High contrast, low distortion optical acquistion system for image capturing
AssigneeSecuGen Corporation
InventorsHarry H. Teng, Sung-Chan Jo
Life of this patent
Estimating the term…
Abstract
An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, and a light source. The light refracting device can, for example, be a prism and includes an imaging surface, a light receiving surface and a viewing surface. Incident light from the light source is projected through the light receiving surface and reflected off a surface other than the imaging surface. This reflected light is then projected onto the imaging surface to create an image of the patterned object from substantially all scattered light through the viewing surface. The lens is placed adjacent to the viewing surface to focus the light on an image sensor.
Claims28
A compact apparatus for forming a high contrast, low distortion image of a patterned object including:
- a light refractor for reflecting and refracting light, the light refractor including:
- an imaging surface against which a patterned object to be imaged is to be placed;
- at least one light entrance surface adjacent to the imaging surface and through which light enters the refractor;
- and
- a viewing surface adjacent to the imaging surface and through which an image of the object to be imaged is projected and which is the same surface as the light entrance surface;
- a further surface positioned between and different from the imaging surface and the light entrance surface;
- at least one focusing lens adjacent to the viewing surface and for receiving and focusing an image of a patterned object projected through the viewing surface;
- and
- at least one light source located adjacent to the light receiving surface and for emitting incident light which enters the light refractor to create an image of the patterned object at the viewing surface, the image focused by the at least one focusing lens, the light source positioned such that light emitted therefrom and entering the light refractor strikes at least the further surface at an angle greater than the critical angle of the further surface before striking the imaging surface at an angle less than the critical angle of the imaging surface such that the image of the patterned object from the imaging surface and projected through the viewing surface is generated by substantially all scattered light from the imaging surface.
A method of imaging a patterned object comprising:
- providing a light refractor having an imaging surface, a light receiving surface, a viewing surface which is the same as the light receiving surface and a further surface different from and between the light receiving surface and the imaging surface;
- placing the patterned object against the imaging surface of the light refractor;
- projecting incident light from a light source through the light receiving surface of the light refractor;
- reflecting the incident light off at least the further surface at an angle greater than the critical angle of the further surface before the incident light strikes the imaging surface at an angle less than the critical angle of the imaging surface and
- scattering the incident light off the imaging surface and patterned object and through the viewing surface.
Dependencies are inferred from the claim text.