VARIABLE MAGNIFICATION OPTICAL SYSTEM FOR PROJECTION AND PROJECTION TYPE DISPLAY DEVICE

摘要

[Problem] To provide a variable magnification optical system for projection wherein the reduction side is made telecentric and, while suppressing increases in size of the system as a whole, long depth of field and high magnification ratios are ensured, forming wide-angle images is easy, and excellent projection images are obtained. [Solution] This variable magnification optical system for projection comprises a negative first lens group (G1) that is disposed furthest to the magnification side and stationary when magnification is varied, a positive final lens group that is disposed furthest to the reduction side and stationary when magnification is varied, and a plurality of lens groups that are disposed between the first lens group (G1) and a final lens group and move when magnification is varied. A lens group (second lens group (G2)) furthest to the magnification side of the plurality of lens groups that move when magnification is varied has negative refractive power. The reduction side is made telecentric. Conditions (1) and (2) are satisfied. 1.5 < Bf/fw (1) -13.0 < f2/fw < -1.5 (2) Wherein: Bf: Depth of field of reduction side of system as a whole on the wide angle end (distance in air conversion) fw: Focal length for system as a whole at wide-angle end. f2: Focal length for second lens group (G2)