Arrangement for the optoelectronic recording of large-area fingerprints

• US 7,567,342 B2
• Filed: 01/27/2006
• Issued: 07/28/2009
• Est. Priority Date: 01/28/2005
• Status: Expired due to Fees

• Current Assignee: Cross Match Technologies GmbH (Assa Abloy AB)
• Original Assignee: Cross Match Technologies GmbH (Assa Abloy AB)
• Inventors: Richter, Uwe, Hillmann, Juergen, Reinhold, Bernd
• Primary Examiner(s): Toatley, Jr.; Gregory J
• Assistant Examiner(s): Valentin; Juan D
• Application Number:
  US11/341,081
• Publication Number:
  US 20060169159A1
• Time in Patent Office: 1,278 Days
• Field of Search: None
• US Class Current: 356/71
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

Abstract

The invention is directed to an arrangement for the optoelectronic recording of large-area fingerprints, particularly for acquiring prints of the entire palm of the hand. The object of the invention is to find a novel possibility for recording the papillary ridge pattern of a hand which permits a complete optoelectronic image recording with one-time placement of large-area concave skin parts without the use of optical beam paths that are subject to contamination and without having to accept a loss of resolution. This object is met, according to the invention, in that the support body for supporting the skin parts has the basic shape of a cylinder providing a portion of the outer surface with a sufficient radian measure and radius as support surface, the end faces of the support body are each provided with a conical recess which is arranged coaxially around the cylinder axis in order to couple in an illumination beam path and an imaging beam path through the surface lines of the conical recesses, and the imaging beam path and a linearly extending image sensor are rotatable synchronously around the cylinder axis in order to record successive line-shaped strips of the frustrated total reflection at the illuminated outer surface of the support body with the supported skin part.

Claims

1. An arrangement for optoelectronic image recording of prints of large-area concave skin parts, particularly whole handprints, comprising:

an optical support body with a convex support surface for supporting the skin parts with large-area contact with the support surface in order to realize an image recording based on frustrated total internal reflection;

a light source for illuminating the support surface;

a readout beam path for transmitting totally internally reflected illumination light to an image sensor;

said support body having the basic shape of a cylinder around a cylinder axis;

said support body having a cylindrical outer surface with a radian measure and radius which are sufficient to provide at least one freely accessible portion of the outer surface as support surface for the large-area concave skin part;

said support body having a first end face and a second end face, each having a conical recess which is arranged coaxially around the cylinder axis;

said light source extending at least parallel to a surface line of the conical recess and being arranged in the conical recess of the first end face;

said readout beam path including an imaging beam path which is connected to the conical recess of the second end face, which imaging beam path images a strip of the support surface that extends in a line-shaped manner along a lateral line of the outer surface of the support body on said image sensor, which is a linearly extending image sensor, at a total internal reflection angle in an axial plane given by the cylinder axis and the strip; and

said linearly extending image sensor and the imaging beam path being rotatable synchronously around the cylinder axis of the support body in order to record successive line-shaped strips of the frustrated total reflection at the illuminated outer surface due to the skin parts contacting the support surface and to combine them to form a two-dimensional image of the skin part resting thereon.

2. The arrangement according to claim 1, wherein the support body is a cylinder sector.

3. The arrangement according to claim 2, wherein the support body is a half-cylinder.

4. The arrangement according to claim 1, wherein a tube which is supported so as to be rotatable around the cylinder axis is provided for synchronous rotation of the image sensor and elements of the imaging beam path, wherein the tube is arranged outside the conical recess of the support body.

5. The arrangement according to claim 1, wherein a tube which is supported so as to be rotatable around the cylinder axis is provided for synchronous rotation of the image sensor and elements of the imaging beam path, wherein the tube is arranged in a cylindrical recess of the support body, which cylindrical recess extends coaxial to the cylinder axis.

6. The arrangement according to claim 5, wherein the imaging beam path is folded into the tube and the cylindrical recess by means of a reflecting surface.

7. The arrangement according to claim 4, wherein a stepper motor is provided for the successive rotation of the tube around the cylinder axis to move the imaging beam path and the image sensor for successive scanning of strips of the support surface of the support body.

8. The arrangement according to claim 7, wherein the light source is a linear light source which is rigidly fastened to the tube, wherein the linear light source is movable parallel to the top of the conical recess at the first end face of the cylindrical support body and synchronous with the imaging beam path around the cylinder axis.

9. The arrangement according to claim 1, wherein the light source has a diffuser arranged downstream thereof in order to generate an intensive background illumination on the inner cylindrical surface of the support body at least along a surface line of the support surface.

10. The arrangement according to claim 9, wherein the light source is a plane projector that is arranged along the surface of the conical recess in order to generate an intensive background illumination on the inner surface of the support body on the entire support surface.

11. The arrangement according to claim 9, wherein the light source is a collimated linear light source which is arranged so as to be rotatable along the surface of the conical recess synchronous with the imaging beam path in order to generate a strip of intensive background illumination along the surface lines of the support surface on the inner surface of the support body.

12. The arrangement according to claim 1, wherein the imaging beam path has at least one imaging optics arrangement for imaging a strip of the cylindrical surface of the support body on the linearly extending image sensor.

13. The arrangement according to claim 12, wherein the imaging beam path contains at least one optical element for correcting the perspective distortion of the strip of the support surface imaged on the image sensor.

14. The arrangement according to claim 13, wherein the imaging beam path has at least one wedge-shaped prism for correcting the perspective distortion of the strip of the support surface imaged on the image sensor.

15. The arrangement according to claim 14, wherein the imaging beam path has two prisms for correcting the perspective distortion and a reflecting surface for folding the beam path.

16. The arrangement according to claim 15, wherein the reflecting surface is that of a separate plane mirror.

17. The arrangement according to claim 15, wherein the reflecting surface is arranged on one of the prisms as a reflecting back surface.

18. The arrangement according to claim 15, wherein the reflecting surface is a back surface of a totally reflecting prism of high-refractive index glass.

19. The arrangement according to claim 15, wherein the first prism is integrated in the cylindrical support body in that the angle (φ

) between the support surface and the conical recess as exit surface of the imaging beam path is appreciably larger than the angle of the total reflection and than the corresponding angle (γ

) of the conical recess on the side of the illumination beam path.

20. The arrangement according to claim 13, wherein the imaging beam path has a curved mirror for partial correction of the perspective distortion and for folding the imaging beam path.

21. The arrangement according to claim 1, wherein heating elements are arranged over a large area on radially extending delimiting surfaces of the support body in the form of a cylinder sector preferably in order to prevent condensation and to promote excretion of perspiration to increase contrast.

22. The arrangement according to claim 1, wherein calibrating devices are arranged on the outer surface of the support body outside the support surface and are covered at least by hoods in order to calibrate and check the imaging beam path.