JP7195783B2 - IMAGING DEVICE, ACCESSORY DEVICE AND CONTROL METHOD THEREOF - Google Patents

Description

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

Japanese Unexamined Patent Application Publication No. 2002-103000 discloses an image pickup apparatus that uses an image pickup device and performs focus detection by a so-called imaging plane phase difference method. Further, Japanese Patent Application Laid-Open No. 2002-200000 discloses a method of emitting auxiliary light toward a subject to perform focus detection when focus detection is difficult, such as when the subject is dark.

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

However, when focus detection is performed using auxiliary light, focus detection is possible only while the auxiliary light is directed toward the subject. Therefore, if the focus detection cannot be performed (unsuccessfully) for some reason even though the auxiliary light is emitted, it is necessary to re-emit the auxiliary light and redo the focus detection. In particular, as disclosed in Japanese Patent Application Laid-Open No. 2002-100001, when focus detection is performed by an imaging plane phase difference detection method using an image sensor having a pair of photoelectric conversion units in each of a plurality of pixels, a pair of photoelectric converters is used. The detectable defocus amount tends to be small due to the short base line length between the conversion portions. Therefore, there is a high possibility that focus detection will be unsuccessful even if auxiliary light is used.

SUMMARY OF THE INVENTION The present invention provides an image pickup apparatus and the like that can reduce the probability of unsuccessful focus detection when performing focus detection using auxiliary light.

An imaging apparatus as one aspect of the present invention includes an imaging device for imaging a subject image formed by an imaging optical system, focus detection means for performing focus detection using output from the imaging device, control of the focus detection means, and control means for controlling the driving of the focus element according to the result of focus detection and controlling the light emitting means for illuminating the subject. When causing the focus detection means to perform focus detection while driving the focus element, the control means causes the light emission means to emit light intermittently in response to the detected defocus amount obtained by the focus detection becoming the light emission start defocus amount. is started, and the driving of the focus element is controlled based on the defocus amount obtained by the focus detection during the intermittent light emission . The light emission start defocus amount is set according to at least one of the focal length of the imaging optical system and the drive speed of the focus element.

According to another aspect of the present invention, there is provided an imaging device comprising: an imaging element for imaging a subject image formed by an imaging optical system; focus detection means for performing focus detection using output from the imaging element; and control means for controlling the means, driving the focus element according to the result of focus detection, and controlling the light emitting means for illuminating the object. When causing the focus detection means to perform focus detection while driving the focus element, the control means causes the light emission means to emit light each time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount. is intermittently emitted , and driving of the focus element is controlled based on the defocus amount obtained by focus detection during the intermittent emission. The light emission interval defocus amount is set according to at least one of the drive speed of the focus element, the detected defocus amount, the number of intermittent light emissions of the light emitting means, and the frame rate at which the imaging element is driven.

Further, a control method as another aspect of the present invention includes an image pickup device that picks up a subject image formed by an image pickup optical system, performs focus detection using an output from the image pickup device, and performs focus detection. The present invention is applied to an imaging apparatus that controls driving of a focus element and controls a light emitting means for illuminating a subject according to the result. The control method includes the step of causing the light emitting means to start intermittent light emission in response to a detected defocus amount obtained by focus detection becoming a light emission start defocus amount when performing focus detection while driving a focus element. and controlling driving of the focus element based on a defocus amount obtained by focus detection during intermittent light emission . The light emission start defocus amount is set according to at least one of the focal length of the imaging optical system and the drive speed of the focus element.

a step of intermittently causing the light emitting means to emit light every time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount when performing the focus detection while driving the focus element ; and controlling the driving of the focus element based on the defocus amount obtained by focus detection during intermittent light emission, wherein the light emission interval defocus amount is determined by the driving speed of the focus element, the detected defocus amount, and the light emission. It is characterized in that it is set according to at least one of the number of times of intermittent light emission of the means and the frame rate at which the imaging device is driven. A control program as a computer program that causes the computer of the imaging apparatus to execute processing according to the control method also constitutes another aspect of the present invention.

According to the present invention, it is possible to reduce the probability of unsuccessful focus detection using auxiliary light.

1 is a block diagram showing the configuration of an imaging apparatus that is Embodiment 1 of the present invention. FIG. 4A and 4B are diagrams showing pixels and a pixel arrangement of an image pickup element used in the image pickup apparatus according to the first embodiment; FIG. 4A and 4B are diagrams for explaining the conjugate relationship between the exit pupil plane of the imaging optical system and the photoelectric conversion unit of the imaging element in the imaging apparatus of the first embodiment; FIG. 4A and 4B are diagrams showing focus detection areas provided within an imaging range in Embodiment 1. FIG. 4A and 4B are diagrams showing a pair of phase-contrast image signals acquired within a focus detection area in Example 1. FIG. 4 is a flowchart showing imaging processing according to the first embodiment; 4 is a flowchart showing focus adjustment processing in the first embodiment; 4A and 4B are diagrams for explaining driving of the focus lens to the initial position according to the first embodiment; FIG. 6 is a diagram showing a table of defocus amount information capable of focus detection in the first embodiment; FIG. 5 is a flowchart showing imaging processing in Example 1. FIG. 5 is a flowchart showing a process for determining whether or not AF auxiliary light needs to be emitted according to the first embodiment; 4 is a flowchart showing focus adjustment processing during LED auxiliary light emission according to the first embodiment. 5 is a flowchart showing focus adjustment processing when LED auxiliary light and flash auxiliary light are emitted according to the first embodiment; 4 is a flowchart showing subject presence/absence determination processing according to the first embodiment. 5 is a flowchart showing focus adjustment processing when flash assist light is emitted according to the first embodiment; 5 is a flowchart showing focus adjustment processing when flash assist light is emitted according to the first embodiment; 5 is a flowchart showing focus detection/light adjustment processing during flash emission in the first embodiment. 6 is a flowchart showing a condition setting process for flash light emission during lens driving in the first embodiment; 5 is a flowchart showing flash light emission and focus detection processing during lens driving in the first embodiment; 10 is a flowchart showing condition setting processing for flash light emission during lens driving in Embodiment 2 of the present invention. FIG. 11 is a flow chart showing a condition setting process for flash light emission during lens driving according to the third embodiment of the present invention; FIG. 10 is a flowchart showing flash light emission and focus detection processing during lens driving in Example 3. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a camera system composed of an imaging lens (interchangeable lens) 300 and a camera body (hereinafter simply referred to as a camera body) 100 as an imaging device to which the imaging lens 300 is detachably mounted. Show configuration. First, the configuration of the camera 100 will be described.

The lens mount 306 of the imaging lens 300 is mechanically and electrically detachably attached to 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 contact portions for electrically connecting the imaging lens 300 to the camera 100 .

A light flux that has entered the imaging lens 300 from the object and passed through the imaging optical system in the imaging lens 300 is reflected upward by the main mirror 130 and enters the optical viewfinder 104 . A user can take an image while observing a subject image, which is an optical image of the subject, through the optical viewfinder 104 . A part of a display section 54, which will be described later, is provided in the optical viewfinder 104, and the display section 54 displays a focus detection area, an in-focus state, a camera-shake warning, an aperture value, and an exposure correction value.

The main mirror 130 is composed of a half mirror. A portion of the light beam incident on the main mirror 130 arranged in the imaging optical path passes through the main mirror 130 and is reflected downward by the sub-mirror 131 provided behind it to enter the focus detection unit 105 .

The focus detection unit 105 is composed of 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 electrical signals (phase difference image signals as a pair of focus detection signals) using a photoelectric conversion element such as a line sensor, and performs AF ( autofocus) section 42. The AF unit 42 calculates the phase difference, which is the amount of deviation between the pair of phase difference image signals. The focus detection unit 105 and the AF section 42 constitute focus detection means.

A system control unit 50 as control means calculates a defocus amount as a focus detection result from the calculated phase difference. The focus control unit 342 performs focus adjustment processing to move the 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, focus adjustment is performed by moving the focus lens 311 in the image pickup optical system, but it is also possible to perform focus adjustment by moving the imaging element 14 described later as a focus element in the optical axis direction.

On the other hand, when the focus adjustment processing of the imaging lens 300 is completed and a still image, an electronic viewfinder image, or a moving image is to be captured, the main mirror 130 and the sub-mirror 131 are retracted out of the imaging light flux by a quick return mechanism (not shown). As a result, the luminous flux from the imaging lens 300 enters the imaging device 14 via the shutter 12 for controlling the amount of exposure. The imaging device 14 is composed of a photoelectric conversion element such as a CMOS sensor, and picks up (photoelectrically converts) a subject image formed by a light flux from the imaging lens 300 . After completing the imaging, the main mirror 130 and the sub-mirror 131 are returned to the imaging optical path.

An electric signal (analog imaging signal) generated by photoelectric conversion in the imaging element 14 is converted into a digital imaging signal by the A/D converter 16 . The timing generation section 18 is controlled by the memory control section 22 and the system control section 50 to supply clock signals and control signals to the imaging element 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 processing using the generated image data.

The imaging element 14 is configured such that all or some of its pixels are pixels capable of focus detection, and the pixels can be used to perform focus detection by an imaging plane phase difference detection method. The image processing unit 20 converts partial image data corresponding to a focus detection area (to be described later) out of the generated image data into focus detection data. The focus detection data is sent to the AF section 42 via the system control section 50, and the AF section 42 moves the focus lens 311 through the focus control section 342 in the imaging lens 300 to obtain an in-focus state.

In the camera 100 of this embodiment, the system control section 50 can generate a contrast evaluation value indicating the contrast state from the image data generated by the image processing section 20 . Then, it is also possible to perform AF by a contrast detection method that obtains an in-focus state by moving the focus lens 311 through the focus control unit 342 to a position where the contrast evaluation value peaks.

Therefore, in an optical viewfinder observation state in which the main mirror 130 and the sub-mirror 131 are arranged in the imaging optical path, the focus detection unit 105 performs phase difference detection AF (phase difference AF). On the other hand, in the electronic viewfinder observation state in which the main mirror 130 and the sub-mirror 131 are retracted out of the imaging light flux or during video imaging, AF (imaging plane phase difference AF) by the imaging plane phase difference detection method by the imaging device 14 and contrast detection method are performed. AF (contrast AF) is performed.

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

The image display section (display means) 28 has a display device such as a liquid crystal monitor. The image data for display written in the image display memory 24 is displayed by the image display section 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 can be displayed as an electronic viewfinder image.

The memory 30 stores still images and moving images generated by imaging. The memory 30 is also used as a work area for the system controller 50 . The compression/decompression unit 32 has a function of compressing and decompressing image data by Adaptive Discrete Cosine Transform (ADCT) or the like. Write data to memory 30 .

The shutter control unit 36 controls the shutter 12 based on the photometry information from the photometry unit 46 in cooperation with the aperture control unit 344 that drives the aperture 312 in the imaging lens 300 . The camera interface section 38 enables communication of control signals, status signals, various data, etc. between the camera 100 and the imaging lens 300 via the connectors 122 and 322 and the lens interface section 338 . Power supply from the camera 100 to the imaging lens 300 is also possible.

The photometry unit 46 performs AE processing. The brightness of the subject image can be measured by causing the light flux that has passed through the imaging lens 300 to enter the photometry unit 46 via the mirror 130 and a photometry lens (not shown). Also, the photometry unit 46 performs light control processing in cooperation with the flash 48 . The flash 48 serves as a light-emitting means (first light-emitting means) for emitting light toward a subject, and emits a flash (flash) to brightly illuminate the subject when capturing a still image, and intermittently emits light to the subject during focus detection. It has the function of projecting AF auxiliary light to illuminate the subject.

Instead of the photometry unit 46, the system control unit 50 controls the shutter control unit 36 and the aperture control unit 344 in the imaging lens 300 based on the result of computing the brightness 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 means (second light emitting means) capable of constant light emission (continuous light emission) as a light source for illuminating an object. The LED light emitted by the LED lamp 49 functions as LED auxiliary light, which is AF auxiliary light, as well as reduces the so-called red-eye phenomenon and serves as an indicator of imaging timing during self-timer imaging.

A system control unit 50 controls the overall operation of the camera 100 . The memory 52 stores constants, variables, programs, etc. used for the operation of the system control unit 50 . The display unit 54 is composed of a display device such as a liquid crystal display panel or an LED, and displays operating states, messages, and the like using characters, images, sounds, and the like. 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 shooting conditions such as shutter speed, aperture value, exposure compensation, and whether or not flash is used, remaining battery level, and date・Display the time, etc. As described above, part of the display section 54 is also provided inside 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. A mode dial 60, shutter switches 62, 64, an image display on/off switch 66, a quick review on/off switch 68, and an operation unit 70 are operated by the user to input various operation instructions to the system control unit 50. be. The operation unit 70 includes switches, dials, a touch panel, a pointing device based on line-of-sight 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 for switching blocks to be energized. The power supply control unit 80 detects the presence or absence of battery attachment, the type of battery, and the remaining battery level through the battery detection unit, and controls the DC/DC converter according to the detection results and instructions from the system control unit 50. A suitable voltage is supplied to each section including the recording medium for the required period. Connectors 82 and 84 connect primary batteries such as alkaline batteries and lithium batteries, secondary batteries such as NiCd batteries, NiMH batteries and lithium ion batteries, an AC adapter, and the like to the camera 100 .

The interface 90 has a connection function with a recording medium 200 such as a memory card or hard disk, and the connector 92 physically connects with the recording medium such as a memory card or hard disk. A recording medium attachment/detachment detector 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 above-described focus lens 311, an aperture 312, and the like. The zoom control unit 340 moves the zoom lens 310 along the optical axis to change the magnification. A focus control unit 342 as focus adjustment means moves the focus lens 311 in the optical axis direction to perform focus adjustment. A diaphragm control unit 344 drives the diaphragm 312 based on photometry information from the photometry unit 46 and the system control unit 50 .

A lens system controller 346 controls the overall operation of the imaging lens 300 . The lens system controller 346 has a memory function for storing constants, variables, programs, etc. used for its operation.

The non-volatile memory 348 stores identification information such as the manufacturing number unique to the imaging lens 300, optical information such as the open aperture value, minimum aperture value and focal length, various current or past setting values, and the like. 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 related to the “frame” that determines the diameter of the light flux passing through the imaging lens (imaging optical system) 300. Specifically, the distance of the “frame” from the imaging device 14 and the distance of the “frame” is information indicating the radius of the luminous flux passage aperture of . One of the "frames" is the diaphragm 312, and a lens holding member that holds lenses constituting the imaging optical system also corresponds to the "frame". Since the “frame” differs according to the position (zoom position) of the zoom lens 310 and the position (focus position) of the focus lens 311, it is prepared for each zoom position and each focus position. When performing focus detection, optimal frame information is selected according to the zoom position and focus position, and the frame information is sent from the lens control section 346 to the system control section 50 .

The defocus-related information is information on defocus amounts up to the infinity end and the close end for each subject distance, and is divided and stored for each subject distance associated with the focus position.

Next, the configuration of the imaging device 14 will be described with reference to FIGS. 2(a) to 2(c). FIG. 2A shows the configuration of one pixel 200 of the image sensor 14. FIG. 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 amplifier unit 204, a reset switch 205, and a selection switch 206. have Each switch is composed of a MOS transistor or the like. In the following explanation, it is assumed that each switch is composed of an N-type MOS transistor, for example. However, each switch may be composed of a P-type MOS transistor, or may be composed of another switching element. Also, 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 that has passed through the same microlens 201c, photoelectrically converts the light, and generates an electric charge corresponding to the amount of light received. In the following description, a signal obtained from charges generated in the photodiode 201a is referred to as an A signal, and a signal obtained from charges generated in the photodiode 201b is referred to as 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. Transfer switches 202a and 202b transfer charges generated by photodiodes 201a and 201b to a common floating diffusion region 203, respectively. Transfer switches 202a and 202b are controlled by control signals TX_A and TX_B, respectively.

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

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

Reset switch 205 is connected between floating diffusion region 203 and common power supply 208 . A reset switch 205 is controlled by a control signal RES to reset 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 section 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 the circuit configuration of the imaging device 14. As shown in FIG. The imaging device 14 has a pixel array 234 , vertical scanning circuit 209 , current source load 210 , readout circuit 235 , common output lines 228 and 229 , horizontal scanning circuit 232 and data output section 233 .

The pixel array 234 has a plurality of pixels 200 arranged in a matrix. In order to simplify the explanation, FIG. 2C shows horizontal n pixels×vertical 4 pixels. In addition, each pixel 200 is provided with one of color filters of a plurality of colors. In the example shown in FIG. 2(c), 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 the Bayer array.

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

A vertical scanning circuit 209 outputs a control signal to the pixels 200 in each pixel row via a drive signal line 208 provided for each pixel row. Although one drive signal line 208 is shown for each pixel row in FIG. 2C, a plurality of drive signal lines are actually connected to 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 readout section 235 via the vertical output line 207 and processed by the readout section 235 . A current source load 210 is connected to the vertical output line 207 of each pixel column.

The horizontal scanning circuit 232 outputs control signals HSR(0) to HSR(n−1) to sequentially select readout units to output signals from among the readout units 235 . The selected reading section 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 reading unit 235 has a clamp capacitor 211, feedback capacitors 214-216, an operational amplifier 213, a reference voltage source 212 and switches 217-220. It also has a comparator 221 , Latch_N 222 , Latch_S 223 and switches 226 and 227 .

A signal input to the reading unit 235 via the vertical output line 207 is input to the inverting input terminal of the operational amplifier 213 via the clamp capacitor 211 . A non-inverting input terminal of the operational amplifier 213 is supplied with the reference voltage Vref from the reference voltage source 212 . Feedback capacitors 214 to 216 are connected between the inverting input terminal and the output terminal of operational amplifier 213 . A switch 217 is also connected between the inverting input terminal and the output terminal of the operational amplifier 213 to short-circuit both ends of the feedback capacitors 214 to 216 . Switch 217 is controlled by control signal RES_C. Switches 218-220 are controlled by control signals GAIN0-2.

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_N222 is a memory element for holding the noise level (N signal), and Latch_S is a memory element for holding the signal level (S signal) of the A signal and the AB signal obtained by adding the A signal and the B signal. . A counter value 225 output from the output terminal of the comparator 221 and the counter 231 is input to Latch_N 222 and Latch_S 223, which 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. Common output lines 228 and 229 are connected to data output section 233 .

The switches 226 and 227 are controlled by a control signal hsr(h) from the horizontal scanning circuit 232. FIG. Here, h indicates the column number of the reading section 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 section 233 to the outside. This operation is called horizontal transfer.

In this embodiment, the imaging device 14 has a first readout mode and a second readout mode. A first readout mode is an all-pixel readout mode in which output signals are read out from all pixels in order to capture a high-definition still image for recording. The second readout mode is for displaying live view images and moving images for recording, which have fewer pixels than still images for recording. mode. Since the number of pixels required to generate Live View images and movies is less than the total number of pixels, the signal processing load can be reduced by reading out the output signal from only the number of pixels thinned out at a predetermined ratio in both the horizontal and vertical directions from the image sensor. It also contributes to reducing power consumption. In addition, in both the first and second readout modes, since the output signals from the respective photoelectric conversion units provided in each pixel are read out independently, a pair of phase difference image signals is generated in either readout mode. is possible.

3A and 3B show the exit pupil plane of the imaging optical system 101 in the camera system of this embodiment and the pixels (hereinafter referred to as , center pixel) 200 with a pair of photoelectric conversion units 201a and 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 in the plane on which the diaphragm 312 is arranged. On the other hand, the imaging optical system of the present embodiment has a variable magnification function, and the distance from the image plane to the exit pupil (exit pupil distance) and the size change due to the variable magnification. The imaging optical system 101 shown in FIG. 3A is in an intermediate zoom state with a focal length between the wide-angle end and the telephoto end. Assuming this as the standard exit pupil distance Zep, the eccentricity parameter is optimized according to the shape of the microlens 201c and the image height (X, Y coordinates).

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

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

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 seen from the optical axis direction. The imaging device 14 has pixels capable of outputting a signal from one of the two photoelectric conversion units 201a and 201b and capable of adding and outputting signals from both of them. The added and output signal 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, a luminous flux L passing through the imaging optical system (its outer edge is indicated by a straight line in the figure) is limited by an aperture plate 312a of a diaphragm 312, and the luminous flux from focus detection pupils EP1a and EP1b is limited by the aperture plate 312a. reaches the pixel 200 without vignetting in the imaging optical system. In FIG. 3(b), the cross section (outer edge) of the light beam L shown in FIG. 3(a) on the exit pupil plane is indicated by TL. Since most of the back-projected images EP1a and EP1b of the two photoelectric conversion units 201a and 201b are included inside the circle indicated by TL (that is, the aperture of the aperture plate 312a), the back-projected images EP1a and EP1b are It can be seen that only slight vignetting occurs. At this time, the vignetting state of the back-projected images EP1a and EP1b at the center of the exit pupil plane is symmetrical with respect to the optical axis of the imaging optical system (indicated by the dashed line in FIG. 3A), and the photoelectric conversion units 201a and 201b receive light. are equal to each other.

In this way, the image sensor 14 not only has the function of capturing an image of a subject, but also has the function of performing focus detection by the imaging plane phase difference detection method by individually receiving light beams from different focus detection pupils in the lens exit pupil. . In this embodiment, one pixel of the image sensor 14 has a pair of photoelectric conversion units. may

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

FIG. 5 shows an example of a pair of phase difference image signals 430a and 430b in this embodiment. A pair of phase difference image signals 430a and 430b are obtained by connecting A signals and B signals obtained from a plurality of pixels in the focus detection area 401 of the image pickup device 14, and further subjected to various image processing by the image processing unit 20 ( correction). A pair of phase difference image signals 430 a and 430 b are sent to the AF section 42 .

In FIG. 5, the horizontal axis indicates the pixel arrangement direction of the signals (A or B signal) connected to each other, and the vertical axis indicates the intensity of the signal. FIG. 5 shows a pair of phase difference image signals 430a and 430b when the imaging optical system is defocused on the object (unfocused state). Compared to the in-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. The AF unit 42 calculates the shift amount (phase difference) between the pair of phase difference image signals 430a and 430b using correlation calculation, and obtains the defocus amount of the imaging optical system with respect to the subject from the phase difference.

The system control unit 50 controls the focus lens 311 based on 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 target position information for moving the focus lens 311 from the focus position information and the drive amount of the focus lens 311 transmitted from the lens control unit 346 , and transmits the target position information to the lens control unit 346 . The lens control unit 346 moves the focus lens 311 to the target position through the focus control unit 342 . As described above, focus adjustment is performed by imaging plane phase difference AF.

Next, imaging control processing (control method) in the camera 100 of this embodiment will be described using the flowchart of FIG. FIG. 6 shows the flow of image capturing control processing when still image capturing is performed while a live view image is being displayed. The system control unit 50 as a computer executes this process according to a control program as a computer program. In the following description, "S" means step.

First, in S<b>1 , the system control unit 50 causes the imaging device 14 to start imaging for generating a live view image, and causes the imaging signal to be input 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 viewing this live view image. The live view image display is used by the user to check the imaging range and imaging conditions, and is updated at predetermined time intervals, such as 33.3 ms (30 fps) and 16.6 ms (60 fps).

However, the system control unit 50 may control the image display unit 28 not to display the live view image when the AF auxiliary light, which will be described later, is emitted. For example, in the case of AF assist light that uses flash light emission (hereinafter referred to as flash assist light), there is a risk that a part of the subject will be saturated in brightness and it may not be possible to obtain a high-quality image. 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 be emitted at all times, and the photometry unit 46 can maintain the display image in a proper exposure state, so there is no need to stop the display. No. Even when flash light emission is performed, if the area where the brightness is saturated is limited or the flash light emission amount is small, the display of the live view image may be continued.

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 up to 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 SW<b>1 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 or not the main (power) switch is turned off. If the main switch is not turned off, return to S2. On the other hand, if the main switch is turned off, this flow ends.

On the other hand, when the ON state of the switch SW1 is detected 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 modes include arbitrary selection mode, automatic selection mode and subject detection mode. The optional selection mode is a mode for setting one or more focus detection areas specified by the user. The automatic selection mode is a mode in which the system control section 50 sets one or more focus detection areas. The subject detection mode is a mode in which a specific subject such as a person's face is detected and one or more focus detection areas are set. In S6, the system control unit 50 acquires information on the focus detection area mode set in advance and subject detection information, which is information on a specific subject such as a person's face. 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 process will be described later. When the focus adjustment process ends, the system control section 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 imaging processing. 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 or not the main switch has been turned off. If the main switch is not turned off, the process returns to S2, and if the main switch is turned off, the process ends.

Next, the focus adjustment process performed in S7 of FIG. 6 will be described using the flowchart of FIG. After starting the focus adjustment process, the system control unit 50 acquires, in S201, 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 obtained detected defocus amount is highly reliable. If the reliability of the detected defocus amount is high, the system control unit 50 proceeds to S202.

The reliability here is determined by the system control unit 50 between the minimum value of the correlation amount of the pair of phase difference image signals and the magnitude of the difference between the correlation amounts in the vicinity of the shift amount showing the minimum correlation amount in the correlation calculation. Determined using

The amount of correlation indicates the degree of correlation between a pair of phase difference image signals, and 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 this 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, a pair of actual phase-difference image signals differ in shape from each other due to influences such as diffusion characteristics of light from the object, light amount adjustment errors, and noise that occurs individually for each pixel. Therefore, the 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.

Further, the shift amount can be calculated with higher accuracy as the difference between the correlation amounts obtained in the vicinity of the shift amount where the correlation amount indicates the minimum value is larger. This is because even if the amount of correlation fluctuates due to an error, if the difference in the amount of correlation is large, the effect on the detection of the shift amount is small. Therefore, when the difference in correlation amount is larger than the threshold Thr2, it is determined that the reliability is high (first reliability).

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

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

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

When the system control unit 50 determines in S202 that a defocus amount with high reliability cannot be detected, the system control unit 50 proceeds to S206 to perform processing for determining whether or not the AF auxiliary light needs to be emitted. 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 AF auxiliary light as LED auxiliary light or flash auxiliary light is required. If 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 search driving and focus detection in S208, the system control unit 50 determines that focus detection is possible in S209, and proceeds to S203.

On the other hand, the system control unit 50, which has determined in S209 that focus detection cannot continue, determines in S210 whether the focus lens 311 is positioned at the end of the movable range (telephoto end or close 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 to continue search driving and focus detection processing.

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 moving the focus lens 311 does not exist within the movable range of the focus lens 311. Then, the process proceeds to S211.

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

After determining in S207 that the AF auxiliary light is necessary, the system control unit 50 proceeds to S212 and calculates the initial position of the focus lens 311 (hereinafter referred to as initial focus position). First, the system control unit 50 acquires focus detection information, which will be described later, and uses the focus detection information to calculate a detectable defocus amount that is assumed to allow focus detection. In addition, the system control unit 50 can cover as wide a subject distance range as possible, including the closest end, based on the detectable defocus amount and information on the subject distance at the closest end of the imaging lens 300 (highly reliable defocus The defocus range for which the amount can be calculated is as wide as possible).

FIG. 8 shows the initial focus position. The horizontal axis indicates the focus position corresponding to the in-focus object distance. The calculated range of detectable defocus amounts (hereinafter referred to as defocus amount detectable range) is indicated by an arrow. The focus initial position is set so that the defocus amount detectable range extends to the long distance side from the close end within the defocus amount detectable range including the close end, which is the end of the movable range of the focus lens 311. there is

The reason why the focus initial position is set within the defocus amount detectable range including the closest end is that the subject distance at which the AF auxiliary light reaches and focus detection becomes possible is a short distance. For this reason, not only at the close-up end, but also by presetting a constant multiple of the focal length or a subject distance such as 1 m as a distance at which the subject exists with a high probability, and calculating the initial focus position so as to include the subject distance. good. If you set a constant multiple of the focal length or a subject distance of 1 m, etc., instead of the closest end, focus detection may not be possible for subjects closer to you. possible range.

Alternatively, the reachable distance of the flash assist light as the AF assist light may be set, and the focus initial position may be set with the reachable distance as the end on the long distance side. As a result, it is possible to limit the subject distance for focus detection, so that a more appropriate initial focus position with a margin can be set.

The focus detection information is information related to focus detection for approximating the detectable defocus amount, and includes the F number of the imaging lens 300, the above-described frame information, the image height of the focus detection area where focus detection is performed, and the phase difference image signal. is information about at least one of the contrasts of Based on the F-number of the imaging lens 300, the frame information, and the information on the image height of the focus detection area, the length of the base line between the pair of photoelectric conversion units that perform focus detection (the center-of-gravity distance between the focus detection pupils) and the diameter of the AF beam (focus detection pupil ) is calculated. The longer the base line length, the greater the amount of deviation between the pair of phase difference image signals per unit defocus amount, so focus detection can be performed with higher accuracy. Further, the smaller the AF beam diameter, the less the phase difference image signal is blurred by defocusing, and the amount of deviation between the pair of phase difference image signals can be detected even in a state of large defocusing. Note that the larger the AF beam diameter, the longer the baseline length.

Also, the detectable defocus amount varies depending on the contrast of the subject, spatial frequency characteristics, and the like. Focus detection is possible even in a state of greater defocusing for a subject having a lot of information of a higher spatial frequency and having a high contrast. For information on the contrast of the object, for example, the sum of the squares of the output differences between adjacent pixel signals in the phase difference image signal may be used.

The system control unit 50 stores information on the detectable defocus amount corresponding to the focus detection information described above in a table form. 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 subject contrast as the focus detection information, and acquires the detectable defocus amount from the table shown in FIG.

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

After calculating the focus initial position in S212, the system control unit 50 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 or not emission of only the LED auxiliary light is permitted. In this embodiment, the system control unit 50 controls the light emission of the flash 48 and the LED lamp 49 as AF auxiliary light emitting means. When only the LED auxiliary light is permitted to be emitted (when the emission of flash auxiliary light is prohibited), the system control unit 50 advances to S215 to emit the LED auxiliary light only from the LED lamp 49 for focus adjustment. Processing (hereinafter referred to as LED focus adjustment processing) is performed. On the other hand, if the emission of flash assist light is permitted, the system control unit 50 advances to S216 and emits LED assist light or flash assist light for focus adjustment processing (hereinafter referred to as LED/flash focus adjustment processing). )I do. Details of these focus adjustment processes will be described later. After completing the LED focus adjustment process in S215 or the LED/flash focus adjustment process in S216, the system control unit 50 ends the focus adjustment process.

Next, the imaging process performed in S9 of FIG. 6 will be described using the flowchart of FIG. First, in 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 the flash 48 emits flash light to take an image, the system control unit 50 drives the mechanical shutter 12 in accordance with the timing of the light emission.

Subsequently, in S<b>302 , the system control unit 50 reads out all pixels from the image sensor 14 for capturing a still image.

Next, in S<b>303 , the system control unit 50 (image processing unit 20 ) performs defective pixel interpolation on the imaging signal read out from the imaging device 14 based on position information of defective pixels stored in advance. Defective pixels include pixels with large variations in output offset and gain between pixels, and pixels that were not used for imaging (pixels dedicated to focus detection described above, etc.).

Next, in S304, the system control unit 50 performs image processing such as γ correction, color conversion, and edge enhancement on the image pickup signal to generate image pickup image data (still image data). Then, in S<b>305 , 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 inside the system control unit 50 in association with the captured image data recorded in S305. The characteristic information of the camera 100 includes, for example, exposure time, image processing during development, light sensitivity distribution of the pixels of the image sensor 14, and vignetting of the imaging light flux within the camera 100. FIG. Since the photosensitivity distribution of the pixels is determined by the microlens 201c and the photodiodes 201a and 201b, information on these structures (size and pitch of the photodiodes 201a and 201b, distance from the microlens 201c, etc.) is recorded. good too. The characteristic information of the camera 100 also includes information about the distance from the mounting surface of the camera 100 and the imaging lens 300 to the imaging device 14 and manufacturing errors.

Next, in S<b>307 , the system control unit 50 records the characteristic information of the imaging lens 300 in the memory 30 and the memory inside the system control unit 50 in association with the captured image data recorded in S<b>305 . The characteristic information of the imaging lens 300 is, for example, information regarding the exit pupil, frame information, focal length and F-number at the time of imaging, aberrations of the imaging optical system, and manufacturing errors.

Next, in S<b>308 , the system control unit 50 records image-related information regarding the captured image data in the memory 30 and a memory inside the system control unit 50 . The image-related information is, for example, information on the focus detection operation before imaging, movement of the subject, and information on the accuracy of the focus detection operation. After completing the process of S307, the system control unit 50 proceeds to S10 in FIG.

Next, with reference to the flowchart of FIG. 11, the determination of whether or not the AF auxiliary light needs to be emitted, which is performed in S206 of FIG. 7, will be described. In S401, the system control unit 50 acquires information regarding 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 photometry 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 S403, the system control unit 50 sets a threshold for emitting LED auxiliary light and flash auxiliary light (hereinafter referred to as a light emission threshold). Although the LED auxiliary light occupies a narrow irradiation range in the imaging range, it can emit light all the time, so it is easy to perform focus detection while emitting light. On the other hand, although the flash assist light has a wide irradiation range, it emits light intermittently. Therefore, if the light is emitted many times during focus detection, there is a risk that the amount of light emitted during image recording for image recording cannot be ensured. Therefore, in S403, the system control unit 50 sets the light emission threshold so that the LED auxiliary light is easy to emit, but the flash auxiliary light is difficult to emit. However, the focus detection error when the LED auxiliary light is monochromatic light such as red and the vignetting of the LED auxiliary light due to the LED lamp 49 being arranged near the imaging lens 300 due to the imaging lens 300 are taken into consideration. The light emission threshold may be set so that the auxiliary light is more likely to emit light.

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

Next, in S407, the system control unit 50 compares the photometric value obtained in S402 with the flash assist light emission threshold value obtained in S403. Also here, 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 flash assist light emission threshold, the system control unit 50 advances to S408 to set the flash emission determination to ON (flash emission permitted). On the other hand, if any one of the photometric values is greater than or equal to the flash assist light emission threshold value, the system control unit 50 advances to S409 to set the flash light emission determination to off (flash light emission prohibited). After completing S408 or S409, the system control unit 50 ends this process.

The emission threshold of the flash assist light may be smaller than the emission threshold of the LED assist light. Since the flash assist light has a short emission time as will be described later, setting the frame rate of the imaging device 14 to a high frame rate (for example, 60 fps) reduces the amount of external light. Therefore, it is necessary to emit the flash assist light only at the emission luminance that is less affected by outside light. Since the built-in LED emits light all the time, the amount of light emitted by the built-in LED can be received by increasing the accumulation time. From the above, it is preferable to set the emission threshold value of the flash assist light to a value smaller than that of the built-in LED.

Next, the LED focus adjustment process 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 an in-focus state is obtained in S504, which will be described later.

The processing from S502 to S510 is the same as the processing from S201 to S205 and S208 to S211 shown in FIG. 7, as shown in parentheses in each step.

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

In S602, the system control unit 50 performs subject presence/absence determination processing. As described above, although the LED auxiliary light can emit light at all times, it has the drawback that the irradiation range is narrow and vignetting is likely to occur due to the imaging lens 300 . Therefore, in S602, the system control unit 50 determines whether or not there is a subject for which the LED auxiliary light effectively functions. 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 effectively functions.

In S604, the system control unit 50 performs LED auxiliary light focus adjustment processing similar to that in S215 of FIG. In S605, the system control unit 50 performs flash focus adjustment processing. The details of this flash focus adjustment process will be described later. After completing the process of S604 or S605, the system control unit 50 ends the LED/flash focus adjustment process.

Next, the subject presence/absence determination processing performed in S602 of FIG. 13 will be described using the flowchart of FIG. In S701, the system control unit 50 acquires photometry information of the focus detection area. Here, the 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 LED auxiliary light. Then, in S703, the system control unit 50 acquires the photometric value corresponding to the focus detection area again.

Next, in S704, the system control unit 50 stops emitting the LED auxiliary light. In S705, the system control unit 50 calculates the amount of change from the photometric value before the LED auxiliary light emission obtained in S701 to the photometric value during LED emission obtained in S703. The system control unit 50 determines whether or not there is a subject for which the LED auxiliary light effectively functions, by using the fact that the presence of a subject that can be illuminated by the LED auxiliary light causes a change in the photometric value. As a result, it is possible to detect when the position of the subject is outside the reachable range of the LED auxiliary light, when the subject is not irradiated with the LED auxiliary light due to vignetting of the imaging lens 300, when the subject distance is too far and the LED auxiliary light does not reach the subject, and so on. be able to.

As a method of judging whether or not a subject exists, a method of performing focus detection while emitting LED auxiliary light and determining that a subject exists if focus detection is possible is also conceivable. However, with this method, focus detection becomes impossible when the object is greatly defocused, and there is a possibility that the object is not present even though it is present. Therefore, it is possible to appropriately determine the presence or absence of a subject regardless of the defocus state by determining the presence or absence of the subject using the change in the photometric information before and after the LED auxiliary light is emitted.

Next, in S705, if the change in the photometric value corresponding to the focus detection area before and after the LED auxiliary light is emitted is equal to or greater than a predetermined value, the system control unit 50 determines that there is a subject for which the LED auxiliary light effectively functions. judge. Then, this processing 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 assist light when the flash assist light is emitted. The horizontal axis indicates time, and the vertical axis indicates the focus (lens) position. FIG. 15 shows changes in the focus position when the focus lens 311 is driven from the focus adjustment start position to the in-focus position. The black circles in FIG. 15 indicate the timing at which the flash assist light is emitted.

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

When the defocus amount is detected by the emission of the flash assist light F1, the system control unit 50 starts driving the focus lens (time T1). After the focus lens drive is started, when the focus lens 311 approaches the in-focus position, the system control unit 50 emits flash assist light a plurality of times while continuing the focus lens drive (M1). That is, the flash assist light is emitted intermittently. If the flash assist light is always emitted while the focus lens is being driven, the required electric power becomes large. Therefore, the system control unit 50 starts intermittent light emission when the focus lens 311 reaches the position determined using the defocus amount obtained before driving the focus lens. In the following description, intermittent emission of flash assist light during focus lens driving is referred to as flash emission during lens driving. Further, focus detection performed with flash light emission during lens driving corresponds to the second focus detection processing.

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

The flow chart of FIG. 16 shows more details of the flash focusing process described above. In S801, the system control unit 50 initializes the count value of the number of step flash light emissions. In this embodiment, an upper limit is set for the number of times of step flash light emission to prevent unnecessary power consumption.

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

Next, in S803, the system control unit 50 determines whether or not a highly reliable focus detection result (having a second reliability higher than the first reliability) was obtained in S802. If a highly reliable focus detection result is not obtained (if the focus detection result has only the first reliability), the system control unit 50 proceeds to S804 to perform step flashes at all predetermined focus positions. It is determined whether or not focus detection involving light emission has ended.

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

In S804, when focus detection accompanied by step flash emission is completed at all predetermined focus positions, the system control unit 50 advances to S820 to determine that focus adjustment is impossible, and determines out of focus as in S211. display. On the other hand, if it is determined in S804 that focus detection accompanied by step flash light emission has not been completed at all predetermined focus positions, the system control unit 50 drives the focus lens to the next focus position in S805. Then, the process returns to S802.

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

Next, in S807, the system control unit 50 starts driving the focus lens according to the conditions set in S806. In S808, the system control unit 50 determines whether or not the focus lens 311 has passed through the light emission start focus position set in S806. If it has not yet passed, the system control unit 50 repeats the determination of S808 while continuing to drive 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 advances to S809 and performs focus detection (second focus detection processing) accompanied by flash light emission during lens driving. At this time, the system control unit 50 emits flash light in synchronization with the frame rate for generating image data (for driving the image pickup device 14), and sets (selects) the pair of focus detection areas obtained in S802. 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 times of flash light emission during lens driving is equal to or less than a predetermined number of times. Focus judgment display is performed. This is a process performed to prevent unnecessary light emission by assuming that a subject detected before the start of focus lens driving has been lost due to movement of the subject, framing by the user, or the like. In S810, if the number of times of flash light emission during lens driving is equal to or less than the predetermined number of times, 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 S813, the system control unit 50 performs focus detection and light control while performing step flash light emission (that is, intermittent light emission with the focus lens drive stopped) in the same manner as in S802. The reason why light control processing is performed again near the in-focus position is to avoid performing focus detection using a pair of phase difference image signals saturated due to changes in the defocus state. In particular, when the subject includes thin lines, the blurring becomes smaller as the state changes from the blurred state to the in-focus state, and the luminance level of the pair of phase difference image signals rises and saturates. Since a pair of saturated phase-difference image signals causes focus detection errors, light control processing is performed near the in-focus position.

After completing S813, the system control unit 50 determines in S814 whether or not 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 process ends.

The system control unit 50, having determined in S814 that the detected defocus amount is greater than the focus determination threshold value, advances to S816 to drive the focus lens based on the detected defocus amount.

After finishing (stopping) the driving of the focus lens in S816, in S817, the system control unit 50 determines whether or not the number of times of step flash light emission is equal to or less than a predetermined number of times. Since the step flash light emission is performed before the start of the focus lens drive, the total number of times from before the start of the focus lens drive is determined here. When the number of times of step flash emission exceeds the predetermined number of times, the system control unit 50 advances to S820, interrupts focus detection, and performs out-of-focus determination display.

On the other hand, if the step flash emission count is equal to or less than the predetermined number, the system control unit 50 advances to S818 to perform flash assist light emission and focus detection with the light emission amount set based on the previous light control 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 light adjustment result obtained in S813 without performing light adjustment again. . As a result, highly accurate focus detection can be achieved without unnecessary light emission. If the defocus amount obtained in S813 is large and the defocus state is significantly different from that in S818, the same processing as in S813 may be performed again.

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

Next, focus detection and light control processing accompanied by flash light emission performed in S802 of FIG. 15 will be described with reference to the flowchart of FIG. In 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 flash light emission, and determines a highly reliable focus detection result. Remember.

Next, in S902, the system control unit 50 performs flash light emission with the first light emission amount, and performs focus detection and focus detection result using a pair of phase-difference image signals acquired from the image sensor 14 in synchronization with this. Reliability determination is performed, and a highly reliable focus detection result is selected and stored.

Next, in S903, the system control unit 50 performs flash light emission with 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 this. It performs focus detection and determines the reliability of the focus detection result. Then, a highly reliable focus detection result is selected and stored.

Next, in S904, the system control unit 50 uses the focus detection results obtained in S901, S902, and S903 to set a focus detection area to be used for focus adjustment from a plurality of focus detection areas. Specifically, for example, the focus detection area indicating the existence of the object on the closest side is set as the focus detection area used for focus adjustment. This is because there is a high possibility that the main subject that the user intends to capture is on the short distance side. However, the method of selecting the focus detection area used for focus adjustment is not limited to this. For example, a focus detection area used for focus adjustment may be set using the averaged focus detection results obtained by averaging a plurality of focus detection results with different amounts of flash light emission.

In general, the higher the contrast of the pair of phase-difference image signals, the higher the detection accuracy of the defocus amount. 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 signals may not be used.

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

Further, the system control unit 50 stores photometry information in a state in which flash light emission is not performed in the selected focus detection area and the light emission amount (first or second light emission amount) of the flash light emission at which the selected focus detection result is obtained. Acquire the corresponding photometric information of the selected focus detection area. Then, from the difference between these two pieces of photometric information, the amount of emitted light necessary and sufficient for focus detection is calculated.

Let BV_n be the photometric value when the flash is not emitted, BV_af be the photometric value when the flash is emitted, and BV_T be the target photometric value necessary and sufficient for focus detection. In this case, the reference amount of light emission, that is, the gain G with respect to the amount of flash light emission with 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 the 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 converting between the linear scale and the logarithmic scale. If the photometric value at the time of flash emission is out of the photometric range, the photometric value cannot be measured appropriately. For this reason, in the case of a photometric value with low reliability (for example, a photometric value that is more than 5 steps of appropriate exposure and less than -5 steps), it is clipped at the upper or lower limit of the highly reliable photometric value. The above calculation is performed using the value as the photometric value at the time of flash emission.

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

The system control unit 50, having finished obtaining the light control result in S905, advances to S906, increments the number of times of step flash emission, and ends this processing.

Next, the condition setting process for flash light emission during lens driving performed in S806 of FIG. 16 will be described with reference to the flowchart of FIG. The system control unit 50 acquires information on the focal length of the imaging lens in S1001, and proceeds to S1002.

In S1002, the system control unit 50 determines whether or not the focal length acquired in step S1001 is equal to or greater than a predetermined value (for example, 100 mm). proceed to

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

In this embodiment, the light emission start defocus position is set according to the focal length of the imaging lens. Since an imaging lens with a long focal length generally has a wide defocus range from the infinity end to the closest end, the driving speed of the focus lens is high. On the other hand, since an imaging lens with a short focal length has a narrow defocus range, the drive speed of the focus lens is slow. Therefore, in this embodiment, when the focal length of the imaging lens is equal to or greater than a predetermined value, the first defocus amount is used as the light emission start defocus amount, and when the focal length is shorter than the predetermined value, the first defocus amount is used. A second defocus amount that is smaller than the focus amount is set as a light emission start defocus amount. The system control unit 50 converts the light emission start defocus amount set as described above to the light emission start focus position in combination with information on the current focus position, and moves the focus lens 311 to that position, thereby driving the lens. A flash may be initiated. By setting the light emission start defocus amount in this manner, the probability of unsuccessful focus detection using auxiliary light can be reduced.

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

Next, in S1006, the system control unit 50 sets (adjusts) the amount of light emitted during flash light emission during lens driving or sets the gain for the imaging signal using the light control result of the previous step flash light emission. Both the light emission amount and gain settings are effective in generating the contrast required for a pair of phase contrast image signals. An appropriate amount of light emission or gain is set in consideration of the S/N of the signal.

For example, in order to generate a greater contrast in a pair of phase-difference image signals, gain setting is used when the subject is a person, and light emission amount is used when the subject is not a person. Specifically, the system control unit 50 causes the flash 48 to perform step flash light emission with mutually different light emission amounts while performing focus detection a plurality of times, or sets a plurality of mutually different gains for the signals obtained from the image sensor. By doing so, a plurality of focus detection results are obtained. Then, the amount of light emission or the gain in subsequent focus detection is set. In addition to the plurality of focus detection results described above, a focus detection result obtained without flash 48 may be used to set the amount of light emission or the gain. After completing S1006, the system control unit 50 ends this process.

Next, with reference to FIG. 19, flash light emission during lens driving and focus detection performed in S809 of FIG. 16 will be described. In S1101, the system control unit 50 sets the frame rate for driving the imaging device 14 to a high-speed frame rate (second frame rate). For example, the low-speed frame rate of 30 fps is changed to the high-speed frame rate of 60 fps. Since flash light emission has a very short light emission time, it is not necessary to lengthen the exposure time of the imaging element 14 . Flash light emission may be performed in synchronization with the timing at which all pixel rows of the image sensor 14 are exposed. As a result, if the irradiation range of flash light emission is sufficiently wide, the contrast of a pair of phase difference image signals obtained from all pixel regions of the imaging element 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 imaging device 14 is, the more the contrast of the pair of phase difference image signals can be secured. For this reason, in this embodiment, the frame rate (second frame rate) when using the flash assist light is different from the frame rate (first frame rate) when not using the AF assist light or when using the LED assist light. frame rate) to a high speed. This makes it possible to speed up focus adjustment when using the flash assist light.

Also, in this embodiment, the frame rate is increased only when flash light is emitted during lens driving. That is, a high frame rate is used during flash light emission during lens driving, and a low frame rate is used during step flash light emission. For focus detection during step flash light emission, the focus detection result obtained when flash light emission is not performed is also used as described above. Therefore, if the frame rate is increased during step flash emission, it becomes necessary to change the frame rate before and after the flash emission, increasing the time lag between three focus detections. As described above, focus detection is performed under the same conditions as much as possible in order to compare the results of focus detection when flash light emission is not used and when flash light emission is used with the first and second light emission amounts. is desirable. For this reason, in this embodiment, the frame rate is increased only when flash light is emitted while the focus lens is being driven.

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

Moreover, as described above, it is assumed that a highly reliable focus detection result is obtained during flash light emission during lens driving. 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 the speeding up of the frame rate may be omitted.

Also, if the focus detection area is not narrowed down when the flash fires while driving the lens, and highly reliable focus detection results can be obtained both when the flash fire is used and when the flash fire is not used, the frame rate should be reduced. No need to speed up. As a result, it is possible to appropriately adjust the focus even in an imaging scene in which a long-distance subject to which the flash assist light does not reach and a short-distance subject to which the flash assist light reaches are mixed.

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

Then, in S1103, the system control unit 50 updates the focus lens drive 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, highly accurate focus adjustment can be performed.

In the present embodiment, focus detection processing is performed using intermittent flash assist light while the focus lens 311 is stopped, and focus detection processing is performed using the flash assist light while driving the focus lens 311. Switching is performed depending on whether or not a highly reliable focus detection result can be obtained. As a result, it is possible to achieve high-speed focus adjustment while suppressing the emission of unnecessary flash assist light when highly reliable focus detection results cannot be obtained.

In this embodiment, a case has been described in which focus adjustment is performed by relying on the focus detection result acquired in S809. However, the detected defocus amount at a certain focus position (first position) while the focus lens is being driven, and the state in which the focus lens is driven from the focus position where focus detection accompanied by step flash light emission was previously performed to the first position Reliability may be determined from the deviation from the estimated defocus amount estimated in . If the difference between these two defocus amounts is large (that is, if the difference value is greater than the predetermined difference value), the subject may move significantly or the direction of the camera 100 may change between before and after the start of driving the focus lens. It is possible that it has changed significantly. In such a case, focus lens drive and focus detection may be interrupted. This makes it possible to quickly complete focus adjustment using focus detection results whose reliability is not guaranteed. The user can shorten the time required for focusing on a subject intended to be imaged by restarting focus adjustment processing as necessary.

Further, the allowable number of times of flash light emission during focus lens driving described in S810 may be variable according to the number of step flash light emission times in advance. As described above, the number of times of intermittent light emission during focus lens driving may be appropriately set from the viewpoint of reducing power consumption and ensuring the light emission amount for image recording after focus adjustment. Further, when the number of times of intermittent light emission is increased, by increasing the light emission start defocus amount, the influence of subject movement during focus lens driving can be reduced, and focus detection can be performed more reliably.

In this embodiment, flash light emission is performed with light emission amounts determined to be different from each other in advance, and a pair of phase difference image signals obtained therefrom is used to select a focus detection area and calculate a defocus amount. Further, light control processing is performed for adjusting the subsequent light emission amount based on the light emission amount at which the selected focus detection result is obtained. This eliminates the need to perform light control processing before performing focus detection, enabling rapid focus adjustment. Further, by performing light control during step flash emission, a highly reliable focus detection result can be obtained with a single flash emission. Therefore, it is possible to reduce the number of times of flash light emission during lens driving and subsequent step flash light emission.

Further, in this embodiment, the adjustment of the contrast of the phase difference image signal is realized mainly by adjusting the amount of light emission. However, it may be realized by adjusting the gain of the imaging signal read out from the imaging device 14 . The adjustment based on the light emission amount is highly effective in adjusting the contrast of a subject that is closer and has a high reflectance 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, the contrast adjustment by gain adjustment does not improve the S/N ratio of the focus detection signal, but the contrast can be adjusted more easily regardless of the object distance or reflectance.

Also, in this embodiment, the case where the focus detection area is determined before flash light emission during lens driving has been described. However, in a mode such as the automatic selection mode described above, in which a highly reliable focus detection result is obtained but the focus detection area is not narrowed down, it is not possible to adjust the amount of light emission corresponding to each focus detection area. Therefore, any one of the first light emission amount, the second light emission amount, and no light emission may be selected. For example, it is sufficient to select a light emission amount corresponding to a more reliable focus detection result or a focus detection result indicating the existence of a subject at a closer distance.

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

Referring to FIG. 20, the condition setting process for flash light emission during lens driving in this embodiment will be described. This processing is performed in S806 of FIG. 16 in place of the condition setting processing for flash light emission during lens driving described with reference to FIG. 18 in the first embodiment. The system control unit 50 sets the focus driving speed in S1201, and proceeds to S1202.

In S1202, the system control unit 50 sets the number of times of intermittent light emission (for example, 5 times) in flash light emission during lens driving in the second focus detection process.

Next, in S1203, the system control unit 50 sets a light emission start defocus amount for starting flash light emission during lens driving according to the focus drive speed. Let C be the number of times of intermittent light emission in the second focus detection process, R [frame/sec] be the frame rate for driving the imaging device 14, and V [mm/sec] be the focus drive speed. The system control unit 50 calculates the light emission start defocus amount Def by the following formula (2).
Def=C/R×V (2)
That is, the system control unit 50 sets the light emission start defocus amount Def so that it increases as the focus driving speed V increases, and conversely, decreases as the focus driving speed V decreases.
Next, in S1204, the system control unit 50 sets (adjusts) the amount of light emitted during flash light emission during lens driving or sets the gain for the imaging signal using the light control result of the previous step flash light emission. The method of setting the light emission amount and gain here is as described in the first embodiment (S1006). After completing S1204, the system control unit 50 ends this process.

In this embodiment, by setting the light emission start defocus amount according to the focus drive speed, even when the focus drive speed differs due to the imaging optical system being different, the number of times of intermittent light emission can be maintained while the focus lens is being driven. flash light emission can be performed. As a result, the probability of unsuccessful focus detection can be reduced.

Note that the light emission start defocus amount may be set not only according to the focus driving speed as in this 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 driving speed.

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

The condition setting process for flash light emission during lens driving in this embodiment will be described with reference to FIG. This processing is performed in S806 of FIG. 16 in place of the condition setting processing for 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 S1302, the system control unit 50 sets the number of times of intermittent light emission (for example, 5 times) during flash light emission during lens driving.

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

Let D2 be the detected defocus amount acquired in the focus detection area 401, let C2 be the number of times of intermittent light emission in the second focus detection process, let R2 [frame/sec] be the frame rate for driving the image sensor 14, and focus drive Let the speed be V2 [mm/sec]. Also, let D2/C2 be the ratio between the detected defocus amount and the number of times of intermittent light emission, and let V2/R2 be the ratio between the focus drive speed and the frame rate. The system controller 50 calculates D2/C2/(V2/R2) as K, which is the ratio of D2/C2 and V2/R2. At this time, the decimal point 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 formula (3).
Def2=V2/R2×K (3)
That is, the system control unit 50 increases the light emission interval defocus amount Def2 as the focus driving speed V2 becomes faster, as the detected defocus amount D2 becomes larger, as the intermittent light emission frequency C2 becomes smaller, and as the frame rate R2 becomes slower. set to be In other words, the system control unit 50 sets the light emission interval defocus amount Def2 as the focus driving speed V2 becomes slower, as the detected defocus amount D2 becomes smaller, as the number of intermittent light emissions C2 becomes larger, and as the frame rate R2 becomes faster. set to be smaller.

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

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

Next, flash light emission during lens driving and focus detection in this embodiment will be described with reference to the flow chart of FIG. This processing is performed in S809 of FIG. 16 in place of flash light emission and focus detection during lens driving described in the first embodiment with reference to FIG.

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

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

Next, in S1403, the system control unit 50 determines whether or not to update the emission interval defocus amount set in S1303 described above. Specifically, the system control unit 50 calculates a defocus amount (hereinafter referred to as defocus decrease amount) corresponding to the driving amount of the focus lens 311 from the time of S802 to the time of S1402 in FIG. Then, the system control unit 50 calculates the difference between the defocus amount obtained by subtracting the defocus decrease amount from the defocus amount calculated in S802 and the defocus amount calculated in S1402. If the calculated difference is equal to or greater 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 proceeds to S1405 without updating the light emission interval defocus amount.

In S1404, the system control unit 50 sets the emission interval defocus amount in the same manner as in S1303, that is, updates it, and proceeds to S1405.

Then, in S1405, the system control unit 50 updates the focus lens drive amount based on the calculated defocus amount, and ends this process.

According to the present embodiment, by setting the light emission interval defocus amount according to the focus drive speed, even if the focus drive speed differs due to the imaging optical system being different, the number of times of intermittent light emission can be maintained during the focus lens drive. 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 emissions, and the frame rate.
(Other examples)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing to It can also be implemented by a unit (for example, ASIC) that implements one or more functions.

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

14 image sensor 48 flash 50 system control unit 311 focus lens

Claims (8)

an imaging device that captures a subject image formed by an imaging optical system;
focus detection means for performing focus detection using the output from the imaging device;
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 is
When causing the focus detection means to perform the focus detection while driving the focus element, the light emission means intermittently emits light in response to a detected defocus amount obtained by the focus detection becoming a light emission start defocus amount. and controlling the driving of the focus element based on the defocus amount obtained by the focus detection during the intermittent light emission ,
An image pickup apparatus, wherein the light emission start defocus amount is set according to at least one of a focal length of the image pickup optical system and a driving speed of the focus element. The control means sets a first defocus amount to the 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. 2. The imaging apparatus according to claim 1, wherein a second defocus amount smaller than the focus amount is set as the light emission start defocus amount. 2. The imaging apparatus according to claim 1, wherein said control means sets said light emission start defocus amount to be smaller as said driving speed is slower. The control means is
a first focus detection process in which the light emitting means is caused to emit light intermittently while the focus element is stopped and the focus detection means is caused to perform the focus detection; switching between a second focus detection process for causing the focus detection means to perform the focus detection,
4. The imaging apparatus according to claim 1, wherein the light emission start defocus amount is set in the second focus detection process. an imaging device that captures a subject image formed by an imaging optical system;
focus detection means for performing focus detection using the output from the imaging device;
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 is
When causing the focus detection means to perform the focus detection while driving the focus element, the light emission means emits light each time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount. is intermittently emitted, and driving of the focus element is controlled based on the defocus amount obtained by the focus detection during the intermittent emission,
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 times of intermittent light emission of the light emitting means, and the frame rate at which the imaging element is driven. imaging device. An imaging device for capturing an image of a subject formed by an imaging optical system is provided, focus detection is performed using an output from the imaging device, and driving control of the focus device and illumination of the subject are performed according to the result of the focus detection. A control method for an imaging device that controls light emitting means for
When performing the focus detection while driving the focus element,
a step of causing the light emitting means to start intermittent light emission when the detected defocus amount obtained by the focus detection becomes the light emission start defocus amount;
controlling driving of the focus element based on the defocus amount obtained by the focus detection during the intermittent light emission ;
A control method for an imaging device, 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 imaging device for capturing an image of a subject formed by an imaging optical system is provided, focus detection is performed using an output from the imaging device, and driving control of the focus device and illumination of the subject are performed according to the result of the focus detection. A control method for an imaging device that controls light emitting means for
When performing the focus detection while driving the focus element,
intermittently causing the light emitting means to emit light every time the detected defocus amount obtained by the focus detection changes by the light emission interval defocus amount;
controlling driving of the focus element based on the defocus amount obtained by the focus detection during the intermittent light emission ;
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 times of intermittent light emission of the light emitting means, and the frame rate at which the imaging element is driven. A control method for an image pickup apparatus. A computer program for causing a computer of an imaging device to execute processing according to the control method according to claim 6 or 7.

Images