JP2007003581A - Lens barrel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens barrel for precisely holding a moving lens group with small tilting/eccentricity. <P>SOLUTION: A lens holding mechanism which rotates a cam cylinder on an optical axis by zooming and moves the moving lens group along the optical axis in response thereto has a fixed cylinder which has a rectilinear guide groove, the cam cylinder with a plurality of guide grooves which radially engages with the outer periphery of the fixed cylinder and whose one end surface in the direction of the optical axis engages with the fixed cylinder, a cam follower which engages the rectilinear guide groove and cam grooves, a rectilinear cylinder which temporarily holds the cam follower and is disposed at the outer periphery of the cam cylinder, a moving lens holding lens barrel which holds a lens fixed fitted and fixed to the rectilinear cylinder and the lens, and a holding ring which is fitted to the fixed cylinder and has a holding ring engaged with the one end surface of the cam cylinder and engaging an internal-diameter surface of the rectilinear cylinder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for moving a lens group of a lens barrel used in a camera or the like.

As a lens barrel holding mechanism that realizes an operation of changing a focal length or the like by moving a lens group constituting a lens lens in recent years, particularly a zoom lens, in the optical axis direction,
(1) A fixed cylinder, a straight guide groove parallel to the optical axis provided in the fixed cylinder, a cam cylinder fitted to the outer diameter or inner diameter of the fixed cylinder and supported rotatably around the optical axis, and the cam cylinder It comprises a cam groove provided, a cam follower that engages with the linear guide groove and the cam groove, a linear cylinder that supports the cam follower, and a lens barrel that is fixed to the linear cylinder. That is, by rotating the cam barrel around the optical axis, the lens barrel moves back and forth in the optical axis direction along the shape of the cam groove (see, for example, Patent Document 1).
(2) A rectilinear cylinder holding a lens barrel is disposed on the outer diameter side of a fixed cylinder having a rectilinear guide groove, a cam cylinder having a plurality of cam grooves is disposed on the inner diameter of the fixed cylinder, and the cam cylinder is optically A mechanism for feeding the cam cylinder in the optical axis direction by rotating around the axis, and rotating the cam cylinder and moving a part of the cam cylinder straight in the optical axis direction; A structure for fitting is proposed (see, for example, Patent Document 2).
JP 07-294793 A Japanese Patent Laid-Open No. 04-184402

However, in the above conventional example,
(1) When the amount of movement of the lens barrel increases, the cam cylinder and the fixed cylinder increase in size in the optical axis direction, and at the same time, the length of the rectilinear cylinder or the distance between the cam follower and the lens barrel increases. Therefore, the tilt and decentering of the lens barrel due to the backlash between the cam follower, the cam groove, and the straight advance groove is further enlarged, which causes deterioration in optical performance.
(2) Although the tilting and eccentricity of the lens barrel attached to the rectilinear cylinder is reduced by a part of the cam cylinder supporting the rectilinear cylinder, a mechanism for extending the cam cylinder and Space is required and the structure is complicated. The other movable lens group has a fixed cylinder, and the fitting with the cam cylinder engaged with the fixed cylinder has a drawback that it is easily affected by component errors.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a lens barrel for holding a movable lens group with high accuracy with less tilting and eccentricity.

  In order to achieve the above object, a first aspect of the present invention is directed to a lens holding mechanism that rotates a cam cylinder around an optical axis by zooming and moves a moving lens group in the direction of the optical axis in response to the rotation. A fixed cylinder having a plurality of cam grooves having a diameter fitted to the outer periphery of the fixed cylinder and having one end surface in the optical axis direction engaged with the fixed cylinder, and engaged with the linear guide groove and the cam groove A cam follower, a rectilinear cylinder that integrally holds the cam follower and is positioned on the outer periphery of the cam cylinder, a moving lens holding barrel that holds a lens that is fixedly attached to the rectilinear cylinder, a lens, and the cam that is attached to the fixed cylinder The lens barrel is constituted by a holding ring that engages with one end face of the cylinder and engages with the inner diameter face of the straight-advance cylinder.

  According to a second aspect of the present invention, in the first aspect of the present invention, the cam cylinder is positioned in the optical axis direction by sandwiching one end between the fixed cylinder and the other end with the holding cylinder at both end faces, and holding the cam cylinder with respect to the fixed cylinder. An optical axis direction backlash of the cam cylinder is supported so as to be adjustable by adjusting the position of the cylinder.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the radial positions of the rectilinear cylinder and the holding cylinder are positioned via a plurality of balls.

According to the present invention, the following effects can be obtained.
(1) By adjusting the attachment and screwing of the holding ring to the fixed cylinder, the play in the optical axis direction of the cam cylinder can be made almost zero.
(2) Since the straight cylinder can be diameter-fitted by the holding ring directly fixed to the fixed cylinder, the mounting accuracy is higher than that of the diameter fitting via the cam cylinder.
(3) As the holding of the rectilinear cylinder is supported by the holding ring and the cam follower that are separated in the optical axis direction, it is synonymous with the fact that the fitting length has become longer. Eccentricity can be suppressed.

  Due to the above features, it has become possible to stabilize the holding of the movable lens group with higher accuracy and to reduce the amount of tilting and eccentricity than before.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Embodiment 1>
FIG. 1 shows Embodiment 1 of the present invention, and is a cross-sectional view of an interchangeable lens barrel attached to a single-lens reflex camera cut along a plane including the optical axis in the WIDE state, and FIG. 2 is TELE showing Embodiment 1 of the present invention. It is sectional drawing cut | disconnected by the plane containing the optical axis of a state. Parts not relevant to the gist of the present invention are not shown.

  In the figure, reference numeral 1 denotes a fixed cylinder, which is fixed to a camera or the like (not shown). The fixed cylinder 1 has a plurality of rectilinear guide grooves 1a extending in the optical axis direction equally in the circumferential direction. An inner diameter surface 2 b of the cam cylinder 2 is fitted to the outer peripheral surface 1 b of the fixed cylinder 1. The cam cylinder 2 has a plurality of cam grooves 2a equally in the circumferential direction. One end surface 2c of the cam cylinder 2 slides with the flange surface 1c of the fixed cylinder.

  Reference numeral 3 denotes a retaining ring, which is diameter-fitted to the fixed cylinder 1d at the part 3a and is screwed to the male screw 1e part of the fixed cylinder 1d at the female screw 3b part. At that time, the holding ring 3 is screwed into the fixed cylinder 1 until the 3c surface of the holding ring 3 comes into contact with the end surface 2d of the cam cylinder 2, and is fixed to the fixed cylinder by bonding or a screw (not shown). That is, the position of the cam cylinder 2 in the optical axis direction is sandwiched between the end faces 2c and 2d by 1c and 3c with an appropriate gap, and is supported only by the fixed cylinder 1 so as to be rotatable about the optical axis. By adjusting the screwing amount of the holding ring 3, the play in the optical axis direction of the cam cylinder 2 can be adjusted, so that it is possible to individually cope with variations in component dimensions.

  Reference numeral 4 denotes a cam follower, which simultaneously engages with the linear guide groove 1a and the cam groove 2a. When the cam cylinder 2 rotates about the optical axis with respect to the fixed cylinder 1, the cam follower 4 is formed in the optical axis direction due to the shape of the cam groove 2a. It is supported movably. Reference numeral 5 denotes a rectilinear cylinder which is fixed integrally with the cam follower 4 by a cam follower fixing screw 6 and moves in the optical axis direction by the rotation of the cam cylinder 2. The surface 5a must be fitted to the outer diameter surface of the cam cylinder 2 or have an appropriate diameter play when the position is uniquely determined by the plurality of cam followers described above.

  Further, the 5b surface of the inner diameter of the rectilinear cylinder 5 is diameter-fitted with the outer peripheral 3d surface of the holding ring 3. Reference numeral 7 denotes a lens holding barrel that holds the moving lens group 8, and is fixed to the 5c surface of the rectilinear tube 5 by screws or the like on the surface 7a.

With the above configuration, the objective of the present embodiment is to move the moving lens group straightly in the optical axis direction by rotating the cam cylinder 2 around the optical axis from the WIDE state (FIG. 1) to the TELE state (FIG. 2). It is. In order to reduce the tilt and eccentricity of the moving lens group with respect to the fixed cylinder, as a feature of the present embodiment,
(1) By adjusting the attachment and screwing of the holding ring to the fixed cylinder, the play in the optical axis direction of the cam cylinder can be made almost zero.
(2) Since the straight cylinder can be diameter-fitted by the holding ring directly fixed to the fixed cylinder, the mounting accuracy is higher than that of the diameter fitting via the cam cylinder.
(3) Since the holding cylinder is supported by the holding ring and the cam follower or the 5a surface that are separated from each other in the optical axis direction, it is synonymous with the fact that the fitting length is increased. Can be suppressed.
Therefore, it is possible to stabilize the holding of the moving lens group with higher accuracy than before, and to suppress the amount of tilting and decentering.

<Embodiment 2>
3 is a cross-sectional view of an interchangeable lens barrel attached to a single-lens reflex camera showing Embodiment 2 of the present invention, cut along a plane including the optical axis in the WIDE state, and FIG. 4 is a TELE state showing Embodiment 2 of the present invention. It is sectional drawing cut | disconnected by the plane containing this optical axis. Parts not relevant to the gist of the present invention are not shown.

  This embodiment is a proposal for reducing the movement resistance of the straight cylinder, and there is almost no difference from the first embodiment. Reference numeral 9 denotes a ball, which is characterized in that it is supported by a plurality of balls instead of the diameter fitting between the holding ring and the straight cylinder inner diameter. It is possible to rotate the cam cylinder with a small force. That is, it becomes possible to reduce the operating torque during zooming.

  As mentioned above, although preferable embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

It is sectional drawing cut | disconnected by the plane containing the optical axis of the WIDE state of the interchangeable lens barrel attached to the single-lens reflex camera which shows Embodiment 1 of this invention. It is sectional drawing cut | disconnected by the plane containing the optical axis of the TELE state of the interchangeable lens barrel attached to the single-lens reflex camera which shows Embodiment 1 of this invention. It is sectional drawing cut | disconnected by the plane containing the optical axis of the WIDE state of the interchangeable lens barrel attached to the single-lens reflex camera which shows Embodiment 2 of this invention. It is sectional drawing cut | disconnected by the plane containing the optical axis of the TELE state of the interchangeable lens barrel attached to the single-lens reflex camera which shows Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed cylinder 2 Cam cylinder 3 Holding cylinder 4 Cam follower 5 Straight advance cylinder 6 Cam follower fixing screw 7 Lens holding barrel 8 Moving lens group 9 Ball

Claims (3)

  A lens holding mechanism that rotates the cam cylinder around the optical axis by zooming and moves the moving lens group in the optical axis direction in response to the rotation is fitted to the fixed cylinder having the straight guide groove and the outer circumference of the fixed cylinder. A cam cylinder having a plurality of cam grooves whose one end surface in the optical axis direction is engaged with the fixed cylinder, a cam follower engaged with the linear guide groove and the cam groove, and an outer periphery of the cam cylinder integrally holding the cam follower A moving lens holding barrel for holding a lens attached to and fixed to the rectilinear cylinder, a lens, and an inner diameter surface of the rectilinear cylinder that is attached to one end surface of the cam cylinder A lens barrel comprising a holding ring that engages with the lens barrel.   The optical axis direction position of the cam cylinder can be adjusted by adjusting the position of the holding cylinder with respect to the fixed cylinder by sandwiching one end between the fixed cylinder and the other end with the holding cylinder at both end faces. The lens barrel according to claim 1, wherein the lens barrel is supported by the lens barrel.   3. The lens barrel according to claim 1, wherein radial positions of the rectilinear cylinder and the holding cylinder are positioned via a plurality of balls.

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