Measurement of aspheric and freeform surfaces remains challenging due to the various shapes of the surface under test (SUT), especially when the SUT has a large aperture and strong deviation… Click to show full abstract
Measurement of aspheric and freeform surfaces remains challenging due to the various shapes of the surface under test (SUT), especially when the SUT has a large aperture and strong deviation from the spherical surface. This paper proposes a two-step carrier-wave stitching method to enlarge the measurement bandwidth of a digital Moiré interferometry. Then, measurements of aspheric and freeform surfaces with a standard spherical interferometer without a phase-shifting mechanism are demonstrated. Experimental results with a root-mean-square repeatability of better than 1/200λ present good consistency to UA3P contact measurement results. Further simulation results with different residual wavefronts confirm measurement accuracies of peak-to-valley value of 10-3λ. The method is effective for large residual wavefronts and thus has potential for flexible measurement of aspheric and freeform surfaces.
               
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