Patent ID: 6987929

Claim:
A cam mechanism comprising: a cam ring; and a linearly movable frame movable by said cam ring along an optical axis of an optical system without rotating, by engagement of a first and a second plurality of cam grooves located on said cam ring with a corresponding first and second plurality of cam followers located on said linearly movable frame, when said cam ring is rotated, said linearly movable frame supporting at least one optical element of said optical system, wherein said first plurality of cam grooves are located at different positions than positions of said second plurality of cam grooves, in both said optical axis direction and a circumferential direction of said cam ring, and respectively trace substantially a same reference cam diagram; and wherein said first plurality of cam followers are located at different positions than positions of said second plurality of cam followers, in both said optical axis direction and a circumferential direction of said linearly movable frame, and are engageable in said plurality of cam grooves, respectively.