Compact optical fingerprint capturing and recognition system
An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, a light source, and a biometric circuit for detecting the presence of a patterned object such as a fingerprint at the light refracting device. Incident light from the light source is projected through a light receiving surface of the light refracting device and is directly reflected off an imaging surface. The resulting image is projected through the focusing lens. The focusing lens has a diameter which is larger than the projection of the patterned object through the light refracting device.
1. 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 light refractor; and
a viewing surface adjacent to the imaging surface and through which an image of the object to be imaged is projected wherein the viewing surface and the imaging surface intersect to form an angle of between 52 and 72 degrees;
at least one focusing lens adjacent to the viewing surface and for receiving and focusing an image of the patterned object projected through the viewing surface, the focusing lens having a diameter that is larger than a projection of the patterned object through the light refractor; 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 light source defining a light source plane and positioned such that substantially all light emitted from the light source in a direction substantially perpendicular to the light source plane directly strikes the imaging surface of the light refractor.
2. The apparatus of claim 1 including a coating placed on the imaging surface, the coating selected from the group consisting of polyethylene, polypropylene and polyethylene terephthalate.
3. The apparatus of claim 2 wherein the light refractor is a five faced triangular prism and the imaging surface includes a first rectangular face of the triangular prism different from both the viewing surface and the light entrance surface.
4. The apparatus of claim 3 wherein the light entrance surface uniformly spreads the incoming light into the light refractor.
5. The apparatus of claim 1 including a biometric circuit having at least one contact located adjacent to the imaging surface, the biometric circuit for detecting the presence of a finger touching the at least one contact.
6. A method of imaging a patterned object comprising:
providing a light refractor having an imaging surface, a light receiving surface and a viewing surface;
forming an angle between the imaging surface and viewing surface of between 52 and 72 degrees;
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;
directly striking the imaging surface with substantially all of the light emitted perpendicularly from the light source to create an image of the patterned object; and
providing a focusing lens adjacent to the viewing surface and which has a diameter that is larger than a projection of the patterned object through the light refractor;
projecting the image of the patterned objection through the focusing lens.
7. The method of claim 6 including the step of the covering the imaging surface with a coating selected from the group consisting of polyethylene, polypropylene and polyethylene terephthalate.
8. The method of claim 7 including the step of detecting the presence of a finger at the imaging surface using a biometric circuit having at least one contact located adjacent to the imaging surface.
9. 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 light refractor; and
a viewing surface adjacent to the imaging surface and through which an image of the object to be imaged is projected wherein the viewing surface and the imaging surface intersect to form an angle of between 52 and 72 degrees;
at least one focusing lens adjacent to the viewing surface and for receiving and focusing an image of the patterned object projected through the viewing surface, the focusing lens having a diameter that is larger than a projection of the patterned object through the light refractor; 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.