Focus detector

Abstract

To improve accuracy in prediction of focus detection.SOLUTION: A focus detector comprises: an imaging section that includes a plurality of pixels which photoelectrically convert light having passed through an optical system including a focus lens to accumulate an electric charge and output a signal used for focus detection, and captures a subject image formed by a luminous flux having passed through the optical system; a defocus calculation section for calculating a defocus amount, which is an amount of deviation between a position of the subject image and a position of an imaging surface of the imaging section; a timing calculation section in which the pixel corresponding to at least one focus area calculates accumulation timing for accumulating the electric charge on the basis of position information of the at least one focus area selected from among a plurality of focus areas; an acquisition section for acquiring the position information of the focus lens; and an arithmetic section for calculating a drive amount of the focus lens on the basis of a position of the focus lens at the accumulation timing determined on the basis of the position information of the focus lens and the defocus amount calculated by the defocus calculation section.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a focus detection device.

Background Art

[0002] A camera that performs focus detection based on signals obtained from focus detection pixels of an image sensor is known (see Patent Document 1). There is a demand for improving the accuracy of focus detection prediction during continuous shooting.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The focus detection device according to the first aspect of the present invention has a plurality of pixels that photoelectrically convert light that has passed through an optical system including a focus lens, accumulate charges, and output signals used for focus detection, and an imaging unit that images a subject image formed by a light beam that has passed through the optical system, a defocus calculation unit that calculates a defocus amount, which is the amount of deviation between the position of the subject image and the position of the imaging surface of the imaging unit, based on the signals, a timing calculation unit that calculates an accumulation timing at which the pixels corresponding to at least one focus area selected from among a plurality of focus areas accumulate charges, based on position information of the at least one focus area, an acquisition unit that acquires position information of the focus lens, and a calculation unit that calculates a driving amount of the focus lens based on the position of the focus lens at the accumulation timing determined based on the position information of the focus lens and the defocus amount calculated by the defocus calculation unit.

Brief Description of the Drawings

[0005]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0006] The focus detection device according to an embodiment of the present invention is mounted, for example, on an interchangeable-lens camera system. <Outline of AF Operation> First, with reference to FIGS. 1 and 2, an overview of the AF (autofocus) operation will be described. FIG. 1 is a perspective view of a camera system 1 before an interchangeable lens 3 is attached to a camera body 2 according to an embodiment. The coupling between the camera body 2 and the interchangeable lens 3 is achieved by a bayonet structure of a body-side mount 210 and a lens-side mount 310. When the camera body 2 and the interchangeable lens 3 are coupled, the contact terminals provided near each mount physically contact each other and are electrically connected.

[0007] FIG. 2 shows a shooting field of view 50 imaged by an imaging element 260 of the camera body 2. It is also a diagram exemplifying a focus area P within the shooting field of view 50 and is shown together with the captured image. In the imaging area 50, 21 focus areas P are provided. The focus area is also referred to as a focus detection area, a focus detection position, a distance measurement point, and an autofocus (AF) point. Note that the number and positions of the illustrated focus areas P are merely examples and are not limited to the aspect of FIG. 2.

[0008] The focus detection device, which will be described in detail with reference to FIG. 4, detects the defocus amount (amount of out-of-focus), which is the deviation amount between the position of the image of the subject formed by the light beam passing through the interchangeable lens 3 and the position of the imaging surface 260S of the imaging element 260 of the camera body 2, by detecting the amount of image shift (phase difference) of the subject image by a pair of light beams passing through different pupils of the interchangeable lens 3 for each focus area P. Then, for example, the position of the focus lens included in the interchangeable lens 3 is adjusted so that the position of the image of the subject existing in the area corresponding to the selected focus area P among the plurality of focus areas P coincides with (is in focus with) the position of the imaging surface 260S of the imaging element 260, and an AF operation is performed.

[0009] The focus area P adopted for the AF operation can be arbitrarily selected by the user's operation or automatically selected by the camera body 2. In the case of the AF mode in which the focus area P is selected by the user's operation, the focus detection device detects the amount of image shift of the subject image existing in the focus area P selected by the user's operation. Then, the focus detection device performs an AF operation so as to focus on the subject existing in the selected focus area P.

[0010] Also, in the case of the AF mode in which the focus area P is automatically selected, the camera body 2 selects at least one focus area P out of the above 21 points. For example, in the example shown in FIG. 2, when the mode of focusing on a person's face is selected, the camera body 2 selects two focus areas P(i) and P(ii) included in the face portion of the person, and detects the amount of image shift of each subject image for each of the two focus areas P(i) and P(ii).

[0011] When the focus detection device selects the focus area P(ii) as the focus area that is closest (nearest) to the camera system 1 or has the highest contrast among the two focus areas P(i) and P(ii), the focus detection device selects the focus area P(ii). Then, the focus detection device performs an AF operation so as to focus on the face portion existing in the selected focus area P(ii). Note that the focus detection device can also perform an AF operation so as to focus on the face portion in consideration of the defocus amounts of both of the two focus areas P(i) and P(ii) selected as being included in the face portion. For example, the average value of the two defocus amounts may be calculated, and the focus lens may be driven (AF operation) with the defocus amount of the calculated average value, or a weighted average may be calculated so that the two defocus amounts fall within the depth of field as much as possible, and the AF operation may be performed.

[0012] (First Embodiment) The camera system 1 that performs the AF operation as described above will be described in more detail. FIG. 3 is a block diagram for explaining the main configuration of the camera system 1 according to the first embodiment. <Interchangeable lens> The interchangeable lens 3 includes a lens-side mount 310, a lens-side control unit 330, a lens-side communication unit 340, a lens-side memory unit 350, an imaging optical system 360, a lens drive unit 370, a diaphragm drive unit 380, and a shake sensor 390. The lens drive unit 370 includes lens drive units 370a and 370b.

[0013] An annular lens-side mount 310 is provided with a lens-side terminal holder 320. The lens-side terminal holder 320 has a plurality of lens-side terminals in an arc shape centered on the optical axis O. The plurality of lens-side terminals include, for example, a mounting detection terminal for notifying the camera body 2 that the interchangeable lens 3 is attached to the camera body 2, a communication terminal used for communication between the interchangeable lens 3 and the camera body 2, a power supply terminal to which power is supplied from the camera body 2 to the interchangeable lens 3, and a grounding terminal (ground), etc.

[0014] The lens-side control unit 330 is composed of a microcomputer and its peripheral circuits, etc. The lens-side control unit 330 executes a control program stored in the lens-side memory unit 350 to control each part of the interchangeable lens 3. The lens-side control unit 330 is connected to the lens-side communication unit 340, the lens-side memory unit 350, the lens drive unit 370a, the lens drive unit 370b, the diaphragm drive unit 380, and the shake sensor 390.

[0015] The lens-side communication unit 340 performs predetermined communication with the body-side communication unit 240. The lens-side communication unit 340 is connected to the lens-side control unit 330 and the above-described communication terminal. Through the communication between the lens-side communication unit 340 and the body-side communication unit 240, a transmission request such as an instruction to move the imaging optical system 360, etc., which will be described later, and information indicating the state of the drive unit for driving the imaging optical system 360, etc., are transmitted to the interchangeable lens 3. Also, through the communication between the lens-side communication unit 340 and the body-side communication unit 240, the drive state of the imaging optical system 360, etc., is transmitted from the interchangeable lens 3 to the camera body 2.

[0016] The state of the drive unit in the interchangeable lens 3 refers to the state where each of the lens drive units 370a and 370b is driving the corresponding focus lens 361a and the shake correction lens 361b, or the state after driving. On the other hand, information indicating the positions of the focus lens 361a and the shake correction lens 361b, the state of the drive unit of the interchangeable lens 3, and information read from the lens-side storage unit 350 are transmitted from the interchangeable lens 3 to the camera body 2.

[0017] The lens-side storage unit 350 is composed of a non-volatile storage medium. The recording and reading of data in the lens-side storage unit 350 are controlled by the lens-side control unit 330. In addition to storing the control programs executed by the lens-side control unit 330, the lens-side storage unit 350 can store data indicating the model name of the interchangeable lens 3 (also referred to as model name information) and data indicating the optical characteristics of the imaging optical system 360. The lens-side storage unit 350 is connected to the lens-side control unit 330.

[0018] The imaging optical system 360 guides subject light to the imaging surface 260S of the imaging element 260 of the camera body 2. The optical axis O of the imaging optical system 360 substantially coincides with the center positions of the lens-side mount 310, the body-side mount 210, and the imaging surface. The imaging optical system 360 includes, for example, a focus lens 361a, a shake correction lens 361b, and a diaphragm 362. At least a part of the imaging optical system 360 is configured to be movable in the direction of the optical axis O by the lens drive unit 370 or manual operation. For example, the focus lens 361a is configured to be able to move forward and backward in the direction of the optical axis O by the lens drive unit 370a. When the focus lens 361a moves, the position of the subject image formed by the imaging optical system 360 is changed. Thereby, the AF operation (focusing) is performed.

[0019] For example, the image stabilization lens 361b is configured to be movable in a direction intersecting the optical axis O by a lens driving unit 370b. When the image stabilization lens 361b moves, the swing (image blur) of the subject image on the imaging surface 260S of the imaging device 260 is suppressed. Image stabilization for moving the image stabilization lens 361b is one of the anti-shake functions of the camera system 1.

[0020] The aperture 362 adjusts the amount of light incident on the imaging device 260. The aperture 362 is configured such that the aperture blades can be driven by an aperture driving unit 380 or manual operation to change the aperture diameter (aperture value). The aperture diameter of the aperture 362 is configured to be detectable by an encoder or the like of the aperture driving unit 380.

[0021] The lens driving units 370a and 370b are each composed of a motor or an actuator and a lens driving mechanism. The lens driving unit 370a moves the focus lens 361a along the optical axis O direction by a driving signal output from the lens side control unit 330. The moving direction, moving amount, moving speed, etc. of the focus lens 361a are instructed by, for example, the body side control unit 230. The position of the focus lens 361a is configured to be detectable by a position detection mechanism such as an encoder of the lens driving unit 370a.

[0022] The lens driving unit 370b moves the image stabilization lens 361b in a direction intersecting the optical axis O by a driving signal output from the lens side control unit 330. The moving direction, moving amount, moving speed, etc. of the image stabilization lens 361b are instructed by, for example, the lens side control unit 330. The position of the image stabilization lens 361b is configured to be detectable by a hall sensor or the like of the lens driving unit 370b. The lens driving unit 370a and the lens driving unit 370b are each connected to the lens side control unit 330.

[0023] The aperture drive unit 380 is composed of a motor and an aperture drive mechanism. The aperture drive unit 380 changes the aperture diameter of the aperture 362, for example, based on an instruction from the lens-side control unit 330. The aperture drive unit 380 is connected to the lens-side control unit 330.

[0024] The shake sensor 390 includes a gyro sensor or the like and detects the shake of the camera system 1 due to hand shake or the like. The shake sensor 390 detects the shake angle component around the X axis and the shake angle component around the Y axis in FIG. 1. The shake sensor 390 may also include an acceleration sensor or the like and detect the shake in a direction orthogonal to the optical axis O. The detection signal from the shake sensor 390 is sent to the lens-side control unit 330. Thereby, so-called anti-shake control is performed. That is, based on the detection signal of the shake sensor 390 sent to the lens-side control unit 330, the correction lens 361b is moved in a direction intersecting the optical axis O by the lens drive unit 370b, thereby suppressing the swing (image shake) of the subject image on the imaging surface 260S of the imaging element 260.

[0025] <Camera body> The camera body 2 has a body-side mount 210, a body-side control unit 230, a body-side communication unit 240, a power supply unit 250, a shutter device 255, an imaging element 260, a sensor drive unit 265, a signal processing unit 270, an operation member 280, and a display unit 290. Since the sensor drive unit 265 is used in the second embodiment, it may be omitted in the first embodiment.

[0026] A body-side terminal holding portion 220 is provided on the annular body-side mount 210. The body-side terminal holding portion 220 has a plurality of body-side terminals and contacts the above-described lens-side terminals. Similar to the lens-side terminals, the plurality of body-side terminals include, for example, a mounting detection terminal that conveys to the camera body 2 that the interchangeable lens 3 is mounted on the camera body 2, a communication terminal used for communication between the camera body 2 and the interchangeable lens 3, a power supply terminal for supplying power from the camera body 2 to the interchangeable lens 3, and a grounding terminal (ground), etc.

[0027] The body-side control unit 230 is composed of a microcomputer and its peripheral circuits, etc. The body-side control unit 230 executes a control program stored in the storage unit 235 to control each part within the camera body 2. The body-side control unit 230 is connected to the body-side communication unit 240, the power supply unit 250, the shutter device 255, the imaging device 260, the sensor driving unit 265, the signal processing unit 270, the operation member 280, and the display unit 290.

[0028] The body-side control unit 230 includes the storage unit 235. The storage unit 235 has its data recording and reading controlled by the body-side control unit 230. In addition to storing the control program etc. executed by the body-side control unit 230, the storage unit 235 can store the model name information of the interchangeable lens 3 received by the body-side communication unit 240, data indicating the optical characteristics of the interchangeable lens 3, etc.

[0029] The body-side communication unit 240 performs the above-described communication with the lens-side communication unit 340. The body-side communication unit 240 is connected to the body-side control unit 230 and the plurality of body-side terminals described above. The power supply unit 250 converts the voltage of a battery (not shown) into a voltage used by each part of the camera system 1 and supplies it to each part of the camera body 2 and the interchangeable lens 3. The power supply unit 250 can switch the power supply on and off for each power supply destination according to an instruction from the body-side control unit 230. The power supply unit 250 is connected to the body-side control unit 230 and the power supply terminals described above.

[0030] The shutter device 255 is a focal plane shutter disposed in front of the imaging device and has a front curtain, a rear curtain, and an actuator mechanism for driving them. The shutter device 255 is controlled to open and close by the body-side control unit 230. When the shutter device 255 (front curtain) opens, light from the subject is guided to the imaging surface 260S of the imaging device 260. When the shutter device 255 (rear curtain) closes, the light from the subject is blocked.

[0031] The imaging device 260 is a solid-state imaging device such as a CMOS image sensor or a CCD image sensor. The imaging device 260 captures a subject image formed on the imaging surface 260S in accordance with a control signal from the body-side control unit 230 and outputs an imaging signal. The imaging device 260 is connected to the body-side control unit 230 and the signal processing unit 270.

[0032] The imaging device 260 has pixels for image generation (referred to as imaging pixels) and pixels for focus detection (referred to as focus detection pixels) disposed on the imaging surface 260S. A signal generated by the imaging pixels (hereinafter referred to as an imaging pixel signal) is used by the signal processing unit 270 described later to generate image data. In addition, a signal generated by the focus detection pixels (hereinafter referred to as a focus detection pixel signal) is used by the signal processing unit 270 described later for a focus detection process to detect the in-focus state of the image by the interchangeable lens 3. Note that the imaging device 260 may be configured to include pixels that output signals usable for both imaging and focus detection.

[0033] The sensor drive unit 265 is constituted by, for example, an actuator and a sensor drive mechanism. The sensor drive unit 265 moves the imaging device 260 in a direction intersecting the optical axis O based on an instruction output from the body-side control unit 230. By moving the imaging device 260, blurring of the subject image with respect to the imaging surface of the imaging device 260 (image blur) is suppressed. The shake correction for moving the imaging device 260 is one of the anti-shake functions of the camera system 1. The position of the moving imaging device 260 is configured to be detectable by a hall sensor or the like of the sensor drive unit 265. The moving direction, moving amount, moving speed, etc. of the imaging device 260 are instructed, for example, from the body-side control unit 230. The sensor drive unit 265 is connected to the body-side control unit 230.

[0034] The signal processing unit 270 performs predetermined image processing on the imaging pixel signals output from the imaging device 260 to generate image data. The generated image data is recorded in a predetermined file format in a storage medium (memory card) (not shown), or is used for displaying a confirmation image of the captured image or a through image before shooting on the display unit 290. The signal processing unit 270 is connected to the body side control unit 230, the imaging device 260, and the display unit 290.

[0035] Also, the signal processing unit 270 uses the pixel signals for focus detection output from the imaging device 260 to calculate the defocus amount, which is the difference between the position of the subject image formed by the interchangeable lens 3 by the phase difference detection method and the imaging surface 260S (FIG. 4) of the imaging device 260. The signal processing unit 270 calculates the movement amount of the focus lens 361a to the in-focus position, which is the position of the focus lens 361a at which the target subject image is in focus on the imaging surface 260S, based on the calculated defocus amount and the position of the focus lens 361a at the time when the pixel signals for focus detection are acquired. The focus drive instruction based on the movement amount of the focus lens 361a calculated by this focus detection calculation is transmitted from the camera body 2 to the interchangeable lens 3 together with data indicating the movement direction, movement amount, etc. of the focus lens 361a.

[0036] The operation member 280 including a release button, operation switches, etc. is provided on the outer surface of the camera body 2. The user gives a shooting instruction, a setting instruction for shooting conditions, etc. by operating the operation member 280. The operation member 280 sends an operation signal corresponding to the user's operation to the body side control unit 230.

[0037] The display unit 290 is configured by, for example, a liquid crystal display panel. The display unit 290 displays an image based on the image data processed by the signal processing unit 270, an operation menu screen, etc. according to an instruction from the body side control unit 230. Also, the display unit 290 may include a touch panel and serve as a part of the operation member 280. The display unit 290 is connected to the body side control unit 230 and the signal processing unit 270.

[0038] The camera body 2 sends, by the above-described communication, for example, a focus drive instruction, an instruction to start an image stabilization operation, a diaphragm drive instruction, a request for information transmission, information on the camera body 2 (imaging mode information, ISO sensitivity, whether or not video recording is in progress, etc.) to the interchangeable lens 3. The interchangeable lens 3 drives the focus lens 361a, starts an image stabilization operation, and drives the diaphragm 362 in response to an instruction from the camera body 2.

[0039] On the other hand, the interchangeable lens 3 sends, by the above-described communication, for example, information indicating the optical characteristics of the imaging optical system 360, the position of the focus lens 361a, the amount of shake detected by the shake sensor 390, the amount of shake corrected by the interchangeable lens 3, information requested from the camera body 2, etc. to the camera body 2.

[0040] FIG. 4 is a diagram for explaining the configuration of the focus detection device according to the first embodiment among the configurations illustrated in FIG. 3. FIG. 4 shows a lens-side control unit 330, a lens-side communication unit 340, a focus lens 361a, a lens drive unit 370a, a body-side control unit 230, a body-side communication unit 240, a shutter device 255, an imaging element 260, and a signal processing unit 270. As described above, the imaging element 260 has an imaging surface 260S on which a light beam from the imaging optical system 360 is incident. The shutter device 255 is disposed in front of the imaging surface 260S (on the imaging optical system 360 side). The shutter device includes a front curtain 255a and a rear curtain 255b. The front curtain 255a and the rear curtain 255b each consist of a plurality of shutter blades and travel downward and upward, respectively, in the FIG. 4 screen. FIG. 4 shows a fully open shutter state before the front curtain 255a has completed moving all its shutter blades downward and before the rear curtain 255b has all its shutter blades waiting in the upward position to close, indicating a state in which a light beam from the imaging optical system 360 is incident on the imaging surface 260S.

[0041] <Explanation of AF operation> Next, the AF operation performed during continuous shooting in which a plurality of images are continuously taken while the release button is pressed in the present embodiment will be described. While the full press operation of the release button is being continued, the camera body 2 performs imaging of a plurality of frames continuously for one frame. The body side control unit 230 starts the charge accumulation operation in the imaging device 260 and drives the front curtain 255a of the shutter device 255 to open. When the body side control unit 230 subsequently drives the rear curtain 255b of the shutter device 255 to close, based on the focus detection pixel signal transferred from the imaging device 260 to the signal processing unit 270, the signal processing unit 270 is made to perform a focus detection calculation.

[0042] Based on the focus detection calculation result, the body side control unit 230 instructs the lens side control unit 330 to perform focus driving via the body side communication unit 240 and the lens side communication unit 340. The lens side control unit 330 moves the focus lens 361a by the lens driving unit 370a in response to the focus driving instruction (focusing control).

[0043] FIG. 5 is a schematic diagram in which 21 frames PS corresponding to the focus area P in FIG. 2 are superimposed on corresponding positions on the imaging surface 260S. The position corresponding to the optical axis O of the imaging surface 260S is set as image height y = 0. Also, the short side direction (vertical direction of the image) of the imaging surface 260S is from image height y = -a to +a. On the imaging surface 260S, the center position of the frame PS is from image height y = -b to +b in the short side direction of the imaging screen 260S. As described with reference to FIG. 4, the front curtain 255a and the rear curtain 255b of the shutter device 255 each consist of a plurality of shutter blades and travel downward from above as indicated by the arrows in FIG. 5. FIG. 5 shows a state in which all the shutter blades of the front curtain 255a have finished opening and moving downward, and all the shutter blades of the rear curtain 255b are waiting above to close.

[0044] The amount of movement of the focus lens 361a calculated by the signal processing unit 270 is the amount of movement from the position of the focus lens 361a at the time when the focus detection pixel signal used for calculating the defocus amount was acquired to the in-focus position calculated starting from that position. The time when the focus detection pixel signal was acquired is the exposure period (charge accumulation period) of the focus detection pixels arranged at the position of the frame PS corresponding to the adopted focus area P, and the position of the frame PS corresponds to the time from the aperture time when the front curtain 255a of the shutter device 255 passes through to the light-shielding time when the rear curtain 255b passes through.

[0045] FIG. 6 is a timing chart for explaining the AF operation performed during continuous shooting. When the front curtain 255a of the shutter device 255 is opened at the n-th frame, the (n + 1)-th frame, and so on, the signal processing unit 270 performs charge accumulation, and after the rear curtain 255b is closed and the charge accumulation ends, the signal processing unit 270 reads out the imaging pixel signal transferred from the imaging device 260 and performs predetermined image processing on the imaging pixel signal to generate an image for one frame. Further, the signal processing unit 270 performs a focus detection calculation based on the focus detection pixel signal read out from the imaging device 260 after the charge accumulation ends and transferred to the signal processing unit 270. The body side control unit 230 instructs the interchangeable lens 3 to perform a focus drive for each shooting frame based on the focus detection calculation result by the signal processing unit 270. For example, a focus drive instruction is given between the accumulation periods of the imaging device 260.

[0046] In the example of FIG. 6, an instruction for focus drive based on the focus detection pixel signal acquired during the imaging of the previous frame is transmitted from the camera body 2 to the interchangeable lens 3 before the next frame is imaged. FIG. 6 shows an example in which the focus lens 361a is moved even during the charge accumulation of the imaging device 260.

[0047] Hereinafter, the (n + 1)-th frame will be described with attention paid thereto. In FIG. 6(a), the horizontal axis represents time, the vertical axis represents the position in the vertical direction of the imaging device 260, and the curve 61 indicates the traveling curve of the front shutter 255a in the imaging of the (n + 1)-th frame (the position of the rearmost end in the traveling direction of the shutter blade of the front shutter 255a). Further, the curve 62 indicates the traveling curve of the rear shutter 255b in the imaging of the (n + 1)-th frame (the position of the foremost end in the traveling direction of the shutter blade of the rear shutter 255a). The body-side control unit 230 outputs a signal for releasing the front shutter 255a to the shutter device 255 at time t0, and outputs a signal for releasing the rear shutter 255b to the shutter device 255 at time t2.

[0048] For the shutter device 255, a first time and a second time are defined as design values. The first time refers to the time from when a signal for releasing the shutter curtain is input until the shutter curtain passes through the position where the image height y = +a. First, the movement of the front curtain 255a will be described. Before the shutter release, the front curtain 255a covers the entire imaging surface 260S, and the rearmost end of the front curtain 255a is located at a position higher (farther) than the image height y = +a. When a signal to release the front curtain 255a is input and the front curtain 255a actually starts to move (arrow in Fig. 5), even in the initial stage, the rearmost end of the front curtain 255a moves from a position higher (farther) than the image height y = +a. When the first time has elapsed (time t1 described later), the rearmost end of the front curtain 255a reaches the uppermost end (image height y = +a) of the imaging surface 260a. After that, the rearmost end of the front curtain 255a moves within the image height -a < y < +a of the imaging surface 260a and stops after exceeding y = -a (moving to a position farther than y = -a). While the front curtain 255a is moving within the image height -a < y < +a, a light beam from the imaging optical system 360 is incident on the imaging surface 260S. That is, when the first time has elapsed, the uppermost part of the imaging surface 260S is opened, and the incidence of the light beam on the uppermost part of the imaging surface 260S is started. As described above, the first time is the delay time from the signal to release the front curtain 255a until the incidence of the light beam on the uppermost part of the imaging surface 260S is started, and is also referred to as the face detection time. The second time refers to the time from when the front curtain passes the position of the image height y = +a until the time (time t4 described later) when it passes the position of the image height y = -a. That is, the second time is the time when the rearmost end of the front curtain 255a passes through the entire imaging surface 260S, and is also referred to as the curtain running time. The foremost end of the rear curtain 255b is located at a position higher (farther) than the image height y = +a before the shutter release. When a signal to release the rear curtain 255b is input and the rear curtain 255b actually starts to move, until the first time has elapsed, the foremost end of the rear curtain 255b moves from a position higher (farther) than the image height y = +a. When the first time has elapsed, the foremost end of the rear curtain 255b reaches the uppermost end (image height y = +a) of the imaging surface 260a. After that, the foremost end of the rear curtain 255a moves within the image height -a < y < +a of the imaging surface 260a and stops after exceeding y = -a (moving to a position farther than y = -a). The foremost end of the rear curtain 255b also passes from the image height y = +a to the image height y = -a during the second time. In the present embodiment, the first hour and the second hour for the front curtain 255a are referred to as the front curtain first hour and the front curtain second hour, respectively. Also, the first hour and the second hour for the rear curtain 255b are referred to as the rear curtain first hour and the rear curtain second hour, respectively. In the present embodiment, the front curtain first hour and the rear curtain first hour are substantially equal, and the front curtain second hour and the rear curtain second hour are substantially equal.

[0049] As described above, at the time t1 when the first hour of the front curtain has elapsed since the time t0, the rearmost end of the front curtain 255a passes through the position where the image height y = +a. As a result, the front curtain 255a starts to open, and the uppermost part of the imaging surface 260S opens (the face appears) (light starts to enter the imaging element 260). The rearmost end of the front curtain 255a passes through the position where the image height y = +b (the position of the frame PS51 in FIG. 5) at the time tb1, passes through the position where the image height y = 0 (the position of the frame PS52 in FIG. 5) at the time t3, passes through the position where the image height y = -b (the position of the frame PS53 in FIG. 5) at the time tb3, and passes through the position where the image height y = -a at the time t4. The time from t1 to t4 is the second hour of the front curtain.

[0050] The foremost end of the rear curtain 255b passes through the position where the image height y = +a at the time t4 when the first hour of the rear curtain has elapsed since the time t2. As a result, the rear curtain 255b starts to close (the light shielding of the imaging element 260 starts). The rear curtain 255b passes through the position where the image height y = +b (the position of the frame PS51 in FIG. 5) at the time tb2, passes through the position where the image height y = 0 (the position of the frame PS52 in FIG. 5) at the time t5, passes through the position where the image height y = -b (the position of the frame PS53 in FIG. 5) at the time tb4, and passes through the position where the image height y = -a at the time t6. The time from t4 to t6 is the second hour of the rear curtain.

[0051] <Calculation of Exposure Timing Based on Image Height> As illustrated in FIG. 5, in the present embodiment, the front curtain 255a and the rear curtain 255b of the shutter device 255 move in the - direction (arrow direction) of the Y axis. Therefore, for the frames PS51, PS52, and PS53 at positions where the image height is different in the Y-axis direction on the imaging surface 260S, the exposure timing of the pixels for focus detection is different because the times when the rearmost end of the front curtain 255a and the foremost end of the rear curtain 255b pass through are different.

[0052] Therefore, the body-side control unit 230 calculates the exposure timing of the focus detection pixels based on the image height of the frame PS corresponding to the adopted focus area P, and calculates the position of the focus lens 361a at the calculated exposure timing. The position information indicating the position of the focus lens 361a is shown by a solid circle (○) in FIG. 6(b). The position information of the focus lens 361a is transmitted from the lens-side control unit 330 to the body-side control unit 230 through communication between the interchangeable lens 3 and the camera body 2 that is performed at predetermined time intervals.

[0053] Based on the position information of the focus lens 361a transmitted from the lens-side control unit 330 and the calculated exposure timing, the body-side control unit 230 calculates the position of the focus lens 361a at the time when the focus detection pixel signal is acquired. The body-side control unit 230 sends the calculated position of the focus lens 361a to the signal processing unit 270. With this configuration, the signal processing unit 270 can appropriately calculate the movement amount of the focus lens 361a from the position of the focus lens 361a at the time when the focus detection pixel signal is acquired to the in-focus position.

[0054] When the focus lens 361a moves during the accumulation period of the imaging device 260, the body-side control unit 230 treats the average position obtained by averaging the positions of the focus lens 361a during the accumulation period as the position of the focus lens 361a at the time when the focus detection pixel signal is acquired. The body-side control unit 230 calculates the average position based on the position information of the focus lens 361a transmitted from the lens-side control unit 330 and the exposure timing calculated as described above. With this configuration, the signal processing unit 270 can appropriately calculate the movement amount of the focus lens 361a from the average position of the focus lens 361a at the time when the focus detection pixel signal is acquired during the movement of the focus lens 361a to the in-focus position.

[0055] <Calculation of Exposure Timing According to Travel Characteristics of Shutter> Generally, the focal plane shutter that constitutes the shutter device 255 is biased by a spring or the like. Therefore, the traveling speeds of the rearmost end of the front curtain 255a and the foremost end of the rear curtain 255b are not constant within the above-mentioned front curtain second time and rear curtain second time. For example, in the first half of the front curtain second time and rear curtain second time (image height y = +a to y = +b), the released front curtain 255a and rear curtain 255b gradually accelerate from a slow speed state. On the other hand, in the second half of the front curtain second time and rear curtain second time, since the traveling speeds of the front curtain 255a and rear curtain 255b have reached the designed speed, they travel at a substantially constant speed from image height y = 0 to y = -a.

[0056] FIG. 7(a) is an enlarged view of the traveling curve of the foremost end of the rear curtain 255b, and is a diagram illustrating the relationship between the image height y on the imaging surface 260S and the time t (FIG. 6(a)) when the rear curtain 255b passes through. The actual traveling curve 71 of the foremost end of the rear curtain 255b is shown by a solid line, and the approximate straight line 72 approximating the traveling curve 71 is shown by a broken line. For the approximate straight line 72, one approximate straight line may be obtained over the entire range (y = +a to y = -a), or two approximate straight lines 72 may be obtained separately for each of y > 0 and y < 0. Alternatively, the straight line 72 may be divided into two, for example, y > +b and +b < y, at the boundary where the speed change of the rear curtain 255b changes significantly, or further divided into three, y > +b, +b < y < -b, and -b < y. As shown in FIG. 6(a), the foremost end of the rear curtain 255b released at time t2 passes through the image height y = +a at time t4, passes through the image height y = +b at time tb2, and passes through the image height y = 0 at time t5. Further, it passes through the image height y = -b at time tb4 and passes through the image height y = -a at time t6.

[0057] As shown by the traveling curve 71, the traveling characteristics of the foremost end of the rear curtain 255b of the shutter device 255 are non-linear in which the curtain traveling time and the traveling distance are not proportional. Therefore, when calculating the exposure timing of the focus detection pixels based on the image height of the position of the frame PS corresponding to the focus area P adopted by the body side control unit 230, simply shifting the exposure timing in proportion to the image height will not make the calculated exposure timing coincide with the actual opening timing of the shutter device 255.

[0058] When calculating the exposure timing of the pixel for focus detection of the frame PS corresponding to the adopted focus area P, the body-side control unit 230 according to this embodiment calculates the exposure timing in accordance with the running characteristics of the shutter device 255. Specifically described, the body-side control unit 230 linearly approximates the running curve 71 as if the relationship between the curtain running time and the running distance is proportional. When linearly approximating the above-described running curve 71, two approximate straight lines 72 are calculated by dividing the region into y > 0 and y < 0 regions. Using the calculated approximate straight line 72, the exposure timing of each frame PS is calculated. The time taken to pass through each frame PS is calculated using the approximate straight line 72 that is proportional to the image height, calculated respectively for y > 0 and y < 0, and the exposure timing is calculated. Note that the exposure timing may be calculated using the running curve 71 without using the approximate straight line 72, or the difference between the actual running curve 71 and the approximate straight line 72 may be corrected for the linearly approximated approximate straight line 72. FIG. 7(b) is a diagram illustrating the relationship between the image height y on the imaging surface 260S and the correction amount in the case of correcting the difference. By configuring in this way, the calculation process of the exposure timing can be calculated simply and accurately.

[0059] With reference to FIGS. 5 to 7, the calculation of the exposure timing of the frames PS51, PS52, and PS53 will be described. In the storage unit 235 of the body-side control unit 230, data indicating the approximate straight line 72 in FIG. 7(a) is stored. Based on this approximate straight line 72, the time when the leading edge of the rear curtain 255b passes is calculated. For example, in the frame PS52 in FIG. 5, the time when the leading edge of the rear curtain 255b passes y = 0, and the exposure timing is calculated as t5 from the approximate straight line 72 in FIG. 7. Note that it may be calculated using the traveling curve 71. Data indicating the traveling curve 71 in FIG. 7(a) is stored in the storage unit 235 of the body side control unit 230. The traveling curve 71 is measured, for example, at the time of manufacture, as the traveling curve of the rear curtain 255b, and stored in the storage unit 235. Instead of storing the traveling curve 71, an approximate curve 72 and the correction amount in FIG. 7(b) may be stored. In that case, the traveling curve 71 in FIG. 7(a) can be calculated by correcting the approximate straight line 72 with the correction amount in FIG. 7(b). The correction amount in FIG. 7(b) may be obtained by actually measuring in advance the curtain traveling time of the shutter device 255, or a value based on the design value of the shutter device 255 may be adopted. The body side control unit 230 calculates the time when the leading end of the rear curtain 255b passes based on the traveling curve 71, starting from the time t2 when a signal for releasing the rear curtain 255b to the shutter device 255 is output. Also, in this embodiment, the exposure timing is obtained from the traveling curve 71 or the approximate straight line of the leading end of the rear curtain 255b, but the trailing end of the front curtain 255a may be used. Further, for each frame PS, the timing when the leading end of the front curtain 255a passes and the timing when the leading end of the rear curtain 255b passes may be calculated respectively, and the timing in the middle of the two may be calculated as the exposure timing.

[0060] (Frame PS51) When calculating the exposure timing of the frame PS51, the body-side control unit 230 calculates the rear curtain first time (51) and the rear curtain second time (51) based on the approximate straight line 72 to obtain the time when the leading edge of the rear curtain 255b passes through the frame PS51. The rear curtain first time (51) is the time from when the signal for releasing the rear curtain 255b, which is calculated based on the approximate straight line 72, is input until the leading edge of the rear curtain 255b reaches the image height y = +a. The rear curtain second time (51) is the time that the leading edge of the rear curtain 255b travels from the image height y = +a to the image height y = +b where the frame PS51 is located, which is calculated based on the approximate straight line 72. That is, the rear curtain first time (51) corresponds to the time from time t2 to time t4 (see FIG. 6), and the rear curtain second time (51) corresponds to the time from time t4 to time tb2 (see FIG. 7). The time tb2 is the accumulation end time at the position of the frame PS51. The body-side control unit 230 calculates the time tb1 by going back the accumulation time from the time tb2 and sets it as the accumulation start time. Through the above calculations, the exposure timing of the frame PS51 is from the time tb1 to the time tb2. In this embodiment, the time when the rear curtain 255b passes through the middle of the frame PS51 is set as the accumulation end time. However, the time when the rear curtain 255b passes through one side in the positive Y-axis direction (the uppermost end of the frame PS52) of the frame PS52, or the time when the rear curtain 255b passes through one side in the negative Y-axis direction (the lowermost end of the frame PS52) of the frame PS52 may also be set as the accumulation end time.

[0061] (frame PS52) When calculating the exposure timing of the frame PS52, the body side control unit 230 calculates the rear curtain first time (52) and the rear curtain second time (52) based on the approximate straight line 72 to obtain the time when the leading edge of the rear curtain 255b passes through the frame PS52. The rear curtain first time (52) is the time from when the signal for releasing the rear curtain 255b, which is calculated based on the approximate straight line 72, is input until the leading edge of the rear curtain 255b reaches the image height y = +a, and is the same as the above-mentioned rear curtain first time (51). The rear curtain second time (52) is the time for the leading edge of the rear curtain 255b to travel from the image height y = +a to the image height y = 0 where the frame PS52 is located, which is calculated based on the approximate straight line 72. That is, the rear curtain first time (52) corresponds to the time from time t2 to time t4 (see FIG. 6), and the rear curtain second time (52) corresponds to the time from time t4 to time t5 (see FIG. 7). Time t5 is the accumulation end time at the position of the frame PS52. The body side control unit 230 calculates time t3 by going back the accumulation time from time t5 and sets it as the accumulation start time. Through the above calculations, the exposure timing of the frame PS52 is from time t3 to time t5.

[0062] (Frame PS53) When calculating the exposure timing of frame PS53, the body side control unit 230 calculates the rear curtain first time (53) and the rear curtain second time (53) based on the approximate straight line 72 to obtain the time when the leading edge of the rear curtain 255b passes through frame PS53. The rear curtain first time (53) is the time from when the signal for releasing the rear curtain 255b, which is calculated based on the approximate straight line 72, is input until the leading edge of the rear curtain 255b reaches the image height y = +a, and is the same as the above-mentioned rear curtain first time (51). The rear curtain second time (53) is the time for the leading edge of the rear curtain 255b to travel from the image height y = +a to the image height y = -b where frame PS53 is located, which is calculated based on the approximate straight line 72. That is, the rear curtain first time (53) corresponds to the time from time t2 to time t4 (see FIG. 6), and the rear curtain second time (51) corresponds to the time from time t4 to time tb4 (see FIG. 7). Time tb4 is the accumulation end time at the position of frame PS53. The body side control unit 230 calculates time tb3 by going back the accumulation time from time tb4 and sets it as the accumulation start time. Through the above calculations, the exposure timing of frame PS53 is from time tb3 to time tb4.

[0063] Summarizing the above description, it is as follows. Since the front curtain 255a and the rear curtain 255b of the shutter device 255 move in the Y-axis direction, for frames PS51, PS52, and PS53 at positions with different image heights in the Y-axis direction on the imaging surface 260S, the times when the trailing edge of the front curtain 255a and the leading edge of the rear curtain 255b pass through are different. As a result, the exposure timings of the focus detection pixels in frames PS51, PS52, and PS53 are different.

[0064] When the exposure timings of the focus detection pixels in frames PS51, PS52, and PS53 are different, when the focus lens 361a is moving, the average positions of the focus lens 361a at the time when the focus detection pixel signals are respectively acquired in frames PS51, PS52, and PS53 are different.

[0065] However, the body - side control unit 230 calculates the exposure timing of the focus - detection pixels in the corresponding frames PS51, PS52, PS53 based on the image height of the frame PS corresponding to the adopted focus area P, and calculates the average position of the focus lens 361a at the calculated exposure timing. As shown in FIG. 6(b), the body - side control unit 230 of the camera body 2 calculates the average position of the focus lens 361a at the time when the focus - detection pixel signal is acquired based on the position information of the focus lens 361a transmitted from the lens - side control unit 330 and the calculated exposure timing. The body - side control unit 230 sends the calculated average position of the focus lens 361a to the signal - processing unit 270. By configuring in this way, the signal - processing unit 270 can appropriately calculate the moving amount of the focus lens 361a from the average position of the focus lens 361a at the time when the focus - detection pixel signal is acquired to the in - focus position.

[0066] <Change according to pupil position> The length of the rear curtain first time and the rear curtain second time is corrected according to the pupil position of the imaging optical system 360. In the present embodiment, the distance from the position of the exit pupil of the imaging optical system 360 to the imaging surface 260S is referred to as the pupil distance. FIG. 8 is a schematic diagram showing the pupil distance and the light rays incident on the imaging surface 260S. FIGS. 8(a), (b), and (c) show cases where the pupil distances of the optical systems are different. The pupil distances are (b) < (a) < (c).

[0067] Generally, due to the optical characteristics of the imaging optical system 360, in the central part of the imaging surface 260S close to the optical axis O, the light passing through the imaging optical system 360 is incident substantially vertically, while the higher the image height on the imaging surface 260S, the more obliquely the light passing through the imaging optical system 360 is incident. The angle of the light passing through the imaging optical system 360 and incident obliquely increases as the pupil distance becomes shorter.

[0068] The position where the shutter curtains 255a and 255b travel is closer to the imaging optical system 360 than the imaging surface 260S. Therefore, as can be clearly seen in FIG. 8(b), when a light ray is obliquely incident on a position with a high image height, the image height h1 at which the shutter curtains 255a and 255b of the shutter device 255, which are located closer to the imaging optical system 360 than the imaging surface 260S, block the light ray is different from the image height h2 of the light ray that actually enters the imaging surface 260S. The difference between the image height h1 and the image height h2 increases as the pupil distance becomes shorter. The difference g2 between the image height h1 and the image height h2 in FIG. 8(b) is larger than the difference g1 between the image height h1 and the image height h2 in FIG. 8(a), and the difference g1 between the image height h1 and the image height h2 in FIG. 8(a) is larger than the difference g3 between the image height h1 and the image height h2 in FIG. 8(c).

[0069] The lens side control unit 330 changes the rear curtain first time and the rear curtain second time for the rear curtain 255b depending on the pupil distance. Specifically, the shorter the pupil distance of the imaging optical system 360, the longer the rear curtain first time is corrected, and the shorter the end time of the rear curtain second time is corrected. By configuring in this way, it is possible to appropriately determine the exposure timing of the focus detection pixels in consideration of the difference in exposure time (charge accumulation time) caused by the difference between the image height h1 at which the shutter curtains 255a and 255b exist and the image height h2 of the light beam actually incident on the imaging surface 260S depending on the pupil distance of the imaging optical system 360.

[0070] In addition, by appropriately determining the exposure timing of the focus detection pixels while taking into account the difference in exposure time (charge accumulation time) caused by the difference between the image height h1 at which the shutter curtain exists and the image height h2 of the light ray actually incident on the imaging surface 260S, the signal processing unit 270 can appropriately calculate the amount of movement of the focus lens 361a to the in-focus position, starting from the average position of the focus lens 361a during the exposure time (charge accumulation time) when the focus detection pixel signal was acquired.

[0071] The corrected rear curtain first time and rear curtain second time may be stored in the storage unit 235 as table values. FIG. 9 is a diagram illustrating the table values. In the table of FIG. 9, for the interchangeable lens A corresponding to the pupil position of FIG. 8(a), the interchangeable lens B corresponding to the pupil position of FIG. 8(b), and the interchangeable lens C corresponding to the pupil position of FIG. 8(c), the values of the first time (51), second time (51), first time (52), second time (52), first time (53), and second time (53) of the frames PS51, PS52, and PS53 at positions where the image height is different in the Y-axis direction on the imaging surface 260S are stored respectively.

[0072] In the present embodiment, since the front curtain first time and the rear curtain first time are substantially equal, and the front curtain second time and the rear curtain second time are substantially equal, one table is sufficient. If the running performances of the front curtain 255a and the rear curtain 255b are different, for example, if the front curtain first time and the rear curtain first time are different, or if the front curtain second time and the rear curtain second time are different, tables may be prepared correspondingly. When there are four or more types of interchangeable lenses 3, the values of the additional interchangeable lenses may be added to the table of FIG. 9. Further, when a focus area is added in addition to the frames PS51, PS52, and PS53 at positions where the image height is different in the Y-axis direction on the imaging surface 260S, the values may be added to the table of FIG. 9 for the added positions.

[0073] According to the first embodiment described above, the following operational effects can be obtained. (1) In the present embodiment, in continuous shooting, the focus lens is driven for the next imaging based on the position of the focus lens in which charges are being accumulated in the focus detection pixels and the calculated defocus amount, so that the focusing speed of the focus lens is increased. In addition, since imaging is performed even while the focus lens is being driven, the imaging speed can be increased. Also, the speed of continuous shooting can be increased. Even if the rear curtain of the shutter has non-linear traveling characteristics where its traveling speed is not constant, based on the light-shielding time by the rear curtain, the exposure timing of the pixels for focus detection can be appropriately obtained. Obtaining the appropriate exposure timing of the pixels for focus detection leads to correctly obtaining the position of the focus lens, which is the basis for calculating the driving amount of the focus lens.

[0074] (2) Based on the light-shielding time by the rear curtain according to the traveling curve of the shutter device, the exposure timing of the pixels for focus detection can be appropriately obtained.

[0075] (3) Obtain the light-shielding timing (aperture time) corresponding to the position of the frame corresponding to the focus area (in-focus area) in the imaging device. With this configuration, even if the passing times of the rear curtain are different in frames at a plurality of positions where the image height is different in the traveling direction (Y-axis direction) of the rear curtain on the imaging surface, the exposure timing of the pixels for focus detection can be appropriately obtained at each position.

[0076] (4) Use the information on the exit pupil distance of the imaging optical system to obtain the light-shielding timing. With this configuration, considering the difference in exposure time (charge accumulation time) caused by the difference in the image height where the rear curtain blocks the light rays and the image height of the light rays actually incident on the imaging surface due to the difference in the exit pupil distance of the imaging optical system, the exposure timing of the pixels for focus detection can be appropriately obtained.

[0077] (5) The shutter has a front curtain that starts the exposure of the imaging device and a rear curtain that shields the light. With this configuration, based on the exposure start time by the front curtain and the light-shielding time by the rear curtain, the exposure timing of the pixels for focus detection can be appropriately obtained.

[0078] (Second Embodiment) In the second embodiment, the imaging element 260 is moved in a direction intersecting the optical axis O using the sensor driving unit 265 of the camera body 2 to perform shake correction. The main configuration of the camera system 1 according to the second embodiment is the same as that in FIG. 3. The body side control unit 230 corrects the lengths of the rear curtain first time and the rear curtain second time described in the first embodiment according to the amount of movement (moved position) of the imaging element 260 in the direction intersecting the optical axis O. This will be described in detail below.

[0079] FIG. 10 is a diagram for explaining the configuration of the focus detection device according to the second embodiment among the configurations illustrated in FIG. 3. FIG. 10 shows a lens side control unit 330, a lens side communication unit 340, a focus lens 361a, a lens driving unit 370a, an image stabilization lens 361b, a lens driving unit 370b, a shake sensor 390, a body side control unit 230, a body side communication unit 240, a shutter device 255, an imaging element 260, a sensor driving unit 265, and a signal processing unit 270.

[0080] <Explanation of the shake correction operation> The shake sensor 390 is constituted by, for example, an angular velocity sensor 390a and an acceleration sensor 390b. The angular velocity sensor 390a detects the angular velocity generated by the rotational movement of the camera system 1. The angular velocity sensor 390a detects the rotation around each axis of, for example, an axis parallel to the X axis, an axis parallel to the Y axis, and an axis parallel to the optical axis O, and sends the detection signal to the lens side control unit 330. The angular velocity sensor 390a is also referred to as a gyro sensor.

[0081] Further, the acceleration sensor 390b detects the acceleration generated by the translational movement of the camera system 1. The acceleration sensor 390b detects the acceleration in the directions of, for example, an axis parallel to the X axis and an axis parallel to the Y axis, and sends the detection signal to the lens side control unit 330. The acceleration sensor 390b is also referred to as a G sensor. Note that the shake sensor 390 may be disposed within the camera body 2. Both the angular velocity sensor 390a and the acceleration sensor 390d may be disposed within the camera body 2, or either one may be disposed within the camera body 2 and the other may be disposed within the interchangeable lens 3.

[0082] The camera system 1 is configured to be capable of performing shake correction by driving the shake correction lens 361b by the lens drive unit 370b and shake correction by driving the imaging element 260 by the sensor drive unit 265. Therefore, for example, shake correction is performed by driving the shake correction lens 361b based on a detection signal from the shake sensor 390, and for the remaining (residual) shake amount after shake correction by the shake correction lens 361b, the imaging element 260 is driven to perform shake correction.

[0083] Generally, the shake generated in the camera system 1 is divided into angular shake associated with the rotational movement of the camera system 1 and translational shake associated with the translational movement of the camera system 1. The lens side control unit 330 calculates the angular shake and the translational shake respectively based on the detection signal of the shake sensor 390. The lens side control unit 330 calculates, for example, the angular shake in the Y-axis direction due to the rotational movement using the detection signal around the axis parallel to the X-axis (Pitch direction) by the angular velocity sensor 390a. Also, the lens side control unit 330 calculates the angular shake in the X-axis direction due to the rotational movement using the detection signal around the axis parallel to the Y-axis (Yaw direction) by the angular velocity sensor 390a.

[0084] Furthermore, the lens side control unit 330 calculates the translational shake in the X-axis direction due to the translational movement using the detection signal in the X-axis direction by the acceleration sensor 390b. Also, the lens side control unit 330 calculates the translational shake in the Y-axis direction due to the translational movement using the detection signal in the Y-axis direction by the acceleration sensor 390b.

[0085] Then, the lens side control unit 330 adds up the angular shake in the X-axis direction and Y-axis direction and the translational shake in the X-axis direction and Y-axis direction for each of the X-axis and Y-axis to calculate the total shake amount in the X-axis direction and Y-axis direction. For example, when the directions of the angular shake and the translational shake calculated for a certain axis direction are the same, the total shake amount increases by addition, but when the directions of the two calculated shakes are different (there is a component in the opposite direction in the direction), the total shake amount decreases by addition. In this way, the addition operation is performed by attaching positive and negative signs according to the directions of the angular shake and the translational shake of each axis.

[0086] Based on the total amount of shake in the X-axis direction and Y-axis direction after addition, the lens-side control unit 330 further calculates the total amount of imaging plane shake converted to the position on the imaging plane 260S of the imaging device 260 for each of the X-axis direction and the Y-axis direction.

[0087] For example, the lens-side control unit 330 calculates, for each of the X-axis direction and the Y-axis direction, the target position of the shake correction lens 361b for moving the shake correction lens 361b in a direction to cancel out the amount of shake with a predetermined sharing ratio among the calculated total amounts of imaging plane shake. The sharing ratio is the ratio of the amount of shake correction performed by the interchangeable lens 3 to the amount of shake correction performed by the camera body 2.

[0088] The lens-side control unit 330 that has calculated the target position of the shake correction lens 361b outputs a drive signal to the lens drive unit 370b to drive the shake correction lens 361b. The lens drive unit 370b that has received the drive signal moves the shake correction lens 361b in the X-axis and Y-axis directions intersecting the optical axis O to the target position in the X-axis direction and the target position in the Y-axis direction, respectively.

[0089] On the other hand, the body-side control unit 230 calculates, for each of the X-axis direction and the Y-axis direction, the target position of the imaging device 260 for moving the imaging device 260 in a direction to cancel out the amount of shake with the above sharing ratio among the total amounts of imaging plane shake received by the body-side communication unit 240 through communication.

[0090] The body-side control unit 230 that has calculated the target position of the imaging device 260 outputs a drive signal to the sensor drive unit 265 to drive the imaging device 260. The sensor drive unit 265 that has received the drive signal moves the imaging device 260 in the X-axis and Y-axis directions intersecting the optical axis O to the target position in the X-axis direction and the target position in the Y-axis direction, respectively. In the above description, the result obtained by adding the angular shake and the translational shake is shared between the shake correction amount performed by the interchangeable lens 3 and the shake correction amount performed by the camera body 2. However, for example, the angular shake correction may be performed by the interchangeable lens 3 (lens-side control unit 330), and the translational shake correction may be performed by the camera body 2 (body-side control unit 230).

[0091] <Changes during shake correction> When the moving direction of the imaging element 260 moved by the sensor driving unit 265 has a component in the Y-axis direction, since the shutter device 255 is fixed to the camera body, the relative positional relationship in the Y-axis direction between the imaging element 260 and the shutter device 255 changes. That is, the relative position of the imaging element 260 with respect to the shutter curtains 255a and 255b that travel changes as the imaging element 260 moves in the Y-axis direction for shake correction. Focusing on the rear curtain 255b, changes occur in the above-described first rear curtain time and second rear curtain time. Therefore, the body-side control unit 230 corrects the lengths of the first rear curtain time and the second rear curtain time as follows based on the Y-axis component of the calculated target position of the imaging element 260.

[0092] For example, when the direction in which the rear curtain 255b travels is the same as the direction in which the imaging element 260 moves for shake correction (when the imaging element 260 moves in the - direction of the Y-axis), the traveling speed of the rear curtain 255b with respect to the imaging element 260 relatively decreases. In this case, the body-side control unit 230 corrects both the first rear curtain time and the second rear curtain time to be longer as the traveling speed of the rear curtain 255b with respect to the imaging element 260 decreases. By configuring in this way, when the sensor driving unit 265 that performs shake correction moves the imaging element 260 in the same direction as the traveling direction of the rear curtain 255b, the body-side control unit 230 can appropriately obtain the exposure timing of the pixels for focus detection in consideration of the decrease in the traveling speed of the rear curtain 255b with respect to the imaging element 260.

[0093] Further, by appropriately determining the exposure timing of the pixels for focus detection in consideration of the decrease in the running speed of the rear curtain 255b with respect to the imaging element 260 due to the above-mentioned shake correction, the signal processing unit 270 can appropriately calculate the amount of movement of the focus lens 361a from the average position of the focus lens 361a at the exposure time (charge accumulation time) when the focus detection pixel signal is acquired to the in-focus position.

[0094] Unlike the above, when the direction in which the rear curtain 255b travels is opposite to the direction in which the imaging element 260 moves for shake correction (when the imaging element 260 moves in the + direction of the Y axis), the running speed of the rear curtain 255b with respect to the imaging element 260 relatively increases. In this case, the body-side control unit 230 corrects both the first rear curtain time and the second rear curtain time shorter as the running speed of the rear curtain 255b with respect to the imaging element 260 increases. By configuring in this way, when the sensor drive unit 265 that performs shake correction moves the imaging element 260 in the direction opposite to the traveling direction of the rear curtain 255b, the body-side control unit 230 can appropriately determine the exposure timing of the pixels for focus detection in consideration of the increase in the running speed of the rear curtain 255b with respect to the imaging element 260.

[0095] Further, by appropriately determining the exposure timing of the pixels for focus detection in consideration of the increase in the running speed of the rear curtain 255b with respect to the imaging element 260 due to the above-mentioned shake correction, the signal processing unit 270 can appropriately calculate the amount of movement of the focus lens 361a from the average position of the focus lens 361a at the exposure time (charge accumulation time) when the focus detection pixel signal is acquired to the in-focus position. In the above second embodiment, an example is shown in which shake correction is performed by driving the shake correction lens 361b by the lens drive unit 370b and shake correction is performed by driving the imaging element 260 by the sensor drive unit 265, but only the shake correction for driving the imaging element 260 may be performed. That is, the interchangeable lens 3 does not include the shake correction lens 361b, and shake correction may be performed by driving the imaging element 260 by the sensor drive unit 265 according to an instruction from the body-side control unit 230.

[0096] According to the focus detection device according to the second embodiment described above, in addition to the same operational effects as those of the first embodiment, the following operational effects can be obtained. That is, the focus detection device includes a sensor drive unit 265 that drives the imaging device 260 and a sensor drive unit 265 that detects the position of the imaging device 260, and the body-side control unit 230 obtains the light shielding time using the position detected by the sensor drive unit 265. With such a configuration, even if the running speed of the rear curtain 255b of the shutter device 255 relative to the imaging device 260 changes, the body-side control unit 230 can appropriately obtain the light shielding time of the focus detection pixels in consideration of the change in the relative running speed of the rear curtain 255b. As a result, the signal processing unit 270 can appropriately calculate the movement amount of the focus lens 361a from the average position of the focus lens 361a at the actual charge accumulation time to the focus position.

[0097] (Modification 1) In the above description, the shutter device 255 having the front curtain 255a and the rear curtain 255b has been described as an example, but the front curtain 255a may be omitted and only a shutter device having a counterpart of the rear curtain 255b may be provided. The body-side control unit 230 starts the charge accumulation operation on the imaging device 260 by electronic shutter control, and then drives the shutter device 255 to close. The body-side control unit 230 causes the signal processing unit 270 to perform focus detection calculation based on the focus detection pixel signal transferred from the imaging device 260 to the signal processing unit 270.

[0098] In the case of Modification 1, the time to start the charge accumulation operation for the focus detection pixels arranged at the position of the frame PS corresponding to the adopted focus area P by electronic shutter control corresponds to the accumulation start time calculated in the above-described embodiment. That is, when calculating the exposure timing of the frame PS51, the time tb1 obtained by going back the accumulation time from the time tb2 which is the accumulation end time at the position of the frame PS51 is calculated and used as the accumulation start time. Also, when calculating the exposure timing of the frame PS52, the time t3 obtained by going back the accumulation time from the time t5 which is the accumulation end time at the position of the frame PS52 is calculated and used as the accumulation start time. Furthermore, when calculating the exposure timing of the frame PS53, a time tb3 obtained by tracing back the accumulation time from a time tb4 which is the end time of accumulation at the position of the frame PS53 is calculated, and this time tb3 is set as the accumulation start time.

[0099] (Modification 2) When continuously shooting a scene where a moving main subject approaches the camera system 1, the body-side control unit 230 may predict the position of the focus lens 361 based on the calculation results of the defocus amount in a plurality of frames. FIG. 11 is a timing chart for explaining the AF operation performed during continuous shooting. Compared with the timing chart of FIG. 6, it is the same as FIG. 6 except that the position of the focus lens is different. The body-side control unit 230 instructs the interchangeable lens 3 to perform focus driving for each frame based on the focus detection calculation result calculated by the signal processing unit 270 for each frame.

[0100] When the defocus amount calculated based on the focus detection pixel signal acquired during imaging of the previous frame increases for the (n - 1)-th frame, n-th frame, and (n + 1)-th frame, for example, based on the rate of increase in the defocus amount for a plurality of past frames, the body-side control unit 230 predicts the movement amount of the focus lens 361a to the in-focus position. When calculating the target position of the focus lens 361a based on the focus detection pixel signal acquired during imaging of the (n + 1)-th frame, in a normal case the target position is set to Q1, while in Modification 2 the target position is set to Q2 taking into account the rate of increase in the defocus amount. By configuring in this way, when continuously shooting a fast-moving main subject, it is possible to continuously focus on the main subject. Note that when continuously shooting a scene where a moving main subject moves away from the camera system 1, the body-side control unit 230 may also predict the position of the focus lens 361 based on the calculation results of the defocus amount in a plurality of frames in the same manner as described above.

[0101] When calculating the movement amount of the focus lens 361a while predicting the change in the defocus amount as in the second modification, if the average position of the focus lens 361a during the accumulation period is incorrect, it is difficult to continue focusing. However, since the body side control unit 230 calculates the average position based on the exposure timing calculated according to the above-described embodiment and the position information of the focus lens 361a transmitted from the lens side control unit 330, the average position of the focus lens 361a during the accumulation period can be correctly obtained. Therefore, it is also suitable for the case of calculating the movement amount of the focus lens 361a while predicting the change in the defocus amount.

[0102] According to the second modification, the following operational effects can be obtained. That is, since the position of the focus lens is predicted based on a plurality of calculation results, for example, it is possible to continue focusing on the main subject when continuously shooting a fast-moving main subject.

[0103] (Second Modification) In the above-described embodiment, the case where the position information of the focus lens 361a during the charge accumulation of the imaging element 260 can be acquired has been described as an example. When the position information of the focus lens 361a during the charge accumulation cannot be acquired, the movement amount of the focus lens 361a up to the in-focus position may be calculated starting from the latest position information acquired before the charge accumulation or the latest position information acquired after the charge accumulation. Alternatively, a weighted average of the latest position information acquired before and after the charge accumulation may be taken, and the movement amount of the focus lens 361a up to the in-focus position may be calculated starting from the weighted average position information.

[0104] (Third Modification) In the above-described embodiment, an example in which the focus detection pixel signal is acquired (charge is accumulated) while the focus lens 361a is moving has been described. However, the focusing lens 361a may be stopped without being moved during the charge accumulation.

[0105] The present invention is not limited to the above-described content. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Description of Reference Numerals

[0106] 1... Camera system, 2... Camera body, 3... Interchangeable lens, 230... Body-side control unit, 235... Storage unit, 240... Body-side communication unit, 255... Shutter device, 255a... Front curtain, 255b... Rear curtain, 260... Image sensor, 265... Sensor drive unit, 270... Signal processing unit, 330... Lens-side control unit, 340... Lens-side communication unit, 350... Lens-side storage unit, 360... Imaging optical system, 370... Lens drive unit, P... Focus area

Claims

Claim 1 An imaging unit that photoelectrically converts light that has passed through an optical system including a focus lens, accumulates charges, and outputs a signal used for focus detection, and that captures a subject image formed by a light beam that has passed through the optical system; A defocus calculation unit that calculates a defocus amount, which is the amount of deviation between the position of the subject image and the position of the imaging surface of the imaging unit, based on the signal; A timing calculation unit that calculates an accumulation timing at which the pixels corresponding to the at least one focus area accumulate charges, based on position information of at least one focus area selected from among a plurality of focus areas; An acquisition unit that acquires position information of the focus lens; An arithmetic unit that calculates a driving amount of the focus lens based on the position of the focus lens at the accumulation timing determined based on the position information of the focus lens and the defocus amount calculated by the defocus calculation unit; A focus detection device having the above components.

Images