公开(公告)号：US20020097059A1

公开(公告)日：2002-07-25

申请号：US10054182

申请日：2002-01-18

Applicant: STMicroelectronics, Inc.

Inventor： Marco Tartagni ,  Bhusan Gupta ,  Alan Kramer

IPC: G01R027/26

CPC classification number: G01B7/023 ,  G01B7/004 ,  G01B7/287 ,  G01B7/34 ,  G06K9/0002

Abstract: A distance sensor has a capacitive element in turn having a first capacitor plate which is positioned facing a second capacitor plate whose distance is to be measured. In the case of fingerprinting, the second capacitor plate is defined directly by the skin surface of the finger being printed. The sensor comprises an inverting amplifier, between the input and output of which the capacitive element is connected to form a negative feedback branch. By supplying an electric charge step to the input of the inverting amplifier, a voltage step directly proportional to the distance being measured is obtained at the output.