Holographic fingerprint device

• US 6,061,463 A
• Filed: 12/22/1997
• Issued: 05/09/2000
• Est. Priority Date: 02/21/1995
• Status: Expired due to Fees

• Current Assignee: Stanley H. Kremen
• Original Assignee: Imedge Technology Incorporated
• Inventors: Coleman, Zane, Metz, Michael, Flatow, Carl, Phillips, Nicholas J
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Do, Anh Hong
• Application Number:
  US08/696,954
• Time in Patent Office: 869 Days
• Field of Search: 382/124, 382/126, 382/127, 356/71, 356/448
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

Abstract

A method and ultra-compact system has been developed for illuminating and detecting the surface topography of an object such as the finger (4) of an individual. The system (8) 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 (2) is redirected by a slanted-fringed light diffractive grating preferably embodied within a volume hologram (3). The volume hologram (3), either of the reflection or transmission type, is attached to the light transmitting substrate (2). 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 insulated light passes back through the light transmitting substrate (2) and the volume hologram (3), 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 of compact construction for producing an image of the topographical surface structure of an object, comprising:

a light transmitting substrate having an index of refraction N1, capable of transmitting light;

an object illuminating region for illuminating an object in proximity therewith;

an optical element having an index of refraction N2 and embodying a light-diffractive grating, said optical element being affixed to a portion of said light transmitting substrate, and disposed about an optical axis passing through said object illuminating region; and

light producing means for producing light rays for propagation within said light transmitting substrate, and towards said optical element, said light diffractive grating defining means for redirecting light rays incident thereon to a different optical axis and for propagating the redirected light rays along said different optical axis towards said object;

whereupon said light rays fall incident upon the object disposed proximate to said object illuminating region, are modulated by the topographical surface structure of the object and propagate back through said light transmitting substrate and said optical element substantially along said different optical axis and fall incident upon an image detection means positionable substantially about said different optical axis, so as to detect an image of the topographical surface structure of the object, wherein the image propagated through said light transmitting substrate and said optical element is along substantially the same optical axis along which light was previously propagated toward the object.

2. The device of claim 1, which further comprises said image detection means disposed substantially about said optical axis, for detecting an image of the topographical surface structure of the object.

3. The device of claim 2, wherein said image detection means is an electro-optical image detector optically coupled to said optical element.

4. The device of claim 3, wherein said electro-optical image detector is an image detection array.

5. The device of claim 2, which further comprises an image transfer means disposed between said image detection means and said optical element.

6. The device of claim 5, wherein said image transfer means is a structure selected from the group consisting a lens system, a microchannel plate, a fiber optic array, and a micro-lens array.

7. The device of claim 2, in combination with an image storage means for storing images produced by said image detection means.

8. The device of claim 7, which further comprises an image analyzer and an image database.

9. The device of claim 2, which further includes a linear polarizing filter optically interposed intermediate said optical element and said image detection means.

10. The device of claim 1, wherein said optical element is a volume hologram embodying said light diffractive grating.

11. The device of claim 10, wherein said light diffractive grating has slanted fringes.

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

13. The device of claim 12, wherein said optical element is affixed to the lower surface of said light transmitting substrate, substantially about said optical axis.

14. The device of claim 13, wherein said optical element is a reflection-type hologram.

15. The device of claim 12, wherein said optical element is affixed to the upper surface of said light transmitting substrate, substantially about said optical axis.

16. The device of claim 15, wherein said optical element is a transmission-type hologram.

17. The device of claim 1, 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 the object can be brought into optical communication with said light transmitting substrate along said optical axis.

18. The device of claim 17, wherein said compact housing further includes electronic circuitry for interfacing said image detection means with a computer-based system.

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

20. The device of claim 1, wherein said light producing means produces white light.

21. 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.

22. The device of claim 1, wherein said light diffractive grating produces converging light rays when said light beam strikes said light diffractive grating.

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

24. The device of claim 1, wherein said light diffractive grating produces diverging light rays when said light beam strikes said light diffractive grating.

25. The device of claim 1, wherein said indices of refraction N1 and N2 are matched to optimize light diffraction efficiency.

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

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

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

29. The device of claim 1, which further comprises a light transmitting superstrate having an upper surface and a lower surface, said superstate being operably associated with said optical element.

30. The device of claim 1, which further comprises a PCMCIA housing containing the operative elements of said device.

31. The device of claim 1, further comprising a second optical element affixed to said light transmitting substrate, said second optical element being disposed to receive light from said light producing means to allow the light to enter and travel through said light transmitting substrate, with or without reflecting via total internal reflection from the upper and/or lower surface of said light transmitting substrate, and to fall incident upon said first optical element.

32. The device of claim 31, in which said first and second optical elements are affixed to opposite surfaces of said light transmitting substrate.

33. The device of claim 31, in which said first and second optical elements are affixed to the same surface of said light transmitting substrate.

34. The device of claim 31, in which said first and second optical elements are respectively first and second holograms.

35. The device of claim 32, in which said first and second optical elements are each reflection holograms.

36. The device of claim 33, in which said first optical element is a reflection hologram and said optical element is a transmission hologram.

37. The device of claim 1, further comprising a narrow-band filter optically interposed intermediate said optical element and said image detection means.

38. The device of claim 37, in which said optical element is a volume hologram and said filter is tuned to the output wavelength of said volume hologram.

39. The device of claim 1, further comprising a narrow band filter optically interposed intermediate said light transmitting substrate and said image detection means.

40. The device of claim 39, in which said optical element is a volume hologram, and said filter is tuned to the wavelength of said volume hologram.

41. The device of claim 1, which further includes a quarter wave plate polarizing filter optically interposed intermediate the object and said optical element.

42. The device of claim 29, in which said optical element is interposed between said substrate and said superstrate, and said superstrate is affixed to or located proximate to said upper surface of said optical element.

43. The device of claim 42, wherein said object illuminating region is disposed upon said upper surface of said superstrate.

44. The device of claim 43, in which the light from said light producing means passes through said substrate and into said optical element at an off-Bragg angle, passing through said optical element and through said superstrate to strike said object illuminating region at an angle greater than the critical angle for said superstrate, whereupon light reflected from the superstrate-object interface travels back through said superstrate, into said optical element, and gets diffracted by said optical element so that it subsequently travels substantially along said optical axis formed between said object and said image detection means.

45. The device of claim 43, which further includes an index discontinuity layer between said superstrate and said optical element, said index discontinuity layer having an index of refraction less than the index of refraction of said optical element.

46. The device of claim 45, wherein light from said light producing means passes through said substrate and through said optical element at an off-Bragg angle, and is totally internally reflected at the interface between said optical element and said index discontinuity layer, whereupon light is diffracted by said optical element to pass through said index discontinuity layer and said superstrate substantially along said optical axis to impinge on said object illuminating region and illuminate said object.