1. A fingerprint sensor comprising in combination: (a) a sensing member having a sensing surface for pressing a finger thereto; (b) sensing means for sensing the ridges and valleys of the skin of said finger, said sensing means containing a multitude of capacitors located in said sensing member, the size of said capacitors being less than the size of said valleys; and (c) said sensing member containing a multitude of metal plates, each forming a first electrode of said multitude of capacitors, whereby the capacitances of respective ones of said capacitors are locally changed in accordance with said ridges and valleys when said finger is pressed against said surface.