DRIVE DEVICE AND IMAGING APPARATUS

A drive device includes a piezoelectric element, a drive shaft that receives vibration of the piezoelectric element and vibrates along an optical axis direction of a first imaging optical system, an engagement member that is frictionally engaged with the drive shaft and is connected to the first imaging optical system, and a lens controller that controls vibration of the piezoelectric element, in which the first imaging optical system is provided to be movable in a range including at least a first position and a second position, and the lens controller performs control of moving the first imaging optical system from the first position to the second position in a case in which a signal for instructing a power of the drive device to be turned off is received.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(a) to Japanese Patent Application No. 2022-018069 filed on 8 Feb. 2022. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drive device that drives an imaging optical system and an imaging apparatus.

2. Description of the Related Art

JP2016-116352A discloses a drive device comprising an oscillator, an ultrasound motor including a friction member in frictional contact with the oscillator, and a controller that controls the ultrasound motor to drive a driven member. The controller counts the number of times that the ultrasound motor has passed through an activation position and an end position based on the detected position of the driven member, and changes the activation position and the end position in accordance with the counted number of times.

JP2013-76944A discloses a drive device comprising a housing, a barrel holder that is provided to be movable in an optical axis direction of a lens and holds the lens, and a piezoelectric element. The piezoelectric element and a drive shaft that is fixed to the piezoelectric element and receives vibration of the piezoelectric element are fixed to the barrel holder such that a longitudinal direction of the drive shaft is along the optical axis direction of the lens. The housing is provided with a shaft holding part that holds the drive shaft in a slidable state.

SUMMARY OF THE INVENTION

An embodiment according to the technology of the present disclosure provides a drive device and an imaging apparatus capable of suppressing, to the minimum, a damage of a drive shaft that occurs in a case in which a power is turned off and ensuring good operability.

One aspect of the technology of the present disclosure relates to a drive device that drives an imaging optical system, the device comprising a piezoelectric element, a drive shaft that receives vibration of the piezoelectric element and vibrates along an optical axis direction of the imaging optical system, an engagement member that is frictionally engaged with the drive shaft and is connected to the imaging optical system, and a processor that controls vibration of the piezoelectric element, in which the imaging optical system is provided to receive vibration of the piezoelectric element and to be movable in a range including at least a first position and a second position, and the processor performs control of moving the imaging optical system from the first position to the second position in a case in which a signal for instructing a power of the drive device to be turned off is received.

It is preferable that the processor perform control of moving the imaging optical system from the first position to the second position based on a time during which the piezoelectric element is in a stop state.

It is preferable that the first position be a position within a movement range in which the imaging optical system is moved in a case in which a signal for instructing the power of the drive device to be turned on is received, and the second position be a position other than the movement range in a range in which the imaging optical system is engaged with the drive shaft via the engagement member.

It is preferable that the first position be a position within a movement range for imaging that guarantees optical accuracy of the imaging optical system, and the second position be a position other than the movement range for imaging in a range in which the imaging optical system is engaged with the drive shaft via the engagement member.

It is preferable that the second position be located on outer sides of both ends of the movement range for imaging, and the processor perform control of moving the imaging optical system to the second position that is closer to the first position at which the imaging optical system is located among the second positions located on the outer sides of both ends in a case in which the signal for instructing the power to be turned off is received.

It is preferable that, in a case in which a maximum movement amount of movement of the imaging optical system within the movement range for imaging in the optical axis direction is denoted by A, an engagement length of engagement between the engagement member and the drive shaft is denoted by W, and a length of the drive shaft is denoted by L, a relationship of L>A+2W be satisfied.

It is preferable that, in a case in which a maximum movement amount of movement of the imaging optical system within the movement range for imaging in the optical axis direction is denoted by A, an engagement length of engagement between the engagement member and the drive shaft is denoted by W, and a length of the drive shaft is denoted by L, a relationship of L>A+3W be satisfied.

It is preferable that a lubricant reservoir portion for retaining a lubricant be provided on a track of the drive shaft, and the second position be located closer to the movement range for imaging than the lubricant reservoir portion in the optical axis direction.

It is preferable that a lubricant reservoir portion for retaining a lubricant be provided on a track of the drive shaft, and the second position be located on a side opposite to the lubricant reservoir portion in the optical axis direction with the movement range for imaging interposed therebetween.

It is preferable that, in a case in which a diameter of the drive shaft in a portion that is frictionally engaged with the engagement member in a case in which the imaging optical system is located at the first position is denoted by a first diameter, and a diameter of the drive shaft in a portion that is frictionally engaged with the engagement member in a case in which the imaging optical system is located at the second position is denoted by a second diameter, the first diameter be smaller than the second diameter.

It is preferable that, in a case in which a frictional force between the drive shaft and the engagement member in a portion that is frictionally engaged with the engagement member in a case in which the imaging optical system is located at the first position is denoted by a first frictional force, and a frictional force between the drive shaft and the engagement member in a portion that is frictionally engaged with the engagement member in a case in which the imaging optical system is located at the second position is denoted by a second frictional force, the first frictional force be smaller than the second frictional force. It is preferable that the drive shaft be a carbon shaft.

Another aspect of the technology of the present disclosure relates to an imaging apparatus comprising the drive device described above, and the imaging optical system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

As shown inFIG.1, a digital camera10comprises a camera body11and an interchangeable lens barrel12. A lens mount13, a release switch14, a power switch (not shown), and the like are provided on a front surface of the camera body11. The lens mount13has a circular-shaped imaging aperture13A. The lens barrel12is attachably and detachably mounted on the lens mount13. The digital camera10is an example of an imaging apparatus according to the present invention.

An imaging element16is built in the camera body11. The imaging element16is a complementary metal oxide semiconductor (CMOS) image sensor, a charge coupled device (CCD) image sensor, or an organic thin-film imaging element. The lens mount13is provided with a body-side signal contact17(seeFIG.14) inside the imaging aperture13A for electrically connecting the lens mount13to the lens barrel12to perform the communication. Moreover, the camera body11has a grip portion11A.

The lens barrel12comprises a lens barrel body21, an imaging optical system22, and a drive device23described below. The lens barrel body21has a cylindrical shape and holds the imaging optical system22and the drive device23therein, and is provided with a lens mount24(seeFIG.3) and a lens-side signal contact25(seeFIG.10) at a rear end thereof. The imaging optical system22images subject light on the imaging element16in a case in which the lens barrel12is mounted on the camera body11.

As shown inFIGS.2and3, the drive device23is disposed inside the lens barrel12. The drive device23drives a first imaging optical system22A which is a part of the imaging optical system22. The first imaging optical system22A corresponds to an “imaging optical system” within the scope of the claims. The drive device23is attached to the lens barrel body21via attachment members26and27, and the like.

The first imaging optical system22A comprises a focus lens51and a lens holding frame52. The lens holding frame52is formed in a cylindrical shape and holds the focus lens51. The lens holding frame52is connected to a holding member34described below.

As shown inFIG.4, the drive device23comprises a piezoelectric element31, a drive shaft32(seeFIGS.5to8, and10), an engagement member33, a holding member34, a position detection sensor35, a guide shaft36, a lens controller61, and a piezoelectric element drive driver62. The lens controller61controls the vibration of the piezoelectric element31via the piezoelectric element drive driver62. Moreover, as will be described below, the lens controller61controls each unit of the lens barrel12.

As shown inFIG.5, the piezoelectric element31is a bimorph type piezoelectric element including electrode layers on both surfaces of a piezoelectric body having an outer shape formed in a disk shape. Flexible substrates37are connected to both surfaces of the piezoelectric element31. The flexible substrate37is connected to the piezoelectric element drive driver62. In the piezoelectric element31, a piezoelectric body constituting the piezoelectric element31to which a voltage is applied by the piezoelectric element drive driver62via the flexible substrate37is, for example, a piezoelectric material, such as piezoelectric ceramics.

The piezoelectric element31has a planar shape without being curved in a voltage non-applied state. In a case in which a predetermined drive voltage is applied between the electrode layers to the piezoelectric element31by the piezoelectric element drive driver62such that one electrode layer has a negative potential and the other electrode layer has a positive potential, one electrode layer side of the piezoelectric body expands, and the other electrode layer side contracts, so that the piezoelectric element31is curved in a bowl shape (that is, a curved state in which one electrode layer side is convex). On the contrary, in a case in which the predetermined drive voltage is applied between the electrode layers to the piezoelectric element31such that one electrode layer has the positive potential and the other electrode layer has the negative potential, one electrode layer side of the piezoelectric body contracts, and the other electrode layer side expands, so that the piezoelectric element31is curved in a bowl shape (that is, a curved state in which the other electrode layer side is convex). Then, in a case in which the first imaging optical system22A is driven, the lens controller61periodically changes a direction in which the piezoelectric element31is convex by applying the voltage to vibrate the piezoelectric element31. It should be noted that an operation of moving the first imaging optical system22A by the vibration of the piezoelectric element31will be described below.

As shown inFIG.6, the drive shaft32is formed in a columnar shape, and one end thereof is bonded to the piezoelectric element31. The drive shaft32is a carbon shaft, for example. An outer diameter of the drive shaft32is smaller than an outer diameter of the piezoelectric element31. A central axis of the drive shaft32and a central axis of the piezoelectric element31coincide with each other. In the bonding between the drive shaft32and the piezoelectric element31, for example, one end of the drive shaft32is fitted into a through-hole formed in the center of the piezoelectric element31. Alternatively, the drive shaft32and the piezoelectric element31may be bonded to each other by an adhesive, soldering, or the like.

The drive shaft32is disposed in parallel with an optical axis OA of the imaging optical system22. Since the drive shaft32is bonded to the piezoelectric element31as described above, the drive shaft32receives the vibration of the piezoelectric element31and vibrates along an optical axis OA direction.

As shown inFIG.7, the piezoelectric element31and the drive shaft32are held by the holding member34. The holding member34is formed in a U-shaped bent shape. Specifically, in the holding member34, a pillar portion34A, and holding pieces34B and34C are integrally formed. The pillar portion34A is formed in a pillar shape having a rectangular cross section disposed in parallel with the optical axis OA.

The holding pieces34B and34C are disposed at a distal end portion and a base end portion of the pillar portion34A. Through-holes34D and34E are formed in the holding pieces34B and34C. In the drive shaft32, the distal end portion and the base end portion pass through the through-holes34D and34E and are held by the holding pieces34B and34C. It should be noted that a bearing member34F (seeFIGS.11A to12B) is provided inside the holding pieces34B and34C and around the drive shaft32. The bearing member34F is formed of an elastic body, such as rubber, and prevents the drive shaft32from being detached from the holding pieces34B and34C due to a frictional force generated between the bearing member34F and the drive shaft32.

A cylindrical-shaped rib34G is integrally formed with the holding piece34B. An inner diameter of the rib34G is formed in accordance with the outer diameter of the piezoelectric element31. As a result, in a case in which the drive shaft32is held by the holding pieces34B and34C, the rib34G holds the piezoelectric element31.

The holding member34is fixed to the attachment member26, for example, by screwing (seeFIG.3). As a result, the piezoelectric element31and the drive shaft32are attached to the lens barrel body21via the holding member34and the attachment member26.

As shown inFIG.8, the engagement member33includes a first member38, a second member39, and a screw member41. In the first member38, a connecting portion38A and a reception portion38B are integrally formed. A groove38C, a positioning protrusion38D, and a screw hole38E are formed in the reception portion38B. The groove38C is a V-shaped groove disposed in parallel with the optical axis OA. In a case in which the drive shaft32is engaged with the engagement member33, the drive shaft32comes into contact with the groove38C. Since the groove38C is formed in a V shape, an inclination of the first imaging optical system22A with respect to the drive shaft32is suppressed. A screw hole38F is formed in the connecting portion38A.

In the second member39, a pressing piece39A, a positioning opening39B, and a screw hole39C are formed. The positioning of the second member39in the optical axis OA direction is performed by fitting the positioning opening39B into the positioning protrusion38D of the first member38. The pressing piece39A is a flat spring having elasticity.

In a state in which the drive shaft32is disposed between the groove38C and the pressing piece39A, the screw member41is screwed with the screw hole39C of the second member39and the screw hole38E of the first member38to connect the first member38and the second member39, and the drive shaft32is interposed between the groove38C and the pressing piece39A. Since the drive shaft32receives a biasing force from the pressing piece39A, the drive shaft32is frictionally engaged with the engagement member33.

The piezoelectric element31, the drive shaft32, the engagement member33, and the holding member34are respectively disposed at positions that are rotationally symmetric about the optical axis OA of the imaging optical system22(that is, the optical axis of the first imaging optical system22A) by 180 degrees (seeFIG.4). That is, a pair of piezoelectric elements31, the drive shaft32, the engagement member33, and the holding member34are provided for the first imaging optical system22A.

As shown inFIG.9, in the lens holding frame52, screw holes52A are respectively provided at positions that are rotationally symmetric about the optical axis OA by 180 degrees. As shown inFIG.10, the lens holding frame52and the engagement member33are connected by screwing the screw member42with the screw holes52A and the screw hole38F. As described above, the engagement member33is frictionally engaged with the drive shaft32and is connected to the first imaging optical system22A. Further, the holding member34holds the drive shaft32and is attached to the lens barrel body21. That is, the first imaging optical system22A is attached to the lens barrel body21while holding a state being frictionally engaged with the drive shaft32via the engagement member33.

The position detection sensors35are respectively disposed at positions that are rotationally symmetric about the optical axis OA by 180 degrees (seeFIG.4). That is, a pair of position detection sensors35are provided for the first imaging optical system22A. The position detection sensor35detects a position of the lens holding frame52. Specifically, a magnet43and a magnetic sensor44are provided. For example, a multi-pole magnetizing magnet is used as the magnet43, and a magnetoresistive sensor (MR sensor) is used as the magnetic sensor44. The magnet43is attached to the lens holding frame52(seeFIG.9). The magnetic sensor44is attached to the lens barrel body21via the attachment member27to face the magnet43(seeFIG.3). The magnet43is magnetized in a pattern in which N poles and S poles are alternately arranged along the optical axis OA direction. A pattern width of the magnetization is, for example, about 100 μm. The magnetic sensor44is configured by using, for example, various magnetic resistance (MR) elements of which an electric resistance value is changed in accordance with strength of a magnetic field.

The magnetic sensor44outputs a pulse signal corresponding to the pattern of the magnet43in which the N poles and the S poles are alternately arranged or an electric signal that is changed periodically to the lens controller61. Based on this output, the lens controller61can detect the position of the lens holding frame52, that is, the first imaging optical system22A. It should be noted that the position detection sensor35is not limited to this, and may include, for example, a hall sensor formed of a hall element and a magnet.

Moreover, in the lens holding frame52, bosses52B protruding from an outer peripheral surface are respectively provided at positions that are rotationally symmetric about the optical axis OA by 180 degrees. The boss52B is formed with a guide hole52C (seeFIGS.5and9) into which the guide shaft36is movably fitted. A distal end portion and a base end portion of the guide shaft36are fixed to an attachment opening portion28(seeFIG.3) provided in the lens barrel body21. The guide shaft36is disposed in parallel with the optical axis OA direction. As a result, the guide shaft36guides the lens holding frame52, that is, the first imaging optical system22A in the optical axis OA direction.

The operation of moving the first imaging optical system22A in the optical axis OA direction by the vibration of the piezoelectric element31will be described with reference toFIGS.11A to12B. It should be noted that, inFIGS.11A to12B, in order to prevent the drawing from being complicated, the position detection sensor35, the guide shaft36, and the like are omitted. As shown inFIG.11A, in a state in which the first imaging optical system is stopped before the first imaging optical system22A is moved, the piezoelectric element31is in the voltage non-applied state, and has a planar shape.

First, as shown inFIG.11B, in a case in which the lens controller61controls the piezoelectric element drive driver62to apply the voltage having the negative potential for the electrode layer on the upper side in the drawing and the positive potential for the electrode layer on the lower side, the piezoelectric element31is displaced in a curved state that is convex to the upper side in the drawing. In this case, since the drive shaft32and the engagement member33are frictionally engaged with each other, the drive shaft32, the engagement member33, and the first imaging optical system22A are moved to the base end side of the optical axis OA by the same movement amount as a displacement amount D1(displacement amount from an initial position P0shown inFIG.11A) in which the piezoelectric element31is displaced in the optical axis OA direction.

Next, as shown inFIG.12A, contrary to the state shown inFIG.11B, in a case in which the lens controller61applies the voltage having the positive potential for the electrode layer on the upper side in the drawing and the negative potential for the electrode layer on the lower side, the piezoelectric element31is displaced in a curved state that is convex to the lower side in the drawing. In the case shown inFIG.12A, the lens controller61applies the voltage in a shorter time than in the case shown inFIG.11B, and moves the piezoelectric element31quickly. As a result, only the drive shaft32returns to the initial position P0shown inFIG.11Adue to an inertial force, and the engagement member33and the first imaging optical system22A remain at the positions moved by the displacement amount D1.

Further, as shown inFIG.12B, in a case in which the lens controller61applies the voltage in which the positive and negative potentials are reversed (that is, the same state as the case shown inFIG.11B) to the piezoelectric element31, the piezoelectric element31is displaced in the curved state that is convex to the upper side in the drawing. In this case, as in the case ofFIG.11B, the drive shaft32, the engagement member33, and the first imaging optical system22A are moved to the base end side of the optical axis OA by the same movement amount as the displacement amount D1in which the piezoelectric element31is displaced in the optical axis OA direction. That is, the drive shaft32, the engagement member33, and the first imaging optical system22A are moved twice the displacement amount D1from the initial position P0.

Then, in a case in which the lens controller61applies the voltage in which the positive and negative potentials are reversed (that is, the same state as shown inFIG.12A), the piezoelectric element31is displaced in the curved state that is convex to the lower side in the drawing. In this case, as in the case shown inFIG.12A, in a case in which the piezoelectric element31is moved quickly, only the drive shaft32returns to the initial position P0shown inFIG.11Adue to an inertial force, and the engagement member33and the first imaging optical system22A remain at the positions moved by the displacement amount D1×2 times from the initial position P0.

In this way, in a case in which the piezoelectric element31periodically changes the direction to be convex by the lens controller61repeating the application of the voltage, that is, the piezoelectric element31is vibrated, the engagement member33and the first imaging optical system22A can be moved along the drive shaft32. Moreover, in a case in which the engagement member33and the first imaging optical system22A are moved to the distal end side of the optical axis OA, a process reverse to the above, that is, an operation in which the piezoelectric element31is moved slowly in a case in which the piezoelectric element31is displaced in the curved state that is convex to the lower side in the drawing and the piezoelectric element31is moved quickly in a case in which the piezoelectric element31is displaced in the curved state that is convex to the upper side in the drawing need only be repeated.

The first imaging optical system22A is provided to receive the vibration of the piezoelectric element31and to be movable in a range including at least the first position and the second position. In the following, the first position and the second position at which the first imaging optical system22A is moved will be described.

As shown in a portion (A) inFIG.13, within a movement range RM of the first imaging optical system22A in the optical axis OA direction, a maximum movement amount of the movement of the first imaging optical system22A is denoted by A, an engagement length of the engagement between the engagement member33and the drive shaft32is denoted by W, and a length of the drive shaft32is denoted by L1. It should be noted that, in the portions (A) and (B) inFIG.13, for convenience of description, each component is shown in a simplified manner.

A first position P11is a position within the movement range RM. It should be noted that the position within the movement range RM as used herein means a case in which all the engagement members33are located within the movement range RM. The movement range RM is a movement range in which the first imaging optical system22A is moved in a case in which the lens controller61receives a signal for instructing the power of the drive device23to be turned on. Specifically, a control signal from a camera body controller71, which will be described below, corresponds to the signal for instructing the power of the drive device23to be turned on, and a range in which the lens controller61, which receives the control signal, moves the first imaging optical system22A is the movement range RM.

Further, in the present embodiment, since the first imaging optical system22A includes the focus lens51, the movement range RM is a movement range for imaging in which the first imaging optical system22A is moved in a case in which focus adjustment is performed by the control of the camera body controller71and an autofocus (AF) processing unit83described below. Therefore, in a case of moving in the movement range RM, the first imaging optical system22A should guarantee the optical accuracy. This is because, in a case in which the first imaging optical system22A is located in the movement range RM, in a case in which the displacement or the inclination occurs, the accuracy of the focus adjustment is reduced.

As shown in the portion (B) inFIG.13, a second position P12is a position other than the movement range RM in the range in which the first imaging optical system22A is engaged with the drive shaft32via the engagement member33. In the present invention, the position on the base end side of the movement range RM is the second position P12. The lens controller61performs control of moving the first imaging optical system22A from the first position to the second position in a case in which a signal for instructing the power of the drive device23to be turned off is received. That is, a stop signal (control signal for stopping the drive device23) from the camera body controller71described below corresponds to the signal for instructing the power of the drive device23to be turned off, and the position at which the lens controller61, which receives the stop signal, moves the first imaging optical system22A is the second position.

In the following, the length L1of the drive shaft32will be described in detail. In a case in which a length (including a length of the holding piece34B) of a range in the drive shaft32in which the first imaging optical system22A can be never moved, that is, a portion on the distal end side with respect to a portion in which the drive shaft32is held by the holding piece34B is denoted by a, a length (including a length of the holding piece34C) of a portion on the base end side with respect to a portion in which the drive shaft32is held by the holding piece34C is denoted by (3, a gap between the holding piece34B and the engagement member33in a case in which the first imaging optical system22A is nearest to the holding piece34B on the distal end side is denoted by a, a gap between the holding piece34C and the engagement member33in a case in which the first imaging optical system22A is nearest to the holding piece34C on the base end side (that is, in a case in which the first imaging optical system22A is at the second position P12) is denoted by b, and a gap between the engagement member33and the movement range RM in a case in which the first imaging optical system22A is at the second position P12is denoted by c, the length L1of the drive shaft32=α+a+W+A+c+W+b+β. Among these, the lengths α, β, the gaps a, b, c, and the like are dimensions for a margin in consideration of a dimensional error, and thus at least a relationship of L1>A+2W is needed.

As shown inFIG.14, the lens barrel12comprises a motor driver63and motors64and65, in addition to the imaging optical system22, the piezoelectric element31, the position detection sensor35, the lens controller61, and the piezoelectric element drive driver62.

The lens controller61consists of a microcomputer comprising a central processing unit (CPU), a read only memory (ROM) that stores programs or parameters used in the CPU, a random access memory (RAM) used as a work memory of the CPU (none of which is shown), and controls each unit of the lens barrel12. The piezoelectric element drive driver62, the motor driver63, and the position detection sensor35are connected to each other.

The lens controller61controls driving of a stop unit55, the first imaging optical system22A, and a second imaging optical system22B based on the control signal from the camera body controller71described below.

The imaging optical system22comprises a plurality of lenses including the first imaging optical system22A and the second imaging optical system22B, the stop unit55, and the like. As described above, the first imaging optical system22A includes the focus lens51and the lens holding frame52. The first imaging optical system22A is moved in the optical axis OA direction due to the vibration of the piezoelectric element31to adjust an imaging distance. The lens controller61transmits a control signal for moving the first imaging optical system22A to the piezoelectric element drive driver62in response to the control signal on a camera body11side. The piezoelectric element drive driver62applies the voltage based on the control signal to vibrate the piezoelectric element31.

The second imaging optical system22B includes a zoom lens53and a lens holding frame54that holds the zoom lens53. The second imaging optical system22B is moved in the optical axis OA direction due to the driving of the motor64and constitutes an electric zoom mechanism that magnifies an angle of view of the imaging optical system22. In the zoom mechanism, for example, a movement amount and a movement direction of the second imaging optical system22B are decided in response to the operation on the camera body11side. The angle of view of the imaging optical system22can be magnified by moving the second imaging optical system22B.

The stop unit55moves a plurality of stop leaf blades55A by driving of the motor65to change an amount of light incident on the imaging element16. The motor driver63controls the driving of the motors64and65based on the control of the lens controller61.

The camera body controller71comprises a CPU, a ROM that stores programs or parameters used in the CPU, and a RAM used as a work memory of the CPU (none of which is shown). The camera body controller71controls the camera body11and each unit of the lens barrel12connected to the camera body11. A release signal is input to the camera body controller71from the release switch14. Moreover, the body-side signal contact17is connected to the camera body controller71.

The lens-side signal contact25comes into contact with the body-side signal contact17in a case in which the lens mount24of the lens barrel12is mounted on the lens mount13of the camera body11, and the lens barrel12and the camera body11are electrically connected to each other.

A shutter unit72is a so-called focal plane shutter, and is disposed between the lens mount13and the imaging element16. The shutter unit72is provided to be able to block an optical path between the imaging optical system22and the imaging element16, and is changed between an opened state and a closed state. The shutter unit72is put into the opened state in a case of capturing a live view image and a video. In a case of capturing a still image, the shutter unit72is temporarily put into the closed state from the opened state. The shutter unit72is driven by a shutter motor73. The motor driver74controls the driving of the shutter motor73.

The imaging element16is driven and controlled by the camera body controller71. The imaging element16has a light-receiving surface configured by a plurality of pixels (not shown) arranged in a two-dimensional matrix. Each pixel includes a photoelectric conversion element, and performs photoelectric conversion of a subject image imaged on the light-receiving surface by the imaging optical system22to generate an imaging signal.

Moreover, the imaging element16comprises a signal processing circuit (none of which is shown), such as a noise removal circuit, an auto gain controller, and an A/D conversion circuit. The noise removal circuit performs noise removal processing on the imaging signal. The auto gain controller amplifies a level of the imaging signal to an optimum value. The A/D conversion circuit converts the imaging signal into a digital signal and outputs the converted signal from the imaging element16to a busline76. The output signal of the imaging element16is image data (so-called RAW data) having one color signal for each pixel.

An image memory75stores image data for one frame output to the busline76. An image data processing unit77reads out the image data for one frame from the image memory75and performs known image processing, such as matrix operation, demosaicing processing, y correction, brightness/color difference conversion, and resizing processing.

An LCD driver78sequentially inputs the image data for one frame subjected to the image processing by the image data processing unit77to an image display unit79. The image display unit79is provided, for example, on a rear surface of the camera body11and sequentially displays the live view images at regular intervals. A card interface (I/F)81is incorporated in a card slot (not shown) provided in the camera body11and is electrically connected to a memory card82inserted in the card slot. The card I/F81stores the image data subjected to the image processing by the image data processing unit77in the memory card82. Moreover, in a case in which the image data stored in the memory card82is reproduced and displayed, the card I/F81reads out the image data from the memory card82.

The camera body controller71transmits a control signal for driving the first imaging optical system22A, that is, the focus lens51, to the lens controller61in accordance with a phase difference detected by the AF processing unit83described below. Based on the control signal, the lens controller61controls the piezoelectric element drive driver62to move the first imaging optical system22A, and detects the position of the first imaging optical system22A by the position detection sensor35. Then, the lens controller61moves the first imaging optical system22A to a position at which the phase difference detected by the AF processing unit83is the minimum value.

The camera body controller71operates the stop unit55in accordance with exposure information calculated by an automatic exposure (AE) processing unit84described below, and transmits a control signal for changing a stop diameter to the lens controller61. The lens controller61controls the motor driver74based on the control signal, and controls the stop diameter of the stop unit55to obtain a stop value calculated by the AE processing unit84.

The AE processing unit84calculates an integrated value of each color signal from the image data for one frame. The camera body controller71calculates an appropriate exposure value based on the integrated value calculated for each image for one frame, and decides the stop value to be an appropriate exposure value calculated with respect to a preset shutter speed. The camera body controller71transmits the control signal to the lens controller61. The lens controller61controls the motor driver74based on the control signal, and operates the stop unit55at the stop diameter at which the decided stop value is obtained.

The AF processing unit83detects the phase difference by a pupil division method from the image data for one frame. It should be noted that, since the technology of the focus adjustment by the phase difference detection is well known, the detailed description thereof will be omitted. The camera body controller71detects the position (focus position) of the first imaging optical system22A at which the phase difference is the minimum value based on the phase difference calculated each time the image for one frame is obtained from the AF processing unit83and the position of the first imaging optical system22A detected by the position detection sensor35. The camera body controller71moves the first imaging optical system22A to the detected focus position, and stops the movement of the first imaging optical system22A. In this way, the focus adjustment is automatically performed without any operation by a user.

It should be noted that the AF processing performed by the camera body controller71and the AF processing unit83is not limited to the focus adjustment by the phase difference detection, and may be contrast type focus adjustment. In this case, the AF processing unit83calculates an AF evaluation value, which is an integrated value of high-frequency components, from the image data for one frame. The camera body controller71detects the position (focus position) of the first imaging optical system22A at which the AF evaluation value is the maximum value based on the AF evaluation value calculated each time the image for one frame is obtained from the AF processing unit83and the position of the first imaging optical system22A detected by the position detection sensor35. The following is the same as in the case of the phase difference detection, the camera body controller71moves the first imaging optical system22A to the detected focus position, and stops the movement of the first imaging optical system22A.

The operation of the digital camera10according to the present embodiment will be described. In a state in which the power switch (not shown) is operated by the user who is an imager to turn on the power, the power is supplied to each unit of the digital camera10.

In a state in which the power of the digital camera10is turned on, the imaging element16, the camera body controller71, the AF processing unit83, the lens controller61, the piezoelectric element drive driver62, the piezoelectric element31, the position detection sensor35, and the like are activated to perform the focus adjustment. As described above, in a case in which the control signal from the camera body controller71is received, the lens controller61moves the first imaging optical system22A within the movement range RM. Then, the lens controller61stops the first imaging optical system22A in a case in which the focus position is detected. In this way, in a case in which the lens controller61receives the signal for instructing the power of the drive device23to be turned on, the first imaging optical system22A is within the movement range RM, that is, at the first position.

Then, in a case in which the user finishes the imaging with the digital camera10and in a state in which the power is turned off, the focus adjustment operation described above is also finished. As described above, in a case in which the stop signal from the camera body controller71is received, the lens controller61performs the control of moving the first imaging optical system22A from the movement range RM (that is, the first position) to the second position. In a case in which the first imaging optical system22A is stopped at the second position, the power supply to each unit of the digital camera10is stopped.

As described above, in the drive device23, the first imaging optical system22A is provided to receive the vibration of the piezoelectric element31and to be movable in the range including at least the first position and the second position, and the lens controller61performs the control of moving the first imaging optical system22A from the first position to the second position in a case in which a signal for instructing the power of the drive device23to be turned off is received. Since the second position is a position other than the movement range RM, for example, in a case in which the digital camera10receives the vibration or the impact, even in a case in which an engagement portion of the drive shaft32with the engagement member33may have a damage or a recess, there is no influence on the operation of the first imaging optical system22A. That is, the drive device23can suppress, to the minimum, the damage to the drive shaft32that occurs in a case in which the power is turned off, and can ensure good operability.

First Modification Example

In the first embodiment, the example has been described in which the control of moving the first imaging optical system22A from the first position to the second position is performed in a case in which a signal for instructing the power of the drive device23to be turned off is received, but the present invention is not limited to this, and control of moving the imaging optical system from the first position to the second position may be performed based on a time during which the piezoelectric element31is in a stop state. In this case, as shown inFIG.15, the digital camera10is provided with a measurement unit that measures the time of the stop state.

In the first modification example, the lens controller61has a function of a measurement unit85. The measurement unit85measures the time of the stop state, for example, a time during which the stop signals continuously transmitted from the camera body11side are received. The lens controller61performs the control of moving the first imaging optical system22A from the first position to the second position in a case in which the time during which the stop signal is received exceeds a certain threshold value. It should be noted that the configuration of the measurement unit85is not limited to this, and the measurement unit85may be provided in the camera body controller71, or a timer integrated circuit (IC) may be provided separately from the lens controller61and the camera body controller71.

Second Embodiment

In the first embodiment, the second position is disposed only on the base end side of the movement range for imaging, but the present invention is not limited to this, and as shown in portions (A) and (B) inFIG.16, second positions P22are positions on outer sides of both ends of the movement range RM in the second embodiment described below.

In a drive device91according to the present embodiment, the second positions are provided on outer sides of both ends of the drive shaft32to make a drive shaft92, a holding member93, a guide shaft, and the like longer than the drive shaft32, the holding member34, the guide shaft36, and the like in the first embodiment. However, the present embodiment is the same as the first embodiment and the first modification example except for these differences, so that the description thereof will be omitted. In addition, in the portions (A) and (B) in FIG.16, for convenience of description, each component is shown in a simplified manner.

As shown in the portion (A) inFIG.16, the first position P11is the position within the movement range RM, as in the first embodiment. Moreover, as in the first embodiment, in a case in which the focus adjustment is performed by the control of the camera body controller71and the autofocus (AF) processing unit83, the movement range RM is the movement range for imaging in which the first imaging optical system22A is moved.

As shown in the portion (B) inFIG.16, the second position P22is a position other than the movement range RM in the range in which the first imaging optical system22A is engaged with the drive shaft92via the engagement member33. In the present embodiment, the positions on the distal end side and the base end side of the movement range RM are the second positions P22. The lens controller61performs control of moving the first imaging optical system22A from the first position to the second position in a case in which a signal for instructing the power of the drive device91to be turned off is received. It should be noted that, as in the first embodiment, the stop signal (control signal for stopping the drive device91) from the camera body controller71corresponds to the signal for instructing the power of the drive device91to be turned off.

Moreover, a length L2of the drive shaft92in the present embodiment is longer than the length L1of the drive shaft32in the first embodiment by the engagement length W of the engagement between the engagement member33and the drive shaft92and the gap c between the engagement member33and the movement range RM in a case in which the first imaging optical system22A is at the second position P22. That is, the length L2of the drive shaft32=α+a+W+c+W+A+c+W+b+β. Therefore, at least a relationship of L2>A+3W is needed.

In the present embodiment, since there are two second positions P22, in a case in which the signal for instructing the power to be turned off is received, the lens controller61determines the second position P22that is closer to the first position P11at which the first imaging optical system22A is located, from position information by the position detection sensor35. Then, the lens controller61performs control of moving the first imaging optical system22A to the second position P22closer to the first position P11at which the first imaging optical system22A is located. As a result, in a case in which the drive device23receives the signal for instructing the power to be turned off, the movement amount for moving the first imaging optical system22A is reduced. Therefore, in addition to the effects of the first embodiment, a probability of the drive shaft32being damaged in the movement range RM is further reduced, and a time until the power is turned off is shortened, and good operability can be ensured.

Second Modification Example

Moreover, as a modification example of each of the embodiments described above, as in the drive device94shown inFIGS.17A and17B, a lubricant reservoir portion96for retaining a lubricant may be provided in a track of the drive shaft95, a second position P32at which the first imaging optical system22A is moved may be a position closer to the movement range RM than the lubricant reservoir portion96in the optical axis OA direction. It should be noted that the lubricant reservoir portion96is, for example, a recessed portion that is recessed from an outer peripheral surface of the drive shaft95. Moreover, the configurations other than the lubricant reservoir portion96and the second position P32are the same as the configurations of each of the embodiments described above, and the description thereof will be omitted.

Third Modification Example

Moreover, as another modification example, as in the drive device97shown inFIGS.18A and18B, the lubricant reservoir portion96for retaining the lubricant may be provided on the track of the drive shaft98, and a second position P42at which the first imaging optical system22A is moved may be interposed between the movement ranges RM and may be a position on the side opposite to the lubricant reservoir portion96in the optical axis OA direction. It should be noted that the lubricant reservoir portion96is the same as the lubricant reservoir portion96of the second modification example. Moreover, the configurations other than the lubricant reservoir portion96and the second position P42are the same as the configurations of each of the embodiments described above, and the description thereof will be omitted.

Moreover, in each of the embodiments described above, diameters of the drive shafts32,92,95, and98are not mentioned, in a case in which the diameter of the drive shaft32in a portion that is frictionally engaged with the engagement member33in a case in which the first imaging optical system22A is located at the first position is denoted by a first diameter R1, and the diameter of the drive shafts32,92,95, and98in a portion that is frictionally engaged with the engagement member33in a case in which the first imaging optical system22A is located at the second position is denoted by a second diameter R2, it is preferable that the first diameter R1be smaller than the second diameter R2.

Alternatively, in a case in which a frictional force between the drive shafts32,92,95, and98and the engagement member33in a portion that is frictionally engaged with the engagement member33in a case in which the first imaging optical system22A is located at the first position is denoted by a first frictional force F1, and a frictional force between the drive shafts32,92,95, and98and the engagement member33in a portion that is frictionally engaged with the engagement member33in a case in which the first imaging optical system22A is located at the second position is denoted by a second frictional force F2, it is preferable that the first frictional force F1be smaller than the second frictional force F2.

In each of the embodiments described above, as the piezoelectric element31, the bimorph type piezoelectric element including the electrode layers on both surfaces of the piezoelectric body having the outer shape formed in the disk shape is used, but the present invention is not limited to this, and a unimorph type piezoelectric element including the electrode layer on only one surface may be used, or a lamination type piezoelectric element which is composed of laminated piezoelectric bodies and contracts in a direction in which the piezoelectric bodies are laminated may be used.

In each of the embodiments described above, the hardware structure of the processing unit that executes various types of processing, such as the lens controller61and the camera body controller71, is various processors as shown below. The various processors include a central processing unit (CPU), which is a general-purpose processor that executes software (program) and functions as various processing units, a graphical processing unit (GPU), a programmable logic device (PLD), which is a processor of which a circuit configuration can be changed after the manufacture, such as a field programmable gate array (FPGA), and a dedicated electric circuit, which is a processor having a circuit configuration specifically designed to execute various types of processing.

One processing unit may be composed of one of these various processors, or may be composed of a combination of two or more same or different types of processors (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). Moreover, a plurality of the processing units may be composed of one processor. As an example in which the plurality of processing units are composed of one processor, first, there is a form in which one processor is composed of a combination of one or more CPUs and software, and this processor functions as the plurality of processing units, as represented by a computer, such as a client or a server. Second, as represented by a system on chip (SoC) or the like, there is a form in which a processor, which realizes the functions of the entire system including the plurality of processing units with a single integrated circuit (IC) chip, is used. In this way, various processing units are composed of one or more of the various processors described above as the hardware structure.

More specifically, the hardware structure of these various processors is an electric circuit (circuitry) in a form of a combination of circuit elements, such as semiconductor elements.

It should be noted that, in each of the embodiments described above, the first imaging optical system22A including the focus lens51is described 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. Moreover, the present invention can be applied to an imaging apparatus, such as a smartphone or a video camera, in addition to the digital camera.

EXPLANATION OF REFERENCES