Projection lens and projection display apparatus

Details Projection lens and projection display apparatus Projection lens and projection display apparatus

1995-12-07

1998-08-18

Dowling, William

Optics: image projectors

Prism in light path

353 34, 359650, G03B 2114

Patent

active

057950474

ABSTRACT:
A projection lens includes sequentially from a screen side a first lens group which has a negative power, a second lens group which has a weaker power than that of the first lens group, a third lens group which has a positive power, a fourth lens group which has a positive power, and at least one transparent prism, wherein the fourth lens group is placed on the third lens group side of the transparent prism so as to be close to or in contact with the transparent prism. In the projection lens, a back focus of the main lens group is much longer compared with a focal length. A projection display apparatus using this projection lens is composed of one main lens group, three auxiliary lenses, and three polarizer-beam splitters, and a color combining optical system for combining three primary color components of red, green, and blue into one light beam is placed between the main lens group and the auxiliary lens.

REFERENCES:
patent: 4191456 (1980-03-01), Hong et al.
patent: 5218480 (1993-06-01), Moskovich
patent: 5390048 (1995-02-01), Miyatake et al.
patent: 5400093 (1995-03-01), Timmers
patent: 5404175 (1995-04-01), Nagae et al.
patent: 5597222 (1997-01-01), Doany et al.

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