Patent ID: 9285574
Filing Date: 2016-03-15
CPC Classification: G02B,G03B

Claim Text:
1. A variable magnification projection optical system comprising: in order from a magnification conjugate side to a reduction conjugate side, a first lens group having a totally negative refracting power and being stationary during changing of magnification; a second lens group having a totally positive refracting power and being movable during changing of magnification; a third lens group having a totally positive refracting power and being movable during changing of magnification; a fourth lens group having a totally negative refracting power and being stationary or movable during changing of magnification; a fifth lens group having a totally positive refracting power and being movable during changing of magnification; a sixth lens group having a totally positive refracting power and being stationary during changing of magnification; and an optical stop which is arranged at any position from a front of a lens arranged closest to the magnification conjugate side in the fourth lens group to a front of a lens arranged closest to the magnification conjugate side in the fifth lens group, wherein the fourth lens group is configured to include, in order from the magnification conjugate side, two or more negative lenses and a positive lens, and wherein the following condition expressions (1), (2) and (3) are satisfied: wherein, E E f f φ φ