Fingerprint identification device-equip with a touch sensor for detecting a human finger

摘要

A fingerprint identification device judges that the input fingerprint is identical to the fingerprint in the database only when a the touch sensor detects the human finger and a the fingerprint processing unit detects that the input fingerprint is identical to a fingerprint in the database. The touch sensor includes an oscillator that outputs a high frequency signal. An electrode unit applies the high frequency signal to the human finger. A detector unit detects a variation of impedance values varied by the human finger contracting the electrode unit and outputs an output signal based on the variation of impedance values. A discriminator unit determines whether the human finger is in contact with the electrode unit by comparing the output signal from the detector unit with a predetermined reference value.