Multidirectional lateral shearing random-step instantaneous phase-shifting interferometry for aspherical measurement

To further enhance measurement accuracy for aspheric surface wavefronts, a multi-directional lateral shearing instantaneous phase-shifting interferometry (MLSIPSI) method for aspheric surface testing is proposed by incorporating phase-shifting technology, and an MLSIPSI experimental system constructed. The experiment measured aspherical mirrors with asphericities of 4 and 10 µm, respectively, and compared the results with LUPHOSscan profilometer data. The system achieves RMS relative error accuracy better than λ/150, with measurement errors reduced by 27.06% and 32.05%, respectively, compared to quadriwave lateral shearing interferometry (QWLSI) baseline measurements. The experimental results verified that the validation against LUPHOScan profilometry confirmed MLSIPSI's superior precision for steep asphericity departures.