Projection lens and projection type display device using the...

Details Projection lens and projection type display device using the... Projection lens and projection type display device using the...

2007-12-18

2007-12-18

Lester, Evelyn A. (Department: 2873)

Optical: systems and elements

Lens

With field curvature shaping

C359S649000, C359S716000, C359S740000, C359S784000

Reexamination Certificate

active

11783028

ABSTRACT:
A projection lens includes, in order from a magnification side, a first lens group, a second lens group and a third lens group. The first lens group includes, in order from the magnification side, a negative lens whose lens made of a non-resin, a plastic lens at least one surface of which is aspheric and a positive lens. The second lens group includes a plastic lens at least one surface of which is aspheric, a positive lens and a negative lens. The third lens group includes a positive lens. The following conditional expressions are satisfied;in-line-formulae description="In-line Formulae" end="lead"?1.0<Bf/f≦1.8in-line-formulae description="In-line Formulae" end="tail"?in-line-formulae description="In-line Formulae" end="lead"?2.0<f1/fin-line-formulae description="In-line Formulae" end="tail"?in-line-formulae description="In-line Formulae" end="lead"?2.0<f2/fin-line-formulae description="In-line Formulae" end="tail"?where Bf denotes a air-conversion back focus of the entire system, f denotes a focal length of the entire system, f1 denotes a focal length of the first lens group and f2 denotes a focal length of the second lens group.

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