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EP0280041A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Direct finger reading

Assignee: Fingermatrix Inc
•
Filing: 1988-01-23
•
Granted: —
•
Expires: 2008-01-23
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Abstract

Abstract The technique for optically scanning a finger to produce a fingerprint image involves positioning the finger surface to be optically scanned so that it is exposed and, in particular, is not pressed against a platen. A slit light beam along the length of the forward part of the finger is circumferentially rotated (38) about an axis (x-x) about the nominal center of the finger. A reflected slit light beam carries modulation information which is focused on a linear array of photo-electric transducers (12) to provide the fingerprint image. The interrogating light is coherent, substantially collimated, light. The plane of the interrogating slit light beam and the plane of the reflected modulated slit light beam are coplanar thereby establishing an illumination plane (42). The illumination plane is parallel to the axis of the finger and is rotated about that axis during the interrogating scan. The illumination plane is slightly offset (d) from that rotational axis and the incident light (16) in the illumination plane impinges on the finger surface at a slight off-normal axis. This offset and off-normal incidence creates two dimensional shadowing. The finger surface being interrogated is positioned slightly off of the object plane for the downstream focusing optics thereby creating a constructive destructive interference effect at the image plane defined by the transducers.

Inventors

  • 👤 Michael Schiller
  • 👤 Daniel H. Marcus

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-08 05:54
CPC Classifications
G; G06; G06V; G06V10/00; G06V10/88; A; A61; A61B; A61B5/00; A61B5/117; A61B5/1171; A61B5/1172; F; F16; F16N; F16N3/00; F16N3/10; F16N3/12; G06V40/00; G06V40/10; G06V40/12; G06V40/13; G06V40/1312; G06V40/1335; G07; G07C; G07C9/00; G07C9/30; G07C9/32; G07C9/37

Claims Analysis

Total Claims: 3
Claim 1
Independent Claim 252 words
In an optical finger image processing apparatus to provide a fingerprint image of a finger held at a predetermined position having illumination means to provide a substantially collimated light beam with an interrogating zone in the form of a slit, said zone being incident on a finger held at said predetermined position; optical focusing means 24 and a linear array of transducers 12 both optically downstream from the finger to receive a modulated light zone in the form of a slit that is reflected from the finger being interrogated by said interrogating zone; the plane of the modulated zone and the plane of the interrogating zone being substantially coplanar to define an illumination plane 42; means 40, 38 to rotate said illumination means, said optical focusing means and said array through a predetermined arc about a predetermined axis (X-X), said predetermined axis being the nominal central axis of the finger being interrogated; rotation through said arc causing said illumination plane to scan an exposed surface of the finger; the light in said illumination plane being incident at a predetermined off-normal angle to the finger surface being interrogated, said off-normal angle being with reference to a plane that is perpendicular to said predetermined axis; the image plane of said transducers being a principal image plane of said optical means for an object plane displaced from the finger object surface being interrogated; the improvement comprising: said illumination plane being parallel to and offset (d) from said predetermined axis during all positions of said rotation.
Claim 2
Dependent Claim 252 words
In an optical finger image processing apparatus to provide a fingerprint image of a finger held at a predetermined position having illumination means to provide a substantially collimated light beam with an interrogating zone in the form of a slit, said zone being incident on a finger held at said predetermined position; optical focusing means 24 and a linear array of transducers 12 both optically downstream from the finger to receive a modulated light zone in the form of a slit that is reflected from the finger being interrogated by said interrogating zone; the plane of the modulated zone and the plane of the interrogating zone being substantially coplanar to define an illumination plane 42; means 40, 38 to rotate said illumination means, said optical focusing means and said array through a predetermined arc about a predetermined axis (X-X), said predetermined axis being the nominal central axis of the finger being interrogated; rotation through said arc causing said illumination plane to scan an exposed surface of the finger; the light in said illumination plane being incident at a predetermined off-normal angle to the finger surface being interrogated, said off-normal angle being with reference to a plane that is perpendicular to said predetermined axis; the image plane of said transducers being a principal image plane of said optical means for an object plane displaced from the finger object surface being interrogated; the improvement comprising: said illumination plane being parallel to and offset (d) from said predetermined axis during all positions of said rotation.
Claim 3
Dependent Claim 17 words
The improvement of claim 1 wherein said substantially collimated interrogating light beam is a coherent light beam.

References Cited (Backward Citations)

EP0048489A1 Cited
DE3424955A1 Cited
EP0168007A2 Cited

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