JP2015064547A - Image stabilization unit - Google Patents

Abstract

Provided is a camera shake correction unit that can position a correction lens with high accuracy and that is compact and can be reduced in cost. A fixed frame 3 fixed in a lens barrel 13 and a correction lens are held and supported so as to be movable in a plane facing the fixed frame 3 and orthogonal to the optical axis when viewed from the optical axis direction. Lens frame 2, magnet members 51 a, 51 b, 51 c having drive magnets 511 a, 511 b, 511 c held by lens frame 2, cores 520 a, 520 b, 520 c held by fixed frame 3, and center core Including driving coils 524a, 524b, 524c wound around the sections 521a, 521b, 521c, and three axial gap type linear motors 5a, 5b, 5c for moving the lens frame 2 in a plane perpendicular to the optical axis . Hall elements 61a, 61b, 61c are mounted on the FPC 7 mounted on the fixed frame 3, and along the optical axis direction, the Hall elements 61a, 61b, 61c, magnet members 51a, 51b, 51c, and a driving coil 524a, 524b and 524c are arranged in this order. [Selection] Figure 2

Description

  The present invention relates to a camera shake correction unit including an axial gap type linear motor that moves a camera shake correction lens in order to prevent image shake caused by camera shake.

  In imaging optical equipment such as digital cameras, camera bodies and interchangeable lenses are generally equipped with an anti-shake mechanism in order to take high-quality photos as the taking lens lengthens and the zoom ratio increases. It has become. In other words, in a camera having a conventional camera shake correction function, a camera shake detection unit using an angular velocity sensor or the like detects a camera shake generated in the camera, and based on the detected amount, a correction lens or an image sensor that is a part of the photographing lens Is shifted, and the image pickup surface and the optical axis of the photographing optical system are displaced relative to each other to correct the shake of the image pickup surface.

  Conventionally, as an optical camera shake correction device, it has been proposed to move a correction lens (or an image sensor) in a two-dimensional direction on a plane perpendicular to the optical axis. For example, Patent Document 1 discloses a correction unit including a support frame that supports a lens or an image sensor, and a pair of permanent magnets that are fixed to the support frame and generate a magnetic field substantially parallel to the optical axis of the lens or the image sensor. And a support means for supporting the correction means so as to be movable in a two-dimensional direction within a plane substantially perpendicular to the optical axis, and provided in the support means for driving the correction means in two different directions within the plane. A pair of coils disposed around the magnetized surface of the permanent magnet and wound around an axis parallel to the optical axis, and a first surface that is a magnetized surface of the permanent magnet. A shake correction apparatus including a magnetic detection sensor that detects a position of the correction unit facing the opposite second surface is described.

  As another optical camera shake correction device, it has been proposed to translate a correction lens (or an image sensor) on a plane perpendicular to the optical axis and further rotate it. For example, Patent Document 2 discloses a movable member that holds a correction lens, a base member that constitutes a base portion of a unit, a base member, and a base member, in order to expand a region in which the linearity of Hall element output can be ensured without reducing driving force. A support member that supports the movable member in a translational and rotational manner on a plane substantially orthogonal to the optical axis of the correction lens, a position detection unit that detects the position of the correction lens, and the movable member on the optical axis. Three drive means for moving in a substantially orthogonal direction, the drive means at least a coil mounted on a substrate fixed to the base member, and a magnet provided at a position facing the coil in the movable member, It is described that the position detecting means is provided on the surface of the substrate on which the coil is not mounted.

  However, when a drive device (voice coil motor) having a coil and a drive magnet is used to drive the correction lens, a lock mechanism (centering mechanism) is provided to hold the correction lens in a predetermined position when the power is not supplied. Since it is necessary to provide the image stabilization apparatus, the camera shake correction apparatus has a complicated structure, which hinders downsizing and cost reduction.

Therefore, a camera shake correction device has been proposed in which the movable part is driven by the attractive force and repulsive force of an electromagnet instead of the voice coil motor. For example, Patent Document 3 uses a magnetic force generated between a first X magnet and a first Y magnet fixed to a fixed support substrate and a second X magnet and a second Y magnet fixed to a stage member. A stage device is described in which the stage member can be driven with less power than in the prior art using an electromagnet and an iron core by moving the stage member in the X and Y directions with respect to the fixed support substrate. .

Japanese Patent No. 3720473 Japanese Patent No. 5266091 Japanese Patent No. 5084308

  Since the stage apparatus described in Patent Document 3 requires two electromagnets in the X direction and the Y direction, respectively, the apparatus is increased in size and cost. In this structure, the gap between the first magnet and the second magnet due to the attraction force changes, and the attraction force does not change linearly in inverse proportion to the square of the gap between the yoke and the magnet. Control becomes difficult. In addition, since the Hall element cannot be placed at the center of the actuator, the position where the suction force is generated differs from the position of the Hall element, and if an inclination such as rotation occurs, an output signal that differs from the actual amount of movement is generated and the position shifts. The phenomenon expands.

  Accordingly, an object of the present invention is to provide a camera shake correction unit that can position the correction lens with high accuracy and is compact and can be reduced in cost.

  The camera shake correction unit of the present invention holds a fixed frame held in a lens barrel and a correction lens, and is movable in a plane facing the fixed frame and orthogonal to the optical axis when viewed from the optical axis direction. A lens frame to be supported, a mover having a permanent magnet (not including a heavy rare earth element) held by the lens frame, a core made of a magnetic material held by the fixed frame, and wound around the core It comprises an axial gap type linear motor that includes a drive coil and moves the shift frame in a plane orthogonal to the optical axis, and further comprises position detection means including a Hall element provided on the fixed frame. To do.

  The camera shake correction unit of the present invention holds a fixed frame fixed in a lens barrel and a correction lens, and is movable in a plane facing the fixed frame and orthogonal to the optical axis when viewed from the optical axis direction. A lens frame to be supported, and a magnet member fixed to the back yoke, held by the lens frame, and magnetized in the optical axis direction and having a pair of block magnets with different magnetization directions arranged at a predetermined interval; An axial gap linear that includes a core made of a magnetic material that is held by the fixed frame and has a plurality of slots, and a driving coil that is wound around the slots, and that moves the lens frame in a plane perpendicular to the optical axis. A configuration in which a near-motor and a magnetic field detection element supported by the fixed frame are provided, and the magnetic field detection element, the magnet member, and the drive coil are arranged in this order along the optical axis direction. It can be adopted.

  In the present invention, a Hall element is used as the magnetic field detection element, and the core has an E-shaped salient pole part, and the Hall element is overlapped with a center salient pole part when viewed from the optical axis direction. Can be installed.

  In the present invention, the Hall element can be mounted on a flexible printed board mounted on the fixed frame and fixed at a position on the back side of the magnetic circuit member and facing the permanent magnet.

  According to the present invention, by adopting a specific stator having a plurality of slots and using a structure that efficiently uses both suction and repulsion, a large thrust can be extracted and the magnetic field detection element can be separated from the driving coil. By providing them, the influence of the magnetic field generated from the drive coil can be reduced, so that highly accurate position control is possible.

  According to the present invention, since an axial gap type linear motor is used as the lens frame driving means, unlike the electromagnet system, the gap between the magnet and the core (or coil) does not change at the time of lens shift. In addition, the correction lens can be moved smoothly without play.

  According to the present invention, the magnetic attractive force in the axial direction (optical axis direction) does not necessarily provide a suction yoke or the like, and the attractive force always acts in the axial direction (optical axis direction). Even at times, the lens frame can be held at the magnetic neutral point (center).

  According to the present invention, since a motor capable of obtaining a high thrust even when using a permanent magnet that does not contain heavy rare earth elements is used, it is possible to realize cost reduction and stable production.

It is the schematic which shows the structure of the digital camera carrying a camera shake correction unit. It is a disassembled perspective view which shows the camera-shake correction unit concerning the 1st Embodiment of this invention. It is a top view which shows the positional relationship of a linear motor and a shift frame at the time of seeing FIG. 2 from an optical axis direction. It is an arrow line view at the time of seeing FIG. 2 from A direction. It is the BB sectional view taken on the line of FIG. It is CC sectional view taken on the line of FIG. (A) is sectional drawing to which the principal part of FIG. 6 was expanded, (b) is a figure which shows magnetic flux density distribution in a Hall element surface. It is a figure which shows the relationship between the gap | interval between drive magnets, and a maximum error amount. It is a figure which shows the relationship between the distance between a Hall element and a magnet part, the gap | interval between drive magnets, and a maximum error amount.

  The details of the present invention will be described with reference to the accompanying drawings.

[Digital camera]
A digital single-lens reflex camera (hereinafter simply referred to as a camera) 10 shown in FIG. 1 includes a body 11 including a solid-state imaging device (for example, a CCD) 12 that forms an optical image of a subject via an optical filter (not shown), and a plurality of bodies 11. And a lens barrel 13 having an imaging optical system 14 composed of the lens groups L1 to L4. In the present embodiment, a lens shift method is employed as a camera shake correction unit in order to make it possible to visually recognize the camera shake prevention function even while observing a subject on the viewfinder. With this lens shift method, when the camera shake correction lens group is displaced in the direction perpendicular to the optical axis, the aberration in the shifted state is corrected well, and the maximum lens shift amount corresponding to the maximum correction angle shake of the photographer's camera shake is appropriately set. It is important to make it a proper value. A lens group that satisfies these conditions may be selected as the correction lens group. For example, at least a part of the lenses constituting the fourth lens group L4 may be shifted as a camera shake correction lens.

  In the camera body 11, for example, camera shake amounts (angular accelerations) detected by the two gyro sensors 15 a and 15 b are input to the control circuit 16 in order to detect the vertical camera shake amount and the horizontal camera shake amount. Then, a drive current corresponding to the amount of camera shake is supplied to a drive circuit 17 of correction lens drive means (three axial gap type linear motors), which will be described later, built in the camera shake correction unit 1 to control the position of the correction lens. Thus, it is possible to obtain an image with little camera shake by shifting the incident optical axis. Further, the position signal of the correction lens is input to the control circuit 16 to perform feedback control.

[Image stabilization unit]
The configuration of the camera shake correction unit 1 will be described with reference to FIG. FIG. 2 shows directions of orthogonal coordinates of X, Y, and Z with the optical axis direction as the Z axis. The camera shake correction unit 1 includes a lens frame 2 having a correction lens (not shown) composed of one or a plurality of lenses, and a fixed frame 3 for holding the lens frame 2 in a lens barrel 13 (see FIG. 1). And an axial gap type linear motor (hereinafter simply referred to as “linear motor”) 5a, 5b, 5c for driving the lens frame 2 in a plane perpendicular to the optical axis. The camera shake correction unit 1 can keep the correction lens stationary at a position coincident with the optical axis during non-imaging. That is, in the camera shake correction OFF state in which the switch for operating the correction lens does not operate, the correction lens is held in a neutral state (coaxial with the optical axis) even when no power is supplied, and in the camera shake correction ON state in which camera shake correction can be performed, the linear motor 5a. At least one of 5b and 5c is driven to ensure a desired shift amount. Details of each part of the camera shake correction unit 1 are as follows.

(Lens frame and fixed frame)
The lens frame 2 is a ring-shaped member having ball receiving portions 20a, 20b, and 20c for holding a peripheral edge of a correction lens (not shown) and receiving a plurality of balls (spheres). The fixed frame 3 is a ring-shaped member formed so as to overlap the lens frame 2 when viewed from the A direction. A plurality of spherical bodies 4a, 4b, and 4c are interposed between the lens frame 2 and the fixed frame 3 when viewed from the optical axis direction, so that a plane perpendicular to the optical axis direction (Z direction) (X direction and (Surface including the Y direction orthogonal thereto) is supported so as to be movable in an arbitrary direction, so that sliding (friction) resistance is reduced, and minute angular shake can be corrected. The lens frame 2 and the fixed frame 3 are formed of a non-magnetic material (for example, engineering plastic). As the spheres 4a, 4b, and 4c, it is preferable to use a sphere made of a ferromagnetic material (for example, a steel ball) in order to enable easy incorporation, but a non-magnetic material (for example, austenitic stainless steel or ceramics). It is also possible to use a sphere consisting of

  3 and 4, the lens frame 2 is formed at equiangular intervals (120 °) along the circumferential direction, and has a rectangular magnet holding portion when viewed from the optical axis direction, and each magnetic circuit holding portion. Claw portions 21a, 21b, and 21c that hold the magnet members 51a, 51b, and 51c constituting the linear motors 5a, 5b, and 5c are formed on both sides of the motor. That is, since a pair of claw portions 21a, 21b, and 21c are formed on both sides of each magnet holding portion when viewed from the optical axis direction so as to sandwich the mover, the magnet member can be easily attached. be able to. Ball receiving portions 20 a, 20 b, and 20 c, one end of which is a protrusion that can be inserted into the fixed frame 3, are formed in the middle of each holding portion along the circumferential direction, and a boss portion 32 a formed on the fixed frame 3. , 32b, 32c arc-shaped relief portions 22a, 22b, 22c are formed.

  The fixed frame 3 is formed at equiangular intervals (120 °) along the circumferential direction, has armature holding portions 31a, 31b, and 31c that are rectangular when viewed from the optical axis direction, and is linearly connected to each armature holding portion. Armatures 52a, 52b, 52c constituting the motors 5a, 5b, 5c are mounted. Housing grooves 311a, 311b, and 311c for receiving a part of the air-core coil are formed on the back side (inner peripheral side) of each armature holding portion. Each armature 52a, 52b, 52c has a pair of female screw portions 33 formed on the surface of the fixed frame 3 facing the armature, and the tip of a machine screw 53 through which the armature is inserted is screwed therein. Thus, the fixed frame 3 is coupled.

  The fixed frame 3 is formed with circular holes 30a, 30b, 30c into which end portions of the ball receiving portions 20a, 20b, 20c are inserted at equal angular intervals (120 ° intervals) along the circumferential direction. Concentric holding holes 301a, 301b, and 301c are formed on the bottom surface of the circular hole. Each holding hole 301a, 301b, 301c is formed in a size that allows the sphere 4 to roll within a predetermined range. Therefore, after the sphere 4 is accommodated in each holding hole, the projecting portions 20a, 20b, and 20c of the lens frame 2 are inserted into the circular holes 30a, 30b, and 30c, respectively, and the sphere is interposed between the shift frame 2 and the fixed frame. Since 4 is interposed, the lens frame 2 is supported so as to be movable in the XY plane.

  Furthermore, a flexible printed circuit board (hereinafter referred to as FPC) 7 is attached to the fixed frame 3 in order to draw out wiring to the armature part and the position detection part. The FPC 7 includes a lead portion 72 connected to a power source and a circuit portion (both not shown), and a support portion formed in a trapezoidal shape as viewed from the optical axis direction, which is connected to one end thereof and has fixing holes at both ends. 70a, 70b, 70c and winding parts 71a, 71b wound around the fixed frame 3. Hall elements 61a, 61b, and 61c are mounted on one surface (surface on the armature side) of each support portion in order to perform position detection. After the Hall elements 61a, 61b, 61c are mounted on the side facing the fixed frame 3, the FPC 7 is fixed to the boss portions 32a, 32b, 32c by the machine screws 54, and the center of the Hall element is set to the center of the magnet member. Installed to match.

(Axial gap type linear motor)
As shown in FIGS. 2 to 4, linear motors 5 a, 5 b, 5 c for moving the correction lens are provided on magnet members (movable elements) 51 a, 51 b, 51 c fixed to the lens frame 2 and the fixed frame 3. Since the armatures (stator) 52a, 52b, and 52c are fixedly installed, the wiring is not routed by the movement of the linear motor, so that the coil can be prevented from being disconnected.

  The magnet members 51a, 51b, 51c fixed to the lens frame 2 holding the correction lens are respectively flat plate-like back yokes 510a, 510b, 510c made of a ferromagnetic material (for example, a steel material such as an SS material), and a thickness. For example, it has drive magnets 511a, 511b, and 511c that are magnetized in the direction (optical axis direction) and adjacent to magnetic poles of different polarities along the longitudinal direction, for example, a rectangular parallelepiped (or other shapes). Each drive magnet is fixed to magnet holding portions 21 a, 21 b, 21 c formed at a plurality of locations (three locations) on the outer peripheral side of the shift frame 2. As will be described later, the pair of drive magnets 511a are arranged with a predetermined gap (separated) so that the magnetic flux density linearly changes at the magnetic pole reversal part. Further, since the projected area of each of the driving magnets 511a, 511b, and 511c is formed to be smaller than the area of the core constituting the stator when viewed from the optical axis direction, the cogging torque is reduced and a smooth straight line is formed. It can be moved.

  The armatures 52a, 52b, 52c include a multi-slot type core and a coil wound around the slot. Referring to FIG. 6, the stator 50b includes an E-shaped core 520b made of a magnetic material having, for example, three salient poles, and a driving coil 524b wound around the central core portion 521b. Similarly to the stator 52b, the stators 52a and 52c have cores 520a and 520c having three salient poles, and the driving coils 524a and 524c are wound so as to surround the central core portions 521a and 521c among the cores. It has been turned. Each core 520a, 520b, 520c can be formed by laminating silicon steel plates, for example. A core formed of a dust core can be used instead of the laminated core. Each armature 52a, 52b, 52c is attached to an armature holding portion 31a, 31b, 31c formed at equiangular intervals (120 ° pitch) along the circumferential direction of the fixed frame 3, and then ends. The screw portion of the machine screw 53 is inserted into the groove portion 530 formed in the core portions 522 a, 523 a, 522 b, 523 b, 522 c, 523 c, and the tip is screwed into the female screw portion 33 to be fixed to the fixed frame 3.

  In the present invention, when viewed from the optical axis direction as shown in FIG. 3, it is preferable to make the magnet area smaller than the core area by the required amount of movement of the lens frame. For example, when the lens frame moves within ± 0.5 mm (within a radius of 0.5 mm) in the X and Y directions, the area of the magnet is {(X + (0.5 × 2)) mm rather than the area of the core. By making it smaller than the above} × {(Y + (0.5 × 2)) mm}, the magnet will be within the core area even if it moves to the end of the movable range, and will return to the origin. Thus, the cogging torque can be reduced and smooth movement can be performed.

The drive magnets 511a, 511b, and 511c can be formed of isotropic rare earth bonded magnets, for example. As an isotropic rare earth bonded magnet, isotropic rare earth magnet powder (for example, Nd-Fe-B magnet powder or Sm-Fe-N magnet powder) is bound with a resin (thermoplastic resin or thermosetting resin). Permanent magnets can be used. Each drive magnet is fixed to magnet holding portions 21 a, 21 b, 21 c formed at a plurality of locations (three locations) on the outer peripheral side of the shift frame 2. It includes a plurality of permanent magnets 321a to 321c provided at positions facing the plurality (three) of driving coils 31a to 31c. These permanent magnets 511a, 511b, and 511c are all magnetized in the thickness direction (optical axis direction), and are magnetized so that a pair of magnetic poles having different polarities exist on the surface facing the drive coil. . Further, flat back yokes 510a, 510b and 510c are provided on the surface of each magnet opposite to the driving coil. Since each permanent magnet 511a, 511b, 511c substantially does not contain heavy rare earth elements, price fluctuations are small and stable production of the motor is possible.

The rare earth bonded magnet used in the present invention contains rare earth magnet powder (the surface may be coated with a resin) and a binder resin for binding the rare earth magnet powder as essential components, for example, 64 to 88 kJ / m. ^{3 with} a maximum energy product of [8-11 MGOe]. The rare earth magnet powder is made of an alloy containing a rare earth element (R) containing Y and a transition metal (TM), and is a tetragonal compound of a rare earth element (R), boron (B), and a transition element (TM). An aggregate of R ₂ TM ₁₄ B type ₁ crystals is preferred, and may contain inevitable impurities that are difficult to remove in production. For example, SmCo _5, Sm SmCo-based alloy, such as _{2 TM 17, Nd-Fe-} B based alloy, Pr-Fe-B based alloys, Nd-Pr-Fe-B based alloy, Ce-Nd-Fe-B Alloy, R—Fe—B alloy such as Ce—Pr—Nd—Fe—B alloy, Sm—Fe—N alloy such as Sm ₂ Fe ₁₇ N _3, etc. Mixed magnet powders (for example, Nd—Fe—B isotropic magnet powder and Sm—Fe—N isotropic magnet powder) may be used.

  In the R-TM-B alloy, examples of the transition metal (TM) include Fe, Co, Ni, and the like, and one or more of these can be included. Normally, Fe is used as the transition metal, but a part of Fe may be substituted with another transition metal such as Co or Ni. Further, in order to improve the magnetic properties, the magnet powder may contain B, Al, Mo, Cu, Ga, Si, Ti, Ta, Zr, Hf, Ag, Zn or the like as necessary. it can.

  As said rare earth element (R), 1 type (s) or 2 or more types, such as Y, La, Ce, Pr, Nd, Sm, Gd, Tb, can be used, Nd is preferable. In addition, even if part of Nd in the magnet raw material is replaced with Pr, there is little influence on the magnetic properties, and a rare earth raw material (zidym) mixed with Nd and Pr is available at a relatively low cost. , Pr may be included. However, in the present invention, since heavy rare earth elements such as Dy, Tb or Ho are limited in production area and expensive, the magnet raw material used for the production of magnet powder does not contain Dy, Tb and Ho as much as possible. It is necessary.

  The above rare earth magnet powder is kneaded with a binder resin and then cooled and solidified to obtain a compound as a raw material for the bonded magnet. The rare earth magnet powder can generally contain 85-98% by mass in the compound. A bonded magnet is obtained by molding this compound by a technique such as compression molding or injection molding. In the case of compression molding, the binder resin is a thermosetting resin such as an epoxy resin, a phenol resin, a silicone resin, or a polyester resin (a curing agent is added if necessary). In the case of injection molding, the binder resin is , PPS, PA and other thermoplastic resins are used.

If the permanent magnet has a maximum energy product of 64 to 88 kJ / m ³ (8 to 11 MGOe), it can constitute a compact linear motor and obtain the thrust necessary for driving the correction lens. It is also possible to use permanent magnets other than rare earth bonded magnets (for example, anisotropic sintered ferrite magnets).

(Magnetic field detection element)
When the correction lens is driven by the linear motors 5a, 5b, and 5c, the fixed frame is used to detect the movement amount of the shift frame 2 in order to perform feedback control based on the movement amount of the lens frame 2 that supports the correction lens. 3, a magnetic field detection element (position sensor) for detecting the magnetic field of each permanent magnet is provided. In this embodiment, as shown in FIGS. 3 to 6, on the back side of the support portions 70 a, 70 b, 70 c facing the fixed frame 3 of the FPC 7 and at the center (space portion) of the drive magnets 511 a, 511 b, and 511 c. Hall elements 61a, 61b and 61c are provided so as to face each other. When attention is paid to the Hall element 61b, the Hall element 61b is arranged as shown in FIG. Here, on the surface of the Hall element 61b, the magnetic flux density changes from one end to the other end of the driving magnet 511b as shown in FIG. 7B. That is, at the zero cross point (middle of the magnet) P ₀ , the magnetic pole reverses from the N pole (S pole) to the S pole (N pole) (magnetic flux density = 0), and within a predetermined length L ₀ across P _0. The magnetic flux density changes linearly.

  In the present invention, by using a GaAs Hall element and driving at constant current operation, the temperature characteristics of the output voltage are reduced (about 0.06% / ° C) and the environmental conditions (ambient temperature, etc.) are reduced. This is advantageous for accurate positioning control. A constant current circuit can be formed by connecting an external resistor in series with the input resistance of the Hall element, making the external resistance sufficiently larger than the input resistance and sufficiently increasing the applied voltage.

Since the hall element outputs a voltage proportional to the magnetic flux density, as the movement of the actuating magnet is within the range specified in the L _0, the size of the magnet unit (Lm, Lg, tm, tb ) and the Hall element and the magnet portion If the distance g is set appropriately, a voltage proportional to the amount of movement of the movable magnet (change in magnetic force) can be output to the control circuit, and the linearity of the output voltage can be improved. Accurate positioning can be performed. For example, when the distance g between the detection surface of the Hall element and the magnet portion is set to 0.1 to 0.3 mm, Lg is in a range of g × (5 to 20) mm. Here, when Lg is narrowed, the gradient of the magnetic flux density becomes steep and the output gain increases, but the noise also increases. On the other hand, as Lg becomes wider, the gradient of the magnetic flux density becomes gentler and the output gain is reduced, but the noise is reduced. Here, for example, when an isotropic rare earth bonded magnet (for example, having a maximum energy product of 80 to 88 kJ / m ³ [10 to 11 MGOe]) is used and the moving range is 1 mm, the distance g is about 0.3 mm. In order to improve the linearity of the Hall element output, it is preferable to set Lg to about 1.7 mm. (See the experimental example below)

  As described above, in the camera shake correction unit 1, the Hall element 61 b is less likely to be affected by the magnetic field of the driving coil, as shown in FIGS. 5 and 6, along the optical axis direction (imaged from the subject side). Toward the element side), the Hall element 61b, the magnet member 51b, and the driving coil 524b are arranged in this order.

(Linear motor operation)
For example, when the driving coil 524b of the linear motor 5b is energized to generate a magnetic pole having the polarity as shown in FIG. 7A on the end surface of the core 520b, the driving magnet 511b of the magnet member 51b has an end portion. The magnet member 51b moves in the direction of arrow S1 because it is attracted to the S pole of the core portion 522b and receives a repulsive force from the S pole of the central core portion 521b, and further receives a repulsive force from the S pole of the end core portion 523b. . On the other hand, when the direction of the current supplied to the driving coil 524b is reversed, a magnetic pole having the polarity shown in parentheses in FIG. 7 is generated on the end surface of the core 520b, and the magnet member 51b moves in the direction of arrow S2. That is, the mover (magnet member 51b) of the linear motor 5b can move in the radial direction on a plane perpendicular to the optical axis direction. The other linear motors 5a and 5c can be driven in the same manner as the linear motor 5b. Accordingly, since the magnitude and direction of the thrust can be adjusted by changing the polarity and / or magnitude of the current supplied to each driving coil, the shift frame can be obtained by synthesizing the thrust generated in each linear motor. 2 can be driven in any direction within a plane perpendicular to the optical axis. The other linear motors 5a and 5c are also driven in the same manner as described above. This driving amount is fed back to the control circuit, and the correction lens can be moved to the target position.

[Position detection operation]
When focusing on the linear motor 5b in the above-described camera shake correction apparatus, in the initial state where the camera shake correction operation is not performed, as shown in FIG. 7A, the zero cross point (boundary between the N pole and the S pole) of the drive magnet 511b. ) P ₀ exists at a position that coincides with the center of the Hall element 61b. As shown in FIG. 7B, the magnetic flux density distribution of the driving magnetic pole is approximated by a substantially sinusoidal distribution. The magnetic flux density changes linearly in a range (L ₀ ) of about 1 mm, for example, with the zero cross point P ₀ as the center. Therefore, since the output voltage of the Hall element also changes linearly, the movement amount of the correction lens can be accurately detected.

  In a lens shift type image stabilization unit in which a correction lens is driven by a motor (actuator), when a magnetic sensor is used as a position detection means, the maximum movement distance of the correction lens is ± (0.5 to 1.. It is generally set in the range of 0) mm, and within this range, a difference (linearity) between the actual movement amount and the movement amount corresponding to the output voltage of the magnetic field detection element is required to be small, and the Hall element It is desirable that the linearity be within 0.04 mm. Therefore, the following experiment was performed using the camera shake correction unit according to the present embodiment.

(Experimental example)
In the camera shake correction unit shown in FIG. 1, the maximum of isotropic rare earth bonded magnets (80 to 88 kJ / m ³ [10 to 11 MGOe]) as drive magnets (Lm = 8.75 mm, tm = 4 mm, width = 5.8 mm). And a back yoke made of SS material (tb = 1.0 mm) and a drive coil (self-bonded wire, wire diameter = An axial gap linear motor was constructed by winding 0.15 mm (φ0.15 mm, number of turns = 424 T). The maximum error amount was measured by changing the distance g between the Hall element and the magnet part and the gap Lg between the magnet parts.

  First, the maximum error amount was measured when the distance g between the Hall element and the magnet portion was set to 0.3 mm and the gap Lg between the magnet portions was changed between 0 and 1.7 mm. The result is shown in FIG. FIG. 8 shows that the maximum error amount can be reduced as the gap Lg between the magnet portions increases. However, since the output voltage decreases as the gap Lg between the magnet portions increases, it is preferable to select Lg in the range of 1.5 to 2.0 mm.

  Next, when the distance g between the Hall element (detection surface) and the magnet member is changed in the range of 0.3 to 1.0 mm, and the gap Lg of the magnet portion is changed in the range of 0 to 1.7 mm. The maximum amount of error was measured. The result is shown in FIG. In the figure, curves g1 = Lg: 0 mm, g2 = Lg: 0.5 mm, g3 = Lg: 0.8 mm, g4 = Lg: 1.0 mm, g5 = Lg: 1.2 mm, g6 = Lg: 1.5 mm , G7 = Lg: 1.7 mm, respectively. From FIG. 9, when g is 1.2 mm or less (curves g1 to g5), the maximum error amount decreases as the distance g between the Hall element and the magnet portion increases, and when g is 1.5 mm or more (curves g6 and g7), It can be seen that the maximum error amount increases as the distance g between the element and the magnet portion increases. However, from the results of FIG. 8, Lg is preferably 1.5 mm or more (see g6 and g7), and g is preferably 0.5 mm or less and 0.3 mm or more.

[Image stabilization]
In the present invention, for example, the camera shake correction operation can be executed by the following procedure (see FIG. 1). The camera shake amount detectors (gyro sensors) 15 a and 15 b detect camera shake amounts (camera body shakes, for example, angular velocity) and input the control circuit 16. In the control circuit 16, the shake amount calculation unit calculates an angle from this shake amount (performs calculation processing such as integration), the shooting mode determination unit determines the shooting mode from the lens position information and the shutter and mode switch information, and then A correction amount calculation unit calculates a camera shake correction amount (camera shake angle × focal length × α), and an operation of driving the linear motor by this correction amount is executed. This correction operation (feeds back the correction lens movement amount to the control circuit and moves the correction lens to the target position) shifts the incident optical axis that has fluctuated due to camera shake in the optical axis direction, thereby correcting camera shake. Optical images can be obtained.

According to the present embodiment, the following effects can be obtained.
(1) Since the armature has two poles and three slots, the cogging torque is reduced, the lens frame can be moved smoothly, suction and repulsion can be used efficiently, and a large thrust can be extracted.

(2) Since the magnet area is made smaller than the core area by the required amount of movement of the lens frame, a uniform magnetic attractive force is generated within the range in which the shift frame can be moved, thereby enabling smooth movement. Become.

(3) Since the position detection element is provided at a position facing the central core portion of the linear motor and not easily affected by the magnetic field of the driving coil, the movement amount of the lens frame is detected at the center of movement. In combination with this, position control with high accuracy becomes possible.

(4) Since the three linear motors are arranged concentrically and at equal angular intervals when viewed from the optical axis direction, the magnetic attractive force in the axial direction can be kept uniform, and the movable part is supported by the three spheres. Since no guide means such as a guide rail is required, the structure is simplified and the correction lens can be moved stably.

1: Image stabilization unit,
2: lens frame, 20a, 20b, 20c: ball receiving portion, 21a, 21b, 21c: magnet holding portion, 22a, 22b, 22c: escape portion,
3: Fixed frame, 30a, 30b, 30c: Ball receiving part, 301a, 301b, 301c: Holding hole, 31a, 31b, 31c: Armature holding part, 311a, 311b, 311c: Coil housing part, 32a, 32b, 32c : Boss part, 33: Female thread part,
4, 4a, 4b, 4c: sphere,
5a, 5b, 5c: axial gap type linear motor,
51a, 51b, 51c: magnet member, 510a, 510b, 510c: back yoke, 511a, 511b, 511c: driving magnet, 512a, 512b, 512c: notch,
52a, 52b, 52c: Armature, 520a, 520b, 520c: Core, 521a, 521b, 521c: Central core portion, 522a, 522b, 522c, 523a, 523b, 523c: End core portion, 524a, 524b, 524c: Driving coil, 530: groove, 53, 54: machine screw,
6: Position sensor, 61a, 61b, 61c: Hall element,
7: FPC, 70a, 70b, 70c: support part, 71a, 71b: winding part, 72: lead part,
10: camera, 11: body, 12: imaging unit, 13: lens barrel, 14: imaging optical system, L1, L2, L3, L4: lens group, 15a, 15b: gyro sensor, 16: control circuit, 17: Driving circuit

Claims (4)

A fixed frame held in the lens barrel;
A lens frame that holds the correction lens and is supported so as to be movable in a plane that faces the fixed frame and is orthogonal to the optical axis when viewed from the optical axis direction;
A mover having a permanent magnet (not including a heavy rare earth element) held by the shift frame, a core made of a magnetic material held by the fixed frame, and a driving coil wound around the core, Along with an axial gap type linear motor that moves the lens frame in a plane perpendicular to the optical axis,
A camera shake correction unit comprising position detection means including a Hall element provided on the fixed frame. A fixed frame held in the lens barrel;
A lens frame that holds the correction lens and is supported so as to be movable in a plane that faces the fixed frame and is orthogonal to the optical axis when viewed from the optical axis direction;
Three axial gap type linear motors that move the lens frame in a plane perpendicular to the optical axis, and a position detection member that is supported by the fixed frame and detects a moving distance of the lens frame;
The axial gap type linear motor includes three pairs of permanent magnets (not including heavy rare earth elements) held on the lens frame, fixed to a back yoke, and held at equiangular intervals along the circumferential direction. An axial member that includes a magnet member, a core made of a magnetic body having a plurality of slots held by the fixed frame, and a driving coil wound around the core, and moves the lens frame in a plane orthogonal to the optical axis Gap type linear motor,
The camera shake correction unit according to claim 1, wherein the position detection member includes a magnetic field detection element that is fixed to the side of the magnetic circuit member opposite to the drive coil and detects a magnetic field of the permanent magnet.   The Hall element is used as the magnetic field detection element, and the core has an E-shaped salient pole part, and the Hall element is installed so as to face a central salient pole part. 2. The image stabilization unit according to 2.   The camera shake correction unit according to claim 3, wherein the hall element is mounted on the fixed frame and mounted on a flexible printed board having a support portion facing the fixed frame.

Images