Elliptical finger press scanner with rotating light source

• US 4,684,802 A
• Filed: 02/18/1986
• Issued: 08/04/1987
• Est. Priority Date: 02/18/1986
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Walker, James R., Hakenewerth, Paul A., White, James M., Wadia, Aspi B.
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/830,650
• Time in Patent Office: 532 Days
• Field of Search: 356/71, 250/235, 250/236, 250/556, 382/4, 382/5
• US Class Current: 250/235
• CPC Class Codes: A61B 5/1172 using fingerprinting

Abstract

A scanner for scanning an increased area of a finger held or pressed on a concave elliptically cylindrical surface having two focal axes includes a linear light source positioned at one focal axis of a first reflective cylindrical elliptical surface, the other focal axis coinciding with one focal axis of the concave elliptical surface in contact with the finger. A second reflective, cylindrical elliptical surface has two focal axes where one of the axes coincides with the position of a linear array combination of photosensitive elements and charged coupled devices and the other coincides with the other focal axis of the concave elliptical surface in contact with the finger. The linear light source resides within a scanning drum having a longitudinal opening or slit and suitable rotated whereby a line of light is projected along the cylindrical elliptical surface of the first reflective surface whereby light rays are reflected to the finger contact surface to scan a finger held thereon and then totally internally reflected to the second reflective surface and then reflected therefrom as an image on the linear array.

Claims

1. A fingerprint scanner comprising:

a cylindrical elliptically concave finger contact surface in a prism for receiving a finger to be scanned, the finger contact surface having a first focal axis and a second focal axis parallel to said first focal axis;

a first cylindrically elliptical reflecting means having a source focal axis and a sink focal axis, the sink focal axis being the same as said second focal axis, and the source focal axis being parallel to and lying in the plane of said first and second focal axes;

a scanning light source located at said source focal axis of said first cylindrically elliptical reflecting means for scanning a line of light across reflecting means for reflecting the line of light onto said finger contact surface from where it is selectively reflected depending upon whether or not a ridge of a fingerprint is in contact with the finger contact surface at the point of possible reflection;

a second cylindrically elliptical reflecting means having a sink focal axis and a source focal line, the source focal axis being the same as said first focal axis, and the sink focal axis being parallel to and lying in the plane of said first and second focal axes; and

an array of light detectors located at said sink focal axis of said second cylindrically reflecting means for receiving light selectively reflected from the finger contact surface and again reflected from said second reflecting means.

2. The fingerprint scanner of claim 1 wherein said first and second reflecting means are convex surfaces in the prism containing said finger contact surface.

3. The fingerprint scanner of claim 1 wherein said first and second reflecting means are concave mirror surfaces and where the prism finger contact surface further comprises:

a cylindrical surface which is normal to the light reflected from said first reflecting means to said finger contact surface; and

a cylindrical surface which is normal to the light reflected from said finger contact surface to said second reflecting means.

4. A finger press scanner comprising:

light source means for sweeping light rays progressively along an arcuate path,

an optical finger contact surface for supporting a finger to be scanned, said finger contact surface being elliptical and having first and second focal axes for total internal reflection of light rays;

a first elliptical reflective surface positioned to receive light rays from said light source means and reflect the same to said finger contact surface to scan a finger placed thereon, said finger contact surface internally reflecting only those light rays reflected by said first elliptical reflective surface unabsorbed by fingerprint valleys;

light sensing means; and

a second elliptical reflective surface positioned to receive light rays internally reflected by said finger contact surface and reflecting the same to said light sensing means whereby said sensing means produces data signals indicating detection of fingerprint valleys in response to the presence of internally reflected light rays and indicating detection of fingerprint ridges in response to the absence of internally reflected light rays.

5. The finger press scanner of claim 4 wherein said light source means comprises:

a linear light source positioned at one focal axis of said first elliptical reflective surface, and

a rotating drum concentrically positioned about said linear light source and having a longitudinal slot for passing light rays from said linear light source.

6. The finger press scanner of claim 4 wherein said first elliptical reflective surface has a focal axis coinciding with the first focal axis of said optical finger contact surface.

7. The finger press scanner of claim 4 wherein said light sensing means is a linear array combination of photosensitive elements and charge coupled devices located a predetermined position.

8. The finger press scanner of claim 4 wherein said second elliptical reflective surface has a focal axis coinciding with the second focal axis of said finger contact surface.

9. The finger press scanner of claim 7 wherein said second elliptical reflective surface has a focal axis coinciding with the predetermined position of said linear array of charge coupled devices.

10. The finger press scanner of claim 4 wherein said finger contact surface is an elliptically cylindrical surface centered at the minor axis of an ellipse.

11. The finger press scanner of claim 10 wherein said ellipse is a 45 degree ellipse.

12. The finger press scanner of claim 5 wherein said finger contact surface, and said first and second elliptical reflective surfaces are integral surfaces of a unitary optical element.

13. The finger press scanner of claim 12 wherein said unitary optical element further comprises:

a first arcuate surface formed to confront said drum and receive light rays normally passed through said slot, and a second arcuate surface for passing light rays reflected by said second elliptical reflective surface.

14. The finger press scanner of claim 7 further comprising:

cylindrical lens means positioned to receive light rays reflected by said second elliptical reflective surface and focus the same upon said linear array combination of photosensitive elements and charge coupled devices.

15. The finger press scanner of claim 4 wherein said optical finger contact surface is formed in a prism having a first arcuate surface for receiving normally light rays reflected by said first elliptical reflective surface and pass the same to said finger contact surface and a second arcuate surface for normally receiving light rays internally reflected by said finger contact surface and pass the same to said second elliptical reflective surface.