Wide angle lens

Details Wide angle lens Wide angle lens

1996-03-13

1998-09-22

Nelms, David C.

Optical: systems and elements

Lens

Reverse telephoto

359651, 359742, 359748, 359750, 359751, 359752, 359753, 359663, 359679, G02B 900, G02B 1322

Patent

active

058123261

ABSTRACT:
A wide angle lens is made of three groups so as to satisfy a predetermined conditional expression concerning abbe number, thereby making it telecentric and yielding no eclipse in its peripheral luminous flux. Also, an apparatus accommodating it is made compact as a whole. This wide angle lens comprises, arranged in the following order from the screen side toward the liquid crystal side, a first lens group composed of a concave lens (L1), whose concave surface having a large radius of curvature is directed toward a smaller conjugate side (liquid crystal panel), and a convex lens (L2); a second lens group composed of one concave lens (L3) and two convex lenses (L4) and (L5); and a third lens group composed of a Fresnel lens (L6) which is disposed near a liquid crystal panel (L7; 4). The abbe number .nu. 1 of the lens L1 which is the concave lens in the first lens group is 57.8, whereas the abbe number .nu. 2 of the lens (L3) which is the concave lens in the second lens group is 25.4, thereby satisfying the conditional expression of .nu. 1>.nu. 2. The focal length f1 of the first lens group is 453.1 mm, whereas the focal length f0 of the whole lens group system is 67.76 mm, thereby satisfying .vertline.f1.vertline.>f0.

REFERENCES:
patent: 4936657 (1990-06-01), Tejima et al.
patent: 5390048 (1995-02-01), Miyatake et al.
Nikkei Sangyo Shimbun, Abstract, Oct. 18, 1994.

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