Controller, lens device, imaging device, method for control, and program

Abstract

To provide a controller which can suppress reduction of the responsivity or the focus accuracy of a focus lens in a control which repeatedly performs imaging while moving a focus lens.SOLUTION: The controller is used for a camera system having an imaging device and a lens device removably attached to the imaging device. The controller includes: an acquisition unit for acquiring focus information from at least one of the imaging device and the lens device; and a control unit for controlling movement of a first focus lens and an optical element which move along the direction of an optical axis dependently from each other according to the focus information. The control unit performs a first drive of driving the optical element to reduce an image surface movement amount according to movement of the first focus lens when the first fucus lens and the optical element are moved at one time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device that controls the movement of a focus lens.

Background Art

[0002] Patent Document 1 discloses a configuration that realizes high-precision focusing by moving a second focus lens with high resolution so as to cancel out the defocus amount generated by a first focus lens with low resolution without generating aberration.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the continuous shooting speed of imaging devices has become very high, and control is performed to repeat imaging while moving a focus lens. However, the configuration of Patent Document 1 does not consider control to repeat imaging while moving the focus lens. For example, when the image plane movement speed is lower than the minimum driving speed of the actuator that moves the focus lens, it is necessary to execute intermittent control that repeats driving and stopping, and there are cases where the responsiveness and focusing accuracy of the focus lens deteriorate.

[0005] An object of the present invention is to provide a control device capable of suppressing a decrease in the responsiveness and focusing accuracy of a focus lens even in control for repeating imaging while moving the focus lens.

Means for Solving the Problems

[0006] One aspect of the present invention is a control device used in a camera system comprising an imaging device and a lens device detachable from the imaging device, comprising: an acquisition unit that acquires focus information from at least one of the imaging device and the lens device; and a control unit that controls the movement of a first focus lens and an optical element, which are movable independently in the optical axis direction, according to the focus information, wherein the control unit performs a first drive to move the optical element in such a way that the amount of image plane movement corresponding to the movement of the first focus lens is reduced when the first focus lens and the optical element are moved simultaneously.

[0007] Furthermore, another aspect of the present invention is a control method used in a camera system comprising an imaging device and a lens device detachable from the imaging device, comprising: a first step of acquiring focus information from at least one of the imaging device and the lens device; and a second step of controlling the movement of a first focus lens and an optical element, which are movable independently in the optical axis direction, according to the focus information, wherein in the second step, when the first focus lens and the optical element are moved simultaneously, the optical element is moved in such a way that the amount of image plane movement corresponding to the movement of the first focus lens is reduced. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a control device that can suppress a decrease in the responsiveness of the focus lens and the focusing accuracy even when controlling repeated imaging while moving the focus lens. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram of the camera system of Example 1. [Figure 2] This diagram shows the relationship between the subject distance and the focusing lens or floating lens. [Figure 3] This figure shows the relationship between the lens position and the image plane position in the normal control mode of Example 1. [Figure 4]This figure shows the relationship between the lens position and the image plane position in the low-speed control mode of Example 1. [Figure 5] This is a flowchart showing the control method for the focus lens and floating lens in Example 1. [Figure 6] This is a block diagram of the camera system of Example 1. [Figure 7] This figure shows the relationship between the element position and the image plane position in the normal control mode of Example 2. [Figure 8] This figure shows the relationship between the element position and the image plane position in the low-speed control mode of Example 2. [Figure 9] This is a flowchart showing the control method for the focus lens and image sensor in Example 2. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numeral is used for identical components, and redundant explanations are omitted. [Examples]

[0011] Figure 1(a) is a block diagram of the camera system of this embodiment. The camera system includes an interchangeable lens 100 and a camera body (imaging device) 200. The interchangeable lens 100 is configured to be detachably attached to the camera body 200 and is mechanically and electrically connected to the camera body 200 via a mount (not shown). The interchangeable lens 100 receives power from the camera body 200 via a power terminal (not shown) provided on the mount. The interchangeable lens 100 uses the power supplied from the camera body 200 to control various actuators (driving means) and a lens microcomputer (hereinafter referred to as lens microcontroller) 113, which will be described later. The camera body 200 communicates with the interchangeable lens 100 via a communication terminal (not shown) provided on the mount and controls the interchangeable lens 100 by sending control commands.

[0012] The camera body 200 includes an imaging device 201, a signal processing unit 202, a recording processing unit 203, a display unit 204, an operation unit 205, and a camera microcomputer (hereinafter referred to as the camera microcontroller) 206.

[0013] The imaging device 201 photoelectrically converts the subject image formed by the imaging optical system in the interchangeable lens 100 and outputs an electrical signal (analog signal). An A / D conversion circuit (not shown) converts the analog signal from the imaging device 201 into a digital signal.

[0014] The signal processing unit 202 performs various image processes on the digital signal from the A / D conversion circuit to generate a video signal. Also, the signal processing unit 202 generates focus information indicating the contrast state of the subject image, that is, the focus state of the imaging optical system, luminance information representing the exposure state, etc. from the video signal.

[0015] The imaging device 201 can detect the focus state of the subject image by the phase difference detection method. The signal processing unit 202 processes the pair of phase difference signals of the subject images obtained based on the light incident through the microlenses for pupil division on the pixels for focus detection included in the imaging device 201, and determines the defocus amount corresponding to the phase difference signal. The signal processing unit 202 outputs the video signal to the display unit 204, and the display unit 204 displays the video signal as a live view image used for confirmation of the composition, focus state, etc. Specifically, the display unit 204 is the rear liquid crystal of the camera body 200, an electronic viewfinder, etc. Also, the signal processing unit 202 outputs the video signal to the recording processing unit 203, and the recording processing unit 203 stores the video signal as still image or moving image data in an external memory (not shown), etc.

[0016] The camera microcontroller 206 controls the camera body 200 according to inputs such as the imaging instruction switch and various setting switches included in the operation unit 205. Also, the camera microcontroller 206 transmits control commands regarding the light amount adjustment operation of the aperture unit 103 according to the luminance information and focus adjustment according to the focus information including the defocus amount to the lens microcontroller 113.

[0017] The interchangeable lens 100 includes an imaging optical system, various control units for controlling various actuators that move the elements included in the imaging optical system, a focus lens operation ring 112, and a lens microcomputer 113.

[0018] The imaging optical system includes a field lens 101, a zoom lens 102, an aperture unit 103, an image shake correction lens 104, a focus lens (first focus lens) 105, and a floating lens (second focus lens) 106.

[0019] The field lens 101 adjusts the traveling direction of peripheral light in the subject image.

[0020] The zoom lens 102 is movable in the optical axis direction of the imaging optical system shown by a dashed line in the figure, and moves in the optical axis direction when a zoom operation ring connected to a zoom mechanism (not shown) is operated by the user. When the zoom lens 102 moves, zooming is performed to change the focal length of the photographing optical system. The zoom lens position detection unit 107 detects the position of the zoom lens 102 using a position detection sensor such as a variable resistor, and outputs information regarding the position of the zoom lens 102 to the lens microcomputer 113. The output position data is used by the lens microcomputer 113 for zoom tracking control and the like.

[0021] The aperture unit 103 is configured to include sensors such as aperture blades and a hall element. The state of the aperture blades is detected by the aforementioned sensors, and information regarding the state of the aperture blades is output to the lens microcomputer 113. The aperture control unit 108 drives an actuator such as a stepping motor or a voice coil motor according to a command from the lens microcomputer 113 to adjust the light amount by the aperture unit 103.

[0022] The image shake correction lens 104 reduces image shake caused by camera shake, etc., by moving in a direction that includes a component perpendicular to the optical axis of the imaging optical system. The image shake correction lens control unit 109 performs vibration isolation by driving an anti-vibration actuator and moving the image shake correction lens 104 in response to shake detected by a vibration gyroscope, acceleration sensor, etc. (not shown), based on a command from the lens microcontroller 113.

[0023] The focus lens 105 is movable in the direction of the optical axis of the imaging optical system and can perform focus control to image the subject onto the image sensor 201. The position of the focus lens 105 is detected using a position detection sensor such as a photointerrupter or potentiometer (not shown), and information regarding the position of the focus lens 105 is output to the lens microcontroller 113. The focus lens control unit 110 adjusts the focus by driving actuators such as a stepping motor or ultrasonic motor to move the focus lens 105 based on commands from the lens microcontroller 113.

[0024] The floating lens 106 is movable in the direction of the optical axis of the imaging optical system. The position of the floating lens 106 is detected using the aforementioned position detection sensor, and information regarding the position of the floating lens 106 is output to the lens microcontroller 113. By moving the floating lens 106 together with the focus lens 105 in conjunction with the subject distance, aberrations such as spherical aberration and distortion can be minimized. In addition, the focal position changes depending on the position of the floating lens 106. By effectively controlling the floating lens 106 using this characteristic, it is possible to perform highly responsive focus adjustment.

[0025] The lens microcontroller 113 controls the operation of each part within the interchangeable lens 100. The lens microcontroller 113 receives control commands transmitted from the camera body 200 and receives requests to transmit lens data. The lens microcontroller 113 also performs lens control corresponding to the control commands and transmits lens data corresponding to the transmission requests to the camera body 200. Specifically, in response to a control command related to light intensity adjustment, the lens microcontroller 113 issues a command to the aperture control unit 108 to adjust the light intensity using the aperture unit 103. In addition, in response to a focusing command, the lens microcontroller 113 issues commands to the focus lens control unit 110 and the floating lens control unit 111 to move the focus lens 105 and the floating lens 106 to adjust the focus. Furthermore, the lens microcontroller 113 can also perform so-called manual focus adjustment by issuing a command to the focus lens control unit 110 to move the focus lens 105 according to the amount of operation of the focus lens operation ring 112. The amount of movement of the focus lens operating ring 112 is calculated by the lens microcontroller 113 using signals output from sensors such as a photo interrupter (not shown).

[0026] Furthermore, as shown in Figure 1(b), the lens microcontroller 113 comprises an acquisition unit 113a and a control unit 113b. The acquisition unit 113a acquires focus information from at least one of the camera body 200 and the interchangeable lens 100. The control unit 113b controls the movement of the focus lens 105 and optical elements, which are movable in the optical axis direction independently of each other, according to the focus information acquired by the acquisition unit 113a. The optical elements include a floating lens 106 and an image sensor configured to move in the optical axis direction. In this embodiment, the lens microcontroller 113 is mounted inside the interchangeable lens 100, but it may be configured as a separate control device from the interchangeable lens 100. Also, the camera microcontroller 206 may be configured to have the functions of both the acquisition unit 113a and the control unit 113b.

[0027] Here, we will explain the relationship between the subject distance and the positions of the focus lens 105 and the floating lens 106. Based on the information provided by the camera microcontroller 206, the lens microcontroller 113 generates the target position of the floating lens 106 so that the target position of the focus lens 105 and the target position of the floating lens 106 are at the same subject distance. In the following explanation, for simplicity, we will show the case where the interchangeable lens 100 is a fixed-focal-length lens.

[0028] Figure 2(a) shows the relationship between the subject distance and the position of the focus lens 105 (focus lens position) for maintaining focus at that subject distance. In Figure 2(a), the horizontal axis represents the subject distance and the vertical axis represents the focus lens position. Figure 2(b) shows the relationship between the subject distance and the position of the floating lens 106 (floating lens position) for maintaining focus at that subject distance. In Figure 2(b), the horizontal axis represents the subject distance and the vertical axis represents the floating lens position.

[0029] In Figure 2, when the focus lens position and floating lens position are Afo and Afl, respectively, the subject at subject distance A is in focus. When the subject distance shifts from A to B, and the focus lens position changes from Afo to Bfo, the floating lens position also changes in conjunction from Af1 to Bfl, thereby maintaining the aberration and focus state.

[0030] A memory (not shown) mounted on the lens microcontroller 113 stores electronic cam data (position characteristic data) that shows the relationship between multiple representative subject distances, the focus lens position, and the floating lens position. If the interchangeable lens 100 is a zoom lens with a changeable focal length or a variable aberration lens with a changeable aberration state, position characteristic data may be stored for each focal length and aberration state.

[0031] If the interchangeable lens 100 is a zoom lens, the focus lens 105 and floating lens 106 correct the image plane fluctuations associated with the magnification by the zoom lens 102. For example, in a rear-focus type variable magnification optical system, zoom tracking control is performed to maintain focus by correcting the image plane fluctuations that occur when magnification is performed by moving the zoom lens 102 by moving the focus lens 105 and floating lens 106. Electronic cam data is stored in a memory (not shown) mounted on the lens microcontroller 113 in order to perform zoom tracking control. Based on the electronic cam data, the lens microcontroller 113 issues control commands to the focus lens control unit 110 and the floating lens control unit 111 to move the focus lens 105 and the floating lens 106.

[0032] The electronic cam data is generated based on the focus sensitivity, which is the amount of image plane movement relative to the unit drive amount of the focus lens 105. However, the electronic cam data actually stored in memory is, for example, data corresponding to several representative subject distances and data for a representative zoom lens position (representative point). The desired focus lens position is obtained by linear interpolation based on the ratio of distances to several representative points close to the zoom lens position other than the representative point.

[0033] There are two methods for adjusting focus by moving the focus lens 105 and the floating lens 106: autofocus (hereinafter referred to as AF), which adjusts focus automatically, and manual focus (hereinafter referred to as MF), which adjusts focus manually. In AF, the camera microcontroller 206 calculates the focus position of the subject from the AF evaluation value generated by the image sensor 201 and sends a control command related to focusing to the lens microcontroller 113. In response to the control command, the lens microcontroller 113 issues commands to the focus lens control unit 110 and the floating lens control unit 111 to move the focus lens 105 and the floating lens 106 and adjust the focus. In MF, the lens microcontroller 113 issues commands to the focus lens control unit 110 according to the amount of operation of the focus lens operation ring 112 to move the focus lens 105 and adjust the focus.

[0034] However, in autofocus, the actuators that move the focus lens 105 and the floating lens 106 may not be able to be driven at the drive speed calculated by the camera microcontroller 206, depending on their performance. In particular, ultrasonic motors cannot be driven at unnecessarily low speeds considering noise and durability. In such cases, effective low-speed driving of the actuators can be achieved by reducing the average amount of drive over time through intermittent operation that repeatedly drives and stops. However, in order to implement intermittent operation, the camera microcontroller 206 needs to repeatedly issue drive commands and stop commands to the lens microcontroller 113, and furthermore, it needs to appropriately manage the imaging timing of the image sensor 201, which complicates the control.

[0035] According to the configuration of this embodiment, it is possible to reduce the movement speed of the image formed on the image sensor 201 by the imaging optical system (image plane movement speed) while maintaining the low-speed limit of the actuator without performing intermittent operation. Furthermore, it is possible to reduce the minimum amount of movement of the image formed on the image sensor 201.

[0036] Figure 3 shows the relationship between the lens position and the image plane position synchronized with the electronic cam data in the normal control mode (first control mode), where the lowest image plane movement speed is the first speed. In Figure 3, the horizontal axis represents time. In Figures 3(a) to 3(c), the vertical axes represent the focus lens position, the floating lens position, and the position of the image formed on the image sensor 201 (image plane position), respectively.

[0037] In Figure 3(a), the floating lens position Xfl0 is synchronized with the focus lens position Xfo0 at time t0, and is acquired using electronic cam data. During the interval from time t0 to t1, the focus lens position changes from Xfo0 to Xfo1, and the floating lens position also changes from Xfl0 to Xfl1.

[0038] The image plane position changes due to the movement of the focusing lens 105 and the floating lens 106. The image moves by an amount equal to the amount of movement of the focusing lens 105 multiplied by the sensitivity coefficient Sfo of the focusing lens 105. The image also moves by an amount equal to the amount of movement of the floating lens 106 multiplied by the sensitivity coefficient Sfl of the floating lens 106. The change in image plane position (image plane displacement) X due to the changes in the positions of the focusing lens and the floating lens in the interval from time t0 to t1 is expressed by the following equation (1).

[0039]

number

[0040] Furthermore, the sensitivity coefficients Sfo and Sfl change with each focus position, and their values ​​are either positive or negative. In other words, the image may move in a direction different from the direction of movement of the focus lens 105 or the floating lens 106. Moreover, if the interchangeable lens 100 is a zoom lens, it will also change depending on the zoom position.

[0041] For example, in the interval from time t0 to t1, the change in the position of the focus lens is 2, the change in the position of the floating lens is 1, the sensitivity coefficient Sfo of the focus lens 105 is 1.5, and the sensitivity coefficient Sfl of the floating lens 106 is 1. In this case, the image plane movement X is 4.

[0042] Figure 4 shows the relationship between the lens position and the image plane position in the low-speed control mode (second control mode), where the lowest image plane movement speed is the second speed, which is slower than the first speed. In Figure 4, the horizontal axis represents time. In Figures 4(a) to 4(c), the vertical axes represent the focus lens position, the floating lens position, and the image plane position, respectively.

[0043] At time t0, the focus lens position is Yfo0, and the floating lens position synchronized with the focus lens position Yfo0, acquired using electronic cam data, is Yfl0. At time t1, the focus lens position is Yfo1, and the floating lens position synchronized with the focus lens position Yfo1, acquired using electronic cam data, is Yfl1. However, in low-speed control mode, the floating lens 106 is moved along the solid line in Figure 4(b) so that the floating lens position becomes Zfl1.

[0044] In this embodiment, in the interval from time t0 to t1, the floating lens 106 is moved in a direction different from the direction toward the floating lens position synchronized with the focus lens position acquired using electronic cam data in normal control mode. That is, in the interval from time t0 to t1, the floating lens 106 moves in a direction that cancels out the change in image plane position caused by the movement of the focus lens 105. In this embodiment, in the interval from time t0 to t1, the focus lens 105 and the floating lens 106 move in opposite directions to each other. In this case, the amount of image plane movement Y shown in Figure 4(c) is smaller than the amount of image plane movement X shown in Figure 3(c). Therefore, it is possible to reduce the amount of image plane movement per unit time. Thus, when the focus lens 105 and the floating lens 106 are moved simultaneously, the drive that moves the floating lens 106 in such a way as to reduce the amount of image plane movement corresponding to the movement of the focus lens 105 is called the first drive.

[0045] For example, in the interval from time t0 to t1, let the change in the position of the focus lens be 2, the change in the position of the floating lens be -1, the sensitivity coefficient Sfo of the focus lens 105 be 1.5, and the sensitivity coefficient Sfl of the floating lens 106 be 1. In this case, the image plane shift Y is 2, which is smaller than the image plane shift X when the floating lens 106 is moved in synchronization with the movement of the focus lens 105.

[0046] At time t1, the difference between the floating lens position Yfl1 synchronized with the focus lens position Yfo1 acquired using electronic cam data and the current floating lens position Zfl1 (hereinafter referred to as the synchronization error) exceeds a first threshold. At this timing, the focus lens 105 is stopped. The first threshold is set based on at least one of the optical aberrations, the F-number of the aperture unit 103 determined by the camera body 200, and the allowable circle of confusion diameter of the image sensor 201.

[0047] During the interval from time t1 to t2, the focus lens 105 remains stationary, as shown in Figure 4(a). The floating lens 106 moves to the floating lens position Yfl1, as shown in Figure 4(b). The movement speed of the floating lens 106 is set to match the image plane movement speed during the interval from time t0 to t1. This drive, which stops the focus lens 105 and moves the floating lens 106 to minimize synchronization misalignment, is called the second drive. The direction of movement of the floating lens 106 in the second drive is opposite to the direction of movement of the floating lens 106 in the first drive.

[0048] For example, in the interval from time t1 to t2, the change in the position of the focus lens is 0, the change in the position of the floating lens is 2, the sensitivity coefficient Sfo of the focus lens 105 is 1.5, and the sensitivity coefficient Sfl of the floating lens 106 is 1. In this case, the amount of image plane movement is 2, and the image plane movement speed in the interval from time t0 to t1 and in the interval from time t1 to t2 are the same. Here, the case in which the focus lens 105 is stopped is shown, but the floating lens 106 may be controlled to eliminate the synchronization misalignment without stopping it. For example, this can be similarly achieved by slowing down the speed of the focus lens 105 compared to the speed in the interval from time t0 to t1, and moving the floating lens 106 faster in the direction that eliminates the synchronization misalignment.

[0049] At time t2, the synchronization error falls below the second threshold. At this timing, the first drive is initiated. The second threshold is ideally 0, but may be set by the stopping accuracy of the actuators that move the focus lens 105 and the floating lens 106. Alternatively, the second threshold may be set based on any of the optical aberrations, the F-number, or the allowable circle of confusion diameter of the image sensor 201.

[0050] As explained above, in the low-speed control mode, the drive in the interval from time t0 to t1 (first drive) and the drive in the interval from time t1 to t2 (second drive) are repeated. This makes it possible to make the image plane movement speed slower than when the floating lens 106 is moved in synchronization with the movement of the focus lens 105. Also, from the camera body 200, the image appears to be moving continuously rather than intermittently. Therefore, the camera body 200 does not need to manage the state of the focus lens 105 and can determine the timing of imaging, thus reducing the imaging processing load on the camera microcontroller 206. Note that the normal control mode and the low-speed control mode may be executed using the corresponding position characteristic data.

[0051] The control method for the focus lens 105 and floating lens 106 in this embodiment will be described below with reference to Figure 5. Figure 5 is a flowchart showing the control method for the focus lens 105 and floating lens 106 in this embodiment.

[0052] In step S101, the lens microcontroller 113 (acquisition unit 113a) acquires the image plane movement speed specified by the camera body 200.

[0053] In step S102, the lens microcontroller 113 (control unit 113b) determines whether the image plane movement speed acquired in step S101 is less than a threshold. If it is determined that the image plane movement speed is less than the threshold, the process proceeds to step S104; otherwise, it proceeds to step S103. Note that if the image plane movement speed is equal to the threshold, the process can be arbitrarily set to proceed to either step or the other.

[0054] In step S103, the lens microcontroller 113 (control unit 113b) is set to normal control mode and controls the movement of the focus lens 105 and the floating lens 106 in normal control mode.

[0055] In step S104, the lens microcontroller 113 (control unit 113b) is set to low-speed control mode.

[0056] In this embodiment, switching between the normal control mode and the low-speed control mode is performed using the image plane movement speed, but it may also be performed using the image plane movement amount.

[0057] In step S105, the lens microcontroller 113 (control unit 113b) obtains the movement speeds of the focus lens 105 and the floating lens 106 to achieve the image plane movement speed acquired in step S101. The movement speeds of the two lenses are obtained based on the minimum drive speed of the actuators that move the two lenses and at least one of the sensitivities of the two lenses. The sensitivity of the focus lens 105 (first sensitivity) and the sensitivity of the floating lens 106 (second sensitivity) are the amount of image plane movement for each unit movement of the lens.

[0058] In step S106, the lens microcontroller 113 (control unit 113b) performs a first drive to move the floating lens 106 in such a way that the amount of image plane movement corresponding to the movement of the focus lens 105 is reduced.

[0059] In step S107, the lens microcontroller 113 (control unit 113b) determines whether the focus lens 105 and the floating lens 106 have reached the target position. If it is determined that they have reached the target position, the process proceeds to step S112; otherwise, the process proceeds to step S108.

[0060] In step S108, the lens microcontroller 113 (control unit 113b) determines whether the synchronization misalignment is greater than or equal to a first threshold. If it is determined that the synchronization misalignment is greater than or equal to the first threshold, the process proceeds to step S109; otherwise, it returns to step S107.

[0061] In step S109, the lens microcontroller 113 (control unit 113b) stops the focus lens 105 and performs a second drive to move the floating lens 106 so as to reduce the synchronization misalignment. Here, the movement speed of the floating lens 106 is determined to achieve the image plane movement speed acquired in step S101.

[0062] In step S110, the lens microcontroller 113 (control unit 113b) determines whether the focus lens 105 and the floating lens 106 have reached the target position. If it is determined that they have reached the target position, the process proceeds to step S112; otherwise, the process proceeds to step S111.

[0063] In step S111, the lens microcontroller 113 (control unit 113b) determines whether the synchronization misalignment is greater than or equal to the second threshold. If it is determined that the synchronization misalignment is less than or equal to the second threshold, the process returns to step S106; otherwise, it returns to step S110.

[0064] In step S112, the lens microcontroller 113 terminates control of the focus lens 105 and the floating lens 106.

[0065] As described above, with the configuration of this embodiment, it is possible to reduce the image plane movement speed without changing the minimum drive speed of the actuators that drive the focus lens 105 and the floating lens 106. Therefore, it is possible to suppress a decrease in the responsiveness of the focus lens. In addition, when the target position is reached in steps S106 and S107, it is possible to make the minimum image plane movement amount smaller than in the normal control mode, thereby improving the focusing accuracy. [Examples]

[0066] Figure 6(a) is a block diagram of the camera system of this embodiment. The camera system of this embodiment differs from the camera system of Embodiment 1 in that the interchangeable lens 100 does not have a floating lens and the image sensor 201 is configured to be movable in the optical axis direction. The other configurations are the same as those of the camera system of Embodiment 1. In this embodiment, only the configurations that differ from Embodiment 1 will be described, and the common configurations will not be described.

[0067] The camera microcontroller 206 controls the movement of the image sensor 201 via the image sensor control unit 207. The camera microcontroller 206 also includes an acquisition unit 206a and a control unit 206b, as shown in Figure 6(b). The acquisition unit 206a and the control unit 206b each have the same functions as the acquisition unit 113a and the control unit 113b. In this embodiment, the camera microcontroller 206 is mounted on the camera body 200, but it may be configured as a separate control device from the camera body 200.

[0068] Figure 7 shows the relationship between the element position and the image plane position in the normal control mode (first control mode), where the lowest image plane movement speed is the first speed. In Figure 7, the horizontal axis represents time. In Figures 7(a) to 7(c), the vertical axes represent the focus lens position, the position of the image sensor 201, and the image plane position, respectively.

[0069] In normal control mode, the focus is adjusted by moving the focus lens 105 while the position of the image sensor 201 is fixed at Pi0. When the focus lens position changes from Pfo0 to Pfo1 during the interval from time t0 to t1, the image plane position changes from P0 to P1. The amount of image plane movement P due to the change in the focus lens position is expressed by the following equation (2).

[0070]

number

[0071] Note that the sensitivity coefficient Sfo changes with each focus position, and if interchangeable lens 100 is a zoom lens, it also changes with the zoom position.

[0072] For example, in the interval from time t0 to t1, let the change in the position of the focus lens be 2, the change in the position of the image sensor 201 be 0, and the sensitivity coefficient Sfo of the focus lens 105 be 1.5. In this case, the change in the position of the image plane P is 3.

[0073] Figure 8 shows the relationship between the element position and the image plane position in the low-speed control mode (second control mode), where the lowest image plane movement speed is the second speed, which is slower than the first speed. In Figure 4, the horizontal axis represents time. In Figures 8(a) to 8(c), the vertical axes represent the focus lens position, the floating lens position, and the image plane position, respectively.

[0074] At time t0, the focus lens position is Qfo0 and the position of the image sensor 201 is Qi0. In the interval from time t0 to t1, the focus lens 105 moves to the focus lens position Qfo1. The image sensor 201 also moves to position Qi1 to counteract the change in image plane position caused by the movement of the focus lens 105. In this embodiment, in the interval from time t0 to t1, the image sensor 201 moves in the opposite direction to the movement of the focus lens 105. The image plane position changes due to the movement of the focus lens 105 and the image sensor 201. The amount of image plane movement Q due to the change in the position of the focus lens and the position of the image sensor 201 is expressed by the following equation (3).

[0075]

number

[0076] The image plane movement amount Q shown in Figure 8(c) is smaller than the image plane movement amount P shown in Figure 7(c). Therefore, it is possible to reduce the amount of image plane movement per unit time. Thus, when the focus lens 105 and the image sensor 201 are moved simultaneously, the drive that moves the image sensor 201 in such a way as to reduce the amount of image plane movement corresponding to the movement of the focus lens 105 is called the first drive.

[0077] For example, in the interval from time t0 to t1, let the change in the position of the focus lens be 2, the change in the image sensor 201 be -2, and the sensitivity coefficient Sfo of the focus lens 105 be 1.5. In this case, the image plane shift Q is 1, which is smaller than the image plane shift P when the image sensor 201 is fixed and the focus lens 105 is moved.

[0078] At time t1, the image sensor 201 reaches position Qi1, which is the first end of the movable range of the image sensor 201 in the optical axis direction. At this timing, the focus lens 105 is stopped.

[0079] In the interval from time t1 to t2, the focus lens 105 remains stationary, as shown in Figure 8(a). The image sensor 201 moves to position Qi0, as shown in Figure 8(b). The movement speed of the image sensor 201 is set to match the image plane movement speed in the interval from time t0 to t1. This drive, which stops the focus lens 105 and moves the image sensor 201 to the second end of the movable range (in the opposite direction to the movement direction of the image sensor 201 in the first drive), is called the second drive. Although the case of stopping the focus lens 105 is shown here, the same can be achieved by decelerating it without stopping it and driving the image sensor 201 at a higher speed.

[0080] For example, in the interval from time t1 to t2, let's assume the change in the position of the focus lens is 0, the change in the position of the image sensor 201 is 2, and the sensitivity coefficient Sfo of the focus lens 105 is 1.5. In this case, the change in the image plane position is 2, and the image plane movement velocity in the interval from time t0 to t1 and in the interval from time t1 to t2 are the same.

[0081] At time t2, the image sensor 201 reaches position Qi0, which is the second end of its movable range. At this timing, the first drive is initiated.

[0082] As explained above, in the low-speed control mode, the drive in the interval from time t0 to t1 (first drive) and the drive in the interval from time t1 to t2 (second drive) are repeated. This makes it possible to make the image plane movement speed slower than when the image sensor 201 is fixed and the focus lens 105 is moved.

[0083] The control method for the focus lens 105 and image sensor 201 in this embodiment will be described below with reference to Figure 9. Figure 9 is a flowchart showing the control method for the focus lens 105 and image sensor 201 in this embodiment.

[0084] In step S201, the camera microcontroller 206 (acquisition unit 206a) acquires the image plane movement speed specified by the camera body 200.

[0085] In step S202, the camera microcontroller 206 (control unit 206b) determines whether the image plane movement speed acquired in step S201 is less than a threshold. If it is determined that the image plane movement speed is less than the threshold, the process proceeds to step S204; otherwise, it proceeds to step S203. Note that if the image plane movement speed is equal to the threshold, the process can be arbitrarily set to proceed to either step or the other.

[0086] In step S203, the camera microcontroller 206 (control unit 206b) is set to normal control mode and controls the movement of the focus lens 105 and the image sensor 201 in normal control mode.

[0087] In step S204, the camera microcontroller 206 (control unit 206b) is set to low-speed control mode.

[0088] In this embodiment, switching between the normal control mode and the low-speed control mode is performed using the image plane movement speed, but it may also be performed using the image plane movement amount.

[0089] In step S205, the camera microcontroller 206 (control unit 206b) obtains the movement speeds of the focus lens 105 and the image sensor 201 to achieve the image plane movement speed acquired in step S201. The movement speeds of the focus lens 105 and the image sensor 201 are obtained based on at least one of the minimum drive speed of the actuators that move the focus lens 105 and the image sensor 201, and the sensitivity of the focus lens 105. The sensitivity of the focus lens 105 is the amount of image plane movement relative to the unit movement amount of the focus lens 105.

[0090] In step S206, the camera microcontroller 206 (control unit 206b) performs a first drive to move the image sensor 201 in such a way that the amount of image plane movement corresponding to the movement of the focus lens 105 is reduced.

[0091] In step S207, the camera microcontroller 206 (control unit 206b) determines whether the focus lens 105 and the image sensor 201 have reached the target position. If it is determined that the target position has been reached, the process proceeds to step S212; otherwise, the process proceeds to step S208.

[0092] In step S208, the camera microcontroller 206 (control unit 206b) determines whether the image sensor 201 has reached the first end of the movable range. If it is determined that the first end has been reached, the process proceeds to step S209; otherwise, it returns to step S207.

[0093] In step S209, the camera microcontroller 206 (control unit 206b) stops the focus lens 105 and performs a second drive to move the image sensor 201 to the second end of its movable range. Here, the movement speed of the image sensor 201 is determined to achieve the image plane movement speed acquired in step S201.

[0094] In step S210, the camera microcontroller 206 (control unit 206b) determines whether the focus lens 105 and the image sensor 201 have reached the target position. If it is determined that the target position has been reached, the process proceeds to step S212; otherwise, the process proceeds to step S211.

[0095] In step S211, the camera microcontroller 206 (control unit 206b) determines whether the image sensor 201 has reached the second end of the movable range. If it is determined that the second end has been reached, the process returns to step S206; otherwise, the process returns to step S210.

[0096] In step S212, the camera microcontroller 206 terminates control of the focus lens 105 and the image sensor 201.

[0097] As described above, with the configuration of this embodiment, it is possible to reduce the image plane movement speed without changing the minimum drive speed of the actuator that drives the focus lens 105 and the image sensor 201. Therefore, it is possible to suppress a decrease in the responsiveness of the focus lens. In addition, when the target position is reached in the processing of steps S206 and S207, it is possible to make the minimum amount of image plane movement smaller than in the normal control mode, and thus it is possible to improve the focusing accuracy. [Other examples] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0098] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. [Explanation of symbols]

[0099] 100 interchangeable lenses (lens assembly) 105 Focusing lens (first focusing lens) 106 Floating lens (optical element, second focusing lens) 113 Lens Microcomputer (Control Device) 113a Acquisition Department 113b Control Unit 200 Camera body (imaging device) 206 Camera Microcomputer (Control Unit) 206a Acquisition Department 206b Control Unit 201 Image sensor (optical element)

Claims

1. A control device for use in a camera system including an imaging device and a lens device detachable from the imaging device, an acquisition unit that acquires focus information from at least one of the imaging device and the lens device; a control unit that controls movement of a first optical element and a second optical element that are movable in an optical axis direction independently of each other in accordance with the focus information; The control device is characterized in that, when the first optical element and the second optical element are moved simultaneously, the control unit performs a first drive to move the second optical element so as to reduce the amount of image plane movement corresponding to the movement of the first optical element.

2. The control device according to claim 1 , wherein the control unit moves the first optical element and the second optical element in opposite directions to each other in the first driving.

3. 3. The control device according to claim 1, wherein each of the first and second optical elements is a lens included in the lens device.

4. The control device according to claim 3, characterized in that when performing the first drive, if a difference between a position of the second optical element corresponding to a position of the first optical element based on position characteristic data indicating a relationship between a subject distance and the positions of the first optical element and the second optical element and a current position of the second optical element is equal to or greater than a first threshold value, the control unit performs a second drive to stop or decelerate the first optical element and move the second optical element so as to reduce the difference.

5. 5. The control device according to claim 4, wherein the first threshold value is set based on at least one of optical aberrations, an F-number, and a permissible circle of confusion diameter of an image pickup element provided in the image pickup device.

6. 6. The control device according to claim 4, wherein the control unit performs the first driving when the difference is equal to or smaller than a second threshold value while the second driving is being performed.

7. 7. The control device according to claim 6, wherein the second threshold value is set based on at least one of a stopping accuracy of a driving means that moves the first optical element, a stopping accuracy of a driving means that moves the second optical element, optical aberrations, an F-number, and a permissible circle of confusion diameter of an imaging element provided in the imaging device.

8. The control device according to claim 4 , wherein the control unit repeatedly performs the first driving and the second driving.

9. The control device described in claim 1, characterized in that the first optical element is a lens provided in the lens device, and the second optical element is an imaging element provided in the imaging device.

10. The control device according to claim 9, characterized in that, when the imaging element reaches a first end of a movable range while performing the first drive, the control unit performs a third drive to stop or decelerate the first optical element and move the imaging element toward a second end of the movable range.

11. The control device according to claim 10 , wherein the control unit performs the first driving when the imaging element reaches the second end while performing the third driving.

12. The control device according to claim 10 or 11, wherein the control unit repeatedly performs the first driving and the third driving.

13. A control device as described in any one of claims 1 to 12, characterized in that the control unit is switched between a first control mode in which the minimum image plane movement speed is a first speed and a second control mode in which the minimum image plane movement speed is a second speed slower than the first speed based on one of the image plane movement speed and the image plane movement amount specified by the imaging device.

14. each of the first and second optical elements is a lens included in the lens device; The control device described in claim 13, characterized in that the control unit acquires the movement speeds of the first optical element and the second optical element in the second control mode based on at least one of the minimum driving speed of a driving means for moving the first optical element, the minimum driving speed of a driving means for moving the second optical element, a first sensitivity which is the amount of image plane movement per unit movement amount of the first optical element, and a second sensitivity which is the amount of image plane movement per unit movement amount of the second optical element.

15. each of the first and second optical elements is a lens included in the lens device; The control device according to claim 13 or 14, characterized in that in the first control mode, the control unit performs driving using first position characteristic data indicating a relationship between a subject distance and the positions of the first optical element and the second optical element, and in the second control mode, performs the first driving using second position characteristic data different from the first position characteristic data indicating a relationship between a subject distance and the positions of the first optical element and the second optical element, and performs a second driving that stops or decelerates the first optical element and moves the second optical element so that a difference between a position of the second optical element corresponding to the position of the first optical element based on the second position characteristic data and a current position of the second optical element is reduced.

16. When the second optical element is an imaging element provided in the imaging device, The control device according to claim 13, characterized in that the control unit acquires the movement speeds of the first optical element and the imaging element in the second control mode based on at least one of the minimum drive speed of a drive means for moving the first optical element, the minimum drive speed of a drive means for moving the imaging element, and a sensitivity which is an image plane movement amount per unit movement amount of the first optical element.

17. A control device according to any one of claims 1 to 16; and an optical system including the first optical element.

18. A control device according to any one of claims 1 to 16; and an imaging element.

19. A control method for a camera system including an imaging device and a lens device detachable from the imaging device, comprising: a first step of acquiring focus information from at least one of the imaging device and the lens device; a second step of controlling movement of a first optical element and a second optical element that are movable in an optical axis direction independently of each other in accordance with the focus information; A control method characterized in that, in the second step, when the first optical element and the second optical element are moved simultaneously, the second optical element is moved so as to reduce an amount of image plane movement corresponding to the movement of the first optical element.

20. A program causing a computer to execute the control method according to claim 19.

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