| 摘要 |
PURPOSE:To stop down a lens properly and continuously over the entire picture plane by providing >=1 hollow cylindrical aperture member which moves forth and back in the direction of optical axis between a reflection and a refraction system, and cutting off the edge part of reflected luminous flux by the forward-backward movement of the aperture member. CONSTITUTION:An external aperture member 20 and an internal aperture member 22 are supported between the projection part 28 of a main lens barrel 24 and the annular part 40 of an aperture driving ring 38. A pin 42 implanted in the outer circumferential flank of the member 20 transmits the motion of the ring 38 to the member 20, and a pin 44 implanted in the outer circumferential flank of the member 22 transmits the motion of the ring 38 to the member 22. When an aperture ring 38 is rotated by the rotary motion of an aperture ring 26, the pin 42 engages with a groove 46 and the pin 44 engages with a groove 48 to rotate the members 20 and 22 respectively, but a fixed pin 34 engages with a slanting groove 54 and a fixed pin 32 engages with a slanting groove 50 to put the members 20 and 22 in simultaneous forward/backward motion. The member 20 cuts off the edge of luminous flux positioned outside of it and the member 22 cuts off the edge of luminous flux positioned inside of it; and the members 20 and 22 serve for a continuous stopping-down function at their tip parts. |
