Zoom lens and image projection apparatus including the same

Details Zoom lens and image projection apparatus including the same Zoom lens and image projection apparatus including the same

2006-07-18

2006-07-18

Lester, Evelyn A. (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S681000, C359S682000, C359S683000, C359S684000, C359S686000, C359S689000, C359S691000, C359S713000, C359S714000, C359S715000, C359S716000, C359S717000, C359S737000, C359S749000, C359S761000, C359S770000, C359S781000

Reexamination Certificate

active

07079324

ABSTRACT:
A zoom lens includes a plurality of lens groups including a first lens group arranged on the foremost side and having negative optical power. Zooming is performed by moving at least one of the plurality of lens groups along a direction parallel to an optical axis of the zoom lens. The first lens group is fixed during the zooming. A first lens arranged on the foremost side, of the first lens group has negative refractive power. When an Abbe constant and a partial dispersion of a material configuring the first lens are respectively represented by νdn and θg,Fn, a focal distance of the first lens group is represented by f1, and an air-equivalent back focus upon focusing on an infinity object is represented by bf, the following conditions are satisfied:in-line-formulae description="In-line Formulae" end="lead"?νdn<32,in-line-formulae description="In-line Formulae" end="tail"?in-line-formulae description="In-line Formulae" end="lead"?0.008<θg,Fn−(0.644−0.00168×νdn)<0.040, andin-line-formulae description="In-line Formulae" end="tail"?in-line-formulae description="In-line Formulae" end="lead"?|f1/bf|<0.9.in-line-formulae description="In-line Formulae" end="tail"?

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