Device for forming and detecting fingerprint images with valley and ridge structure

• US 5,974,162 A
• Filed: 02/27/1995
• Issued: 10/26/1999
• Est. Priority Date: 02/18/1994
• Status: Expired due to Fees

• Current Assignee: Stanley H. Kremen
• Original Assignee: Imedge Technology Incorporated
• Inventors: Metz, Michael, Flatow, Carl, Coleman, Zane, Phillips, Nicholas J.
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Do, Anh Hong
• Application Number:
  US08/394,470
• Time in Patent Office: 1,702 Days
• Field of Search: 382/124, 382/126, 382/116, 382/210, 382/125, 382/127, 356/71
• US Class Current: 382/124
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G06K 7/10663 using hologram
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• CPC Class Codes: G06K 7/1098 the scanning arrangement having a modular construction
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence
• CPC Class Codes: G07C 9/37 using biometric data, e.g. fingerprints, iris scans or voice recognition

Abstract

A method and ultra-compact system has been developed for illuminating and detecting the surface topography of an object such as the finger of an individual. The system is capable of producing high-contrast images which can be electronically transmitted in real-time, or stored using electronic or photographic recording devices. Light traveling within a light transmitting substrate is redirected by a slanted-fringe light diffractive grating preferably embodied within a volume hologram. The volume hologram, either of the reflection or transmission type, is attached to the light transmitting substrate, and functions to diffract light striking thereupon and illuminate an object having topographical surface structure. After being spatially and intensity modulated in accordance with topographical details of the illuminated object, the modulated light passes back through the light transmitting substrate and the volume hologram, onto an image detection array, for subsequent analysis. Each of the disclosed embodiments has a compact geometry suitable for use in diverse object identification applications.

Claims

1. A device for producing an image of a fingerprint having ridges and valleys, said device comprising:

light producing means for producing light rays;

a light transmitting substrate capable of transmitting the light produced by said light producing means;

a fingerprint illuminating region for physical placement of a finger bearing a fingerprint;

an image detection means for detecting an image of said fingerprint;

an optical element affixed to a portion of said light transmitting substrate and being disposed between said fingerprint illuminating region and said image detection means, said optical element embodying a light diffracting grating;

wherein said fingerprint illuminating region, said optical element and said image detection means are each disposed substantially along a common optical axis; and

wherein during the operation of said device,

(1) light rays produced by said light producing means, propagate within said light transmitting substrate towards said optical element and are diffracted by said light diffracting grating,

(2) diffracted light rays produced by said light diffracting grating, propagate directly towards said fingerprint illuminating region and fall incident upon and are intensity modulated by the ridges and valleys of said fingerprint, and

(3) intensity modulated light rays produced from said ridges and valleys propagate directly back through light transmitting substrate and said optical element and fall incident upon said image detection means, whereupon an image of said fingerprint is detected, said detected image including information corresponding to said ridges and valleys of said fingerprint.

2. The device of claim 1, wherein said light transmitting substrate has an upper surface in which said fingerprint illuminating region is disposed, and a lower surface arranged opposite said upper surface.

3. The device of claim 2, wherein said light diffracting grating comprises light diffracting structures that are slanted with respect to the upper and lower surfaces of said light transmitting substrate.

4. The device of claim 3, wherein said optical element is affixed to the lower surface of said light transmitting substrate.

5. The device of claim 4, wherein said light diffracting grating is a hologram containing a slanted fringe structure.

6. The device of claim 5, wherein said hologram is a volume hologram.

7. The device of claim 6, wherein said volume hologram is of the reflection type.

8. The device of claim 3, wherein said optical element is affixed to the upper surface of said light transmitting substrate, between said fingerprint illuminating region and said light transmitting substrate.

9. The device of claim 8, wherein said light diffracting grating is a hologram containing a slanted fringe structure.

10. The device of claim 9, wherein said hologram is a volume hologram.

11. The device of claim 10, wherein said volume hologram is of the transmission type.

12. The device of claim 8, which further comprises a light transmitting superstrate affixed to said upper surface of said optical element, and in which said fingerprint illuminating region is disposed.

13. The device of claim 12, wherein said light transmitting substrate, said optical element, said superstrate and said light producing means are contained within a compact housing having an access aperture through which said fingerprint can he placed in physical contact with said light transmitting superstrate, within said fingerprint illuminating region.

14. The device of claim 2, which further includes electronic circuitry for interfacing said image detection means with a computer-based system.

15. The device of claim 3, wherein said light transmitting substrate, said optical element and said light producing means are contained within a compact housing having an access aperture through which said fingerprint can be brought into physical contact with said light transmitting substrate, within said fingerprint illuminating region.

16. The device of claim 1, wherein said image detection means is an electro-optical image detector.

17. The device of claim 16, wherein said electro-optical image detector is an image detection array.

18. The device of claim 1, wherein said light producing means produces substantially monochromatic light.

19. The device of claim 1, wherein said light producing means comprises a white light source for producing white light.

20. The device of claim 19, which further comprises a narrow wavelength bandpass filter disposed between said white light source said light transmitting substrate.

21. The device of claim 1, which further comprises a narrow wavelength bandpass filter disposed substantially along said optical axis and between said optical element and said image detection means.

22. The device of claim 1, which comprises an image transfer means disposed between said image detection means and said optical element.

23. The device of claim 22, wherein said image transfer means is a structure selected from the group consisting of a lens system, a microchannel plate a fiber optic array, and a micro-lens array.

24. The device of claim 1, in combination with an image storage means for storing images produced by said image detection means.

25. The combination of claim 24, which further comprises an image analyzer and an image database.

26. The device of claim 1, wherein said light producing means is a structure selected from the group consisting of a monochromatic light source, a small filament incandescent lamp, and a light emitting diode.

27. The device of claim 1, wherein said light diffracting produces converging light rays when said light rays strike said light diffracting grating.

28. The device of claim 1, wherein said light diffracting grating produces substantially collimated light rays when said light beam strikes said light diffracting grating.

29. The device of claim 1, wherein said light diffracting grating produces diverging light rays when said light rays strike said light diffracting grating.

30. The device of claim 1, wherein the indices of refraction of said light transmitting substrate and said optical element are matched to optimize light transmission efficiency therebetween.

31. The device of claim 1, wherein light rays produced from said light producing means strike said light diffracting grating such that the first diffraction order of said diffracted light travels along said optical axis at an angle with respect to said optical axis, which is less than the critical angle for said light transmitting substrate.

32. The device of claim 1, wherein said fingerprint illuminating region is associated with a portion of said light transmitting substrate about said optical axis.

33. The device of claim 1, wherein said fingerprint illuminating region is associated with a portion of said optical element about said optical axis.

34. The device of claim 1, which further comprises a light transmitting substrate operably associated with said optical element.

35. The device of claim 1, which further comprises a PCMCIA-type housing containing said light producing means, said light transmitting substrate, said optical element, and said image detection means.