Apparatus and method for electronically acquiring
December 18, 2003 6:36pm
U.S. Patents
Patent Number 6665427
Issue Date 2003 12 16
Assignee Identix, Inc.
Inventor(s) Keagy, John M.
Pinkhasik, Naum
Muzil, Alexander
State/Country CA
Title Apparatus and method for electronically acquiring
fingerprint image with low cost removable platen and
separate imaging device
Abstract In one embodiment, a fingerprint sensing system includes a
sheet prism having a sensing surface and a number of
prismlets positioned opposite to the sensing surface. Each
prismlet has an entrance surface and an exit surface, and is
adjacent to another prismlet. The width of the sheet is more
than ten times the maximum thickness of any one of the
prismlets. When a finger is positioned on the sensing
surface, a portion of the radiation entering a number of the
entrance surfaces and incident at the sensing surface is
reflected through total internal reflection. The reflected
radiation emits from a number of the exit surfaces to create
an image of the fingerprint. In another embodiment, the
system further includes a second sheet prism stacked
together with the previously described sheet prism. The
second sheet prism has a flat surface and a number of
prismlets positioned opposite to the flat surface, which
faces the prismlets of the previously described sheet prism.
The image formed with two sheet prisms can have lower
distortion. In yet another embodiment, the fingerprint
sensing system is incorporated into a flat-profile package
using mirrors to fold radiation and to compress the height
of the package.
Exmp. Claim 1
Ex Claim text A fingerprint sensing system comprising:
a sheet prism having
a sensing surface,
a plurality of rigid prismlets positioned opposite to the
sensing surface,
each prismlet having an entrance surface and an exit
surface,
each prismlet being adjacent to another prismlet,
the width of the sheet being more than ten times the maximum
thickness of any one of the prismlets;
such that when a finger is positioned on the sensing
surface, a portion of illumination radiation illuminating
the system, entering a plurality of the entrance surfaces
and incident at the sensing surface is reflected through
total internal reflection and emitted from a plurality of
the exit surfaces to create an image of the fingerprint.
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