Imaging device, especially for optical fingerprinting
First Claim
1. An optical imaging device comprisinga light transmitting element having at least a first surface on which an imaged object can be placed and at which incident light beam transmitted through the light transmitting element may undergo frustrated total internal reflection, and a second surface through which light reflected from the first surface may exit as a reflected beam, an image sensor disposed at a distance from the light transmitting element for receiving an image of said object from said light transmitting element, a lens disposed in the path of said reflected beam between the light transmitting element and the sensor for focusing said reflected beam to produce a focused beam, the lens having two dissimilar surfaces, a first refractive convex surface facing the incident reflected beam from the light-transmitting element, and a second surface having a significantly lesser curvature than said first convex surface, and a reflective surface disposed adjacent said second surface for reflecting said reflected beam through said refractive surface, onto said image sensor so that an image of said object can be detected, wherein the incident reflected beam passes through said refractive surface immediately before reflection off of the reflective surface and the reflected beam passes through said refractive surface immediately after reflection off of the reflective surface.
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0 Petitions
Accused Products
Abstract
An optical imaging device such as a fingerprint imager has a prism or another light transmitting element, a light source for illuminating a finger placed on the prism, and a CCD image sensor for receiving a light beam reflected from the finger-contacted surface. A modified optical lens is used to focus and redirect the reflected light beam. The lens has a relatively small reflective coating in the middle of its back surface, the reflective coating constituting an optical iris. The modified lens is effective to partly correct for peripheral aberration, perspective distortion and depth-of-field image distortion of the device and gives rise to a compact design of the device.
148 Citations
16 Claims
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1. An optical imaging device comprising
a light transmitting element having at least a first surface on which an imaged object can be placed and at which incident light beam transmitted through the light transmitting element may undergo frustrated total internal reflection, and a second surface through which light reflected from the first surface may exit as a reflected beam, an image sensor disposed at a distance from the light transmitting element for receiving an image of said object from said light transmitting element, a lens disposed in the path of said reflected beam between the light transmitting element and the sensor for focusing said reflected beam to produce a focused beam, the lens having two dissimilar surfaces, a first refractive convex surface facing the incident reflected beam from the light-transmitting element, and a second surface having a significantly lesser curvature than said first convex surface, and a reflective surface disposed adjacent said second surface for reflecting said reflected beam through said refractive surface, onto said image sensor so that an image of said object can be detected, wherein the incident reflected beam passes through said refractive surface immediately before reflection off of the reflective surface and the reflected beam passes through said refractive surface immediately after reflection off of the reflective surface.
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12. An optical imaging device comprising
a light transmitting element having at least a first surface on which an imaged object can be placed and at which incident light beam transmitted through the light transmitting element may undergo frustrated total internal reflection, and a second surface through which light reflected from the first surface may exit as a reflected beam, an image sensor disposed at a distance from the light transmitting element for receiving an image of said object from said light transmitting element, a lens disposed in the path of said reflected beam between the light transmitting element and the sensor for focusing said reflected beam to produce a focused beam, the lens having two dissimilar surfaces, a first refractive convex surface facing the incident reflected beam from the light-transmitting element, and a second surface having a significantly lesser curvature than said first convex surface, and a reflective coating applied contiguously on said second surface about the optical axis of said lens and sized to correspond to a portion less than the whole of said second surface, for reflecting said reflected beam passed through said refractive surface, onto said image sensor so that an image of said object can be detected.
Specification