VARIABLE MAGNIFICATION OPTICAL SYSTEM FOR PROJECTION, AND PROJECTION DISPLAY DEVICE

WIPO Patent Application WO/2013/001759

A1

[Problem] To provide a variable magnification optical system for projection having a reduction side that is telecentric, a long back focus, and a high variable magnification ratio, and in which a wide angle is easy to achieve and upsizing can be suppressed even in the wide-angle state, thus allowing the obtention of a satisfactory projected image. [Solution] A variable magnification optical system for projection comprises: a first negative lens group (G1) that is disposed closest to the magnification side and fixed during magnification variation; a positive final lens group that is disposed closest to the reduction side and fixed during magnification variation; and a plurality of lens groups that is disposed between the first lens group (G1) and the final lens group, and moves during magnification variation. The plurality of lens groups which move during magnification variation comprises three or more lens groups. Among the plurality of lens groups, the lens group closest to the magnification side is a negative lens group. The reduction side is telecentric. The back focus (Bf) of the reduction side of the entire system at the wide-angle end (air-equivalent distance), the focal distance (fw) of the entire system at the wide-angle end, and the focal distance (fe) of the final lens group satisfy the conditional expressions (1): [1.5