| 摘要 |
PURPOSE: To provide an optical device which has at least two focal positions for specific focal length and adjusts the focus and focal length. CONSTITUTION: In a device equipped with 1st and 2nd lens groups 12 and 14 which are provided movably along the optical axis and a mechanism 48 consisting of a cam 50 and a follower 52 which vary the focal length of an optical system by displacing the 2nd lens group 14 relatively along the axis in response to the axial movement of the 1st lens group 12, the mechanism 48 is equipped with plural cam step, each of which has a 1st means for holding the relative displacement constant in response to the axial movement of the 1st lens group 12 and a 2nd means for varying the relative axial displacement in response to the axial movement of the 1st lens group 12. |
