Zonal multi-shear amount fusion wavefront reconstruction for lateral shearing interferometry in aspheric surface measurement

Abstract

In lateral shearing interferometry for aspheric surface measurement, the nonuniform fringe density distribution caused by zonal curvature variations degrades wavefront reconstruction accuracy. To address this issue, this paper proposes a fused multi-shear wavefront reconstruction method for aspheric measurement. First, the test aspheric wavefront is partitioned into annular subzones based on the wavefront slope principle, while ensuring fringe resolvability at the zone edges, optimal shear amounts are matched to each zone to acquire appropriate interferograms. Specifically, a smaller shear amount is used in the high curvature zone to reduce the stripe density, and a larger shear amount is used in the low curvature zone to increase the data volume. After phase extraction and unwrapping are performed for the sheared interferograms of each annular subzone, differential Zernike polynomials are employed to independently reconstruct the wavefront for each annular subzone, and multi-shear wavefront fusion algorithm model is established to achieve full-aperture measurement through local surface. Experimental results demonstrate that this method effectively resolves the inherent limitation of conventional single-shear approaches in simultaneously measuring high and low curvature zones, significantly improves fringe pattern resolvability, and provides a viable approach for enhancing the measurement precision of aspheric surfaces.