Patent ID: 7701587
Filing Date: 2010-04-20
Classification: G01B,G01S

Abstract:
1. An apparatus for obtaining an amount of movement of an object, said apparatus comprising: two laser diodes for emitting laser lights; a beam splitter for mixing laser lights emitted from the two laser diodes to generate at least two mixture beams including a first mixture beam and a second mixture beam; a photoconductive device for emitting a terahertz electromagnetic wave when irradiated by the first mixture beam; parabolic mirrors for directing the emitted terahertz electromagnetic wave towards the object, wherein the terahertz electromagnetic wave is reflected by the object; a photoconductive device for detecting the reflected terahertz electromagnetic wave when irradiated by the second mixture beam; and a time delaying system including a movable stage for time-delaying the second mixture beam, wherein the movable stage is controlled based on the detected terahertz electromagnetic wave, wherein when the object is in a first position, a first output in the reflected terahertz electromagnetic wave detected by the photoconductive device for detecting the reflected terahertz electromagnetic wave is obtained, wherein when the object moves from the first position to a second position, a second output in the reflected terahertz electromagnetic wave detected by the photoconductive device for detecting the reflected terahertz electromagnetic wave is obtained, wherein when the object is in the second position, the movable stage of the time delaying system is moved such that an output in the reflected terahertz electromagnetic wave detected by the photoconductive device for detecting the reflected terahertz electromagnetic wave changes from the second output to the first output, and wherein the amount of movement of the object is calculated from an amount of the movement of the movable stage.