| 摘要 |
PROBLEM TO BE SOLVED: To solve the following problem: in the conventional cam mechanism for a lens barrel, when increasing the length of a cam ring in the rotary axis direction, the size of the lens barrel is increased, on the contrary, when decreasing the size of the lens barrel, the length of the cam ring in the rotary axis is decreased, and it is impossible to achieve higher variable power of an optical system. SOLUTION: A cam mechanism has a cam ring 15 to the circumferential surface of which an external cam groove 65 is provided. By turning the cam ring 15, a cam pin is guided along the external cam groove 65, thereby moving the cam ring 15 forward/backward in the direction of an optical axis. At least part of one end of the cam ring 15 in the rotary axis direction is provided with a gear portion 60 which is extended to the outside in a radial direction and has teeth on its outer periphery. The end of the external cam groove 65 at the side of the gear portion is opened to the end face of the cam ring 15 to provide a cam groove opening 71. The cam groove opening 71 and gear portion 60 are disposed so as to be substantially coincident with each other on the identical vertical plane perpendicular to the optical axis direction. COPYRIGHT: (C)2011,JPO&INPIT
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