JP2020003672A - Imaging apparatus, accessory device, and control method thereof - Google Patents

Abstract

To reduce a probability that focus detection using auxiliary light is unsuccessful.SOLUTION: An imaging apparatus 100 performs the focus detection by using output from an imaging element 14 for capturing a subject image formed by an imaging optical system. When performing the focus detection, while driving a focus element, light-emitting means 48 is caused to start intermittent light emission according to the fact that a detection defocus amount obtained by the focus detection becomes a light emission start defocus amount. The light emission start defocus amount is set according to at least one of the focal distance of the imaging optical system and the drive speed of the focus element.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging device and the like that performs focus detection using an imaging element and auxiliary light.

  Patent Document 1 discloses an imaging apparatus that performs focus detection using a so-called imaging plane phase difference method using an imaging element. Patent Document 2 discloses a method of performing focus detection by emitting auxiliary light toward a subject when focus detection is difficult, such as when the subject is dark.

JP 2014-182360 A JP-A-6-94988

  However, when the focus detection is performed using the auxiliary light, the focus detection can be performed only while the auxiliary light is applied to the subject. For this reason, if the focus detection cannot be performed for some reason (unsuccessful) despite the emission of the auxiliary light, it is necessary to emit the auxiliary light again and perform the focus detection again. In particular, as disclosed in Patent Document 1, when focus detection is performed by an imaging surface phase difference detection method using an imaging element having a pair of photoelectric conversion units in each of a plurality of pixels, a pair of photoelectric conversion units is used. Since the base line length between the conversion units is short, the detectable defocus amount tends to be small. For this reason, even if the auxiliary light is used, the focus detection is likely to be unsuccessful.

  The present invention provides an imaging apparatus and the like that can reduce the probability of unsuccessful focus detection when performing focus detection using auxiliary light.

  An imaging device according to one aspect of the present invention includes an imaging element that captures a subject image formed by an imaging optical system, a focus detection unit that performs focus detection using an output from the imaging element, and control of the focus detection unit. And control means for controlling the driving of the focus element according to the result of the focus detection and for controlling the light emitting means for illuminating the subject. When the control means causes the focus detection means to perform focus detection while driving the focus element, the control means causes the light emission means to perform intermittent light emission in response to the detected defocus amount obtained by the focus detection becoming the light emission start defocus amount. To start. The light emission start defocus amount is set according to at least one of a focal length of an imaging optical system and a driving speed of the focus element.

  According to another aspect of the present invention, there is provided an imaging apparatus that captures a subject image formed by an imaging optical system, a focus detection unit that performs focus detection using an output from the imaging element, and a focus detection unit. Control means for controlling the means, controlling the driving of the focus element according to the result of focus detection, and controlling the light emitting means for illuminating the subject. The control means controls the focus detection means to perform focus detection while driving the focus element, and emits light every time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount. To emit light intermittently. The light emitting interval defocus amount is set according to at least one of a driving speed of the focus element, a detected defocus amount, the number of intermittent light emission of the light emitting unit, and a frame rate at which the imaging element is driven.

  Further, a control method according to another aspect of the present invention includes an imaging device that captures a subject image formed by an imaging optical system, performs focus detection using an output from the imaging device, and performs focus detection. The present invention is applied to an imaging apparatus that controls driving of a focus element and control of a light emitting unit that illuminates a subject according to a result. The control method includes the steps of: performing focus detection while driving the focus element; and performing intermittent light emission by the light emitting unit in response to the detected defocus amount obtained by the focus detection becoming the light emission start defocus amount in the focus detection. Is started. The light emission start defocus amount is set according to at least one of the focal length of the imaging optical system and the driving speed of the focus element.

Further, in the focus detection, the control method includes a step of intermittently illuminating the light emitting means so as to emit light every time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount. Is set according to at least one of the driving speed of the focus element, the detected defocus amount, the number of intermittent light emission of the light emitting unit, and the frame rate at which the imaging element is driven.
Note that a control program as a computer program that causes a computer of the imaging apparatus to execute a process according to the control method also constitutes another aspect of the present invention.

  According to the present invention, the probability that the focus detection using the auxiliary light is unsuccessful can be reduced.

FIG. 1 is a block diagram illustrating a configuration of an imaging device that is Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating pixels and a pixel array of an imaging element used in the imaging device according to the first embodiment. FIG. 3 is a diagram illustrating a conjugate relationship between an exit pupil plane of an imaging optical system and a photoelectric conversion unit of an imaging element in the imaging apparatus according to the first embodiment. FIG. 3 is a diagram illustrating a focus detection area provided in an imaging range in the first embodiment. FIG. 4 is a diagram illustrating a pair of phase difference image signals acquired in a focus detection area according to the first embodiment. 5 is a flowchart illustrating an imaging process according to the first embodiment. 5 is a flowchart illustrating focus adjustment processing according to the first embodiment. FIG. 4 is a diagram illustrating driving of a focus lens to an initial position according to the first embodiment. FIG. 4 is a diagram illustrating a table of defocus amount information that enables focus detection in the first embodiment. 6 is a flowchart illustrating an imaging process according to the first embodiment. 6 is a flowchart illustrating a process of determining whether or not to emit AF auxiliary light according to the first embodiment. 7 is a flowchart illustrating a focus adjustment process when the LED auxiliary light is emitted according to the first embodiment. 9 is a flowchart illustrating focus adjustment processing when the LED auxiliary light and the flash auxiliary light are emitted according to the first embodiment. 7 is a flowchart illustrating a subject presence / absence determination process according to the first embodiment. 6 is a flowchart illustrating focus adjustment processing when flash assist light is emitted in the first embodiment. 6 is a flowchart illustrating focus adjustment processing when flash assist light is emitted in the first embodiment. 5 is a flowchart illustrating focus detection / light control processing at the time of flash light emission according to the first embodiment. 5 is a flowchart showing a flash light emission condition setting process during driving of the lens according to the first embodiment. 6 is a flowchart showing flash light emission and focus detection processing during lens driving according to the first embodiment. 9 is a flowchart illustrating a flash light emission condition setting process during driving of the lens according to the second embodiment of the present invention. 9 is a flowchart illustrating a flash light emission condition setting process during driving of a lens according to a third embodiment of the present invention. 9 is a flowchart showing flash light emission and focus detection processing during lens driving in a third embodiment.

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

  FIG. 1 shows a camera system including an imaging lens (interchangeable lens) 300 and a camera body (hereinafter, simply referred to as a camera body) 100 as an imaging apparatus in which the imaging lens 300 is exchangeably (removably) mounted. The configuration is shown. First, the configuration of the camera 100 will be described.

  The lens mount 306 of the imaging lens 300 is mechanically and electrically detachably mounted on the camera mount 106 of the camera 100. The camera mount 106 and the lens mount 306 are provided with connectors 122 and 322 as electrical contacts for electrically connecting the imaging lens 300 to the camera 100.

  A light beam that enters the imaging lens 300 from a subject and passes through the imaging optical system in the imaging lens 300 is reflected upward by the main mirror 130 and enters the optical finder 104. The user can take an image while observing the subject image, which is an optical image of the subject, through the optical viewfinder 104. A part of a display unit 54 described later is provided in the optical finder 104, and the display unit 54 displays a focus detection area, a focused state, a camera shake warning, an aperture value, and an exposure correction value.

  The main mirror 130 is constituted by a half mirror. A part of the light beam incident on the main mirror 130 disposed in the imaging optical path passes through the main mirror 130, is reflected downward by the sub-mirror 131 provided behind the main mirror 130, and enters the focus detection unit 105.

  The focus detection unit 105 includes a secondary imaging optical system and a photoelectric conversion element, and performs focus detection by a phase difference detection method. The focus detection unit 105 converts a pair of subject images formed by the secondary imaging optical system into an electric signal (a phase difference image signal as a pair of focus detection signals) by a photoelectric conversion element such as a line sensor and performs AF ( (Auto focus) unit 42. The AF unit 42 calculates a phase difference which is a shift amount between the pair of phase difference image signals. The focus detection unit 105 and the AF unit 42 constitute a focus detection unit.

  The system control unit 50 as a control unit calculates a defocus amount as a focus detection result from the calculated phase difference. The focus control unit 342 performs a focus adjustment process of moving a focus lens (focus element) 311 included in the imaging optical system in the optical axis direction so as to reduce the defocus amount. In this embodiment, the focus adjustment is performed by moving the focus lens 311 in the imaging optical system. However, it is also possible to perform the focus adjustment by moving the image sensor 14 described later as a focus element in the optical axis direction.

  On the other hand, when a still image, an electronic finder image, or a moving image is captured after the focus adjustment processing of the imaging lens 300 ends, the main mirror 130 and the sub mirror 131 are retracted out of the imaging light beam by a quick return mechanism (not shown). Thereby, the light beam from the imaging lens 300 enters the imaging device 14 via the shutter 12 for controlling the exposure amount. The imaging element 14 is configured by a photoelectric conversion element such as a CMOS sensor, and captures (photoelectric conversion) a subject image formed by a light beam from the imaging lens 300. When the imaging is completed, the main mirror 130 and the sub mirror 131 are returned to the imaging optical path.

  The electric signal (analog image signal) generated by the photoelectric conversion in the image sensor 14 is converted into a digital image signal by the A / D converter 16. The timing generation unit 18 is controlled by the memory control unit 22 and the system control unit 50 to supply a clock signal and a control signal to the image sensor 14, the A / D converter 16, and the D / A converter 26. The image processing unit 20 performs image processing such as pixel interpolation processing and color conversion processing on the digital imaging signal from the A / D converter 16 or the memory control unit 22 to generate image data. The image processing unit 20 performs various arithmetic processes using the generated image data.

  The image sensor 14 is configured such that all or some of the pixels are focus-detectable pixels, and can perform focus detection by the imaging surface phase difference detection method using the pixels. The image processing unit 20 converts partial image data corresponding to a focus detection area described later in the generated image data into focus detection data. The focus detection data is sent to the AF unit 42 via the system control unit 50, and the AF unit 42 moves the focus lens 311 through the focus control unit 342 in the imaging lens 300 to obtain a focused state.

  In the camera 100 of the present embodiment, the system control unit 50 can generate a contrast evaluation value indicating a contrast state from the image data generated by the image processing unit 20. Then, it is also possible to perform AF by a contrast detection method in which the focus lens 311 is moved to a position where the contrast evaluation value indicates a peak through the focus control unit 342 to obtain a focused state.

  For this reason, in the optical finder observation state in which the main mirror 130 and the sub mirror 131 are arranged in the imaging optical path, AF (phase difference AF) is performed by the focus detection unit 105 in a phase difference detection method. On the other hand, in the electronic finder observation state in which the main mirror 130 and the sub-mirror 131 are retracted out of the image pickup light beam or in moving image pickup, the image pickup device 14 uses the image pickup surface phase difference detection method AF (image pickup surface phase difference AF) and the contrast detection method. AF (contrast AF) is performed.

  The memory control unit 22 controls the A / D converter 16, the timing generation unit 18, the image processing unit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression unit 32. As described above, digital image data from the A / D converter 16 is input to the image processing unit 20 to generate image data, and the image data is transmitted to the image display memory 24 or the memory 30 via the memory control unit 22. Is written to. The imaging data from the A / D converter 16 may be written directly to the image display memory 24 or the memory 30 via the memory control unit 22.

  The image display unit (display means) 28 has a display device such as a liquid crystal monitor. The display image data written in the image display memory 24 is displayed by the image display unit 28 via the D / A converter 26. By sequentially displaying image data (frame images) sequentially obtained by imaging on the image display unit 28, a live view image as an electronic finder image can be displayed.

  The memory 30 stores a still image or a moving image generated by imaging. The memory 30 is also used as a work area of the system control unit 50. The compression / decompression unit 32 has a function of compressing and decompressing image data by adaptive discrete cosine transform (ADCT) or the like, reads image data stored in the memory 30, performs compression or decompression processing, and processes the processed image. Write data to memory 30.

  The shutter control unit 36 controls the shutter 12 based on photometric information from the photometric unit 46 in cooperation with an aperture control unit 344 that drives an aperture 312 in the imaging lens 300. The camera interface unit 38 enables communication of control signals, status signals, various data, and the like between the camera 100 and the imaging lens 300 via the connectors 122 and 322 and the lens interface unit 338. In addition, power can be supplied from the camera 100 to the imaging lens 300.

  The photometric unit 46 performs an AE process. The luminance of the subject image can be measured by causing the light beam that has passed through the imaging lens 300 to enter the photometric unit 46 via the mirror 130 and a photometric lens (not shown). The photometric unit 46 performs a light control process in cooperation with the flash 48. The flash 48 is a light emitting unit (first light emitting unit) that emits light toward the subject, emits a flash (flash) when capturing a still image, illuminates the subject brightly, and emits light intermittently when focus is detected to intermittently emit light to the subject. It has a function of projecting AF auxiliary light to illuminate a subject.

  Note that, instead of the photometric unit 46, the system control unit 50 sends the shutter control unit 36 and the aperture control unit 344 in the imaging lens 300 based on the result of calculating the luminance from the image data generated by the image processing unit 20. It is also possible to perform AE control.

  The LED lamp 49 is a light emitting unit (second light emitting unit) capable of constantly emitting light (continuous emission) as a light source for illuminating the subject. The LED light emitted from the LED lamp 49 not only functions as LED auxiliary light, which is AF auxiliary light, but also reduces so-called red-eye effect and serves as an index of an imaging timing at the time of self-timer imaging.

  The system control unit 50 controls the entire operation of the camera 100. The memory 52 stores constants, variables, programs, and the like used for the operation of the system control unit 50. The display unit 54 is configured by a display device such as a liquid crystal display panel or an LED, and displays an operation state, a message, and the like using characters, images, sounds, and the like. More specifically, information on the number of captured images, such as the number of captured images and the number of remaining images that can be captured, information on imaging conditions such as shutter speed, aperture value, exposure correction, and presence or absence of flash emission, battery remaining amount and date・ Displays the time, etc. As described above, a part of the display unit 54 is also provided in the optical viewfinder 104.

  The non-volatile memory 56 is configured by an EEPROM or the like, and is an electrically recordable and erasable memory. The mode dial 60, the shutter switches 62 and 64, the image display on / off switch 66, the quick review on / off switch 68, and the operation unit 70 are operated by the user to input various operation instructions to the system control unit 50. You. The operation unit 70 includes a switch, a dial, a touch panel, a pointing device based on gaze detection, a voice recognition device, and the like.

  The power control unit 80 includes a battery detection unit, a DC / DC converter, and a switch unit that switches a block to be energized. The power control unit 80 detects whether or not a battery is installed, the type of the battery, and the remaining battery level through the battery detection unit, controls the DC / DC converter according to the detection result and an instruction from the system control unit 50, and Voltage is supplied to each part including the recording medium for a necessary period. The connectors 82 and 84 connect the camera 100 to a power supply unit 86 including a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, and a lithium ion battery, and an AC adapter.

  The interface 90 has a function of connecting to a recording medium 200 such as a memory card or a hard disk, and the connector 92 makes a physical connection to a recording medium such as a memory card or a hard disk. The recording medium attachment / detachment detection unit 98 detects that the recording medium 200 is connected to the connector 92.

  Next, the configuration of the imaging lens 300 will be described. The imaging lens 300 has an imaging optical system including a variable power (zoom) lens 310, the focus lens 311 described above, the stop 312, and the like. The zoom control unit 340 causes the zoom lens 310 to move in the optical axis direction to perform zooming. The focus control unit 342 as a focus adjusting unit moves the focus lens 311 in the optical axis direction to perform focus adjustment. The aperture control unit 344 drives the aperture 312 based on photometric information from the photometric unit 46 and the system control unit 50.

  The lens system control unit 346 controls the entire operation of the imaging lens 300. The lens system control unit 346 has a memory function for storing constants, variables, programs, and the like used for the operation.

  The non-volatile memory 348 stores identification information such as a serial number unique to the imaging lens 300, optical information such as an open aperture value, a minimum aperture value, and a focal length, and various current or past set values. Further, the nonvolatile memory 348 also stores frame information and defocus-related information according to the state of the imaging lens 300.

  The frame information is information on a “frame” that determines the diameter of a light beam passing through the imaging lens (imaging optical system) 300, and specifically, the distance of the “frame” from the image sensor 14 and the “frame” Is the information indicating the radius of the light beam passage opening of FIG. One of the “frames” is the stop 312, and the other lens holding member that holds the lens that forms the imaging optical system corresponds to the “frame”. Since the “frame” differs depending on the position of the zoom lens 310 (zoom position) and the position of the focus lens 311 (focus position), the “frame” is prepared for each zoom position and each focus position. When performing focus detection, optimal frame information according to the zoom position and the focus position is selected, and the frame information is transmitted from the lens control unit 346 to the system control unit 50.

  The defocus-related information is information on the defocus amount from the infinity end and the closest end for each subject distance, and is divided and stored for each subject distance associated with the focus position.

  Next, the configuration of the image sensor 14 will be described with reference to FIGS. FIG. 2A shows a configuration of one pixel 200 of the image sensor 14. The pixel 200 includes two photodiodes (PD) 201a and 201b as a pair of photoelectric conversion units, transfer switches 202a and 202b, a floating diffusion region 203, an amplification unit 204, a reset switch 205, and a selection switch 206. Having. Each switch is configured by a MOS transistor or the like. In the following description, as an example, it is assumed that each switch is configured by an N-type MOS transistor. However, each switch may be composed of a P-type MOS transistor, and may be composed of another switching element. Further, the number of photodiodes provided in the pixel 200 may be three or more (for example, four).

  As shown in FIG. 2B, each of the photodiodes 201a and 201b receives light passing through the same microlens 201c, performs photoelectric conversion, and generates electric charges according to the amount of received light. In the following description, a signal obtained by the charge generated by the photodiode 201a is called an A signal, and a signal obtained by the charge generated by the photodiode 201b is called a B signal.

  The transfer switch 202a is connected between the photodiode 201a and the floating diffusion region 203, and the transfer switch 202b is connected between the photodiode 201b and the floating diffusion region 203. The transfer switches 202a and 202b transfer charges generated in the photodiodes 201a and 201b to a common floating diffusion region 203, respectively. The transfer switches 202a and 202b are controlled by control signals TX_A and TX_B, respectively.

  The floating diffusion region 203 temporarily holds the charges transferred from the photodiodes 201a and 201b, and converts the held charges into a voltage signal.

  The amplifier 204 is a source follower MOS transistor. The gate of the amplification unit 204 is connected to the floating diffusion region 203, and the drain of the amplification unit 204 is connected to a common power supply 208 that supplies the power supply potential VDD. The amplifying unit 204 amplifies and outputs a voltage signal obtained from the charges held in the floating diffusion region 203.

  The reset switch 205 is connected between the floating diffusion region 203 and the common power supply 208. The reset switch 205 is controlled by the control signal RES, and resets the potential of the floating diffusion region 203 to the power supply potential VDD.

  The selection switch 206 is connected between the source of the amplification unit 204 and the vertical output line 207. The selection switch 206 is controlled by the control signal SEL, and outputs the voltage signal amplified by the amplifier 204 to the vertical output line 207.

  FIG. 2C shows a circuit configuration of the image sensor 14. The imaging device 14 includes a pixel array 234, a vertical scanning circuit 209, a current source load 210, a readout circuit 235, common output lines 228 and 229, a horizontal scanning circuit 232, and a data output unit 233.

The pixel array 234 has a plurality of pixels 200 arranged in a matrix. FIG. 2C shows n pixels in the horizontal direction × 4 pixels in the vertical direction for the sake of simplicity. Each pixel 200 is provided with one of a plurality of color filters. In the example shown in FIG. 2C, the colors of the color filters are red (R), green (G), and blue (B).
The n × m pixels provided with these color filters are arranged according to a Bayer arrangement.

  The image sensor 14 has a region (OB) in which a part of the pixel array 234 is shielded from light by a light-shielding layer.

  The vertical scanning circuit 209 outputs a control signal to the pixels 200 of each pixel row via a drive signal line 208 provided for each pixel row. In FIG. 2C, one drive signal line 208 is shown for each pixel row, but a plurality of drive signal lines are actually connected for each pixel row.

  Pixels 200 in the same pixel column are commonly connected to a vertical output line 207 provided for each pixel column. A signal output from each pixel 200 is input to the reading unit 235 via the vertical output line 207, and is processed by the reading unit 235. The current source load 210 is connected to the vertical output line 207 of each pixel column.

  By outputting the control signals HSR (0) to HSR (n-1), the horizontal scanning circuit 232 sequentially selects a reading unit to output a signal from among the plurality of reading units 235. The selected reading unit 235 outputs the processed signal to the output amplifier 233 via the common output lines 228 and 229.

  A specific configuration of the reading unit 235 will be described. The read unit 235 includes a clamp capacitor 211, feedback capacitors 214 to 216, an operational amplifier 213, a reference voltage source 212, and switches 217 to 220. Further, it has a comparator 221, Latch_N222, Latch_S223, and switches 226 and 227.

  A signal input to the reading unit 235 via the vertical output line 207 is input to an inverting input terminal of the operational amplifier 213 via the clamp capacitor 211. The reference voltage Vref is supplied from the reference voltage source 212 to the non-inverting input terminal of the operational amplifier 213. The feedback capacitors 214 to 216 are connected between the inverting input terminal and the output terminal of the operational amplifier 213. The switch 217 is also connected between the inverting input terminal and the output terminal of the operational amplifier 213, and shorts both ends of the feedback capacitors 214 to 216. Switch 217 is controlled by control signal RES_C. The switches 218 to 220 are controlled by control signals GAIN0 to GAIN2.

  The output terminal of the operational amplifier 213 and the ramp signal 224 output from the ramp signal generator 230 are connected to the comparator 221. Latch_N 222 is a storage element for holding a noise level (N signal), and Latch_S is a storage element for holding a signal level (S signal) of an A signal and an AB signal obtained by adding the A signal and the B signal. . The output terminal of the comparator 221 and the counter value 225 output from the counter 231 are input to Latch_N 222 and Latch_S 223, and are controlled by LATEN_N and LATEN_S, respectively. Output terminals of Latch_N and Latch_S are connected to common output lines 228 and 229 via switches 222 and 223, respectively. The common output lines 228 and 229 are connected to the data output unit 233.

  Switches 226 and 227 are controlled by control signal hsr (h) from horizontal scanning circuit 232. Here, h indicates the column number of the reading unit 235 to which the control signal line is connected. The signals held in Latch_N 222 and Latch_S 223 are output via common output lines 238 and 229 and output from data output unit 233 to the outside. This operation is called horizontal transfer.

  In the present embodiment, the image sensor 14 has a first read mode and a second read mode. The first reading mode is an all-pixel reading mode in which output signals are read from all pixels in order to capture a high-definition still image for recording. The second readout mode is a thinning-out readout in which only output signals from some of the pixels are read out to display a live view image or a moving image for recording, which has a smaller number of pixels than a still image for recording. Mode. Since the number of pixels required to generate a live view image or a moving image is smaller than the total number of pixels, the signal processing load can be reduced by reading output signals from only a small number of pixels in the horizontal and vertical directions at a predetermined ratio from the image sensor. In addition to reducing power consumption. In each of the first and second readout modes, the output signal from each photoelectric conversion unit provided for each pixel is read out independently, so that the generation of a pair of phase difference image signals is performed in any of the readout modes. Is possible.

  FIGS. 3A and 3B show pixels (hereinafter, referred to as pixels) arranged near the exit pupil plane of the imaging optical system 101 and near the image height 0 of the image sensor 14 in the camera system of the present embodiment, that is, near the center of the image plane. , A central pixel) 200 with a pair of photoelectric conversion units 201a, 201b. The exit pupil plane of the imaging optical system and the pair of photoelectric conversion units are set to have a conjugate relationship by the microlens 201c. The exit pupil of the imaging optical system is generally located on the surface where the stop 312 is arranged. On the other hand, the imaging optical system of the present embodiment has a zoom function, and the distance from the image plane to the exit pupil (exit pupil distance) and the size change according to the zooming. The imaging optical system 101 shown in FIG. 3A has a focal length in an intermediate zoom state between the wide-angle end and the telephoto end. Assuming this as a standard exit pupil distance Zep, the eccentricity parameter according to the shape and image height (X, Y coordinates) of the microlens 201c is optimized.

  In FIG. 3A, reference numeral 301 denotes a first lens group disposed closest to the subject in the imaging optical system, and reference numeral 301b denotes a lens barrel member that holds the first lens group 301. Reference numeral 311b denotes a lens barrel member that holds the focus lens 311. Reference numeral 312a denotes an aperture plate having an opening for determining the aperture of the aperture 312, and reference numeral 312b denotes aperture blades for adjusting the aperture of the aperture. The lens barrel member 301b, the aperture plate 312a, and the aperture blade 312b as members for restricting the light flux passing through the imaging optical system are shown as optical virtual images when observed from the image plane side. Further, the synthetic aperture near the stop 312 is defined as an exit pupil (hereinafter, referred to as a lens exit pupil) of the imaging optical system, and the distance from the image plane to the lens exit pupil is Zep as described above.

  The pair of photoelectric conversion units 201a and 201b included in the central pixel 200 are back-projected by the microlens 201c as images EP1a and EP1b onto the lens exit pupil plane. In other words, different pupil areas (hereinafter, referred to as focus detection pupils) EP1a and EP1b of the lens exit pupil are projected onto the surfaces of the photoelectric conversion units 201a and 201b via the microlenses 201c. The central pixel 200 includes, in order from the lowest layer, photoelectric conversion units 201a and 201b, wiring layers 201e to 201g, a color filter 201h, and a microlens 201c.

  FIG. 3B shows back-projected images EP1a and EP1b of the photoelectric conversion units 201a and 201b on the exit pupil plane of the imaging optical system as viewed from the optical axis direction. The imaging element 14 has a pixel that can output a signal from one of the two photoelectric conversion units 201a and 201b and that can add and output a signal from both of them. The signal output by the addition is a signal obtained by photoelectrically converting all the light beams that have passed through the focus detection pupils EP1a and EP1b.

  In FIG. 3A, the light beam L passing through the imaging optical system (the outer edge thereof is shown by a straight line) is limited by the aperture plate 312a of the stop 312, and the light beam from the focus detection pupils EP1a and EP1b. Reaches the pixel 200 without vignetting in the imaging optical system. In FIG. 3B, the cross section (outer edge) of the light beam L shown in FIG. 3A on the exit pupil plane is indicated as TL. Since most of the back-projected images EP1a and EP1b of the two photoelectric conversion units 201a and 201b are included in the circle indicated by TL (that is, the opening of the aperture plate 312a), the back-projected images EP1a and EP1b are included in the circle. Shows that only slight vignetting occurs. At this time, in the center of the exit pupil plane, the vignetting state of the back-projected images EP1a and EP1b is symmetric with respect to the optical axis of the imaging optical system (indicated by a dashed line in FIG. 3A), and the photoelectric conversion units 201a and 201b receive light. The amounts of light emitted are equal to each other.

  As described above, the imaging device 14 has not only a function of capturing an image of a subject, but also a function of individually receiving light beams from different focus detection pupils in the lens exit pupil and performing focus detection by an imaging surface phase difference detection method. . In the present embodiment, a case where one pixel of the image sensor 14 has a pair of photoelectric conversion units will be described. However, two focus detection-dedicated pixels, each of which is partly different from each other and shaded, are used as a pair of photoelectric conversion units. You may.

  FIG. 4 shows a focus detection area 401 within the imaging range 400. In the present embodiment, focus detection of the imaging surface phase difference detection method is performed in a plurality (three) of focus detection areas 401. In the focus detection area 401, a phase difference is detected using a horizontal contrast difference.

  FIG. 5 shows an example of a pair of phase difference image signals 430a and 430b in the present embodiment. The pair of phase difference image signals 430a and 430b connect A signals and B signals obtained from a plurality of pixels in the focus detection area 401 of the image sensor 14, respectively, and further perform various types of image processing ( (Correction). The pair of phase difference image signals 430a and 430b are sent to the AF unit 42.

  In FIG. 5, the horizontal axis indicates the pixel arrangement direction of the mutually connected signals (A or B signals), and the vertical axis indicates the intensity of the signals. FIG. 5 shows a pair of phase difference image signals 430a and 430b in a state where the imaging optical system is defocused on the subject (out of focus state). The phase difference image signal 430a is shifted to the left and the phase difference image signal 430b is shifted to the right as compared to the focused state. The AF unit 42 calculates a shift amount (phase difference) between the pair of phase difference image signals 430a and 430b using a correlation operation, and obtains a defocus amount for the subject in the imaging optical system from the phase difference.

  The system control unit 50 determines the focus lens 311 from the information on the focus sensitivity (image plane movement amount with respect to the unit movement amount of the focus lens 311) transmitted from the lens control unit 346 and the defocus amount obtained from the AF unit 42. Is calculated. Further, the system control unit 50 obtains information on a target position for moving the focus lens 311 from the information on the focus position transmitted from the lens control unit 346 and the driving amount of the focus lens 311, and transmits the information to the lens control unit 346. The lens control unit 346 moves the focus lens 311 to a target position for moving through the focus control unit 342. As described above, the focus adjustment by the imaging plane phase difference AF is performed.

  Next, an imaging control process (control method) in the camera 100 of the present embodiment will be described with reference to the flowchart of FIG. FIG. 6 shows a flow of an imaging control process when a still image is captured from a state in which a live view image is displayed. The system control unit 50 as a computer executes this processing according to a control program as a computer program. In the following description, “S” means a step.

  First, in S1, the system control unit 50 starts imaging by the imaging element 14 for generating a live view image, and inputs an imaging signal to the image processing unit 20.

  Next, in S2, the system control unit 50 causes the image processing unit 20 to generate live view image data and focus detection data from the imaging signal.

  Next, in S3, the system control unit 50 displays a live view image on the image display unit 28 based on the live view image data generated in S2. The user can determine the imaging composition by looking at the live view image. The display of the live view image is used by the user to confirm the imaging range and imaging conditions, and is updated at predetermined time intervals, for example, 33.3 ms (30 fps) or 16.6 ms (60 fps).

  However, the system control unit 50 may control the live view image not to be displayed on the image display unit 28 when the AF auxiliary light described below is emitted. For example, in the case of AF auxiliary light using flash light emission (hereinafter referred to as flash auxiliary light), there is a possibility that a high-quality image cannot be acquired due to saturation of a part of the subject or the like. The display of the view image may be stopped and then resumed.

  On the other hand, the AF auxiliary light emitted from the LED (hereinafter, referred to as LED auxiliary light) can emit light at all times, and the display image can be kept in an appropriate exposure state by the photometry unit 46. Therefore, it is not necessary to stop the display. Absent. Even when flash light emission is performed, the display of the live view image may be continued when the region where the luminance is saturated is limited or the flash light emission amount is small.

  Next, in S4, the system control unit 50 (AF unit 42) performs focus detection processing using the focus detection data in the three focus detection areas 401 shown in FIG. That is, the AF unit 42 performs focus detection processing until calculating the defocus amount from the phase difference between the pair of phase difference image signals shown in FIG.

  In the next S5, the system control unit 50 detects ON / OFF of the switch SW1 as an imaging preparation start instruction. The switch SW1 is turned on by half-pressing a release (imaging trigger) switch included in the operation unit 70. If the switch SW1 is on, the process proceeds to S10 if the S switch SW1 is off.

  In S10, the system control unit 50 determines whether the main (power) switch has been turned off. If the main switch has not been turned off, the process returns to S2. On the other hand, when the main switch is turned off, the present flow ends.

  On the other hand, if the switch SW1 is detected to be on in S5, the system control unit 50 proceeds to S6. In S6, the system control unit 50 acquires the focus detection area mode. The focus detection area mode includes an arbitrary selection mode, an automatic selection mode, and a subject detection mode. The optional mode is a mode in which one or a plurality of focus detection areas specified by the user are set. The automatic selection mode is a mode in which the system control unit 50 sets one or a plurality of focus detection areas. The subject detection mode is a mode for detecting a specific subject such as a human face and setting one or a plurality of focus detection areas. In step S6, the system control unit 50 acquires information on a focus detection area mode set in advance and subject detection information that is information on a specific subject such as a person's face, and acquires the position, location, and number of focus detection areas. Set.

  Next, in S7, the system control unit 50 (AF unit 42) performs focus adjustment processing in the focus detection area 401 set according to the focus detection area mode acquired in S6. Details of the focus adjustment processing will be described later. When the focus adjustment processing ends, the system control unit 50 proceeds to S8.

  In S8, the system control unit 50 detects ON / OFF of the switch SW2 as an imaging start instruction. The switch SW2 is turned on by fully pressing the release switch. The system control unit 50 waits until the switch SW2 is turned on, and proceeds to S9 when the switch SW2 is turned on.

  In S9, the system control unit 50 performs an imaging process. Details of the imaging process will be described later. When the imaging process in S9 ends, the system control unit 50 proceeds to S10.

In S10, the system control unit 50 determines whether the main switch has been turned off. If the main switch has not been turned off, the process returns to S2, and if the main switch has been turned off, this processing ends.

  Next, the focus adjustment processing performed in S7 of FIG. 6 will be described with reference to the flowchart of FIG. In S201, the system control unit 50 that has started the focus adjustment process acquires a defocus amount (hereinafter, referred to as a detected defocus amount) as a result of the focus detection performed in S4. Further, the system control unit 50 determines whether or not the reliability of the acquired detected defocus amount is high. If the reliability of the detected defocus amount is high, the system control unit 50 proceeds to S202.

Here, the reliability is determined by the system controller 50 that the minimum value of the correlation amount between the pair of phase difference image signals and the magnitude of the difference between the correlation amounts near the shift amount at which the correlation amount shows the minimum value in the correlation calculation. Is determined using

  The correlation amount indicates the degree of correlation between a pair of phase difference image signals. The higher the correlation, the smaller the value. In other words, the smaller the minimum value of the correlation amount, the higher the reliability. In the present embodiment, if the minimum value of the correlation amount is smaller than the threshold Thr1, it is determined that the reliability is high. Ideally, the minimum value of the correlation amount is 0 when the pair of phase difference image signals have completely the same shape. However, the actual pair of phase difference image signals have different shapes due to the diffusion characteristics of light from the subject, the light amount adjustment error, the influence of noise generated individually for each pixel, and the like. For this reason, the local minimum value of the correlation amount is generally a positive value. On the other hand, as the difference between the shapes of the pair of phase difference image signals increases, the detection accuracy of the minimum value decreases, and as a result, the accuracy of focus detection decreases.

  Also, the larger the difference between the correlation amounts obtained near the shift amount at which the correlation amount shows the minimum value, the more accurately the shift amount can be calculated. This is because, even when the correlation amount varies due to an error, if the difference between the correlation amounts is large, the influence on the shift amount detection is small. From this, it is determined that the reliability is high (first reliability) when the difference between the correlation amounts is larger than the threshold Thr2.

  In S202, the system control unit 50 determines whether a highly reliable detected defocus amount has been acquired in all the focus detection areas set according to the focus detection area mode acquired in S6. Then, if a highly reliable detected defocus amount can be obtained in all the focus detection areas, the process proceeds to S203. The process proceeds to S203 only when a highly reliable detection defocus amount can be acquired in all the focus detection regions set in S202. The reason is that some of the focus detection regions have higher reliability due to the emission of the AF auxiliary light. This is because there is a possibility. If there is a focus detection area in which the detected defocus amount with low reliability is obtained, the system control unit 50 attempts focus detection using the AF auxiliary light. However, when the number of focus detection areas is large, it is not necessary to use the AF auxiliary light only when the reliability of all the focus detection areas is high. For example, it may be determined that the AF auxiliary light is not used when the image height is high only in the focus detection area near the center of the plurality of focus detection areas.

  In S203, the system control unit 50 determines whether the detected defocus amount in the focus detection area 401 set in S6 indicates a focused state or an out-of-focus state where the detected defocus amount is equal to or less than a predetermined defocus amount. Here, among the focus detection areas set according to the focus detection area mode, one focus detection area is selected according to a predetermined algorithm of nearest priority and central area priority, and the detected defocus amount is compared with the predetermined amount. I do. The system control unit 50, which has determined that the state is out of focus, proceeds to S204, and drives the focus lens 311 based on the detected defocus amount.

  On the other hand, the system control unit 50, which has determined in S203 that the detected defocus amount is equal to or less than the predetermined defocus amount and is in focus, proceeds to S205, and performs in-focus display indicating the in-focus state on the image display unit 28. For example, a frame indicating the focus detection area in which the in-focus state has been obtained is displayed in a specific color, or a sound indicating that the in-focus state has been obtained is output.

  Further, the system control unit 50 that has determined in S202 that a highly reliable defocus amount has not been detected, proceeds to S206, and performs processing for determining whether or not to emit AF auxiliary light. Details of the processing will be described later.

  Next, in S207, the system control unit 50 determines whether or not the result of the determination processing in S206 indicates that the AF auxiliary light as the LED auxiliary light or the flash auxiliary light is necessary. If the AF auxiliary light is unnecessary, the system control unit 50 proceeds to S208.

  In S208, the system control unit 50 performs focus detection processing (second focus detection processing) while driving the focus lens 311, that is, performing search driving. The focus detection processing performed here is the same as the focus detection processing performed in S4. As a result of performing the search driving and the focus detection in S208, the system control unit 50 that has determined in S209 that the focus detection is possible proceeds to S203.

  On the other hand, in S210, the system control unit 50 that has determined that focus detection cannot be continued in S209 determines whether or not the focus lens 311 is located at the movable range end (telephoto end or closest end) in the optical axis direction. judge. If the focus lens 311 has not reached the end of the movable range, the process returns to S208, and the search driving and focus detection processing are continued.

  If the focus lens 311 has reached the end of the movable range in S210, the system control unit 50 determines that the subject that can be focused by the movement of the focus lens 311 does not exist at a position where the focus is within the movable range of the focus lens 311. Then, the process proceeds to S211.

  In S211, the system control unit 50 suspends the focus detection and causes the image display unit 28 to perform the out-of-focus determination display indicating that the in-focus state cannot be obtained.

  The system control unit 50 that determines that the AF auxiliary light is necessary in S207 proceeds to S212 and calculates an initial position of the focus lens 311 (hereinafter, referred to as a focus initial position). First, the system control unit 50 acquires focus detection information described later, and calculates a detectable defocus amount that is assumed to be capable of focus detection using the focus detection information. Further, the system control unit 50 can cover as wide a subject distance range as possible including the closest end from the detectable defocus amount and information on the subject distance at the closest end of the imaging lens 300 (defocus with high reliability). (The defocus range in which the amount can be calculated becomes as large as possible).

  FIG. 8 shows the focus initial position. The horizontal axis indicates the focus position corresponding to the subject distance to be focused. The calculated range of the detectable defocus amount (hereinafter, referred to as a defocus amount detectable range) is indicated by an arrow. The focus initial position is set such that the defocus amount detectable range extends to a farther side than the close end within the defocus amount detectable range including the closest end which is the movable range end of the focus lens 311. I have.

  The focus initial position is set within the defocus amount detectable range including the closest end, because the subject distance at which the AF auxiliary light reaches and the focus can be detected is short. For this reason, if the subject distance such as a constant multiple of the focal length or 1 m is set in advance as the distance at which the probability that the subject is present is high, the initial focus position is calculated so as to include the subject distance. Good. If a subject distance such as a constant multiple of the focal length or 1 m is set instead of the closest end, focus detection may not be performed on the closer subject, but focus detection is performed on the range of the far subject distance. It can be in the possible range.

  Alternatively, the reaching distance of the flash auxiliary light as the AF auxiliary light may be set, and the reaching distance may be set as the far end to set the initial focus position. As a result, the subject distance for focus detection can be limited, so that a more appropriate and initial focus position with a margin can be set.

  The focus detection information is information related to focus detection for estimating a detectable defocus amount, and includes an F value of the imaging lens 300, the above-described frame information, an image height and a phase difference image signal of a focus detection area where focus detection is performed. Is information on at least one of the contrasts. Based on the F value of the imaging lens 300, frame information, and information on the image height of the focus detection area, the base line length (center-of-gravity distance between the focus detection pupils) and the AF beam diameter (focus detection pupil) between a pair of photoelectric conversion units that perform focus detection Is calculated, the range through which the light beam forming the phase contrast image passes) is calculated. The longer the base line length is, the larger the amount of shift between the pair of phase difference image signals per unit defocus amount is, so that more accurate focus detection can be performed. In addition, the smaller the AF light beam diameter, the less the phase difference image signal is blurred due to defocusing, and the amount of displacement between a pair of phase difference image signals can be detected even in a large defocused state. Note that the larger the AF light beam diameter, the longer the base line length.

  In addition, the detectable defocus amount differs depending on the contrast of the subject, the spatial frequency characteristics, and the like. For a subject having a lot of information of a higher spatial frequency and having a high contrast, it is possible to perform focus detection even in a larger defocused state. The information on the contrast of the subject may be, for example, the sum of squares of the output differences between mutually adjacent pixel signals in the phase difference image signal.

  The system control unit 50 stores the information of the detectable defocus amount corresponding to the focus detection information described above in a table. FIG. 9 shows an example of a table of detectable defocus amounts. As described above, the system control unit 50 calculates the AF beam diameter and the contrast of the subject as the focus detection information, and acquires the detectable defocus amount from the table shown in FIG.

  Further, the reaching distance of the flash auxiliary light may be changed according to the AF light beam diameter. The smaller the AF beam diameter, the shorter the reach of the flash auxiliary light. Thereby, the focus initial position can be set more appropriately.

  The system control unit 50 that has calculated the focus initial position in S212 proceeds to S213, and moves the focus lens 311 to the calculated focus initial position.

  Next, in S214, the system control unit 50 determines whether emission of only the LED auxiliary light is permitted. In the present embodiment, the system control unit 50 controls the light emission of the flash 48 and the LED lamp 49 as the light emitting means of the AF auxiliary light. If only the LED auxiliary light is permitted to be emitted (if the emission of the flash auxiliary light is prohibited), the system control unit 50 proceeds to S215, and causes the LED lamp 49 to emit the LED auxiliary light to adjust the focus. Processing (hereinafter, referred to as LED focus adjustment processing) is performed. On the other hand, if the emission of the flash auxiliary light is permitted, the system control unit 50 proceeds to S216, emits the LED auxiliary light or the flash auxiliary light, and performs focus adjustment processing (hereinafter, referred to as LED / flash focus adjustment processing). )I do. Details of these focus adjustment processes will be described later. The system control unit 50 that has completed the LED focus adjustment processing in S215 or the LED / flash focus adjustment processing in S216 ends the focus adjustment processing.

  Next, the imaging process performed in S9 of FIG. 6 will be described with reference to the flowchart of FIG. First, in step S301, the system control unit 50 drives the diaphragm 312 to adjust the amount of light, and drives the mechanical shutter 12 that controls the exposure time. When performing imaging by flashing the flash 48, the system control unit 50 drives the mechanical shutter 12 in accordance with the timing of the light emission.

  Subsequently, in S302, the system control unit 50 reads out all pixels from the image sensor 14 for capturing a still image.

  Next, in step S303, the system control unit 50 (image processing unit 20) performs defective pixel interpolation on the image signal read from the image sensor 14 based on the position information of the defective pixel stored in advance. The defective pixel includes a pixel having a large variation in output offset and gain between pixels, and a pixel not used for imaging (such as the focus detection pixel described above).

  Next, in S304, the system control unit 50 performs image processing such as γ correction, color conversion, and edge enhancement on the imaging signal to generate captured image data (still image data). Then, in S305, the system control unit 50 records the captured image data in the memory 30.

  Subsequently, in step 306, the system control unit 50 records the characteristic information of the camera 100 in the memory 30 and the memory in the system control unit 50 in association with the captured image data recorded in S305. The characteristic information of the camera 100 is, for example, information on an exposure time, image processing at the time of development, a light receiving sensitivity distribution of pixels of the image sensor 14, and vignetting of an imaged light beam in the camera 100. Since the light receiving sensitivity distribution of the pixel is determined by the microlens 201c and the photodiodes 201a and 201b, information on the structure (the size and pitch of the photodiodes 201a and 201b, the distance from the microlens 201c, and the like) is recorded. Is also good. The characteristic information of the camera 100 also includes information on a distance from a mounting surface of the camera 100 and the imaging lens 300 to the imaging device 14 and information on a manufacturing error.

  Next, in S307, the system control unit 50 records the characteristic information of the imaging lens 300 in the memory 30 and the memory in the system control unit 50 in association with the captured image data recorded in S305. The characteristic information of the imaging lens 300 is, for example, information on an exit pupil, frame information, a focal length and F-number at the time of imaging, aberrations of the imaging optical system, and manufacturing errors.

  Next, in S308, the system control unit 50 records the image-related information on the captured image data in the memory 30 and the memory in the system control unit 50. The image-related information is, for example, information on a focus detection operation before imaging, movement of a subject, and information on accuracy of the focus detection operation. The system control unit 50 that has completed the processing of S307 proceeds to S10 of FIG.

  Next, with reference to the flowchart of FIG. 11, the determination of the necessity of emission of the AF auxiliary light performed in S206 of FIG. 7 will be described. In S401, the system control unit 50 acquires information on the focus detection area. Here, information such as the arrangement, position, and number of focus detection areas set according to the focus detection area mode in S6 of FIG. 6 is acquired.

  Next, in S402, the system control unit 50 acquires photometric information. Here, both the photometric value corresponding to each focus detection area and the photometric value of the area including all the focus detection areas are acquired.

  Next, in step S403, the system control unit 50 sets a threshold (hereinafter, referred to as a light emission threshold) for emitting the LED auxiliary light and the flash auxiliary light. The LED auxiliary light has a narrow irradiation range occupying the imaging range, but since it can always emit light, it is easy to perform focus detection while emitting light. On the other hand, since the flash auxiliary light emits intermittently with a wide irradiation range, if the flash auxiliary light is emitted a large number of times in focus detection, it may not be possible to secure a light emission amount at the time of imaging for image recording. For this reason, in S403, the system control unit 50 sets the light emission threshold so that the LED auxiliary light is easily emitted, but the flash auxiliary light is hardly emitted. However, in consideration of the focus detection error when the LED auxiliary light is monochromatic light such as red and the vignetting of the LED auxiliary light by the image pickup lens 300 due to the LED lamp 49 being arranged near the image pickup lens 300, the flashing is performed. The light emission threshold may be set so that the auxiliary light emits light more easily.

  Next, in S404, the system control unit 50 compares the photometric value indicated by the photometric information obtained in S402 with the light emission threshold of the LED auxiliary light obtained in S403. The photometric values used for the comparison here are the photometric value of the area including all the focus detection areas and the photometric value of each focus detection area. If any one of the photometric values is smaller than the light emission threshold value of the LED auxiliary light, the system control unit 50 proceeds to S405 and sets the LED light emission determination to ON (LED light emission permitted). On the other hand, if any one of the photometric values is equal to or greater than the light emission threshold value of the LED auxiliary light, the system control unit 50 proceeds to S406 and sets the LED light emission determination to off (LED light emission prohibited).

  Next, in step S407, the system control unit 50 compares the photometric value obtained in step S402 with the light emission threshold value of the flash auxiliary light obtained in step S403. Also in this case, the photometric value of the area including all the focus detection areas and the photometric value of each focus detection area are used. If any one of the photometric values is smaller than the light emission threshold value of the flash auxiliary light, the system control unit 50 proceeds to S408 and sets the flash light emission determination to ON (flash light emission permitted). On the other hand, if any one of the photometric values is equal to or greater than the flash auxiliary light emission threshold, the system control unit 50 proceeds to S409 and sets the flash emission determination to off (flash emission prohibited). The system control unit 50 that has completed S408 or S409 ends this processing.

  The light emission threshold value of the flash auxiliary light may be smaller than the light emission threshold value of the LED auxiliary light. Since the flash auxiliary light has a short light emission time as described later, by setting the frame rate of the image sensor 14 to a high frame rate (for example, 60 fps), the amount of external light to be taken in decreases. Therefore, it is necessary to emit the flash auxiliary light only at a light emission luminance that is less affected by external light. Since the built-in LED always emits light, the amount of light from the built-in LED can be received by increasing the accumulation time. From the above, the light emission threshold value of the flash auxiliary light is preferably set to a value smaller than the built-in LED.

  Next, the LED focus adjustment processing performed in S215 of FIG. 7 will be described using the flowchart of FIG. In S501, the system control unit 50 emits LED auxiliary light. The emission of the LED auxiliary light is continued at least until a focused state is obtained in S504 described later.

  The following processes from S502 to S510 are the same as the processes from S201 to S205 and S208 to S211 shown in FIG.

  Next, the LED / flash focus adjustment process performed in S216 of FIG. 7 will be described with reference to the flowchart of FIG. In step S <b> 601, the system control unit 50 determines whether only the flash auxiliary light has been permitted to be emitted in the emission necessity determination performed in advance. If the LED auxiliary light is not permitted and only the flash auxiliary light is permitted to emit light, the system control unit 50 proceeds to S605. If both the LED auxiliary light and the flash auxiliary light are permitted to emit light, the system control unit 50 proceeds to S602.

  In step S602, the system control unit 50 performs a process of determining the presence or absence of a subject. As described above, although the LED auxiliary light can always emit light, it has disadvantages that the irradiation range is narrow and that the imaging lens 300 is easily vignetted. Therefore, in S602, the system control unit 50 determines whether or not there is a subject for which the LED auxiliary light functions effectively. Details of the subject presence / absence determination processing will be described later.

  Next, in S603, the system control unit 50 determines whether or not it is determined that there is a subject for which the LED auxiliary light functions effectively. If so, the process proceeds to S604; otherwise, the process proceeds to S605.

  In S604, the system control unit 50 performs the same LED auxiliary light focus adjustment processing as in S215 of FIG. In S605, the system control unit 50 performs a flash focus adjustment process. Details of the flash focus adjustment processing will be described later. The system control unit 50 that has completed the processing of S604 or S605 ends the LED / flash focus adjustment processing.

  Next, the subject presence / absence determination processing performed in S602 of FIG. 13 will be described with reference to the flowchart of FIG. In S701, the system control unit 50 acquires photometric information of the focus detection area. Here, a photometric value corresponding to the focus detection area set in S6 of FIG. 6 is obtained.

  Next, in S702, the system control unit 50 emits the LED auxiliary light. Then, in S703, the system control unit 50 acquires a photometric value corresponding to the focus detection area again.

  Next, in S704, the system control unit 50 stops emitting the LED auxiliary light. Then, in S705, the system control unit 50 calculates the amount of change from the photometric value before emission of the LED auxiliary light obtained in S701 to the photometric value during LED emission obtained in S703. The system control unit 50 determines whether there is a subject in which the LED auxiliary light functions effectively, utilizing the fact that the photometric value changes due to the presence of the subject that can be illuminated by the LED auxiliary light. Thereby, when the position of the subject is out of the reach of the LED supplementary light, when the subject is not irradiated with the LED supplementary light due to vignetting of the imaging lens 300, when the subject is far away and the LED supplementary light does not reach, it is detected. be able to.

  As a method of determining the presence or absence of a subject, a method of performing focus detection during emission of LED auxiliary light and determining that a subject is present when focus detection is possible can be considered. However, in this method, when the subject is largely defocused, focus detection becomes impossible, and it may be determined that the subject does not exist even though the subject exists. Therefore, by performing the subject presence / absence determination using the change in the photometric information before and after the emission of the LED auxiliary light, it is possible to perform the appropriate subject presence / absence determination regardless of the defocus state.

  Next, in step S705, the system control unit 50 determines that there is a subject in which the LED auxiliary light functions effectively when the change in the photometric value corresponding to the focus detection area before and after the emission of the LED auxiliary light is equal to or greater than a predetermined value. judge. Then, the present process ends.

  Next, the flash focus adjustment process performed in S605 of FIG. 14 will be described with reference to FIGS. FIG. 15 shows a typical driving method of the focus lens 311 and emission timing of the flash auxiliary light when the flash auxiliary light is emitted. The horizontal axis indicates time, and the vertical axis indicates the focus (lens) position. FIG. 15 shows a change in the focus position when the focus lens 311 is driven from the focus adjustment start position to the focus position. The black circles in FIG. 15 indicate the timing at which the flash auxiliary light was emitted.

  First, the system control unit 50 emits the flash auxiliary light twice with the focus lens 311 stopped at the focus adjustment start position (F1). This is light emission for obtaining a defocus amount at the start of focus adjustment. The emission of flash auxiliary light (intermittent emission) performed with the focus lens 311 stopped is referred to as step flash emission in the following description. The focus detection accompanied by the step flash emission corresponds to a first focus detection process. The details of the two light emission operations will be described later.

  When the amount of defocus is detected by the emission of the flash auxiliary light of F1, the system control unit 50 starts driving the focus lens (time T1). When the focus position of the focus lens 311 is approaching after the start of the focus lens driving, the system control unit 50 emits the flash auxiliary light a plurality of times while continuing the focus lens driving (M1). That is, the flash auxiliary light is intermittently emitted. If the flash auxiliary light is always emitted while the focus lens is being driven, the required power will increase. Therefore, the system control unit 50 starts intermittent light emission in response to the focus lens 311 reaching a position determined using the defocus amount obtained before driving the focus lens. The intermittent light emission of the flash auxiliary light performed during driving of the focus lens is referred to as flash light emission during driving of the lens in the following description. The focus detection performed with flash light emission during driving of the lens corresponds to a second focus detection process.

  The system control unit 50 stops the focus lens 311 at the in-focus position based on the defocus amount obtained by the focus detection accompanied by flash emission during driving of the lens. After that, the system control unit 50 performs step flash emission again (F2), and confirms whether or not the operation is stopped within a predetermined focusing range. Thus, the flash focus adjustment processing ends.

  The flowchart of FIG. 16 shows the flash focus adjustment processing described above in more detail. In step S801, the system control unit 50 initializes a count value of the number of times of step flash emission. In the present embodiment, an upper limit is set for the number of times of the step flash emission to prevent unnecessary power consumption.

  Next, in step S802, the system control unit 50 performs focus detection (first focus detection processing) and light control while performing step flash emission. Here, the system control unit 50 performs dimming for setting the amount of flash light emission during lens driving while performing focus detection. In step S802, the system control unit 50 selects a focus detection area in which focus detection is to be performed later.

  Next, in S803, the system control unit 50 determines whether or not a focus detection result with high reliability (having a second reliability higher than the first reliability) has been obtained in S802. When a highly reliable focus detection result is not obtained (when the focus detection result has only the first reliability), the system control unit 50 proceeds to S804 and performs step flashing at all predetermined focus positions. It is determined whether or not focus detection with light emission has been completed.

  In this embodiment, as described above, the focus lens 311 is moved to the focus initial position in order to perform flash light emission. When it is impossible to detect the focus at the initial focus position, the system control unit 50 moves the focus lens 311 to the infinity side, stops the focus lens 311 and performs the focus detection with step flash emission again. The number of trials of focus detection involving step flash emission is arbitrary. For example, step flash emission can be performed for each defocus amount detectable range described above. In this case, the number of step flash emission becomes more than two. Further, after the light is emitted at the focus initial position, the step flash light emission may be performed from the infinite end position of the focus lens 311 on the close side by the defocus amount detectable range. In this case, the number of times of step flash emission when focus detection is impossible becomes a maximum of two times, and it is possible to determine whether or not focus adjustment can be performed more quickly.

  When the focus detection with the step flash emission has been completed at all the predetermined focus positions in S804, the system control unit 50 proceeds to S820, determines that the focus adjustment is impossible, and determines the out-of-focus state similarly to S211. Display. On the other hand, if the focus detection with the step flash emission has not been completed at all the predetermined focus positions in S804, the system control unit 50 drives the focus lens to the next focus position in S805. Then, the process returns to S802.

  The system control unit 50, which has determined in S803 that a highly reliable focus detection result has been obtained, proceeds to S806, and sets conditions for flash emission during lens driving. The conditions include a defocus amount at which light emission is started, a focus position (light emission start focus position), a driving speed of the focus lens 311 and the like, and details thereof will be described later.

  Next, in step S807, the system control unit 50 starts driving the focus lens according to the conditions set in step S806. In step S808, the system control unit 50 determines whether the focus lens 311 has passed the light emission start focus position set in step S806. If it has not passed yet, the system control unit 50 repeats the determination of S808 while driving the focus lens. On the other hand, when the focus lens 311 has passed the light emission start focus position, the system control unit 50 proceeds to S809 and performs focus detection accompanied by flash emission during lens driving (second focus detection processing). At this time, the system control unit 50 causes the flash emission to be performed in synchronization with the frame rate at which the image data is generated (driving the image sensor 14), and a pair of the focus detection areas obtained (selected) in S802 is obtained. Focus detection using the phase difference image signal is repeatedly performed. Details will be described later.

  Next, in S810, the system control unit 50 determines whether or not the number of flashes during driving the lens is equal to or less than a predetermined number. If the number exceeds the predetermined number, the process proceeds to S820, in which the focus detection is interrupted and the A focus determination display is performed. This is a process performed to prevent unnecessary light emission by regarding a subject detected before the start of focus lens driving as being lost due to the movement of the subject or framing of the user. If the number of flashes during driving of the lens is equal to or less than the predetermined number in S810, the system control unit 50 proceeds to S811.

  In S811, the system control unit 50 determines whether the obtained detected defocus amount is equal to or less than a predetermined defocus amount. If the detected defocus amount is larger than the predetermined defocus amount, the system control unit 50 returns to S809 and continues the processing. If the detected defocus amount is equal to or less than the predetermined defocus amount, the system control unit 50 proceeds to S812 and stops driving the focus lens.

  Then, in step S813, the system control unit 50 performs focus detection and light control while performing step flash emission (that is, performing intermittent light emission while the focus lens driving is stopped), as in step S802. The reason why the light adjustment processing is performed again near the in-focus position is to avoid performing focus detection using a pair of phase difference image signals saturated by a change in the defocus state. In particular, when the object includes a thin line, the blur becomes smaller as the focus changes from the blur state to the focused state, and the luminance level of the pair of phase difference image signals may increase and become saturated. Since a pair of saturated phase difference image signals causes a focus detection error, light adjustment processing is performed near the in-focus position.

  After S813, the system control unit 50 determines in S814 whether the detected defocus amount is smaller than the focus determination threshold. If it is smaller, the process proceeds to S815, in-focus display is performed in the same manner as in S205, and this processing ends.

  The system control unit 50 that has determined in S814 that the detected defocus amount is larger than the focus determination threshold value proceeds to S816, and drives the focus lens based on the detected defocus amount.

  After the end (stop) of the drive of the focus lens in S816, in S817, the system control unit 50 determines whether or not the number of times of the step flash emission is equal to or less than a predetermined number. Since the step flash emission is also performed before the start of the focus lens driving, the determination is made here based on the total number of times from before the start of the focus lens drive. If the number of times of step flash emission exceeds the predetermined number, the system control unit 50 proceeds to S820, interrupts the focus detection, and performs the out-of-focus determination display.

  On the other hand, when the number of times of step flash emission is equal to or less than the predetermined number, the system control unit 50 proceeds to S818, and performs the emission of the flash auxiliary light and the focus detection in which the light emission amount is set based on the previous dimming result.

  Subsequently, in S818, since it is assumed that the change in the defocus state from S813 is small, the system control unit 50 performs focus detection using the dimming result obtained in S813 without performing dimming again. . As a result, highly accurate focus detection can be realized without performing unnecessary light emission. If the defocus amount obtained in S813 is large and the defocus state is largely different from S818, the same processing as S813 may be performed again.

  Next, in S819, the system control unit 50 increments the number of times of step flash emission, and returns to S814.

  Next, with reference to the flowchart of FIG. 17, the focus detection and light adjustment processing involving flash light emission performed in S802 of FIG. 15 will be described. In step S901, the system control unit 50 performs focus detection and reliability determination of the focus detection result in one or more focus detection areas set in advance without performing flash light emission, and outputs a highly reliable focus detection result. Remember.

  Next, in S902, the system control unit 50 causes the flash emission to be performed at the first light emission amount, and in synchronization with this, the focus detection and the detection of the focus detection result are performed using the pair of phase difference image signals acquired from the image sensor 14. A reliability determination is performed, and a focus detection result with high reliability is selected and stored.

  Next, in step S <b> 903, the system control unit 50 causes a flash light emission to be performed at a second light emission amount larger than the first light emission amount, and uses a pair of phase difference image signals acquired from the image sensor 14 in synchronization with the flash light emission. The focus detection and the reliability determination of the focus detection result are performed. Then, a focus detection result with high reliability is selected and stored.

  Next, in step S904, the system control unit 50 sets a focus detection area to be used for focus adjustment from a plurality of focus detection areas using the focus detection results obtained in steps S901, S902, and S903. Specifically, for example, a focus detection area indicating the existence of the closest object is set as a focus detection area used for focus adjustment. This is because the main subject that the user intends to image is likely to be on the near distance side. However, the method of selecting a focus detection area used for focus adjustment is not limited to this. For example, averaging processing may be performed on a plurality of focus detection results having different flash light emission amounts, and a focus detection area used for focus adjustment may be set using the averaged focus detection results.

  In general, the higher the contrast of the pair of phase difference image signals, the higher the detection accuracy of the defocus amount. However, this is not the case when the pair of phase difference image signals are saturated as described above. Therefore, the saturation of the pair of phase difference image signals obtained in S902 and S903 may be detected, and the focus detection result obtained from the saturated signal may not be used.

  Next, in S905, the system control unit 50 performs a dimming process and acquires a dimming result. If the focus detection area set in S904 is the focus detection area corresponding to the focus detection result selected in S901, the system control unit 50 does not perform the light control processing. In the subsequent focus detection, the focus detection is performed without emitting the AF auxiliary light. On the other hand, when the focus detection area selected in S904 is the focus detection area corresponding to the focus detection result selected in S902 or S903, the light control processing is performed.

  Further, the system control unit 50 adds the light metering information in a state where flash light emission is not performed in the selected focus detection area and the flash light emission amount (first or second light emission amount) from which the selected focus detection result is obtained. The corresponding photometric information of the selected focus detection area is acquired. Then, a light emission amount necessary and sufficient for performing focus detection is calculated from the difference between these two photometric information.

A photometric value in a state where flash light emission is not performed is BV_n, a photometric value when flash light is emitted is BV_af, and a target photometric value necessary and sufficient for focus detection is BV_T. In this case, the reference light emission amount, that is, the gain G for the flash light emission amount at which the selected focus detection result is obtained is calculated by the following equation (1).
G = (BV_T-BV_n) / (BV_af-BV_n) (1)
Equation (1) shows a case where the photometric value is on a linear scale, but the photometric information is often on a logarithmic scale. In this case, the gain G may be calculated by performing conversion between a linear scale and a logarithmic scale. If the photometric value at the time of flash emission is out of the photometric range, the photometric value cannot be measured properly. For this reason, in the case of a photometric value having low reliability as a photometric value (for example, a photometric value of 5 steps or more and -5 steps or less of an appropriate exposure), clipping is performed at an upper limit or a lower limit of a highly reliable photometric value. The above calculation is performed using the value as a photometric value at the time of flash light emission.

  The system control unit 50 sets the subsequent light emission amount of the flash auxiliary light from the obtained gain G and the reference light emission amount. This makes it possible to set an appropriate light emission amount, to suppress unnecessary power consumption, and to prevent a decrease in focus detection accuracy due to saturation of the pair of phase difference image signals. If the appropriate amount of light emission is larger than the upper limit of the amount of light emission possible with the flash auxiliary light, the ISO sensitivity of the image sensor is increased to adjust the phase difference image signal to an appropriate amount.

  The system control unit 50 that has finished acquiring the dimming result in step S905 proceeds to step S906, increments the number of times of step flash emission, and ends this processing.

  Next, with reference to the flowchart of FIG. 18, a description will be given of the flash drive emission condition setting processing during lens driving performed in S806 of FIG. 16. The system control unit 50 acquires the information on the focal length of the imaging lens in S1001, and proceeds to S1002.

  In step S1002, the system control unit 50 determines whether the focal length acquired in step S1001 is equal to or larger than a predetermined value (for example, 100 mm). If the focal length is equal to or larger than the predetermined value, the process proceeds to step S1003; Proceed to.

  In S1003, the system control unit 50 sets the first defocus amount as the light emission start defocus amount, and sets the second defocus amount smaller than the first defocus amount as the light emission start defocus amount in S1004. Then, the process proceeds to S1005.

  In this embodiment, the light emission start defocus position is set according to the focal length of the imaging lens. An imaging lens having a long focal length generally has a wide defocus range from an infinity end to a close end, so that the driving speed of the focus lens is high. On the other hand, an imaging lens having a short focal length has a narrow defocus range, and thus the driving speed of the focus lens is low. For this reason, in the present embodiment, when the focal length of the imaging lens is equal to or longer than a predetermined value, the first defocus amount is set as the light emission start defocus amount, and when the focal length is shorter than the predetermined value, the first defocus amount is set. The second defocus amount smaller than the focus amount is defined as a light emission start defocus amount. The system control unit 50 converts the light emission start defocus amount set as described above into a light emission start focus position in accordance with the information on the current focus position, and moves the focus lens 311 to that position to drive the lens. Flash emission may be started. By setting the light emission start defocus amount in this way, the probability that the focus detection using the auxiliary light is unsuccessful can be reduced.

  In step S1005, the system control unit 50 sets a drive speed of the focus lens 311 (hereinafter, referred to as a focus drive speed). Here, the system control unit 50 sets a focus drive speed for performing a predetermined number of flashes within the range of the light emission start defocus amount set in S1003 or S1004. For example, when the sampling rate of the pair of phase difference image signals is 60 fps and the flash drive is performed five times within the range of the light emission start defocus amount D (mm), the focus drive speed is set to D / 5 × 60 (mm). / s). In this way, the system control unit 50 sets an appropriate focus driving speed according to the light emission start defocus amount and the sampling rate (sampling cycle) of the phase difference image signal.

  Next, in step S <b> 1006, the system control unit 50 sets (adjusts) the light emission amount in the flash light emission while driving the lens or sets the gain for the imaging signal using the dimming result in the step flash light emission in advance. Both the light emission amount and the gain setting are effective to generate the contrast required for a pair of phase difference image signals, but the glare for the flash of a person or an animal as a subject, power consumption and a pair of phase difference image signals are effective. An appropriate light emission amount or gain is set in consideration of the S / N of the signal.

  For example, in order to generate a larger contrast between a pair of phase difference image signals, the gain is set when the subject is a person, and the light emission amount when the subject is not a person. Specifically, the system control unit 50 causes the flash 48 to perform a plurality of focus detections while causing the flash 48 to emit step flashes with different light emission amounts, or sets a plurality of different gains to a signal obtained from the image sensor. By doing so, a plurality of focus detection results are obtained. Then, the light emission amount or gain in the subsequent focus detection is set. In addition to the plurality of focus detection results, a light emission amount or a gain may be set using a focus detection result obtained without causing the flash 48 to emit light. After finishing S1006, the system control unit 50 ends this processing.

  Next, flash emission and focus detection during lens driving performed in S809 of FIG. 16 will be described with reference to FIG. In step S1101, the system control unit 50 sets the frame rate for driving the image sensor 14 to the high-speed frame rate (second frame rate). For example, a low frame rate of 30 fps is changed to a high frame rate of 60 fps. Since the flash light emission time is very short, it is not necessary to lengthen the exposure time of the image sensor 14. The flash light emission may be performed in synchronization with the timing at which all the pixel rows of the image sensor 14 are exposed. Thus, if the irradiation range of the flash light emission is sufficiently wide, the contrast of the pair of phase difference image signals obtained from all the pixel regions of the image sensor 14 can be ensured.

  On the other hand, when the AF auxiliary light is not used or when the LED auxiliary light is used, the longer the exposure time of the image sensor 14, the more the contrast of the pair of phase difference image signals can be secured. For this reason, in the present embodiment, the frame rate (the second frame rate) when the flash auxiliary light is used (the second frame rate) when the AF auxiliary light is not used or when the LED auxiliary light is used is used. Frame rate) is set to high speed. Thereby, it is possible to realize a high-speed focus adjustment when the flash auxiliary light is used.

  In the present embodiment, the frame rate is increased only when the flash is emitted during driving of the lens. That is, a high-speed frame rate is used for flash light emission during lens driving, and a low-speed frame rate is used for step flash light emission. As described above, the focus detection at the time of the step flash emission also uses the focus detection result when no flash emission is performed. For this reason, if the frame rate is increased during the step flash emission, it is necessary to change the frame rate before and after the flash emission, and the time lag between the three focus detections increases. As described above, focus detection is performed under the same conditions as possible, in order to compare and select focus detection results when flash light is not used and when flash light is used at the first light emission amount and the second light emission amount. It is desirable. For this reason, in the present embodiment, the frame rate is increased only during flash light emission during driving of the focus lens.

  However, this is not limited to the case where the time required for switching the frame rate is short. The frame rate may be appropriately switched between a case where flash light emission is not used and a case where flash light emission is used, and focus detection accompanied by step flash light emission may be performed.

  Further, as described above, it is premised that a highly reliable focus detection result is obtained at the time of flash emission during driving of the lens. If the focus lens driving amount calculated from the obtained defocus amount is small, the effect of speeding up the focus adjustment is low, so that the speeding up of the frame rate may be omitted.

  Also, if the focus detection area is not narrowed down during flash emission while the lens is being driven, and a highly reliable focus detection result can be obtained both when flash emission is used and when flash emission is not used, the frame rate should be set. It is not necessary to speed up. This makes it possible to appropriately perform focus adjustment even in an imaging scene in which a long-distance subject to which the flash auxiliary light does not reach and a short-distance subject to which the flash auxiliary light reaches are mixed.

  Next, in step S1102, the system control unit 50 performs flash emission and focus detection. Here, the defocus amount is calculated using a pair of phase difference image signals obtained by focus detection accompanied by flash light emission at a preset light emission amount.

  In step S1103, the system control unit 50 updates the focus lens driving amount based on the calculated defocus amount. In flash light emission and focus detection during lens driving, the smaller the detected defocus amount, the smaller the detection error. Therefore, by updating the focus lens drive amount, in other words, the target position of the focus lens drive as described above, it is possible to perform highly accurate focus adjustment.

  In the present embodiment, a focus detection process performed using the flash auxiliary light that emits light intermittently with the focus lens 311 stopped, and a focus detection process performed using the flash auxiliary light while driving the focus lens 311 include: The switching is performed depending on whether or not a highly reliable focus detection result is obtained. Thereby, it is possible to realize high-speed focus adjustment while suppressing unnecessary emission of the flash auxiliary light when a highly reliable focus detection result cannot be obtained.

  In the present embodiment, a case has been described in which the focus adjustment is performed while relying on the focus detection result acquired in S809. However, the defocus amount detected at a certain focus position (first position) during driving of the focus lens, and the state where the focus lens is driven from the focus position where focus detection with step flash emission was performed to the first position before that The reliability may be determined based on the deviation from the estimated defocus amount estimated in step (1). When the difference between these two defocus amounts is large (that is, the difference value is larger than the predetermined difference value), the subject moves greatly or the direction of the camera 100 changes before and after the start of the focus lens driving. It is possible that it has changed significantly. In such a case, focus lens driving and focus detection may be interrupted. Thereby, the focus adjustment using the focus detection result whose reliability is not guaranteed can be completed early. The user can start the focus adjustment process again as needed, thereby reducing the time required for focus adjustment on the subject to be imaged.

  Further, the allowable number of times of flash light emission during driving of the focus lens described in S810 may be variable in accordance with the number of times of previous step flash light emission. As described above, the number of times of intermittent light emission during driving of the focus lens may be appropriately set from the viewpoint of reducing power consumption and securing the amount of light emission during imaging for image recording after focus adjustment. In addition, when the number of intermittent light emission is increased, by increasing the light emission start defocus amount, the influence of the movement of the subject during driving of the focus lens can be reduced, and the focus can be detected more reliably.

  In the present embodiment, flash light emission is performed with a light emission amount determined differently in advance, and a focus detection area is selected and a defocus amount is calculated using a pair of phase difference image signals obtained therefrom. Further, based on the light emission amount at which the selected focus detection result is obtained, light adjustment processing for adjusting the light emission amount thereafter is performed. Accordingly, it is not necessary to perform the light adjustment processing before performing the focus detection, and thus the focus can be quickly adjusted. Further, by performing dimming at the time of step flash emission, a highly reliable focus detection result can be obtained with one flash emission. For this reason, it is possible to reduce the number of times of flash light emission during driving of the lens and the number of step flash light emissions thereafter.

  In this embodiment, the adjustment of the contrast of the phase difference image signal is realized mainly by adjusting the light emission amount. However, it may be realized by adjusting the gain of the image signal read from the image sensor 14. In the adjustment based on the light emission amount, the effect of adjusting the contrast of a subject that is closer and has a higher reflectance is great depending on the reflectance and distance of the subject, and the S / N ratio of the phase difference image signal is improved. On the other hand, in the contrast adjustment by the gain adjustment, the S / N ratio of the focus detection signal is not improved, but the contrast can be adjusted more easily irrespective of the distance and the reflectance of the subject.

  Further, in the present embodiment, a case has been described in which the focus detection area is determined before flash light emission is performed during driving of the lens. However, in a mode in which a highly reliable focus detection result is obtained but a focus detection area is not narrowed down, such as the above-described automatic selection mode, the light emission amount cannot be adjusted corresponding to each focus detection area. Therefore, one of the first light emission amount, the second light emission amount, and no light emission may be selected. For example, a light emission amount corresponding to a more reliable focus detection result or a focus detection result indicating the presence of an object at a shorter distance may be selected.

  A second embodiment of the present invention will be described. Note that components that are the same as or similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted.

  A condition setting process of flash light emission during lens driving according to the present embodiment will be described with reference to FIG. This process is performed in step S806 in FIG. 16 instead of the condition setting process of flash light emission during lens driving described with reference to FIG. 18 in the first embodiment. The system control unit 50 sets the focus drive speed in S1201, and proceeds to S1202.

  In step S <b> 1202, the system control unit 50 sets the number of intermittent flashes (for example, five times) in the flash emission during the lens driving in the second focus detection processing.

Next, in step S <b> 1203, the system control unit 50 sets a flash start defocus amount for starting flash emission during driving of the lens according to the focus drive speed. In the second focus detection process, the number of intermittent light emission is C, the frame rate for driving the image sensor 14 is R [frame / sec], and the focus drive speed is V [mm / sec]. The system control unit 50 calculates the light emission start defocus amount Def by the following equation (2).
Def = C / R × V (2)
That is, the system control unit 50 sets the light emission start defocus amount Def such that it increases as the focus driving speed V increases, or conversely, decreases as the focus driving speed V decreases.
Next, in step S1204, the system control unit 50 sets (adjusts) the light emission amount in the flash light emission during driving of the lens or sets the gain for the image pickup signal using the dimming result in the step flash light emission in advance. The method of setting the light emission amount and the gain here is as described in the first embodiment (S1006). After finishing S1204, the system control unit 50 ends this processing.

  In the present embodiment, by setting the light emission start defocus amount in accordance with the focus drive speed, even when the focus drive speed differs due to different imaging optical systems, a constant number of intermittent light emission is maintained during the focus lens drive. Flash light can be emitted. As a result, the probability of unsuccessful focus detection can be reduced.

  The light emission start defocus amount may be set not only according to the focus drive speed as in the present embodiment but also according to the focal length of the imaging optical system as described in the first embodiment. That is, the light emission start defocus amount may be set according to at least one of the focal length of the imaging optical system and the focus drive speed.

  Third Embodiment A third embodiment of the present invention will be described. Note that components that are the same as or similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted. In the present embodiment, the system control unit 50 emits light in the flash light emission during driving of the lens every time the detected defocus amount obtained by focus detection changes by the light emission interval defocus amount. That is, the light emission interval defocus amount is a detected defocus amount that changes between flash light emission and intermittent light emission.

  With reference to FIG. 21, a description will be given of a condition setting process of flash light emission during lens driving according to the present embodiment. This process is performed in step S806 in FIG. 16 instead of the condition setting process of flash light emission during lens driving described with reference to FIG. 18 in the first embodiment. The system control unit 50 sets the focus drive speed in S1301, and proceeds to S1302.

  In step S1302, the system control unit 50 sets the number of intermittent light emissions (for example, five times) in flash light emission during driving of the lens.

  Next, in step S1303, the system control unit 50 sets the light emission interval defocus amount in flash light emission during driving of the lens. In this embodiment, the flash light emission is performed in synchronization with the timing at which all the pixel rows of the image sensor 14 are exposed, but the light emission interval is set to be different depending on the focus drive speed.

When the detected defocus amount acquired in the focus detection area 401 is D2, the number of intermittent light emission in the second focus detection processing is C2, the frame rate for driving the image sensor 14 is R2 [frame / sec], and focus driving is performed. The speed is set to V2 [mm / sec]. The ratio between the detected defocus amount and the number of intermittent light emission is D2 / C2, and the ratio of the focus drive speed to the frame rate is V2 / R2. The system control unit 50 calculates D2 / C2 / (V2 / R2), which is the ratio of D2 / C2 to V2 / R2, as K. At this time, the decimal number of K is rounded up and calculated as an integer value. The system control unit 50 calculates the light emission interval defocus amount Def2 by the following equation (3).
Def2 = V2 / R2 × K (3)
That is, the system control unit 50 increases the light emission interval defocus amount Def2 as the focus drive speed V2 is faster, the detected defocus amount D2 is larger, the number of intermittent light emission C2 is smaller, and the frame rate R2 is lower. Set to be. In other words, the system control unit 50 sets the light emission interval defocus amount Def2 as the focus drive speed V2 is slower, the detected defocus amount D2 is smaller, the number of intermittent light emission C2 is larger, and the frame rate R2 is faster. Set to be smaller.

  The system control unit 50 emits flash light during driving of the lens at the light emission interval defocus amount Def2 calculated in this manner and in synchronization with the drive cycle (1 / frame rate) of the image sensor 14.

  Next, in step S1304, the system control unit 50 sets (adjusts) the light emission amount in the flash light emission during driving of the lens or sets the gain for the imaging signal using the dimming result in the step flash light emission in advance. The method of setting the light emission amount and the gain here is as described in the first embodiment (S1006). After finishing S1304, the system control unit 50 ends this processing.

  Next, flash emission during lens driving and focus detection in this embodiment will be described with reference to the flowchart of FIG. This processing is performed in step S809 in FIG. 16 instead of the flash emission and focus detection during lens driving described with reference to FIG. 19 in the first embodiment.

  In step S1401, the system control unit 50 sets the frame rate for driving the image sensor 14 to a high-speed frame rate (second frame rate). The details are as described in the first embodiment.

  Next, in step S1402, the system control unit 50 performs flash emission and focus detection. Here, the defocus amount is calculated using a pair of phase difference image signals obtained by focus detection accompanied by flash light emission at a preset light emission amount.

  Next, in step S1403, the system control unit 50 determines whether to update the light emission interval defocus amount set in step S1303. Specifically, the system control unit 50 calculates a defocus amount (hereinafter, referred to as a defocus decrease amount) corresponding to the drive amount of the focus lens 311 from the time point of S802 to the time point of S1402 in FIG. Then, the system control unit 50 calculates a difference between the defocus amount obtained by subtracting the defocus reduction amount from the defocus amount calculated in S802 and the defocus amount calculated in S1402. If the calculated difference is equal to or larger than the predetermined value, the system control unit 50 determines that the error in the defocus amount calculated in S802 is large, and proceeds to S1404 to update the light emission interval defocus amount. On the other hand, if the calculated difference is less than the predetermined value, the process advances to step S1405 without updating the light emission interval defocus amount.

  In step S1404, the system control unit 50 sets the light emission interval defocus amount similarly to step S1303, that is, updates the defocus amount, and proceeds to step S1405.

  In step S1405, the system control unit 50 updates the focus lens driving amount based on the calculated defocus amount, and ends the process.

  According to the present embodiment, by setting the light emission interval defocus amount in accordance with the focus drive speed, even when the focus drive speed is different due to a different imaging optical system, a certain number of intermittent light emission during the focus lens drive can be performed. Flash light emission can be performed while maintaining. As a result, the probability of unsuccessful focus detection can be reduced.

Note that the light emission interval defocus amount may be set according to at least one of the focus drive speed, the detected defocus amount, the number of intermittent light emission, and the frame rate.
(Other Examples)
The present invention supplies a program for realizing one or more functions of the above-described embodiments to a system or an apparatus via a network or a storage medium, and one or more processors in a computer of the system or the apparatus read and execute the program. It can also be realized by the following processing. Further, it can also be realized by a unit (for example, an ASIC) that realizes one or more functions.

Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment in practicing the present invention.

14 Image sensor 48 Flash 50 System controller 311 Focus lens

Claims (10)

An imaging element for capturing a subject image formed by the imaging optical system;
Focus detection means for performing focus detection using an output from the image sensor,
Control means for controlling the focus detection means, controlling the driving of the focus element according to the result of the focus detection, and controlling the light emitting means for illuminating the subject,
The control means includes:
When causing the focus detection unit to perform the focus detection while driving the focus element, the light emission unit intermittently emits light in response to the detected defocus amount obtained by the focus detection becoming the emission start defocus amount. To start,
An imaging apparatus, wherein the light emission start defocus amount is set according to at least one of a focal length of the imaging optical system and a driving speed of the focus element.   The control means sets a first defocus amount to the light emission start defocus amount when the focal length is longer than a predetermined value, and sets the first defocus amount when the focal length is shorter than the predetermined value. The imaging apparatus according to claim 1, wherein a second defocus amount smaller than a focus amount is set as the light emission start defocus amount.   2. The imaging apparatus according to claim 1, wherein the control unit sets the light emission start defocus amount to be smaller as the driving speed is lower. 3. The control means includes:
A first focus detection process in which the light emitting unit is intermittently lit while the focus element is stopped and the focus detection unit performs the focus detection, and wherein the light emitting unit is intermittently lit while moving the focus element. Switching to a second focus detection process for causing the focus detection means to perform the focus detection,
The imaging apparatus according to any one of claims 1 to 3, wherein the emission start defocus amount is set in the second focus detection processing. An imaging element for capturing a subject image formed by the imaging optical system;
Focus detection means for performing focus detection using an output from the image sensor,
Control means for controlling the focus detection means, controlling the driving of the focus element according to the result of the focus detection, and controlling the light emitting means for illuminating the subject,
The control means includes:
When the focus detecting unit performs the focus detection while driving the focus element, the light emitting unit emits light every time a detected defocus amount obtained by the focus detection changes by a light emission interval defocus amount. Flashes intermittently,
The light emitting interval defocus amount is set according to at least one of a driving speed of the focus element, the detected defocus amount, the number of intermittent light emission of the light emitting unit, and a frame rate at which the imaging element is driven. Imaging device.   The control unit sets the light emission interval defocus amount to be smaller as the driving speed is lower, the detected defocus amount is smaller, the number of times of flash emission is larger, and the frame rate is faster. The imaging device according to claim 5, wherein: The control means includes:
A first focus detection process in which the light emitting unit is intermittently lit while the focus element is stopped and the focus detection unit performs the focus detection, and wherein the light emitting unit is intermittently lit while moving the focus element. Switching to a second focus detection process for causing the focus detection means to perform the focus detection,
The imaging apparatus according to claim 5, wherein the light emission interval defocus amount is set in the second focus detection processing. An image pickup device for picking up an image of a subject formed by an image pickup optical system, performing focus detection using an output from the image pickup device, controlling drive of the focus element according to a result of the focus detection, and illuminating the subject; A method of controlling an imaging device that controls a light emitting unit to perform,
Performing the focus detection while driving the focus element;
In the focus detection, a step of causing the light emitting unit to start intermittent light emission in accordance with the detected defocus amount obtained by the focus detection becomes a light emission start defocus amount,
A method of controlling an imaging apparatus, wherein the light emission start defocus amount is set according to at least one of a focal length of the imaging optical system and a driving speed of the focus element. An image pickup device for picking up an image of a subject formed by an image pickup optical system, performing focus detection using an output from the image pickup device, controlling drive of the focus element according to a result of the focus detection, and illuminating the subject; A method of controlling an imaging device that controls a light emitting unit to perform,
Performing the focus detection while driving the focus element;
In the focus detection, the step of intermittently emitting the light emitting means so as to emit light every time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount,
The light emitting interval defocus amount is set according to at least one of a driving speed of the focus element, the detected defocus amount, the number of intermittent light emission of the light emitting unit, and a frame rate at which the imaging element is driven. A control method of the imaging device.   A computer program for causing a computer of an imaging device to execute a process according to the control method according to claim 8.