Patent ID: 9575297
Date: 2017-02-21
CPC Classifications: G02B

Claim:
1. A projection lens comprising a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having negative refractive power, a fifth lens group having positive refractive power, and a sixth lens group having positive refractive power, in sequence from an enlargement conjugate side, the projection lens performing magnification by changing the spacing between the lens groups, wherein at the time of magnification from the telephoto end to the wide-angle end, the second, third, fourth, and fifth lens groups are moved, an aperture stop is arranged between the surface of the third lens group closest to a reduction conjugate side and the surface of the fifth lens group closest to the enlargement conjugate side, and the following conditional expressions (1) and (2) are satisfied: where bf: Air-converted back focus from the rearmost lens surface to an image plane, fw: Focal length of the entire projection lens at the wide-angle end, dx: Amount of movement of the second lens group at the time of magnification from the telephoto end to the wide-angle end, and f2: Focal length of the second lens group.