Single-shot quasi-absolute wavefront measurement of a plane mirror with wedge-induced lateral-shearing interferometry

Abstract On-line wavefront measurement in real time is constrained by the susceptibility of multi-exposure interferometry to air turbulence and vibration. Here we propose a single-shot approach for a plane mirror based on wedge-induced lateral-shearing interferometry (W-LSI), by separating the first-order sidebands of the reference and test beams in the Fourier domain and then reconstructing them individually, so that the quasi-absolute wavefront is obtained in one exposure. For comparison, plane-mirror measurements were performed using a temporally separated QWLSI reference/test workflow and the proposed single-shot W-LSI method. Under the present non-isolated experimental conditions, the temporally separated reference/test acquisition in the conventional workflow was strongly affected by time-varying vibration and air turbulence, whereas the proposed W-LSI result agreed well with the Zygo interferometer measurement, with peak-to-valley (PV) values of 0.238λ and 0.237λ, respectively. The proposed method avoids phase-shifting operation and provides a single-shot, in-frame reference/test measurement scheme with reduced sensitivity to time-varying disturbances, making it suitable for quasi-absolute metrology of reflective elements under practical working conditions.