Patent ID: 9250427
Filing Date: 2016-02-02
CPC Classification: G02B

Claim Text:
1. A projection lens having a positive refractive power as a whole and comprising a correction group consisting of a plurality of lens groups that corrects field curvature by moving in an optical axis direction and changing the distance between each lens group, wherein: the conjugation length of a combined optical system combining the most magnification side lens group constituting the correction group to the most reduction side lens group constituting the correction group in the projection lens is constant before and after the movement of the correction group for correcting field curvature; and when the projection lens is variable in magnification or focusable by moving at least some of the lens groups, the movement of the correction group for correcting field curvature is allowed to be performed independently of the movement for either changing magnification or focusing, wherein a first lens group which has a negative refractive power and is different from the correction group is disposed on the most magnification side, and the lens groups constituting the correction group are adjacently disposed on the reduction side of the first lens group.