Patent ID: 9261687
Filing Date: 2016-02-16
CPC Classification: G02B

Claim Text:
1. A variable magnification optical system for projection consisting of: a negative lens group having negative refractive power; and a positive lens group having positive refractive power in this order from a magnification side, wherein a distance on an optical axis between the negative lens group and the positive lens group changes during magnification change, and wherein an entire system substantially consists of six lenses, and wherein the negative lens group consists of a first lens including an aspheric surface and a second lens that is a single lens having negative refractive power in this order from the magnification side, and wherein the first lens is made of plastic material, and wherein the following conditional expression (1) is satisfied: fw: a focal length of the entire system at a wide angle end, and f1: a focal length of the first lens.