| 摘要 |
PURPOSE:To obtain excellent focusing performance and change magnification factor with simple structure by providing an optical member which exchanges optical path so that the optical path distance between an intermediate focal point and lens, and distance between lens and projected focal point. CONSTITUTION:A picture of alignment pattern 18 is focused to an intermediate picture 19 with an objective lens 15 and moreover is projected to the pick-up surface within a TV camera 17 with a lens 16. In this case, the magnification factor of final picture 20 is expressed by L1/L2. Here, the position of lens 16 is moved to the position 16' without changing the position of intermediate picture 19 and the position of the final picture. The lens position 16' is located at the area where the distance L2 from the intermediate picture and the distance L1 from the pick-up surface are inversed each other in comparison with the lens position 16. Thereby, the intermediate picture 19 is focused as indicated by an imaginary line 20' and is reduced in size with a factor of L2/L1. As mentioned above, a magnification factor can be changed in the 22 steps even when a lens having fixed magnification factor is used. |
