Fingerprint image refinement

• US 4,569,080 A
• Filed: 06/23/1983
• Issued: 02/04/1986
• Est. Priority Date: 07/09/1982
• Status: Expired due to Fees

• Current Assignee: Secure Technologies Group, Inc.
• Original Assignee: Secure Technologies Group, Inc.
• Inventors: Schiller, Michael
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US06/507,067
• Time in Patent Office: 957 Days
• Field of Search: 382/2, 382/4, 382/5, 356/71, 350/485
• US Class Current: 382/126
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G06V 40/13 Sensors therefor

Abstract

In an optical fingerprint image processing apparatus a light beam is scanned across a finger placed against a transparent platen in order to provide a reflected modulated light beam carrying fingerprint information. The modulated light beam is imaged and the image is intercepted by an array of photo receptors that detect the image and convert the optical signal into electrical signals. The improvement is in placing a diffuser element, which may be a ground glass wafer, in the interrogating light beam. The diffusion of the light beam acts as an effective filter to eliminate the higher spatial frequency components of the optical image and thus provide a fingerprint image having improved continuity.

Claims

1. In an optical fingerprint image processing apparatus wherein a fingerprint object on a platen is optically scanned by an interrogating light beam to provide a reflected light beam modulated with the fingerprint information and wherein the modulated light beam is imaged by an imaging lens and an array of photo detectors is positioned downstream from the lens to receive and detect the image formed, the improvement comprising:

a diffuser element positioned within the interrogating light beam to partially diffuse said beam and to provide an interrogating light beam at the fingerprint object which is sufficiently diffused to eliminate the higher spatial frequency components of the reflected image;

whereby over-modulation components of the reflected image are avoided.

2. The improvement of claim 1, wherein said platen has a transparent substrate and a deformable resilient layer on the finger receiving surface thereof, said layer being responsive to an applied finger to provide the fingerprint object, said deformable layer including a reflective layer to provide the fingerprint object as a reflective object.

3. The improvement of claim 2, wherein said diffuser element has a diffusing surface with a grain size approximately ten micrometers in diameter.

4. The improvement of claim 1, wherein said platen has a transparent substrate and an anti-reflective coating on the finger receiving surface thereof.

5. The improvement of claim 4, wherein said diffuser element has a diffusing surface with a grain size approximately ten micrometers in diameter.

6. The improvement of claim 1, wherein said diffuser element has a diffusing surface with a grain size approximately ten micrometers in diameter.

7. In the method of optically processing a fingerprint image in which a fingerprint object is optically scanned by an interrogating light beam to provide a reflected light beam modulated with the fingerprint information and wherein the modulated light beam is imaged by an imaging lens and an array of photodetectors is positioned downstream from the lens to receive and detect the image formed, the improvement comprising the step of:

partially diffusing the interrogating light beam, the partial diffusion being sufficient to eliminate the higher spatial frequency components of the fingerprint image carried by the reflected light beam,

whereby over-modulation components of the reflected image are avoided.

8. The method fo claim 7, wherein said step of diffusing is insufficient to substantially degrade the interrogating light beam.

9. The method of claim 7, wherein the fingerprint object is formed from a finger placed against a platen and wherein the interrogating light beam is modulated by differential scattering of the light reflected respectively from beneath the valley and ridge zones.

10. The method of claim 7, wherein the fingerprint object is formed from a finger placed against a platen having an anti-reflective coating on the finger receiving surface thereof.