Abstract

For lateral shearing interferometry, interferograms from two orthogonally sheared directions for complete optical path difference (OPD) are required. We are proposing a new approach for a real-time lateral shear interferometry by applying a phase-shifting method¹ to a double-frequency crossed-grating lateral shear interferometer (LSI).² The double-frequency crossed-grating LSI produces four interferograms, two from ±1 orders of x and y directions, respectively. If we introduce a constant phase-shift Δ to the interferograms in the opposite direction (+Δ for +1 orders and −Δ for −1 orders), the slope data of the OPD can be simultaneously calculated as arctangent values of the four intensity measurements. The instantaneous nature of phase shifting³ to the multiple interferograms allows us to measure the wave fronts from pulsed light sources using array detectors and digital computer analysis.

© 1985 Optical Society of America