Finger imaging apparatus
First Claim
1. An optical finger image system comprising:
- a platen having a touching surface to receive and support a finger to be interrogated, a light beam source providing an interrogating light beam, said light beam providing a trace at said touching surface, said trace having a maximum width and a maximum length, the maximum width being less than or equal to the maximum length, said width of said trace being no greater than approximately 2hmin/tan Φ
, wherein hmin is a minimum depth of a valley portion of the finger, said light beam source being oriented with respect to said platen such that said light beam forms a predetermined angle Φ
with said touching surface, said light beam illuminating a surface of a finger applied thereto, imaging optics optically downstream from said platen for directing onto an image plane light from said interrogating light beam scattered by a finger on said touching surface, and a photoelectric transducer at said image plane, light detected by said photoelectric transducer being restricted to light falling within a window area, said window area being positioned such that an illuminated ridge portion of said finger is imaged within said window, said predetermined angle Φ
being sufficiently small such that any image of an illuminated valley floor portion of said finger is projected outside said window area.
1 Assignment
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Accused Products
Abstract
In an optical finger image system, a platen is provided to receive and support a finger to be interrogated. A light beam source orients an interrogating light beam onto the platen, so that the beam forms a shallow angle with the platen and intersects the platen at a trace. The light beam illuminates ridge, valley, and ridge/valley edge portions of the finger. An image of the finger generated by the interrogating light beam is focused by imaging optics onto an image plane. A photo-electric transducer array is positioned at the image plane, the transducer array having a window region. The window region is positioned such that illuminated ridge and ridge/valley edge portions of the finger are imaged within the window; while illuminated valley portions of the finger are not imaged in the window. The angle of the light beam incident on the platen is compounded to generate an image of enhanced brightness at ridge/valley edges.
31 Citations
30 Claims
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1. An optical finger image system comprising:
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a platen having a touching surface to receive and support a finger to be interrogated, a light beam source providing an interrogating light beam, said light beam providing a trace at said touching surface, said trace having a maximum width and a maximum length, the maximum width being less than or equal to the maximum length, said width of said trace being no greater than approximately 2hmin/tan Φ
, wherein hmin is a minimum depth of a valley portion of the finger,said light beam source being oriented with respect to said platen such that said light beam forms a predetermined angle Φ
with said touching surface, said light beam illuminating a surface of a finger applied thereto,imaging optics optically downstream from said platen for directing onto an image plane light from said interrogating light beam scattered by a finger on said touching surface, and a photoelectric transducer at said image plane, light detected by said photoelectric transducer being restricted to light falling within a window area, said window area being positioned such that an illuminated ridge portion of said finger is imaged within said window, said predetermined angle Φ
being sufficiently small such that any image of an illuminated valley floor portion of said finger is projected outside said window area.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An optical finger image system comprising:
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a platen having a touching surface to receive and support a finger to be interrogated, a light beam source providing an interrogating light beam, said light beam providing a trace at said touching surface, said trace having a maximum width and a maximum length, the maximum width being less than or equal to the maximum length, said light beam source being oriented with respect to said platen such that said light beam forms a predetermined angle Φ
with said touching surface, said light beam illuminating a surface of a finger applied thereto,imaging optics optically downstream from said platen for directing onto an image plane light from said interrogating light beam scattered by a finger on said touching surface, and a photoelectric transducer at said image plane, light detected by said photoelectric transducer being restricted to light falling within a window area, said window area being positioned such that an illuminated ridge portion of said finger is imaged within said window, said predetermined angle Φ
being sufficiently small such that any image of an illuminated valley floor portion of said finger is projected outside said window area,said light beam including a central ray, said central ray forming a predetermined angle Φ
with said touching surface, and wherein a perpendicular projection of said central ray on said touching surface forms a predetermined angle α
with said trace such that said predetermined angles Φ
, α and
θ
satisfy the equation sinα
·
tanΦ
=tanθ and
such that θ
≧
10°
.
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10. An optical finger image system comprising:
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a platen having a touching surface to receive and support a finger to be interrogated, a light beam source providing an interrogating light beam, said light beam providing a trace at said touching surface, said light beam source being oriented with respect to said platen such that said light beam forms a predetermined Φ
with said touching surface, said light beam illuminating a surface of a finger applied thereto,imaging optics optically downstream from said platen for directing onto an image plane light from said interrogating light beam scattered by a finger on said touching surface, and a photoelectric transducer at said image plane, light detected by said photoelectric transducer being restricted to light falling within a window area, said window area being positioned such that an illuminated ridge portion of said finger is imaged within said window, said predetermined angle Φ
being sufficiently small such that any image of an illuminated valley floor portion of said finger is projected outside said window area, andwherein hmin is a minimum depth of a valley portion of the finger, v is an overlap distance between an image of said trace and said transducer, and m is the magnification of said image, where hmin=(v/m)tan Φ
.
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11. An optical finger image system comprising:
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a platen having a touching surface to receive and support a finger to be interrogated, a light beam source providing an interrogating light beam, said light beam providing a trace at said touching surface, said light beam source being oriented with respect to said platen such that said light beam forms a predetermined angle Φ
with said touching surface, said light beam illuminating a surface of a finger applied thereto, said predetermined angle Φ
is between approximately 1.0° and
approximately −
1.0°
.- View Dependent Claims (12)
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13. In an optical finger image system having at least one interrogating light beam for illuminating a finger placed against a finger touching surface of a platen to provide a modulated light beam, the system having an imaging segment for imaging the modulated light into a photo-electric transducer at an image surface to provide a finger image, the improvement comprising:
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said finger touching surface being substantially dry, the interrogating light beam having an angle of incidence that is more than 30°
from the normal to the finger touching surface at the place where a finger on the surface is being interrogated,the imaging segment providing the finger image at the image surface by focusing only those rays of the modulated light beam that are within the maximum angle of refraction from the finger touching surface of the platen, and the finger image at the image surface being provided in part by light from said interrogating light beam which is modulated by finger surface that is out of contact with the platen. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
a fiberoptic bundle, said fiberoptic bundle having a first end constituting said touching surface and a second end in intimate contact with the photoelectric transducer at said image surface.
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26. The optical finger image system of claim 25 wherein said interrogating light beam has an angle with said finger touching surface that is between approximately plus 1.0°
- and approximately minus 1.0°
.
- and approximately minus 1.0°
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27. The method of optically imaging a finger object comprising the steps of:
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interrogating the finger object on a platen having a dry touching surface with an interrogating light beam having an angle of incidence that is more than 30 degrees from the normal to the finger touching surface at the place where the finger on the platen surface is being interrogated, using said light beams to interrogate a finger surface that is out of contact with the platen to provide a portion of the modulated light that is to be focused on an image surface, and focusing only those rays of the modulated light beam that are within the maximum angle of refraction from the finger touching surface of the platen to provide a finger image at an image surface. - View Dependent Claims (28, 29)
rolling the finger being interrogated on the finger touching surface of the platen while interrogating said rolled finger with an interrogating light beam that has an angle with the plane of the platen that is between −
1° and
+1°
to the plane of the platen.
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30. In an optical finger image system having at least one interrogating light beam for illuminating a finger placed against a finger touching surface of a platen to provide a modulated light beam, the system having an imaging segment for imaging the modulated light into a photo-electric transducer at an image surface to provide a finger image, the improvement comprising:
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said finger touching surface having an anti-reflective coating and a liquid layer on said anti-reflective coating, the interrogating light beam having an angle of incidence that is more than 30°
from the normal to the finger touching surface at the place where a finger on the surface is being interrogated,the imaging segment providing the finger image at the image surface by focusing only those rays of the modulated light beam that are within the maximum angle of refraction from the finger touching surface of the platen, and the finger image at the image surface being provided in part by light from said interrogating light beam which is modulated by finger surface that is out of contact with the platen.
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Specification