Patent ID: 6853503
Filing Date: 2005-02-08
Classification: G02B

Abstract:
1. An eccentricity-prevention mechanism for preventing eccentricity in relatively rotating lens-supporting rings, said eccentricity-prevention mechanism comprising: a pair of lens-supporting rings for supporting a pair of lens groups, respectively, said pair of lens-supporting rings being relatively moved in a direction of the optical axis, of said pair of lens groups, in accordance with relative rotation thereof; and a pair of positioning recesses and a follower projection formed on one and the other of opposed surfaces of said pair of lens-supporting rings, such that said follower projection engages with one of said pair of positioning recesses to define a relative position of said pair of lens-supporting rings, with respect to said optical axis, at a mutually close position and at a mutually distant position; wherein at least three said pairs of positioning recesses and at least three said follower projections are provided on said pair of lens-supporting rings at different positions in a circumferential direction respectively, so that eccentricity between said pair of lens-supporting rings is eliminated when all of said follower projections are concurrently brought into engagement with corresponding said positioning recesses.