Lens barrel and camera

A lens barrel includes a linear vibration actuator and a lens ring. The linear vibration actuator includes a vibrating element, relative motion member and pressurizing mechanism. The vibrating element generates a driving force at a driving face in parallel with an optical axis by oscillation of an electromechanical conversion element. The relative motion member is in pressure contact with the driving face and linearly moves in parallel with the optical axis with respect to the vibrating element. The pressurizing mechanism applies a pressure force between the driving face and the relative motion member. The lens ring holds a photographic lens and is linearly moved by the relative motion member in parallel with the optical axis. The linear vibration actuator includes a first linear guide receiving the pressure force applied to the relative motion member, and the lens ring includes a second linear guide guiding the lens ring to linearly move.

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2010-207115 filed on 15 Sep. 2010 and 2011-191586 filed on 2 Sep. 2011, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens barrel provided with a vibration actuator and to a camera.

2. Related Art

A vibration actuator, as disclosed in Patent Document 1, generates a progressive vibration wave (below abbreviated as “progressive wave”) at a driving face of an elastic body utilizing the expansion and contraction of a piezoelectric body. An elliptic motion is generated at the driving face by this progressive wave, and wave crests of the elliptic motion drive a moving element which is in pressure contact with the wave crests. Such a vibration actuator has the characteristic of having a high torque even at a low revolution rate. Therefore, when installed in a driving device, the vibration actuator has advantages that it is possible to omit gears of the driving device, so that it is possible to achieve silencing due to lack of gear noise and an increase in the positioning accuracy.

A technique is disclosed in Patent Document 2, which directly drives a lens barrel of a steel camera or an automatically focusing lens (hereinafter referred to as “AF lens”) of an interchangeable lens of an electronic camera, using a linear vibration actuator.

Patent Document 1: Japanese Examined Patent Application No. H1-17354

Patent Document 2: Japanese Unexamined Patent Application No. 2006-187114

SUMMARY OF THE INVENTION

The lens barrel having the linear vibration actuator recited in Patent Document 2 employs a pressure force that is applied between a vibrating element and a relative motion member in a radial direction. Structural members configured for applying the pressure force are disposed radially outward from a side surface of a holding frame for an AF lens. Accordingly, this lens barrel poses a problem to render its radial dimension to increase.

The present invention provides a lens barrel that enables its downsizing and a camera having this lens barrel.

The present invention solves the above problem. In order to facilitate understanding, explanations are made referring to added reference numbers which correspond to embodiments of the present invention, but the present invention is not limited by this.

In a first aspect of the present invention, a lens barrel (30) is provided, which includes a linear vibration actuator (10,210) and a lens ring (38,238). The linear vibration actuator (10,210) includes a vibrating element (35,235), a relative motion member (36,236) and a pressurizing mechanism (34,234). The vibrating element (35,235) is configured to generate a driving force at a driving face (35c) in parallel with an optical axis (OA) by oscillation of an electromechanical conversion element (50). The relative motion member (36,236) is configured to be in pressure contact with the driving face (35c) and to linearly move in parallel with the optical axis (OA) with respect to the vibrating element (35,235) by the driving force. The pressurizing mechanism (34,234) is configured to apply a pressure force between the driving face (35c) of the vibrating element (35,235) and the relative motion member (36,236). The lens ring (38,238) is configured to hold a photographic lens (L3) and to be linearly moved by the relative motion member (36,236) in parallel with the optical axis OA), along with the relative motion member (36,236).

The linear vibration actuator (10,210) includes a first linear guide (40,240) which receives the pressure force applied to the relative motion member (36,236), and the lens ring (38,238) includes a second linear guide (41,42,241,242) which guides the lens ring (38,238) to linearly move.

In a second aspect of the present invention, the lens barrel (30) according to the first aspect is employed in a camera (1).

In a third aspect of the present invention, a lens barrel (30) is provided, which includes a linear vibration actuator (10,210,410) and a lens ring (38,238,438).

The linear vibration actuator (10,210,410) includes a vibrating element (35,235,435), a relative motion member (36,236,436) and a pressurizing mechanism (34,234,434). The vibrating element (35,235,435) is configured to generate a driving force at a driving face (35c) in parallel with an optical axis (OA) by oscillation of an electromechanical conversion element (50). The relative motion member (36,236,436) is configured to be in pressure contact with the driving face (35c) and to linearly move in parallel with the optical axis (OA) with respect to the vibrating element (35,235,435) by the driving force. The pressurizing mechanism (34,234,434) is configured to apply a pressure force between the driving face (35c) of the vibrating element (35,235,435) and the relative motion member (36,236,436) in a direction not intersecting the optical axis (OA).

The lens ring (38,238,438) is configured to hold a photographic lens (L3) and to be linearly moved by the relative motion member (36,236,436) in parallel with the optical axis (OA), along with the relative motion member (36,236,436).

In a fourth aspect of the present invention, the lens barrel (30) according to the third aspect is employed in a camera (1).

The constitutions explained with the attached reference numbers may be suitably improved or may be at least a partly substituted with other constituent elements.

According to the present invention, it is possible to provide a downsizable lens barrel that mounts a linear vibration actuator and a camera provided with this lens barrel.

DETAILED DESCRIPTION OF THE INVENTION

Below, embodiments of a lens barrel, which is provided with a vibration actuator of the present invention, and of a camera, will be explained in detail with reference to the attached drawings.

FIG. 1is a drawing explaining an electronic camera1to which a lens barrel30is attached. The electronic camera1of the present embodiment is provided with an imaging element3, an AFE (analog front end) circuit4, and an image processing unit5.

The electronic camera1, which is further constituted of a sound detection unit6, a buffer memory7, a recording interface8, a monitor9, an operation unit13, a memory11, and a CPU12, is communicably connectable to an external PC14.

The imaging element3is constituted of a CMOS imaging element or the like, on which light receiving elements are two-dimensionally arranged on a light receiving face. The imaging element3performs photoelectric conversion of an image of a photographic subject generated by a luminous flux passing through a photographic optical system L of the lens barrel30, so that the imaging element3generates an analog image signal. The analog image signal is input to the AFE circuit4.

Then, an exposure time (shutter speed) applied to the imaging element3is determined by the operation unit13or a condition of the image of the photographic subject.

The AFE circuit4performs gain adjustment (signal amplification corresponding to the ISO sensitivity) of the analog image signal. More specifically, the AFE circuit4changes the image sensitivity within a predetermined range according to sensitivity setting instructions from the CPU12. The AFE circuit4further converts the image signal having undergone analog processing to digital data by a built in A/D conversion circuit. This digital data is input to the image processing unit5.

The image processing unit5performs various types of image processing of the digital image data.

The buffer memory7temporarily records pre-processing and post-processing image data for image processing performed by the image processing unit5.

The sound detection unit6, which is constituted of a microphone and a signal amplifier, mainly detects and captures sound from a direction of the photographic subject at the time of motion picture photography, and transmits this data to the CPU12. The sound detection unit6may employ a built-in microphone of the electronic camera1and an external microphone attached to an attachment point of the electronic camera1. The electronic camera1is so configured that the attached external microphone is detected.

The recording interface8having a connector (not shown) performs writing of data to a recording medium connected to the connector, or reading of data from the recording medium.

The monitor9is constituted of a liquid crystal panel or the like, and displays an image or an operation menu or the like in response to an instruction from the CPU12.

The operation unit13indicates a mode dial, cross key, setting button and release button to allow a user to input settings. The operation unit13sends an operation signal according to any operation made through the operation unit13to the CPU12. Settings for still photography and motion picture photography are set through the operation unit13.

The CPU12performs centralized control of operations performed by the electronic camera1by executing a computer program stored in a ROM (not shown). For example, it performs AF (autofocus) operation control, AE (auto-exposure) operation control, auto white balance control, and the like.

The memory11records sequential image data having undergone image processing.

The electronic camera1having such a constitution captures an image corresponding to a motion picture.

The lens barrel30attached to the electronic camera1has the photographic optical system L, which is constituted of a plurality of optical lenses that form an image of the photographic subject on the light receiving face of the imaging sensor3. InFIG. 1, an optical lens system is simplified and shown as a single lens. Further, among a group of optical lenses, an optical lens L3for autofocusing (shown inFIG. 2) is driven by the vibration actuator10.

First Embodiment

FIG. 2is a partial sectional view of the lens barrel30in which the vibration actuator10of the first embodiment is built in.FIG. 3is a partial enlargement view when seen from a direction A shown inFIG. 2.FIG. 4is a view when seen from a direction B-B shown inFIG. 2.

For ease of explanation and understanding an XYZ Cartesian coordinate system is provided in the drawings when necessary. In this coordinate system, a direction towards the left side when seen by a user is defined as +X direction, when the electronic camera1is positioned by the user to photograph a horizontally oblong image with an optical axis OA being set horizontal (below referred to as “normal position”). A direction going upwards is +Y direction while the electronic camera1is in the normal position. A direction towards the photographic subject is +Z direction while the electronic camera1is in the normal position.

The lens barrel30includes an outer fixed tube31which is fixed with respect to the electronic camera1, and the above mentioned photographic optical system L which includes optical lenses L1, L2, L3, and L4aligned in sequence from the photographic subject side.

The optical lens L3of the photographic optical system L is configured for autofocusing, and is driven by the vibration actuator10. Of the other optical lenses, the optical lenses L1and L2which are on a closer side of the photographic subject than the optical lens L3are fixed to an inner first fixed tube32A which is disposed at the photographic subject side inside the outer fixed tube31. The optical lens L4which is on a closer side of a formed image than the optical lens L3is fixed to an inner second fixed tube32B disposed at a formed image side inside the outer fixed tube31.

The vibration actuator10of the present embodiment is disposed at an outer circumferential face of the inner first fixed tube32A.

The vibration actuator10includes a support member33, a pressurizing spring34, a vibrating element35, a moving element36and a linear guide40. The support member33is fixed at the outer circumferential face of the inner first fixed tube32A. The pressurizing spring34is mounted at the support member33. The vibrating element35receives a pressure force applied by the pressurizing spring34. The moving element36is driven by the vibrating element35. The linear guide40is fixed at a fixing member32Aa provided on an outer face of the inner first fixed tube32A and contacts a face opposite to the vibrating element35of the moving element36.

The support member33, as shown inFIG. 4, is fixed at the outer circumferential face of the inner first fixed tube32A, slightly on +X side relative to the center and +Y side of the inner first fixed tube32A. The support member33has an extension33aextending in −Z direction parallel to the optical axis OA from the fixed portion of the support member33. The extension33ahas a rectangular cross section when cut at a face perpendicular to the optical axis OA.

The pressurizing spring34is a plate shaped member, one end of which is mounted at a side face33bfacing −X side of the extension33a.

The vibrating element35is an approximately rectangular parallelepiped member having a side face35afacing the side face33bof the extension33a. A groove35bextending in a direction perpendicular to the optical axis OA is provided at an approximately central portion of the side face35aof the vibrating element35.

The other end of the pressurizing spring34, one end of which is mounted at the side face33bof the support member33, is crimped at a predetermined angle in a transverse direction. An angled portion of the crimp fits into the groove35bof the side face35a, pressurizing the vibrating element35in the −X direction.

The moving element36is disposed adjacent to a driving face35cwhich is opposite (−X side) to the side face35aof the vibrating element35. The moving element36consists of a light metal such as aluminum, and has a sliding face36aopposite to the driving face35c. The sliding face36ais provided with sliding plating in order to improve the abrasion resistance.

The linear guide40, which is in contact with a face36b(−X side) opposite to the sliding face36aof the moving element36, is fixed at a guide fixing portion40A fixed to the inner first fixed tube32A.

The linear guide40is a linear bearing that causes the moving element36to be movable in a linear direction (Z direction inFIGS. 3 and 4) and to prevent from moving in other directions (X and Y directions). Spherical members and a smooth sliding member are provided inside the linear guide40. In this manner, it is possible for the linear guide40to provide smooth movement in the Z direction being free of sliding resistance even if urging forces are applied to in the X and Y directions.

A protruding portion37is provided at the sliding face36aof the moving element36.

Further, an AF ring38which holds the optical lens L3is disposed at an inner circumferential side of the inner first fixed tube32A.

The AF ring38has an annular cross section perpendicular to the optical axis OA, and is provided with guide portions43and44that outwardly project at symmetrical positions (both ends of the diameter along the Y axis) centered about the optical axis OA. The guide portions43and44include fitting holes43aand44a, respectively.

A first linear rail41and a second linear rail42are provided across the interval between the inner first fixed tube32A and the inner second fixed tube32B. The first linear rail41is inserted through the fitting hole43aof the guide portion43, and the second linear rail42is inserted through the fitting hole44aof the guide portion44.

A coupling portion39for coupling with the moving element36extends in the +Y direction at the −Z side of the AF ring38.

The coupling portion39is fixed to the AF ring38, and has a base portion39aprovided with a hole through which the first linear rail41passes, and a fork portion39bextending from the +X side of the base portion39ain the +Y direction (approximately radial direction). A groove39cis formed at a tip of the fork portion39b. The groove39cfits the protruding portion37provided at the sliding face36aof the moving element36. The driving force of the moving element36in a direction parallel to the optical axis OA is transmitted to the AF ring38by the coupling portion39, causing the AF ring38to be driven.

FIG. 5is a drawing explaining in detail the vibrating element35.

The vibrating element35is constituted of an electromechanical conversion element (below referred to as a piezoelectric body)50such as a piezoelectric element or an electrostrictive element or the like which converts electrical energy into mechanical energy, and sliding members51and52disposed at the driving face35cside of the electromechanical conversion element50. The vibrating element35generates standing waves of a longitudinal primary mode vibration and standing waves of a flexing secondary mode vibration.

A front face of the piezoelectric body50is provided with an electrode55divided into four sections (55a,55b,55c, and55d), and a rear face is provided with an undivided GND electrode. The four sections55a,55b,55cand55dof the electrodes55have the same polarization direction. A driving signal A phase is applied to the electrodes55aand55d, and a driving signal B phase is applied to the electrodes55band55c.

The above described groove35bis provided at the center portion of the vibrating element35. Since the pressurizing spring34engages with the groove35b, it is possible not only to prevent the pressurizing position from deviating, but also to provide support in a lengthwise direction.

The sliding members51and52are constituted of engineering plastic material having a good abrasion resistance. They are provided at locations where the amplitude of the standing waves of the longitudinal primary mode vibration is greatest, and further the amplitude of the standing waves of the flexing secondary mode vibration is greatest.

Next, the generation of vibrations in the vibrating element35will be explained in chronological sequence.FIG. 6is a diagram explaining the vibration generated by the vibrating element.

(a) t=1: The A phase voltage is minus and the B phase voltage is plus.

Since a portion P1where the electrode55aof the piezoelectric body50is provided shrinks in the lengthwise direction, a portion P2provided with the electrode55bextends in the lengthwise direction, a portion P3provided with the electrode55cextends in the lengthwise direction, and a portion P4provided with the electrode55dshrinks in the lengthwise direction, a bending deformation arises as shown at the right center side of (a) ofFIG. 6.

Further, since the portion P1shrinks in the lengthwise direction, the portion P2extends in the lengthwise direction, the portion P3extends in the lengthwise direction, and the portion P4shrinks in the lengthwise direction, displacements in the lengthwise direction offset each other. Accordingly, no longitudinal displacement occurs, as shown at the left center side of (a) ofFIG. 6.

(b) t=2: The A phase voltage is plus and the B phase voltage is minus.

The portion P1extends in the lengthwise direction, the portion P2extends in the lengthwise direction, the portion P3extends in the lengthwise direction, and the portion P4extends in the lengthwise direction. Thus, a bending deformation does not arise, as shown at the right center side of (b) ofFIG. 6.

Since the portions P1, P2, P3and P4extend in the lengthwise direction as described above, a deformation in the lengthwise direction arises as shown at the left center side of (b) ofFIG. 6.

(c) t=3: The A phase voltage is plus and the B phase voltage is minus.

Since the portion P1extends in the lengthwise direction, the portion P2shrinks in the lengthwise direction, the portion P3shrinks in the lengthwise direction, and the portion P4extends in the lengthwise direction, a bending deformation arises as shown at the right center side of (c) ofFIG. 6.

Since the portion P1extends in the lengthwise direction, the portion P2shrinks in the lengthwise direction, the portion P3shrinks in the lengthwise direction, and the portion P4extends in the lengthwise direction, lengthwise displacements offset each other. Accordingly, a longitudinal deformation does not arise as shown at the left center side of (c) ofFIG. 6.

(d) t=4: The A phase voltage is minus and the B phase voltage is plus.

Since the portion P1shrinks in the lengthwise direction, the portion P2shrinks in the lengthwise direction, the portion P3shrinks in the lengthwise direction, and the portion P4shrinks in the lengthwise direction, a bending deformation does not arise as shown at the right center side of (d) ofFIG. 6.

Since the portions P1, P2, P3and P4shrink in the lengthwise direction as described above, a displacement in the lengthwise direction arises, as shown at the center left side of (d) ofFIG. 6.

(e) t=5: Return to the case of t=1 in (a) above

When the vibrations described above are generated, points C and D where the sliding members51and52are bonded undergo an elliptic motion as shown at the rightmost side of (a) to (e) ofFIG. 6. The moving element36in pressure contact with these sliding members51and52receives a frictional force due to the elliptic motion, and is driven, accordingly.

FIG. 7is a block diagram explaining a driving device100of the vibration actuator10of the first embodiment. The driving/control of the vibration actuator10will be explained.

An oscillation unit101generates a driving signal of a desired frequency by instructions sent from a control unit102.

A phase shift unit103divides the driving signal generated by the oscillation unit101into two driving signals having a 90° phase shift.

Amplification units104and105respectively boost the two driving signals divided by the phase shift unit103to desired voltages.

The driving signals from the amplification units104and105are transmitted to the vibration actuator10. A standing wave is generated at the vibrating element35to which the transmitted driving signals applied. Accordingly, elliptical movement occurs at the sliding elements51and52, so that the moving element36is driven in a direction parallel to the optical axis OA.

The detection unit106is constituted of an optical encoder or a magnetic encoder or the like, and detects the position or speed of an object driven by the moving element36, and transmits the detected values to the control unit102as an electric signal.

The control unit102controls driving of the vibration actuator10based on driving instructions from the CPU12of the camera1or inside the lens barrel30. The control unit102receives a detection signal from the detection unit106, and based on its value, obtains the position information and velocity information, and controls the frequency of the oscillation unit101and the voltage of the amplification portions104and105to achieve positioning at a target position. Further, the control unit102receives the photographing information (still photography mode/motion picture mode) from the lens barrel30or the camera1. Based on this photographing information transmitted by the lens barrel30or the camera1, the control unit102finely controls the frequency of the driving signal.

According to the present embodiment, the present invention provides effects below.

With the vibration actuator10, the linear guide40receives the pressure force applied by the pressurizing spring34. By coupling the protruding portion37provided at the moving element36and the fork portion39bextending from the AF ring38, a driving force generated by the moving element36of the vibration actuator10is transmitted to the AF ring38, and the AF ring38is linearly driven. Accordingly, the first linear rail41and the second linear rail42which linearly guide the AF ring38are not subject to any force other than the linear driving force.

In this manner, the sliding resistance (loss) during linear motion of the optical lens L3is greatly reduced, and it is possible to provide driving of the optical lens L3with good efficiency.

Since the direction of the pressure to the vibrating element35is a direction tangential to the circumference of the lens barrel30such that the pressurizing spring34does not project in the radial direction of the lens barrel30, it is possible that an increase in the size of the lens barrel30in the radial direction is prevented and the linear vibration actuator10is compactly installed.

One end of the pressurizing spring34, another end of which is fixed at the supporting member33, applies a pressure force to the vibrating element35. The applied pressure force causes the vibrating element35to be pressed toward the moving element36. The applied pressure force is oriented in a direction orthogonal to and not intersecting the optical axis OA. More specifically, the applied pressure force is oriented in a direction tangential to a circumference of a circle centered about the optical axis OA. In other words, the vibration actuator10is attached to an external circumferential surface of the inner first fixed tube32A, which is cylindrical about the optical axis OA, and the pressure force applied by the pressurizing spring34of the vibration actuator10is oriented in a direction substantially tangential to the inner first fixed tube32A. Furthermore, the pressure force applied by the pressurizing spring34is oriented in a direction (−X direction) orthogonal to a line I (shown inFIG. 4), which connects the optical axis OA and the first linear rail41.

Since the pressurizing spring34does not protrude radially with respect to the lens barrel30, it is possible to prevent the lens barrel30from increasing its radial dimension, thereby allowing compact mounting of the linear vibration actuator10.

Respective members constituting the vibration actuator10, the pressurizing spring34, vibrating element35, moving element36, linear guide40, are arranged in juxtaposition in the direction orthogonal to and not intersecting the optical axis OA. More specifically, the members constituting the vibrating element actuator10are arranged in the direction tangential to the circumference of the circle centered about the optical axis OA. In other words, the members constituting the vibration actuator10are attached to the external circumferential surface of the inner first fixed tube32A, which is cylindrical about the optical axis OA, and the pressure force applied by the pressurizing spring34of the vibration actuator10is oriented in the direction substantially tangential to the inner first fixed tube32A. Furthermore, the members constituting the vibration actuator10are arranged in the direction (−X direction) orthogonal to the line I (shown inFIG. 4), which connects the optical axis OA and the first linear rail41.

Since the pressurizing spring34does not protrude in the radial direction of the lens barrel30, it is possible to prevent the lens barrel30from increasing its radial dimension, thereby enabling compact mounting of the vibration actuator10.

In addition, the pressure force generated in the vibration actuator is received by the linear guide40and the groove39cof the coupling portion39provided at the AF ring38is mated with the protruding portion37provided at the moving element36, so that the AF ring38is driven to move rectilinearly. In this manner, the first linear rail41and second linear rail42are free of forces other than a linearly driving force (a radial force is not exerted).

Accordingly, a sliding resistance (loss) of the AF lens L3during linear movement will decrease, enabling efficient driving of the AF lens L3.

Second Embodiment

FIG. 8is a drawing explaining a vibration actuator210of a lens barrel of the second embodiment of the present invention, and is a drawing corresponding toFIG. 3of the first embodiment. In the second embodiment, protruding portions237of a moving element236are provided both at sliding face236aof the moving element236and a side face236blocated on a side of a linear guide240. At a coupling portion239fixed to an AF ring238there are two fork portions239bextending from both ends of a base portion239a, and grooves239cformed at these fork portions239bare respectively fit with the protruding portions237at two locations. Others except for these differences described above are the same as the first embodiment, and explanations thereof will not be repeated.

A center axis of the moving element236and a center axis of a first linear rail241which guides the AF ring238are aligned in the same radial direction of the AF ring238. As mentioned above, the two fork portions239bof the coupling portion239fit with the protruding portions237at positions symmetrical about this radius.

In this way, the driving force of the moving element236is evenly applied to the coupling portion239and the AF ring238. Accordingly, during the linear driving of the AF ring238, forces in directions other than a linear direction (in particular forces in a rolling direction) are not applied to the AF ring238.

A fitting hole243aprovided at a guide portion243of the AF ring238is a circular hole. On the other hand, a fitting hole244aprovided at a guide portion244in the present embodiment is a u-shaped hole (u-shaped groove).

The u-shaped fitting hole244ahas the following advantages.

As shown inFIG. 9, the position of the coupling portion239is disposed displaced towards the −Z direction parallel to an optical axis OA, from a cross section perpendicular to the optical axis OA passing through the center O of an AF lens L3. Accordingly, a force acts on the AF ring238in a direction tilted with respect to the optical axis OA due to the position of its center of mass.

When the moving element236and the AF ring238are moving in an optical axis OA direction, a slight tilt may arise as a result of this force.FIG. 9is a drawing explaining the tilt with respect to the optical axis OA; the axis of the AF ring238inclines by α degrees with respect to the optical axis OA (such a large angle will not occur in actuality and the angle is exaggerated in the drawing). If the hole of the guide portion244is a circular hole and a linear force is applied to the coupling portion239, it may be possible that a sliding load arises between a second linear rail242and the hole of the guide portion244due to this inclination.

However, according to the present embodiment, even if the AF ring238slightly inclines, it is possible for the hole of the guide portion244, which is a u-shaped groove and has an open end, to escape in the radial direction.

Further, the center axis of the moving element236, the center axis of the first linear rail241and the center axis of the second linear rail242which guide the AF ring238are aligned with each other with respect to the radial direction of the AF ring238. In this way, when a tilting motion arises, the sliding load is further reduced.

Accordingly, it is possible that the sliding resistance (loss) during linear motion of the AF lens is further reduced in the second embodiment than in the first embodiment.

Third Embodiment

FIG. 10is a drawing explaining the third embodiment of the present invention.

The third embodiment, compared to the first embodiment, differs in the fitting method of a protruding portion337provided at a moving element and a groove339cof a fork portion339aconnected to an AF ring. Others except for these differences described above are the same as the first embodiment, and explanations thereof will not be repeated.

If there is a gap between the protruding portion337and the groove339c, at a time of startup or stopping, side faces of the protruding portion337and the groove339cwill collide with each other, generating an impact force which is transmitted to the AF ring. If this phenomenon is repeated, sliding portions of a linear rail and the groove339cwill suffer damage, and in this way a sliding resistance will arise.

In the embodiment shown inFIG. 10A, the protruding portion337is cylindrical and made of plastics, and its diameter is slightly greater than the width of the groove339c. The protruding portion337is inserted into the groove339c, causing the protruding portion337to mate with the coupling portion339(fork portion339a). Since the groove339cand the protruding portion337are mated with each other without a gap in the direction of the optical axis OA in this manner, rattling does not occur and there is no generation of an impact force resulting from collisions of the side faces of the protruding portion337and the groove339cat a time of startup and stopping. Accordingly, it is possible to reduce sliding resistance and there is no damage to the sliding portions of the linear rail and the guide portions.

Further,FIG. 10Bshows a modification of the third embodiment where a fork portion339a′ of a coupling portion339′ is made of two members held with a screw340, such that a protruding portion337′ is held between these two members. Since the protruding portion337′ mates with a groove339c′ without a gap in the direction of the optical axis OA in this modification as well as the third embodiment, rattling does not arise, and there is no generation of an impact force resulting from collisions of the side faces of the protruding portion337′ and the groove339c′ at a time of startup and stopping. Accordingly, it is possible to reduce sliding resistance and there is no damage to the sliding portions of the linear rail and the guide portions.

Fourth Embodiment

FIG. 11is a drawing explaining a vibration actuator410according to the fourth embodiment of the present invention. In the fourth embodiment, a moving element436and an AF ring438are integrally manufactured. Others except for this difference described above are the same as the first embodiment, and explanations thereof will not be repeated. A vibrating element435is in pressure contact with a moving element436by a pressurizing spring434, which is disposed between the vibrating element435and a support member433. The moving element436is pressed towards the linear guide440by a pressurizing spring434, and is linearly driven parallel to an optical axis OA by a driving force applied by the vibrating element435.

A guide portion444having a u-shaped groove444bin the same manner as in the second embodiment is formed at a position symmetric about the optical axis OA with respect to a portion of an AF ring438where a moving element436is provided. In the present embodiment, unlike the first or second embodiment, a first linear rail is not provided and only a second linear rail442is provided.

The second linear rail442is inserted into the groove444bof the guide portion444. The groove444bis also u-shaped in the same manner as in the second embodiment, such that it is possible for the second linear rail442to escape with respect to the guide portion444in a radial direction.

In the present embodiment, by integrating the moving element436and the AF ring438, it is possible to omit the first linear rail, therefore reducing the number of parts.

Further, a direction of pressurizing the vibration actuator410is arranged to coincide with the circumferential direction of a lens barrel and a space for taking out an output of the moving element436is provided in the radial direction of a lens barrel30in the same manner as in the above described embodiments. As a result, it is possible to connect the moving element436integrally with the AF ring438.

In the above described embodiments, the vibrating element is employed, in which the longitudinal primary vibration mode and a bending secondary vibration mode are combined. However, it may be alternatively possible to adopt other combinations of vibration modes, such as a vibration actuator combining a longitudinal primary vibration mode and a bending fourth vibration mode. As long as a linear vibration actuator is adopted, it may provide the similar effects.

Modified Example

It is assumed in the embodiments described above that the pressure applied to the vibrating element35is oriented in the direction orthogonal to and not intersecting the optical axis OA. However, it may alternatively be possible that the pressure is oriented in a direction not intersecting the optical axis OA, such as being skew with respect to the direction of the optical axis OA. In addition, it may alternatively be possible that the pressure is oriented in a direction not intersecting the optical axis OA, such as being slightly inclined from a direction orthogonal to the optical axis OA.