Zoom projection lenses for use with pixelized panels
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United States of America Patent
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-
May 4, 1999
Grant Date -
N/A
app pub date -
Feb 12, 1998
filing date -
Feb 13, 1997
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A zoom projection lens for use with LCD or DMD panels is provided. The lens has two units U1 and U2, which are moved relative to one another for zooming. The first unit has a negative power and includes at least three lens elements L1, L2, and L3, where L1 is composed of plastic and has two aspherical surfaces, L2 has a positive power and is composed of a flint material, and L3 has a negative power and is composed of a crown material. The second unit has two subunits U2.sub.S1 and U2.sub.S2, each of which has a positive power, with the power of U2.sub.S2 being greater than the power of U2.sub.S1. At its minimum effective focal length f.sub.min, the projection lens has a back focal length to focal length ratio greater than one, the ratio being achieved by arranging the first unit, the second unit, and the subunits of the second unit so that: D.sub.12 /f.sub.min >1.0, D.sub.S1S2 /f.sub.min >1.0, and D.sub.12 /D.sub.S1S2 >1.0, where D.sub.12 is the axial distance between the first and second lens units evaluated at f.sub.min and D.sub.S1S2 is the axial distance between the first and second subunits of the second lens unit.
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Cited Art Landscape
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