Measurement of aspherical optical elements using multi-plane phase retrieval combined with varying-curvature illumination

Aspherical optical elements have been widely used in modern optical systems, and the advanced measurement techniques are required to ensure the accurate characterization and quality control. A multi-plane phase retrieval method combined with varying-curvature illumination is presented, which greatly improves the convergence speed and reconstruction accuracy. The corresponding reconstruction algorithms and update methods are designed respectively for the reflective elements and the transmissive elements according to the optical path characteristics of different elements. This method was applied to the digital knife-edge instrument to achieve quantitative measurement. The PV deviations of the large-aperture transmissive and reflective elements from interferometer are both less than 30 nm. It provides a simple, low-cost and high-precision measurement tool for aspheric optical elements and has strong scalability.