Patent ID: 8830591
Filing Date: 2014-09-09
Classification: G02B

Abstract:
1. A projection lens for projecting image information displayed on a reduction side conjugate position to a magnification side conjugate position, the projection lens comprising: a first lens group having a negative power, a second lens group having a positive power, a third lens group having a positive power, and a fourth lens group having a positive power arranged in this order from the magnification side, wherein the projection lens satisfies conditional expressions (1), (2-1), (3), and (5) given below: where: Bf is a back focus on the reduction side (air equivalent length); f is a focal length of the entire projection lens, including said first, second, third, and fourth lens groups; d34 is an air equivalent distance on the optical axis between the third lens group and fourth lens group; YI is a maximum height of effective luminous flux at the reduction side conjugate position; YP is a maximum height of an off-axis principal ray in the projection lens; and YA is a maximum height of axial luminous flux in the projection lens; wherein said projection lens comprises a total of six or fewer lenses.