Cam mechanism of a telescoping lens barrel

A cam mechanism of a lens barrel, comprising:

• a cam ring;
• and
• a movable frame which moves along an optical axis of an optical system when said cam ring is rotated by engagement of at least one cam groove comprising two cam groove segments, provided on said cam ring with at least one corresponding cam follower provided on said movable frame, said movable frame supporting at least one optical element of said optical system,
• wherein said cam groove is formed as a bottomed cam groove including two inclined side surfaces and a bottom surface which connects said two inclined side surfaces to each other, a width of said cam groove decreasing in a depth direction in a cross section orthogonal to a direction of a reference cam diagram of each said cam groove,
• wherein:
• said cam groove comprises at least one single-sided cam section, which is formed by removing a section of one of said two included side surfaces which is positioned closer to a nearby end of said cam ring, and
• one of said two cam groove segments extends from a first end of said single-sided cam section, and the other of said two cam groove segments extends from a second end of said single-sided cam section, such that said single-sided cam section and said two cam groove segments maintain continuity of said reference cam diagram of said cam groove.