Patent ID: 6295131
Filing Date: 2001-09-25
Classification: G01B

Abstract:
An interference detecting system for detecting a phase of interference light occurring between a first laser light of a reference phase and a second laser light of a measuring phase, said interference detecting system comprising:a light divider that divides the interference light into two interference light beams to be directed in two directions;a polarizing light separator that receives one of the interference light beams from said light divider and separates components of said first and second laser lights from the interference light beam received thereby;first and second light detectors that convert respective light energy of the components separated by said polarizing light separator into electric signals;an arithmetic operator that performs an arithmetic operation between the electric signals outputted by said first and second light detectors, said arithmetic operation including an average-evaluating operation;a third light detector that converts light energy of another of the interference light beams from said light divider into an electric signal; anda comparator that compares the electric signal outputted by said third light detector with an output of said arithmetic operator as a reference value, to generate a detection output having a predetermined phase of said electric signal outputted by said third light detector.