| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect a position in a specified allowable measuring time by using a two-beam interference system (LIA system) alignment sensor. SOLUTION: The position of a reference mark is consecutively detected as time sereis data by using the LIA(laser interferometric alignment) system alignment sensor (step 102). The power spectrum I(ω) of the fluctuation of the time series data is calculated (step 103). The power spectrum I'(ω) of the averaged fluctuation is calculated with reference to average timeΔT changing between different measuring timeΔT1 andΔT2 (step 105). Since the dispersion of the time series data averaged by the average timeΔT coincides with the integrated value of the power spectrum I'(ω), the integrated value of the power spectrum I'(ω), that is, the average timeΔTMM when the dispersed valueσof the fluctuation is minimum is obtained (step 106). The obtained average timeΔTMM is defined as the measuring time of the position based on a beat signal obtained by the alignment sensor. |
