| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To enable an appropriate back focus and a high variable magnification ratio, suppressing aberration variation when varying magnification, preventing upsizing of a whole system, widening a view angle, keeping an F number constant when varying magnification, and being telecentric on a contraction side all together in a variable magnification optical system for projection. <P>SOLUTION: A variable magnification optical system for projection of the invention comprises a first negative lens group G1 placed closest to a magnification side and being immovable when varying magnification, a final positive lens group placed closest to a contraction side and being immovable when varying magnification, and plural lens groups placed between the first lens group G1 and the final lens group and being moved when varying magnification. The system is telecentric on the contraction side. A diaphragm is disposed in the final lens group, and a numerical aperture is set to be constant over an entire range of magnification variation. Also a conditional expression is satisfied relating to an overall thickness of the lenses L, a maximum effective image circle diameter on the contraction side Imϕ, a back focus (in air) of the whole system on the contraction side at a wide angle end Bf, a variable magnification ratio of a telephoto end to the wide angle end Zr, and a focal distance of the whole system at the wide angle end f. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
