Fingerprint sensing system using a sheet prism
First Claim
1. A fingerprint sensing system comprising:
- a sheet prism havinga 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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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.
214 Citations
28 Claims
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1. A fingerprint sensing system comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A fingerprint sensing system comprising:
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a sensing surface, a transparent substrate; a plurality of rigid prismlets coupled to the transparent substrate, the prismlets positioned opposite to the sensing surface and forming a first sheet prism; a detector array; a lens to focus the radiation emitted from the exit surfaces to the detector array, and to de-magnify the image to be captured by the detector array; an optical system with mirrors to fold the emitted radiation so as to change the ratio between the maximum length and maximum width of the sensing system and mirrors on both the top and the bottom surfaces to reflect the emitted radiation; wherein use of the sheet prism and the mirrors in the optical system substantially reduce a height of the finger print system.
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Specification