JP2007264678A - Lens barrel, photographing device and observation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens barrel capable of making energizing force for energizing a shift frame to a shift base side effectively act and making the driving force of the shift frame efficiently act on the shift frame. <P>SOLUTION: The shift frame holding a shake correction lens is energized to the shift base side by magnetic attractive force acting between a magnet (18p) and a yoke (21p). The yoke is equipped with a projection part (21pa) projecting to the magnet side, and the projection part is positioned on a boundary in two-pole magnetization of the magnet in such a state that the center of the shake correction lens is aligned with an optical axis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image blur correction apparatus that shifts a lens in a plane orthogonal to an optical axis in order to correct image blur caused by so-called camera shake. For example, a lens barrel, a video camera, a digital still camera, etc. The present invention relates to a shake correction apparatus suitable for being incorporated in an observation apparatus such as an apparatus, binoculars, or an astronomical telescope.

  In order to prevent image blur due to camera shake, etc., which is likely to occur during hand-held shooting, various devices have been proposed that detect shake information from cameras and binoculars and optically cancel the shake according to the detection results to achieve shake correction. Has been.

  For example, Japanese Patent Laid-Open No. 11-305277 proposes a so-called shift type shake correction apparatus that performs shake correction by shifting a shake correction lens group in a plane orthogonal to the optical axis among a plurality of lens groups. .

  In the shake correction device according to this proposal, three pins are press-fitted in the radial direction into the shift member that holds the shake correction lens group, and these are inserted into the elongated holes formed at three locations in the circumferential direction of the fixing member that is the device body. The three pins are fitted with a certain gap to guide the shake correction lens group so that it can be shifted in the plane orthogonal to the optical axis.

  Further, in this shake correction device, by using a magnetic attraction force acting between the magnet and the ferromagnetic body, the pin is pressed against the elongated hole portion in one direction in the optical axis direction, thereby causing a galling in the guide portion. It prevents rattling and tilting of the shake correction lens group associated therewith. Thereby, the maintenance of optical performance and the reduction of the operation sound caused by the rattling of the guide portion during driving are achieved.

  Further, in the shake correction device proposed in Japanese Patent Laid-Open No. 6-289465, a flexible board that connects a circuit board provided on a fixed member and a coil provided on a shift member has been devised based on the shape and arrangement of the extension portion. The load in the optical axis direction and the shift direction is reduced to prevent adverse effects on the driving of the shift member.

  Further, in the shake correction device proposed in Japanese Patent Application Laid-Open No. 10-319465, the fixed member is used for the purpose of eliminating the shakiness in the optical axis direction between the fixed member and the shift member and reducing the driving resistance of the shift member with respect to the fixed portion. The above-mentioned object is achieved by disposing a rollable ball between the member and the shift member and pressing the shift member against the fixed member via the ball by a spring biasing force.

Further, this shake correction apparatus employs a configuration in which the shift member is guided in the shift direction by the rotation of the ball, and the rotation of the shift member around the optical axis is prevented by the spring.
JP-A-11-305277 JP-A-6-289465 JP-A-10-319465

  In recent years, imaging devices and observation devices equipped with lens barrels have been required to be smaller and have a less protruding design in order to improve portability and storage. Therefore, it is necessary to further downsize the shake correction device.

  However, as the lens barrel is reduced in size, the space for drawing the flexible substrate connecting the main body or the fixing member and the shift member of the shake correction device is remarkably limited. As a result, it is difficult to sufficiently reduce the rigidity of the flexible substrate. It becomes. For this reason, it is difficult to reduce the elastic force in the optical axis direction generated in the flexible substrate to a level where there is no problem only by devising the shape and arrangement of the flexible substrate as shown in the above-mentioned JP-A-6-289465. Become.

  Therefore, as proposed in Japanese Patent Laid-Open No. 11-305277, even if the shift member is biased with an appropriate force in the optical axis direction by using a magnetic attractive force, the elastic force in the optical axis direction of the flexible substrate is used. The shift member pin is pushed too hard against the long hole due to the variation in the friction, resulting in very large friction, and on the contrary, the bias due to the magnetic attraction force is canceled and the shift member is driven. It will adversely affect.

  On the other hand, in an image sensor such as a CCD that converts an object image formed on a focus surface by a photographing optical system into an electric signal, an element with a smaller pixel pitch can be manufactured due to advancement of semiconductor microfabrication technology. It is coming.

  As a result, the optical system can be further reduced in size by forming the same number of pixels in a smaller area, and the resolution of the optical system can be further increased due to the increase in the number of pixels by the same area or area expansion. The flow of is occurring.

  In the former, since the shift movement amount of the shake correction lens group for correcting the same amount of shake is substantially proportional to the imaging area, a finer movement is required, and moreover, the space for drawing the flexible substrate is reduced.

  In the latter case, if the smaller shake cannot be corrected, the resolution deteriorates. Therefore, it is necessary to reduce the frictional force generated in the guide portion so that the shift member can be driven minutely.

  In either case, the required accuracy with respect to the tilt of the shake correction lens group becomes higher.

  Further, in the shake correction apparatus proposed in the above Japanese Patent Laid-Open No. 10-319465, since the ball is held by the holding member so that the position does not change with respect to the fixed member, the ball and the shift member are guided by rolling. However, since the ball rotates at a position held by the holding member, a sliding frictional force is generated between the ball and the fixing member and between the ball and the shift member.

  For this reason, the urging force for eliminating the play due to the spring is limited to the minimum necessary force to pinch the ball, and the shift member is caused by a slight acceleration in the optical axis direction in which the inertial force exceeding the urging force acts on the shift member. Floating from the ball, the deterioration of the optical performance due to the tilt of the shake correction lens group, and the generation of noise due to the hitting sound of the ball become a problem.

  For example, when a shift member having a weight of 4 g is urged by a force of 4 gf, the shift member floats off the ball only by applying an acceleration of 1 G or more.

  Further, since the rotation of the shift member around the optical axis by the spring depends on the pulling force of the spring, the rotation cannot be completely stopped and only the function of suppressing the rotation can be exhibited.

  In particular, in the configuration of the means for detecting the position of the shift member proposed in the embodiment, the output value of the position detection means changes due to rotation around the optical axis. Depending on the positional relationship between the force generation position and the center of gravity of the shift member, and the connection position and shape of the flexible board connected to the coil on the shift member, the shift member rotates around the optical axis with the shift drive. There is a problem that the shake correction lens group cannot be driven to an accurate position for shake correction.

  Therefore, in the present invention, by holding and guiding the shift frame without stagnation, noise such as a hitting sound at the guide portion is not generated, the tilt of the shake correction lens is extremely small, and the optical performance is excellent. The driving frictional force at the time of shake correction can be made extremely small by the ball rolling guide to increase the biasing force that acts on the shift frame so that it is not affected by the elastic force in the optical axis direction of the flexible substrate. An object of the present invention is to provide a lens barrel that can be used.

  In order to achieve the above object, in the present invention, a shake correction lens, a shift frame that holds the shake correction lens and is movable in a direction orthogonal to the optical axis, and a movement of the shift frame in the optical axis direction are regulated. A shift base, a roll that is sandwiched between the shift frame and the shift base, and a rollable ball, a limiting portion that limits the movement of the ball within a predetermined range by contact with the ball, the shift frame, and the shift base Drive means for driving the shift frame in a direction orthogonal to the optical axis by energizing the coil, the magnet having a two-pole magnetized magnet held on one of them and a yoke and a coil held on the other of the shift frame and the shift base And the shift frame is urged to the shift base side by a magnetic attractive force acting between the magnet and the yoke, and the yoke protrudes toward the magnet side. Be equipped And, in the state where the center of the shake correction lens coincides with the optical axis, the protruding portion is characterized by being located at the boundary of the two poles of the magnet.

  According to the present invention, the urging force (suction force) that urges the shift frame toward the shift base effectively acts, or the driving force of the shift frame acts on the shift frame efficiently. Is possible.

  In addition, by forming the ball from a material that does not easily generate a magnetic action, the ball is not attracted by the magnet of the driving means, thereby preventing the position of the ball from being displaced due to the attraction force, and the assembly of the device is deteriorated. It is good to prevent.

  Further, the biasing force of the shift frame toward the shift base due to the magnetic attraction between the magnet and the yoke can be made to be 5 times or more the weight of the shift frame including the shake correction lens. This makes it possible to avoid the influence of the elastic force in the optical axis direction from the flexible substrate that connects the shift base and the shift frame in the actual use of the lens barrel, and between the shift frame and the shift base. It is possible to perform a reliable play.

  Further, in the above invention, the lubricating oil having a viscosity capable of holding the ball on the contact surface between the shift frame and the shift base and the ball without being biased by the magnetic attraction between the magnet and the yoke. It is good to apply.

  As a result, it is possible to further reduce the friction between the ball, the shift frame, and the shift base, and for example, a large inertial force in the optical axis direction acts on the shift frame so that the shift frame is magnetically Even if the ball floats off the ball against the suction action, the ball is held by the viscosity of the lubricating oil and can be prevented from being easily displaced.

  According to the present invention, the urging force (suction force) that urges the shift frame toward the shift base effectively acts, or the driving force of the shift frame acts on the shift frame efficiently. Is possible.

  1 and 2 show the configuration of a lens barrel provided with a shake correction apparatus that is an embodiment of the present invention. FIG. 1 is an exploded perspective view of the lens barrel, and FIG. 2 is a sectional view of the lens barrel. This lens barrel is used in a photographing apparatus such as a video camera.

  The optical system of this lens barrel is a variable magnification optical system having a convex / concave / convex / convex four-group configuration in order from the subject or the observation object side.

  L1 is a fixed first group lens, L2 is a second group lens that moves in the direction of the optical axis and performs a zooming operation, and L3 is a third group lens that moves in the plane orthogonal to the optical axis and performs a shake correction operation (shakeout). L4 is a fourth lens group that moves in the optical axis direction and performs a focusing operation.

  Reference numeral 1 denotes a fixed barrel that holds the first group lens L1, 2 denotes a variable magnification moving frame that holds the second group lens L2, and 3 denotes a shift unit that allows the shift lens L3 to move within the plane orthogonal to the optical axis. Reference numeral 4 denotes a focusing moving frame that holds the fourth group lens L4, and 5 denotes a rear barrel to which an image pickup device such as a CCD is fixed.

  Two guide bars 6 and 7 are positioned and fixed between the fixed barrel 1 and the rear barrel 5. The variable magnification moving frame 2 and the focusing moving frame 4 are supported by the guide bars 6 and 7 so as to be movable in the optical axis direction.

  The variable magnification moving frame 2 and the focusing moving frame 4 are each fitted to one guide bar by a sleeve portion having a predetermined length in the optical axis direction, thereby preventing the optical axis direction from falling down. Then, by engaging the other guide bar with the U groove, rotation around the one guide bar is prevented.

  The shift unit 3 is positioned between the fixed lens barrel 1 and the rear lens barrel 5 and sandwiched between them, and is fastened and fixed from behind by three screws.

  Reference numeral 8 denotes an aperture unit that changes the aperture diameter of the optical system, and moves the aperture blades in opposite directions to change the aperture diameter.

  Reference numeral 9 denotes a stepping motor (hereinafter referred to as a focus motor) that drives the fourth group lens L4 in the optical axis direction to perform a focusing operation, and has a lead screw 9a coaxial with the rotating rotor. A rack 4a attached to the focusing moving frame 4 is engaged with the lead screw 9a, and the focusing moving frame 4 (fourth group lens L4) is driven in the optical axis direction by rotating the rotor and the lead screw 9a. The The focus motor 9 is fixed to the rear barrel 5 with two screws.

  Note that the torsion coil spring 4b disposed between the focusing moving frame 4 and the rack 4a causes the focusing moving frame 4 to move in the guide bar radial direction with respect to the guide bars 6 and 7, and the rack 4a to the focusing moving frame 4. On the other hand, the rack 4a is biased in the direction of the optical axis and further in the meshing direction with the lead screw 9a, thereby eliminating backlash at each part.

  Reference numeral 10 denotes a stepping motor (hereinafter referred to as a zoom motor) that drives the second group lens L2 in the optical axis direction to perform a zooming operation, and includes a rotating rotor and a coaxial lead screw 10a. The lead screw 10a meshes with a rack 2a attached to the variable magnification moving frame 2, and the variable magnification moving frame 2 (second group lens L2) is driven in the optical axis direction by rotating the rotor and the lead screw 10a. The The zoom motor 10 is fixed to the fixed barrel 1 with two screws.

  Note that the torsion coil spring 2b disposed between the variable magnification moving frame 2 and the rack 2a causes the variable magnification moving frame 2 to move in the guide bar radial direction with respect to the guide bars 6 and 7, and the rack 2a to the variable magnification moving frame 2. On the other hand, the rack 2a is biased in the optical axis direction and further in the meshing direction with the lead screw 10a, thereby eliminating backlash at each part.

  Reference numeral 11 denotes a focus reset switch composed of a photo interrupter, which detects the switching between light shielding and light transmission due to movement of the light shielding portion 4c formed in the focusing moving frame 4 in the optical axis direction and outputs an electrical signal. A control circuit (not shown) determines whether or not the fourth group lens L4 is located at the reference position based on the electrical signal from the focus reset switch 11. The focus reset switch 11 is fixed to the rear barrel 5 with a single screw.

  Reference numeral 12 denotes a zoom reset switch composed of a photo interrupter, which detects the switching between light shielding and light transmission due to movement of the light shielding portion 2c formed in the variable magnification moving frame 2 in the optical axis direction and outputs an electrical signal. A control circuit (not shown) determines whether or not the second group lens L2 is located at the reference position based on the electrical signal from the zoom reset switch 12. The zoom reset switch 12 is fixed to the fixed barrel 1 with a single screw.

  Next, the configuration of the shift unit (shake correction device) 3 that enables the shift lens L3 to move within the plane orthogonal to the optical axis will be described in detail with reference to FIGS. FIG. 3 shows a state in which the shift unit 3 is disassembled as viewed from the rear side.

  Reference numeral 13 denotes a shift base that constitutes the front main body of the shift unit 3, and is fixed between the fixed barrel 1 and the rear barrel 5.

  Reference numeral 15 denotes a shift frame that holds a shift lens L3. The shift frame 15 is used to correct image blur due to shake in the pitch direction (change in the angle of the camera in the vertical direction) and to shake in the pitch direction and yaw direction ( In order to correct the image shake due to the angle change in the lateral direction of the camera, it can be shifted with respect to the shift base 13 in the plane perpendicular to the optical axis in the yaw direction.

  Reference numerals 16 a, 16 b, and 16 c denote three balls sandwiched between the shift base 13 and the shift frame 15. These balls 16a, 16b, and 16c are formed of a material such as SUS304 (austenitic stainless steel) so as not to be attracted by a driving magnet that will be described later.

  The balls 16a, 16b, and 16c are in contact with the surfaces 13a, 13b, and 13c on the shift base 13 and the surfaces 15a, 15b, and 15c of the shift frame 15, respectively. These three contact surfaces are surfaces perpendicular to the optical axis of the optical system. When the nominal diameters of the three balls 16a, 16b, and 16c are the same, the optical axis direction of the three contact surfaces is the same. By suppressing the mutual difference between positions, the shift frame 15 can be held and shifted while maintaining a posture perpendicular to the optical axis.

  Reference numeral 17 denotes a sensor base constituting the rear main body, the position of which is determined by two positioning pins and coupled to the shift base 13 by two screws.

  Next, driving means for driving the shift frame 15 to shift will be described. The driving means in the pitch direction and the yaw direction and the position detecting means described later have the same configuration and only have a phase difference of 90 degrees around the optical axis. Therefore, here, in the pitch direction shown in FIG. The drive means and position detection means will be described. Further, regarding the reference numerals indicating the components in the drawing, P is attached to the components in the pitch direction, and Y is attached to the components in the yaw direction.

  Reference numeral 18p denotes a driving magnet magnetized in two radial directions with respect to the optical axis, 19p denotes a back yoke for closing the magnetic flux in the optical axis direction front side of the driving magnet 18p, and 20p is attached to the shift frame 15 by bonding. The fixed coil 21p is a yoke (yoke in the claims) for closing the magnetic flux on the rear side in the optical axis direction of the driving magnet 18p. The yoke 21p has substantially the same projected shape as the drive magnet 18p in the optical axis direction.

  Reference numeral 14p denotes a member for positioning the yoke 21p. The position of the yoke 21p is determined by the positioning member 14p and is fixed to the back surface of the coil 20p.

  The drive magnet 18p and the back yoke 19p are fixed to the shift base 13, and the yoke 21p is fixed to the shift frame 15 together with the coil 20p. The drive magnet 18p, the back yoke 19p, and the yoke 21p form a magnetic circuit. When a current is passed through the coil 20p disposed in the magnetic circuit, the Lorentz force due to the repulsion between the magnetic lines generated in the magnet and the coil in a direction substantially perpendicular to the magnetization boundary of the two-pole magnetization in the driving magnet 18p. Occurs, and the shift frame 15 shifts.

  Since the driving means having such a configuration is provided with respect to the pitch direction and the yaw direction, it is possible to give the shift frame 15 driving force in the pitch direction and the yaw direction substantially orthogonal to each other in the plane orthogonal to the optical axis. it can.

  That is, the present embodiment is a so-called moving coil type shift unit in which a coil is disposed in a gap of a magnetic circuit including a magnet, and the shift frame 15 (shift lens L3) is driven to shift together with the coil by energization of the coil.

  Further, a magnetic attraction action occurs between the driving magnet 18p and the yoke 21p, and the attraction force attracts the yoke 21p toward the driving magnet 18p. That is, the magnetic frame and the balls 16a to 16b are arranged so that the resultant force in the magnetic circuit in the pitch direction and the yaw direction works inside the three balls 16a to 16b, so that the shift frame 15 is moved to the three balls 16a. It is possible to urge the shift base 13 with ˜16c interposed therebetween.

  Further, between the three balls 16a to 16c and the contact surfaces of the shift base 13 and the shift frame 15, the balls 16a to 16c can be moved to the shift base 13 and the shift frame 15 without being biased by the suction force. Lubricating oil having a viscosity that does not easily fall off from the contact surface is applied. Thereby, even if the inertia force exceeding the said attraction | suction force acts on the shift frame 15, and the contact surface of the shift frame 15 will be in the state which floated from the ball | bowl 16a-16c, the position of ball | bowl 16a-16c will shift | deviate easily. Can be prevented. Further, the biasing force by the magnetic circuit in the pitch direction and the yaw direction is at least five times the weight of the shift frame 15 including the shift lens L3, so that a favorable biasing state can be maintained during actual photographing. it is conceivable that.

  Next, the state at the time of the drive of the shift frame 15 is demonstrated using Fig.4 (a)-(c). 4 (a) and 4 (b) show only a part of the drive means described above. In the state of FIG. 4A, the optical axis of the shift lens L3 substantially coincides with the optical axes of other lenses in the lens barrel, and the shift frame 15 is in the neutral position in the pitch direction and the yaw direction. Yes.

  A protruding portion 21pa is formed on the yoke 21p by half punching, and the position thereof is located at the boundary of the two-pole magnetization of the driving magnet 18p. At this time, since the protruding portion 21pa is at a substantially equal distance from both magnetic poles of the two-pole magnetization of the driving magnet 18p, the force for pulling the protruding portion 21pa by both of them is also substantially equal and balanced.

  Further, since the yoke 21p has substantially the same projected shape in the optical axis direction as the drive magnet 18p as described above, the magnetic flux entering and exiting from the two magnetic poles of the drive magnet 18p is closed through the yoke 21p. 4 (a) is the most magnetically stable state.

  FIG. 4B shows a state where the coil 20p and the yoke 21p (that is, the shift frame 15) are moved downward by energizing the coil 20p. In accordance with the force generated by the coil 20p, the pitch is displaced in the pitch direction (or yaw direction) from the stable state of FIG.

  Since the state of FIG. 4B is displaced from the stable state in terms of the magnetic circuit, when the energization to the coil 20p is stopped, it is pulled back to the state of FIG. 4A, but the protruding portion 21pa of the yoke 21p is downward. Is closer to the north pole of the drive magnet 18p and farther from the south pole.

  Since the magnitude of the magnetic force is inversely proportional to the square of the distance, the force from the magnetic pole acting on the protrusion 21pa acts in a direction that promotes displacement.

  FIG. 4C is a diagram for explaining this, and the horizontal axis indicates the voltage value applied to the coil 20p, and the vertical axis indicates the amount of displacement of the shift frame 15. FIG. The intersection of both axes indicates that the voltage applied to the coil 20p is “0” and the shift frame 15 is in the neutral position.

  If the yoke 21p does not have the protruding portion 21pa, the driving curve is as shown by a broken line A in the figure. If the protruding portion 21pa is present, the force of closing the magnetic circuit is canceled by the effect of the protruding portion 21pa, and the driving curve Becomes like a solid line B. That is, the shift frame 15 can be displaced greatly with a small applied voltage.

  The central position of the magnetic force can be controlled by changing the size of the yoke 21p and the size of the protruding portion 21pa. For example, in order to support the weight of the shift frame 15 with the magnetic force, the yoke 21p is It may be shifted intentionally or the protruding portion 21pa may be shifted downward.

  Next, in FIGS. 5A to 5D, the relationship between the shift base 13 and the shift frame 15 with respect to the ball 16b will be described. The other balls 16a and 16c have the same relationship.

  In the state shown in FIG. 5A, the shift frame 15 is in the neutral position, and the ball 16b is also a restriction frame (restriction unit) that restricts the movement of the ball 16b provided around the contact surface 13b of the shift base 13. Located in the center. The contact surface 13b is a surface corresponding to the bottom surface of a recess formed in the shift base 13 and having a rectangular (square) opening when viewed in the optical axis direction. The end surface of the limiting frame is the inner wall surface of the recess. Consists of.

  FIG. 5B shows a state in which the shift frame 15 is driven in the downward arrow direction by the driving means in the pitch direction from the state shown in FIG. In the state shown in FIG. 5B, the shift frame 15 is driven to a movable machine end (not shown) provided on the shift base 13 and moved from the neutral position by a.

  Since the ball 16b is sandwiched between the shift base 13 and the shift frame 15, the ball 16b rolls from the position of FIG. 5A to the position of FIG. 5B. Here, since the rolling friction is sufficiently smaller than the sliding friction, the ball 16b does not slide with respect to the contact surfaces 13b and 15b of the shift base 13 and the shift frame 15, and the shift frame 15 shifts while rolling the ball 16b. Move relative to the base 13.

  At this time, since the shift frame 15 and the shift base 13 are moving in the opposite directions relative to the center of the ball 16b, the movement amount b of the ball 16a relative to the shift base 13 is equal to the movement amount a of the shift frame 15. It becomes half (a ÷ 2).

  FIG. 5C shows the restriction frame of the ball 16b and the shift base 13 in the state shown in FIG. The ball 16b is located at the center in a rectangular frame surrounded by a pair of limiting end surfaces extending in the pitch direction and a pair of limiting end surfaces extending in the yaw direction.

  The size of the inside of the restriction frame is represented by (r + b + c) from the center, where r is the radius of the ball 16b. c is a mechanical margin. That is, the size of the inside of the restriction frame is the diameter of the ball 16b, the maximum movement amount (b × 2) of the ball 16b from the center accompanying the shift movement of the shift frame 15 to both sides in the pitch direction and both sides in the yaw direction, and the machine It is a dimension to which an additional margin (c × 2) is added.

  Here, when the ball 16b is at a position shifted downward by a margin amount c or more from the state where the ball 16b is located at the center in the restriction frame shown in FIG. 5C, the shift frame 15 is moved as shown in FIG. When driven downward by the amount a, the ball 16b hits the limit end face before the shift frame 15 moves by the amount a and hits the machine end, and the ball 16b presses against the limit end face during the subsequent drive of the shift frame 15. While sliding, it slides with respect to the shift frame 15.

  Then, when the shift frame 15 is returned to the center position after the a amount driving of the shift frame 15 has been completed, the ball 16b rolls back to the position of the distance c from the center of the limit frame.

  Thus, when the shift frame 15 is driven to the machine ends on both sides in the pitch direction and the yaw direction and returned to the center position, as shown in FIG. The center of the ball 16b is positioned within a rectangular range (initial position range) constituted by four sides at a distance c from the center of the restriction frame. This series of operations is called a ball reset operation.

  Usually, the optical performance of the lens is designed so that the best performance is obtained when the optical axes of the respective lenses are coincident with each other. Therefore, as the shift lens L3 is decentered with respect to other lenses, the performance is disadvantageous. It becomes a state. However, in the lens barrel of the present embodiment, optical performance having no practical problem can be achieved within the actually required shift range of the shift lens L3.

  By the way, when the shift frame 15 is driven by the same amount in the pitch direction and the yaw direction at the same time, the shift frame 15 moves in the middle direction between the pitch direction and the yaw direction to a position that is √2 times the movement amount in the pitch direction or the yaw direction. In an actual use state, the shift frame 15 is hardly driven completely independently in the pitch direction or the yaw direction, and is circular or circular around the optical axis in consideration of the position in the other direction. Shift within a polygon range close to.

  At this time, the three balls 16a to 16c roll in a half range similar to the shape of the actual movement range.

  On the other hand, the restriction frame that accommodates the balls 16a to 16c has a rectangular shape having two pairs of sides that are substantially parallel to the pitch direction and the yaw direction, respectively. If the ball has a circular or polygonal shape, the ball may not be correctly moved to a position where the ball does not come into contact with the limit end surface due to the resetting operation of the ball.

  Therefore, as described above, the size of the restriction frame is determined by determining the diameter of the ball 16b and the maximum amount of movement of the ball 16b from the center accompanying the shift movement of the shift frame 15 to both sides in the pitch direction and both sides in the yaw direction (b × 2). And a mechanical margin (c × 2). Thereby, for example, when the ball is shifted to one of the two limit end faces adjacent to each other at one corner (constitutes the corner), the pitch and yaw gaps between the ball and the other two limit end faces are The shift frame 15 is set to be larger than an amount b (2b + 2c) which is half of the mechanical maximum movable amount in each direction (or the maximum movable amount in actual use).

  In other words, when the movable range of the ball is not a rectangle but a polygon such as a circle or an octagon, if the ball is displaced and is in an arbitrary position, when it hits the end when it is reset, it rolls back in the opposite direction. If there is not enough clearance, it will hit the end and eventually the initial position may not be able to be found near the center, so this embodiment avoids this.

  Therefore, by setting the limit frame to the above-described size, the areas of the surfaces 13a to 13c and 15a to 15c that contact the balls of the shift base 13 and the shift frame 15 can be minimized, and the balls 16a When the reset operation of ˜16c is performed, the ball does not hit the limit end face during actual use, and the shift frame 15 is supported and guided only by rolling the ball. For this reason, the driving resistance of the shift frame 15 during the shake correction operation can be set to only a small rolling resistance, so that a highly accurate shake correction operation can be performed and driving means by reducing the driving force required for the shift drive. As a result, the shift unit 3 can be reduced in size.

  Further, as described above, by applying lubricating oil between the balls 16a to 16c and the contact surfaces 13a to 13c and 15a to 15c, the sliding frictional force between the balls and the contact surfaces is further reduced. Thus, it is possible to further increase the accuracy of the shake correction control and reduce the size of the shift unit 3.

  Next, position detection means will be described. This will be described with reference to FIGS. In these figures, reference numeral 22p denotes a detection magnet magnetized in two poles in the radial direction with respect to the optical axis, and the magnetic flux on the front side in the optical axis direction is closed by a yoke 21p. The detection magnet 22p is fixed to the shift frame 15 on the rear side of the yoke 21p (on the opposite side of the coil 20p across the yoke 21p).

  Reference numeral 24p denotes a hall element that converts the magnetic flux density into an electric signal, and is positioned and fixed to the sensor base 17. These detection magnets 22p, yoke 21p, and hall element 24p constitute position detection means. By sharing the yoke 21p between the drive means and the position detection means, the number of parts is reduced, the shift unit 3 is downsized and the shift frame 15 is further reduced compared to the case where a dedicated yoke for the position detection means is provided. It is possible to improve the shake correction controllability by reducing the weight.

  Here, the state of the magnetic flux on the rear side in the optical axis direction of the detection magnet 22p will be described with reference to FIG. In FIG. 6, the horizontal axis indicates the position in the radial direction with respect to the optical axis, and the vertical axis indicates the magnetic flux density. The center of the horizontal axis is a boundary portion of the two-pole magnetization of the detection magnet 22p, and the magnetic flux density is zero here. This position corresponds to a neutral position where the optical axis of the shift lens L3 is substantially coincident with other lenses.

  In FIG. 6, the magnetic flux density changes linearly within a range of displacement indicated by a two-dot chain line to such an extent that there is no practical problem. By detecting this change in magnetic flux density as an electric signal from the Hall element 24p by appropriate signal processing, the position of the shift lens L3 can be detected.

  FIG. 7 shows an example of a signal processing circuit of the Hall element 24p. In this figure, 24 is a Hall element and 40 is an operational amplifier. This operational amplifier 40 is combined with resistors 40 a, 40 b and 40 c and supplies a constant current to the Hall element 24. The output with respect to the magnetic flux density of the Hall element 24 is differentially amplified by the operational amplifier 41 and the resistors 41a, 41b, 41c, and 41d.

  The resistor 41e is a variable resistor, and the level of the electric output signal with respect to the magnetic flux density can be shifted by changing the resistance value. In this embodiment, the output is adjusted to be equal to the reference potential Vc when the shift lens L3 is in the neutral position.

  The operational amplifier 42 is combined with the resistors 42a and 42b to invert and amplify the output of the operational amplifier 41 with respect to the reference potential Vc. Then, by changing the resistance value of the variable resistor 42b, the rate of change of the output voltage with respect to the change of the magnetic flux density can be adjusted to a predetermined value.

  In FIG. 3, reference numeral 25 denotes a flexible substrate having flexibility for electrically connecting the coil 20p and the hall element 24p to an external circuit. The flexible substrate 25 is folded back at the portion 25a, and a hall element 24p is mounted on the front side in the optical axis direction of the portion 26p. Further, the folded portion 25a further has three bent portions, and the tip portion 27p allows a hole 28p formed in a part thereof to freely rotate around a pin 29p formed in the shift frame 15. It is fitted. Both terminals of the coil 20p are soldered to land portions 30p and 31p provided at the tip portion 27p.

  Reference numeral 32 denotes a pressing plate for fixing the flexible substrate 25 to the sensor base 17 and is fixed to the sensor base 17 by a single screw.

  Next, the connecting portion that absorbs the movement of the sensor base 17 and the shift frame 15 that are the fixing portions of the flexible substrate 25 will be described in more detail with reference to FIGS.

  FIG. 8A shows a shape before the flexible substrate 25 is bent. A hole 33p and a long hole 34p are formed in a portion fixed to the sensor base 17 so as to be aligned in the longitudinal direction. Pins are formed in portions corresponding to the hole 33p and the long hole 34p in the sensor base 17, respectively, and the position of the flexible substrate 25 is extended by the hole 33p, and the extending direction from the fixed portion is extended by the long hole 34p. It is decided.

  The bent portion between the hole 33p and the long hole 34p is pressed by the sensor base 17 by the pressing plate 32. The band-shaped portions of 35p and 37p are bent at approximately 90 degrees by the bent portion 36p. The movement of the shift frame 15 in the pitch direction and the yaw direction is absorbed by the bending in the longitudinal direction of the strips 35p and 37p.

  As described above, the hole portion 28p of the distal end portion 27p is fitted to the pin 29p of the shift frame 15, but the pin 29p is a stepped pin, and the distal end portion 27p is configured not to come off.

  In addition, the tip portion 27p is fitted within a certain range by fitting the protruding portion 38p between the receiving surface of the shift frame 15 and the pressing portion 15g formed with a certain interval with respect to the receiving surface. The pin 29p has a degree of freedom of rotation around the pin 29p so that the pin 29p does not come off.

  Here, when the bent portion 36p is bent at an angle of exactly 90 degrees with respect to the longitudinal direction, the hole portion 28p of the distal end portion 27p comes to the position of the pin 29p. Although unnatural deformation does not occur in 35p and 37p, when the bent portion 36p is bent out of 90 degrees with respect to the longitudinal direction, the positions of the hole portion 28p of the tip portion 27p and the pin 29p are light. The bending is shifted by the amount of bending in the axial direction.

  At this time, since the tip end portion 27p can rotate by the amount of bending deviation, the bending deviation of the bending portion 36p can be absorbed by the twisting of the belt-like portions 35p and 37p.

  If the distal end portion 27p cannot be rotated, if the bending portion 36p is misaligned, bending in the longitudinal width direction that does not easily bend the belt-like portions 35p and 37p (bending in the directions of arrows A and B in the figure). The shift frame 15 is strongly pressed in the optical axis direction. As a result, the movement of the shift frame 15 becomes worse due to an increase in friction at sliding portions between the balls 16a to 16c and the shift base 13 and the shift frame 15.

  Further, even if the pressing of the holding plate 32 at the coupling portion to the sensor base 17 is shifted and the extending direction of the flexible substrate 25 is slightly shifted, the position of the hole 28p in the optical axis direction with respect to the pin 29p is shifted. The elastic force in the optical axis direction by the flexible substrate 25 is relaxed by the rotation of 27p.

  Next, with reference to FIGS. 9A and 9B, the configuration and arrangement of the position detection means, the function of suppressing the rotation of the shift frame 15 by two magnetic circuits in the pitch and yaw directions, and the movement at that time will be described.

  FIG. 9A shows the shift frame 15 as viewed from the rear side in the optical axis direction. The two magnetic circuits in the pitch direction and the yaw direction urge the shift frame 15 in the optical axis direction. Further, as described above, the yokes 21p and 21y have substantially the same projected shape as the drive magnets 18p and 18y in the optical axis direction. Therefore, the rotation of the shift frame 15 around the optical axis with respect to the shift base 13 (sensor base 17) is suppressed by the attracting action of the two drive magnets 18p and 18y in the pitch and yaw directions fixed to the shift base 13. Is done.

  The detection magnets 22p and 22y have their respective two-pole magnetization boundaries arranged perpendicular to their own detection direction axes (pitch direction axis and yaw direction axis), and the detection direction axis of the other detection magnet. When the movement is smaller than the size of the detection magnet, the magnetic flux distribution with respect to the Hall element does not change practically. For this reason, the position of the shift frame 15 can be detected independently of the two axes.

  Further, the two position detection means in the pitch and yaw directions have the intersection of the detection direction axes coincident with the optical axis of the other lens, so that even if the shift frame 15 rotates around the optical axis, Is within a relatively small angle, it does not cause a change in output value which causes a practical problem.

  The movement of the shift frame 15 when a driving force is applied to the shift frame 15 by the driving means is based on the positional relationship between the position where the force of the driving means is generated and the center of gravity of the shift frame 15, and the connection position of the connected flexible substrate 25. It depends on the shape. Since the two magnetic circuits only suppress the rotation of the shift frame 15, the shift frame 15 may rotate around the optical axis as the shift frame 15 is driven to shift.

  The change in the output value from the position detection means at that time will be described with reference to FIG. When the position detection point in the pitch direction is A, the position detection point in the yaw direction is B, the other lens optical axis is C, and the shift frame 15 rotates around the point D, the movement of each point is observed.

  When the rotation angle is not so large, the points A, B, and C move in a direction perpendicular to the line connecting the points D.

  Here, the motion vectors of the points A to C are Va, Vb, and Vc, respectively, and these are respectively decomposed in the extending direction of two axes (the detection direction axis x in the yaw direction and the detection direction axis y in the pitch direction). The components are Vax, Vay, Vbx, Vby, Vcx, and Vcy.

  As described above, since the position detection means has little sensitivity in the direction perpendicular to the detection direction axis, the vectors of Vax and Vby are not detected by the position detection means.

  By the way, since the intersection of the two detection direction axes x and y coincides with the optical axis C, the relationship of Vcx = Vbx and Vcy = Vay is established with respect to the motion vectors Vcx and Vcy of the optical axis C.

  This indicates that the position detection means can correctly detect the change in the optical axis position of the shift lens L3 accompanying the rotation around a point away from the optical axis C, that is, the shift amount without being influenced by the rotation. Thus, the shift frame 15 can be moved to the correct position by positioning control (which will be described later) including the driving means and the position detecting means.

  FIG. 10 shows an electric circuit configuration in a photographing apparatus equipped with a lens barrel having a shake correction function. The lens barrel shown in FIG. 2 includes an optical low-pass filter 50 for removing a high frequency component of the spatial frequency of the subject, and a CCD or the like for converting an optical image arranged on the focal plane into an electric signal. An element 51 is provided.

  The camera body is provided with a camera signal processing circuit 52 that processes the electrical signal a read from the image sensor 51 into a video signal, and a microcomputer 53 as a control circuit that controls lens driving.

  When the camera power is turned on, the microcomputer 53 causes the focus motor drive circuit 56 and the zoom motor drive circuit 57 to drive the focus motor 9 and the zoom motor 10 while monitoring the outputs of the focus reset circuit 54 and the zoom reset circuit 55. The in-focus moving frame 4 and the variable magnification moving frame 2 are moved in the optical axis direction.

  The outputs of the focus reset circuit 54 and the zoom reset circuit 55 are respectively the positions where the in-focus moving frame 4 and the variable magnification moving frame 2 are set in advance (the light shielding portions provided in the respective moving frames are the light emitting portions of the reset switches 11 and 12). Is reversed at the boundary position where light is shielded. This series of operations is referred to as a reset operation of the focusing movement frame 4 and the magnification movement frame 2.

  The microcomputer 53 counts the number of subsequent drive steps of the focus motor 9 and the zoom motor 10 with the position as a reference, so that the focusing movement frame (fourth group lens L4) and the variable magnification movement frame 2 (second group). The absolute position of the lens L2) can be known. By counting the number of drive steps of the zoom motor 10, accurate focal length information can be obtained.

  Reference numeral 58 denotes an aperture driving circuit for driving the aperture unit 8, and the aperture diameter of the aperture is controlled based on the brightness information b of the video signal taken into the microcomputer 53.

  Reference numerals 59 and 60 denote pitch and yaw angle detection circuits for detecting shake angles in the pitch direction and yaw direction of the photographing apparatus, respectively. The shake angle is detected by integrating the output of an angular velocity sensor such as a vibrating gyroscope fixed to the photographing apparatus, for example.

  The outputs of the both angle detection circuits 59 and 60, that is, the information on the shake angle of the photographing apparatus is taken into the microcomputer 53.

  61 and 62 perform energization control to the coils 20p and 20y constituting the above-described driving means in the pitch direction and yaw direction according to the outputs from the angle detection circuits 59 and 60, respectively, and the shift frame 15 (shift lens L3 ) In the plane orthogonal to the optical axis and the yaw coil drive circuit.

  Reference numerals 63 and 64 respectively denote pitch and yaw position detection circuits for detecting the shift amount with respect to the optical axis of the shift frame 15 including the position detection means described above. The outputs from these position detection circuits 63 and 64 are the microcomputer 53. Is taken in.

  When the shift lens L3 is shifted, the passing light beam in the photographing lens is bent. For this reason, the shift lens L3 is shifted and moved so as to bend the passing light beam by the bending amount to be canceled in the direction to cancel the displacement of the subject image on the image pickup device 51 that is originally caused by the shake of the imaging device. It is possible to perform so-called shake correction in which a subject image that is formed does not move on the image sensor 51 even if the apparatus is shaken.

  The microcomputer 53 corresponds to the difference between the shake signal of the photographing apparatus obtained by the pitch angle detection circuit 59 and the yaw angle detection circuit 60 and the shift amount signal obtained from the pitch position detection circuit 63 and the yaw position detection circuit 64. Based on the signal obtained by performing amplification and appropriate phase compensation on the signal, the pitch coil driving circuit 61 and the yaw coil driving circuit 62 are driven to shift the shift frame 15.

  By this control, positioning of the shift lens L3 is controlled so that the difference signal becomes smaller, and the shift lens L3 is maintained at the target position.

  Furthermore, in this embodiment, since the shift lens L3 is on the imaging surface side with respect to the second group lens L2 for zooming, the amount of image movement relative to the shift amount of the shift lens L3 is the position of the second group lens L2. That is, it changes depending on the focal length.

  For this reason, the shift amount of the shift lens L3 is not determined as it is based on the shake signal of the photographing apparatus obtained by the pitch angle detection circuit 59 and the yaw angle detection circuit 60, and the shake signal is used as the position information of the second group lens L2 ( (Focal distance information). Thereby, appropriate shake correction control can be performed regardless of the focal length.

  The operation at the time of shake correction has been described so far, but the above-described reset operation of the balls 16a to 16b is performed simultaneously with the zoom and focus reset operation at the time of power-on or in time division (that is, shake correction). Even if the balls 16a to 16b are deviated from the correct position due to an impact when the photographing apparatus is not used, etc., immediately after the start of the operation, immediately after the ball reset operation, A shake correction operation can be performed. For this reason, it is possible to always exhibit excellent shake correction performance.

  Further, the microcomputer 53 discriminates states other than when the photographing apparatus is in use (when the photographed image is observed on the monitor or when the image is recorded on the recording apparatus) (for example, the shake angle of the photographing apparatus). By observing, it is determined whether or not the user is carrying the photographing device), and in this state, by appropriately performing the ball reset operation, excellent shake correction can be guaranteed at all times during use.

  In general, the correction angle range of shake correction is about 0.5 to 1 degree. In actual shooting, the above correction is performed by operating each function of the shooting apparatus or searching for a subject on the viewfinder. This gives a motion of an angle or more to the photographing apparatus. For this reason, the same operation as the ball resetting operation may be performed by the movement. When the ball transitions from the rolling friction state to the sliding friction state, the shake correction performance deteriorates for a moment due to the discontinuous increase of the frictional force, but if the device is moved beyond the correction angle range, the ball will roll after that. Since guidance is performed only by this, good shake correction can be performed.

  In this embodiment, the moving coil type shake correction apparatus in which the driving magnet is held on the shift base and the coil is held on the shift frame has been described. However, the driving magnet is held on the shift frame and the coil is held on the shift base. You may do it.

  In the present embodiment, the shift unit used in the photographing apparatus has been described. However, the shake correction apparatus of the present invention can also be used in observation apparatuses such as binoculars and telescopes.

1 is an exploded perspective view of a lens barrel that is an embodiment of the present invention. Sectional drawing of said lens-barrel. The disassembled perspective view of the shift unit used for the said lens-barrel. The figure explaining the drive means of the said shift unit. The figure explaining the movement restriction | limiting frame of the ball in the said shift unit. The figure explaining the principle of the position detection means provided in the said shift unit. The figure of the signal processing circuit of the Hall element which constitutes the above-mentioned position detection means. Explanatory drawing of the flexible substrate used for the said shift unit. The figure explaining the characteristic with respect to rotation of the shift frame of the said position detection means. The block diagram which shows the electric circuit structure of the imaging device provided with the said lens-barrel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed lens barrel 2 Variable magnification moving frame 3 Shift unit 4 Focusing moving frame 5 Rear lens barrel 6, 7 Guide bar 8 Aperture unit 9 Focus motor 10 Zoom motor 11, 12 Reset switch 13 Shift base 14 Positioning member 15 Shift frame 16a -16c Ball 17 Sensor base 18p, 18y Driving magnet 19p, 19y Back yoke 20p, 20y Coil 21p, 21y Yoke 22p, 22y Detection magnet 24p, 24y Hall element 25 Flexible substrate 32 Holding plate

Claims (5)

An image stabilization lens,
A shift frame that holds the shake correction lens and is movable in the direction perpendicular to the optical axis;
A shift base for restricting movement of the shift frame in the optical axis direction;
A ball sandwiched between the shift frame and the shift base and capable of rolling;
A limiting portion for limiting movement of the ball within a predetermined range by contact with the ball;
A two-pole magnetized magnet held on one of the shift frame and the shift base; and a yoke and a coil held on the other of the shift frame and the shift base, and the shift by energizing the coil A lens barrel having a driving means for driving the frame in the direction orthogonal to the optical axis,
The shift frame is biased toward the shift base by a magnetic attractive force acting between the magnet and the yoke,
The yoke includes a protruding portion protruding toward the magnet,
The lens barrel characterized in that, in a state where the center of the shake correction lens coincides with the optical axis, the projecting portion is located at a boundary of two-pole magnetization of the magnet.   The lens barrel according to claim 1, wherein the coil is provided between the magnet and the yoke and on an outer periphery of the protrusion.   3. The lens barrel according to claim 1, wherein a biasing force that biases the shift frame toward the shift base is not less than five times the weight of the shift frame including the shake correction lens.   An imaging apparatus comprising the lens barrel according to any one of claims 1 to 3. An observation apparatus comprising the lens barrel according to any one of claims 1 to 3.