Adaptive wavefront interferometry with a wavefront sensor-less adaptive optics subsystem resolving invisible fringes iteratively for unknown free-form surfaces

The primary problem of conventional wavefront measuring interferometer is the limited dynamic range. Unknown free-form surface figure error with large amplitude or slope is not measurable for too dense or invisible fringes. To overcome this problem, we propose adaptive wavefront interferometry (AWI). AWI utilizes a wavefront sensor-less adaptive optics (AO) subsystem to intelligently speculate and compensate the unknown free-form surface figure error. In this subsystem, tunable optics is utilized to iteratively generate adaptive wavefronts to compensate the unknown large surface figure error. The tunable optics is close-loop controlled, i.e., wavefront sensor-less optimization algorithms are utilized to control the tunable optics by real time monitoring of the compensation effects to guarantee convergence of the iteration. Ultimately, invisible fringes are turned into resolvable fringes, and null test is further realized. To demonstrate the feasibility of AWI, we designed one spatial light modulator (SLM) based AWI modality as an example. Principle, simulations and experiments for the SLM based AWI are demonstrated.