Measurement for off-axis aspheric mirror using off-axis annular subaperture stitching interferometry: Theory and applications

An off-axis annular subaperture stitching interferometry (OASSI) is presented to test off-axis aspheric surfaces. In view of this, the relationship between misalignment and wavefront aberration is deduced with a strict theoretical analysis. The analytic result shows that the relative misalignment errors between the interferometer and the off-axis mirror tested will lead to complex wavefront aberrations in the measurement result other than the ordinary terms of piston, tilts, and power. Based on the analytic result, a suitable off-axis stitching algorithm is developed for stitching the off-axis subaperture. Both the numerical simulations and preliminary experimental results prove the potential of the proposed approach for the measurement of off-axis aspheric surfaces. As far as we know, this is the first time that OASSI has been used to test the off-axis aspheric surface.