Wide-angle projection lens

Details Wide-angle projection lens Wide-angle projection lens

2006-02-14

2006-02-14

Thompson, Timothy (Department: 2873)

Optical: systems and elements

Lens

Multiple component lenses

C359S717000, C359S691000

Reexamination Certificate

active

06999247

ABSTRACT:
A wide-angle projection lens includes, in order from an object side: a first lens group including four lenses and having a negative refractive power; and a second lens group including a cemented lens and having a positive refractive power. The first lens group includes an aspherical lens and a spherical lens having a positive refractive power. The wide-angle projection lens further includes an iris diaphragm located after the first lens of the second lens group from the object side, and satisfies the following conditional expressions fb/f>3, −2.0<D12/f1<−1.3, and 0.8<Lr/Lf<1.2 where f denotes the focal length of the projection lens; fb denotes the retrofocal length of the projection lens; f1denotes the focal length of the first lens group; Lf denotes the thickness of the first lens group; Lr denotes the thickness of the second lens group; and D12denotes the distance between the first and second lens groups.

REFERENCES:
patent: 4364641 (1982-12-01), Mogami
patent: 5644435 (1997-07-01), Shikama
patent: 5973848 (1999-10-01), Taguchi et al.
patent: 05-203871 (1993-08-01), None
patent: 07-311338 (1995-11-01), None
patent: 2003-15033 (2003-01-01), None
patent: 2003-35870 (2003-02-01), None
patent: 2003-156683 (2003-05-01), None

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