Birch, Stewart, Kolasch & Birch, LLP
Projection lens and projection type display device using the same
A projection lens includes, in order from a magnification side, a first lens group, a second lens group and a third lens group. The first lens group includes, in order from the magnification side, a negative lens whose lens made of a non-resin, a plastic lens at least one surface of which is aspheric and a positive lens. The second lens group includes a plastic lens at least one surface of which is aspheric, a positive lens and a negative lens. The third lens group includes a positive lens. The following conditional expressions are satisfied;1.0<Bf/f≦1.82.0<f1/f 2.0<f2/f where Bf denotes a air-conversion back focus of the entire system, f denotes a focal length of the entire system, f1 denotes a focal length of the first lens group and f2 denotes a focal length of the second lens group.
Fujinon Corporation
G
G02B
inventional
Chikara Hiroshi
Yamamoto Yamada