Measuring method and measuring apparatus

摘要

A measuring arrangement includes forming first and second pairs of light beams each having a low frequency light beam and a high frequency light beam. Both pairs of light beams generate beat signals of the same frequency. The low frequency light beam of either pair and the high frequency of the other pair pass through a predetermined optical path to cause phase changes in the same direction. Beat signals are generated by superposing the first and second beam pair to provide measurement information on the phase changes.