Patent ID: 7773313
Filing Date: 2010-08-10
Classification: G03B

Abstract:
1. A cam mechanism of a retractable zoom lens which can move to a ready-to-photograph state which enables a zoom optical system to perform a photographing operation, a retracted state to accommodate said zoom optical system, and a transition state between said ready-to-photograph state and retracted state, wherein said cam mechanism comprises: a cam ring having cam grooves on a peripheral surface of said cam ring; and a driven member which includes cam followers respectively engaged in said cam grooves, said driven member supporting at least a part of said zoom optical system, and wherein said driven member is supported to be movable relative to said cam ring in an optical axis direction, said cam mechanism moving said driven member forward and rearward in said optical axis direction via engagement of said cam followers with said cam grooves in accordance with relative rotation between said driven member and said cam ring, wherein at least one front cam groove and at least one rear cam groove constitute said cam grooves and are formed at different positions at least in said optical axis direction, said front and rear cam grooves having substantially the same reference cam diagram, being formed in a manner such that a front part of said front cam groove and a rear part of said rear cam groove are omitted from said reference cam diagram, and said front and rear cam grooves having at least one front end opening and at least one rear end opening on a front end surface and a rear end surface of said cam ring, respectively, wherein at least one front cam follower and at least one rear cam follower constitute said cam followers and are engaged in said front cam groove and said rear cam groove, respectively, said front and rear cam followers being formed on said driven member at different positions in said optical axis direction, wherein said front cam follower is disengaged from said front cam groove while said rear cam follower is engaged in said rear cam groove when said driven member is positioned at a limit of forward movement thereof, and said rear cam follower is disengaged from said rear cam groove while said front cam follower is engaged in said front cam groove when said driven member is positioned at a limit of rearward movement thereof, wherein each of said front and rear cam grooves include a normal-width section for guiding an associated said cam follower with substantially no play, and a wide-width section, which is greater in width than said normal-width section, in which said associated cam follower is loosely engageable therein, wherein, when said retractable zoom lens is set at said ready-to-photograph state, one of said front and rear cam followers is engaged in said normal-width section of one associated said cam groove, and the other of said front and rear cam followers is positioned out of said normal-width section of said other associated said cam groove, and wherein, when said retractable zoom lens is set at said transition state, both said front and rear cam followers are positioned out of said normal-width sections of said associated cam grooves so that at least one of said front and rear cam followers is loosely engaged in said wide-width section of said one associated cam groove.