Patent ID: 7729881
Filing Date: 2010-06-01
Classification: G01B

Abstract:
1. A laser interferometric apparatus for measuring a displacement of an object, the apparatus comprising: a laser source for producing a laser beam having a given intensity; a first beam splitter for dividing the laser beam into a reference beam and an object beam to be directed to the object, thereby producing a scattered object beam being modulated according to the displacement of the object; a second beam splitter for combining the scattered object beam and the reference beam, thereby providing at least one interference beam; at least one array of detectors for receiving the at least one interference beam, each detector of the array receiving a portion of the at least one interference beam to form an electrical interference signal, the electrical interference signal comprising a wanted signal component indicative of the object displacement and a substantially equal intensity noise component; and a processing circuit comprising a differential amplifier for subtracting at least two electrical interference signals formed by at least two portions of the interference beam, thereby generating a displacement signal, the displacement signal comprising substantially the wanted signal component alone, wherein the intensity noise is substantially rejected, wherein each detector contained in the at least one array of detectors comprises an automatic gain control circuit to normalize the amplitude of one of the at least two electrical interference signals to the amplitude of the other of the at least two electrical interference signals.