Patent ID: 7212352

Claim:
A cam mechanism of a lens barrel, comprising: a first ring member rotatable about an optical axis; a second ring member which supports an optical element, and is linearly guided along said optical axis without rotating; a plurality of cam grooves having the same reference cam diagrams which are formed on one of said first ring member and said second ring member; and a plurality of cam followers formed on the other of said first ring member and said second ring member to be engaged in said plurality of cam grooves, respectively, wherein said plurality of cam grooves and said plurality of cam followers include a single groove/follower set, which includes a cam groove and an associated cam follower, and at least one groove/follower group, each of which includes a front groove/follower set and and a rear groove/follower set which are positioned at different positions in said optical axis direction, said single groove/follower set and said groove/follower group being positioned at different positions in a circumferential direction, wherein said cam groove of said single groove/follower set intersects said cam grooves of said groove/follower group, and wherein at least one of the following two conditions (a) and (b) is satisfied: (a) said cam groove of said single groove/follower set is greater in width than each of said cam grooves of said groove/follower group, and (b) an interval between said cam groove of said single groove/follower set and said cam groove of said front groove/follower set in said circumferential direction and an interval between said cam groove of said single groove/follower set and said cam groove of said rear groove/follower set in said circumferential direction are mutually different.