The prior art for contact image sensors is exemplified by U.S. Pat. No. 5,214,273 ("the '273 patent") which issued May 25, 1993 for an invention called "Contact Image Sensor." A second example of prior art is U.S. Pat. No. 5,331,146 ("the '146 patent") which issued Jul. 19, 1994 for an invention called "Contact-type Image Sensor for Generating Electric Signals Corresponding to an Image Formed on a Document." Unlike the present invention, the '273 patent and the '146 patent do not employ frustrated total internal reflection (FTIR) to view a high contrast fingerprint.
The prior art for fingerprint sensors is exemplified by U.S. Pat. No. 4,784,484 ("the '484 patent") which issued Dec. 4, 1986 for an invention called "Method and Apparatus for Automatic Scanning of Fingerprints." Unlike the present invention, the '484 patent uses a separate sensing means to measure the speed of finger motion. Also, unlike the present invention, the '484 patent does not teach the use of FTIR to view a high contrast image of the fingerprint. Finally, unlike the present invention, the '484 patent does not employ a gradient index rod lens array or an array of relay lens pairs.
The prior art for fingerprint sensors is also exemplified by U.S. Pat. No. 5,619,586 ("the '586 patent") which issued May 3, 1995 for an invention called "Method and Apparatus for Producing a Directly Viewable Image of a Fingerprint." The '586 patent shows prior art employing FTIR to obtain a high contrast fingerprint image. However, unlike the present invention, the '586 patent shows imaging of the entire fingerprint at once as an area image, instead of a narrow strip image projected onto a linear array sensor. Also, unlike the present invention, the '586 patent does not show the use of gradient index rod lenses or relay lenses to image the fingerprint.
The prior art for fingerprint sensors is also exemplified by U.S. Pat. No. 5,096,290 ("the '290 patent") which issued Mar. 17, 1990 for an "Apparatus for Imaging Fingerprint Using Transparent Optical Means Having Elastic Material Layer." Unlike the present invention, the '200 patent covers an elastic layer for the entire area of the fingerprint, rather than a narrow strip of the fingerprint.