On the other hand, when the aperture is narrowed down to F2.8, the exposure of the second image is higher than that of the first image.

As shown in FIG. 10, when the accumulation of the second image for focus detection is sandwiched between the first images used for recording, the second image is set to the appropriate exposure (AF). , Highly accurate focus detection is possible even during continuous shooting. Depending on the mode, the first image may serve as both a still image for recording and an image for focus detection. In this case, it is preferable to give priority to the exposure of the image for recording and to expose with an appropriate exposure (image). In addition, for moving images, frequent exposure changes during video recording may reduce the quality, so the appropriate exposure (AF) is adjusted during video standby, and the appropriate exposure (image) is adjusted during video recording. There is also a method of

The image pickup apparatus 100 of each embodiment enables quick and highly accurate focus detection by setting the presence / absence of light measurement and the exposure target value using the information based on the baseline length. The present invention can be applied to all products capable of performing phase-difference AF, and can be applied to distance measuring sensors and the like using a phase-difference structure in addition to the imaging device.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

According to each embodiment, it is possible to set the presence / absence of light measurement and the exposure target value by using the information based on the baseline length. Therefore, according to each embodiment, it is possible to provide a control device, an image pickup device, a control method, and a program capable of quick and highly accurate focus detection.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

121 CPU (control device)
121a Exposure control unit 121b Exposure condition acquisition unit

Claims (12)

It is a control device that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system.
An exposure control unit that controls exposure based on exposure control values including exposure time, imaging sensitivity, and aperture value.
It has an exposure condition acquisition unit that acquires an exposure condition for the focus detection based on information based on the baseline length.
The exposure condition is an exposure condition that is the first exposure target value in the information based on the first baseline length, and the second exposure different from the first exposure target value in the information based on the second baseline length. It is an exposure condition that is the target value,
The exposure control unit is a control device that controls the exposure so as to meet the exposure conditions. The first baseline length is shorter than the second baseline length.
The control device according to claim 1, wherein the first exposure target value is higher than the second exposure target value. The control device according to claim 1 or 2, wherein the exposure condition acquisition unit acquires the exposure condition based on information based on the contrast of the subject. It also has a focus adjustment unit that adjusts the focus of the imaging optical system.
The invention according to any one of claims 1 to 3, wherein the exposure control unit performs the exposure control based on a change in the subject brightness while the focus adjustment unit performs the focus adjustment. Control device. It is a control device that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system.
An exposure control unit that controls exposure based on exposure control values including exposure time, imaging sensitivity, and aperture value.
A focus adjustment unit that adjusts the focus of the imaging optical system,
It has an exposure change determination unit that determines whether or not the exposure control needs to be performed based on at least the current luminance information and the information based on the baseline length at the time of the focus adjustment by the focus adjustment unit.
The exposure change determination unit has a first exposure determination condition for information based on the first baseline length, and a second exposure determination condition different from the first exposure determination condition for information based on the second baseline length. death,
The exposure control unit is a control device that performs the exposure control when the exposure change determination unit determines that the exposure control is to be performed. The first baseline length is shorter than the second baseline length.
The control device according to claim 5, wherein the first exposure determination condition is a determination condition for adjusting to an exposure condition more suitable for the focus detection than the second exposure determination condition. The control device according to any one of claims 1 to 6, wherein the information based on the baseline length is a value proportional to the baseline length or a value proportional to the reciprocal of the baseline length. The control device according to any one of claims 1 to 7, wherein the information based on the baseline length is an aperture value, an image height, or a lens ID. An image sensor that outputs pixel signals by photoelectrically converting light that passes through different pupil regions of the image pickup optical system.
An imaging device comprising the control device according to any one of claims 1 to 8, which performs focus detection based on the pixel signal. It is a control method that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system.
An exposure control step that controls exposure based on exposure control values including exposure time, imaging sensitivity, and aperture value.
It has an exposure condition acquisition step of acquiring the exposure condition for the focus detection based on the information based on the baseline length.
The exposure condition is an exposure condition that is the first exposure target value in the information based on the first baseline length, and the second exposure different from the first exposure target value in the information based on the second baseline length. It is an exposure condition that is the target value,
A control method comprising performing the exposure control so as to meet the exposure conditions in the exposure control step. It is a control method that performs focus detection based on a pixel signal obtained by photoelectric conversion of light passing through different pupil regions of an imaging optical system.
An exposure control step that controls exposure based on exposure control values including exposure time, imaging sensitivity, and aperture value.
The focus adjustment step for adjusting the focus of the imaging optical system and
At the time of the focus adjustment, it has a determination step of determining whether or not the exposure control should be performed based on at least the current luminance information and the information based on the baseline length.
In the determination step, the information based on the first baseline length determines the necessity of implementation according to the first exposure determination condition, and the information based on the second baseline length is a second exposure determination condition different from the first exposure determination condition. Judging whether or not the implementation is necessary according to the exposure judgment conditions,
A control method comprising performing the exposure control in the exposure control step when it is determined in the determination step that the exposure control is to be performed. A program comprising causing a computer to execute the control method according to claim 10 or 11.

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