Patent ID: 9740086
Date: 2017-08-22
CPC Classifications: G02B,G03B

Claim:
1. A projection system comprising a first lens group to an n-th lens group with n being 6 or 7 sequentially arranged from an enlargement side, wherein the first lens group includes a first-first lens group and a first-second lens group sequentially arranged from the enlargement side, the first-first lens group and the first-second lens group are separated from each other by a variable distance for image plane correction, the first lens group and the n-th lens group are fixed and the second lens group to an (n−1)-th group are moved when magnification is changed, and the following conditional expression is satisfied: where fw represents a focal length of the projection system operating at a wide angle end, and BF represents an air conversion length of a back focal distance of the projection system.