Optical: systems and elements – Lens – Including a nonspherical surface
Patent
1997-05-09
1999-05-04
Epps, Georgia Y.
Optical: systems and elements
Lens
Including a nonspherical surface
356 71, G02B 1318
Patent
active
059009934
ABSTRACT:
Lens systems for use in fingerprint detection systems employing frustrated total internal reflection are provided. The systems include an aperture stop and three lens units. The first lens unit has a positive power, is located on the object side of the aperture stop, and forms a telecentric pupil for the lens system. The second lens unit has a positive power, is located on the image side of the first lens unit, and forms a real image of the object. In certain embodiments, the third lens unit is located between the first and second lens units and has substantially afocal cylindrical power. In other embodiments, the third lens unit serves to correct the field curvature of the image contributed by the first and second lens units.
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Cross Check Corporation
Epps Georgia Y.
Klee Maurice M.
Lucas Michael A.
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