Drive device and imaging device

Abstract

To provide a driving device capable of securing excellent operability by minimizing the damage of a driving shaft caused when a power source is OFF and to provide an imaging apparatus.SOLUTION: A driving device 23 includes a piezoelectric element 31, a driving shaft which is vibrated along an optical axis OA direction of a first imaging optical system 22A by receiving the vibration of the piezoelectric element 31, an engagement member 33 which is frictionally engaged with the driving shaft and connected to the first imaging optical system 22A, and a lens control part 61 which controls the vibration of the piezoelectric element 31. The first imaging optical system 22A is provided to be movable in a range including at least a first position and a second position and the lens control part 61 performs control for moving the first imaging optical system 22A from the first position to the second position when receiving a signal for instructing the power-off of the driving device 13.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a driving device for driving an imaging optical system and an imaging device. [Background technology]

[0002] Patent Document 1 describes a driving device including an ultrasonic motor having a vibrator and a friction member in frictional contact with the vibrator, and a control unit that controls the ultrasonic motor to drive a driven member. The control unit counts the number of times the ultrasonic motor passes through a starting position and an end position based on the detected position of the driven member, and changes the starting position and the end position according to the counted number of times.

[0003] Patent Document 2 describes a drive device that includes a housing, a barrel holder that is movably arranged in the optical axis direction of the lens and holds the lens, and a piezoelectric element. The barrel holder is fixed with the piezoelectric element and a drive shaft that is fixed to the piezoelectric element and receives vibrations from the piezoelectric element, with the longitudinal direction of the drive shaft aligned with the optical axis direction of the lens. The housing is provided with a shaft holder that slidably holds the drive shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-116352 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-76944 Summary of the Invention

[0005] One embodiment of the technique of the present disclosure provides a drive device and an imaging device that can minimize damage to the drive shaft that occurs when the power is off and ensure good operability. [Means for solving the problem]

[0006] One aspect of a driving device according to the technology of the present disclosure is a driving device for driving an imaging optical system, comprising: a piezoelectric element; a driving shaft that vibrates along the optical axis direction of the imaging optical system in response to vibration of the piezoelectric element; an engaging member that frictionally engages with the driving shaft and is connected to the imaging optical system; and a processor that controls the vibration of the piezoelectric element; the imaging optical system is arranged to be movable within a range that includes at least a first position and a second position in response to vibration of the piezoelectric element; and the processor is a driving device that controls the imaging optical system to move from the first position to the second position when it receives a signal instructing it to power off.

[0007] The processor preferably controls the imaging optical system to move from the first position to the second position based on the time during which the piezoelectric element is in a stopped state.

[0008] The first position is preferably a position within the range of movement of the imaging optical system when a signal instructing the drive device to be powered on is received, and the second position is preferably a position outside the range of movement within the range in which the imaging optical system engages with the drive shaft via the engagement member.

[0009] It is preferable that the first position is a position within the imaging movement range that ensures the optical accuracy of the imaging optical system, and the second position is a position outside the imaging movement range within the range in which the imaging optical system engages with the drive shaft via the engagement member.

[0010] The second position is preferably located outside both ends of the imaging movement range, and when the processor receives a signal instructing to turn off the power, it preferably controls the imaging optical system to move to one of the second positions located outside both ends that is closer to the first position where the imaging optical system is located.

[0011] If the maximum movement amount of the first imaging optical system within the imaging movement range in the optical axis direction is A, the engagement length between the engagement member and the drive shaft is W, and the length of the drive shaft is L, it is preferable to satisfy the relationship L>A+2W.

[0012] If the maximum movement amount of the first imaging optical system within the imaging movement range in the optical axis direction is A, the engagement length between the engagement member and the drive shaft is W, and the length of the drive shaft is L, it is preferable to satisfy the relationship L>A+3W.

[0013] It is preferable that a lubricant reservoir for retaining lubricant is provided on the orbit of the drive shaft, and the second position is closer to the imaging movement range in the optical axis direction than the lubricant reservoir.

[0014] It is preferable that there is a lubricant reservoir on the orbit of the drive shaft for retaining lubricant, and that the second position is located on the opposite side of the lubricant reservoir in the optical axis direction, with the imaging movement range in between.

[0015] When the imaging optical system is in a first position, the diameter of the drive shaft at the portion that frictionally engages with the engaging member is defined as a first diameter, and when the imaging optical system is in a second position, the diameter of the drive shaft at the portion that frictionally engages with the engaging member is defined as a second diameter. It is preferable that the first diameter be smaller than the second diameter.

[0016] When the imaging optical system is in a first position, the frictional force between the drive shaft and the engaging member at the portion where the drive shaft and the engaging member frictionally engage is defined as a first frictional force, and when the imaging optical system is in a second position, the frictional force between the drive shaft and the engaging member at the portion where the drive shaft and the engaging member frictionally engage is defined as a second frictional force. The drive shaft is preferably a carbon shaft.

[0017] An imaging device according to one aspect of the technique of the present disclosure is an imaging device including the drive device described above and an imaging optical system. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is an exploded perspective view of the digital camera. [Figure 2] FIG. 1 is a plan view of a digital camera. [Figure 3] FIG. 2 is a cross-sectional view of a main part of a lens barrel. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 2 is a perspective view of a piezoelectric element, a drive shaft, and a holding member. [Figure 8] FIG. 2 is an exploded perspective view of a piezoelectric element, a drive shaft, and an engaging member. [Figure 9] FIG. [Figure 10] 10 is a perspective view illustrating a state in which the lens holding frame and the engagement member are connected to each other. [Figure 11] 1A and 1B are explanatory diagrams illustrating the operation of moving the imaging optical system in the optical axis direction by vibration of a piezoelectric element, showing a state in which no voltage is applied (A) and a state in which a voltage is applied so that the upper electrode layer of the piezoelectric element is at a negative potential and the lower electrode layer is at a positive potential (B). [Figure 12] 1A and 1B are explanatory diagrams illustrating the operation of moving the imaging optical system in the optical axis direction by vibration of a piezoelectric element, showing a state in which a voltage is applied so that the upper electrode layer of the piezoelectric element is at a positive potential and the lower electrode layer is at a negative potential, and a state in which a voltage is applied so that the upper electrode layer of the piezoelectric element is at a negative potential and the lower electrode layer is at a positive potential, respectively. [Figure 13] 10A and 10B are explanatory diagrams illustrating the relationship between the length of a drive shaft and a range of movement. [Figure 14] FIG. 1 is a block diagram showing a schematic configuration of a digital camera. [Figure 15] FIG. 10 is a block diagram showing a schematic configuration of a first modified example. [Figure 16] FIG. 10 is an explanatory diagram illustrating the relationship between the length of a drive shaft and the range of movement in the second embodiment. [Figure 17] FIG. 10 is an explanatory diagram illustrating the relationship between a lubricant reservoir and a range of movement in a second modified example. [Figure 18] FIG. 11 is an explanatory diagram illustrating the relationship between a lubricant reservoir and a range of movement in a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0019] [First embodiment] As shown in Fig. 1, digital camera 10 includes a camera body 11 and an interchangeable lens barrel 12. On the front of camera body 11 are provided lens mount 13, release switch 14, power switch (not shown), and other components. Lens mount 13 has a circular imaging opening 13A. Lens barrel 12 is detachably attached to lens mount 13. Digital camera 10 is an example of an imaging device according to the present invention.

[0020] An imaging element 16 is built into the camera body 11. The imaging element 16 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, or an organic thin-film imaging element. The lens mount 13 is provided with a body-side signal contact 17 (see FIG. 14) inside the imaging opening 13A for electrically connecting with the lens barrel 12 for communication. The camera body 11 also has a grip portion 11A.

[0021] Lens barrel 12 includes a lens barrel main body 21, an imaging optical system 22, and a drive unit 23 (described later). Lens barrel main body 21 is cylindrical and holds imaging optical system 22 and drive unit 23 inside, with a lens mount 24 (see FIG. 3) and a lens-side signal contact 25 (see FIG. 10) provided at its rear end. When lens barrel 12 is attached to camera body 11, imaging optical system 22 forms an image of subject light on image sensor 16.

[0022] 2 and 3, drive device 23 is disposed inside lens barrel 12. Drive device 23 drives first imaging optical system 22A, which is part of imaging optical system 22. First imaging optical system 22A corresponds to the "imaging optical system" in the claims. Drive device 23 is attached to lens barrel main body 21 via mounting members 26, 27, etc.

[0023] The first imaging optical system 22A includes a focus lens 51 and a lens holding frame 52. The lens holding frame 52 is formed in a cylindrical shape and holds the focus lens 51. The lens holding frame 52 is connected to a holding member 34, which will be described later.

[0024] 4, drive device 23 includes piezoelectric element 31, drive shaft 32 (see FIGS. 5 to 8 and 10), engagement member 33, holding member 34, position detection sensor 35, guide shaft 36, lens control unit 61, and piezoelectric element driver 62. Lens control unit 61 controls the vibration of piezoelectric element 31 via piezoelectric element driver 62. In addition, lens control unit 61 controls each part of lens barrel 12, as will be described later.

[0025] 5, the piezoelectric element 31 is a bimorph type piezoelectric element having electrode layers on both sides of a piezoelectric body formed into a disk-like outer shape. Flexible substrates 37 are connected to both sides of the piezoelectric element 31. The flexible substrates 37 are connected to a piezoelectric element driver 62. A voltage is applied to the piezoelectric element 31 by the piezoelectric element driver 62 via the flexible substrate 37. The piezoelectric body constituting the piezoelectric element 31 is made of a piezoelectric material such as piezoelectric ceramics.

[0026] When no voltage is applied, the piezoelectric element 31 is flat and not curved. When a predetermined drive voltage is applied between the electrode layers of the piezoelectric element 31 by the piezoelectric element driver 62 so that one electrode layer is at a negative potential and the other electrode layer is at a positive potential, one electrode layer side of the piezoelectric body expands and the other electrode layer side contracts, causing the piezoelectric element 31 to curve into a bowl shape (i.e., a curved state in which one electrode layer side is convex). Conversely, when a predetermined drive voltage is applied between the electrode layers of the piezoelectric element 31 so that one electrode layer is at a positive potential and the other electrode layer is at a negative potential, one electrode layer side of the piezoelectric body contracts and the other electrode layer side expands, causing the piezoelectric element 31 to curve into a bowl shape (i.e., a curved state in which the other electrode layer side is convex). When driving the first imaging optical system 22A, the lens control unit 61 applies a voltage to periodically change the convex orientation of the piezoelectric element 31, thereby vibrating the piezoelectric element 31. The operation of moving the first imaging optical system 22A by the vibration of the piezoelectric element 31 will be described later.

[0027] As shown in FIG. 6, the drive shaft 32 is formed in a cylindrical shape, and one end thereof is coupled to the piezoelectric element 31. The drive shaft 32 is, for example, a carbon shaft. The outer diameter of the drive shaft 32 is smaller than the outer diameter of the piezoelectric element 31. The central axis of the drive shaft 32 and the central axis of the piezoelectric element 31 coincide with each other. The drive shaft 32 and the piezoelectric element 31 are coupled, for example, by fitting one end of the drive shaft 32 into a through-hole formed in the center of the piezoelectric element 31. Alternatively, the drive shaft 32 and the piezoelectric element 31 may be bonded together using an adhesive, soldering, or the like.

[0028] The drive shaft 32 is disposed parallel to the optical axis OA of the imaging optical system 22. As described above, the drive shaft 32 is coupled to the piezoelectric element 31, and therefore vibrates along the optical axis OA in response to the vibration of the piezoelectric element 31.

[0029] 7, the piezoelectric element 31 and the drive shaft 32 are held by a holding member 34. The holding member 34 is formed in a U-shaped bent shape. Specifically, the holding member 34 is formed integrally with a pillar-shaped portion 34A and holding pieces 34B and 34C. The pillar-shaped portion 34A is formed in the shape of a pillar with a rectangular cross section that is arranged parallel to the optical axis OA.

[0030] The retaining pieces 34B, 34C are disposed at the distal and proximal ends of the columnar portion 34A. Through holes 34D, 34E are formed in the retaining pieces 34B, 34C. The distal and proximal ends of the drive shaft 32 pass through the through holes 34D, 34E and are held by the retaining pieces 34B, 34C. A bearing member 34F (see FIGS. 11 and 12) is provided inside the retaining pieces 34B, 34C and around the drive shaft 32. The bearing member 34F is made of an elastic material such as rubber, and the frictional force generated between the bearing member 34F and the drive shaft 32 prevents the drive shaft 32 from coming off the retaining pieces 34B, 34C.

[0031] A cylindrical rib 34G is formed integrally with the holding piece 34B. The inner diameter of the rib 34G is formed to match the outer diameter of the piezoelectric element 31. As a result, when the drive shaft 32 is held by the holding pieces 34B and 34C, the rib 34G holds the piezoelectric element 31.

[0032] The holding member 34 is fixed to the mounting member 26, for example, by screws (see FIG. 3). As a result, the piezo element 31 and the drive shaft 32 are attached to the lens barrel body 21 via the holding member 34 and the mounting member 26.

[0033] As shown in FIG. 8, the engagement member 33 is composed of a first member 38, a second member 39, and a screw member 41. The first member 38 has a connecting portion 38A and a receiving portion 38B formed integrally therewith. The receiving portion 38B has a groove 38C, a positioning protrusion 38D, and a screw hole 38E formed therein. The groove 38C is a V-shaped groove arranged parallel to the optical axis OA. When the drive shaft 32 engages with the engagement member 33, it abuts against the groove 38C. Because the groove 38C is formed in a V-shape, tilt of the first imaging optical system 22A with respect to the drive shaft 32 is suppressed. A screw hole 38F is formed in the connection portion 38A.

[0034] Second member 39 to The second member 39 has a pressing piece 39A, a positioning opening 39B, and a screw hole 39C. The second member 39 is positioned in the direction of the optical axis OA by fitting the positioning opening 39B onto a positioning protrusion 38D of the first member 38. The pressing piece 39A is an elastic leaf spring.

[0035] With the drive shaft 32 disposed between the groove 38C and the retaining piece 39A, the first member 38 and the second member 39 are connected by threading a screw member 41 into the screw hole 39C of the second member 39 and the screw hole 38E of the first member 38, and the drive shaft 32 is sandwiched between the groove 38C and the retaining piece 39A. The drive shaft 32 receives a biasing force from the retaining piece 39A and is thereby frictionally engaged with the engaging member 33.

[0036] The piezoelectric element 31, drive shaft 32, engagement member 33, and holding member 34 are respectively arranged at positions that are rotationally symmetrical by 180 degrees about the optical axis OA of the imaging optical system 22 (i.e., the optical axis of the first imaging optical system 22A) (see FIG. 4). That is, a pair of piezoelectric elements 31, drive shaft 32, engagement member 33, and holding member 34 are provided for the first imaging optical system 22A.

[0037] As shown in Fig. 9, the lens holding frame 52 has screw holes 52A formed at positions that are rotationally symmetrical by 180 degrees about the optical axis OA. As shown in Fig. 10, the lens holding frame 52 and the engaging member 33 are connected by threading the screw members 42 into the screw holes 52A and 38F. As described above, the engaging member 33 is frictionally engaged with the drive shaft 32 and is connected to the first imaging optical system 22A. Furthermore, the holding member 34 holds the drive shaft 32 and is attached to the lens barrel main body 21. That is, the first imaging optical system 22A is attached to the lens barrel main body 21 while maintaining frictional engagement with the drive shaft 32 via the engaging members 33.

[0038] The position detection sensors 35 are arranged at positions that are rotationally symmetrical by 180 degrees around the optical axis OA (see FIG. 4). That is, a pair of position detection sensors 35 are provided for the first imaging optical system 22A. The position detection sensors 35 detect the position of the lens holding frame 52. Specifically, the position detection sensors 35 are composed of a magnet 43 and a magnetic sensor 44. For example, a multi-pole magnetized magnet is used as the magnet 43, and a magnetoresistive sensor (MR sensor) is used as the magnetic sensor 44. The magnet 43 is attached to the lens holding frame 52 (see FIG. 9). The magnetic sensor 44 is attached to the lens barrel body 21 via the mounting member 27 so as to face the magnet 43 (see FIG. 3). The magnet 43 is magnetized in a pattern in which north and south poles are alternately arranged along the optical axis OA. The width of the magnetization pattern is, for example, approximately 100 μm. The magnetic sensor 44 is configured using, for example, various magnetoresistive (MR) elements whose electrical resistance value changes depending on the strength of a magnetic field.

[0039] The magnetic sensor 44 outputs a pulse signal or a periodically changing electrical signal corresponding to the alternating north-south pole arrangement pattern of the magnet 43 to the lens control unit 61. Based on this output, the lens control unit 61 can detect the position of the lens holding frame 52, i.e., the first imaging optical system 22A. Note that the position detection sensor 35 is not limited to this, and may be configured, for example, by a hall sensor using a hall element and a magnet.

[0040] The lens holding frame 52 is also provided with bosses 52B protruding from the outer peripheral surface at positions that are rotationally symmetrical by 180 degrees about the optical axis OA. Guide holes 52C (see FIGS. 5 and 9) into which the guide shafts 36 are movably fitted are formed in the bosses 52B. The distal and proximal ends of the guide shafts 36 are fixed to mounting openings 28 (see FIG. 3) provided in the lens barrel body 21. The guide shafts 36 are disposed parallel to the optical axis OA. As a result, the guide shafts 36 guide the lens holding frame 52, i.e., the first imaging optical system 22A, in the direction of the optical axis OA.

[0041] 11 and 12, the operation of moving the first imaging optical system 22A in the direction of the optical axis OA by vibration of the piezoelectric element 31 will be described. Note that in Fig. 11 and 12, the position detection sensor 35, guide shaft 36, etc. are omitted to avoid complication of the drawings. As shown in Fig. 11(A), before the first imaging optical system 22A moves, when the first imaging optical system is stopped, the piezoelectric element 31 is in a state where no voltage is applied, and therefore is flat.

[0042] First, as shown in FIG. 11B, the lens control unit 61 controls the piezo element driver 62 to apply a voltage that sets the upper electrode layer in the drawing at a negative potential and the lower electrode layer at a positive potential. application As a result, the piezoelectric element 31 is displaced to a curved state that is convex upward in the drawing. At this time, because the drive shaft 32 and the engagement member 33 are frictionally engaged, the drive shaft 32, the engagement member 33, and the first imaging optical system 22A move toward the base end of the optical axis OA by an amount equal to the displacement D1 by which the piezoelectric element 31 is displaced in the direction of the optical axis OA (the amount of displacement from the initial position P0 shown in FIG. 11A).

[0043] Next, as shown in FIG. 12A, the lens control unit 61 applies a voltage that sets the upper electrode layer in the drawing at a positive potential and the lower electrode layer at a negative potential, in contrast to the state shown in FIG. 11B. application 12A, the lens control unit 61 applies voltage in a shorter time than in the case shown in FIG. 11B. application 11A, and the engaging member 33 and the first imaging optical system 22A remain at the position where they were moved by the displacement amount D1.

[0044] Furthermore, as shown in FIG. 12B, the lens control unit 61 applies a voltage to the piezo element 31 with the positive and negative potentials reversed (i.e., the same state as shown in FIG. 11B). application 11B, the drive shaft 32, the engagement member 33, and the first imaging optical system 22A move toward the base end of the optical axis OA by the same amount of displacement D1 as the amount of displacement of the piezoelectric element 31 in the direction of the optical axis OA. In other words, the drive shaft 32, the engagement member 33, and the first imaging optical system 22A move from the initial position P0 by twice the amount of displacement D1.

[0045] Then, the lens control unit 61 switches the voltage with the positive and negative potentials reversed (i.e., the same state as shown in FIG. 12(A)). application 12A, if the piezoelectric element 31 is moved quickly, only the drive shaft 32 returns to the initial position P0 shown in FIG. 11A due to inertial force, and the engagement member 33 and the first imaging optical system 22A remain at a position moved by the displacement amount D1×2 from the initial position P0.

[0046] In this way, by repeatedly applying a voltage, the lens control unit 61 periodically changes the convex orientation of the piezoelectric element 31, that is, vibrates the piezoelectric element 31, and the engaging member 33 and the first imaging optical system 22A can move along the drive shaft 32. Furthermore, to move the engaging member 33 and the first imaging optical system 22A toward the tip side of the optical axis OA, the reverse process to the above can be performed, that is, the piezoelectric element 31 is moved slowly when the piezoelectric element 31 is displaced to a curved state convex downward in the figure, and the piezo element 31 is moved quickly when the piezo element 31 is displaced to a curved state convex upward in the figure.

[0047] The first imaging optical system 22A is provided so as to be movable within a range that includes at least a first position and a second position in response to vibration of the piezoelectric element 31. The first position and the second position to which the first imaging optical system 22A moves will be described below.

[0048] 13(A), within the movement range RM of the first imaging optical system 22A in the direction of the optical axis OA, the maximum movement amount of the first imaging optical system 22A is denoted by A, the engagement length of the engagement between the engagement member 33 and the drive shaft 32 is denoted by W, and the length of the drive shaft 32 is denoted by L1. Note that for the sake of convenience, the components are shown in a simplified form in FIGS. 13(A) and 13(B).

[0049] The first position P11 is a position within the movement range RM. Note that, here, a position within the movement range RM refers to a case where the entire engaging member 33 is located within the movement range RM. The movement range RM is a movement range within which the first imaging optical system 22A moves when the lens control unit 61 receives a signal instructing the driving device 23 to be powered on. Specifically, a control signal from a camera body control unit 71 (described later) corresponds to a signal instructing the driving device 23 to be powered on, and the movement range RM is a range within which the lens control unit 61, upon receiving this control signal, moves the first imaging optical system 22A.

[0050] Furthermore, in this embodiment, since the first imaging optical system 22A includes the focus lens 51, the movement range RM is an imaging movement range within which the first imaging optical system 22A moves when performing focus adjustment under the control of the camera body control unit 71 and the AF (Autofocus) processing unit 83, which will be described later. Therefore, when moving within this movement range RM, the first imaging optical system 22A must ensure optical accuracy. If the first imaging optical system 22A is within the movement range RM, but This is because if there is a positional deviation or tilt when the focus adjustment is performed, the accuracy of the focus adjustment will decrease.

[0051] 13(B), the second position P12 is a position outside the movement range RM within the range in which the first imaging optical system 22A engages with the drive shaft 32 via the engagement member 33. In the present invention, the position on the base end side of the movement range RM is defined as the second position P12. When the lens control unit 61 receives a signal instructing to power off the drive device 23, the lens control unit 61 controls to move the first imaging optical system 22A from the first position to the second position. That is, a stop signal (a control signal for stopping the drive device 23) from the camera body control unit 71 (described later) corresponds to a signal instructing to power off the drive device 23, and the position to which the lens control unit 61, upon receiving this stop signal, moves the first imaging optical system 22A is the second position.

[0052] The length L1 of the drive shaft 32 will be described in detail below. Let α be the range of the drive shaft 32 over which the first imaging optical system 22A cannot move, i.e., the length of the portion of the drive shaft 32 that is distal to the portion where the drive shaft 32 is held by the holding piece 34B (including the length of the holding piece 34B), β be the length of the portion of the drive shaft 32 that is proximal to the portion where the drive shaft 32 is held by the holding piece 34C (including the length of the holding piece 34C), a be the gap between the holding piece 34B and the engaging member 33 when the first imaging optical system 22A is closest to the distal holding piece 34B, b be the gap between the holding piece 34C and the engaging member 33 when the first imaging optical system 22A is closest to the proximal holding piece 34C (i.e., when the first imaging optical system 22A is at the second position P12), and c be the gap between the engaging member 33 and the moving range RM when the first imaging optical system 22A is at the second position P12. Then, the length L1 of the drive shaft 32 is α+a+W+A+c+W+b+β. Of these, the lengths α and β, and the gaps a, b, and c are dimensions with allowances that take into account dimensional errors, so the relationship of at least L1>A+2W is required.

[0053] As shown in FIG. 14, the lens barrel 12 includes an imaging optical system 22, a piezoelectric element 31, a position detection sensor 35, a lens control unit 61, a piezoelectric element driver 62, a motor driver 63, motors 64 and 65, and the like.

[0054] Lens control unit 61 is made up of a microcomputer equipped with a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores programs and parameters used by the CPU, and a RAM (Random Access Memory) (none of which are shown) used as work memory for the CPU, and controls each part of lens barrel 12. A piezoelectric element driver 62, a motor driver 63, and a position detection sensor 35 are connected to it.

[0055] The lens control unit 61 controls the driving of the aperture unit 55, the first imaging optical system 22A, and the second imaging optical system 22B based on a control signal from a camera body control unit 71, which will be described later.

[0056] The imaging optical system 22 includes a plurality of lenses including a first imaging optical system 22A and a second imaging optical system 22B, an aperture unit 55, etc. As described above, the first imaging optical system 22A includes a focus lens 51 and a lens holding frame 52. The first imaging optical system 22A moves in the direction of the optical axis OA by vibration of the piezoelectric element 31, and adjusts the imaging distance. The lens control unit 61 transmits a control signal to a piezoelectric element driver 62 to move the first imaging optical system 22A in accordance with a control signal from the camera body 11. The piezoelectric element driver 62 applies a voltage based on the control signal. application This causes the piezoelectric element 31 to vibrate.

[0057] The second imaging optical system 22B includes a zoom lens 53 and a lens holding frame 54 that holds the zoom lens 53. The second imaging optical system 22B is moved in the direction of the optical axis OA by driving a motor 64, constituting an electric zoom mechanism that varies the angle of view of the imaging optical system 22. In this zoom mechanism, the amount and direction of movement of the second imaging optical system 22B are determined in response to, for example, an operation on the camera body 11 side. The angle of view of the imaging optical system 22 can be varied by moving the second imaging optical system 22B.

[0058] The diaphragm unit 55 moves a plurality of diaphragm blades 55A by driving a motor 65, thereby changing the amount of light incident on the image sensor 16. A motor driver 63 controls the driving of the motors 64 and 65 based on the control of a lens control unit 61.

[0059] The camera body control unit 71 includes a CPU, a ROM that stores programs and parameters used by the CPU, and a RAM (none of which are shown) that is used as work memory for the CPU. The camera body control unit 71 controls the camera body 11 and various parts of the lens barrel 12 connected to the camera body 11. A release signal is input to the camera body control unit 71 from the release switch 14. A body-side signal contact 17 is also connected to the camera body control unit 71.

[0060] The lens side signal contact 25 comes into contact with the body side signal contact 17 when the lens mount 24 of the lens barrel 12 is attached to the lens mount 13 of the camera body 11, electrically connecting the lens barrel 12 and the camera body 11.

[0061] The shutter unit 72 is a so-called focal plane shutter, and is disposed between the lens mount 13 and the image sensor 16. The shutter unit 72 is provided so as to be able to block the optical path between the image sensor 16 and the image sensor 22, and is variable between an open state and a closed state. The shutter unit 72 is in the open state when capturing live view images and moving images. The shutter unit 72 temporarily switches from the open state to a closed state when capturing still images. The shutter unit 72 is driven by a shutter motor 73. A motor driver 74 controls the driving of the shutter motor 73.

[0062] The imaging element 16 is driven and controlled by the camera body control unit 71. The imaging element 16 has a light receiving surface made up of a plurality of pixels (not shown) arranged in a two-dimensional matrix. Each pixel includes a photoelectric conversion element, and performs photoelectric conversion on the subject image formed on the light receiving surface by the imaging optical system 22 to generate an imaging signal.

[0063] The image sensor 16 also includes signal processing circuits (none of which are shown), such as a noise reduction circuit, an auto-gain controller, and an A / D conversion circuit. The noise reduction circuit performs noise reduction processing on the image signal. The auto-gain controller amplifies the level of the image signal to an optimal value. The A / D conversion circuit converts the image signal into a digital signal and outputs it from the image sensor 16 to the bus line 76. The output signal from the image sensor 16 is image data (so-called RAW data) with one color signal for each pixel.

[0064] The image memory 75 stores one frame of image data output to the bus line 76. The image data processing unit 77 reads one frame of image data from the image memory 75 and performs known image processing such as matrix calculation, demosaic processing, gamma correction, luminance / color difference conversion, and resizing.

[0065] The LCD driver 78 sequentially inputs one frame's worth of image data that has been image-processed by the image data processing unit 77 to the image display unit 79. The image display unit 79 is provided, for example, on the rear surface of the camera body 11, and sequentially displays live view images at a regular interval. A card I / F (Interface) 81 is incorporated in a card slot (not shown) provided in the camera body 11, and is electrically connected to a memory card 82 inserted into the card slot. The card I / F 81 stores the image data that has been image-processed by the image data processing unit 77 in the memory card 82. When playing back and displaying the image data stored in the memory card 82, the card I / F 81 reads the image data from the memory card 82.

[0066] The camera body control unit 71 transmits a control signal to the lens control unit 61 to drive the first imaging optical system 22A, i.e., the focus lens 51, in accordance with the phase difference detected by the AF processing unit 83, which will be described later. Based on the control signal, the lens control unit 61 controls the piezoelectric element driver 62 to move the first imaging optical system 22A, and detects the position of the first imaging optical system 22A using the position detection sensor 35. Then, the lens control unit 61 moves the first imaging optical system 22A to a position where the phase difference detected by the AF processing unit 83 is at a minimum value.

[0067] The camera body control unit 71 operates the aperture unit 55 in accordance with exposure information calculated by an AE (Automatic Exposure) processing unit 84, which will be described later, and sends a control signal for changing the aperture diameter to the lens control unit 61. The lens control unit 61 controls the motor driver 74 based on the control signal, and controls the aperture diameter of the aperture unit 55 so as to obtain the aperture value calculated by the AE processing unit 84.

[0068] The AE processing unit 84 calculates the integrated value of each color signal from one frame of image data. The camera body control unit 71 calculates the appropriate exposure value based on the integrated value calculated for each frame of image, and determines the aperture value so that the appropriate exposure value calculated for a preset shutter speed is achieved. The camera body control unit 71 sends a control signal to the lens control unit 61. The lens control unit 61 controls the motor driver 74 based on the control signal, and operates the aperture unit 55 to an aperture diameter that achieves the determined aperture value.

[0069] The AF processing unit 83 detects a phase difference using a pupil division method from one frame of image data. Since the technology for focus adjustment using phase difference detection is well known, a detailed description will be omitted. The camera body control unit 71 detects the position (focus position) of the first imaging optical system 22A at which the phase difference is minimum, based on the phase difference calculated each time one frame of image is obtained by the AF processing unit 83 and the position of the first imaging optical system 22A detected by the position detection sensor 35. The camera body control unit 71 moves the first imaging optical system 22A to the detected focus position and stops the movement of the first imaging optical system 22A. In this way, focus adjustment is performed automatically without any user operation.

[0070] The AF processing performed by the camera body control unit 71 and the AF processing unit 83 is not limited to focus adjustment using phase difference detection, and may also be focus adjustment using a contrast method. In this case, the AF processing unit 83 calculates an AF evaluation value, which is an integrated value of high-frequency components, from one frame of image data. The camera body control unit 71 detects the position (focus position) of the first imaging optical system 22A at which the AF evaluation value is maximum, based on the AF evaluation value calculated by the AF processing unit 83 each time one frame of image is obtained and the position of the first imaging optical system 22A detected by the position detection sensor 35. Thereafter, as in the case of phase difference detection, the camera body control unit 71 moves the first imaging optical system 22A to the detected focus position and stops the movement of the first imaging optical system 22A.

[0071] The operation of the digital camera 10 of this embodiment will be described below. When a user who is the photographer operates a power switch (not shown) to turn on the power, power is supplied to each part of the digital camera 10.

[0072] When the power of the digital camera 10 is turned on, the image sensor 16, the camera body control unit 71, and the AF processing unit 8 3, the lens control unit 61, the piezoelectric element driver 62, the piezoelectric element 31, the position detection sensor 35, etc. are activated to perform focus adjustment. As described above, when a control signal is received from the camera body control unit 71, the lens control unit 61 moves the first imaging optical system 22A within the movement range RM. Then, when the lens control unit 61 detects the in-focus position, it stops the first imaging optical system 22A. In this way, when the lens control unit 61 receives a signal instructing to turn on the power of the drive device 23, the first imaging optical system 22A is within the movement range RM, i.e., at the first position.

[0073] Then, when the user ends image capture with the digital camera 10 and turns off the power, the focus adjustment operation described above also ends. As described above, when a stop signal is received from the camera body control unit 71, the lens control unit 61 controls the first imaging optical system 22A to move from within the movement range RM (i.e., the first position) to the second position. When the first imaging optical system 22A stops at the second position, the power supply to each unit of the digital camera 10 is stopped.

[0074] As described above, in the drive device 23, the first imaging optical system 22A is movable within a range that includes at least the first and second positions in response to vibrations of the piezoelectric element 31, and the lens control unit 61 controls the first imaging optical system 22A to move from the first position to the second position when it receives a signal instructing it to power off the drive device 23. This second position is outside the range of movement RM, so even if, for example, vibrations or shocks cause scratches or dents to form on the engagement portion of the drive shaft 32 with the engagement member 33, the operation of the first imaging optical system 22A is not affected. In other words, the drive device 23 minimizes damage to the drive shaft 32 that occurs when the power is off, ensuring good operability.

[0075] [First Modification] In the first embodiment described above, an example is given in which control is performed to move the first imaging optical system 22A from the first position to the second position when a signal instructing to power off the drive device 23 is received, but the present invention is not limited to this, and control may be performed to move the imaging optical system from the first position to the second position based on the time that the piezoelectric element 31 is in a stopped state. In this case, as shown in Fig. 15, the digital camera 10 is provided with a measurement unit that measures the time that the imaging optical system is in a stopped state.

[0076] In this first modified example, the lens control unit 61 has the function of the measurement unit 85. The measurement unit 85 measures the time of the stop state, for example, the time during which a stop signal continuously transmitted from the camera body 11 side is received. When the time during which the stop signal is received exceeds a certain threshold, the lens control unit 61 controls to move the first imaging optical system 22A from the first position to the second position. Note that the configuration of the measurement unit 85 is not limited to this, and it may be provided in the camera body control unit 71, or a timer IC (integrated circuit) may be provided separately from the lens control unit 61 and the camera body control unit 71. good stomach.

[0077] [Second embodiment] In the first embodiment described above, the second position is located only on the base end side of the imaging movement range, but the present invention is not limited to this, and in the second embodiment described below, as shown in Figures 16(A) and 16(B), the second position P22 is a position outside both ends of the movement range RM.

[0078] In the drive device 91 of this embodiment, the second positions are provided on the outer sides of both ends of the drive shaft 32, so that the drive shaft 92, holding member 93, guide shaft, etc. are formed longer than the drive shaft 32, holding member 34, guide shaft 36, etc. in the first embodiment, but other than these differences, the drive device 91 is the same as the first embodiment and the first modified example, and therefore description thereof will be omitted. Also, in Figures 16(A) and 16(B), for convenience of explanation, each part is illustrated in a simplified form.

[0079] 16A, the first position P11 is a position within the movement range RM, as in the first embodiment. Also, as in the first embodiment, the movement range RM is an image-capturing movement range within which the first image capturing optical system 22A moves when focus adjustment is performed under the control of the camera body control unit 71 and the AF (Autofocus) processing unit 83.

[0080] 16(B), the second position P22 is a position outside the movement range RM within the range in which the first imaging optical system 22A engages with the drive shaft 92 via the engagement member 33. In this embodiment, the positions on the distal end and proximal end sides of the movement range RM are defined as the second position P22. When the lens control unit 61 receives a signal instructing the driving device 91 to be powered off, the lens control unit 61 controls the first imaging optical system 22A to move from the first position to the second position. Note that, as in the first embodiment, a stop signal (a control signal for stopping the driving device 91) from the camera body control unit 71 corresponds to a signal instructing the driving device 91 to be powered off.

[0081] Furthermore, the length L2 of the drive shaft 92 in this embodiment is longer than the length L1 of the drive shaft 32 in the first embodiment by the engagement length W of the engagement member 33 and the drive shaft 92 and the gap c between the engagement member 33 and the movement range RM when the first imaging optical system 22A is at the second position P22. That is, the length L2 of the drive shaft 32 is expressed as α+a+W+c+W+A+c+W+b+β. Therefore, at least the relationship L2>A+3W is required.

[0082] In this embodiment, because there are two second positions P22, when the lens control unit 61 receives a signal instructing the power to be turned off, it determines the second position P22 that is closer to the first position P11 where the first imaging optical system 22A is located, based on position information from the position detection sensor 35. Then, the lens control unit 61 controls the first imaging optical system 22A to move to the second position P22 that is closer to the first position P11 where the first imaging optical system 22A is located. As a result, when the drive device 23 receives a signal instructing the power to be turned off, the amount of movement of the first imaging optical system 22A is reduced. Therefore, in addition to the effects of the first embodiment, the possibility of damage within the movement range RM of the drive shaft 32 is further reduced, and the time until the power is turned off is shortened, ensuring good operability.

[0083] [Second Modification] 17, a lubricant reservoir 96 for retaining lubricant may be provided on the orbit of a drive shaft 95, and a second position P32 to which the first imaging optical system 22A moves may be located closer to the movement range RM in the direction of the optical axis OA than the lubricant reservoir 96. The lubricant reservoir 96 is, for example, a recess recessed from the outer circumferential surface of the drive shaft 95. The configuration other than the lubricant reservoir 96 and the second position P32 is the same as that of the above embodiments, and therefore a description thereof will be omitted.

[0084] [Third Modification] 18, a lubricant reservoir 96 for retaining lubricant may be provided on the orbit of a drive shaft 98, and a second position P42 to which the first imaging optical system 22A moves may be located on the opposite side of the lubricant reservoir 96 in the direction of the optical axis OA, with the movement range RM therebetween. The lubricant reservoir 96 is the same as in the second modified example. The configuration other than the lubricant reservoir 96 and the second position P42 is the same as in each of the above embodiments, and therefore a description thereof will be omitted.

[0085] Furthermore, although the above embodiments do not mention the diameters of the drive shafts 32, 92, 95, and 98, for example, if the diameter of the drive shaft 32 at the portion that frictionally engages with the engaging member 33 when the first imaging optical system 22A is in a first position is a first diameter R1, and the diameter of the drive shaft 32, 92, 95, and 98 at the portion that frictionally engages with the engaging member 33 when the first imaging optical system 22A is in a second position is a second diameter R2, it is preferable that the first diameter R1 be smaller than the second diameter R2.

[0086] Alternatively, when the first imaging optical system 22A is in a first position, the frictional force between the drive shafts 32, 92, 95, 98 and the engaging member 33 at the portion where they frictionally engage with the engaging member 33 is defined as a first frictional force F1, and when the first imaging optical system 22A is in a second position, the frictional force between the drive shafts 32, 92, 95, 98 and the engaging member 33 at the portion where they frictionally engage with the engaging member 33 is defined as a second frictional force F2. It is preferable that the first frictional force F1 is smaller than the second frictional force F2.

[0087] In each of the above embodiments, a bimorph type piezoelectric element having an electrode layer on both sides of a piezoelectric body having a disk-shaped outer shape is used as the piezoelectric element 31, but this is not limited to this and a unimorph type piezoelectric element having an electrode layer on only one side may also be used, or a laminated type piezoelectric element made up of laminated piezoelectric bodies that expands and contracts in the direction in which the piezoelectric bodies are laminated.

[0088] In each of the above embodiments, the hardware structure of processing units that execute various processes, such as the lens control unit 61 and the camera body control unit 71, is the following various processors: The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and functions as various processing units, a GPU (Graphical Processing Unit), a PLD (Programmable Logic Device), which is a processor whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and a dedicated electrical circuit, which is a processor with a circuit configuration designed specifically for executing various processes.

[0089] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (for example, multiple FPGAs, a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). Also, multiple processing units may be configured with a single processor. Examples of multiple processing units configured with a single processor include, first, a configuration in which one processor is configured with a combination of one or more CPUs and software, as typified by client or server computers, and this processor functions as multiple processing units. Second, a configuration in which a processor is used that realizes the functions of an entire system including multiple processing units on a single IC (Integrated Circuit) chip, as typified by SoCs (System On Chips). In this way, the various processing units are configured with one or more of the above-mentioned various processors as a hardware structure.

[0090] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit in the form of a combination of circuit elements such as semiconductor elements.

[0091] In the above-described embodiments, the first imaging optical system 22A including the focus lens 51 is exemplified as the imaging optical system, but the present invention is not limited to this and may be applied to an imaging optical system including a zoom lens. Furthermore, the present invention is applicable to imaging devices other than digital cameras, such as smartphones and video cameras. [Explanation of symbols]

[0092] 10. Digital Camera 11 Camera body 11A Grip 12 Lens barrel 13 Lens mount 13A Imaging aperture 14 Release switch 16 image sensor 17 Body side signal contact 21 Lens barrel body 22 Imaging optical system 22A First imaging optical system 22B Second imaging optical system 24 lens mount 25 Lens side signal contact 26 Mounting material 27 Mounting material 28 Mounting opening 31 Piezo element 32 Drive shaft 33 Engagement member 34 Retaining member 34A Column part 34B, 34C holding piece 34D, 34E through hole 34F Bearing material 34G Rib 35 Position detection sensor 36 Guide shaft 37 Flexible PCB 38 First member 38A connection part 38B Receiving part 38C Groove 38D Positioning protrusion 38E screw hole 38F screw hole 39 Second member 39A Presser piece 39B Positioning opening 39C screw hole 41 Screw member 43 Magnet 44 Magnetic Sensor 51 Focus Lens 52 Lens holding frame 52A screw hole 52B Boss 52C Guide hole 53 Zoom Lens 54 Lens holding frame 55 Aperture unit 55A aperture blades 61 Lens control unit 62 Piezo element driver 63 Motor Driver 64, 65 motors 71 Camera body control unit 72 Shutter unit 73 Shutter motor 74 Motor Driver 75 Image Memory 76 Bus Line 77 Image data processing section 78 LCD Driver 79 Image display unit 81 Card I / F (Interface) 82 Memory Card 83 AF (Autofocus) processing unit 84 AE (Automatic Exposure) processing section 85 Measurement section 91 Drive unit 92 Drive shaft 93 Retaining member 94 Drive unit 95 Drive shaft 96 Lubricant reservoir 97 Drive Unit 98 Drive shaft D1 Displacement L1 length L2 length OA optical axis P0 initial position P11 1st position P12 2nd position P22 2nd position P32 2nd position P42 Second position RM movement range

Claims

1. A driving device for driving an imaging optical system, A piezoelectric element, a drive shaft that vibrates along the optical axis direction of the imaging optical system in response to vibration of the piezoelectric element; an engagement member that is frictionally engaged with the drive shaft and is connected to the imaging optical system; a processor for controlling the vibration of the piezoelectric element; the imaging optical system is provided so as to be movable within a range including at least a first position and a second position in response to vibration of the piezoelectric element; the processor performs control to move the imaging optical system from the first position to the second position when a signal instructing to power off the driving device is received; the first position is a position within an imaging movement range that ensures optical accuracy of the imaging optical system, the second position is a position outside the imaging movement range within a range in which the imaging optical system engages with the drive shaft via the engagement member, the second position is located outside both ends of the imaging movement range, The processor is a drive device that controls the movement of the imaging optical system to the second position located on the outside of both ends, which is closer to the first position where the imaging optical system is located, when it receives a signal instructing the power to be turned off.

2. A driving device for driving an imaging optical system, A piezoelectric element, a drive shaft that vibrates along the optical axis direction of the imaging optical system in response to vibration of the piezoelectric element; an engagement member that is frictionally engaged with the drive shaft and is connected to the imaging optical system; a processor for controlling the vibration of the piezoelectric element; the imaging optical system is provided so as to be movable within a range including at least a first position and a second position in response to vibration of the piezoelectric element; the processor performs control to move the imaging optical system from the first position to the second position when a signal instructing to power off the driving device is received; the first position is a position within an imaging movement range that ensures optical accuracy of the imaging optical system, the second position is a position outside the imaging movement range within a range in which the imaging optical system engages with the drive shaft via the engagement member, A lubricant reservoir for retaining lubricant is provided on the track of the drive shaft, The second position of the drive device is closer to the imaging movement range in the optical axis direction than the lubricant reservoir.

3. A driving device for driving an imaging optical system, A piezoelectric element, a drive shaft that vibrates along the optical axis direction of the imaging optical system in response to vibration of the piezoelectric element; an engagement member that is frictionally engaged with the drive shaft and is connected to the imaging optical system; a processor for controlling the vibration of the piezoelectric element; the imaging optical system is provided so as to be movable within a range including at least a first position and a second position in response to vibration of the piezoelectric element; the processor performs control to move the imaging optical system from the first position to the second position when a signal instructing to power off the driving device is received; the first position is a position within an imaging movement range that ensures optical accuracy of the imaging optical system, the second position is a position outside the imaging movement range within a range in which the imaging optical system engages with the drive shaft via the engagement member, A lubricant reservoir for retaining lubricant is provided on the track of the drive shaft, The second position is a position of the driving device that is located on the opposite side of the lubricant reservoir portion in the optical axis direction, with the imaging movement range sandwiched therebetween.

4. The processor:

4. The driving device according to claim 1, wherein control is performed to move the imaging optical system from the first position to the second position based on the time during which the piezoelectric element is in a stopped state.

5. the first position is a position within a movement range to which the imaging optical system moves when a signal instructing to turn on the power of the driving device is received, 4. The drive device according to claim 1, wherein the second position is a position outside the range of movement of the imaging optical system within a range in which the imaging optical system engages with the drive shaft via the engaging member.

6. 4. The drive device according to claim 1, wherein the relationship L > A + 2W is satisfied, where A is a maximum movement amount of the imaging optical system within the imaging movement range in the optical axis direction, W is an engagement length between the engagement member and the drive shaft, and L is a length of the drive shaft.

7. 2. The drive device according to claim 1, wherein the relationship L>A+3W is satisfied, where A is the maximum movement amount of the imaging optical system within the imaging movement range in the optical axis direction, W is the engagement length between the engagement member and the drive shaft, and L is the length of the drive shaft.

8. A driving device for driving an imaging optical system, comprising: A piezoelectric element, a drive shaft that vibrates along the optical axis direction of the imaging optical system in response to vibration of the piezoelectric element; an engagement member that is frictionally engaged with the drive shaft and is connected to the imaging optical system; a processor for controlling the vibration of the piezoelectric element; the imaging optical system is provided so as to be movable within a range including at least a first position and a second position in response to vibration of the piezoelectric element; the processor performs control to move the imaging optical system from the first position to the second position when a signal instructing to power off the driving device is received; a diameter of the drive shaft at a portion that frictionally engages with the engagement member when the imaging optical system is in the first position is set to a first diameter; When the imaging optical system is in the second position, the diameter of the drive shaft at the portion that frictionally engages with the engagement member is set to a second diameter, The first diameter is smaller than the second diameter.

9. A driving device for driving an imaging optical system, comprising: A piezoelectric element, a drive shaft that vibrates along the optical axis direction of the imaging optical system in response to vibration of the piezoelectric element; an engagement member that is frictionally engaged with the drive shaft and is connected to the imaging optical system; a processor for controlling the vibration of the piezoelectric element; the imaging optical system is provided so as to be movable within a range including at least a first position and a second position in response to vibration of the piezoelectric element; the processor performs control to move the imaging optical system from the first position to the second position when a signal instructing to power off the driving device is received; a friction force between the drive shaft and the engaging member at a portion where the drive shaft frictionally engages with the engaging member when the imaging optical system is in the first position is defined as a first friction force; When the imaging optical system is in the second position, the friction force between the drive shaft and the engaging member at the portion where the drive shaft and the engaging member are frictionally engaged is defined as a second friction force. The drive device, wherein the first friction force is smaller than the second friction force.

10. 10. The drive device according to claim 1, wherein the drive shaft is a carbon shaft.

11. An imaging device comprising the drive device according to any one of claims 1 to 10 and an imaging optical system.

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