Optics: measuring and testing – Document pattern analysis or verification
Reexamination Certificate
1998-12-17
2001-01-16
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Document pattern analysis or verification
C382S124000, C382S127000, C250S227110
Reexamination Certificate
active
06175407
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to apparatus and methods for optically imaging features on a surface of a hand, such as fingerprints and palmprints.
Fingerprints and palmprints are commonly taken by applying ink to the surface of the skin and then transferring the ink to a paper medium for recording. The application of ink to the skin and the subsequent transfer to paper requires a skilled expert to produce high quality images. Optical systems for scanning fingerprint and palmprint images have been developed to avoid problems associated with ink-based methods. In common optical systems, a hand to be scanned is held against a transparent platen, and an optical detector scans light reflecting from the interface between the hand and the platen to generate signals representative of fingerprint or palmprint images. These signals are digitized, stored in digital computer memory, and processed for transmission or printing.
SUMMARY OF THE INVENTION
In one aspect, the invention features an apparatus for optically imaging features of a hand, comprising: a light source for illuminating an imaging area; a convex contact surface exposed to contact a hand and to guide portions of a hand in fixed contact with the convex contact surface through the imaging area; and a detector positioned to intercept light from the imaging area and to generate therefrom a signal representative of surface features of a hand contacting the contact surface in the imaging area.
In another aspect, the invention features a method for optically imaging features on a surface of a hand, comprising: placing the hand in contact with a convex contact surface; guiding the hand in fixed contact with the contact surface through an imaging area; illuminating the imaging area with light; intercepting light from the imaging area; and generating from the intercepted light, a signal representative of surface features of the hand being guided through the imaging area.
Embodiments may include one or more of the following features.
The contact surface may reflect light produced by the light source. The contact surface may be convex in shape in the imaging area. The contact surface may have a constant radius of curvature in the imaging area. The contact surface may correspond to the surface of a rotatable cylinder. The contact surface may be configured to smooth portions of a contacting hand moving through the imaging area. The contact surface may contact different portions of a hand as the hand is being guided through the imaging area.
A damper may be coupled to the contact surface for adjusting the rate at which the contact surface guides portions of the hand through the imaging area. A monitor (e.g., a position encoder) may be provided for tracking the position of the contact surface relative to the imaging area. The contact surface may be adapted to guide portions of the hand through the imaging area in a scanning direction. The imaging area may be contained substantially in an image plane that intersects the contact surface along an image line that is substantially orthogonal to the scanning direction.
The detector may be configured to receive primarily light reflecting from the contact surface at an observation angle relative to a normal to the contact surface in the imaging area that is greater than the critical angle for an interface between the contact surface and air. The detector may be configured to receive primarily light reflecting from the contact surface at an observation angle relative to a normal to the contact surface in the imaging area that is greater than the critical angle for an interface between the contact surface and water. The observation angle may be less than the critical angle for an interface between the contact surface and the hand being imaged.
The light illuminating the contact surface in the imaging area may be substantially normal to the contact surface in the imaging area. The light source and the detector may be stationary. A controller may be provided for determining when an imaging session has begun. The controller may be configured to determine when an imaging session has ended.
Portions of a hand may be guided through the imaging area by rotating the convex guiding surface through the imaging area. An imaging area that is illuminated may be elongated in a direction that is substantially orthogonal to the direction in which portions of the hand are guided. A two-dimensional image of surface features of the contacting hand guided through the imaging area may be generated. The writer's palm of the hand may be placed against the convex contact surface to obtain a print of the writer's palm.
The invention can be used to obtain a complete print of a hand, including the palm and the sides of the hand. The invention can be implemented by an apparatus having a compact footprint. Also, because the contact surface guides the hand through the imaging area, as opposed to optically scanning a stationary hand, the invention can print a hand of any length—that is, the length of the print is not limited by the footprint of the imaging apparatus. Furthermore, because the contact surface is convex in shape, the invention can properly image surface features corresponding to the interior of the palm. The invention can also image the four fingers of a hand, either separately or as part of an image of the whole hand.
Other features and advantages will become apparent from the following description, including the drawings and the claims.
REFERENCES:
patent: 4032889 (1977-06-01), Nassimbene
patent: 4322163 (1982-03-01), Schiller
patent: 4685145 (1987-08-01), Schiller
patent: 4784484 (1988-11-01), Jensen
patent: 5177802 (1993-01-01), Fujimoto et al.
patent: 5195145 (1993-03-01), Backus et al.
patent: 5416573 (1995-05-01), Sartor
patent: 5526436 (1996-06-01), Sekiya
patent: 5528355 (1996-06-01), Maase et al.
Fish & Richardson P.C.
Font Frank G.
Identix Incorporated
Smith Zandra
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