Patent ID: 7518731
Filing Date: 2009-04-14
Classification: G01D,G01L,G01P,G01V

Abstract:
1. A sensing device comprising: 1) a first movable mass, said first movable mass including a first surface; 2) a second movable mass including a second surface; 3) a stationary mass including a stationary surface, said first, second, and stationary surfaces being disposed for receiving a first, second, and third portion of an incoming beam respectively, said first and second mass being arranged to phase shift said first and second portion respectively; 4) a first interference sensor for detecting the displacement of said first mass relative to said stationary mass; 5) a second interference sensor for detecting the displacement of said second mass relative to said stationary mass; and 6) means for performing differential measurement based on the detected signals of said first and second interference sensors.