Focus detection device

Abstract

To improve the accuracy of focus detection predictions. [Solution] The focus detection device has multiple pixels that convert light that has passed through an optical system including a focus lens into photoelectric data to accumulate charge and output a signal used for focus detection, and includes an imaging unit that captures an image of a subject 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, a timing calculation unit that calculates the accumulation timing at which a pixel corresponding to at least one focus area accumulates charge based on the 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, and a calculation unit that calculates the amount of drive 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.

Description

[Technical Field]

[0001] The present invention relates to a focus detection apparatus. [Background Art]

[0002] There is known a camera that performs focus detection based on signals obtained from focus detection pixels of an image sensor (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] Japanese Unexamined Patent Publication No. 2018-37959 [Summary of the Invention]

[0004] A focus detection apparatus according to a first aspect of the present invention comprises: an imaging unit that includes a plurality of pixels which photoelectrically convert light that has passed through an optical system including a focus lens, accumulate electric charge, and output signals used for focus detection, and which captures a subject image formed by a light flux that has passed through the optical system; a defocus calculation unit that calculates, based on the signals, a defocus amount which is a deviation amount between a position of the subject image and a position of an imaging surface of the imaging unit; a timing calculation unit that calculates, based on position information of at least one focus area selected from among a plurality of focus areas, an accumulation timing at which the pixels corresponding to the at least one focus area accumulate electric charge; an acquisition unit that acquires position information of the focus lens; and a calculation unit that calculates a drive 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] FIG. 1 is a perspective view illustrating an example of a camera system. [Figure 2] This is a diagram illustrating an example of a focus area set within an imaging field of view. [Figure 3] This is a block diagram for explaining the main configuration of a camera system. [Figure 4] This is a diagram illustrating an example of the configuration of a focus detection device. [Figure 5] This is a schematic diagram in which a frame corresponding to a focus area is superimposed on a corresponding position of an imaging surface. [Figure 6] FIG. 6(a) is a diagram showing travel curves of a front curtain and a rear curtain in imaging of the (n+1)-th frame, and FIG. 6(b) is a diagram explaining an AF operation performed during continuous shooting. [Figure 7] FIG. 7(a) is an enlarged diagram of the travel curve of the rear curtain, and FIG. 7(b) is a diagram illustrating an example of the relationship between image height on the imaging surface and a correction amount. [Figure 8] FIG. 8 is a schematic diagram showing a pupil position and light rays incident on an imaging surface. FIG. 8(a) is a diagram showing a case of a standard exit pupil distance, FIG. 8(b) is a diagram showing a case where the exit pupil distance is shorter than that in FIG. 8(a), and FIG. 8(c) is a diagram showing a case where the exit pupil distance is longer than that in FIG. 8(a). [Figure 9] This is a diagram illustrating an example of a table storing a first rear curtain time and a second rear curtain time after correction. [Figure 10] This is a diagram illustrating an example of the configuration of a focus detection device according to a second embodiment. [Figure 11] This is a diagram explaining an AF operation performed during continuous shooting. DETAILED DESCRIPTION OF THE INVENTION

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

[0007] Figure 2 shows the shooting field of view 50 captured by the image sensor 260 of the camera body 2. It also illustrates the focus areas P within the shooting field of view 50, and is shown along with the captured image. The imaging area 50 has 21 focus areas P. Focus areas are also referred to as focus detection areas, focus detection positions, distance measurement points, and autofocus (AF) points. Note that the number and location of the focus areas P shown are merely examples and are not limited to the configuration in Figure 2.

[0008] The focus detection device, as explained in detail in Figure 4, detects the amount of defocus (focus shift) between the position of the subject image formed by the light beam passing through the interchangeable lens 3 and the position of the imaging surface 260S of the image sensor 260 of the camera body 2. To do this, it detects the amount of image shift (phase difference) of the subject image caused by a pair of light beams passing through different pupils of the interchangeable lens 3 for each focus area P. Then, for example, it performs an AF operation by adjusting the position of the focus lens included in the interchangeable lens 3 so that the position of the subject image in the region corresponding to the selected focus area P is aligned with the position of the imaging surface 260S of the image sensor 260 (in focus).

[0009] The focus area P used for AF operation can be selected arbitrarily by the user or automatically by the camera body 2. In AF mode where the focus area P is selected by the user, the focus detection device detects the amount of image shift of the subject image within the selected focus area P. The focus detection device then performs AF operation to focus on the subject within the selected focus area P.

[0010] Furthermore, in AF modes where the focus area P is automatically selected, the camera body 2 selects at least one of the 21 focus areas P mentioned above. For example, in the example shown in Figure 2, if the mode for focusing on a person's face is selected, the camera body 2 selects two focus areas P(i) and P(ii) that are included in the person's face, and detects the amount of image shift of the subject image for each of these two focus areas P(i) and P(ii).

[0011] The focus detection device selects focus area P(ii) from two focus areas P(i) and P(ii) if, for example, P(ii) is the closest to camera system 1 or has the highest contrast. The focus detection device then performs AF operation to focus on the face located in the selected focus area P(ii). Furthermore, the focus detection device can perform AF operation to focus on the face area by considering the defocus amounts of both focus areas P(i) and P(ii) selected as being included in the face area. For example, it may calculate the average of the two defocus amounts and drive the focus lens (AF operation) with the calculated average defocus amount, or it may calculate a weighted average so that the two defocus amounts are as close to the depth of field as possible and perform AF operation.

[0012] (First embodiment) The camera system 1 that performs the AF operation described above will now be explained in more detail. Figure 3 is a block diagram illustrating the main components of the camera system 1 according to the first embodiment. <Interchangeable Lens> The interchangeable lens 3 comprises a lens-side mount 310, a lens-side control unit 330, a lens-side communication unit 340, a lens-side storage unit 350, an imaging optical system 360, a lens driving unit 370, an aperture driving unit 380, and a shake sensor 390. The lens driving unit 370 includes lens driving units 370a and 370b.

[0013] The annular lens-side mount 310 is provided with a lens-side terminal holding portion 320. The lens-side terminal holding portion 320 has a plurality of lens-side terminals arranged in an arc centered on the optical axis O. The plurality of lens-side terminals include, for example, an attachment detection terminal that notifies the camera body 2 that the interchangeable lens 3 has been 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 that supplies power from the camera body 2 to the interchangeable lens 3, and a ground terminal, among others.

[0014] The lens-side control unit 330 is composed of a microcomputer, its peripheral circuits, and the like. The lens-side control unit 330 controls each part of the interchangeable lens 3 by executing a control program stored in the lens-side storage unit 350. The lens-side control unit 330 is connected to the lens-side communication unit 340, the lens-side storage unit 350, the lens driving unit 370a, the lens driving unit 370b, the aperture driving unit 380, and the shake sensor 390.

[0015] The lens-side communication unit 340 performs predetermined communication with a body-side communication unit 240. The lens-side communication unit 340 is connected to the lens-side control unit 330 and the communication terminal described above. Through communication between the lens-side communication unit 340 and the body-side communication unit 240, instructions for moving the imaging optical system 360 (to be described later), transmission requests for information indicating the status of a driving unit that drives the imaging optical system 360, and the like are transmitted to the interchangeable lens 3. In addition, the driving status of the imaging optical system 360 and the like are transmitted from the interchangeable lens 3 to the camera body 2 through communication performed between the lens-side communication unit 340 and the body-side communication unit 240.

[0016] The state of the drive units in the interchangeable lens 3 refers to a state in which each of the lens drive unit 370a and the lens drive unit 370b is driving the corresponding focus lens 361a and image stabilization lens 361b, or a state after driving. Meanwhile, information indicating the positions of the focus lens 361a and the image stabilization 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 configured by a non-volatile storage medium. The recording and reading of data of the lens-side storage unit 350 is controlled by the lens-side control unit 330. In addition to storing control programs and the like executed by the lens-side control unit 330, the lens-side storage unit 350 can also store data indicating the model name of the interchangeable lens 3 (also referred to as model name information), data indicating the optical characteristics of the imaging optical system 360, and the like. 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 an imaging surface 260S of an image sensor 260 of the camera body 2. An 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, an image stabilization lens 361b, and an aperture stop 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 capable of moving forward and backward in the direction of the optical axis O by the lens drive unit 370a. The movement of the focus lens 361a changes the position of the subject image formed by the imaging optical system 360, whereby an AF operation (focusing) is performed.

[0019] For example, the image stabilization lens 361b is configured to move in a direction intersecting the optical axis O by the lens drive unit 370b. By moving the image stabilization lens 361b, the shaking (image shake) of the subject image on the imaging surface 260S of the image sensor 260 is suppressed. Image stabilization by moving the image stabilization lens 361b is one of the image stabilization functions of the camera system 1.

[0020] The aperture 362 adjusts the amount of light incident on the image sensor 260. The aperture 362 is configured so that the aperture blades can be driven by the aperture drive unit 380 or by 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 in the aperture drive unit 380.

[0021] The lens drive unit 370a and the lens drive unit 370b each consist of a motor or actuator and a lens drive mechanism. The lens drive unit 370a moves the focus lens 361a along the optical axis O direction based on a drive signal output from the lens-side control unit 330. The direction, amount, and speed of movement of the focus lens 361a are instructed, for example, from the body-side control unit 230. The position of the focus lens 361a is detectable by a position detection mechanism such as an encoder in the lens drive unit 370a.

[0022] The lens drive unit 370b moves the vibration correction lens 361b in a direction intersecting the optical axis O based on a drive signal output from the lens-side control unit 330. The direction, amount, and speed of movement of the vibration correction lens 361b are, for example, instructed by the lens-side control unit 330. The position of the vibration correction lens 361b is detectable by a Hall sensor or the like in the lens drive unit 370b. The lens drive unit 370a and the lens drive unit 370b are each connected to the lens-side control unit 330.

[0023] The aperture drive unit 380 consists of a motor and an aperture drive mechanism. The aperture drive unit 380 changes the aperture diameter of the aperture 362 based on instructions from, for example, 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, which includes a gyro sensor and the like, detects shake of the camera system 1 caused by 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 Figure 1. The shake sensor 390 may also be equipped with an acceleration sensor and the like to detect shake in a direction perpendicular to the optical axis O. The detection signal from the shake sensor 390 is sent to the lens-side control unit 330. This performs so-called vibration damping control. That is, based on the detection signal from 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 oscillation (image shake) of the subject image on the imaging surface 260S of the image sensor 260.

[0025] <Camera body> The camera body 2 includes 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 image sensor 260, a sensor drive unit 265, a signal processing unit 270, an operating member 280, and a display unit 290. The sensor drive unit 265 is used in the second embodiment and may be omitted in the first embodiment.

[0026] The annular body-side mount 210 is provided with a body-side terminal holding portion 220. The body-side terminal holding portion 220 has multiple body-side terminals that contact the lens-side terminals described above. The multiple body-side terminals, like the lens-side terminals, include, for example, a mounting detection terminal that informs the camera body 2 that an interchangeable lens 3 has been attached to 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).

[0027] The body-side control unit 230 consists of a microcomputer and its peripheral circuits. The body-side control unit 230 controls each part of the camera body 2 by executing a control program stored in the memory unit 235. The body-side control unit 230 is connected to the body-side communication unit 240, power supply unit 250, shutter device 255, image sensor 260, sensor drive unit 265, signal processing unit 270, operating member 280, and display unit 290.

[0028] The body-side control unit 230 includes a storage unit 235. The storage unit 235 is controlled by the body-side control unit 230 for recording and reading data. In addition to storing control programs executed by the body-side control unit 230, the storage unit 235 can also store information such as the model name of the interchangeable lens 3 and data indicating the optical characteristics of the interchangeable lens 3, which are received by the body-side communication unit 240.

[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 multiple 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 source according to the instructions of 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 positioned in front of the image sensor and has a front curtain, a rear curtain, and an actuator mechanism to drive 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 image sensor 260. When the shutter device 255 (rear curtain) closes, light from the subject is blocked.

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

[0032] The image sensor 260 has pixels for image generation (referred to as imaging pixels) and pixels for focus detection (referred to as focus detection pixels) arranged on the imaging surface 260S. The signals generated by the imaging pixels (hereinafter referred to as imaging pixel signals) are used by the signal processing unit 270, which will be described later, to generate image data. The signals generated by the focus detection pixels (hereinafter referred to as focus detection pixel signals) are used by the signal processing unit 270, which will be described later, to detect the focus state of the image by the interchangeable lens 3. Furthermore, the image sensor 260 may be configured to include pixels that output signals usable for both imaging and focus detection.

[0033] The sensor drive unit 265 is composed of, for example, an actuator and a sensor drive mechanism. Based on instructions output from the body-side control unit 230, the sensor drive unit 265 moves the image sensor 260 in a direction intersecting the optical axis O. By moving the image sensor 260, the blur of the subject image relative to the imaging surface of the image sensor 260 (image shake) is suppressed. Shake correction by moving the image sensor 260 is one of the image stabilization functions of the camera system 1. The position of the moving image sensor 260 is configured to be detectable by a Hall sensor or the like in the sensor drive unit 265. The direction, amount, and speed of movement of the image sensor 260 are instructed, for example, by 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 image capture pixel signals output from the image sensor 260 to generate image data. The generated image data is recorded in a predetermined file format on a storage medium (memory card) (not shown), or used for displaying confirmation images of captured images or through images before shooting on the display unit 290. The signal processing unit 270 is connected to the body-side control unit 230, the image sensor 260, and the display unit 290.

[0035] Furthermore, the signal processing unit 270 uses the focus detection pixel signal output from the image sensor 260 to calculate the defocus amount, which is the difference between the position of the subject image formed by the interchangeable lens 3 and the imaging surface 260S (Figure 4) of the image sensor 260, using a phase difference detection method. Based on the calculated defocus amount and the position of the focus lens 361a at the time the focus detection pixel signal was acquired, the signal processing unit 270 calculates the amount of movement of the focus lens 361a to the focus position, which is the position of the focus lens 361a where the target subject image is in focus on the imaging surface 260S. The focus drive instruction based on the amount of movement of the focus lens 361a calculated by this focus detection calculation is transmitted from the camera body 2 to the interchangeable lens 3 along with data indicating the direction and amount of movement of the focus lens 361a.

[0036] The operating components 280, including the release button and operation switches, are provided on the exterior surface of the camera body 2. The user performs actions such as issuing shooting instructions and setting shooting conditions by operating the operating components 280. The operating components 280 send operation signals corresponding to the user's actions to the body-side control unit 230.

[0037] The display unit 290 is composed of, for example, a liquid crystal display panel. The display unit 290 displays images based on image data processed by the signal processing unit 270, operation menu screens, etc., based on instructions from the body-side control unit 230. The display unit 290 may also be equipped with a touch panel and may serve as 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] Through the aforementioned communication, the camera body 2 sends, for example, a focus drive instruction, a shake correction operation start instruction, an aperture drive instruction, a request for information transmission, and information of the camera body 2 (imaging mode information, ISO sensitivity, information on whether video recording is in progress, etc.) to the interchangeable lens 3. In accordance with instructions from the camera body 2, the interchangeable lens 3 drives the focus lens 361a, starts the shake correction operation, and drives the aperture 362.

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

[0040] FIG. 4 is a diagram explaining the configuration of the focus detection apparatus 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 image sensor 260, and a signal processing unit 270. As described above, the image sensor 260 has an imaging surface 260S on which the light flux from the imaging optical system 360 is incident. The shutter device 255 is disposed on the front surface (the imaging optical system 360 side) of the imaging surface 260S. The shutter device comprises 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 each travel from the top to the bottom in the screen of FIG. 4. FIG. 4 shows a fully open shutter state before closing, in which all shutter blades of the front curtain 255a have finished opening and moving downward, and all shutter blades of the rear curtain 255b are waiting at the upper position, showing a state where the light flux from the imaging optical system 360 is incident on the imaging surface 260S.

[0041] <Description of AF Operation> The following describes the AF operation performed during continuous shooting in this embodiment, where multiple images are captured in succession while the release button is pressed. The camera body 2 continuously captures multiple images, each a single frame, while the release button is held fully pressed. The body-side control unit 230 starts a charge accumulation operation on the image sensor 260 and drives the front curtain 255a of the shutter device 255 to open. The body-side control unit 230 then drives the rear curtain 255b of the shutter device 255 to close, and then causes the signal processing unit 270 to perform a focus detection calculation based on the focus detection pixel signal transferred from the image sensor 260 to the signal processing unit 270.

[0042] Based on the focus detection calculation result, the body-side control unit 230 instructs the lens-side control unit 330 to perform focus drive via the body-side communication unit 240 and the lens-side communication unit 340. In response to the focus drive instruction, the lens-side control unit 330 moves the focus lens 361a using the lens drive unit 370a (focus control).

[0043] Figure 5 is a schematic diagram showing 21 frames PS corresponding to the focus area P in Figure 2 superimposed on the corresponding positions on the imaging plane 260S. The position corresponding to the optical axis O of the imaging plane 260S is defined as image height y=0. The short side direction (vertical direction of the image) of the imaging plane 260S is defined as image height y=-a to +a. On the imaging plane 260S, the center position of the frame PS is in the short side direction of the imaging screen 260S, and the image height is defined as y=-b to +b. As explained using Figure 4, the front curtain 255a and rear curtain 255b of the shutter device 255 each consist of multiple shutter blades, and move from top to bottom as indicated by the arrows in Figure 5. Figure 5 shows the state where all the shutter blades of the front curtain 255a have opened downwards and finished moving, and all the shutter blades of the rear curtain 255b are waiting at the top before closing.

[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 the focus detection pixel signal used to calculate the defocus amount was acquired, up to the in-focus position. The time when the focus detection pixel signal was acquired is the exposure period (charge accumulation period) of the focus detection pixel positioned at the frame PS corresponding to the adopted focus area P, and corresponds to the time from the aperture time when the front curtain 255a of the shutter device 255 passes over the frame PS to the shading time when the rear curtain 255b passes over it.

[0045] Figure 6 is a timing chart illustrating the AF operation performed during continuous shooting. The signal processing unit 270 performs charge accumulation when the front curtain 255a of the shutter device 255 is opened for the nth frame, the (n+1)th frame, and so on. It then performs predetermined image processing on the imaging pixel signals read from the image sensor 260 after the rear curtain 255b has closed and charge accumulation has ended, and which are transferred to the signal processing unit 270, to generate one image. The signal processing unit 270 also performs focus detection calculations based on the focus detection pixel signals read from the image sensor 260 after charge accumulation has ended and which are transferred to the signal processing unit 270. The body-side control unit 230 instructs the interchangeable lens 3 to focus for each shooting frame based on the focus detection calculation results from the signal processing unit 270. For example, focus drive instructions are given between the charge accumulation periods of the image sensor 260.

[0046] In the example shown in Figure 6, the camera body 2 transmits a focus drive instruction to the interchangeable lens 3 based on the focus detection pixel signal acquired during the imaging of the previous frame, before the next frame is captured. Figure 6 shows an example in which the focus lens 361a is moved even while the image sensor 260 is accumulating charge.

[0047] The following explanation focuses on the (n+1)th frame. In Figure 6(a), the horizontal axis represents time, and the vertical axis represents the vertical position of the image sensor 260. Curve 61 shows the travel curve of the front curtain 255a in the (n+1)th frame (the last position in the travel direction of the shutter blades of the front curtain 255a). Curve 62 shows the travel curve of the rear curtain 255b in the (n+1)th frame (the leading position in the travel direction of the shutter blades of the rear curtain 255a). The body-side control unit 230 outputs a signal to the shutter device 255 to release the front curtain 255a at time t0, and outputs a signal to the shutter device 255 to release the rear curtain 255b at time t2.

[0048] The shutter device 255 has two designated design values: a first time and a second time. The first time is the time from when the signal to release the shutter curtain is input until the shutter curtain passes the position of 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 surface of the 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. Even after a signal for releasing the front curtain 255a is input and the front curtain 255a actually starts moving (the arrow in FIG. 5), in the initial stage, the rearmost end of the front curtain 255a still moves at a position higher (farther) than the image height y=+a. When the first time elapses (time t1, which will be described later), the rearmost end of the front curtain 255a reaches the position of the uppermost end (image height y=+a) of the imaging surface 260a. Thereafter, the rearmost end of the front curtain 255a moves across the imaging surface 260a within the image height range -a<y<+a, and stops after passing y=-a (moving to a position farther than y=-a). While the front curtain 255a moves across the range of -a<y<+a in image height, the light flux from the photographing optical system 360 is incident on the imaging surface 260S. That is, when the first time elapses, the uppermost portion of the imaging surface 260S is opened, and the incidence of the light flux onto the uppermost portion of the imaging surface 260S starts. As described above, the first time is the delay time from the signal for releasing the front curtain 255a to the start of incidence of the light flux onto the uppermost portion of the imaging surface 260S, and is also referred to as lag time. The second time refers to the time from when the front curtain passes the position of image height y=+a to when it passes the position of image height y=-a (time t4, which will be described later). In other words, the second time is the time taken for the rearmost end of the front curtain 255a to pass the entire surface of the imaging surface 260S, and is also referred to as curtain travel time. Before the shutter release, the foremost end of the rear curtain 255b is located at a position higher (farther) than the image height y=+a. Even after a signal for releasing the rear curtain 255b is input and the rear curtain 255b actually starts moving, the foremost end of the rear curtain 255b still moves at a position higher (farther) than the image height y=+a until the first time elapses. When the first time elapses, the foremost end of the rear curtain 255b reaches the position of the uppermost end (image height y=+a) of the imaging surface 260a. Thereafter, the foremost end of the rear curtain 255b moves across the imaging surface 260a within the image height range -a<y<+a, and stops after passing y=-a (moving to a position farther than y=-a). The foremost end of the rear curtain 255b also passes from the position of image height y=+a to the position of image height y=-a during the second time. In this embodiment, the first and second hours for the front curtain 255a are referred to as the first and second hours of the front curtain, respectively. Similarly, the first and second hours for the rear curtain 255b are referred to as the first and second hours of the rear curtain, respectively. In this embodiment, the first hour of the front curtain and the first hour of the rear curtain are approximately equal, and the second hour of the front curtain and the second hour of the rear curtain are approximately equal.

[0049] As described above, at time t1, when the first duration of the front curtain 255a has elapsed from time t0, the rear end of the front curtain 255a passes the position of image height y = +a. As a result, the front curtain 255a begins to open, and the top of the imaging surface 260S opens (light begins to enter the image sensor 260). The rear end of the front curtain 255a passes the position of image height y = +b (Figure 5, position of frame PS51) at time tb1, passes the position of image height y = 0 (Figure 5, position of frame PS52) at time t3, passes the position of image height y = -b (Figure 5, position of frame PS53) at time tb3, and passes the position of image height y = -a at time t4. The period from time t1 to time t4 is the second duration of the front curtain.

[0050] The leading edge of the rear curtain 255b passes the position of image height y = +a at time t4, after the first rear curtain time has elapsed from time t2. This causes the rear curtain 255b to begin closing (starting to block light from the image sensor 260). The rear curtain 255b passes the position of image height y = +b (Figure 5, position of frame PS51) at time tb2, passes the position of image height y = 0 (Figure 5, position of frame PS52) at time t5, passes the position of image height y = -b (Figure 5, position of frame PS53) at time tb4, and passes the position of image height y = -a at time t6. The period from time t4 to time t6 is the second rear curtain time.

[0051] <Calculation of exposure timing based on image height> As illustrated in Figure 5, in this embodiment, the front curtain 255a and rear curtain 255b of the shutter device 255 move in the negative direction of the Y axis (arrow direction). Therefore, frames PS51, PS52, and PS53, which are located at positions with different image heights in the Y axis direction on the imaging surface 260S, have different exposure timings for the focus detection pixels because the rearmost edge of the front curtain 255a and the leading edge of the rear curtain 255b pass through them at different times, respectively.

[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. Figure 6(b) shows the position information of the focus lens 361a with a circle (○). The position information of the focus lens 361a is transmitted from the lens-side control unit 330 to the body-side control unit 230 by communication between the interchangeable lens 3 and the camera body 2, which takes place at predetermined intervals.

[0053] The body-side control unit 230 calculates the position of the focus lens 361a at the time 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 position of the focus lens 361a to the signal processing unit 270. With this configuration, the signal processing unit 270 can appropriately calculate the amount of movement of the focus lens 361a from the position of the focus lens 361a at the time the focus detection pixel signal is acquired to the in-focus position.

[0054] If the focus lens 361a moves during the accumulation period of the image sensor 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 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. By configuring it in this way, the signal processing unit 270 can appropriately calculate the amount of movement of the focus lens 361a to the focus position, starting from the average position of the focus lens 361a at the time when the focus detection pixel signal is acquired while the focus lens 361a is moving.

[0055] <Calculation of exposure timing according to shutter travel characteristics> Generally, a focal-plane shutter that constitutes a shutter device 255 is biased by a spring or the like. Therefore, the traveling speed of the rearmost end of the front curtain 255a and the leading end of the rear curtain 255b is not constant within the aforementioned second front curtain time and second rear curtain time. For example, in the first half of the second front curtain time and the second rear curtain time (from image height y=+a to y=+b), the released front curtain 255a and rear curtain 255b gradually accelerate from a low speed state. In contrast, in the second half of the second front curtain time and the second rear curtain time, the traveling speed of the front curtain 255a and the rear curtain 255b has reached the designed speed, so the curtains 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 leading end of the rear curtain 255b, and is a diagram illustrating an example of 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. An actual traveling curve 71 of the leading end of the rear curtain 255b is shown by a solid line, and an 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 (from y=+a to y=-a), or two approximate straight lines 72 may be obtained separately for y>0 and y<0. Alternatively, the straight line 72 may be divided into two, for example, y>+b and +b<y, with a boundary at a position where the speed change of the rear curtain 255b changes greatly, or may further be divided into three parts: y>+b, +b<y<-b, and -b<y. As shown in FIG. 6(a), the leading end of the rear curtain 255b released at time t2 passes image height y=+a at time t4, passes image height y=+b at time tb2, and passes image height y=0 at time t5. Further, it passes image height y=-b at time tb4, and passes image height y=-a at time t6.

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

[0058] In this embodiment, the body-side control unit 230 calculates the exposure timing of the focus detection pixels of the frame PS corresponding to the adopted focus area P, in accordance with the travel characteristics of the shutter device 255. Specifically, the body-side control unit 230 approximates the travel curve 71 as a straight line, assuming that there is a linear relationship between the curtain travel time and the travel distance. When approximating the travel curve 71 as described above, two approximate straight lines 72 are calculated by dividing it into regions y>0 and y<0. The exposure timing for each frame PS is calculated using the calculated approximate straight line 72. The time it takes to pass through each frame PS is calculated using the approximate straight line 72, which is proportional to the image height, calculated for y>0 and y<0 respectively, and the exposure timing is calculated. Alternatively, the exposure timing may be calculated using the travel curve 71 instead of the approximate straight line 72, or the difference between the actual travel curve 71 and the approximate straight line 72 may be corrected for the approximate straight line 72. Figure 7(b) illustrates the relationship between the image height y on the imaging plane 260S and the amount of correction when correcting the difference. This configuration allows for simple and accurate calculation of the exposure timing.

[0059] Referring to Figures 5-7, the calculation of the exposure timing for frames PS51, PS52, and PS53 will be explained. The memory unit 235 of the body-side control unit 230 stores data showing the approximate straight line 72 in Figure 7(a). Based on this approximate straight line 72, the time when the leading edge of the rear curtain 255b passes is calculated. For example, in frame PS52 in Figure 5, the exposure timing is calculated as t5 from the approximate straight line 72 in Figure 7, which is the time when the leading edge of the rear curtain 255b passes y=0. Alternatively, the calculation may be performed using the running curve 71. The memory unit 235 of the body-side control unit 230 stores data showing the running curve 71 in Figure 7(a). The running curve 71 is obtained, for example, by measuring the running curve of the rear curtain 255b during manufacturing and storing it in the memory unit 235. Instead of storing the running curve 71, the approximation curve 72 and the correction amount in Figure 7(b) may be stored. In that case, the running curve 71 in Figure 7(a) can be calculated by correcting the approximation straight line 72 with the correction amount in Figure 7(b). The correction amount in Figure 7(b) may be determined in advance by actually measuring the curtain running 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 edge of the rear curtain 255b passes, based on the running curve 71, starting from the time t2 when the shutter device 255 outputs a signal to release the rear curtain 255b. In this embodiment, the exposure timing was determined from the leading edge travel curve 71 or approximate straight line 72 of the rear curtain 255b, but the last edge of the front curtain 255a may also be used. Alternatively, the timing at which the leading edge of the front curtain 255a passes through each frame PS and the timing at which the leading edge of the rear curtain 255b passes through each frame PS may be calculated, and the exposure timing may be calculated as the timing in the middle of these two.

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

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

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

[0063] To summarize the above explanation, the following can be said: As the front curtain 255a and rear curtain 255b of the shutter device 255 move in the Y-axis direction, frames PS51, PS52, and PS53, which are located at positions with different image heights in the Y-axis direction on the imaging plane 260S, will have different times at which the rearmost edge of the front curtain 255a and the leading edge of the rear curtain 255b pass through, respectively. As a result, the exposure timing of the focus detection pixels in frames PS51, PS52, and PS53 will be different.

[0064] If the exposure timing of the focus detection pixels in frames PS51, PS52, and PS53 is different, then when the focus lens 361a is moving, the average position of the focus lens 361a at the time the focus detection pixel signal is acquired will be different in each of frames PS51, PS52, and PS53.

[0065] However, the body-side control unit 230 calculates the exposure timing of the focus detection pixels in the corresponding frames PS51, PS52, and 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 Figure 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 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. With this configuration, 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 time the focus detection pixel signal is acquired to the in-focus position.

[0066] <Changes based on pupil position> The lengths of the first and second rear curtain durations are corrected by the pupil position of the imaging optical system 360. In this embodiment, the distance from the exit pupil position of the imaging optical system 360 to the imaging surface 260S is called the pupil distance. Figure 8 is a schematic diagram showing the pupil distance and the light rays incident on the imaging surface 260S. Figures 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, light passing through the imaging optical system 360 is incident almost perpendicularly to the central part of the imaging plane 260S near the optical axis O, whereas the higher the image height on the imaging plane 260S, the more obliquely the light passing through the imaging optical system 360 is incident. The angle at which the light passing through the imaging optical system 360 is incident at an oblique angle increases as the interpupillary distance decreases.

[0068] The shutter curtains 255a and 255b travel closer to the imaging optical system 360 than to the imaging surface 260S. Therefore, as is clearly seen in Figure 8(b), when light rays are incident at an oblique angle at 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 to the imaging surface 260S, block the light rays differs from the image height h2 of the light rays that actually enter the imaging surface 260S. The difference between the image height h1 and the image height h2 increases as the interpupillary distance decreases. The difference g2 between image height h1 and image height h2 in Figure 8(b) is greater than the difference g1 between image height h1 and image height h2 in Figure 8(a), and the difference g1 between image height h1 and image height h2 in Figure 8(a) is greater than the difference g3 between image height h1 and image height h2 in Figure 8(c).

[0069] The lens-side control unit 330 changes the first and second rear curtain exposure times for the rear curtain 255b according to the pupil distance. Specifically, the shorter the pupil distance of the imaging optical system 360, the longer the first rear curtain exposure time is corrected, and the shorter the end time of the second rear curtain exposure time is corrected. With this configuration, the exposure timing of the focus detection pixels can be appropriately determined, taking into account the difference in exposure time (charge accumulation time) caused by the difference between the image height h1 where the shutter curtains 255a and 255b exist and the image height h2 of the light rays actually incident on the imaging surface 260S, depending on the pupil distance of the imaging optical system 360.

[0070] Furthermore, by taking into account the difference in exposure time (charge accumulation time) caused by the difference between the image height h1 where the shutter curtain exists and the image height h2 of the light rays actually incident on the imaging surface 260S, and by appropriately determining the exposure timing of the focus detection pixels, the signal processing unit 270 can appropriately calculate the amount of movement of the focus lens 361a to the 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 as table values ​​in the storage unit 235. Figure 9 is a diagram illustrating table values. The table in Figure 9 stores the values ​​for the first time (51), second time (51), first time (52), second time (52), first time (53), and second time (53) of frames PS51, PS52, and PS53 at positions with different image heights in the Y-axis direction on the imaging plane 260S, respectively, for interchangeable lens A corresponding to the pupil position in Figure 8(a), interchangeable lens B corresponding to the pupil position in Figure 8(b), and interchangeable lens C corresponding to the pupil position in Figure 8(c).

[0072] In this embodiment, the first time for the front curtain and the first time for the rear curtain are approximately equal, and the second time for the front curtain and the second time for the rear curtain are approximately equal, so only one table is needed. If the running performance of the front curtain 255a and the rear curtain 255b are different, or if the first time for the front curtain and the first time for the rear curtain are different, or if the second time for the front curtain and the second time for the rear curtain are different, then a table should be prepared to correspond to each case. If there are four or more types of interchangeable lenses 3, simply add the values ​​for the additional interchangeable lenses to the table in Figure 9. Also, if you want to add focus areas other than frames PS51, PS52, and PS53 at positions with different image heights in the Y-axis direction on the imaging plane 260S, simply add the values ​​for the added positions to the table in Figure 9.

[0073] According to the first embodiment described above, the following effects and advantages can be obtained. (1) In this embodiment, during continuous shooting, the focus lens is driven for the next image based on the position of the focus lens accumulating charge in the focus detection pixel and the calculated defocus amount, thereby increasing the focusing speed of the focus lens. Furthermore, since imaging is performed even while the focusing lens is moving, the imaging speed can be increased. Continuous shooting speed can also be increased. Even if the shutter's rear curtain travel speed is not constant and has nonlinear characteristics, the exposure timing of the focus detection pixels can be appropriately determined based on the time of light blocking by the rear curtain. Determining the appropriate exposure timing of the focus detection pixels leads to correctly determining the position of the focus lens, which is the basis for calculating the amount of drive of the focus lens.

[0074] (2) Based on the light-shielding time by the rear curtain based on the travel curve of the shutter device, the exposure timing of the focus detection pixels can be appropriately determined.

[0075] (3) Determine the light-shielding timing (aperture time) corresponding to the position of the frame corresponding to the focus area (focused area) within the image sensor. With this configuration, even if the time at which the rear curtain passes through frames at multiple positions with different image heights in the direction of the rear curtain's travel (Y-axis direction) on the imaging surface differs, the exposure timing of the focus detection pixels can be appropriately determined at each position.

[0076] (4) The light-shielding timing is determined using information on the exit pupil distance of the imaging optical system. With this configuration, the exposure timing of the focus detection pixels can be appropriately determined by taking into account the difference in exposure time (charge accumulation time) caused by the difference in the image height at which 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.

[0077] (5) The shutter has a front curtain that starts the exposure of the image sensor and a rear curtain that blocks light. With this configuration, the exposure timing of the focus detection pixels can be appropriately determined based on the exposure start time by the front curtain and the light blocking time by the rear curtain.

[0078] (Second embodiment) In the second embodiment, the sensor drive unit 265 of the camera body 2 is used to move the image sensor 260 in a direction intersecting the optical axis O to correct for shake. The main components of the camera system 1 according to the second embodiment are the same as in Figure 3. The body-side control unit 230 corrects the lengths of the first and second rear curtain hours, as described in the first embodiment, based on the amount of movement (position) of the image sensor 260 in the direction intersecting the optical axis O. A detailed explanation follows below.

[0079] Figure 10 is a diagram illustrating the configuration of a focus detection device according to the second embodiment of the configuration illustrated in Figure 3. Figure 10 shows a lens-side control unit 330, a lens-side communication unit 340, a focus lens 361a, a lens drive unit 370a, a shake correction lens 361b, a lens drive unit 370b, a shake sensor 390, a body-side control unit 230, a body-side communication unit 240, a shutter device 255, an image sensor 260, a sensor drive unit 265, and a signal processing unit 270.

[0080] <Explanation of image stabilization operation> The vibration sensor 390 is composed of, 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 motion of the camera system 1. The angular velocity sensor 390a detects rotation around each axis, 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 called a gyro sensor.

[0081] Furthermore, the acceleration sensor 390b detects the acceleration generated by the translational motion of the camera system 1. The acceleration sensor 390b detects acceleration in the axis parallel to the X-axis and the axis parallel to the Y-axis, respectively, and sends the detection signal to the lens-side control unit 330. The acceleration sensor 390b is also called a G-sensor. The shake sensor 390 may be placed inside the camera body 2. Both the angular velocity sensor 390a and the acceleration sensor 390d may be placed inside the camera body 2, or one of them may be placed inside the camera body 2 and the other inside the interchangeable lens 3.

[0082] The camera system 1 is configured to enable both image stabilization by driving the image stabilization lens 361b with the lens drive unit 370b and image stabilization by driving the image sensor 260 with the sensor drive unit 265. For example, image stabilization is performed by driving the image stabilization lens 361b based on the detection signal from the image stabilization sensor 390, and then the image sensor 260 is driven to correct any remaining (residual) shake after correction by the image stabilization lens 361b.

[0083] Generally, the vibrations generated in the camera system 1 can be divided into angular vibrations associated with the rotational movement of the camera system 1 and translational vibrations associated with the translational movement of the camera system 1. The lens-side control unit 330 calculates the angular vibration and translational vibration, respectively, based on the detection signals from the vibration sensor 390. The lens-side control unit 330 calculates the angular runout in the Y-axis direction due to rotational motion using, for example, the detection signal from the angular velocity sensor 390a around an axis parallel to the X-axis (Pitch direction). The lens-side control unit 330 also calculates the angular runout in the X-axis direction due to rotational motion using the detection signal from the angular velocity sensor 390a around an axis parallel to the Y-axis (Yaw direction).

[0084] Furthermore, the lens-side control unit 330 uses the X-axis detection signal from the acceleration sensor 390b to calculate the translational wobble in the X-axis direction due to translational motion. In addition, the lens-side control unit 330 uses the Y-axis detection signal from the acceleration sensor 390b to calculate the translational wobble in the Y-axis direction due to translational motion.

[0085] The lens-side control unit 330 then adds up the angular runout in the X-axis and Y-axis directions and the translational runout in the X-axis and Y-axis directions for each X-axis and Y-axis to calculate the total runout in the X-axis and Y-axis directions. For example, if the angular runout and translational runout calculated for a certain axis direction are in the same direction, the summation will increase the total runout. However, if the directions of the two calculated runouts are different (they have components in opposite directions), the summation will decrease the total runout. In this way, the summation calculation is performed by assigning positive or negative signs to the angular runout and translational runout of each axis depending on their direction.

[0086] The lens-side control unit 330 further calculates the total image plane runout, converted to the position on the imaging plane 260S of the image sensor 260, for the X-axis and Y-axis directions, respectively, based on the summed total runout amounts in the X-axis and Y-axis directions.

[0087] The lens-side control unit 330 calculates, for example, the target position of the shake correction lens 361b in the X-axis and Y-axis directions, respectively, to move the shake correction lens 361b in a direction that cancels out a predetermined share of the calculated total shake amount of the imaging plane. The share ratio is the ratio of the shake correction amount performed by the interchangeable lens 3 to the shake correction amount performed by the camera body 2.

[0088] The lens-side control unit 330, having calculated the target position of the vibration correction lens 361b, outputs a drive signal to the lens drive unit 370b to drive the vibration correction lens 361b. Upon receiving the drive signal, the lens drive unit 370b moves the vibration correction lens 361b in the X-axis and Y-axis directions, which intersect with the optical axis O, to the target position in the X-axis direction and the target position in the Y-axis direction, respectively.

[0089] Meanwhile, the body-side control unit 230 calculates, for both the X-axis and Y-axis directions, the target position of the image sensor 260 in a direction that cancels out the amount of vibration of the above-mentioned distribution ratio from the total amount of vibration of the imaging surface received by the body-side communication unit 240 via communication.

[0090] The body-side control unit 230, having calculated the target position of the image sensor 260, outputs a drive signal to the sensor drive unit 265, which drives the image sensor 260. Upon receiving the drive signal, the sensor drive unit 265 moves the image sensor 260 to the target position in the X-axis direction and the target position in the Y-axis direction, respectively, in the X-axis and Y-axis directions that intersect the optical axis O. In the above description, the sum of angular and translational shake was divided 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 could be corrected by the interchangeable lens 3 (lens-side control unit 330) and the translational shake could be corrected by the camera body 2 (body-side control unit 230).

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

[0092] For example, if the direction in which the rear curtain 255b travels is the same as the direction in which the image sensor 260 moves for shake correction (i.e., the image sensor 260 moves in the negative direction of the Y-axis), the travel speed of the rear curtain 255b relative to the image sensor 260 decreases relatively. 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 travel speed of the rear curtain 255b relative to the image sensor 260 decreases. With this configuration, when the sensor drive unit 265 that performs shake correction moves the image sensor 260 in the same direction as the travel direction of the rear curtain 255b, the body-side control unit 230 can appropriately determine the exposure timing of the focus detection pixels, taking into account the decrease in the travel speed of the rear curtain 255b relative to the image sensor 260.

[0093] Furthermore, by appropriately determining the exposure timing of the focus detection pixels, taking into account the decrease in the travel speed of the rear curtain 255b relative to the image sensor 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 to the focus position, starting from the average position of the focus lens 361a during the exposure time (charge accumulation time) in which the focus detection pixel signal was acquired.

[0094] Unlike the above, when the direction in which the rear curtain 255b travels and the direction in which the image sensor 260 moves for shake correction are opposite (when the image sensor 260 moves in the positive direction of the Y axis), the relative travel speed of the rear curtain 255b to the image sensor 260 increases. In this case, the body-side control unit 230 corrects both the first rear curtain time and the second rear curtain time to be shorter as the travel speed of the rear curtain 255b to the image sensor 260 increases. With this configuration, when the sensor drive unit 265 that performs shake correction moves the image sensor 260 in the opposite direction to the travel direction of the rear curtain 255b, the body-side control unit 230 can appropriately determine the exposure timing of the focus detection pixels, taking into account the increase in the travel speed of the rear curtain 255b to the image sensor 260.

[0095] Furthermore, by appropriately determining the exposure timing of the focus detection pixels, taking into account the increase in the travel speed of the rear curtain 255b relative to the image sensor 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 to the focus position, starting from the average position of the focus lens 361a during the exposure time (charge accumulation time) in which the focus detection pixel signal was acquired. In the second embodiment described above, an example was shown in which shake correction is performed by driving the shake correction lens 361b with the lens drive unit 370b and by driving the image sensor 260 with the sensor drive unit 265. However, shake correction may be performed only by driving the image sensor 260. In other words, the interchangeable lens 3 may not have a shake correction lens 361b, and shake correction may be performed by driving the image sensor 260 with the sensor drive unit 265 as instructed by the body-side control unit 230.

[0096] The focus detection device according to the second embodiment described above provides the same effects as the first embodiment, as well as the following effects. Specifically, the focus detection device includes a sensor drive unit 265 that drives the image sensor 260 and a sensor drive unit 265 that detects the position of the image sensor 260, and the body-side control unit 230 determines the light-shielding time using the position detected by the sensor drive unit 265. With this configuration, even if the relative travel speed of the rear curtain 255b of the shutter device 255 changes relative to the image sensor 260, the body-side control unit 230 can appropriately determine the light-shielding time of the focus detection pixels by taking into account the change in the relative travel speed of the rear curtain 255b. As a result, 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 over the actual charge accumulation time to the focus position.

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

[0098] In the case of Modification 1, the time at which the charge accumulation operation is initiated by electronic shutter control for the focus detection pixel positioned at the frame PS corresponding to the adopted focus area P corresponds to the accumulation start time calculated in the embodiment described above. In other words, when calculating the exposure timing of frame PS51, time tb1 is calculated by counting back the accumulation time from time tb2, which is the end time of accumulation at the position of frame PS51, and this is used as the start time of accumulation. Furthermore, when calculating the exposure timing for frame PS52, time t3 is calculated by counting back the accumulation time from time t5, which is the end time of accumulation at the position of frame PS52, and this is used as the start time of accumulation. Furthermore, when calculating the exposure timing for frame PS53, time tb3 is calculated by counting back the accumulation time from time tb4, which is the accumulation end time at the position of frame PS53, and this is used as the accumulation start time.

[0099] (Modification 2) When shooting in continuous mode in 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 multiple frames. Figure 11 is a timing chart illustrating the AF operation performed during continuous shooting. Compared to the timing chart in Figure 6, it is the same as in Figure 6 except for the position of the focus lens. The body-side control unit 230 instructs the interchangeable lens 3 to focus for each frame based on the focus detection calculation result calculated by the signal processing unit 270 for each frame.

[0100] The body-side control unit 230 predicts the amount of movement of the focus lens 361a to the in-focus position based on the rate of increase in the defocus amount over multiple past frames, for example, when the amount of defocus calculated based on the focus detection pixel signal acquired when the previous frame was captured is increasing for n-1 frames, n frames, and n+1 frames. When calculating the target position of the focus lens 361a based on the focus detection pixel signal acquired when the n+1th frame was captured, the target position is normally set to Q1, but in the modified example 2, the target position is set to Q2, taking into account the rate of increase in the defocus amount. With this configuration, when shooting a fast-moving main subject in continuous shooting mode, it is possible to maintain focus on the main subject. In addition, when shooting a scene in which the moving main subject is moving away from the camera system 1 in continuous shooting mode, the body-side control unit 230 may predict the position of the focus lens 361 based on the calculation results of the defocus amount over multiple frames, similar to the above.

[0101] As shown in Modification 2, when calculating the amount of movement of the focus lens 361a while predicting changes in the amount of defocus, it is difficult to maintain focus if the average position of the focus lens 361a during the accumulation period is incorrect. However, since the body-side control unit 230 calculates the average position based on the exposure timing calculated according to the above embodiment and the position information of the focus lens 361a transmitted from the lens-side control unit 330, it can correctly determine the average position of the focus lens 361a during the accumulation period, making it suitable even when calculating the amount of movement of the focus lens 361a while predicting changes in the amount of defocus.

[0102] According to Modification 2, the following effects can be obtained. That is, since the position of the focus lens is predicted based on multiple calculation results, for example, when taking continuous shots of a fast-moving main subject, it is possible to keep the main subject in focus.

[0103] (Variation 3) In the above-described embodiment, the case in which position information of the focus lens 361a can be obtained while the image sensor 260 is accumulating charge was explained as an example. If position information of the focus lens 361a cannot be obtained while the focus lens 361a is accumulating charge, the amount of movement of the focus lens 361a to the focus position may be calculated starting from the most recent position information obtained before charge accumulation, or the most recent position information obtained after charge accumulation. Alternatively, the weighted average of the most recent position information acquired before and after charge accumulation may be taken, and the amount of movement of the focus lens 361a to the focus position may be calculated using the weighted average position information as the starting point.

[0104] (Modification 4) In the embodiment described above, an example was explained in which a pixel signal for focus detection is acquired (charge is accumulated) while the focus lens 361a is moving. However, the focusing lens 361a may be kept stationary without moving during charge accumulation.

[0105] The present invention is not limited to what has been described above. Other embodiments that can be conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of Symbols]

[0106] 1...Camera system, 2...Camera body, 3...Interchangeable lens, 230...Body-side control unit, 235...Memory 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 memory unit, 360...Imaging optical system, 370...Lens drive unit, P...Focus area

Claims

[Claim 1] An imaging unit has multiple pixels that convert light passing through an optical system including a focusing lens into photoelectric charge to accumulate charge and output a signal used for focus detection, and captures an image of a subject formed by the light beam passing through the optical system, A defocus calculation unit 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 aforementioned signal. A timing calculation unit calculates the charge accumulation timing at which the pixel corresponding to the at least one focus area accumulates charge, based on the positional information of at least one focus area selected from among multiple focus areas. An acquisition unit that acquires position information of the aforementioned focus lens, A calculation unit calculates the amount of drive 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 amount of defocus calculated by the defocus calculation unit, A focus detection device having the following features.

Images