JP5679736B2 - Lens barrel and imaging device - Google Patents

Description

The present invention relates to a lens barrel having a bending optical element such as a prism and a mirror, and an imaging apparatus having the lens barrel .

  A subject-side lens frame provided so as to be movable in the first optical axis direction between the storage position and the photographing position while holding the subject-side lens, and a light beam incident through the subject-side lens There is known a lens barrel that includes a prism that is bent in a second optical axis direction intersecting the optical axis and guided to an image sensor. The prism is arranged behind the subject side lens frame in the first optical axis direction to bend the incident light beam toward the image sensor when the subject side lens frame is at the photographing position. Further, when the subject-side lens frame is in the storage position, the prism moves from the rear of the subject-side lens frame to the retracted position along the second optical axis direction in order to secure a storage space for the subject-side lens frame. (See Patent Document 1).

JP 2007-226106 A

  The lens barrel described above is supported by two guide shafts so that the prism holding member that holds the prism can be moved between the photographing position and the retracted position along the second optical axis direction. In the photographing state, when the prism holding member supported by the guide shaft is driven by a rack provided on the prism holding member and a prism driving gear that meshes with the rack and transmits a driving force, the prism holding member becomes a photographing side stopper. To stop at the shooting position. At this time, a component force generated in the pressure angle direction of the prism drive gear is applied in a direction orthogonal to the guide shaft, and thus the guide shaft may be deformed. Further, the deformation of the guide shaft causes a problem that the third lens group and the fourth lens group supported by the guide shaft are decentered.

The present invention aims to provide a lens barrel and an image pickup device capable of suppressing the occurrence of collapse eccentricity of the lens group to be driven is supported by the guide shaft.

The lens barrel according to the present invention is supported by an optical element and two guide shafts arranged in parallel, is supported by a holding member that holds the optical element, and the two guide shafts, and the two and movable lens along an axial direction of the guide shaft, and said one guide shaft engaging portion to be engaged with one guide shaft of Oite the two guide shafts to the holding member The holding gear is driven in the length direction of the two guide shafts by meshing with the rack gear provided in parallel with the rack gear and transmitting the driving force transmitted from the driving means to the rack gear by a rotating operation. An optical element driving gear, a guide shaft restricting member disposed at a position facing the optical element driving gear so as to sandwich the one guide shaft, and the holding member when the optical element is at a photographing position. 1 moth And a biasing means for biasing against the stopper member provided in the de-axis, the guide shaft regulating member, the one when the holding member by the biasing means is biased to the stopper member The guide shaft is arranged at a position to receive a component force in the pressure angle direction of the optical element driving gear .

  According to the present invention, the guide shaft restricting member is disposed at a position facing the optical element driving gear with the guide shaft supporting the lens group interposed therebetween, so that the deformation of the guide shaft can be suppressed. Occurrence of the eccentric collapse of the group can be suppressed.

It is sectional drawing which shows schematic structure of the lens-barrel which concerns on embodiment of this invention. It is another sectional view showing a schematic structure of a lens barrel. It is another sectional view showing the schematic structure of a lens barrel. It is a perspective view which decomposes | disassembles and shows a part of mechanism which drives a cam cylinder and a prism. It is a perspective sectional view showing a part of a part of mechanism which drives a cam cylinder and a prism. It is a top view which shows a holding member and a part of prism drive part which hold | maintain a prism. It is an inner peripheral side expanded view of a fixed cylinder. It is a figure which shows typically the phase relationship of a prism carrier and a prism delay gear, and the charge amount of a torsion spring. It is a perspective view which shows the state which the holding member holding a prism contact | abutted to the imaging | photography side stopper. It is a figure which shows the component force which arises in the pressure angle direction of a prism drive gear added to the guide shaft which supports a holding member. It is sectional drawing which shows the relationship between a guide shaft and a guide shaft control member.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, a lens barrel having a zoom function mounted on an imaging apparatus such as a so-called digital camera is taken as a specific example.

  FIG. 1 is a cross-sectional view showing a schematic structure of a lens barrel according to an embodiment of the present invention, and shows a state where the lens barrel is at a photographing position having the widest angle of view (hereinafter referred to as “WIDE position”). . The lens barrel includes a first lens group 10, a second lens group 20, a prism 5, a fixed cylinder 62, a cam cylinder 61, and a rectilinear guide cylinder 63.

  The first lens group 10 has a structure in which the first group lens 1 is held in the first group lens barrel 11, and the second lens group 20 has a structure in which the second group lens 2 is held in the second group lens barrel 21. doing. The light beam incident through the first group lens 1 and the second group lens 2 intersects the optical axis A (first optical axis) of the first group lens 1 and the second group lens 2 at an angle of approximately 90 °. It is bent by the prism 5 in the direction of (second optical axis) and guided to the image sensor 8.

  The prism 5 is an example of a bending optical element. The prism 5 is held by the holding member 6, and is movable along the optical axis B while being held by the holding member 6. A third lens group 30, a fourth lens group 40, and an optical filter 7 are disposed along the optical axis B between the prism 5 and the image sensor 8.

  The third lens group 30 includes a shutter mechanism (not shown) fixed to the front base plate 32 and a third group lens 3 held by the rear base plate 34. The front base plate 32 and the rear base plate 34 are mutually screwed or the like. Are combined. As the third lens group 30 moves along the optical axis B, a zooming operation (zooming) is performed. The fourth lens group 40 has a structure in which the fourth group lens 4 is held by the fourth group lens holder 41. When the fourth lens group 40 moves along the optical axis B, the zooming operation and the focusing operation are performed. Operation (focusing) is performed. As the optical filter 7, an optical filter having a low-pass filter function for cutting light having a high spatial frequency, a function for cutting infrared light, or the like is used.

  FIG. 2 is another cross-sectional view showing a schematic structure of the lens barrel shown in FIG. 1, and shows a state in which the lens barrel is at a photographing position having the narrowest angle of view (hereinafter referred to as “TELE position”). In a state where the lens barrel is in the TELE position, the first lens group 10 extends toward the subject along the optical axis A, and the second lens group 20 moves back along the optical axis A and approaches the prism 5. Stop at. The third lens group 30 moves toward the prism 5 along the optical axis B and stops at a position close to the prism 5. The fourth lens group 40 moves toward the image sensor 8 along the optical axis B and stops at a position close to the image sensor 8.

  FIG. 3 is another cross-sectional view showing a schematic structure of the lens barrel shown in FIG. 1, and shows a state in which the lens barrel is housed in the main body of the digital camera (hereinafter referred to as “SINK position”). When the lens barrel is in the SINK position, the prism 5, the third lens group 30, and the fourth lens group 40 move along the optical axis B toward the image sensor 8 so as not to interfere with each other. As a result, a storage space is formed behind the second lens group 20 and the first lens group 10, and the second lens group 20 and the first lens group 10 are retracted along the optical axis A to the formed storage space. Stored.

  Cam grooves 62a (see FIG. 6), which are cam-engaged with cam pins (not shown) provided on the outer peripheral portion of the cam barrel 61, are provided at a plurality of locations at substantially equal intervals in the circumferential direction on the inner peripheral portion of the fixed barrel 62. Is formed. A gear portion 61a (see FIG. 4) that meshes with the drive gear 60 (see FIG. 4) is formed on the outer peripheral portion of the cam cylinder 61, and the driving force is transmitted from the drive gear 60 to the gear portion 61a. Then, the cam cylinder 61 is rotationally driven. At this time, the cam cylinder 61 advances and retreats along the optical axis A by the cam action of the cam groove 62 a of the fixed cylinder 62 and the cam pin provided on the outer peripheral portion of the cam cylinder 61. A first group cam groove and a second group cam groove (not shown) are formed in the inner peripheral portion of the cam cylinder 61.

  The rectilinear guide tube 63 is disposed on the inner peripheral side of the cam tube 61, can rotate integrally with the cam tube 61, and can move in the direction of the optical axis A. A first group barrel 11 constituting the first lens group 10 is disposed between the cam barrel 61 and the rectilinear guide barrel 63, and cam pins (not shown) provided on the outer periphery of the first group barrel 11 are arranged. The cam cylinder 61 is cam-engaged with a first group cam groove provided in the inner peripheral portion of the cam cylinder 61. Further, a rectilinear groove (not shown) extending along the optical axis A is formed on the outer peripheral portion of the rectilinear guide tube 63, and a convex portion provided on the inner peripheral portion of the first group barrel 11 in the rectilinear groove. By engaging (not shown), the movement of the first group barrel 11 in the rotational direction is restricted.

  The second lens group 20 is disposed on the inner peripheral side of the rectilinear guide tube 63, and a cam pin (not shown) provided on the outer peripheral portion of the second group lens barrel 21 constituting the second lens group 20 is a cam tube 61. The cam is engaged with a second group cam groove provided on the inner peripheral portion of the cam. Further, a through groove (not shown) is formed in the linear guide tube 63 in the direction of the optical axis A, and the engagement is arranged in the through groove at the base of the cam pin provided on the outer peripheral portion of the second group barrel 21. The movement of the second group barrel 21 in the rotational direction is restricted by the engagement of the portions.

  When the cam barrel 61 rotates, the convex portion provided on the inner periphery of the first group barrel 11 slides in the rectilinear groove formed in the rectilinear guide barrel 63 in the direction of the optical axis A. It advances and retreats along the optical axis A with respect to the cam cylinder 61. This operation is realized by the cam action of the first group cam groove provided on the inner peripheral portion of the cam barrel 61 and the cam pin provided on the outer peripheral portion of the first group barrel 11. Therefore, when the cam cylinder 61 advances and retreats along the optical axis A with respect to the fixed cylinder 62, the first group lens barrel 11 advances and retreats along the optical axis A with respect to the cam cylinder 61, and the first group lens 1 moves to the SINK position. It moves between the (storage position) and the shooting position (WIDE position to TELE position). The second group lens 2 is also moved between the storage position and the photographing position by the same operation. In addition, the structure which concerns on the above description is a structure of the lens moving mechanism using a general cam cylinder.

  Next, a transmission mechanism that transmits the driving force of the motor to the cam cylinder 61 and a transmission mechanism that transmits the driving force of the motor to the prism 5 will be described with reference to FIGS.

  FIG. 4 is an exploded perspective view showing a part of the mechanism for driving the cam cylinder 61 and the prism 5. 5 is a perspective sectional view showing a part of a part of the mechanism for driving the cam cylinder 61 and the prism 5 of FIG.

  4 and 5, the SW motor 51 is a drive source for moving the first lens group 10 and the second lens group 20 between the SINK position and the WIDE position. The TW motor 53 is a drive source for moving the first lens group 10 and the second lens group 20 between the TELE position and the WIDE position. A worm gear 52 is press-fitted into the motor shaft of the SW motor 51, and a worm gear 54 is press-fitted into the motor shaft of the TW motor 53.

  Between the worm gear 52 and the worm gear 54, a zoom ring gear 55, a zoom carrier gear 56, and a sun gear train 57 are arranged coaxially in parallel with the optical axis A from the subject side (upper side in FIGS. 4 and 5). ing.

  The sun gear train 57 includes sun gears 57a to 57c formed of three stages of flat gears. The sun gear 57a meshes with the worm gear 52 via the oblique gear when the sun gear 57a meshes with the oblique gear.

  The zoom carrier gear 56 includes a gear portion 56a and three shaft portions 56b projecting at substantially equal intervals in the circumferential direction on a surface facing the subject side in the gear portion 56a. Each of the three shaft portions 56b includes a shaft portion 56b. A zoom planetary gear 58 is pivotally supported. The worm gear 54 meshes with the gear portion 56a via an inclined gear or the like, and the zoom planetary gear 58 meshes with the sun gear 57b.

  The zoom ring gear 55 includes an internal gear 55a and an external gear 55b. The internal gear 55 a meshes with the zoom planetary gear 58, the external gear 55 b meshes with the drive gear 60 via the idler gear 59, and the drive gear 60 meshes with the gear portion 61 a of the cam barrel 61.

  As described above, the gear train disposed between the TW motor 53 and the SW motor 51 and the gear portion 61 a constitutes a transmission mechanism that transmits the driving force of the TW motor 53 and the SW motor 51 to the cam cylinder 61. .

  Next, the prism driving unit 80 will be described. In the prism driving unit 80, as shown in FIG. 4, a prism planetary gear 83, a prism carrier 81, a torsion spring 84, and a prism delay gear 82 are arranged in order from the subject side below the sun gear train 57. And are arranged coaxially.

  On the surface of the prism carrier 81 facing the subject side, three shaft portions protrude in the circumferential direction at substantially equal intervals, and a prism planetary gear 83 is supported on each of the three shaft portions. Yes. The prism planetary gear 83 meshes with an internal gear (not shown) fixed to the sun gear 57c and a gear base plate (not shown).

  The prism delay gear 82 is rotatably supported on the prism carrier 81. A prism drive gear 85 as an optical element drive gear meshes with the gear portion of the prism delay gear 82. Each of the prism carrier 81 and the prism delay gear 82 is formed so that the latching portion 81b and the latching portion 82b extend in directions opposite to each other, and the latching portion 81b is radially inward of the latching portion 82b. Is arranged (see FIG. 8).

  As shown in FIG. 8 to be described later, the torsion spring 84 includes a coil portion and two arm portions 84a and 84b extending radially outward from both axial ends of the coil portion. The two arms 84 a and 84 b are hooked on the hooks 82 b and 81 b of the prism delay gear 82 and the prism carrier 81. The torsion spring 84 is incorporated in the prism driving unit 80 in a state where the latching portion 82b and the latching portion 81b are arranged in the same phase (see FIG. 8B). At this time, the torsion spring 84 is precharged with the arm portion 84a hooked to the hook portion 81b and the arm portion 84b hooked to the hook portion 82b.

  In this state, when the prism carrier 81 is rotated by freely rotating the prism delay gear 82, the prism carrier 81, the prism delay gear 82, and the torsion spring 84 rotate integrally. On the other hand, when the prism carrier 81 is rotated in a state where the rotation of the prism delay gear 82 is restricted, only the prism carrier 81 rotates while overcharging the torsion spring 84.

  FIG. 6 is a plan view showing a part of the holding member 6 that holds the prism 5 and the prism driving unit 80. The holding member 6 includes engaging portions 6a and 6b that are movably engaged with two guide shafts 86 and 87 that are arranged in parallel to each other and extend in the optical axis B direction. A rack gear 6 c is formed in the engaging portion 6 a, and the rack gear 6 c meshes with the prism drive gear 85. With such a structure, when the rotation operation of the prism drive gear 85 is transmitted to the rack gear 6 c, the holding member 6 moves forward and backward along the optical axis B together with the prism 5.

  Thus, in the present embodiment, a transmission mechanism that transmits the driving force of the SW motor 51 and the TW motor 53 to the prism 5 is configured by the gear train arranged between the sun gear train 57 and the rack gear 6 c. In addition, a transmission mechanism that transmits the driving force of the TW motor 53 and the SW motor 51 to the cam barrel 61 is disposed in the projection range of the cam barrel 61 in the optical axis A direction.

  The operation of the cam cylinder 61 and the prism 5 will be described with reference to FIGS. 4 and 5 again. When the SW motor 51 is driven and the TW motor 53 is stopped, the driving force is transmitted from the SW motor 51 to the sun gear train 57 and the sun gear train 57 rotates. On the other hand, the zoom carrier gear 56 connected to the TW motor 53 is stopped. Therefore, the zoom planetary gear 58 only rotates without revolving.

  For example, when the number of teeth of the sun gear 57b is 9, the number of teeth of the zoom planetary gear 58 is 10, and the number of teeth of the internal gear 55a of the zoom ring gear 55 is 30, the rotation of the sun gear train 57 is 1/3. The speed is reduced by 33 times and transmitted to the zoom ring gear 55. Thereby, the rotation of the external gear 55b of the zoom ring gear 55 is transmitted to the drive gear 60 via the idler gear 59, the rotation of the drive gear 60 is transmitted to the gear portion 61a of the cam cylinder 61, and the cam cylinder 61 rotates. Driven.

  At this time, the rotation direction of the zoom ring gear 55 is opposite to the rotation direction of the sun gear train 57. At this time, the rotation of the sun gear train 57 is transmitted to the prism carrier 81 via the prism planetary gear 83. Here, when the holding member 6 is movable in the optical axis B direction, the torsion spring 84 and the prism delay gear 82 rotate together with the prism carrier 81 to advance and retract the holding member 6 in the optical axis B direction. On the other hand, when the movement of the holding member 6 in the direction of the optical axis B is restricted, the prism delay gear 82 cannot rotate, so that the rotation of the prism carrier 81 is absorbed while the torsion spring 84 is overcharged.

  When the SW motor 51 is stopped and the TW motor 53 is driven, the sun gear 57 connected to the SW motor 51 stops and the zoom carrier gear 56 connected to the TW motor 53 rotates. Therefore, the zoom planetary gear 58 rotates and revolves. For example, if the number of teeth of the sun gear 57b is 9, the number of teeth of the zoom planetary gear 58 is 10, and the number of teeth of the internal gear 55a of the zoom ring gear 55 is 30, the rotation of the zoom carrier gear 56 is 1.3 times. The speed is increased and transmitted to the zoom ring gear 55. In this way, the cam cylinder 61 is rotationally driven in the same manner as when the SW motor 51 is driven and the TW motor 53 is stopped.

  At this time, the rotation direction of the zoom ring gear 55 is the same as the rotation direction of the zoom carrier gear 56. At this time, since the sun gear 57 is stopped, the prism carrier 81 is also stopped, and the driving force is not transmitted to the holding member 6.

  When the SW motor 51 and the TW motor 53 are driven at the same time, the combined rotation speed is transmitted to the zoom ring gear 55. For example, consider a case where the sun gear 57 is rotated at 1 rpm in the CW (clockwise) direction and the zoom carrier gear 56 is rotated at 1 rpm in the CW direction. In this case, the rotational speed that should be transmitted to the zoom ring gear 55 by the sun gear train 57 is 0.3 rpm in the CCW (counterclockwise) direction and should be transmitted to the zoom ring gear 55 by the zoom carrier gear 56. The rotation speed is 1.3 rpm in the CW direction. Therefore, when these rotational speeds are combined, the zoom ring gear 55 rotates at a rotational speed of 1 rpm in the CW direction.

  Here, consider a case where the sun gear train 57 is rotated at 1.3 rpm in the CW direction and the zoom carrier gear 56 is rotated at 0.3 rpm in the CW direction. The rotational speed that should be transmitted to the zoom ring gear 55 by the sun gear 57 is 0.39 rpm in the CCW direction, and the rotational speed that should be transmitted to the zoom ring gear 55 by the zoom carrier gear 56 is 0 in the CW direction. 39 rpm. Therefore, when these rotational speeds are combined, the zoom ring gear 55 stops.

  From the above description, it can be seen that the prism 5 can be driven with the cam cylinder 61 stopped by appropriately selecting the rotational speed and direction of the SW motor 51 and the TW motor 53. It can also be seen that the gear ratio connected to the SW motor 51 is large and the gear ratio connected to the TW motor 53 is small. This point will be described later.

  Next, with reference to FIGS. 7 to 9, the operation of extending the first lens group 10 and the second lens group 20 in the direction of the optical axis A and arranging the prism 5 at the photographing position will be described.

  FIG. 7 is a development view of the inner circumference side of the fixed cylinder 62. On the inner peripheral portion of the fixed cylinder 62, cam grooves 62a in which cam pins provided on the outer peripheral portion of the cam cylinder 61 are cam-engaged are formed at a plurality of positions at substantially equal intervals in the circumferential direction. In addition, a notch 62b is formed at the rear end of the fixed cylinder 62 through which the holding member 6 holding the prism 5 passes when it advances and retreats in the direction of the optical axis B. Reference numerals 62c, 62d, and 62e in FIG. 7 are examples of positions of cam pins provided on the outer peripheral portion of the cam cylinder 61, which will be described later.

  FIG. 8 is a diagram schematically showing the phase relationship between the prism carrier 81 and the prism delay gear 82 and the charge amount of the torsion spring 84. When the lens barrel is in the SINK position, the cam pin provided on the outer peripheral portion of the cam barrel 61 is disposed in the cam groove 62a of the fixed barrel 62 at a position 62c in FIG. At this time, the prism carrier 81 and the prism delay gear 82 are in a phase relationship for overcharging the torsion spring 84 as shown in FIG.

  FIG. 9 is a perspective view showing a state in which the holding member 6 holding the prism 5 is in contact with the photographing side stopper 6e. In the state shown in FIG. 7A, the holding member 6 is urged in the retracting direction of the optical axis B (on the image sensor 8 side) by the charging force of the torsion spring 84, but as shown in FIG. Movement in the retracting direction is restricted by contacting the photographing side stopper 6e.

  In order to move the lens barrel from the SINK position to the photographing position, first, the SW motor 51 is rotated in the extending direction of the cam cylinder 61 (subject side). At this time, the cam pin provided on the outer peripheral portion of the cam cylinder 61 moves the cam groove 62a of the fixed cylinder 62 to the right in FIG. 7, and the first lens group 10 and the second lens group 20 have a lift. To move in the feeding direction along the optical axis A. During this extension operation, the prism carrier 81 also rotates in the direction in which the holding member 6 is extended to the photographing position. However, since the torsion spring 84 is in an overcharged state, the prism delay gear 82 remains stopped. Therefore, the holding member 6 does not move from the retracted position.

  When the cam cylinder 61 is extended in the direction of the optical axis A to form a space in which the holding member 6 can move to the photographing position side, as shown in FIG. 8B, the latching portion 81b of the prism carrier 81 and the prism delay are formed. The phase with the hooking portion 82b of the gear 82 matches. When the SW motor 51 is further rotated in the feeding direction of the cam cylinder 61, the cam pin provided on the outer peripheral portion of the cam cylinder 61 moves the cam groove 62a of the fixed cylinder 62 to the right in FIG. Moves toward the shooting position.

  After the cam cylinder 61 reaches the WIDE position, the TW motor 53 is driven in the retraction direction of the cam cylinder 61 while the SW motor 51 is driven in the retraction direction of the cam cylinder 61. Thereby, only the holding member 6 continues to move toward the photographing position along the optical axis B direction while the cam cylinder 61 is stopped at the WIDE position.

  When the holding member 6 reaches the photographing position, as shown in FIG. 9, the holding member 6 comes into contact with the photographing side stopper 6 e and stops, and at the same time as the holding member 6 stops, the prism delay gear 82 also stops. At this time, by continuing to drive the SW motor 51 in the feeding direction of the cam cylinder 61, the prism carrier 81 continues to rotate in the direction in which the holding member 6 is drawn out to the photographing position, and as shown in FIG. The spring 84 is overcharged. If the torsion spring 84 is overcharged to some extent, the holding member 6 is biased toward the photographing side stopper 6e by the action of the torsion spring 84, so that the position and posture of the holding member 6 can be stabilized during photographing. It is done.

  Here, since the holding member 6 is always biased by the photographing side stopper 6e at the photographing position, a component force generated in the pressure angle direction of the prism driving gear 85 is applied to the guide shaft 86 supporting the holding member 6. . FIG. 10 is a diagram showing a component force generated in the pressure angle direction of the prism drive gear 85 applied to the guide shaft 86 that supports the holding member 6. Since this component force F is applied in a direction perpendicular to the guide shaft 86, the guide shaft 86 may be deformed. When the guide shaft 86 is deformed, there arises a problem that the third lens group 30 and the fourth lens group 40 supported by the guide shaft 86 are decentered.

  In order to prevent such a problem, in the lens barrel according to the present embodiment, a guide shaft for restricting the deformation amount of the guide shaft 86 at a position substantially opposed to the prism drive gear 85 with the guide shaft 86 interposed therebetween. The restricting member 6d is arranged. Therefore, next, the relationship between the guide shaft 86 and the guide shaft restricting member 6d will be described with reference to FIG.

  FIG. 11 is a cross-sectional view showing the relationship between the guide shaft 86 and the guide shaft regulating member 6d. As for the fitting of the guide shaft 86 and the guide shaft regulating member 6d, it is desirable that the clearance between them is 0 (zero). If the clearance is 0, the guide shaft 86 can be prevented from being deformed even when the guide shaft 86 receives a force from the prism drive gear 85, so that the eccentricity accuracy of the third lens group 30 and the fourth lens group 40 is substantial. There is no decline.

  However, in practice, since it is difficult to make the clearance between the guide shaft 86 and the guide shaft restricting member 6d zero due to processing tolerances, in this embodiment, for example, a clearance of 15 μm is provided. By arranging the guide shaft regulating member 6d, the deformation amount of the guide shaft 86 depends on the clearance amount. Therefore, even if the guide shaft 86 is deformed by receiving a force from the prism driving gear 85, the eccentric accuracy of the third lens group 30 and the fourth lens group 40 is stably maintained within the provided clearance range. Will be able to.

  As described above, in the present embodiment, the guide shaft restricting member 6d is disposed at a position substantially opposite to the prism drive gear 85 with the guide shaft 86 interposed therebetween. It is possible to prevent the eccentric collapse of the four lens group 40.

  When the torsion spring 84 reaches a certain overcharge state, the SW motor 51 and the TW motor 53 are stopped. Thus, the first lens group 10, the second lens group 20, and the prism 5 are arranged at the WIDE position as the imaging position and enter the imaging state. When the cam cylinder 61 reaches the WIDE position, the cam pin provided on the outer peripheral portion of the cam cylinder 61 moves to a position 62 d shown in FIG. 7 in the cam groove 62 a of the fixed cylinder 62. Thereafter, the third lens group 30 and the fourth lens group 40 are driven to a predetermined position in the optical axis B direction by driving a motor (not shown).

  When the lens barrel is moved from the WIDE position to the SINK position, an operation opposite to the operation relating to the movement from the SINK position to the WIDE position is performed. That is, first, a motor (not shown) is driven to retract the third lens group 30 and the fourth lens group 40 toward the image sensor 8 along the optical axis B. Subsequently, the TW motor 53 is driven in the feeding direction of the cam cylinder 61, and at the same time, the SW motor 51 is driven in the feeding direction of the cam cylinder 61. Thereby, the cam cylinder 61 does not rotate, and only the prism carrier 81 rotates in the direction in which the holding member 6 is extended to the photographing position.

  When the prism carrier 81 rotates by the amount of overcharge of the torsion spring 84 in the state shown in FIG. 8C, the phases of the latching portion 81b of the prism carrier 81 and the latching portion 82b of the prism delay gear 82 are as shown in FIG. Match as shown in (b). At this time, the prism delay gear 82 rotates integrally with the prism carrier 81 and the torsion spring 84 in the direction of retracting the holding member 6 to the retracted position, and the holding member 6 moves in the retracted direction.

  When the holding member 6 moves to the retracted position and a space that can be stored behind the cam cylinder 61 is formed, the TW motor 53 stops and only the SW motor 51 continues to drive in the direction in which the cam cylinder 61 is retracted. . Thereby, the cam cylinder 61 starts to be retracted. When the holding member 6 moves to the retracted position, the retaining member 6 comes into contact with the retracting side end member (not shown) and stops, and at the same time, the prism delay gear 82 also stops.

  Since the SW motor 51 continues to be driven to retract the cam cylinder 61 to the retracted position, the prism carrier 81 continues to rotate in a direction to retract the holding member 6 to the retracted position while overcharging the torsion spring 84. . When the cam cylinder 61 is housed in the SINK position and the first lens group 10 and the second lens group 20 are housed, the SW motor 51 stops.

  When the lens barrel is zoomed between the WIDE position and the TELE position, by driving only the TW motor 53, the first lens group 10 and the second lens group 10 are moved without moving the holding member 6 in the optical axis B direction. The lens group 20 can be moved in the direction of the optical axis A. At the TELE position of the lens barrel, the cam pin provided on the outer peripheral portion of the cam barrel 61 is disposed at a position 62e of the cam groove 62a of the fixed barrel 62 shown in FIG.

  Next, an effect obtained by setting the reduction ratio of the gear train connected to the SW motor 51 to be large and setting the reduction ratio of the gear train connected to the TW motor 53 to be small will be described.

  Generally, the driving load of the cam cylinder 61 is larger in the area from the SINK position to the imaging area where the lift angle of the cam groove 62a of the fixed cylinder 62 is larger than in the imaging area from the WIDE position to the TELE position. Further, in the region from the SINK position to the imaging region, an operating load of a lens barrier (not shown) is often further applied, and therefore it is necessary to amplify the motor torque using a gear train having a large reduction ratio. On the other hand, in the shooting area from the WIDE position to the TELE position, it is necessary to keep the motor rotation speed low so that lens drive sound is not recorded during shooting of moving images or the like. However, if a gear train having a large reduction ratio is used for this purpose, the rotational speed of the cam cylinder 61 becomes extremely slow.

  Therefore, in the present embodiment, in the region from the SINK position where the load of the cam cylinder 61 is large to the imaging area, the driving force of the SW motor 51 is transmitted to the cam cylinder 61 via the gear train having a large reduction ratio. Drive. In the imaging region from the WIDE position to the TELE position, the cam cylinder 61 is driven by transmitting the driving force of the TW motor 53 to the cam cylinder 61 via a gear train having a small reduction ratio. Thereby, even if the TW motor 53 is rotated at a low speed so that the driving sound of the motor is reduced during moving image shooting, a comfortable zooming operation speed can be obtained.

  In the present embodiment, the SW motor 51 and the TW motor 53 can be different types of motors. For example, a DC motor can be used for the SW motor 51 and a stepping motor can be used for the TW motor 53. A stepping motor is suitable for low-speed driving during moving image shooting because stable control at a low speed is possible compared to a DC motor.

  Further, when selecting a stepping motor, a driving method can be selected. For example, if a stepping motor whose driving method is a micro-step driving method is used, driving with higher silence becomes possible. For example, if a stepping motor whose driving method is a two-phase excitation driving method is used, high torque driving is possible. Therefore, it is preferable to use micro-step driving for a scaling operation during moving image shooting that requires quietness, and to use two-phase driving for a scaling operation during still image shooting.

  Next, the pulse gear train 70 for detecting the positions of the first lens group 10 and the second lens group 20 in the optical axis A direction will be described. As shown in FIGS. 4 and 5, the pulse gear train 70 is connected to the idler gear 59. The pulse plate 71 at the final stage of the pulse gear train 70 is provided with a plurality of blades, and the number of times these blades have passed is counted by the photo interrupter 72 to detect the amount of rotation of the cam cylinder 61. The speed increasing ratio of the pulse gear train 70 and the number of blades of the pulse plate 71 are determined so as to obtain a necessary resolution determined by optical design.

  By the way, when the gear train is originally used for transmission of the driving force of the motor, the rotation amount of the cam cylinder is linearly determined by the reduction ratio with respect to the rotation amount of the motor because there is no loss of rotation amount due to slipping. However, in reality, the cam barrel rotation amount varies with respect to the motor rotation amount due to gear backlash and meshing errors.

  However, in a conventional lens barrel that drives one cam barrel with one motor, once the gear train is assembled, the meshing relationship of the gears remains unchanged even when the motor is driven. That is, since the same teeth mesh each time, the state of variation in the amount of rotation of the cam cylinder relative to the amount of rotation of the motor should be the same every time. Actually, when the rotation amount of the cam cylinder is calculated from the rotation amount of the motor, an error from the actual rotation amount is small.

  In the case of driving one cam cylinder 61 by combining the rotation amounts of two motors (SW motor 51 and TW motor 53) using the zoom planetary gear 58 as in the present embodiment, when one motor is rotated, the other The relationship of the meshing teeth between the motor and the zoom ring gear 55 changes. That is, each time the power of the camera including the lens barrel according to the present embodiment is turned on, different teeth mesh each time, and therefore the state of variation in the rotation amount of the cam tube 61 with respect to the rotation amount of the motor is different. Therefore, even if the rotation amount of the cam cylinder 61 is obtained by calculation from the rotation amount of the motor, there is a possibility that an error from the actual rotation amount becomes large.

  In the present embodiment, the pulse gear train 70 is branched from the idler gear 59 between the zoom ring gear 55, which is the output gear of the zoom planetary gear 58, and the cam cylinder 61 so that such a problem does not occur. As a result, the meshing relationship between the pulse gear train 70 and the cam cylinder 61 remains unchanged. Therefore, the rotation amount of the cam barrel 61 can be detected with an error equivalent to that of the conventional lens barrel.

  As described above, in the present embodiment, the prism 5 (holding member 6) is in the projection range in the optical axis A direction of the transmission mechanism that transmits the driving force of the motor (SW motor 51 and TW motor 53) to the cam cylinder 61. In contrast, a transmission mechanism for transmitting the driving force of the motor is arranged. Thereby, the occupied area when each transmission mechanism that transmits the driving force of the motor to the cam cylinder 61 and the prism 5 (holding member 6) is viewed from the optical axis A direction of the cam cylinder 61 can be reduced. Therefore, for example, it is possible to reduce the size of an imaging apparatus such as a digital camera provided with the lens barrel according to the present embodiment. In the present embodiment, the cam cylinder 61 and the prism 5 can be driven by a common motor. Therefore, as compared with the case where a dedicated motor for driving the prism 5 (holding member 6) is provided, the imaging of a digital camera or the like is performed. The size and cost of the apparatus can be reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A material, a shape, a dimension, a form, a number, an arrangement | positioning location, etc. are related to the structure of this invention. It can be set and changed as appropriate without departing from the scope of the invention.

  For example, in the above-described embodiment, the prism 5 is exemplified as the bending optical element. However, the prism 5 is not limited thereto, and may be a mirror or the like. Further, in the above-described embodiment, the case where the bending optical element is disposed behind the second lens group 20 is exemplified. However, for example, the bending optical element may be disposed between the first lens group 10 and the second lens group 20. .

5 Prism 6 Prism Holding Member 6c Prism Holding Member Rack 6d Guide Shaft Restricting Member 6e Shooting Side Stopper 30 Third Lens Group 40 Fourth Lens Group 51 SW Motor 53 TW Motor 55 Zoom Ring Gear 56 Zoom Carrier Gear 57 Sun Gear Row 58 Zoom Planetary gear 61 Cam cylinder 80 Prism drive unit 85 Optical element drive gear 86 Guide shaft

Claims (3)

An optical element;
A holding member that is supported by two guide shafts arranged in parallel and holds the optical element;
A lens supported by the two guide shafts and movable along the axial direction of the two guide shafts;
A rack gear provided in parallel with the one guide shaft engaging portion to be engaged with one guide shaft of Oite the two guide shafts in the holding member,
An optical element drive gear for driving the holding member in the length direction of the two guide shafts by meshing with the rack gear and transmitting the driving force transmitted from the driving means to the rack gear by a rotational operation;
A guide shaft restricting member disposed at a position facing the optical element driving gear so as to sandwich the one guide shaft ;
Urging means for urging the holding member against a stopper member provided on the one guide shaft when the optical element is in a photographing position ;
The guide shaft restricting member is disposed at a position to receive a component force in the pressure angle direction of the optical element driving gear on the one guide shaft when the holding member is biased by the biasing means to the stopper member. A lens barrel characterized by being made .   The lens barrel according to claim 1, wherein the optical element is a prism. Imaging apparatus characterized by having a lens barrel according to claim 1 or 2.

Images