Fingerprint sensing device for deriving an electric signal
First Claim
1. A fingerprint sensor for deriving an electric output signal according to the ridges and valleys of a finger under investigation, said sensor comprising, in combination:
- (a) an elastic, pressure-sensitive contact surface formed by a transparent elastic material for receiving a contact pressure by said finger, thereby changing the structure of said surface in accordance with the fingerprint pattern of ridges and valleys of said finger, whereby the regions of the contact surface associated with the fingerprint valleys are not in contact with the finger and form small concave focusing mirrors, having their focal points along a focusing plane which is parallel to, and at the focal distance of said focusing mirrors away from, said contact surface;
(b) a light source for passing substantially parallel light through said transparent elastic material to said contact surface, whereby in the presence of said finger said regions of the contact surface associated with the valleys which form said focusing mirrors reflect the light impinging on these regions and focus this light at said focusing plane, thus forming a focused light pattern at said plane in accordance with the fingerprint pattern of said finger;
(c) photodetector means having a light sensitive area for measuring the distribution of light impinging on said area;
(d) optical means focused on said plane for transmitting said focused light pattern to said light sensitive area of said photodetector means; and
(e) output means associated with said photodetector means for deriving said electric output signal in response to the pattern of light falling on said light sensitive area.
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Accused Products
Abstract
The fingerprint sensor derives an electric output signal in accordance with the topographic relief of the finger under investigation. The sensor incorporates a contact body which is formed at least in part by a light-transparent elastic material. The contact body, preferably a flat sensor plate made of said elastic material and attached to a flat supporting plate, has a light receiving surface and a contact surface for receiving a contact pressure by the finger. Before an investigation process is started, the contact surface is smooth. By pressing the finger against the contact surface, the contact surface will attain a shape conforming to the fingerprint pattern of the finger. The sensor also incorporates a light source, a photodetector and an optical system. The light source obliquely passes light to the contact surface which reflects a light beam modulated in accordance with the fingerprint. The optical system passes the reflected light beam to the light sensitive area of the photodetector. In the optical path between finger and photodetector is included a light stop for blocking reflected light which does not contain fingerprint information.
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Citations
17 Claims
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1. A fingerprint sensor for deriving an electric output signal according to the ridges and valleys of a finger under investigation, said sensor comprising, in combination:
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(a) an elastic, pressure-sensitive contact surface formed by a transparent elastic material for receiving a contact pressure by said finger, thereby changing the structure of said surface in accordance with the fingerprint pattern of ridges and valleys of said finger, whereby the regions of the contact surface associated with the fingerprint valleys are not in contact with the finger and form small concave focusing mirrors, having their focal points along a focusing plane which is parallel to, and at the focal distance of said focusing mirrors away from, said contact surface; (b) a light source for passing substantially parallel light through said transparent elastic material to said contact surface, whereby in the presence of said finger said regions of the contact surface associated with the valleys which form said focusing mirrors reflect the light impinging on these regions and focus this light at said focusing plane, thus forming a focused light pattern at said plane in accordance with the fingerprint pattern of said finger; (c) photodetector means having a light sensitive area for measuring the distribution of light impinging on said area; (d) optical means focused on said plane for transmitting said focused light pattern to said light sensitive area of said photodetector means; and (e) output means associated with said photodetector means for deriving said electric output signal in response to the pattern of light falling on said light sensitive area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification