Finger identification

• US 4,322,163 A
• Filed: 11/17/1980
• Issued: 03/30/1982
• Est. Priority Date: 10/25/1977
• Status: Expired due to Term

• Current Assignee: Secure Technologies Group, Inc.
• Original Assignee: Secure Technologies Group, Inc.
• Inventors: Schiller, Michael
• Primary Examiner(s): Punter, William H.
• Application Number:
  US06/207,639
• Time in Patent Office: 498 Days
• Field of Search: 356/71, 356/371, 356/394, 356/446, 356/448, 350/146.3 E, 250/566
• US Class Current: 356/71
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence
• CPC Class Codes: G06V 40/1335 Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement

Abstract

A finger pressed against a platen provides a fingerprint object which is scanned by an interrogating beam of collimated light in the form of a slit and that is linearly displaced across the platen. As the slit-beam scans across the back surface of the platen, the reflected light beam is modulated. The modulated beam is imaged onto a linear array of photodiodes to provide a series of output signals indicative of modulation information. The outputs of the diodes are serially interrogated at each of successive scan positions to provide a set of signals containing fingerprint information. The platen has a transparent glass base. A layer of transparent, compressible, resilient epoxy is on the back of the glass base. The epoxy layer has a flat back surface. A thin silver reflecting layer on the back surface of the epoxy provides a flat mirrored surface to reflect the light beam. A further epoxy layer on top of the silver provides mechanical filtering. A lacquer layer at the back protects the platen from wear. When a finger is applied to the back surface, the ridges of the finger distort the underlying layers sufficiently so that the reflected light at the ridge zones is scattered while the reflected light at the valley zones is collimated. This difference in scatter is transformed by an imaging lens to a difference in intensity at the diode array.

Claims

1. In an optical finger image processing apparatus, the improvement comprising:

a platen having a front surface adapted to receive an interrogating light beam and a back surface adapted to receive a finger thereon, said platen having a transparent substrate, a first deformable, resilient transparent layer on the back surface of said substrate, said layer having sufficient thickness and being sufficiently deformable so that forces transmitted by the ridges of a finger pressed against the back surface on said platen will readily cause said layer to deform in the zones directly under the ridges of the applied finger, and a reflective layer on the back surface of said first deformable, resilient layer, said reflective layer being sufficiently thin so that forces transmitted by the ridges of a finger pressed against the back surface of said platen will be readily transmitted to said deformable resilient layer.

2. The improvement of claim 1 wherein said substrate is glass and said first deformable layer is epoxy.

3. The improvement of claim 2 wherein said epoxy layer has a thickness of approximately 0.25 millimeters.

4. The improvement of claims 1, 2 or 3 wherein said reflective layer is a metallic deposit approximately 3,000 Angstroms thick.

5. The improvement of claims 1, 2 or 3 further comprising:

a compliant protective layer defining the back surface of said platen.

6. The improvement of claim 4 further comprising:

a compliant protective layer defining the back surface of said platen.

7. The improvement of claims 1 or 2 further comprising:

a second deformable, resilient layer on the back surface of said reflective layer to provide a predetermined separation between said reflective layer and the finger receiving surface of said platen.

8. The improvement of claim 7 wherein said second deformable layer has deformation and resilience characteristics comparable to that of said first deformable resilient layer.

9. The improvement of claim 7 further comprising:

a compliant protective layer defining the back surface of said platen.

10. The improvement of claim 8 further comprising:

a compliant protective layer defining the back surface of said platen.

11. In an optical finger image processing apparatus, the improvement comprising:

a platen having a front surface adapted to receive an interrogating light beam and a back surface adapted to receive a finger thereon, said platen having a relatively hard transparent substrate, an optically active surface and a touching surface, said optically active surface being effective to reflect substantially all of the incident light received thereon from the interrogating light beam, said platen having a first deformable resilient layer between said substrate and said optically active surface, said first layer being transparent, said platen also having a second deformable resilient layer between said optically active surface and said touching surface, said second layer serving to transmit the three dimensional finger image from said touching surface to said optically active surface, said first layer serving to permit said optically active surface to provide the three dimensional finger image being transmitted.

12. The improvement of claim 11 wherein the deformation and resilience characteristic of said first and second layers are substantially the same.