| 摘要 |
A lens-barrel cam mechanism includes first and second ring members; and cam grooves and cam followers formed on the first and second ring members. A single groove/follower set, including one cam groove and one cam follower, and a groove/follower group, including front and rear groove/follower sets at different positions in the optical axis direction, are at different positions single groove/follower set intersects those of the groove/follower group, and condition (a) and/or (b) are satisfied: (a) the cam groove of the single groove/follower set is wider than that of the groove/follower group, and (b) an interval between the cam groove of the single groove/follower set and that of the front groove/follower set and an interval between the cam groove of the single groove/follower set and that of the rear groove/follower set in the circumferential direction are different.
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