Optical: systems and elements – Lens – With field curvature shaping
Patent
1998-02-17
2000-05-09
Mack, Ricky
Optical: systems and elements
Lens
With field curvature shaping
G02B 300
Patent
active
060611855
ABSTRACT:
Four groups of six lenses comprising a plastic lens having weak refracting power, three glass lenses of convex, concave, and convex yielding a major part a refracting power of the projection lens as a whole, a plastic lens having a weak refracting power, and a lens having a concave surface directed onto the screen side are successively disposed from the screen side, whereby the plastic lens with a temperature-correcting function is omitted, thus cutting down cost. Successively disposed from the screen side are G.sub.1 made of a plastic lens L.sub.1 having a weak refracting power and at least one aspheric surface, G.sub.2 made of three glass lenses of convex, concave, and convex L.sub.2 to L.sub.4 yielding a major part of the refracting power of the projection lens as a whole, G.sub.3 made of a plastic lens L.sub.5 having a weak refracting power and at least one aspheric surface, and G.sub.4 made of a lens L.sub.6 having at least one aspheric surface and a concave surface directed onto the screen side.
REFERENCES:
patent: 4989961 (1991-02-01), Yoshioka
patent: 5272540 (1993-12-01), Hirata et al.
patent: 5367405 (1994-11-01), Sado
patent: 5572364 (1996-11-01), Toide et al.
patent: 5659424 (1997-08-01), Osawa et al.
Fuji Photo Optical Co., Ltd.
Mack Ricky
Snider Ronald R.
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