Integrated fingerprint sensor
An integrated fingerprint sensor has been developed to be used as an access controller in several kinds of electronic portable devices like cellular phones or labtop computer. The device is composed of a 1.28 cm long row embedding 256 sensitive elements. The sensitive elements are tactile micro cantilevers (100 micron long and 30 micron width) distributed at a pitch of 50 micron along the row.
When the user sweeps its finger on the device the cantilevers are bent down. A piezoresistive gauge placed at the clamped end of each cantilever allows the measurement of the bending and by consequent the measurement of the finger's roughness. The device embeds a read out electronic circuit that manages the scan of the cantilevers row at a frequency of 100 kHz. At each clock pulse, the signal coming from a cantilever is switched to an electronic circuit that amplifies and digitize the signal. The fingerprint sensor is then fully digital. A test board including a programmable integrated circuit drives the fingerprint sensor and records the data.
Specific fingerprint recognition algorithms have been developped to take part of the specificity of the sensor. The algorithms includes directional image filtering, signature extraction and matching steps.
Related publications :
N.Galy, B.Charlot, B.Courtois, "A Full Fingerprint Verification System for a Single-Line Sweep Sensor", IEEE Sensors Journal, Vol.7, issue 7, july 2007, pp. 1054-1065.pdf
B.Charlot, F.Parrain, N.Galy, S.Basrour and B.Courtois, "A Sweeping Mode Integrated Fingerprint Sensor With 256 Tactile Microbeams". IEEE Journal of Microelectromechanical Systems, Vol 13, Issue 4, 2004, pp. 636-644.pdf
N.Galy, B.Charlot, F.Parrain and B.Courtois, "A Full Identification System For A Tactile Fingerprint Sensor", Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, DTIP?04, 12-14 May 2004, Montreux, Switzerland.
B.Charlot, F.Parrain, N.Galy and B.Courtois, "A Sweeping Mode Tactile Integrated Fingerprint Sensor", 12th International conference on solid-state sensors, actuators and microsystems TRANSDUCERS?03, 8-12 June 2003, Boston.
F.Parrain, B.Charlot, N.Galy, B.Courtois, "A CMOS Micromachined Tactile Fingerprint Sensor", Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, 6-8 Mai 2002, Cannes - Mandelieu, France.