JP2004029619A - Lens barrel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the inclination of a cam cylinder and image swinging or the like in a lens barrel provided with the cam cylinder supported to a fixed cylinder so as to be freely turned and retracted. <P>SOLUTION: The lens barrel is provided with the fixed cylinder 20 which has a cam groove 21 on an inner peripheral surface 20a and the cam cylinder 30 which has a follower pin 31 to be inserted to the cam groove 21 on an outer peripheral surface 30a, and is arranged in a nest shape on the inner side of the fixed cylinder 20. On the outer peripheral surface 30a of the cam cylinder 30, two circular-arcuate ribs 33 and 34 projected so as to be abutted on the inner peripheral surface 20a of the fixed cylinder 20 are provided on positions holding a rack part 32 therebetween in an optical axis direction over a prescribed region in a peripheral direction. Thus, the inclination of the cam cylinder 30 is prevented, and an image swinging phenomenon or the like is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lens barrel for moving a lens in an optical axis direction, and more particularly, to a lens barrel having a cam groove and a follower pin as a driving mechanism and a plurality of lens barrels being nested so as to be able to relatively protrude and retract. .
[0002]
[Prior art]
As a conventional lens barrel, a lens holding frame holding a lens, a cylindrical cam barrel for housing the lens holding frame, a cylindrical fixed barrel for nesting the cam barrel, and the like are provided on the lens holding frame. Inserting the follower pin into the cam groove provided on the inner peripheral surface of the cam cylinder, and inserting the follower pin provided on the outer peripheral surface of the cam cylinder into the cam groove provided on the inner peripheral surface of the fixed cylinder, It is known to rotate the lens so as to protrude and retract in the optical axis direction and to move a lens holding frame (lens) in the optical axis direction.
[0003]
In this lens barrel, the relationship between the cam barrel and the fixed barrel is such that a predetermined interval is provided between the outer circumferential surface of the cam barrel and the inner circumferential face of the fixed barrel, and a follower pin projecting from the outer circumferential face of the cam barrel is provided. One rib, which is inserted into a cam groove formed on the inner peripheral surface of the fixed cylinder and protrudes from the vicinity of the follower pin on the outer peripheral surface of the cam cylinder, slidably contacts the inner peripheral surface of the fixed cylinder. By being in contact with each other, the cam cylinder is supported so as to rotate and protrude and retract with respect to the fixed cylinder.
[0004]
[Problems to be solved by the invention]
By the way, in the above lens barrel, the cam barrel is supported by, for example, three follower pins arranged on the same plane with respect to the fixed barrel and one rib close to the cam barrel, and the cam barrel is internally provided. In order to support the lens holding frame, especially when the cam barrel projects from the fixed barrel and the lens holding frame extends from the cam barrel to the projecting side, a bending moment acts on the distal end side of the cam barrel to cause the fixed barrel to move. On the other hand, the cam cylinder may be inclined. This tilt may cause a shift of the optical axis, and may cause an image shake phenomenon in a captured image captured by an image sensor such as a CCD.
[0005]
In order to prevent the cam cylinder from tilting and image shaking, the play between the cam cylinder on which the follower pin is provided and the fixed cylinder on which the cam groove is provided is set as small as possible, and the width (thickness) of one rib is set to the optical axis. Although it is conceivable to expand in the direction, the driving load increases due to an increase in frictional force in a region where relative movement occurs, and when a cam cylinder is formed of a resin material, molding defects such as sink marks may occur. There is a risk of inviting.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and an object of the present invention is to provide a simple structure, which can prevent the cam cylinder from tilting and image swinging phenomena, and achieve desired optical characteristics. It is an object of the present invention to provide a lens barrel that can perform a smooth out-and-out operation while ensuring the above.
[0007]
[Means for Solving the Problems]
The lens barrel of the present invention has a fixed cylinder having a cam groove on the inner peripheral surface that performs a cam action in the optical axis direction, and an outer peripheral surface that holds a lens inside and a follower pin inserted into the cam groove is separated from the inner peripheral surface. A lens barrel for moving the lens in the optical axis direction by rotating the cam cylinder to move the lens in the optical axis direction, wherein an outer peripheral surface of the cam cylinder has an optical axis. A plurality of protruding portions are provided which are formed at predetermined intervals in the direction and project so as to contact the inner peripheral surface of the fixed cylinder over at least a predetermined region in the circumferential direction.
According to this configuration, the cam barrel is supported by the follower pins and the plurality of protrusions that are separated from each other in the optical axis direction with respect to the fixed barrel. Therefore, the cam cylinder is prevented from tilting, and the image swing phenomenon and the like due to the shift of the optical axis are prevented.
[0008]
In the above configuration, it is possible to adopt a configuration in which the protruding portion is a rib formed to protrude in an arc shape over a predetermined region in the circumferential direction.
According to this configuration, the cam cylinder is supported by the follower pins and the plurality of ribs formed on the outer peripheral surface of the fixed cylinder with respect to the fixed cylinder, thereby suppressing an increase in frictional force on the sliding surface, The tilt and the image swing phenomenon are prevented. In particular, when the cam cylinder is molded from a resin material, by forming the protruding portion in a rib shape, sink marks and the like during molding can be prevented.
[0009]
In the above configuration, an arc-shaped rack portion to which a rotational driving force is transmitted is formed on the outer peripheral surface of the cam cylinder, and the plurality of protruding portions are arranged separately at positions sandwiching the rack portion in the optical axis direction. , Configuration can be adopted.
According to this configuration, when the cam cylinder is rotated by the gear meshing with the rack, the pressing force generated by the meshing of the gear is reduced by the plurality of protrusions (or the plurality of protrusions formed across the rack in the optical axis direction). , A plurality of arc-shaped ribs), the inclination of the cam cylinder is reliably prevented even when a rotational driving force is applied.
[0010]
In the above-described configuration, the cam barrel has a lens holding frame on which a follower pin is formed while holding the lens, and the cam cylinder has a cam function for inserting the follower pin and moving the lens holding frame in the optical axis direction on an inner peripheral surface thereof. A configuration having a cam groove can be adopted.
According to this configuration, the lens holding frame also moves in the optical axis direction along with the rotation of the cam barrel, and when the lens is extended, the bending moment corresponding to the load of the lens holding frame is applied to the tip of the cam barrel. However, even in this case, since the cam cylinder is supported by a plurality of protruding portions (or a plurality of arc-shaped ribs) in addition to the follower pins, the inclination of the cam cylinder is ensured. Is prevented.
[0011]
In the above configuration, on the outer peripheral surface of the cam barrel, three follower pins arranged at equal intervals in the circumferential direction, an arc-shaped rack portion to which rotational driving force is transmitted at a position separated from the follower pin in the optical axis direction, A configuration having two ribs arranged at positions sandwiching the rack portion in the axial direction can be adopted.
According to this configuration, the cam cylinder is supported by the fixed cylinder by the three follower pins and the two arc-shaped ribs located at positions sandwiching the rack. That is, the cam cylinder is reliably prevented from being inclined with a simple structure, and the image swing phenomenon or the like due to the displacement of the optical axis is reliably prevented.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
1 to 8 show an embodiment of a lens barrel according to the present invention. FIG. 1 is a front view of the apparatus, FIG. 2 is an exploded sectional view of the apparatus, and FIGS. 3 and 4 are partial sectional views of the apparatus. 5 and 6 are side views of the cam cylinder, and FIGS. 7 and 8 are front and rear views of the cam cylinder.
[0013]
As shown in FIGS. 1 and 2, the lens barrel has a low-pass filter 11 having a substantially rectangular outline, a base 10 on which a CCD 12 as an image sensor is mounted, a fixed cylinder 20 fixed to the base 10, The cam barrel 30 is rotatably and linearly supported inside the cylinder 20, the first lens group 40 and the second lens group 50 are movably supported in the optical axis direction L inside the cam cylinder 30, and the base 10. A third lens group 60 movably supported in the optical axis direction L, a driving mechanism 70 for driving the cam barrel 30, a driving mechanism 80 for driving the third lens group 60, and the like.
[0014]
2 to 4, the fixed cylinder 20 is formed in a cylindrical shape having an axis in the optical axis direction L, and is fixed to the base 10. As shown in FIGS. 2 to 4, three inner circumferential surfaces 20 a of the fixed cylinder 20 are arranged at equal intervals (approximately 120 degrees) in the circumferential direction and exert a cam action on three follower pins 31 described later. A cam groove 21 (partially omitted in the drawing) is formed.
[0015]
As shown in FIGS. 2 to 4 and 5 to 8, the cam cylinder 30 is formed in a cylindrical shape from a resin material, and is nested coaxially inside the fixed cylinder 20.
The outer peripheral surface 30a of the cam cylinder 30 is located at a position separated from the inner peripheral surface 20a of the fixed cylinder 20, and the outer peripheral surface 30a has an equal interval (about 120 degrees) in the circumferential direction as shown in FIGS. 3), an arc-shaped rack portion 32 to which rotational driving force is transmitted from the outside, and a position sandwiching the rack portion 32 at the rear of the follower pin 31 in the optical axis direction L at a predetermined distance from the follower pin 31. Two ribs 33 and 34 are formed as the arranged protrusions.
[0016]
As shown in FIGS. 7 and 8, the two ribs 33 and 34 are partially removed from the entire circumference so as not to hinder the engagement between the rack 32 and the driving mechanism 70 (a gear 77 described later). It is formed in an arc shape so as to continuously protrude at least over a predetermined region in the circumferential direction (as two parallel protruding portions).
Further, since the ribs 33 and 34 are not formed thick but narrow in the optical axis direction L, when these ribs 33 and 34 are formed integrally with the cam cylinder 30 by a resin material, Molding defects such as sink marks and warpage can be prevented.
Further, although the ribs 33 and 34 slidably contact the inner peripheral surface 20a of the fixed cylinder 20, the ribs 33 and 34 are formed to be narrow, so that the frictional force on the sliding surface is suppressed, The cam cylinder 30 can rotate smoothly.
[0017]
As shown in FIGS. 2 to 4 and 8, three cam grooves 35 acting on the first lens group 40 in the optical axis direction L are formed in the inner peripheral surface 30b of the cam cylinder 30. Three cam grooves 36 that act on the second lens group 50 are formed, and as shown in FIGS. 2 to 4, the optical axis while regulating the rotation of the first lens group 40 and the second lens group 50. A guide cylinder 37 for guiding in the direction L is arranged.
[0018]
The three follower pins 31 of the cam cylinder 30 are inserted into the three cam grooves 21 of the fixed cylinder 20, and the two arc-shaped ribs 33 and 34 are slidably in contact with the inner peripheral surface 20a. Thus, the cam barrel 30 is supported coaxially with the fixed barrel 20 and rotated forward and backward in the optical axis direction L by being rotated by the drive mechanism 70, and the first lens group 40 and the second lens group. The group 50 is moved in the optical axis direction L to perform variable power driving.
[0019]
As described above, the cam cylinder 30 is supported by the fixed cylinder 20 by the two arc-shaped ribs 33 and 34 arranged at positions sandwiching the three follower pins 31 and the rack 32. That is, since the cam cylinder 30 is supported by the follower pin 31 and the plurality of ribs 33 and 34 separated by a predetermined distance from the follower pin 31 in the optical axis direction L, the inclination with respect to the fixed cylinder 20 is reliably prevented. .
[0020]
As shown in FIGS. 2 to 4, the first lens group 40 includes a lens holding frame 41 for holding the lens G1, and three follower pins 42 (one in FIG. 2) formed in the lens holding frame 41 and inserted into the cam grooves 35. Part is omitted). Then, the first lens group 40 moves forward and backward in the optical axis direction L by the rotation of the cam barrel 30.
[0021]
As shown in FIGS. 2 to 4, the second lens group 50 includes a lens holding frame 51 for holding the lens G2, and three follower pins 52 (one in FIG. 2) formed in the lens holding frame 51 and inserted into the cam groove 36. And a shutter unit S held by a lens holding frame 51 and the like. Then, the second lens group 50 moves forward and backward in the optical axis direction L by the rotation of the cam barrel 30.
[0022]
The third lens group 60 includes a lens holding frame 61 that holds the lens G3, as shown in FIGS. As shown in FIGS. 1 and 2, the lens holding frame 61 is provided with a step motor 81 disposed outside the fixed cylinder 20, a lead screw driven by the step motor 81, and a screw held by the lens holding frame 61. The focusing mechanism is performed by moving forward and backward in the optical axis direction L by the driving mechanism 80 including the combined nuts and the like.
[0023]
As shown in FIGS. 1 and 2, the drive mechanism 70 includes a DC motor 71 fixed to the base 10, a worm 72 fixed to a drive shaft 71 a thereof, a worm wheel 73 supported by the base 10 and meshing with the worm 72, A worm 74 integrally formed coaxially with the worm wheel 73, a worm wheel 75 supported by the base 10 and meshing with the worm 74, a gear 76 integrally formed coaxially with the worm wheel 75, and supported by the base 10. The gear 76 is formed by a gear 77 and a gear 77 that meshes with the rack 32.
[0024]
That is, when the DC motor 71 rotates, the cam cylinder 30 relatively rotates with respect to the fixed cylinder 20 via the worm 72, the worm wheel 73, the worm 74, the worm wheel 75, the gear 76, and the gear 77. Then, the first lens group 40 and the second lens group 50 are respectively extended (forward) or retracted (retracted) in the optical axis direction L, for example, the retracted position at the time of non-photographing shown in FIG. 4 through the telephoto end photographing position to the wide-angle end photographing position shown in FIG. 4, and is moved to a desired zooming position so that a wide range of photographing can be performed.
[0025]
As shown in FIG. 4, in a state where the cam barrel 30 projects most from the fixed barrel 20 and the first lens group 40 projects most from the cam barrel 30, the distal end of the cam barrel 30 is caused by the load of the first lens group 40. When the bending moment acts, the cam cylinder 30 tends to hang downward (incline) in the vertical direction. As described above, the three follower pins 31 and the two arc-shaped ribs 33 and 34 The cam cylinder 30 is supported in close contact with the fixed cylinder 20 at a predetermined interval in the optical axis direction L. Therefore, the cam cylinder 30 is securely held at a predetermined position without being inclined. Accordingly, the optical axis is prevented from being shifted, and the image swing phenomenon of the captured image in the CCD 12 or the like can be prevented.
[0026]
Next, a general operation when the above-described lens barrel is mounted on a digital camera will be described. First, at the time of non-shooting, the first lens group 40, the second lens group 50, and the cam barrel 30 are in the retracted position retracted rearward in the optical axis direction L as shown in FIG. In this retracted position, the first lens group 40 and the second lens group 50 are at the most retracted positions, so that almost no load acts on the tip side of the cam cylinder 30, and the cam cylinder 30 is connected to the fixed cylinder 20. It is securely supported on the same axis.
[0027]
When the cam cylinder 30 is rotated from the retracted position by the driving mechanism 70, the follower pin 31 moves while being guided by the cam groove 21, and the cam cylinder 30 is extended forward in the optical axis direction L. By the rotation of 30, the follower pins 42 and 52 are guided by the cam grooves 35 and 36, respectively, so that the first lens group 40 and the second lens group 50 first extend to the telephoto end photographing position, and then as shown in FIG. To the wide-angle shooting position, which is the maximum extension position. On the other hand, the third lens group 60 is moved to a focusing position corresponding to the positions of the first lens group 40 and the second lens group 50 by a driving mechanism (such as a step motor 81).
[0028]
In the feeding operation of the cam cylinder 30, a rotational driving force is transmitted to the cam cylinder 30 from the gear 77 to the rack 32. This rotational driving force acts as a biasing force that presses the cam cylinder 30 toward one side in the radial direction, but the cam cylinder 30 always applies three follower pins 31 and two ribs 33 and 34 to the fixed cylinder 20. Supported by Thereby, the cam cylinder 30 is reliably supported coaxially with the fixed cylinder 20 at any of the extended positions, and the inclination thereof is reliably prevented.
[0029]
Therefore, when the image photographed by the CCD 12 can be confirmed on the monitor during the feeding operation, a clear image without image shaking or the like is displayed on the monitor, and the operator confirms the displayed image. It is possible to perform a desired zooming operation while doing so.
[0030]
As shown in FIG. 4, also at the maximum extension position where the cam barrel 30 and the first lens group 40 protrude most, the cam barrel 30 is similarly formed by three follower pins 32 and two arc-shaped ribs 33 and 34. Since it is securely supported by the fixed cylinder 20, its inclination, image swing phenomenon, and the like are reliably prevented.
Also, when the cam cylinder 30 receives an external impact force due to a drop or the like in the maximum extension position, the two ribs 33 and 34 securely hold the cam cylinder 30 with respect to the fixed cylinder 20. Therefore, not only the inclination of the cam cylinder 30 is prevented, but also the rack portion 32 meshing with the gear 77 is prevented from falling off, and the initial function is reliably maintained.
[0031]
In the above-described embodiment, the two ribs 33 and 34 are shown as the projecting portions formed on the outer peripheral surface 30a of the cam cylinder 30. However, the present invention is not limited to this, and a predetermined interval is provided in the optical axis direction L. As long as it is formed, a projecting piece that is not continuous in an arc shape in the circumferential direction but partially projects may be radially provided.
Further, in the above-described embodiment, the configuration according to the present invention is employed in the lens barrel that supports the plurality of lens groups 40 and 50 inside the cam barrel 30. However, the present invention is not limited to this. The configuration according to the present invention may be adopted in a configuration in which one lens group is directly held with respect to 30 and the cam barrel 30 functions as a lens holding frame.
[0032]
【The invention's effect】
As described above, according to the lens barrel of the present invention, the cam barrel having the follower pin inserted into the cam groove on the outer peripheral surface is nested with respect to the fixed cylinder having the cam groove on the inner peripheral surface. In the configuration, on the outer peripheral surface of the cam cylinder, a plurality of protrusions formed at predetermined intervals in the optical axis direction and projecting so as to contact the inner peripheral surface of the fixed cylinder over at least a predetermined region in the circumferential direction. With the provision, the inclination of the cam cylinder with respect to the fixed cylinder can be prevented, and the image swing phenomenon and the like can be prevented.
In particular, by adopting a rib formed to project in an arc shape over a predetermined area in the circumferential direction as the protruding portion, the inclination and image sway phenomenon can be suppressed while suppressing an increase in frictional force on the sliding surface. In addition, when the cam cylinder is formed of a resin material, by forming the protruding portion into a thin rib shape, it is possible to prevent sink marks and the like during molding.
Further, by arranging a plurality of protrusions (ribs) so as to sandwich the arc-shaped rack formed on the outer peripheral surface of the cam cylinder, even when a rotational driving force is applied to the cam cylinder via the rack, The inclination and the like of the cam cylinder are reliably prevented.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of a lens barrel according to the present invention.
FIG. 2 is a developed sectional view showing one embodiment of a lens barrel according to the present invention.
FIG. 3 is a longitudinal sectional view showing a state where a cam cylinder and a lens holding frame (lens) are in a collapsed position.
FIG. 4 is a longitudinal sectional view showing a state where a cam cylinder and a lens holding frame (lens) are at a maximum extension position.
FIG. 5 is a side view showing a cam cylinder.
FIG. 6 is a side view showing a cam cylinder.
FIG. 7 is a front view showing a cam cylinder.
FIG. 8 is a rear view showing the cam barrel.
[Explanation of symbols]
10 Base 11 Low-pass filter 12 CCD
Reference Signs List 20 fixed cylinder 20a inner peripheral surface 21 cam groove 30 cam cylinder 30a outer peripheral surface 30b inner peripheral surface 31 follower pin 32 rack part 33, 34 plural ribs (plural projecting parts)
35, 36 Cam groove 40 First lens group G1 Lens 41 Lens holding frame 42 Follower pin 50 Second lens group G2 Lens 51 Lens holding frame 52 Follower pin 60 Third lens group G3 Lens 61 Lens holding frame 70 Drive mechanism 71 DC motor 72, 74 Worm 73, 75 Worm wheel 76, 77 Gear L Optical axis direction

Claims (5)

A fixed cylinder having a cam groove on the inner peripheral surface that performs a cam action in the optical axis direction, and a cam cylinder having a follower pin that holds a lens inside and is inserted into the cam groove on an outer peripheral surface separated from the inner peripheral surface. A lens barrel for moving the lens in the optical axis direction by moving the cam cylinder in the optical axis direction by the rotation of the cam cylinder;
On the outer peripheral surface of the cam cylinder, provided are a plurality of protrusions formed at predetermined intervals in the optical axis direction and projecting so as to contact the inner peripheral surface over at least a predetermined region in the circumferential direction,
A lens barrel characterized in that: The protrusion is a rib formed to protrude in an arc shape over a predetermined region in the circumferential direction,
The lens barrel according to claim 1, wherein: On the outer peripheral surface of the cam cylinder, an arc-shaped rack portion to which a rotational driving force is transmitted is formed,
The plurality of protrusions are spaced apart at a position sandwiching the rack in the optical axis direction,
The lens barrel according to claim 1, wherein: Having a lens holding frame on which a follower pin is formed while holding the lens,
The cam barrel has, on its inner peripheral surface, a cam groove that acts as a cam for inserting the follower pin and moving the lens holding frame in the optical axis direction.
The lens barrel according to any one of claims 1 to 3, wherein: On the outer peripheral surface of the cam cylinder, three follower pins arranged at equal intervals in the circumferential direction, an arc-shaped rack portion to which a driving force is transmitted at a position separated from the follower pins in the optical axis direction, and an optical axis direction And two ribs arranged at positions sandwiching the rack portion.
The lens barrel according to any one of claims 2 to 4, wherein:

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