Projection lenses having large back focal length to focal length

Details Projection lenses having large back focal length to focal length Projection lenses having large back focal length to focal length

1999-02-08

1999-10-19

Epps, Georgia

Optical: systems and elements

Lens

With field curvature shaping

359649, 359682, 359689, 359716, 359784, G02B 300, G02B 912, G02B 1514

Patent

active

059698764

ABSTRACT:
A projection lens for use with LCD or DMD panels is provided. The lens has three lens units, the first unit having a negative power and at least one plastic lens element having two aspheric surfaces, a second lens unit having a negative power or a weak positive power and at least one color correcting doublet, and a third lens unit having a positive power and an aspheric surface either on a glass element or on a weak plastic element. The projection lens has a back focal length to focal length ratio of at least 3.0, the ratio being achieved by arranging the first, second, and third lens units so that:

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Patent Abstracts of Japan, vol. 095, No. 009, Oct. 1995: JP 07 140379 (Asahi Optical Co. Ltd.) Jun. 2, 1995, abstract.
Translation of Patent Publication No. 6-317742 (Japan, Nov. 1994), Item 35 above.

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