Projection lenses having larger back focal length to focal lengt

Details Projection lenses having larger back focal length to focal lengt Projection lenses having larger back focal length to focal lengt

1997-05-16

1999-02-09

Epps, Georgia

Optical: systems and elements

Lens

With field curvature shaping

G02B 300

Patent

active

058702288

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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Translation of Patent Publication No. 6-317742 (Japan, Nov. 1994), Item 19 above.

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