Retro-focus lens

Details Retro-focus lens Retro-focus lens

1999-03-16

2000-12-12

Epps, Georgia

Optical: systems and elements

Lens

Reverse telephoto

359751, 359753, 359708, 359649, 359651, G02B 1304, G02B 302, G02B 300

Patent

active

061606715

ABSTRACT:
A retro focus lens having three lens groups arranged, in order from the longer conjugate length side of the lens, as follows: a negative first lens group G.sub.1, a positive second lens group G.sub.2, and a positive third lens group G.sub.3. The first group G.sub.1 includes, in order from the longer conjugate length side of the lens, a first lens element L.sub.1 of small positive refractive power and made of plastic with an aspherical surface, a second lens element L.sub.2 of negative refractive power that is made of glass and has a concave surface facing the shorter conjugate length side of the lens, and a third lens element L.sub.3 of negative refractive power with a concave surface facing the shorter conjugate length side of the lens, there being no additional lens elements between the first lens element L.sub.1 and the third lens element L.sub.3. By satisfying preferred conditions, favorable chromatic aberrations and distortion are attained while achieving a high resolution and a sufficiently large back focus to allow the lens to be used as a projection lens for liquid crystal color projectors.

REFERENCES:
patent: 5812326 (1998-09-01), Yamada
patent: 5949589 (1999-09-01), Nakazawa

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