Patent ID: 7164479

Claim:
Optical displacement sensor, comprising two essentially flat surfaces ( 1 , 2 ) provided on respective element parts ( 3 , 4 ) being separated by a cavity being defined by a spacer ( 5 ), the distance (d) between the surfaces ( 1 , 2 ) being variable thus providing a displacement sensitive Fabry-Perot interferometer, wherein both of said surfaces ( 1 , 2 ) are at least partially reflective, and said first surface ( 1 ) being provided with at least one optical detector ( 7 ) and one of said element parts ( 3 , 4 ) being made of an at least partially transparent material, wherein said optical detector ( 7 ) comprises a number of concentric ring shaped detectors symmetrically positioned relative to the optical axis of the Fabry-Perot interferometer, the sensor also comprising a light source ( 6 ) directed toward said surfaces ( 1 , 2 ), said light source ( 6 ) being sufficiently monochromatic and point shaped to provide interference with the Fabry-Perot interferometer.