Lens driving device and camera

A lens driving device includes: a lens holder; a first coil wound onto the lens holder around the optical axis direction; a plurality of magnets having a first surface and a second surface perpendicular to the first surface, the magnets being disposed in a state in which the first surface opposes a circumferential surface of the first coil; a magnet holder that fixes the magnets apart from each other; a yoke constituting, together with the magnets, a magnetic circuit having a magnetic flux that traverses the first coil; a second coil provided opposite the second surface of the magnets; and a base on which the second coil is disposed. An auto-focus lens driving part that includes the lens holder, the first coil, the magnets, the magnet holder, and the yoke is held on the base so as to allow relative displacement in a direction perpendicular to the optical axis.

TECHNICAL FIELD

This invention relates to a lens driving device and a camera and, in particular, to a lens driving device and a camera that are suitable for a small-sized mobile terminal and that are capable of picking up images without blurs by stabilizing the image blurring (movement) occurring upon shooting an image.

BACKGROUND ART

Hitherto, various lens driving devices have been proposed which are capable of taking photographs with a high degree by stabilizing blurry images on an image-forming surface although there are blurry images (movement) upon shooting the static image.

As image stabilizing methods, “optical methods” such as a sensor shift method or a lens shift method and “a software stabilizing method” for stabilizing the blurry images using image processing by software are known. An image stabilizing method introduced in the mobile phone mainly adopts the software stabilizing method.

The software stabilizing method is disclosed, for example, in Japanese Unexamined Patent Application Publication No. H11-64905 (JP-A-11-064905) (PTL 1). The software stabilizing method disclosed in PTL1 comprises the steps of removing noise components from detected results of detection means, of calculating, from a detected signal in which the noise components are removed, particular information necessary to stabilize image blurred due to an image blurring of an image pickup device, thereby making a picked-up image be at a standstill in a nonshaking state where the image pickup device remains at rest.

However, the image stabilizing method of “the software stabilizing method” disclosed in PTL1 has a problem so that image quality degrades in compassion with the “optical method” which will later be described. In addition, the image stabilizing method of the software stabilizing method has disadvantage so that a taking time interval becomes longer because processing of the software is included therein.

Therefore, as the image stabilizing methods, request of “the optical methods” are on the increase with higher pixels in recent years. As the image stabilizing methods of “the optical methods”, “a sensor shift method”, “a lens shift method”, and “an optical unit tilt method” are known.

The sensor shift method is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2004-274242 (JP-A-2004-274242) (PTL 2). A digital camera disclosed in PTL 2 has structure in which an image pickup device (CCD) can shift with a center at a reference position (center) by an actuator. The actuator moves the CCD in response to blurry images detected by a blurry sensor to stabilize blurry images. The CDD is disposed in a CCD moving portion. The CCD can move in an X-Y plane orthogonal to a Z-axis by the CCD moving portion. The CCD moving portion mainly comprises three members: a base plate fixed to a housing; a first slider moving with respect to the base plate in a direction of an X-axis; and a second slider moving with respect to the first slider in a direction of a Y-axis.

However, in “the sensor shift method” as disclosed in PTL 2, the CCD moving portion (a movable mechanism) becomes large. It is therefore difficult in terms of size (outer dimensions, height) to adopt the image stabilizer of the sensor shift method to a miniature camera for a mobile phone.

Now, the description will proceed to the lens shift method.

By way of illustration, Japanese Unexamined Patent Application Publication No. 2009-145771 (JP-A-2009-145771) (PTL 3) discloses an image stabilizing device including an image stabilizing unit for driving a correction lens. The image stabilizing unit comprises a base plate serving as a fixed member, a movable mirror barrel holding the correction lens movably, three balls sandwiched between the base plate and the movable mirror barrel, and a plurality of elastic bodies for elastically supporting the movable mirror barrel with respect to the base plate, two coils fixed to the base plate, and two magnets fixed to the movable mirror barrel.

In addition, Japanese Unexamined Patent Application Publication No. 2006-65352 (JP-A-2006-065352) (PTL 4) discloses “an image stabilizing device” for stabilizing image blurred by moving and controlling a particular lens group (which will later be called “a correction lens”) among an image pickup optical system comprising a plurality of lens groups in two directions orthogonally crossing to each other within a plane perpendicular to an optical axis. In the image stabilizing device disclosed in PTL 4, the correction lens is movably supported with respect to a fixed frame up and down (in a pitch direction) and from side to side (in a yaw direction) via a pitching moving box and a yawing moving frame.

Japanese Unexamined Patent Application Publication No. 2008-26634 (JP-A-2008-026634) (PTL 5) discloses “an image stabilizing unit” including a stabilizing optical member for stabilizing blurry images formed by an imaging optical system by being moved to a direction crossed with an optical axis of the imaging optical system. In the stabilizing optical member disclosed in PTL 5, a lens holding flame for holding a correction lens is movably supported with respect to a receiving barrel in a pitch direction and a yaw direction via a pitch slider and a yaw slider.

Japanese Unexamined Patent Application Publication No. 2006-215095 (JP-A-2006-215095) (PTL 6) discloses “an image stabilizing device” which is capable of moving a correction lens by small driving force and which is capable of rapidly and accurately stabilizing the blurry images. The image stabilizing device disclosed in PTL 6 comprises a holding frame holding the correction lens, a first slider for slidably supporting the holding frame in a first direction (a pitch direction), a second slider for slidably supporting the holding frame in a second direction (a yaw direction), a first coil motor for driving the first slider in the first direction, and a second coil motor for driving the second slider in the second direction.

Japanese Unexamined Patent Application Publication No. 2008-15159 (JP-A-2008-015159) (PTL 7) discloses a lens barrel comprising an image stabilizing optical system provided to enable to move in a direction orthogonal to an optical axis. In the image stabilizing optical system disclosed in PTL 7, a movable VR unit disposed in a VR body unit holds a correction lens (a third lens group) and is disposed so as to enable to move in an X-Y plane orthogonal to the optical axis.

Japanese Unexamined Patent Application Publication No. 2007-212876 (JP-A-2007-212876) (PTL 8) discloses “an image stabilizer” which is capable to stabilize image blurred by performing control so that the optical axis of a correction lens held in a moving frame may be aligned with the optical axis of a lens system by moving the correction lens in first and second directions orthogonal to the optical axis of the lens system by driving means.

Japanese Unexamined Patent Application Publication No. 2007-17957 (JP-A-2007-017957) (PTL 9) discloses “an image stabilizer” for stabilizing image blurred by driving a correcting lens for stabilizing the blurry images that are formed by a lens system by operation of a lens driving part in a first direction and a second direction which are perpendicular to an optical axis of the lens system and which are perpendicular to each other. In the image stabilizer disclosed in PTL 9, the lens driving part is provided at one side of the correcting lens in the direction perpendicular to the optical axis.

Japanese Unexamined Patent Application Publication No. 2007-17874 (JP-A-2007-017874) (PTL 10) discloses “an image stabilizer” which is capable to stabilize blurry images by performing control so that the optical axis of a correction lens held in a moving frame may be aligned with the optical axis of a lens system by moving the correction lens in first and second directions which are perpendicular to the optical axis of the lens system and which are perpendicular to each other. The image stabilizer disclosed in PTL 10 comprises driving means including a coil and a magnet which can be relatively moved. One of the coil and the magnet is fixed to a moving frame while another is fixed to a supporting frame for supporting a movable frame movably. In addition, the image stabilizer disclosed in PTL 10 comprises a first Hall element for detecting position information related to the first direction of the correction lens by detecting a magnetic force of the magnet and a second Hall element for detecting position information related to the second direction of the correction lens by detecting the magnetic force of the magnet.

Any of the image stabilizers (the image stabilizing devices) of “the lens shift method” disclosed in the above-mentioned PTLs 3 to 10 has structure for moving and adjusting the correction lens in a plane perpendicular to the optical axis. However, such image stabilizers (the image stabilizing devices) have problems in which structure is complicated and they are unsuited for miniaturization. That is, like in the above-mentioned image stabilizer of the sensor shift method, it is difficult in terms of size (outer dimensions, height) to adopt the image stabilizer of the lens shift method to the miniature camera for the mobile phone.

In order to resolve the above-mentioned problems, an image stabilizer (an image stabilizing device) has been proposed which stabilizes blurry images (image blurred) by swinging a lens module (a camera module) for holding a lens and a pickup device (an image sensor) in itself. Such a method will be referred to herein as “an optical unit tilting method”.

Now, the description will proceed to “the optical unit tilting method”.

By way of illustration, Japanese Unexamined Patent Application Publication No. 2007-41455 (JP-A-2007-041455) (PTL 11) discloses “an image stabilizer of an optical device” comprising a lens module for holding a lens and an imaging element, a frame structure for rotatably supporting the lens module by rotary shafts, driving means (actuators) for rotating the lens module with respect to the frame structure by imparting driving force to driven parts (rotors) of the rotary shafts, and energizing means (leaf springs) for energizing the driving means (the actuators) to the driven parts (the rotors) of the rotary shafts. The frame structure comprises an inner frame and an outer frame. The driving means (the actuators) is disposed so as to be in contact with the driven parts (the rotors) of the rotary shafts from directions perpendicular to an optical axis. The driving means (the actuators) comprises a piezoelectric element and an action part of the rotary shafts side. The action part drives the rotary shafts by vertical vibrations and bending vibrations of the piezoelectric element.

However, it is necessary for the image stabilizer of “the optical unit tilting method” disclosed in PTL 11 to cover the lens module with the frame structure comprising the inner frame and the outer frame. As a result, there is a problem in which the image stabilizer becomes large.

In addition, Japanese Unexamined Patent Application Publication No. 2007-93953 (JP-A-2007-093953) (PTL 12) discloses “an image stabilizer for a camera” for stabilizing blurry images upon shooting a static image by accommodating a camera module in which a pickup lens and an image sensor are integrated in a housing, by swingably mounting the camera module in housing at a center of first and second axes which are orthogonal to a pickup optical axis and which cross each other at right angles, and by controlling the attitude of the camera module as a whole in the housing in response to a shake of the housing detected by a shake sensor. The image stabilizer for the camera disclosed in PTL 12 comprises an intermediate frame for swingably supporting an inner frame in which the camera module is fixed at the first axis as a center from the outside thereof, an outer frame, fixed to the housing, for swingably supporting the intermediate frame at the second axis as a center from the outside thereof, first driving means, mounted inside the intermediate frame, for swinging the inner frame around the first axis in response to a shake signal from a shake sensor (a first sensor module for detecting a shake in a pitch direction), and second driving means, mounted inside the outer frame, for swinging the intermediate frame around the second axis in response to a shake signal from a shake sensor (a second sensor module for detecting a shake in a yaw direction). The first driving means comprises a first stepping motor, a first reduction gear train for reducing a rotation thereof, and a first cam for swinging the inner frame through a first cam follower provided to the inner frame by rotating it integral with a final stage gear. The second driving means comprises a second stepping motor, a second reduction gear train for reducing a rotation thereof, and a second cam for swinging the intermediate frame through a second cam follower provided to the intermediate frame by rotating it integral with a final stage gear.

However, also in the image stabilizer of “the optical unit tilting method” disclosed in PTL 12, it is necessary to cover the camera module with the inner frame, the intermediate frame, and the outer frame. As a result, the image stabilizer becomes large. Furthermore, inasmuch as there are the rotary axes in “the optical unit tilting method”, there is a problem in which friction is produced between a hole and an axis and it results in exhibiting hysteresis.

Furthermore, Japanese Unexamined Patent Application Publication No. 2009-288770 (JP-A-2009-288770) (PTL 13) discloses an optical photography device which is capable of reliably stabilizing blurry images by improving the structure of a photography unit drive mechanism for stabilizing the blurry images in a photography unit. The optical photography device disclosed in PTL 13 comprises, inside a fixed cover, the photography unit (a movable module) and an image stabilizing mechanism for stabilizing blurry images by displacing the photography unit. The photography unit is for moving a lens along a direction of an optical axis. The photography unit comprises a moving body for holding the lens and a fixed aperture therein, a lens driving mechanism for moving the moving body in the direction of the optical axis, and a supporting body in which the lens driving mechanism and the moving body are mounted. The lens driving mechanism comprises a lens driving coil, a lens driving magnet, and a yoke. The photography unit is supported to a fixed body via four suspension wires. At two positions on both sides sandwiching the optical axis, a first photography unit drive mechanism and a second photography unit drive mechanism, which are for stabilizing the blurry images, are respectively provided as a pair. In each of their photography unit drive mechanisms, a photography unit drive magnet is held in a movable body side while a photography unit drive coil is held in a fixe body side.

However, in the optical photography device of “the optical unit tilting method” disclosed in PTL 13, it is necessary to use the photography unit drive magnets as well as the lens drive magnet. As a result, there is a problem in which the optical photography device becomes large.

In addition, Japanese Unexamined Patent Application Publication No. 2011-107470 (JP-A-2011-107470) (PTL 14) discloses a lens driving device which is capable of not only driving a lens in a direction of an optical axis but also stabilizing blurry images. The lens driving device disclosed in PTL 14 comprises a first holding body for holding the lens so as to be movable it in the direction of the optical axis (Z direction), a second holding body for holding the first holding body so as to be movable it in the Z direction, a fixed body for holding the second holding body so as to be movable it in a direction which is substantially orthogonal to the Z direction, a first driving mechanism for driving the first holding body in the Z direction, a second driving mechanism for driving the second holding body in an X direction, and a third driving mechanism for driving the second holding body in a Y direction. The first holding body is supported to the second holding body by a first supporting member made of an elastic material so as to be movable in the Z direction. The second holding body is supported to the fixed body by a second supporting member made of an elastic material so as to be movable in the Z direction. The first driving mechanism comprises a first drive coil and a first drive magnet, the second driving mechanism comprises a second drive coil and a second drive magnet, and the third driving mechanism comprises a third drive coil and a third drive magnet.

In the lens driving device disclosed in PTL 14, three kinds of driving mechanisms consisting of the first through the third driving mechanism require as driving mechanisms, and each of the first through third driving mechanisms comprises a coil and a magnet, independently. Therefore, there is a problem in which the number of parts is increased.

Japanese Unexamined Patent Application Publication No. 2011-113009 (JP-A-2011-113009) (PTL 15) discloses a lens driving device which uses a plurality of wires as the second supporting member and which comprises a buckling prevention member for preventing buckling of the wires while its basic structure is similar to the lens driving mechanism disclosed in the above-mentioned PTL 14. Each wire is formed in a straight line and the second holding member is supported by the wires so as to be movable in the direction which is substantially orthogonal to the Z direction. The buckling prevention member is made of an elastic member and becomes elastically deformed in the Z direction at a force smaller than a buckling load of the wire. More specifically, the buckling prevention member comprises a wire fixed portion formed to a leaf spring for the first supporting member. When a force applies to a movable part such as the second holding body downwards, the wire fixed portion becomes elastically deformed downwards.

In also the lens driving device disclosed in PTL 15, in the manner similar to the lens driving device disclosed in PTL 14, there is a problem in which the number of parts is increased.

Therefore, the present inventors (present applicants) proposed an image stabilizer which is capable of miniaturizing and lowering height by sharing a permanent magnet for an auto-focusing (AF) lens driving device as a permanent magnet for the image stabilizer (see, Japanese Unexamined Patent Application Publication No. 2011-65140 (JP-A-2011-065140) (PTL 16)).

The image stabilizer disclosed in PTL 16 is called an image stabilizer of “a barrel shift method” because camera shake is corrected by moving a lens barrel received in an AF lens driving device in itself. In addition, the image stabilizers of “the barrel shift method” are classified into “a moving magnet method” in which the permanent magnet moves (is movable) and “a moving coil method” in which the coil moves (is movable).

PTL 16 discloses, as the image stabilizer of “the moving magnet method” in a second exemplary embodiment thereof′, an image stabilizer which is provided with a permanent magnet comprising four first permanent magnet pieces and four second permanent magnet pieces which are disposed so as to apart from up and down in a direction of an optical axis and which is provided with a stabilizer coil disposed between the upper four first permanent magnet pieces and the lower four second permanent magnet pieces. That is, the second exemplary embodiment comprises the image stabilizer of “the moving magnet method” including the permanent magnet comprising eight permanent magnet pieces in total.

In the image stabilizer disclosed in PTL 16, a base is disposed so as to apart from at a bottom portion of the auto-focusing lens driving device and a plurality of suspension wires have one ends which are fixed to the base at outer regions thereof. The plurality of suspension wires has other ends which are firmly fixed to the auto-focusing lens driving device.

On the other hand, Japanese Patent Application Laid-Open No. 2011-128583 (PTL 17) discloses a lens driving device in which an AF magnet and an image stabilizer magnet are provided. The lens driving device disclosed in PTL 17 includes: the aforementioned first driving portion that includes a first magnet that is mounted to a focus portion, and a first coil that is mounted to a base portion and is disposed facing the first magnet, so as to thereby cause the focus portion to move relative to the base portion along a direction perpendicular to an optical axis; and a second driving portion that includes a second coil that is mounted to a lens portion, and a second magnet that is mounted to a focus base and is disposed facing the second coil.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The “software-type” image stabilizing method disclosed in PTL 1 has a problem of image quality degrading in comparison with an optical type, and also has the disadvantage of taking a long time, since it includes both imaging time and software processing time.

The “sensor-shifting” image stabilizer (digital camera) disclosed in the above-mentioned PTL 2 has a large CCD moving portion (movable mechanism), and is therefore difficult to apply to a small camera for mobile phone use from a size (external shape and height) standpoint.

On the other hand, each of the image stabilizers (image stabilizing devices) of “the lens shift method” disclosed in the above-mentioned PTLs 3 to 10 has a structure for moving and adjusting the correction lens in a plane perpendicular to the optical axis, and there is therefore a problem in that their structure is complex and is not suitable for miniaturization.

On the other hand, in the image stabilizing device of the “optical unit tilting method” disclosed in PTL 11, it is necessary to cover the lens module with a frame structure including an inner frame and an outer frame. As a result, there is the problem that the image stabilizing device becomes large. In the image stabilizer that adopts the “optical unit tilting method” disclosed in PTL 12 also, it is necessary to cover the camera module with an inner frame, an intermediate frame, and an outer frame. As a result, the image stabilizer becomes large. Furthermore, because a rotation shaft is used with the “optical unit tilting method”, there is also a problem of the occurrence of friction between a hole and the shaft, resulting in the occurrence of hysteresis. In the optical photography device that adopts the “optical unit tilting method” disclosed in PTL 13, it is necessary to use the photography unit drive magnets as well as the lens drive magnet. As a result, there is a problem that the optical photography device becomes large. In the lens driving device disclosed in PTL 14, three kinds of driving mechanisms consisting of a first to a third driving mechanism are required as driving mechanisms, and each of the first to third driving mechanisms includes a coil and a magnet, independently. Therefore, there is a problem that the number of parts is increased. In the lens driving device disclosed in PTL 15 also, similarly to the lens driving device disclosed in the aforementioned PTL 14, there is a problem that the number of parts is increased. In the image stabilizer disclosed in PTL 16, since the permanent magnet includes eight permanent magnet pieces, there is a problem that there are a large number of parts. Further, since an image stabilizer coil is disposed between four first permanent magnet pieces on an upper side and four second permanent magnet pieces on a lower side, there is also the problem that assembly of the image stabilizer requires time and effort. In the lens driving device disclosed in PTL 15, since a first driving portion and a second driving portion each include a coil and a magnet, independently, there is a problem that the number of parts is increased.

An object of the present invention is to provide a lens driving device and a camera that can be miniaturized.

Other objects of this invention will become clear as the description proceeds.

Solution to Problem

A lens driving device according to the present invention including:

a lens holder to which a lens barrel is mountable, the lens holder being movable in a direction of an optical axis;

a first coil wound around the lens holder about the optical axis;

a plurality of magnets that have a first surface magnetized to a south pole or a north pole and a second surface that is perpendicular to the first surface and the optical axis, the magnets being disposed in a state in which the first surface faces a circumferential face of the first coil;

a magnet holder that fixes the plurality of magnets apart from each other;

a yoke constituting, together with the plurality of magnets, a magnetic circuit that generates a magnetic flux that crosses the first coil;

a second coil that is provided facing the second surface of the magnet; and

a base on which the second coil is disposed;

wherein an auto-focusing lens driving portion that includes the lens holder, the first coil, the plurality of magnets, the magnet holder and the yoke is held so as to be relatively movable in a direction perpendicular to the optical axis with respect to the base.

A camera according to the present invention may include the above-described lens driving device incorporated therein.

Advantageous Effect of Invention

According to the present invention, a lens driving device and a camera that can be miniaturized can be provided.

DESCRIPTION OF EMBODIMENTS

Referring now to Figures, the description will proceed to exemplary embodiments of the present invention.

First Exemplary Embodiment

Referring toFIGS. 1 through 3, the description will proceed to lens driving device10according to a first exemplary embodiment of this invention.FIG. 1is an external perspective view of lens driving device10.FIG. 2is a partial vertical cross sectional view of lens driving device10.FIG. 3is an exploded perspective view of lens driving device10.

Herein, in the manner shown inFIGS. 1 through 3, an orthogonal coordinate system (X, Y, Z) is used. In a state illustrated inFIGS. 1 through 3, in the orthogonal coordinate system (X, Y, X), an X-axis direction is a fore-and-aft direction (depth direction), a Y-axis direction is a left-and-right direction (width direction), and a Z-axis direction is an up-and-down direction (height direction). In addition, in the example being illustrated inFIGS. 1 through 3, the up-and-down direction Z is a direction of optical axis O of a lens. In the exemplary embodiment, the X-axis direction (the fore-and-aft direction) is called a first direction while the Y-axis direction (the left-and-right direction) is called in a second direction.

However, in an actual use situation in which a user shoots a front subject, the direction of optical axis O, namely, the Z-axis direction becomes a fore-and-aft direction. In other words, an upper direction of the Z-axis becomes a front direction while a lower direction of the Z-axis becomes a rear direction.

The illustrated lens driving device10is mounted to small-sized mobile terminal T as shown inFIG. 44such as a cellular mobile phone, a smartphone, a notebook personal computer, a tablet-type personal computer or a mobile-type game machine, or to a web camera or a vehicle-mounted camera or the like. Lens driving device10comprises auto-focusing lens driving portion20which will later be described, and an image stabilizer portion (which will later be described) for stabilizing blurry images (vibrations) occurring in auto-focusing lens driving portion20upon shooting a static image and video, and is a device which is capable of picking up the image without image blurred. The image stabilizer portion of lens driving device10stabilizes the blurry images by moving the auto-focusing lens driving portion20in first direction (fore-and-aft direction) X and second direction (left-and-right direction) Y which are orthogonal to optical axis O and which are perpendicular to each other.

Auto-focusing lens driving portion20is for moving lens barrel12along optical axis O. Base14is disposed apart from a bottom portion of auto-focusing lens driving portion20on the underside in the optical axis direction. Image pickup board13on which image pickup device131is mounted is disposed on a lower portion (a rear portion) of base14. Image pickup device131converts a subject image (light) formed by lens barrel12into an electric signal.

Image pickup device131may, for example, comprise a CCD (charge coupled device) type image sensor, a CMOS (complementary metal oxide semiconductor) type image sensor, or the like. Infrared light filter132that blocks wavelengths in the infrared light region is disposed on the front surface of image pickup device131. Therefore, a camera module is constituted by combining auto-focusing lens driving portion20, image pickup board13and image pickup device131.

Base14has a ring-shaped which has the outside shape of a rectangular and which has circular opening14ain the interior thereof.

The image stabilizer portion of lens driving device10comprises four suspension wires16each having one ends fixed at four corner portions of base14, and image stabilizer coil18(second coil) disposed to face permanent magnet28of auto-focusing lens driving portion20.

Four suspension wires16extend along optical axis O and swingably support auto-focusing lens driving portion20as a whole in first direction (fore-and-aft direction) X and second direction (left-and-right direction) Y. Four suspension wires16have the other ends which are fixed to an upper end portion (first leaf spring32) of above-mentioned auto-focusing lens driving portion20.

In the manner described above, four suspension wires16serves as a supporting member for swingably supporting auto-focusing lens driving portion20with respect to base14in first direction Y and second direction Y.

The image stabilizer portion of lens driving device10comprises coil board40having a rectangular ring shape that is disposed apart from to face undersurface282cof permanent magnet28(see,FIG. 21). Coil board40is mounted on base14with flexible printed circuit (FPC)44sandwiched therebetween. Above-mentioned image stabilizer coil18is formed on coil board40.

Referring now toFIG. 3, the description will proceed to auto-focusing lens driving portion20. Auto-focusing lens driving portion20is also called an AF unit.

Auto-focusing lens driving portion20comprises lens holder24including tubular portion240for holding lens barrel12, focusing coil26(first coil) fixed so as to position around tubular portion240of lens holder24, permanent magnet28disposed opposite to focusing coil26at the outside of focusing coil26, magnet holder30for holding permanent magnet28, and first and second leaf springs32and34mounted on first end30a(upper end) and second end30b(lower end) of magnet holder30in the direction of optical axis O.

First and second leaf springs32and34support lens holder24in the direction of optical axis O shiftably so as to position lens holder24in a radial direction. In the example being illustrated, first leaf spring32is called an upper leaf spring while second leaf spring34is called a lower leaf spring.

In addition, in the manner which is described above, in the actual use situation in which a user shoots a front subject, the upper direction in the Z-axis direction (the direction of optical axis O) becomes the front direction while the lower direction in the Z-axis direction (the direction of optical axis O) becomes the rear direction. Accordingly, upper leaf spring32is also called a front-side spring while lower leaf spring34is also called a rear-side spring.

Magnet holder30has configuration of a substantially octagonal tube. Specifically, magnet holder30comprises outer tubular portion302made of a frame body of an octagonal tubular shape, octagonal upper ring-shaped end portion304provided at upper end (front end, first end)30aof outer tubular portion302, and octagonal lower ring-shaped end portion306provided at lower end (rear end, second end)30bof outer tubular portion302. Upper ring-shaped end portion304has eight upper protrusions304awhich project at four corners corresponding to short edges of octagon upwards by two per corner. Lower ring-shaped end portion306has four lower protrusions306awhich project at four corners corresponding to short edges of octagon downwards by one per corner.

Focusing coil26has an octagonal cylindrical shape which coincides with a shape of magnet holder30having the octagonal tubular shape. Permanent magnet28comprises four rectangular permanent magnet pieces282which are disposed in outer tubular portion302having the octagonal tubular shape in magnet holder30so as to apart from each other in first direction (fore-and-aft direction) X and second direction (left-and-right direction) Y. Four permanent magnet pieces282are disposed with spaces between them and focusing coil26. In the example being illustrated, each permanent magnet piece282has an inner end side polarized (magnetized) to the north pole and an outer end side polarized (magnetized) to the south pole. Hereunder, a surface (in this case, inner wall surface282a) facing a circumferential face of focusing coil26of permanent magnet piece282is referred to as “first surface”, a surface (in this case, the undersurface) that is perpendicular to the first surface and optical axis O is referred to as “second surface”, and a surface (in this case, the top surface) opposite to the second surface of permanent magnet piece282is referred to as “third surface”.

Upper leaf spring (front-side spring)32is disposed at an upper side (a front side) of lens holder24in the direction of optical axis O while lower leaf spring (rear-side spring)34is disposed at a lower side (a rear side) of lens holder24in the direction of optical axis O.

Upper leaf spring (front-side spring)32comprises upper inner end portion322mounted on an upper end portion of lens holder24and upper outer end portion324mounted on upper ring-shaped end portion304of magnet holder30. Between upper inner end portion322and upper outer end portion324, a plurality of upper arm portions326are provided. That is, the plurality of upper aim portions326connects upper inner end portion322to upper outer end portion324.

Tubular portion240of lens holder24has, at an upper end thereof, four upper protrusions240aprojecting at four corners upwards. Upper inner end portion322has four upper holes322ain which four upper protrusions240aare compression inserted (charged), respectively. That is, four upper protrusions240aof tubular portion240of lens holder24are compression inserted (charged) in four upper holes322aof upper inner end portion322of upper leaf spring32, respectively.

On the other hand, upper outer end portion324has eight upper holes324ain which eight upper protrusions304aof magnet holder30are charged, respectively. That is, eight upper protrusions304aof magnet holder30are charged in eight upper holes324aof upper outer end portion324.

Upper leaf spring (front-side spring)32further comprises four arc-shaped extending portions328which extend at four corners of upper outer end portion324in the radial direction outwards. Four arc-shaped extending portions328have four wire fixing holes328ain which the other ends of four suspension wires16are inserted (charged), respectively. A detailed structure of each arc-shaped extending portion328will later be described with reference toFIG. 29in detail.

Lower leaf spring (rear-side spring)34comprises lower inner end portion342mounted on a lower end portion of lens holder24and lower outer end portion344mounted on lower ring-shaped end portion306of magnet holder30. Between lower inner end portion342and lower outer end portion344, a plurality of lower arm portions346are provided. That is, the plurality of lower arm portions346connect lower inner end portion342to lower outer end portion344.

Lower leaf spring34has a lower portion in which spacer36having a substantially same outside shape is disposed. More specifically, spacer36comprises outer ring portion364having a shape which is substantially equivalent to that of lower outer end portion344of lower leaf spring34and inner ring portion362having a shape so as to cover lower inner end portion342and lower arm portions346of lower leaf spring34.

Tubular portion240of lens holder24has, at a lower end, four lower protrusions (not shown) projecting at four corners downwards. Lower inner end portion342has four lower holes342ain which the four lower protrusions are compression inserted (charged), respectively. That is, the four lower protrusions of tubular portion240of lens holder24are compression inserted (charged) in four lower holes342aof lower inner end portion342of lower leaf spring34.

On the other hand, lower outer end portion344of lower leaf spring34has four lower holes344ain which four lower protrusions306aof magnet holder30are charged, respectively. Outer ring portion364of spacer36also has four lower holes364ain which four lower protrusions306aof magnet holder30are compression inserted at positions corresponding to four lower holes344a, respectively. That is, four lower protrusions306aof magnet holder30are compression inserted in four lower holes364aof outer ring portion364of spacer36via four lower holes344aof lower outer end portion344of lower leaf spring34, and thermally-welded at tip ends thereof, respectively.

As is apparent fromFIG. 2, the four lower protrusions306aof magnet holder30protrude so as to approach coil board40. In other words, it will be understood that a gap between the four lower protrusions306aand coil board40is narrower than a gap in another region (that is, a gap between spacer36and coil board40).

An elastic member comprising upper leaf spring32and lower leaf spring34serves as a guiding arrangement for guiding lens holder24so as to be movable in the direction of optical axis O alone. Each of upper leaf spring32and lower leaf spring34is made of beryllium copper, phosphor bronze, or the like.

Tubular portion240of lens holder24has an inner wall in which female screw thread240bis cut. On the other hand, lens barrel12has an outer wall in which male screw thread12ascrewed in above-mentioned female screw thread240bis cut. In a case of fitting lens barrel12to lens holder24, it includes the steps of rotating lens barrel12with respect to tubular portion240of lens holder24around optical axis O to screw it along the direction of optical axis O thereby accommodating lens barrel12in lens holder24, and of connecting them to each other via an adhesive agent or the like.

In the manner which will later be described, by flowing an auto-focusing (AF) current through focusing coil26, it is possible to positionally adjust lens holder24(lens barrel12) in the direction of optical axis O according to interaction between a magnetic field of permanent magnet28and a magnetic field due to the AF current flowing through focusing coil26.

In the manner which is described above, auto-focusing lens driving portion (AF unit)20comprises lens holder24, focusing coil26, permanent magnet28, magnet holder30, upper leaf spring32, lower leaf spring34, and spacer36.

Referring now toFIG. 3, the description will proceed to the image stabilizer portion of lens driving device10in more detail.

In the manner which is described above, the image stabilizer portion of lens driving device10comprises four suspension wires16each having one ends fixed at four corner portions of base14, and image stabilizer coil18disposed to face permanent magnet28of above-mentioned auto-focusing lens driving portion20.

Four suspension wires16extend along optical axis O and swingably support auto-focusing lens driving portion20as a whole in first direction (fore-and-aft direction) X and second direction (left-and-right direction) Y. Four suspension wires16have the other ends which are fixed to the upper end portion of above-mentioned auto-focusing lens driving portion20.

More specifically, in the manner which is described above, four arc-shaped extending portions328of upper leaf spring32have wire fixing holes328ain which the other ends of suspension wires16are inserted (charged), respectively (see,FIG. 3). In four wire fixing holes328a, the other ends of four suspension wires16are inserted (charged) and are fixed by means of an adhesive agent, solder, or the like.

Although each arc-shaped extending portion328has an L-shape in the example being illustrated, of course, it is not limited to this.

Two of four suspension wires16are also used to feed to focusing coil26.

In the manner which is described above, permanent magnet28comprises four permanent magnet pieces282which are disposed so as to oppose to each other in first direction (the fore-and-aft direction) X and second direction (the left-and-right direction) Y

The image stabilizer portion of lens driving device10comprises ring-shaped coil board40which is inserted between four permanent magnet pieces282and base14and which is disposed so as to apart from them. Coil board40has, at four corners thereof, four through holes40athrough which four suspension wires16pass. Above-mentioned image stabilizer coil18is formed on coil board40.

The combination of base14, coil board40, image stabilizer coil18and flexible printed circuit (FPC)44serves as fixed member (14,40,18,44) that is disposed apart from auto-focusing lens driving portion20in optical axis O direction.

Herein, in four permanent magnet pieces282, the permanent magnet pieces disposed with respect to optical axis O at a front side, a rear side, a left side, and a right side are called front-side permanent magnet piece282f, rear-side permanent magnet piece282b, left-side permanent magnet piece282l, and right-side permanent magnet piece282r, respectively.

Referring toFIG. 4also, on coil board40, four image stabilizer coil portions18f,18b,18l, and18rare formed as image stabilizer coil18.

Disposed opposite to each other in first direction (fore-and-aft direction) X, two image stabilizer coil portions18fand18bare for moving (swinging) auto-focusing lens driving portion (AF unit)20in first direction (fore-and-aft direction) X. Such two image stabilizer coil portions18fand18bare called a first direction actuator. Herein, image stabilizer coil portion18fdisposed at a front side with respect to optical axis O is called “a front-side image stabilizer coil portion” while image stabilizer coil portion18bdisposed at a back side with respect to optical axis O is called “a back-side image stabilizer coil portion”.

On the other hand, disposed opposite to each other in second direction (the left-and-right direction) Y, two image stabilizer coil portions18land18rare for moving (swinging) auto-focusing lens driving portion (AF unit)20in second direction (the left-and-right direction) Y. Such two image stabilizer coil portions18land18rare called a second direction actuator. Herein, image stabilizer coil portion18ldisposed at a left side with respect to optical axis O is called “a left-side image stabilizer coil portion” while image stabilizer coil portion18rdisposed at a right side with respect to optical axis O is called “a right-side image stabilizer coil portion”.

As shown inFIG. 4, in illustrated image stabilizer coil18, front-side image stabilizer coil portion18fand left-side image stabilizer coil portion18lare divided into two coil parts so as to separate at a center in a longitudinal direction of front-side permanent magnet piece282fand left-side permanent magnet piece2821opposite thereto, respectively. That is, front-side image stabilizer coil portion18fcomprises left-side coil part18fland right-side coil part18fr. Likewise, left-side image stabilizer coil portion18lcomprises front-side coil part18lfand back-side coil part18lb.

In other words, each of front-side image stabilizer coil portion18fand left-side image stabilizer coil portion18rcomprises two loop portions while each of back-side image stabilizer coil portion18band right-side image stabilizer coil portion18rcomprises only one loop portion.

In the manner which is described above, among four image stabilizer coil portions18f,18b,18l, and18r, each of two particular image stabilizer coil portions18fand18ldisposed in first direction X and second direction Y is divided into two coil parts18fl,18frand18lf,18lbso as to separate it at the center of the longitudinal direction of permanent magnet pieces282fand282lopposite thereto.

Four image stabilizer coil portions18f,18b,18l, and18rconfigured as described above in cooperation with permanent magnet28are for driving auto-focusing lens driving portion (AF unit)20as a whole in the X-axis direction (the first direction) and the Y-axis direction (the second direction). A combination of four image stabilizer coil portions18f,18b,18l, and18rand permanent magnet28serves as a voice coil motor (VCM).

In the manner which is described above, the illustrated image stabilizer portion of lens driving device10stabilizes the blurry images by moving lens barrel12received in auto-focusing lens driving portion (AF unit)20in itself in first direction (fore-and-aft direction) X and second direction (left-and-right direction) Y. Accordingly, the image stabilizer portion of lens driving device10is called an image stabilizer portion of “a barrel shift method”.

Lens driving device10further comprises shielding cover42for covering auto-focusing lens driving portion (AF unit)20. Shielding cover42comprises rectangular tubular portion422for covering an outer periphery of auto-focusing lens driving portion (AF unit)20and upper end portion424for covering an upper surface of auto-focusing lens driving portion (AF unit)20. Upper end portion424has circular opening424aconcentric with optical axis O.

The illustrated image stabilizer portion of lens driving device10further comprises position detection arrangement50for detecting a position of auto-focusing lens driving portion (AF unit)20with respect to base14. Illustrated position detection arrangement50comprises a magnetic position detection arrangement comprising two Hall elements50fand50lmounted on base14. Two Hall elements50fand50lare disposed so as to oppose with a space to two of four permanent magnet pieces282, respectively, in the manner which will later be described. As shown inFIG. 2, each Hall element50fand50lis disposed so as to cross in a direction from the north pole to the south pole in permanent magnet piece282.

In the example being illustrated, one Hall element50fis called a front-side Hall element because Hall element50fis disposed at a front side in first direction (fore-and-aft direction) X with respect to optical axis O. Another Hall element50lis called a left-side Hall element because Hall element50lis disposed at a left side in second direction (left-and-right direction) Y with respect to optical axis O.

Front-side Hall element50fis disposed on base14at a position where front-side image stabilizer coil portion18fhaving divided two coil parts18fland18fris separated into two coil parts18fland18fr. Similarly, left-side Hall element50lis disposed on base14at a position where left-side image stabilizer coil portion18lhaving divided two coil parts18lfand18lbis separated into two coil parts18lfand18lb.

In the manner which is described above, two Hall elements50fand50lare disposed on base14at the positions where particular two image stabilizer coil portions18fand18lhaving divided two coil parts18fl,18frand18lf,18lbare separated into two coil parts18fl,18frand18lf,18lb.

Front-side Hall element50fdetects a first position with a movement (a swing) in first direction (fore-and-aft direction) X by detecting a magnetic force of front-side permanent magnet piece282fopposite thereto. Left-side Hall element50ldetects a second position with a movement (a swing) in second direction (left-and-right direction) Y by detecting a magnetic force of left-side permanent magnet piece282lopposite thereto.

Referring toFIGS. 5 through 7, the description will proceed to a relationship between a related magnetic circuit and Hall elements for use in a related lens driving device in order to facilitate the understanding of lens driving device10according to the exemplary embodiment of the present invention. The relationship between the illustrated related magnetic circuit and the Hall elements is similar in structure (relationship) to that illustrated in the above-mentioned PTL 17.FIG. 5is a perspective view showing the relationship between the related magnetic circuit and the Hall elements;FIG. 6is a vertical cross sectional view showing the relationship between the related magnetic circuit and the Hall elements, andFIG. 7is a vertical cross sectional view shoring the relationship between the related magnetic circuit and the Hall elements in a case of displacing AF unit20in fore-and-aft direction X.

A difference between the related magnetic circuit and the magnetic circuit used in lens driving device10according to this exemplary embodiment is that any of four image stabilizer coil portions18f′,18b′,18l′, and18r′ constituting image stabilizer coil18′ in the related magnetic circuit comprises no two loop ports. That is, in the conventional magnetic circuit, each of four image stabilizer coil portions18f,18b′,18l′, and18r′ comprises only one loop part.

As described above, four permanent magnet pieces282f,282b,282l, and282rhave the inner side polarized (magnetized) to the north pole and the outer side polarized (magnetized) to the south pole. Arrows B depicted inFIG. 5indicate directions of magnetic fluxes generated by the permanent magnet pieces.

Referring now toFIG. 5, the description will be made as regards operation in a case of position adjusting lens holder24(lens barrel) in the direction of optical axis O by using the related magnetic circuit.

By way of illustration, it will be assumed that the AF current is flowed through focusing coil26counterclockwise. In this event, according to Fleming's right-hand rule, focusing coil26is acted upon by an electromagnetic force upwards. As a result, it is possible to move lens holder24(lens barrel) in the direction of optical axis O upwards.

Conversely, by flowing the AF current through focusing coil26clockwise, it is possible to move lens holder24(lens barrel) in the direction of optical axis O downwards.

Referring now toFIGS. 5 to 7, the description will be made as regards operation in a case of moving the auto-focusing lens driving portion (AF unit)20as a whole in first direction (fore-and-aft direction) X or second direction (left-and-right direction) Y by using the conventional magnetic circuit.

First, the description will be made as regards operation in a case of moving auto-focusing lens driving portion (AF unit)20as a whole in first direction (the fore-and-aft direction) X backwards. In this event, as shown inFIG. 5, a first image stabilizing (IS) current flows through front-side image stabilizer coil portion18fcounterclockwise as depicted at arrow IIS1and a second image stabilizing (IS) current flows through back-side image stabilizer coil portion18b′ clockwise as depicted at arrow IIS2.

In this event, according to Fleming's right-hand rule, front-side image stabilizer coil portion18f′ is acted upon by an electromagnetic force forwards and back-side image stabilizer coil portion18b′ is also acted upon by an electromagnetic force forwards. However, inasmuch as there image stabilizer coil portions18fand18r′ are fixed to base14, as reaction, auto-focusing lens driving portion (the AF unit)20as a whole is acted upon by an electromagnetic force backwards, as depicted at arrows FIS1and FIS2inFIG. 6. As a result, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole backwards.

Conversely, by flowing the first IS current through front-side image stabilizer coil portion18f′ clockwise and by flowing the second IS current through back-side image stabilizer coil portion18b′ counterclockwise, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole forwards.

On the other hand, by flowing a third IS current through left-side image stabilizer coil portion18l′ counterclockwise and by flowing a fourth IS current through right-side image stabilizer coil portion18r′ clockwise, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole rightwards.

In addition, by flowing the third IS current through left-side image stabilizer coil portion18l′ clockwise and by flowing the fourth IS current through right-side image stabilizer coil portion18r′ counterclockwise, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole leftwards.

In the manner which is described above, it is possible to stabilize blurry images.

Referring now toFIGS. 8 through 10in addition toFIGS. 5 through 7, the description will proceed to problems in the conventional lens driving device using the conventional magnetic circuit in more details.

The description will be made as taking a case as an example where the first IS current flows through front-side image stabilizer coil portion18fcounterclockwise as depicted at arrow IIS1and the second IS current flows through back-side image stabilizer coil portion18b′ clockwise as depicted at arrow IIS2, as shown inFIG. 5, in order to move auto-focusing lens driving portion (AF unit)20as a whole backwards in the manner which is described above.

In this event, as shown inFIG. 7, it is understood that magnetic field BI1produced by first IS current IIS1flowing through front-side image stabilizer coil portion18f′ and magnetic field B produced by front-side permanent magnet piece282fare in phase. It will be assumed that magnetic flux density of magnetic field B is indicated by a and magnetic flux density of magnetic field BI1is indicated by b. Accordingly, front-side Hall element50fdetects total magnetic flux density (a+b) obtained by summing magnetic flux density a of magnetic field B and magnetic flux density b of magnetic field BI1.

It is herein noted that it is necessary that magnetic flux density a of the magnetic field B and total magnetic flux density (a+b) are in phase in order to detect a position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f.

FIG. 8is a view showing a frequency response of front-side Hall element50fin the related magnetic circuit. InFIG. 8, the horizontal axis represents a frequency (Frequency) (Hz), the left-hand vertical axis represents a gain (Gain) (dB), and the right-hand vertical axis represents a phase (Phase) (deg). In addition, inFIG. 8, a solid line indicates a gain characteristic and an alternate long and short dashed line indicate a phase characteristic.

As is apparent fromFIG. 8, the frequency response of font-side Hall element50fis divided into a region I, a region II, and a region III. The region I is a region having a band not higher than a primary resonance frequency of the actuator and having low frequencies. The region II is a region having a band not lower than the primary resonance frequency of the actuator and having middle frequencies. The region III is a region having a band not lower than the primary resonance frequency of the actuator and having high frequencies.

FIG. 9is a view showing relationships between phases and magnitudes among magnetic flux density a of magnetic field B generated by front-side permanent magnet piece282f, magnetic flux density b of magnetic field BI1generated by first IS current IIS1flowing through front-side image stabilizer coil18f, and total magnetic flux density (a+b) detected by front-side Hall element50fin region I, region II, and region III, respectively.FIG. 10is a view tabulated for the relationships ofFIG. 9.

It is understood fromFIGS. 9 and 10as follows.

In the band not higher than the primary resonance frequency of region I, a magnitude |a| of magnetic flux density a of magnetic field B is larger than a magnitude |b| of magnetic flux density b of magnetic field BI1(|a|>|b|), and magnetic flux density a of magnetic field B, magnetic flux density b of magnetic field BI1, and total magnetic flux density (a+b) are in phase. Accordingly, in region I, it is possible to detect the position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f.

On the other hand, in a band not lower than primary resonance frequency, phase is opposite because movement of front-side permanent magnet piece282fshifts with respect to a phase of first IS current IIS1, flowing through front-side image stabilizer coil18f′ by 180 degrees.

In the band not lower than the primary resonance frequency of region II, magnetic flux density a of magnetic field B and total magnetic flux density (a+b) are in phase because the magnitude |a| of magnetic flux density a of magnetic field B is larger than a magnitude |b| of magnetic flux density b of magnetic field BI1(|a|>|b|). Accordingly, in region II, it is possible to detect the position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f.

However, in the band not lower than the primary resonance frequency of region III, it is understood that the magnitude of magnetic flux density a of the magnetic field B is smaller than a magnitude |b| of magnetic flux density b of the magnetic field BI1(|a|<|b|). Therefore, magnetic flux density a of magnetic field B and total magnetic flux density (a+b) are opposite phase. As a result, in region III, it is impossible to detect the position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f. That is, an output of Hall element has resonance.

Accordingly, when the Hall element is disposed between (in) the loop part of the coil, it is understood that it is impossible to detect the position of auto-focusing lens driving portion (AF unit)20in region III which is not lower than the primary resonance frequency. In other words, Hall elements50fand50lare subjected to adverse effect caused by the magnetic fields generated by the currents flowing through image stabilizer coils18fand18l′, respectively.

Referring now toFIGS. 11 through 14, the description will proceed to a relationship between the magnetic circuit according to this exemplary embodiment and the Hall elements for use in lens driving device10according to the first exemplary embodiment of this invention.FIG. 11is a perspective view showing the relationship between the magnetic circuit according to this exemplary embodiment and the Hall elements,FIG. 12is a vertical cross sectional view showing the relationship between the magnetic circuit according to this exemplary embodiment and the Hall elements,FIG. 13is a vertical cross sectional view shoring the relationship between the magnetic circuit according to this exemplary embodiment and the Hall elements in a case of displacing AF unit20in fore-and-aft direction X, andFIG. 14is a cross sectional view taken on line XIV-XIV ofFIG. 13.

As described above, four permanent magnet pieces282f,282b,282l, and282rhave the inner side polarized (magnetized) to the north pole and the outer side polarized (magnetized) to the south pole. Arrows B depicted inFIG. 11indicate directions of magnetic fluxes generated by the permanent magnet pieces.

Referring now toFIG. 11, the description will be made as regards operation in a case of position adjusting lens holder24(the lens barrel) in the direction of optical axis O by using the magnetic circuit according to this exemplary embodiment.

By way of illustration, it will be assumed that the AF current is flowed through focusing coil26counterclockwise. In this event, according to Fleming's right-hand rule, focusing coil26is acted upon by an electromagnetic force upwards. As a result, it is possible to move lens holder24(lens barrel) in the direction of optical axis O upwards.

Conversely, by flowing the AF current through focusing coil26clockwise, it is possible to move lens holder24(lens barrel) in the direction of optical axis O downwards.

Referring now toFIGS. 11 to 14, the description will be made as regards operation in a case of moving auto-focusing lens driving portion (AF unit)20as a whole in first direction (fore-and-aft direction) X or second direction (left-and-right direction) Y by using the magnetic circuit according to this exemplary embodiment.

First, the description will be made as regards operation in a case of moving auto-focusing lens driving portion (AF unit)20as a whole in first direction (the fore-and-aft direction) X backwards. In this event, as shown inFIG. 11, a first image stabilizing (IS) current flows through each of two coil parts18fland18frof front-side image stabilizer coil portion18fcounterclockwise as depicted at arrow IIS1and a second image stabilizing (IS) current flows through back-side image stabilizer coil portion18bclockwise as depicted at arrow IIS2.

In this event, according to Fleming's right-hand rule, front-side image stabilizer coil portion18fis acted upon by an electromagnetic force forwards and back-side image stabilizer coil portion18bis also acted upon by an electromagnetic force forwards. However, inasmuch as there image stabilizer coil portions18fand18rare fixed to base14, as reaction, auto-focusing lens driving portion (AF unit)20as a whole is acted upon by an electromagnetic force backwards, as depicted at arrows FIS1and FIS2inFIG. 12. As a result, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole backwards.

Conversely, by flowing the first IS current through each of two coil parts18fland18frof front-side image stabilizer coil portion18fclockwise and by flowing the second IS current through back-side image stabilizer coil portion18bcounterclockwise, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole forwards.

On the other hand, by flowing a third IS current through each of two coil parts18lfand18lbof left-side image stabilizer coil portion18lcounterclockwise and by flowing a fourth IS current through right-side image stabilizer coil portion18rclockwise, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole rightwards.

In addition, by flowing the third IS current through each of two coil parts18lfand18lrof left-side image stabilizer coil portion18lclockwise and by flowing the fourth IS current through right-side image stabilizer coil portion18rcounterclockwise, it is possible to move auto-focusing lens driving portion (AF unit)20as a whole leftwards.

In the manner which is described above, it is possible to stabilize blurry images in the camera.

Referring now toFIGS. 15 through 17in addition toFIGS. 11 through 14, the description will proceed to advantages in lens driving device10using the magnetic circuit according to this exemplary embodiment in more details.

The description will be made as taking a case as an example where the first IS current flows through each of two coil parts18fland18frof front-side image stabilizer coil portion18fcounterclockwise as depicted at arrow IIS1and the second IS current flows through back-side image stabilizer coil portion18bclockwise as depicted at arrow IIS2, as shown inFIG. 11, in order to move auto-focusing lens driving portion (AF unit)20as a whole backwards in the manner which is described above.

In this event, as shown inFIGS. 13 and 14, it is understood that a magnetic field BI1produced by first IS current IIS1flowing through front-side image stabilizer coil portion18fand magnetic field B produced by front-side permanent magnet piece282fare opposite phase. It will be assumed that magnetic flux density of magnetic field B is indicated by a and magnetic flux density of magnetic field BI1is indicated by b. Accordingly, it is understood that front-side Hall element50fdetects total magnetic flux density (a+b) obtained by summing magnetic flux density a of magnetic field B and magnetic flux density b of magnetic field BI1.

It is herein noted that it is necessary that magnetic flux density a of magnetic field B and total magnetic flux density (a+b) are in phase in order to detect a position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f.

FIG. 15is a view showing a frequency response of front-side Hall element50fin the magnetic circuit according to this exemplary embodiment. InFIG. 15, the horizontal axis represents a frequency (Frequency) (Hz), the left-hand vertical axis represents a gain (Gain) (dB), and the right-hand vertical axis represents a phase (Phase) (deg). In addition, inFIG. 15, a solid line indicates a gain characteristic and an alternate long and short dashed line indicate a phase characteristic.

As is apparent fromFIG. 15, the frequency response of font-side Hall element50fis divided into region I, region II, and region III. Region I is a region having a band not higher than a primary resonance frequency of the actuator and having low frequencies. Region II is a region having a band not lower than the primary resonance frequency of the actuator and having middle frequencies. Region III is a region having a band not lower than the primary resonance frequency of the actuator and having high frequencies.

FIG. 16is a view showing relationships between phases and magnitudes among magnetic flux density a of magnetic field B generated by front-side permanent magnet piece282f, magnetic flux density b of magnetic field BI1generated by first IS current IIS1flowing through front-side image stabilizer coil18f, and total magnetic flux density (a+b) detected by front-side Hall element50fin region I, region II, and region III.FIG. 17is a view tabulated for the relationships ofFIG. 16.

It is understood fromFIGS. 16 and 17as follows.

In the band not higher than the primary resonance frequency of region I, a magnitude |a| of magnetic flux density a of magnetic field B is larger than a magnitude |b| of magnetic flux density b of magnetic field BI1(|a|>|b|), and magnetic flux density a of magnetic field B and total magnetic flux density (a+b) are in phase although magnetic flux density a of magnetic field B and magnetic flux density b of magnetic field BI1are opposite phase. Accordingly, in region I, it is possible to detect the position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f.

On the other hand, in a band not lower than primary resonance frequency, movement of front-side permanent magnet piece282fis in phase with first IS current IIS1flowing through front-side image stabilizer coil portion18f.

In the band not lower than the primary resonance frequency of region II, magnetic flux density a of magnetic field B and total magnetic flux density (a+b) are in phase because the magnitude |a| of magnetic flux density a of magnetic field B is larger than a magnitude |b| of magnetic flux density b of magnetic field BI1(|a|>|b|). Accordingly, in region II, it is possible to detect the position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f.

On the other hand, in the band not lower than the primary resonance frequency of region III, the magnitude |a| of magnetic flux density a of magnetic field B is smaller than a magnitude |b| of magnetic flux density b of magnetic field BI1(|a|<|b|). However, inasmuch as the magnetic flux density a of the magnetic field B and total magnetic flux density (a+b) of the magnetic field B are in phase, the magnetic flux density a of the magnetic field B and the total magnetic flux density (a+b) are also in phase. As a result, in also region III, it is possible to detect the position of auto-focusing lens driving portion (AF unit)20by means of front-side Hall element50f. That is, resonance does not occur in an output of Hall element.

Accordingly, when the Hall element is disposed between the two loop parts of the coil, it is understood that it is possible to detect the position of auto-focusing lens driving portion (AF unit)20in all of frequency ranges. In other words, Hall elements50fand50lcan avoid to subject to adverse effect caused by the magnetic fields generated by the currents flowing through image stabilizer coil portions18fand18l, respectively.

FIG. 18is a cross sectional view showing a relationship of a placement among one permanent magnet piece282of permanent magnet28, focusing coil26disposed around it, and image stabilizer coil18in the magnetic circuit.

It is understood that the height of permanent magnet piece282is higher than the height of focusing coil26. It is therefore possible to make a stoke larger in a case of position adjusting lens holder24(lens barrel) in the direction of optical axis O.

FIG. 19toFIG. 23illustrate a first modified example of the first exemplary embodiment.

FIG. 19toFIG. 23illustrate a configuration in which yoke25is newly added to the magnetic circuit constituted by permanent magnet28, focusing coil26and image stabilizer coil18that is shown inFIG. 5.

Yoke25has coupling portion252integrally disposed in a substantially rectangular annular ring shape on a side facing the top surface (third surface) of each permanent magnet piece282, and four vertical extension portions254that extend vertically downward in parallel with optical axis O at the inner sides of the four corners of coupling portion252. That is, the yoke (25) has first yoke portions (vertical extension portions254) that are disposed facing the first surfaces (inner wall surfaces282a) of a plurality of magnets (permanent magnet pieces282) in a manner in which a first coil (focusing coil26) is sandwiched therebetween, and second yoke portions (coupling portions252) that are disposed facing the third surface (top surface) of the plurality of magnets (permanent magnet pieces282).

Yoke25is mounted to magnet holder30, for example, by inserting protrusions (not shown) formed on an inner surface side at an upper portion of magnet holder30into holes (not shown) formed in coupling portion252and performing thermal welding. Vertical extension portions254are inserted into spaces formed between tubular portion240of lens holder24and focusing coil26.

The four permanent magnet pieces282are fixed apart from each other in magnet holder30, and gaps29are formed between the respective permanent magnet pieces282. Vertical extension portions254of yoke25each have outer wall surface254a. That is, the first yoke portions (vertical extension portions254) have wall surfaces (outer wall surfaces254a) that face the first surfaces (inner wall surfaces282a) of the respective adjacent magnets (permanent magnet pieces282) and separation parts (gaps29) between the adjacent magnets (permanent magnet pieces282), and are coupled by means of the second yoke portions (coupling portions252).

In this case, since the four permanent magnet pieces282are disposed so as to each form one side of a square, the number of first yoke portions (vertical extension portions254) disposed facing gaps29between the four permanent magnet pieces282is also four.

The respective outer wall surfaces254aof vertical extension portions254are disposed at positions facing one part of inner wall282athat is parallel with optical axis O of the respective permanent magnet pieces282as well as the corresponding gap29. Focusing coil26is disposed between one part of inner wall282aof the respective permanent magnet pieces282and gaps29, and outer wall surfaces254aof vertical extension portions254.

Note that, although yoke25is mounted to magnet holder30and is separated from permanent magnet pieces282(seeFIG. 21), a configuration may also be adopted in which yoke25and each permanent magnet piece282are directly contacting each other.

By constructing the magnetic circuit in the manner described above, a configuration can be adopted in which a magnetic circuit is added between permanent magnet28and focusing coil26of the first exemplary embodiment, and in which a magnetic circuit is newly formed between vertical extension portions254of yoke25and focusing coil26. That is, together with a plurality of magnets (permanent magnet pieces282), yoke (25) forms a magnetic circuit that generates a magnetic flux that crosses the first coil (focusing coil26). In this case, a magnetic circuit in which a magnetic flux is emitted from the north poles (inner wall surfaces282a) of permanent magnet pieces282and crosses focusing coil26and efficiently returns to the south poles of permanent magnet pieces282through yoke25is formed by permanent magnet pieces282and yoke25. Since the magnetic flux crosses the four corners of focusing coil26, a propulsive force that arises when a current flows through focusing coil26is larger than in the first exemplary embodiment.

That is, according to the first modified example, the capacity of permanent magnet28and focusing coil26can be made less than in the first exemplary embodiment. Since small components can be applied as permanent magnet28and focusing coil26, the total weight of auto-focusing lens driving portion20does not become heavier as a result of newly adding yoke25. Rather, in the case of securing the same driving force for auto-focusing lens driving portion20as in the first exemplary embodiment, it is possible to reduce the total weight of auto-focusing lens driving portion20. Accordingly, by applying yoke25, it is also possible to reduce power consumption when driving auto-focusing lens driving portion20to move up and down in parallel with optical axis O.

In addition, permanent magnet piece282and image stabilizer coil18are disposed so that edges of permanent magnet piece282in the radial direction are laid in a coil sectional width of image stabilizer coil18in the radial direction. It is therefore possible to heighten sensitivity of a driving force for moving auto-focusing lens driving portion (AF unit)20as a whole in a direction orthogonal to optical axis O.

Incidentally, there is a concern that four suspension wires16may be fracture in lens driving device10having such a structure because four suspension wires16are subjected to force in a direction to expand caused by a drop impact or the like. However, lens driving device10according to this exemplary embodiment comprises a fracture preventing member for preventing four suspension wires16from fracturing in the manner which will be presently described.

Referring toFIGS. 24 and 25, the description will proceed to the fracture preventing member according to this exemplary embodiment in detail.FIG. 24is a partial perspective view enlargedly showing a part fixing the other end of suspension wire16to upper leaf spring32, andFIG. 25is a partial cross sectional view of the fixed part.

In the manner which is described above, upper leaf spring32comprises four arc-shaped extending portions328(only one arc-shaped extending portion328is shown inFIG. 24) for extending at the four corners of upper outer end portion324in the radial direction outwards. Four arc-shaped extending portions328have, at tip portions thereof, four wire fixing holes328a(see,FIG. 3) in which the other ends of four suspension wires16are inserted (fitted), respectively. The other ends of four suspension wires16are inserted in four wire fixing holes328ato be fixed by means of solder60or adhesive agent (not shown).

Accordingly, four arc-shaped extending portions328serve as a wire fixing portion for fixing the other ends of four suspension wires16.

In lens driving device10having such a structure, although auto-focusing lens driving portion (AF unit)20is subjected to the force in the direction to apart from base14due to a drop impact or the like, auto-focusing lens driving portion (AF unit)20moves upward with four arc-shaped extending portions328elastically deformed in a state where the other ends of four suspension wires16are fixed to four arc-shaped extending portions328of upper leaf spring32.

As a result, it is possible to prevent four suspension wires16from fracturing. Accordingly, four arc-shaped extending portions328act as the facture preventing member for preventing four suspension wires16from fracturing.

On the other hand, as shown inFIG. 24, magnet holder30comprises four upper stoppers308(only one upper stopper308is shown inFIG. 24) which project at the four corners of upper ring-shaped end portion304upwards. Each upper stopper308projects from opening32aformed in upper leaf spring32between upper outer end portion324and each arc-shaped extending portion328.

In other words, four upper stoppers308project from magnet holder30toward an inner wall surface of shielding cover42.

By four upper stoppers308, movement of auto-focusing lens driving portion (AF unit)20upwards is limited. In other words, when auto-focusing lens driving portion (AF unit)20moves upwards, four upper stoppers308of magnet holder30hits to the inner wall surface of upper end portion424of shielding cover42although four arc-shaped extending portions328become elastically deformed before four arc-shaped extending portions328buckle or before four suspension wires16are subjected to a fracturing force.

That is, four upper stoppers308serve as a fracture prevention supporting member for supporting prevention of fracture in four suspension wires16.

As shown inFIG. 2, there is little clearance (gap) between fixed members (14,40,18,44) and auto-focusing lens driving portion (AF unit)20. Accordingly, although auto-focusing lens driving portion (AF unit)20is subjected to a force in a direction to get near base14due to a drop impact or the like, four suspension wires16do not buckle because auto-focusing lens driving portion (AF unit)20immediately hits to an upper surface of fixed members (14,40,18,44).

Referring toFIG. 26in addition toFIGS. 2 to 4, the description will proceed to flexible printed circuit (FPC)44disposed between base14and coil board40and a method of mounting it.FIG. 26is a perspective view showing an assembly of coil board40and flexible printed circuit (FPC)44seen from a rear side.

As shown inFIG. 3, base14has four positioning protrusions142which project upwards on diagonal lines in vicinity of circular opening14ain the radial direction outwards. On the other hand, as shown inFIG. 4, coil board40has four positioning hole portions40bin which four positioning protrusions142are charged, respectively. As shown inFIG. 26, flexible printed circuit (FPC)44also has four positioning hole portions44aat positions corresponding to four positioning hole portions40b. Accordingly, four positioning protrusions142of base14are charged in four positioning hole portions40bof coil board40via four positioning hole portions44aof flexible printed circuit (FPC)44.

As shown inFIG. 26, flexible printed circuit (FPC)44has a rear surface on which two Hall elements50fand50lare mounted. On the other hand, as shown inFIG. 2, base14has holes14bin which two Hall elements50fand50lare fitted.

As shown inFIG. 4, on coil board40, six lands18afor supplying electric currents to four image stabilizer coil portions18f,18b,18l, and18rare formed along circular opening40abored at a central portion thereof. On the other hand, as shown inFIG. 26, on flexible printed circuit (FPC)44, six notch portions44bare formed at positions corresponding to six lands18a. Accordingly, by mounting solder pastes on six notch portions44band by carrying out solder reflow, it is possible to electrically connect internal wiring (not shown) of flexible printed circuit (FPC)44with six lands18aof coil board40.

As shown inFIG. 26, flexible printed circuit (FPC)44has a rear surface on which control portion46is mounted. Control portion46controls the current flowing through focusing coil16and controls the currents flowing through four image stabilizer coil portions18f,18b,18l, and18rso as to compensate wobbling detected based on two directional gyros (not shown) on the basis of position detected signals detected by two Hall elements50fand50l.

Referring toFIGS. 27 and 28, the description will proceed to a method for feeding to focusing coil26.FIG. 27is a plan view showing a state where shielding cover42is omitted from lens driving device10.FIG. 28is a partial enlarged perspective view enlargedly showing a tied-up part of an end portion of a wire composed of focusing coil26as shown inFIG. 27.

As shown inFIG. 27, lens holder24has, at an upper end thereof, first and second projecting portions241and242which project in a direction (outwards in the radial direction) to apart from each other in left-and-right direction Y. In the example being illustrated, first projecting portion241is also called a right-side projecting portion because it projects to right side while second projecting portion242is also called a left-side projecting portion because it projects to left side.

On the other hand, the wire composed of focusing coil26has first and second end portions261and262. As shown inFIG. 28, first end portion261of the wire of focusing coil26is tied up to first projecting portion (right-side projecting portion)241of lens holder24. Similarly, second end portion262of the wire of focusing coil26is tied up to second projecting portion (left-side projecting portion)242of lens holder24. Accordingly, first and second end portions261and262are also called first and second tied-up parts, respectively.

On the other hand, as shown inFIG. 27, first leaf spring (upper leaf spring)32comprises first and second leaf spring pieces32-1and32-2which are electrically insulated from each other. First and second leaf spring pieces32-1and32-2have rotational symmetry shapes with respect to optical axis O of the lens as a center. First leaf spring piece32-1is disposed, at the first end (the upper end) of magnet holder30, substantially back side and right side while second leaf spring piece32-2is disposed, at the first end (the upper end) of magnet holder30, substantially front side and left side.

Upper inner end portion322of first leaf spring piece32-1disposed at the right side has first U-shaped terminal portion322-1projecting rightwards (outwards in the radial direction) at a position corresponding to first projecting portion (right-side projecting portion)241of lens holder24. Likewise, upper inner end portion322of second leaf spring piece32-2disposed at the left-side has second U-shaped terminal portion322-2projecting leftwards (outwards in the radial direction) at a position corresponding to second projecting portion (left-side projecting portion)242of lens holder24. First U-shaped terminal portion322-1is also called a right-side U-shaped terminal portion while second U-shaped terminal portion322-2is also called a left-side U-shaped terminal portion.

In addition, in the manner which is described above, among four suspension wires16, the other ends of two suspension wires16(right-back and left-front in the example ofFIG. 27) are connected to arc-shaped extending portions328through wire fixing holes328aby means of solder60. The other ends of remaining two suspension wires16(left-back and right-front in the example ofFIG. 27) are fixed to arc-shaped extending portions328through wire fixing holes328aby means of adhesive agent62.

Accordingly, suspension wire16of the right-back is electrically connected to first end portion (first tied-up part)261of focusing coil26via first leaf spring piece32-1of first leaf spring (upper leaf spring)32, and first U-shaped terminal portion (right-side U-shaped terminal portion)322-1. Similarly, suspension wire16of the left-front is electrically connected to second end portion (second tied-up part)262of focusing coil26via second leaf spring piece32-2of first leaf spring (upper leaf spring)32, and second U-shaped terminal portion (left-side U-shaped terminal portion)322-2.

In the manner which is described above, feeding to focusing coil26is carried out from suspension wires16via first leaf spring32.

In this connection, yoke25that is described in the first modified example is interposed between first leaf spring32and lens holder24. Therefore, in a case where lens holder24and first leaf spring32are connected as described above, yoke25that is made from a single member as described in the first modified example cannot be mounted.

Further, in a case in which a specific part of lens holder24interferes with yoke25accompanying upward movement of lens holder24also, a problem will arise if yoke25that is made from a single member is applied. For example, even in a case where lens holder24and first leaf spring32are not connected, if lens holder24includes first projecting portion241and second projecting portion242for tying end portions261and262of focusing coil26, there is a risk that first projecting portion241and second projecting portion242will collide with yoke25accompanying upward movement of lens holder24.

In such a case, it is preferable to construct yoke25with a plurality of members as shown inFIG. 40toFIG. 43.FIG. 40is a perspective view illustrating an example in a case where yoke25is constituted by a plurality of members.FIG. 41is an exploded perspective view illustrating an example in a case where yoke25is constituted by a plurality of members.FIG. 42is a vertical cross sectional view at a portion at which yoke25is present.FIG. 43is a vertical cross sectional view at a portion at which yoke25is not present (separation part).

In the example shown inFIG. 40toFIG. 43, yoke25according to the first modified example (seeFIGS. 19 to 23) is constituted by a plurality of members (yokes25A and25B). Further, predetermined parts (parts with respect to which there is a risk of interfering with yoke25, for example, first projecting portion241and second projecting portion242) of lens holder24are positioned at a separation part between yokes25A and25B.

In a case where yoke25is constituted by a single member, as in the first modified example, lens holder24can only move upward as far as a position that is immediately before a position at which lens holder24would collide with yoke25. Therefore, to secure the moving distance, it is necessary to increase the size of lens driving device10in the optical axis direction. Further, in a case where it is necessary to electrically connect lens holder24and first leaf spring32, it is not even possible to mount yoke25.

In contrast, in a case where yoke25is constituted by a plurality of members (yokes25A and25B), since interference with yoke25when lens holder24moves upward can be avoided, the height of lens driving device10can be lowered. Further, in a case where lens holder24and first leaf spring32are electrically connected also (seeFIGS. 27 and 28), yoke25can be mounted without any problem.

Next, the description will proceed to a method of assembling lens driving device10.

On the other hand, an assembly consisting of coil board40and flexible printed circuit (FPC)44, as shown inFIG. 26, is manufactured by the above-mentioned solder reflow. The assembly is mounted on base14to which one ends of four suspension wires16are fixed.

Subsequently, above-mentioned auto-focusing lens driving portion (AF unit)20is mounted on base14via the above-mentioned assembly and the other ends of four suspension wires16are fixed to arc-shaped extending portions328via wire fixing holes328aby means of solder60or adhesive agent62.

First and second U-shaped terminal portions322-1and322-2of first leaf spring (the upper leaf spring)32are connected to first and second end portions261and262of focusing coil26.

Lastly, shielding cover42is put so as to cover auto-focusing lens driving portion (AF unit)20and a lower end of shielding cover42is fixed to base14.

As such a manner, it is possible to easily assemble lens driving device10.

Lens driving device10assembled in such a manner has a size of 11 mm×11 mm×4.2 mm.

A method of attaching damper material65for suppressing undesired resonance in the direction of optical axis O of auto-focusing lens driving portion (AF unit)20as well as placement positions of damper material65in lens driving device10will now be described with reference toFIG. 29toFIG. 31.

FIG. 29is a partial front view of lens driving device10in a state where shielding cover42is omitted therefrom.FIG. 30is a partial perspective view of lens driving device10illustrated inFIG. 29seen from a diagonally upward direction.FIG. 31is a plan view showing placement positions of damper material65in lens driving device10in a state in which shielding cover42is omitted and one part of upper leaf spring (first leaf spring)32is omitted.

Damper material65is disposed between four lower protrusions306aof magnet holder30and coil board40. Outer tubular portion302of magnet holder30has four guide grooves302athat guide a dispenser (not shown) for applying damper material65. It is thereby possible to easily apply damper material65in gaps between the four lower protrusions306aand coil board40using the dispenser. As described in the foregoing, the gaps between the four lower protrusions306aand coil board40are narrower than gaps in another region. Therefore, when the dispenser that is inserted along guide grooves302ais used to apply damper material65in the vicinity of four lower protrusions306a, the applied damper material65naturally accumulates in the gaps between the four lower protrusions306aand coil board40by the effect of surface tension.

In the example being illustrated, as damper material65, an ultraviolet curing silicone gel having a viscosity of 90 Pa·s is used that is manufactured by ThreeBond Co. Ltd. and sold under the product name TB3168E.

Accordingly, after applying damper material65into gaps between the four lower protrusions306aof magnet holder30and coil board40in the manner described above, damper material65is cured by irradiating damper material65with ultraviolet light.

Frequency responses in a case where damper material65is not provided (conventional example) and a case where damper material65is provided (first exemplary embodiment) will now be described referring toFIG. 32andFIG. 33.FIG. 32illustrates a frequency response in optical axis O direction of auto-focusing lens driving portion (AF unit)20of a conventional lens driving device in a case where damper material65is not provided.FIG. 33illustrates a frequency response in optical axis O direction of auto-focusing lens driving portion (AF unit)20of lens driving device10according to the first exemplary embodiment of the present invention in a case where damper material65is provided. In each ofFIG. 32andFIG. 33, the abscissa axis represents a frequency [Hz] while the ordinate axis represents a gain [dB].

As is apparent fromFIG. 32, in the conventional lens driving device without damper material65, resonance (a high-order resonance mode) is generated in optical axis O direction at frequencies of about 400 Hz.

In contrast, as is apparent fromFIG. 33, in lens driving device10according to the first exemplary embodiment that includes damper material65, generation of such resonance (the high-order resonance mode) in optical axis O direction is suppressed.

Accordingly, lens driving device10according to the first exemplary embodiment enables control operations that realize stable image stabilization.

Further, since damper material65is disposed so as to support auto-focusing lens driving portion (AF unit)20that is a movable portion on the image stabilizing side, damper material65also has an effect of relieving the impact on auto-focusing lens driving portion (AF unit)20if lens driving device10is dropped.

Above-mentioned lens driving device10according to the first exemplary embodiment of the present invention has effects which will be presently described.

First, it is possible for two Hall elements50fand50lto avoid a detrimental effect caused by the magnetic field generated by the current flowing through specific two image stabilizer coil portions18fand18lbecause two Hall elements50fand50lare disposed on base14at the positions where specific two image stabilizer coil portions18fand18lare separated into respective two coil parts18fl,18frand18lf,18lb.

Secondly, it is possible to prevent four suspension wires16from fracturing and to heighten impact resistance of lens driving device10because the lens driving device comprises fracture preventing member328.

Thirdly, it is possible to electrically connect the inner wiring of flexible printed circuit (FPC)44with the plurality of lands18aof coil board40by means of solder reflow because notch portions44bare formed to flexible printed circuit (FPC)44at the positions corresponding to the plurality of lands18aformed on coil board40.

Fourthly, it is possible to make the stoke in the case of position adjusting lens holder24(lens barrel) in the direction of optical axis O larger because the height of focusing coil26is lower than the height of permanent magnet piece282.

Fifthly, it is possible to enhance sensitivity of the driving force for moving auto-focusing lens driving portion (AF unit)20as a whole in the direction orthogonal to optical axis O because permanent magnet pieces282and image stabilizer coil portions18are disposed so that the edges of permanent magnet pieces282in the radial direction are laid in the coil sectional width of image stabilizer coil portions18in the radial direction.

Sixthly, since damper material65is disposed between the fixed member (14,40,18, and44) and auto-focusing lens driving portion20, undesired resonance can be suppressed and stable operations can be performed.

Seventhly, since damper material65is disposed between the fixed member (14,40,18, and44) and auto-focusing lens driving portion20, the proof stress at a time that lens driving device10is dropped can be improved.

Next, modified examples of lens driving device10according to the first exemplary embodiment will be described.

While damper material65is provided at four places as shown inFIG. 31in lens driving device10according to the first exemplary embodiment described above, the number of places at which damper material65is provided and the placement positions are not important for the present invention. The important point is that damper material65is disposed between movable portion (auto-focusing lens driving portion)20and the fixed member (14,40,18, and44).

For example, a configuration may be adopted in which damper material65is provided at only one place, as in lens driving device10according to a second modified example as illustrated inFIG. 34. Further, a configuration may be adopted in which damper material65is provided at three places, as in lens driving device10according to a third modified example as illustrated inFIG. 35. In addition, a configuration may be adopted in which damper material65is provided at eight places, as in lens driving device10according to a fourth modified example as illustrated inFIG. 36.

By providing damper material65at one or a plurality of places in this manner, effects similar to those of the above-mentioned first exemplary embodiment are obtained.

Further, in lens driving device10according to the first exemplary embodiment described above, as shown inFIG. 29andFIG. 25, guide grooves302aare faulted in magnet holder30to facilitate application of damper material65. However, a configuration may also be adopted in which guide groove302ais not provided, as in lens driving device10according to a fifth modified example as shown inFIG. 37.

Further, although the ultraviolet curing silicone gel is used as damper material65in lens driving device10according to the first exemplary embodiment described above, the material of damper material65is not limited thereto, and any material that has a damper effect may be used.

Second Exemplary Embodiment

Referring toFIGS. 38 and 39, the description will proceed to lens driving device10A according to a second exemplary embodiment of the present invention.FIG. 38is a vertical cross sectional view of lens driving device10A.FIG. 39is an exploded perspective view of lens driving device10A.

Herein, in the manner shown inFIGS. 38 and 39, an orthogonal coordinate system (X, Y, Z) is used. In a state illustrated inFIGS. 38 and 39, in the orthogonal coordinate system (X, Y, X), an X-axis direction is a fore-and-aft direction (a depth direction), a Y-axis direction is a left-and-right direction (a width direction), and a Z-axis direction is an up-and-down direction (height direction). In addition, in the example being illustrated inFIGS. 38 and 39, up-and-down direction Z is a direction of optical axis O of a lens. In the second exemplary embodiment, the X-axis direction (the fore-and-aft direction) is called a first direction while the Y-axis direction (the left-and-right direction) is called in a second direction.

However, in an actual use situation, the direction of optical axis O, namely, the Z-axis direction becomes a fore-and-aft direction. In other words, an upper direction of the Z-axis becomes a front direction while a lower direction of the Z-axis becomes a rear direction.

Illustrated lens driving device10A includes auto-focusing lens driving portion20A and an image stabilizer portion for stabilizing blurry images produced in auto-focusing lens driving portion20A on picking up a static image using a miniature camera for a mobile phone and is a device which can pick up the image free from image blurred.

Illustrated lens driving device10A has a structure in which lens driving device10according to the above-mentioned first exemplary embodiment is substantially turned upside down. Accordingly, it is suitable to change “upper” into “lower” and to change “lower” into “upper”. In order to simplify the description, the same reference signs are attached to those having functions similar those of lens driving device10according to the first exemplary embodiment and the description will later be made as regards only differences.

Lens barrel12has a shape like a hanging bell. In place of shielding cover42, shielding wall422A having a rectangular tubular shape and second base (cover)424A are used. In auto-focusing lens driving portion (AF unit)20A, spacer36A is mounted to lower leaf spring32serving as a first leaf spring.

A configuration except for those is similar to above-mentioned lens driving device10according to the first exemplary embodiment.

That is, damper material (not shown) is disposed between the fixed member (14,40,18, and44) and auto-focusing lens driving portion (AF unit)20A that is a movable portion.

Accordingly, lens driving device10A according to the second exemplary embodiment of the present invention has effects similar to those of above-mentioned lens driving device10according to the first exemplary embodiment.

While this invention has been particularly shown and described with reference to the exemplary embodiments thereof, the invention is not limited to the embodiment. It will be understood by those of ordinary skill in the art that various changes in form and details may be therein without departing from the spirit and scope of the present invention as defined by the claims. For example, although the four suspension wires are used as the supporting member for swingably supporting the auto-focusing lens driving portion with respect to the fixed member in the above-mentioned exemplary embodiments, the number of the suspension wires is not limited to four and therefore may be two or more. Furthermore, although protrusions306aare provided in magnet holder30in the above-described embodiment, a configuration may also be adopted in which, instead of providing protrusions306a, a concave portion or convex portion is provided on coil board40, and damper material is retained in that place.

The disclosures of the specification, the drawings and the abstract included in Japanese Patent Application No. 2012-029729 filed on Feb. 14, 2012 are incorporated herein by reference in their entirety.

REFERENCE SIGNS LIST