Lens barrel and optical apparatus including the same

The lens barrel has an image blur correction function for correcting an image blur, including: a movable member movable in a direction orthogonal to an optical axis while holding a lens and a driving magnet; and a fixed member for positioning the movable member in an optical axis direction and holding a driving coil and a magnetic member, in which: the driving magnet and the magnetic member constitute a driving portion for moving the movable member in the direction orthogonal to the optical axis; and in a plane orthogonal to the optical axis, a width of the magnetic member in a direction orthogonal to a direction of driving the movable member is larger than a width of the driving magnet in the direction orthogonal to the direction of driving the movable member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens barrel and an optical apparatus including the same, the lens barrel being suitable for driving a shift moving frame holding a lens for image blur correction so as to have a component in a direction orthogonal to an optical axis in order to correct an image blur due to vibration such as hand movements.

2. Description of the Related Art

In an optical apparatus such as a digital still camera and video camera, an image blur correction device has been used. Specifically, the image blur correction device detects hand movements of a user, and corrects a blur of a taken image (image blur).

In the image blur correction device, some optical elements for image blur correction (correction lens), which constitute an imaging lens, are driven in a pitch direction (longitudinal direction) and in a yaw direction (lateral direction).

With this configuration, a shift of a position of image formation due to hand movements is corrected. Thus, the image blur is cancelled (corrected).

In such image blur correction device, image blur correction may not be efficiently performed when a correction lens and a movable member (shift moving frame) movably supporting the correction lens rotate in a plane orthogonal to the optical axis.

Generally, a center of gravity of the movable member is situated at a position shifted from an axis in a direction of a thrust force generated from a driving portion for moving the movable member. Therefore, upon image blur correction, due to the thrust force, there is generated a rotational moment for rotating the movable member in the plane orthogonal to the optical axis. In addition, there is generated a force for rotating the movable member also due to vibration and friction other than the thrust force.

When the movable member is rotated in the plane orthogonal to the optical axis, the movable member may come in contact with a fixed member during image blur correction operation. As a result, driving properties of the movable member are changed, and hence the image is adversely affected.

Further, a position detection sensor for detecting a position of the movable member of the image blur correction device includes an optical sensor in many cases. The optical sensor includes a combination of a Hall element, a light emitting element, and a light receiving element, the Hall element including a combination of a magnet and a magnetic detection element. The position detection sensor is adapted for a movement of the correction lens in one of a yaw direction and a pitch direction in the plane perpendicular to the optical axis.

Here, the yaw direction is defined as a horizontal direction in the plane perpendicular to the optical axis in a posture of the camera in use. Meanwhile, the pitch direction is defined as a perpendicular direction in the plane perpendicular to the optical axis in a posture of the camera in use.

Thus, when the correction lens is rotated largely in the plane orthogonal to the optical axis, output properties of the position detection sensor are changed. As a result, it is impossible to correctly detect the position of the correction lens, and a so-called cross talk is generated. In addition, when a position detection property is changed due to rotation of the correction lens, feedback position control causes anomalous oscillation. Further, optical performance upon correction of hand movements is deteriorated.

In rotation of the correction lens within such an amount that the feedback position control is allowed, feedback position control can be performed in order to position the correction lens to a target position. However, the above-mentioned feedback position control leads an increased electric power consumption.

Conventionally, there has been known an image blur correction device. Specifically, in the image blur correction device, a correction lens held by a movable member is displaced in any one of a yaw direction and a pitch direction without being rotated about an optical axis (Japanese Patent Application Laid-Open No. H05-297443 and Japanese Patent Application Laid-Open No. H10-319465).

Japanese Patent Application Laid-Open No. H05-297443 discloses an image blur correction device provided with a guide shaft for regulating rotation. In addition, Japanese Patent Application Laid-Open No. H10-319465 discloses an image blur correction device in which rotation is prevented with a tension coil spring.

In the image blur correction device in Japanese Patent Application Laid-Open No. H05-297443, a gimbal structure is employed. With this structure, the correct lens is held by two guide shafts so as to be guided by the two guide shafts. Thus, the correct lens is allowed to move in any one of a yaw direction and a pitch direction, which are defined as two axial directions orthogonal to each other in the same plane. For image blur correction, response within a frequency band of several 10 Hz is needed, and also for position accuracy, high accuracy control is required. Therefore, it is essential to hold the correct lens with little friction and little backlash.

Therefore, In Japanese Patent Application Laid-Open No. H05-297443, in order to accurately displace the correction lens in the same plane, it is preferred that the two guide shafts be fitted into each other at two points. However, in order to hold those two guide shafts, which are fitted into each other at two points, without backlash but with high accuracy, a more complex structure is required.

In addition, in this structure, a rotational moment for rotating the movable member remains, and a torsion force is generated between the guide shafts and a bearing provided to the moving frame when the movable member is displaced. Therefore, it is difficult to satisfactorily maintain micro-amplitude properties.

In a lens shifting device of Japanese Patent Application Laid-Open No. H10-319465, a movable member holding a correction lens is supported in parallel to a plane perpendicular to the optical axis with at least three balls rotatably held by a fixed member. Further, by an elastic member provided for generating a pressing force for sandwiching the three balls between the movable member and the fixed member, rotation of the movable member about the optical axis is prevented.

In this case, rolling friction of the three balls is lower than sliding friction acting between a guide shaft and a bearing. Therefore, it is possible to satisfactorily maintain the micro-amplitude properties of the correction lens due to a friction of a mechanical mechanism.

In this case, when a center of the correction lens most frequently used is situated in vicinity of the optical axis, if, in a driving direction of the movable member, a force from the elastic member is not applied uniformly to the movable member from both sides, the force from the elastic member acts as a load. As a result, the electric power consumption increases. In addition, a unit for uniformly applying, in the driving direction of the movable member, the force from the elastic member to the movable member is required.

Meanwhile, in recent years, an image pickup element (charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS)) for converting a subject image, which is formed by means of an photographic optical system, into an electrical signal has a shorter pixel pitch by grace of development of a semiconductor micro-processing technology. Moving amount of a shift lens group for correcting hand movements having the same amount is substantially proportional to an image pickup area. For this reason, when the pixel pitch of the image pickup element is shorter, it is more difficult to satisfactorily correct the image blur without more micro movement having a higher accuracy.

SUMMARY OF THE INVENTION

The present invention has an object to provide a lens barrel provided with an image blur correction device, and an optical apparatus including the lens barrel, the lens barrel being capable of restricting rotation of a correction lens about an optical axis, and being further capable of correcting an image blur with a little electric power consumption.

According to the present invention, it is possible to obtain a lens barrel provided with an image blur correction device, and an optical apparatus including the lens barrel, the lens barrel being capable of restricting rotation of a correction lens about an optical axis, and being further capable of correcting the image blur with a little electric power consumption.

According to the invention, there is provided a lens barrel having an image blur correction function for correcting an image blur, comprising: a movable member movable in a direction orthogonal to an optical axis while holding a lens and a driving magnet; and a fixed member for positioning the movable member in an optical axis direction and holding a driving coil and a magnetic member, wherein: the driving magnet, the driving coil, and the magnetic member constitute a driving portion for moving the movable member in the direction orthogonal to the optical axis; and in a plane orthogonal to the optical axis, a width of the magnetic member in a direction orthogonal to a direction of driving the movable member is larger than a width of the driving magnet in the direction orthogonal to the direction of driving the movable member.

According to the present invention, there is also provided a lens barrel, wherein: the driving portion comprising: a first driving portion for driving the movable member in the plane orthogonal to the optical axis in a first direction; and a second driving portion for driving the movable member in the plane orthogonal to the optical axis in a second direction orthogonal to the first direction, wherein, in the plane orthogonal to the optical axis, the width of the magnetic member in the direction orthogonal to the direction of driving the movable member constituting each of the first driving portion and the second driving portion is larger than the width of the driving magnet in the direction orthogonal to the direction of driving the movable member.

According to the present invention, there is also provided a lens barrel, wherein the relation A≧(2×d+B) is obtained, where d (mm) represents a maximum movable distance of the movable member, A (mm) represents the width of the magnetic member in the direction orthogonal to the direction of driving the movable member, and B (mm) represents the width of the driving magnet in the direction orthogonal to the direction of driving the movable member.

According to the present invention, there is also provided an optical apparatus, comprising: the lens barrel; and an image pickup element.

According to the present invention, there is also provided a lens barrel having an image blur correction function for correcting an image blur, comprising: a movable member movable in a direction orthogonal to an optical axis while holding a lens, a driving coil, and a magnetic member; and a fixed member for positioning the movable member in an optical axis direction and holding a driving magnet, wherein: the driving magnet, the driving coil, and the magnetic member constitute a driving portion for moving the movable member in the direction orthogonal to the optical axis; and in a plane orthogonal to the optical axis, a width of the driving magnet in a direction orthogonal to a direction of driving the movable member is larger than a width of the magnetic member in the direction orthogonal to the direction of driving the movable member.

According to the present invention, there is also provided a lens barrel, wherein: the driving portion comprising: a first driving portion for driving the movable member in the plane orthogonal to the optical axis in a first direction; and a second driving portion for driving the movable member in the plane orthogonal to the optical axis in a second direction orthogonal to the first direction, wherein, in the plane orthogonal to the optical axis, the width of the driving magnet in the direction orthogonal to the direction of driving the movable member constituting each of the first driving portion and the second driving portion is larger than the width of the magnetic member in the direction orthogonal to the direction of driving the movable member.

According to the present invention, there is also provided a lens barrel, wherein the relation A≧(2×d+B) is obtained, where d (mm) represents a maximum movable distance of the movable member, A (mm) represents the width of the magnetic member in the direction orthogonal to the direction of driving the movable member, and B (mm) represents the width of the driving magnet in the direction orthogonal to the direction of driving the movable member.

According to the present invention, there is also provided an optical apparatus, comprising: the lens barrel; and an image pickup element.

DESCRIPTION OF THE EMBODIMENTS

A lens barrel according to the present invention includes a lens for vibration isolation, driving magnets, and a movable member. The movable member is movable in a direction perpendicular to an optical axis, while holding the driving magnets. Further, the lens barrel according to the present invention includes multiple balls and a fixed member. The multiple balls are for positioning the movable member in a direction of the optical axis. The fixed member is for positioning the multiple balls in the direction of the optical axis, and holding a driving coil and a magnetic member.

The driving magnets and the magnetic member constitute a driving portion for moving the movable member in a plane orthogonal to the optical axis.

The multiple balls are rotatably sandwiched due to a magnetic attraction force between the driving magnets and the magnetic member.

A width in a direction orthogonal to a direction in which the movable member is driven by the magnetic member is set to be larger than a width in a direction orthogonal to a direction in which the movable member is driven by the driving magnets.

By energizing the driving coil, the driving portion is driven so as to cause the movable member to move. In this manner, an image blur is corrected.

First Example

FIG. 1illustrates a sectional view of a lens barrel provided with an image blur correction device according to a first example.FIG. 2illustrates an exploded perspective view of the lens barrel ofFIG. 1. Note that, the lens barrel is attached to an imaging apparatus such as a video camera or a digital still camera, or otherwise, the lens barrel is integrally provided to such imaging apparatus for use.

The lens barrel includes a variable magnification optical system (zoom lens) having a four-group structure including lens groups having positive, negative, positive, and positive refractive indexes. That is, the lens barrel includes: a first group lens L1fixed (immobile) in the optical axis direction; and a second group lens L2for variable magnification. Further, the lens barrel includes: a third group lens L3for image blur correction; and a fourth group lens L4which moves for variable magnification and for focusing.

The second group lens L2moves in the optical axis direction, and performs variable magnification operation. The third group lens L3acts as a movable optical element for vibration isolation. Specifically, the optical element for vibration isolation moves in a direction orthogonal to the optical axis, that is, in a longitudinal direction and a lateral direction to be described later, and performs blur correction (image blur correction). The fourth group lens L4moves in the optical axis direction, and performs correction action and focusing action of an image surface which varies depending on variable magnification.

The first group lens L1is held by the fixed lens barrel1. The second group lens L2is held by a second-group moving frame2. The third group lens L3is held by a shift unit3. The fourth group lens L4is held by a fourth-group moving frame4.

In addition, on a rear side (image side) of the fourth-group moving frame4, there is provided a CCD holder5for fixing an image pickup element including a CCD. The lens barrel1is fixed to a forward fixed lens barrel6with vises. The CCD holder5and the forward fixed lens barrel6are fixed to a rearward fixed lens barrel7with vises.

The second-group moving frame2is movably supported in the optical axis direction by guide bars8and9. The guide bars8and9are positioned and fixed by the forward fixed lens barrel6and the rearward fixed lens barrel7. In addition, the fourth-group moving frame4is movably supported in the optical axis direction by guide bars10and11. The guide bars10and11are positioned and fixed by the CCD holder5and the rearward fixed lens barrel7.

The shift unit3is positioned with respect to the rearward fixed lens barrel7and is fixed with two vises. An aperture stop device12arranged in the third group lens L3employs a so-called guillotine system. Specifically, in the guillotine system, a diameter of an opening of a variable magnification optical system is changed, and two aperture blades are moved in an opposite direction to each other to thereby change the diameter of the opening.

An aperture motor12aof the aperture-stop device12includes a galvanometer.

The fourth group lens L4is driven in the optical axis direction by a voice coil motor13. The voice coil motor13includes a magnet13a, a yoke13b, a yoke13c, and a coil13d. In the voice coil motor13, the yoke13bis pressed-fitted into and fixed to the rearward fixed lens barrel7. The magnet13aand the yoke13care magnetically fixed to yoke13b. By supplying an electrical current to the coil13d, a Lorentz force is generated in the coil13d. Thus, the coil13dmay be driven in the optical axis direction. The coil13dis fixed to the fourth-group moving frame4, and hence the fourth-group moving frame4is driven in the optical axis direction due to driving of the coil13d.

A zoom motor14is fixed to the rearward fixed lens barrel7with two vises. The second group lens L2is driven in the optical axis direction by the zoom motor (stepping motor)14and performs variable magnification operation. The zoom motor14includes a rotating rotor and a lead screw14awhich is coaxial with the rotating rotor. A rack2aprovided to the second-group moving frame2is mated to the lead screw14a. Thus, the second group lens L2is driven in the optical axis direction due to rotation of the rotor. In addition, a backlash of each of the guide bars8and9, the rack2a, and the lead screw14ais compensated by a helical torsion coil spring2b. In this manner, a backlash due to fitting or mating is prevented.

A photo interrupter15is used as a zoom reset switch. Specifically, the zoom reset switch optically detects a movement of a light-shielding portion2cto the optical axis direction, the light-shielding portion2cbeing formed in the second-group moving frame2. Thus, it is detected that the second group lens L2is positioned at a reference position.

An encoder (optical sensor)16fixed to the rearward fixed lens barrel7includes a light emitting portion and a light receiving portion. The encoder16irradiates a light, which is emitted from the light emitting portion, to a scale17adhesively fixed to the fourth-group moving frame4. Then, a reflected light is read in the light receiving portion. In this manner, an absolute position of the fourth group lens L4in the optical axis direction is detected.

Next, a structure of the shift unit3for moving the third group lens L3in a direction orthogonal to the optical axis direction is described with reference toFIGS. 3 and 4.FIG. 3is an exploded perspective view of a shift unit3.FIG. 4is an enlarged sectional view of a driving portion in a pitch direction (longitudinal direction) of the shift unit3.

The shift moving frame22for holding the third group lens L3is driven by an actuator for longitudinal drive. The actuator is for correcting the image blur due to angular change in the pitch direction, that is, in the longitudinal direction of the lens barrel or in the longitudinal direction in the imaging direction. Further, the shift moving frame22holding the third group lens L3is driven in the plane orthogonal to the optical axis direction by an actuator for a lateral drive. The actuator is for correcting the image blur due to angular change in the yaw direction, that is, in the lateral direction of the lens barrel or in the lateral direction in the imaging direction.

In an optical apparatus such as a camera, as illustrated inFIG. 8, there are installed a pitch-direction-blurring sensor59and a yaw-direction-blurring sensor60, such as a vibratory gyroscope. The pitch-direction-blurring sensor59is for detecting angular change in the pitch direction. The yaw-direction-blurring sensor60is for detecting angular change in the yaw direction (lateral direction).

A control circuit (such as CPU responsible for controlling the entire of the optical apparatus)56controls each of the actuators based on output from the blurring sensors50and60and on signals from a position sensor (to be described later) for detecting the position in the plane orthogonal to the optical axis direction of the third group lens L3. Note that, each of the actuators is independently driven and controlled in the pitch direction and the yaw direction.

In addition, the actuator and the position sensor for the pitch direction, and the actuator and the position sensor60for the yaw direction are arranged so as to form an angle of 90° with each other and have the same structure. Therefore, in the following, the description is made only regarding the pitch direction (longitudinal direction). Note that, suffixes p and y of the reference symbols indicates the pitch direction and the yaw direction, respectively.

The shift moving frame22has a function for holding the third group lens L3and displaces in the direction orthogonal to the optical axis direction in order to correct the image blur.

Magnets24pfor both drive and position detection is press-fitted into and held by a magnet base18in the direction orthogonal to the optical axis direction. The magnets24pare press-fitted and incorporated into the magnet base18, and hence a relative position relation between the magnet base18and the magnets24pis not changed.

The magnet base18and the shift moving frame22is coupled and fixed to each other with a vis in a state in which a metal plate19is sandwiched therebetween. The metal plate19, the magnet base18, and the shift moving frame22constitute one element of the movable member. The magnets24p, which also have a function of position detection, is positioned at a position fixed with respect to the shift moving frame22holding the third group lens L3. Thus, it is possible to accurately detect the position of the third group lens L3by the magnets24p.

It is suitable that the metal plate19is made of a stainless steel, for example.

Between the shift base21and the magnet base18, three balls20are arranged in the plane orthogonal to the optical axis direction. Note that, it is sufficient that multiple balls20are provided. Between the balls20and the magnet base18, the above-mentioned metal plate19is arranged. With this metal plate19, when the lens barrel receives some impact, the balls20are not bumped on the magnet base18, which is a molded component, and hence there are not formed a marks of the balls in the magnet base19. Thus, this metal plate19prevents driving properties of the shift unit3from being deteriorated. In addition, the balls20are, due to magnetic attraction force of the magnets24for drive and a magnetic member29p, rotatably held by a ball holder portion21aformed in the shift base (fixed member)21.

Note that, it is suitable that the balls20are made of a stainless steel so as not to be attracted to the magnet24arranged in vicinity of the balls.

The magnets24pfor drive and the magnetic member29pconstitute one element of the driving portion.

It is an attraction force acting between the magnets24pand a rear yoke29p(driving portion) that is for securely abutting the balls20against the shift base (end surface in the optical axis direction of the ball holder21a) and the magnet base19(metal plate19). With this attraction force, the magnet base18is biased toward the shift base21. As a result, the three balls20are abutted against the end surface in the optical axis direction of the three ball holder portions21aand against three points19aof the metal plate19, in a pressed state.

Each of the surfaces of the metal plate19, against which the three balls20are abutted, extends in the direction orthogonal to the optical axis direction AXL of the photographic optical system. Nominal diameters of the three balls20are the same, and hence differences of positions of the three ball holders21aprovided to the shift base21in the optical axis direction between the end surfaces of the optical axis direction are kept being small. With this structure, it is possible to move the third group lens L3held by the shift moving frame22in the plane orthogonal to the optical axis direction without causing the third group lens L3to be tilted with respect to the optical axis.

Next, the actuator for driving the shift moving frame22for holding the magnet base18and the third group lens L3is described. As describe above, the magnets24phave, as illustrated inFIG. 5, two magnetic poles in a radial direction from the optical axis AXL. The rear yoke23pis for closing a magnetic flux on a front side of the magnets24pin the optical axis direction. The rear yoke23pis attracted and fixed to the magnets24p. The coil28pis adhesively fixed to the shift base21. The rear yoke (magnetic member)29pis for closing a magnetic flux on a rear side of the magnets24pin the optical axis direction.

The rear yoke29pis arranged on an opposite side to the magnets24pwhile sandwiching the coil28p, and the rear yoke is held by the shift base21. A magnetic circuit is formed by the magnets24p, the front yoke23p, the rear yoke29p, and the coil28p.

By supplying an electrical current to the coil (coil for drive)28d, a Lorentz force is generated in a direction substantially orthogonal to a magnetic boundary of the magnets24pdue to mutual repulsion of a magnetic line of flux generated in the magnets24pand the coil28p. Thus, the magnet base18is caused to move in the direction orthogonal to the optical axis direction. This is a so-called moving magnet type actuator (driving portion).

Actuators (driving portion) having such structure are arranged in the longitudinal direction and the lateral direction. Therefore, it is possible to drive the magnet base18and the shift moving frame22coupled to the magnet base18in two directions orthogonal to the optical axis direction, the two directions being substantially orthogonal to each other. Further, by combining drive in the longitudinal direction with drive in the lateral direction, it is possible to freely move the magnet base18and the shift moving frame22in a plane orthogonal to the optical axis direction within a predetermined range.

Note that, a friction when the magnet base18acts in the direction orthogonal to the optical axis direction is only a rolling friction each generated between the balls20and the metal plate19and between the balls20and the ball holder portions21aas long as the balls20are abutted against a wall of the ball holder portions21a. Therefore, despite acting of the above-mentioned attraction force, the magnet base18(that is, the shift moving frame22holding the third group lens L3) is capable of very smoothly moving in the plane orthogonal to the optical axis direction, and it is possible to control even a micro amount of the movement. Note that, by applying a lubricating oil to the balls20, it is possible to further reduce the frictional force.

Next, a position detection of the magnet base18and the shift moving frame22holding the third group lens L3is described. A Hall element27pfor converting a magnetic flux density into an electrical signal is fixed to a flexible print cable (hereinafter, referred to as FPC)26by soldering. The FPC26is positioned and fixed with respect to the shift base21. In addition, by fixing a supporting metal piece25with respect to the shift base21with a vis, the FPC26is prevented from being lifted up, and a position of the Hall element27pis prevented from being shifted. With the following structure, a position sensor for detecting the position of the shift moving frame22holding the magnet base21and the third group lens L3is formed.

When the shift moving frame22holding the magnet base18and the third group lens L3is driven in one of the longitudinal direction and the lateral direction, a change of the magnetic flux density of the magnets24pis detected by the Hall element27p. Then, an electrical signal indicating the change of the magnetic flux density is output. According to the Hall element27p, a control circuit56is capable of detecting the position of the shift moving frame22holding the magnet base18and the third group lens L3. Note that, the magnets24pare magnets for drive, and the magnets24pare used also as magnets for position detection at the same time.

Here, a structure of the driving portions23p,24p,28p, and29pin this example is described.

FIG. 5illustrates a structure of the driving portion in this example. The magnets24p, the front yoke23p, the coil28p, and the rear yoke29phave a symmetrical shape with respect to a center of the driving portion so that a direction of a driving force of the driving portion is one direction of the pitch direction and the yaw direction.

Next, a relation of movement and rotation due to a returning force generated by the attraction force, of the movable member (shift moving frame)22in this example is illustrated inFIGS. 6A to 6C.

FIG. 6Aillustrates an arrangement of the coils (28pand28y) and the rear yokes29(29pand29y) on a fixing side in a state in which the third group lens L3, which is supported by the movable member22, and the magnets24(24pand24y) are situated at a center position.

A center O of the third group lens L3is situated on the optical axis. The attraction force acting between the magnets24and the rear yokes29is proportional to the inverse of the square of a strength of magnetic charge of two objects and distance between the two objects, as described by Coulomb's law. Therefore, if each of the magnets24and the rear yokes29have a symmetrical shape with respect to the center of the driving portion, when the magnets24are situated at the center position of the driving portion, the attraction force in the pitch direction (Fp) and the attraction force in the yoke direction (Fy) are balanced in each of the directions. In addition, when the magnets24are moved from the center of the driving portion, a magnetic charge increases in an opposite direction to a moving direction. Thus, attraction force for returning the magnets24to the center of the driving portion is generated.

Note that, inFIG. 6A, the magnets24p, the coil28p, and the rear yoke29pconstitute a perpendicular driving portion for moving the movable member in a perpendicular direction Fp.

In addition, the magnets24y, the coil28y, and the rear yoke29yconstitute a horizontal driving portion for moving the movable member in a horizontal direction Fy.

FIG. 6Billustrates a relation of a driving force and an attraction force when the movable member22is displaced in the yaw direction from the state ofFIG. 6A. When the movable member22is displaced in the yaw direction, by supplying an electrical current to the coil28y, a Lorentz force is generated from the coil28y. Due to the Lorentz force, a thrust force100for driving the movable member22in the yaw direction is generated. Due to the thrust force100, the movable member22is moved by a distance d.

In this case, the magnets24(24pand24y) arranged in the movable member22are also moved by the distance d from the center position of the driving portion. Thus, returning forces101pand101yare generated, with which the magnets24returns to their original positions with the attraction force.

Upon the above-mentioned action, the thrust force100and the returning force101yact on the identical axis to an axis of a thrust force direction, while the returning force101acting on the driving portion in the pitch direction is not on the identical axis to that of the thrust force100. Thus, a rotational moment102for rotating the movable member with the thrust force100and the returning force101pis generated.

FIG. 6Cillustrates a state in which the rotational moment due to the thrust force100and the returning force101pofFIG. 6Bis balanced. The center point O of the third group lens L3is moved from the optical axis in the yaw direction by the distance d, and the movable member22is rotated by a rotational angle θ1in the plane orthogonal to the optical axis. In this case, a rotational direction in the plane orthogonal to the optical axis is in a stable state because the thrust force100and the returning force101pare balanced. Thus, even when an additional force in the rotational direction acts, the force for returning to the position of the rotational angle θ1is generated.

InFIG. 6A, a reference symbol A indicates a longitudinal dimension of the rear yoke (magnetic member)29p, and a reference symbol B indicates a longitudinal dimension of the magnets24p. In this example, supposed that the distance d is a maximum movable distance of the movable member22in one direction from the optical axis, a dimensional relation between the width A of the magnetic member29pand the width B of the magnets for drive24pis set as follows:
A≧(2×d+B).

That is, the width A (mm) is set to be larger than the width B (mm).

With this setting, even when the movable member22is displaced in the yaw direction by the maximum amount, as illustrated inFIG. 6B, the magnets24pis not moved on a left side over the rear yoke29p.

In this example, the width A is set to be larger than the width B in the yaw direction and the pitch direction.

FIGS. 9A to 9Cillustrates an example of prior art. In this example of prior art, the dimensional relation between the width A of the magnetic member29pand the width B of the magnets for drive24pis set to be as follows:
A=B.

Therefore, when the movable member is displaced in the yaw direction by the maximum amount, as illustrated inFIG. 9B, the magnets24pare moved on the left side over the rear yoke29p.

In focusing on the above-mentioned returning force, as illustrated inFIG. 9B, returning forces104pand103y, with which the magnets returns to their original positions with the attraction force, are generated. In comparison with the case where the magnets are not moved over the rear yoke as in this example, in the example of prior art, correspondingly to an amount, by which the magnets24pare moved over the rear yoke29p, due to the magnetic flux between the magnets24pand the rear yoke29p, the attraction force, which attracts the magnets24pto the right direction in the drawing, increases. Therefore, the returning force101pin this example illustrated inFIGS. 6A to 6Cis lower than the returning force104pin the example of prior art illustrated inFIGS. 9A to 9C.

Therefore, the rotational angle θ1in this example illustrated inFIGS. 6A to 6Cis lower than a rotational angle θ2in the example of prior art illustrated inFIGS. 9A to 9C. As a result, rotation is restricted.

Though, in the foregoing, the description is made regarding displacement in the yaw direction, also for displacement in the pitch direction, its structure is the same as the structure for displacement in the yaw direction except that a direction for arrangement is shifted by 90°.

The width A of a direction orthogonal to a direction in which the movable member is driven by the magnetic members29yand29pis larger than the width B of a direction orthogonal to a direction in which the movable member is driven by the magnets for drive24yand24p. In this case, the magnetic members29yand29pconstitute a horizontal driving portion (24y,28y, and29y) and a perpendicular driving portion (24p,28p, and29p), respectively.

In addition, the dimensional relation between the width A and the width B is not limited to the following relation:
A≧(2×d+B).

For example, it is sufficient to determine the most suitable value complying with a target performance under consideration of a size and a cost under the setting of A>B including A>(d+B). For example, it is sufficient that A≧(d+B) is set.

Here, in order to arbitrarily move the position of the third group lens L3despite rotation of the movable member22as illustrated inFIGS. 6A to 6C, the position of the third group lens L3must be precisely detected even when the movable member22is rotated. For this reason, next, a relation between a rotational angle of the movable member22and output of the position detection unit is described.

FIG. 7Aillustrates an arrangement of the third group lens L3, the magnets24, and the Hall elements27pand27yserving as the position detection unit when the movable member22is situated at the center position. The Hall element27pin the pitch direction and the Hall element27pin the yaw direction is arranged so that an intersection of a detecting direction axis is corresponding to the optical axis O. Further, component of the density of the magnetic flux in the optical axis direction due to the magnets24pand24yis detected, and hence the positions of the magnets can be detected in view of change of the density of the magnetic flux upon displacement in the driving direction.

FIG. 7Billustrates change of an output value from the Hall element when the movable member is rotated by an angle θ1about an arbitrary point in a plane orthogonal to the optical axis. InFIG. 7B, it is supposed that a position detection point in the pitch direction is PA, and a position detection point in the yaw direction is YB. A center of the lens is indicated by O. The movable member is rotated about a point R. When a rotational angle θ1is not so large, each of points PA, PB, and O is moved in a normal direction with respect to a straight line linking each of the points PA, PB, and O and the point R.

The above-mentioned movement of each of the points is indicated by Va, Vb, and Vo, respectively. The components which is resolved in one of the detection direction axis y of the yaw direction and the detection direction axis p of the pitch direction are indicated by Vap, Vay, Vbp, Vby, Vop, and Voy. In this case, the Hall element hardly has a sensibility against the flux bundle in the detecting direction and the perpendicular direction, and hence the components Vbp and Vay are not detected by the Hall element. In addition, the intersection of two detection direction axes p and y is corresponding to the optical axis O, and hence the following relation is obtained regarding the pitch component and the yaw component of the movement of the optical axis O:
Vop=Vap
Voy=Vby.

This fact indicates that it is possible to detect the amount of the movement about the lens without receiving the influence of rotation. It is possible to move the third group lens L3to a precise position under control of positioning.

As described above, it is found that, when the rotational angle is not so large, it is possible to precisely detect the position of the third group lens L3even when the movable member22rotates.

In the foregoing, the exemplary first example according to the present invention is described. In this example, the returning force is reduced, which is generated due to the attraction force acting on the magnet24and the rear yoke29on an opposite side with respect to the driving direction of the movable member22. With this structure, the above-mentioned rotational moment102and the rotational angle θ1are reduced. Thus, rotation in the plane orthogonal to the optical axis of the movable member is restricted.

As a result, the thrust force needed for position correction is reduced in position feed-back control of the movable member22without an additional mechanical mechanism. Thus, the electric power consumption may be reduced. Further, it is possible to obtain an image blur correction device excellent in micro-amplitude properties, a lens barrel provided with the image blur correction device, and an optical apparatus including the lens barrel.

Additionally, in this example, the returning force by the attraction force generated from the magnets for drive is reduced24, and hence rotation of the correction lens in the plane orthogonal to the optical axis is easily restricted without one of an additional mechanical mechanism and an additional driving portion. In addition, rotation is restricted, and hence it is possible to reduce the electric power consumption needed for position feed-back control by rotation, and to obtain the image blur correction device excellent in micro-amplitude properties.

In this example, though the third group lens L3supported by the movable member22is driven by two driving portions, that is, the driving portion for the yaw direction and the driving portion for the pitch direction, the present invention is applicable to an embodiment in which three driving portions are employed to drive the third group lens L3supported by the movable member22.

In this case, it is preferred that, in the plane orthogonal to the optical axis, about the optical axis, the three driving portions be arranged at an interval of 120°, and that three actuators arranged corresponding to the three driving portions be independently driven in order to correct an image blur due to vibration such as hand movements.

Note that, needless to say, the present invention is not limited to those examples, and various modifications and changes are possible within a range of the gist of the present invention.

Second Example

FIG. 8is a schematic view of main parts of an imaging apparatus (camera) of a second example according to the present invention.

The imaging apparatus of the second example installs therein the lens barrel capable of correcting the image blur of the first example.

FIG. 8illustrates a configuration of electrical processing for driving processing of each member in the camera installing therein the lens barrel of the first example. InFIG. 8, the components described inFIGS. 1 to 6are indicated by the same symbols.

In the imaging apparatus (camera) inFIG. 8, a blur signal of the camera, which is detected by the pitch-direction-blurring sensor59and the yaw-direction-blurring sensor60(hereinafter, referred to as “sensors”), is input into the control circuit56.

The control circuit56calculates a driving amount of the movable member for the image blur correction according to the signal from the sensors. Then, the control circuit56inputs the calculated driving amount into a third-lens-group driving source31.

The third-lens-group driving source31energizes the coils for drive28pand28yaccording to the input signal. As a result, the movable member is moved so as to correct the image blur.

The stepping motor (hereinafter, referred to as zoom motor)14is a driving source of the second group lens L2. The voice coil motor13is a driving source of the fourth-group moving frame4holding the fourth group lens L4. The aperture motor (aperture-stop-device driving source)12ais a driving source of the aperture-stop device12. For the stop aperture, the galvanometer is used.

The photo interrupter15is the zoom reset switch for detecting whether or not the second-group moving frame2is positioned at the reference position in the optical axis direction. After detecting that the second-group moving frame2is positioned at the reference position, the number of pulse signals input into the stepping motor14is counted. Thus, it is possible to detect the amount of movement (position with respect to the reference position) of the second-group moving frame2in the optical axis direction.

The optical sensor16detects the absolute position of the fourth group lens L4in the optical axis direction.

For the aperture-stop encoder36, the following type is used. Specifically, in the type, the Hall element is arranged in the aperture-stop-device driving source12a, and a rotational positional relation between the rotor and a stator is detected.

The control circuit56is responsible for the signal of the camera. The control circuit56includes a central processing unit (CPU). A camera signal processing circuit50performs signal processing such as predetermined augmentation and gamma correction with respect to output from the image pickup element58.

A contrast signal of a picture signal processed as described above is supplied to an AE gate52and an auto focus (AF) gate51. Each of the AE gate52and the AF gate51sets a picking-up range of the signal, which is optimum for exposure control and focusing, from the picture signal in an entire image surface. A size of the gate may be variable or alternatively multiple gates may be provided.

An AF signal processing circuit53processes the AF signal for the AF and generates at least one output about a high frequency component of the picture signal.

A zoom tracking memory55stores information of the position of the fourth-group moving frame4corresponding to a distance between the fourth-group moving frame4and the object to be taken and to a distance between the fourth-group moving frame4and the second-group moving frame2upon the variable magnification. Note that, for the zoom tracking memory55, a memory in the control circuit56may be used.

For example, when the zoom switch54is operated by a user, the control circuit56maintain a predetermined positional relation between the second-group moving frame2and the fourth-group moving frame4, the predetermined positional relation being calculated from information of the zoom tracking memory55. That is, with the zoom switch54, a count value, which indicates the current absolute position of the second-group moving frame2in the optical axis direction, and a calculated position to be set of the second-group moving frame2are corresponding to each other. Further, driving of the zoom motor14and the voice coil motor13is controlled by the zoom switch54, and hence a count value, which indicates the current absolute position of the fourth-group moving frame4in the optical axis direction, and a calculated position to be set of the fourth-group moving frame4are corresponding to each other.

In addition, in auto focus operation, the control circuit56controls driving of the voice coil motor13so that output of the AF signal processing circuit53exhibits a peak.

Further, in order to obtain suitable exposure, the control circuit56sets an average value of output of a Y signal, which passes by the AF gate52, as a referential value, controls driving of the aperture motor12aso that output of the aperture-stop encoder36is the referential value, and controls the amount of light.

The control circuit56controls energizing to each of the coils28yand28pserving as a component of the third-group-lens driving source31based on a signal from the output sensor29(Hall element29y,29p) from the blurring sensors59and60. In this manner, the movable member holding the third group lens L3is driven so as to correct the image blur.

In the examples described above, the imaging apparatus in which the lens barrel is integrally provided to a main body of the camera is described. The lens barrel according to the present invention is also applicable to an interchangeable lens device detachable to the main body of the camera. Alternatively, the lens barrel according to the present invention is also applicable to a silver film camera, the digital still camera, and the video camera. The function for vibration isolation according to the present invention is also applicable to an optical apparatus such as an observation instrument including binoculars.

Third Example

FIG. 10is a block diagram of main parts of a third example when the image pickup element58is moved for image blur correction in replace of the movement of the movable member holding the third group lens L3ofFIG. 8.

A basic structure of the image blur correction device is the same as that of the first example. Except for image blur correction in which the image pickup element58is moved for image blur correction in replace of the third group lens L3, the electrical configuration is the same as that of the second example.

InFIG. 10, the image pickup element58includes one of a CCD and a CMOS, and is driven by an image-pickup-element driving source32.

The blurring sensors50and60detect the blur in the pitch direction and the yaw direction. The control circuit56controls energizing to the coil serving as a component of the image-pickup-element driving source32according to output from the blur sensors59and60and the signal from the position sensor33. Thus, the image pickup element58is driven so as to correct the image blur.

Note that, a structure of the driving portion of each of the above-mentioned examples is not limited to the image blur correction device, and such structure is applicable to a driving apparatus for moving a member in a horizontal direction and a perpendicular direction.

Fourth Example

In the first example, in the magnetic circuit ofFIG. 5, the example in a so-called moving magnet type actuator in which the front yoke23pand the magnets24pare movable and the coil28pand the rear yoke29pare fixed. Here, in the magnetic circuit ofFIG. 5, as a variant, an example in the moving coil type actuator is described, in which the front yoke23pand the magnets24pare fixed and the coil28pand the rear yoke29pare movable.

A basic mechanic structure of the shift unit3is similar to that of the first example, and the detailed description thereof is omitted. What is significantly different is that the coil28pand the rear yoke29pare configured to be movable integrally with the shift moving frame22, and that the front yoke23pand the magnets24pare retained by the fixed shift base21.

By energizing the coil, the coil and the rear yoke are actuated integrally with each other in the fourth example, while the magnets are actuated in the first example. An action/effect to be obtained is the same as that of the first example. Specifically, the shift moving frame22can be freely moved within a predetermined range in the plane orthogonal to the optical axis.

FIGS. 11A to 11Cillustrate, similarly toFIGS. 6A to 6Cof the first example, a relation of movement of the movable member (shift moving frame)22and rotation by the returning force due to the attraction force in this example.

FIG. 11Aillustrates arrangement of the magnets24(24pand24y) on the fixing side in a state in which the third group lens L3supported by the movable member22, the coils28(28pand28y), and the rear yokes29(29pand29y) are situated at the center position.

Note that, the magnets24p, the coil28p, and the rear yoke29pconstitute a perpendicular driving portion for moving the movable member in the perpendicular direction Fp.

In addition, the magnets24y, the coil28y, and the rear yoke29yconstitute a horizontal driving portion for moving the movable member in the horizontal direction Fy.

FIG. 11Billustrates a relation of a driving force and an attraction force when the movable member22is displaced in the yaw direction (left direction in the drawing) from the state ofFIG. 11A. When the movable member22is displaced in the yaw direction, by supplying an electrical current to the coil28y, a Lorentz force is generated from the coil28y. Due to the Lorentz force, a thrust force106for driving the movable member22in the yaw direction is generated. Due to the thrust force106, the movable member22is moved by a distance d.

In this case, the rear yokes29(29pand29y) arranged in the movable member22are also moved by the distance d from the center position of the driving portion. Thus, returning forces107pand107yfor returning to their original positions with the attraction force with the magnets24are generated.

Upon the above-mentioned action, the thrust force106and the returning force107yact on the identical axis to an axis of a thrust force direction, while the returning force107pacting on the driving portion in the pitch direction is not on the identical axis to the thrust force106. Thus, a rotational moment108for rotating the movable member with the thrust force106and the returning force107pis generated.

FIG. 11Cillustrates a state in which the rotational moment due to the thrust force106and the returning force107pofFIG. 11Bis balanced. The center point O of the third group lens L3is moved from the optical axis in the yaw direction by the distance d, and the movable member22is rotated by a rotational angle θ1in the plane orthogonal to the optical axis. In this case, a rotational direction in the plane orthogonal to the optical axis is in a stable state because the thrust force106and the returning force107pare balanced. Thus, even when an additional force in the rotational direction acts, the force for returning to the position of the rotational angle θ1is generated.

InFIG. 11A, a reference symbol A indicates a longitudinal dimension of the rear yoke (magnetic member)29p, and a reference symbol B indicates a longitudinal dimension of the magnets24p. In this example, supposed that the distance d is a maximum movable distance of the movable member22in one direction from the optical axis, a dimensional relation between the width A of the magnetic member29pand the width B of the magnets for drive24pis set as follows:
A≧(2×d+B).

That is, the width A (mm) is set to be larger than the width B (mm).

With this setting, even when the movable member22is displaced in the yaw direction by the maximum amount, as illustrated inFIG. 11B, the magnets24pare not moved on a left side over the rear yoke29p.

Here, in the case where A=B is set as in the example of prior art ofFIGS. 9A to 9C, when the movable member is displaced by the maximum amount in the yaw direction, that is, to the left side in the drawing, the rear yoke29pis moved to the left side over the magnets24p.

In focusing on the above-mentioned returning force, in comparison with the case where the rear yoke is not moved over the magnets as in this example, correspondingly to an amount, by which the rear yoke29pis moved over the magnets24p, due to the magnetic flux between the rear yoke29pand the magnets24p, the returning force for attracting the rear yoke29pto the right direction in the drawing increases. Therefore, the returning force110pin this example illustrated inFIGS. 11A to 11Cis lower than the returning force in the example of prior art.

Therefore, the rotational angle θ1in this example illustrated inFIGS. 11A to 11Cis lower than a rotational angle in the example of prior art. As a result, rotation is restricted.

Though, in the foregoing, the description is made regarding displacement in the yaw direction, also for displacement in the pitch direction, its structure is the same as the structure for displacement in the yaw direction except that a direction for arrangement is shifted by 90°.

The width A of a direction orthogonal to a direction in which the movable member is driven by the magnetic members29yand29pis larger than the width B of a direction orthogonal to a direction in which the movable member is driven by the magnets for drive24yand24p. In this case, the magnetic members29yand29pconstitute a horizontal driving portion (24y,28y, and29y) and a perpendicular driving portion (24p,28p, and29p), respectively.

In addition, the dimensional relation between the width A and the width B is not limited to the following relation:
A≧(2×d+B).

For example, it is sufficient to determine the most suitable value complying with a target performance under consideration of a size and a cost under the setting of A>B including A>(d+B). For example, it is sufficient that A≧(d+B) is set.

A relation of a rotational angle of the movable member22and an output of the position detecting means is the same as that of the first example.

In the foregoing, the exemplary fourth example according to the present invention is described. In this example, the returning force is reduced, which is generated due to the attraction force acting on the magnet24and the rear yoke29on an opposite side with respect to the driving direction of the movable member22. With this structure, the above-mentioned rotational moment108and the rotational angle θ1are reduced. Thus, rotation in the plane orthogonal to the optical axis of the movable member is restricted.

As a result, the thrust force needed for position correction is reduced in position feed-back control of the movable member22without an additional mechanical mechanism. Thus, the electric power consumption may be also reduced. Further, it is possible to obtain an image blur correction device excellent in micro-amplitude properties, a lens barrel provided with the image blur correction device, and an optical apparatus including the lens barrel.

Additionally, in this example, the returning force by the attraction force generated from the magnets for drive is reduced, and hence rotation of the correction lens in the plane orthogonal to the optical axis is easily restricted without one of an additional mechanical mechanism and an additional driving portion. In addition, rotation is restricted, and hence it is possible to reduce the electric power consumption needed for position feed-back control by rotation, and to obtain the image blur correction device excellent in micro-amplitude properties.

In this example, though the third group lens L3supported by the movable member22is driven by two driving portions, that is, the driving portion for the yaw direction and the driving portion for the pitch direction, the present invention is applicable to an embodiment in which three driving portions are employed to drive the third group lens L3supported by the movable member22.

In this case, it is preferred that, in the plane orthogonal to the optical axis, about the optical axis, the three driving portions be arranged at an interval of 120°, and that three actuators arranged corresponding to the three driving portions be independently driven in order to correct an image blur due to vibration such as hand movements.

Note that, needless to say, the present invention is not limited to those examples, and various modifications and changes are possible within a range of the gist of the present invention.

This application claims the benefit of Japanese Patent Application No. 2009-010536, filed Jan. 21, 2009, which is hereby incorporated by reference herein in its entirety.