Optical: systems and elements – Lens – With field curvature shaping
Patent
1998-09-03
2000-09-26
Epps, Georgia
Optical: systems and elements
Lens
With field curvature shaping
359716, 359781, 359784, G02B 300, G02B 1318, G02B 934
Patent
active
061249793
ABSTRACT:
A projection lens device for extensively projecting an original image being displayed on an image source, such as a liquid crystal panel, upon a screen, comprising in sequence from the screen: a first lens group having a negative refractive power as an entire system thereof, and including at least a meniscus lens of negative refractive power, which has a convex surface toward the screen side; a second lens group having a positive refractive power as an entire system thereof, and including cemented lenses having a negative refractive power, one of which has convex surfaces at both sides and a first Abbe's number and the other of which has concave surfaces at both sides and a second Abbe's number being smaller than the first Abbe's number; and a third lens group having a negative refractive power as an entire system thereof, and including at least a lens which has a concave surface at a center thereof toward the screen.
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Hirata Koji
Mori Shigeru
Ogura Naoyuki
Otsuka Yasuo
Epps Georgia
Hitachi , Ltd.
Lester Evelyn A.
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