Optical: systems and elements – Lens – With support
Reexamination Certificate
2003-02-12
2003-09-23
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With support
C359S704000, C359S694000
Reexamination Certificate
active
06624955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel which can be used as a photographing lens barrel of a camera.
2. Description of the Related Art
A conventional lens barrel in which each of linearly guided front and rear lens groups is provided with a set of follower pins which are respectively engaged in a corresponding set of cam grooves (cam slots) formed on a rotating cam ring so that the linearly guided front and rear lens groups move in an optical axis direction without rotating about the optical axis by rotation of the cam ring to move each of the front and rear lens groups between an accommodation position and a ready-to-photograph position in front of the accommodation is known in the art.
However, if the diameter of the cam ring is small, a reduction of the pitch of each cam groove (i.e., a reduction of the angle of inclination of each cam groove relative to a circumferential direction of the cam ring) causes the set of cam grooves for the first lens group and the set of cam grooves for the second lens group to interfere with each other, or causes the front and rear lens groups positioned at their respective accommodation positions to interfere with each other, to thereby get stuck (jam) thereat even if the cam ring is rotated to move the first and second lens groups forward from their respective accommodation positions.
Among such type of lens barrels, in a lens barrel required to be designed compact as much as possible, it is sometimes desirable not to rotate the cam ring for the purpose of preventing the cam ring from interfering with any peripheral elements while moving the cam ring in the optical axis direction in a predetermined moving section of the cam ring from a fully retracted position thereof.
Moreover, in the above described conventional type of lens barrels, backlash occurs between the cam ring and a guiding mechanism for guiding the cam ring in the optical axis direction when the cam ring is moved to a ready-to-photograph position thereof. Such backlash deteriorates the performance of the focusing system.
SUMMARY OF THE INVENTION
The present invention provides a lens barrel having front and rear lens groups and a cam ring on which cam grooves for driving the front and rear lens groups are formed, wherein front and rear lens groups can be driven to move forward smoothly from their respective accommodation positions in an optical axis direction by rotation of the cam ring even if the angle of inclination of each cam groove formed thereon with respect to a circumferential direction of the cam ring is small.
The present invention provides a lens barrel in which the cam ring is prevented from interfering with any peripheral elements while moving in the optical axis direction in a predetermined moving section of the cam ring from a fully retracted position thereof.
The present invention provides a lens barrel in which backlash is prevented from occurring between the cam ring and a guiding mechanism for guiding the cam ring in the optical axis direction with a simple mechanism.
For example, in an embodiment, a lens barrel is provided, including a front lens frame which supports a front lens group and includes a first cam follower, the front lens frame being guided linearly in an optical axis direction without rotating about the optical axis; a rear lens frame which supports a rear lens group and includes a second cam follower; a cam ring driven to rotate about the optical axis, the cam ring including a first cam groove and a second cam groove in which the first cam follower and the second cam follower are respectively engaged; the first cam groove including a first moving section for moving the front lens frame in the optical axis direction, and a first accommodation section for moving the front lens frame behind a position of the front lens frame of which the first follower is engaged in the first moving section; the second cam groove including a second moving section for moving the rear lens frame in the optical axis direction, and a second accommodation section for moving the rear lens frame behind a position of the rear lens frame of which the second follower is engaged in the second moving section, the second accommodation section including an accommodation position at which the rear lens frame is positioned rearmost; and a guiding mechanism, provided between the front lens frame and the rear lens frame, for allowing the rear lens frame to rotate about the optical axis relative to the front lens frame when the second cam follower is engaged in a vicinity of the accommodation position of the second accommodation section, and for prohibiting the rear lens frame from rotating about the optical axis relative to the front lens frame while allowing the rear lens frame to move only in the optical axis direction relative to the front lens frame when the second cam follower is engaged in a section of the second cam groove which includes the second moving section and excludes the vicinity of the accommodation position.
The lens barrel can further include a shutter unit fixed to the rear lens frame; and a flexible PWB which extends rearward from the shutter unit so that a drive signal can be transmitted to the shutter unit via the flexible PWB.
The lens barrel can further include an elastic band which is engaged with the flexible PWB to pull a portion of the flexible PWB in a direction away from the optical axis.
The elastic band can be a rubber band.
The multi-direction guiding mechanism can include a linear guide groove formed on an inner peripheral surface of the front lens frame to extend parallel to the optical axis; a rotation-permitting groove, formed at a front end of the linear guide groove, which communicatively connects with the linear guide groove, a width of the rotation-permitting groove being greater than a width of the linear guide groove in a circumferential direction of the front lens frame; and a linear guide projection, formed on the rear lens frame, which is engaged in the rotation-permitting groove when the second cam follower is engaged in the vicinity of the accommodation position, and which is engaged in the linear guide groove when the second cam follower is engaged in the section of the second cam groove which includes the second moving section and excludes the vicinity of the accommodation position.
The front lens frame can include an inner flange for supporting the front lens group, a circumferential opening being formed on the front lens frame. The rear lens frame can include a front projecting portion, on which the linear guide projection is formed, the front projecting portion projecting forward to extend through the inner flange through the circumferential opening when the second cam follower is engaged in the vicinity of the accommodation position.
The inner flange can be formed on the front lens frame at a front end thereof.
The lens barrel can be a zoom lens barrel, wherein the first moving section and the second moving section constitute a first zooming section and a second zooming section for moving the front lens group and the rear lens group to perform a zooming operation, respectively.
The rear lens frame can rotate about the optical axis via rotation of the cam ring when the second cam follower is engaged in the vicinity of the accommodation position.
In another embodiment, a lens barrel is provided, including a front lens frame which supports a front lens group and includes a first cam follower, the front lens frame being guided linearly in an optical axis direction without rotating about the optical axis; a rear lens frame which supports a rear lens group and includes a second cam follower; a cam ring driven to rotate about the optical axis, the cam ring including a continuous cam groove in which the first cam follower and the second cam follower are engaged; wherein the continuous cam groove includes a first moving section for moving the front lens group in the optical axis direction; a first accommodation section for moving the front lens frame behind a position of the
Nakamura Satoru
Nomura Hiroshi
Okuda Isao
Yamazaki Yoshihiro
Greenblum & Bernstein P.L.C.
Mack Ricky
Pentax Corporation
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