Image analysis – Applications – Personnel identification
Patent
1997-11-20
2000-10-03
Bella, Matthew
Image analysis
Applications
Personnel identification
382127, 382126, 382314, 382315, 358474, 358483, 358484, G06K 900
Patent
active
061283991
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a fingerprint sensor device capable of detecting the ridges and furrows of a phalanx.
Such optical devices are already in existence, for example the device described in document FR-A-2 235 431, which devices make use of a two-dimensional array of detection sites associated with a recognition system.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a fingerprint sensor device that satisfies practical requirements better than presently-known devices, particularly because of its simplicity and its suitability for distinguishing well between ridges and furrows, and thus for delivering a fingerprint with sharp lines.
To this end, the invention provides a fingerprint sensor device comprising: end of a finger and carrying on an inside face a two-dimensional matrix of photosensitive elements which are distributed at a regular pitch of not more than 90 .mu.m and which are separated by strip-forming transparent gaps that are generally of a width that is smaller than the width of the photosensitive elements; directing a light beam through the support via the gaps of the support and substantially orthogonally to said outside face; and said photosensitive elements being protected against the light coming from the sources so as to deliver an output signal only in response to light that has been back-scattered by the furrows towards the outside face of the support.
Each of the component elements of the device can be implemented in various different ways.
In advantageous embodiments, the sources are constituted by thin film light emitting diodes deposited on the inside face of the substrate, by parallel strips of light emitting diodes, or by a continuous flat component. By way of example, such a flat component may be formed by a plate of diffusing material such as acrylic resin, with the bottom face thereof carrying light emitting diodes that may be far fewer in number than the photosensitive elements, thereby reducing the cost of the device. The light emitting diodes (LEDs) may be stuck to the bottom face of the support, optionally in cavities provided for this purpose. The substrate may thus constitute a component which deflects or diffuses towards the support, light received from sources placed laterally or longitudinally relative thereto. The support which is a few millimeters thick can then be treated to constitute semitransparent micromirrors reflecting the light towards the gaps.
In general, the sources may be fixed on the outside face or on the inside face of the substrate or on one or more edges thereof.
The photosensitive elements may also be of various structures. They may be photodiodes integrated in a thin film of silicon belonging to the support or constituting the support. They may be thin film phototransistors, similar to those used in flat display screens. They may also be photo cells.
Usable sources that are available at low cost are specifically sources that emit in the visible range; in general, such sources are used together with photosensitive elements that are matched so as to present high sensitivity in the emission band of the source.
The above characteristics and others appear more clearly on reading the following description of a particular embodiment of the invention given by way of non-limiting example. The description refers to the accompanying drawing, in which.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overall perspective view showing one possible structure for a sensor device; and
FIG. 2 is a diagrammatic section view for showing how ridges and furrows are distinguished when the sensor is taking a fingerprint.
DESCRIPTION OF THE EMBODIMENTS
The sensor device described by way of example is associated with a system for processing the resulting signals. The system may be of any of the types presently known, for example it may be of the type described in above-mentioned document FR-A-2 235 431, to which reference may be made.
The sensor device shown diagrammatically in FIG. 1 can be considered as co
REFERENCES:
patent: 4394773 (1983-07-01), Ruell
patent: 5050220 (1991-09-01), Marsh et al.
patent: 5088817 (1992-02-01), Igaki et al.
patent: 5325442 (1994-06-01), Knapp
patent: 5448649 (1995-09-01), Chen et al.
patent: 5544338 (1996-08-01), Forslund
Bella Matthew
Chawan Sheela
Sagem SA
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