System for print imaging with prism illumination optics
View Patent ↗A directionally-oriented reflective device is optically coupled to a prism surface in a skin ridge pattern imaging system to reflect illumination light at relatively small angles, along an optical path to an imaging device, so that minimal light is lost from the optical system. Examples of such directionally-oriented reflective devices include, but are not limited to, echelon reflectors, faceted reflective surfaces, retroreflectors, aluminum paint, nacreous pigment, and slightly rough mirror surfaces.
1. A platen illumination system comprising:
a prism comprising a first side, a second side, a third side and a platen side, such that the first side is between the platen side and the third side and the second side is between the platen side and the third side;
a platen surface coupled to the platen side, the platen surface being configured to receive at least a portion of a hand;
an illumination source optically coupled to the first side, the illumination source configured to generate a beam of radiation for illuminating the platen surface; and
a directionally-oriented reflective device optically coupled to the second side, the directionally-oriented reflective device configured to reflect the beam of radiation towards the platen surface, wherein:
the beam of radiation enters the prism through the first side and reflects from the directionally-oriented reflective device towards the platen surface,
the platen surface is arranged to receive the beam of radiation at a desired angle of incidence, and
the directionally-oriented reflective device is configured such that at least a portion of the directionally-oriented reflective device reflects the beam of radiation at a selected angle of reflection which is different than an angle of incidence of the beam of radiation on the directionally-oriented reflective device, the selected angle of reflection is such that the beam of radiation is incident upon the platen surface at the desired angle of incidence.
2. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a directional scattering element.
3. The platen illumination system of claim 2 , wherein the directional scattering element comprises a roughened mirror surface, nacreous pigment, metallic paint, or retroreflective material.
4. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises an echelon reflector.
5. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a Fresnel mirror.
6. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device includes a plurality of progressively tilted facets.
7. The platen illumination system of claim 6 , wherein the plurality of progressively tilted facets comprise circular groove facets that collectively function as a concave mirror.
8. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device reflects the beam of radiation at the selected angle of reflection such that the beam of radiation further reflects from the platen surface along a telecentric path out of the prism.
9. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a multifaceted reflective surface.
10. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a Fresnel lens between the prism and a reflective element.
11. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a combination of optical elements.
12. The platen illumination system of claim 11 , wherein the combination of optical elements includes a combination of refractive and reflective surfaces.
13. The platen illumination system of claim 11 , wherein the combination of optical elements comprises a Mangin mirror.
14. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a concave mirror.
15. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device comprises a diffractive optical element.
16. The platen illumination system of claim 15 , wherein the diffractive optical element comprises a holographic film.
17. The platen illumination system of claim 9 , wherein the multifaceted reflective surface comprises a plurality of progressively tilted facets.
18. The platen illumination system of claim 17 , wherein the plurality of progressively tilted facets comprises circular groove facets that collectively function as a concave mirror.
19. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device is configured to concentrate or focus the beam of radiation onto the platen surface.
20. The platen illumination system of claim 1 , wherein the directionally-oriented reflective device reflects a plurality of beams of radiation toward the platen surface at a plurality of selected angles of reflection, wherein the plurality of beams of radiation are incident upon the platen surface at a plurality of respective desired angles of incidence with respect to the platen surface.
21. The platen illumination system of claim 20 , wherein the plurality of desired angles of incidence are selected such that a print pattern received on the platen surface can be viewed telecentrically with an imaging device.
22. The platen illumination system of claim 20 , wherein the plurality of desired angles of incidence are selected, such that a print pattern received on the platen surface can be illuminated with at most two light emitting diodes (LEDs).
23. The platen illumination system of claim 1 , wherein the platen surface comprises a surface of the platen side of the prism.
24. The platen illumination system of claim 1 , wherein the platen surface comprises a platen element optically coupled to a surface of the platen side of the prism.
25. The platen illumination system of claim 1 , wherein the selected angle of reflection results in a reduction of scattering of the beam of radiation.
26. The platen illumination system of claim 15 , wherein the diffractive optical element includes a holographic optical element.
27. A system for imaging at least a portion of a hand, comprising:
a prism comprising a first side, a second side, a third side and a platen side, such that the first side is between the platen side and the third side and the second side is between the platen side and the third side;
a platen surface coupled to the platen side, the platen surface being configured to receive at least a portion of a hand;
an illumination source optically coupled to the first side, the illumination source configured to generate a beam of radiation for illuminating the platen surface;
a directionally-oriented reflective device optically coupled to the second side, the directionally-oriented reflective device configured to reflect the beam of radiation towards the platen surface;
an imaging device configured to view the platen surface telecentrically; and
an aperture stop between the imaging device and the platen surface, the aperture stop configured to transmit at least a portion of the beam of radiation from the platen surface along a telecentric path before imaging of the at least a portion of the beam of radiation by the imaging device, wherein:
the beam of radiation enters the prism through the first side and reflects from the directionally-oriented reflective device towards the platen surface,
the platen surface is arranged to receive the beam of radiation at a desired angle of incidence, and
the directionally-oriented reflective device is configured such that at least a portion of the directionally-oriented reflective device reflects the beam of radiation at a selected angle of reflection which is different than an angle of incidence of the beam of radiation on the directionally-oriented reflective device, wherein:
the selected angle of reflection is such that the beam of radiation is incident upon the platen surface at the desired angle of incidence, and
the desired angle of incidence is arranged to result in reflection of the beam of radiation from the platen surface along the telecentric path to the aperture, wherein an intensity of the at least a portion of the beam of radiation transmitted by the aperture and collected by the imaging device is maximized.