| 摘要 |
<p>PROBLEM TO BE SOLVED: To solve the problem that since it is difficult for a conventional zoom mechanism using a cam and a roller to process a conventional cam groove and a straight advance groove to the same size with a width which is exactly equal to the diameter of the roll, a tolerance is therefore set so as to suppress variance in size within an assumption range, but an optical system which has high optical sensitivity has its optical performance affected by rattling.SOLUTION: (1) A roller has an outer shape formed by combining together a circular roller having a circular outer shape and a roller in a long circle shape which are used as a driven member for a lead groove or cam groove, and the roller is fixed while decreasing the angle of a long circle part by rotation to the width of the cam groove to an extent that there is no influence of rattling on performance. (2) An outer peripheral shape of the long circle part of the roller is a polygonal shape obtained by approximating a long circle with a straight line. (3) The outer peripheral shape of the long circle part of the roller comprises a plurality of long circle shapes and a part in contact with a straight advance groove is a circumferential contact.</p> |
