Apparatus and method for optically imaging features on the surface of a hand

• US 6,175,407 B1
• Filed: 12/17/1998
• Issued: 01/16/2001
• Est. Priority Date: 12/17/1998
• Status: Expired due to Term

• Current Assignee: Morphotrust USA Incorporated (Advent International Corporation)
• Original Assignee: Identix, Inc. (Advent International Corporation)
• Inventors: Sartor, Thomas F.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): SMITH, ZANDRA V
• Application Number:
  US09/215,682
• Time in Patent Office: 761 Days
• Field of Search: 356/71, 382/127, 382/124, 250/227.11
• US Class Current: 356/71
• 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

Apparatus and methods for optically imaging features on the surface of a hand are described. An apparatus in accordance with one implementation includes a fixed light source for illuminating an imaging area, a movable convex contact surface, and a detector. The convex contact surface is exposed to contact a hand and to guide portions of the hand through the imaging area while maintaining contact with the hand. The detector is positioned to intercept light from the imaging area and is adapted to generate therefrom a signal representative of surface features of a hand contacting the contact surface in the imaging area. In accordance with another implementation, a method includes the following steps: placing the hand in contact with a contact surface; guiding the hand in fixed contact with the convex contact surface through an imaging area; illuminating the imaging area with light; intercepting light from the imaging area; and generating from the intercepted light, a signal representative of surface features of the contacting hand being guided through the imaging area.

Claims

1. An apparatus for optically imaging features of a hand, comprising:

a light source to illuminate an imaging area;

a convex contact surface exposed to contact a hand and to guide portions of a hand in fixed contact with the contact surface through the imaging area;

a detector positioned to intercept light from the imaging area and to generate therefrom a signal representative of surface features of a hand contacting the contact surface in the imaging area; and

a damper coupled to the contact surface to adjust the rate at which the contact surface guides portions of a hand through the imaging area.

2. The apparatus of claim 1 wherein the contact surface reflects light produced by the light source.

3. The apparatus of claim 1 wherein the contact surface is convex in shape in the imaging area.

4. The apparatus of claim 1 wherein the contact surface has a constant radius of curvature in the imaging area.

5. The apparatus of claim 1 wherein the contact surface corresponds to the surface of a rotatable cylinder.

6. The apparatus of claim 1 wherein the contact surface is configured to smooth portions of a contacting hand moving through the imaging area.

7. The apparatus of claim 1 wherein the contact surface contacts different portions of a hand as the hand is being guided through the imaging area.

8. The apparatus of claim 1 further comprising a monitor for tracking the position of the contact surface relative to the imaging area.

9. The apparatus of claim 8 wherein the monitor comprises a position encoder.

10. The apparatus of claim 1 wherein the contact surface is configured to guide portions of the hand through the imaging area in a scanning direction, and the imaging area is contained substantially in an image plane that intersects the contact surface along an image line that is substantially orthogonal to the scanning direction.

11. The apparatus of claim 1 wherein the detector is configured to receive primarily light reflecting from the contact surface at an observation angle relative to a normal to the contact surface in the imaging area that is greater than the critical angle for an interface between the contact surface and air.

12. The apparatus of claim 1 wherein the detector is configured to receive primarily light reflecting from the contact surface at an observation angle relative to a normal to the contact surface in the imaging area that is greater than the critical angle for an interface between the contact surface and water.

13. The apparatus of claim 12 wherein the observation angle is less than the critical angle for an interface between the contact surface and the hand being imaged.

14. The apparatus of claim 1 wherein the light illuminating the contact surface in the imaging area is substantially normal to the contact surface in the imaging area.

15. The apparatus of claim 1 wherein the light source and the detector are stationary.

16. The apparatus of claim 1 further comprising a controller for determining when an imaging session has begun.

17. The apparatus of claim 16 wherein the controller is configured to determine when an imaging session has ended.

18. The apparatus of claim 1 wherein the rate at which the hand is guided through the imaging area is about five inches per second or less.

19. An apparatus for optically imaging features on a surface of a hand, comprising:

means for illuminating an imaging area;

means for contacting a hand with a convex contact surface and guiding portions of the hand in fixed contact with the contact surface through the imaging area;

means for intercepting light from the imaging area and generating therefrom a signal representative of surface features of the hand contacting the contact surface in the imaging area; and

means for dampening coupled to the contact surface for adjusting the rate at which portions of the hand are guided through the imaging area.

20. An apparatus for optically imaging features on a surface of a hand, comprising:

a light source to illuminate an imaging area;

a rotatable transparent cylinder having a cylindrical contact surface to contact the hand and configured to guide portions of the hand contacting the contact surface through the imaging area; and

a detector positioned to intercept light from the imaging area and to generate therefrom a signal representative of surface features of the hand contacting the contact surface in the imaging area, the detector being configured to receive primarily light reflecting from the contact surface at an observation angle relative to a normal to the contact surface in the imaging area that is greater than a critical angle for an interface between the contact surface and water.

21. A method for optically imaging features on the surface of a hand, comprising:

placing the hand in contact with a convex contact surface;

guiding the hand in fixed contact with the convex contact surface through an imaging area;

dampening movement of the contact surface to adjust the rate at which the hand moves through the imaging area;

illuminating the imaging area with light;

intercepting light from the imaging area; and

generating from the intercepted light a signal representative of surface features of the contacting hand being guided through the imaging area.

22. The method of claim 21 wherein the guiding step comprises rotating the convex guiding surface through the imaging area.

23. The method of claim 21 wherein the illuminating step comprises illuminating an imaging area that is elongated in a direction that is substantially orthogonal to the direction in which portions of the hand are guided.

24. The method of claim 21 further comprising generating a two-dimensional image of surface features of the contacting hand guided through the imaging area.

25. The method of claim 21 wherein placing the hand comprises placing the palm of the hand against the convex contact surface.

26. The method of claim 21 wherein the hand is guided through the imaging area at a rate of about five inches per second or less.