Multi-focal Shack–Hartmann wavefront sensing with self-interference Chinese Taiji-lenslet array

Abstract

Shack–Hartmann wavefront sensor (SHWS) is a traditional method of obtaining the phase information of the incident light. As a classical method, SHWS has the merit of simple structure, good usability, real-time monitoring and wide waveband. Traditional SHWS depends mainly on a lenslet array which can split the incident wavefront and produce an array of distorted foci, which reflect the change of wavefront curvature under test. Compared to the mono-focal lenslet in SHWS, here self-interference Chinese Taiji lenslet have been introduced into the wavefront sensing in order to improve the precision of the centroid position by means of multiple foci. Wavefront sensing experiments on self-interference Taiji-lenslet array with bi- and quad-foci were sequentially carried out to verify the validity of our proposed method. More foci-splitter would bring more accuracy. Taiji lens can also be designed with amplitude modulation such as Taiji sieve, which is very suitable for wavefront measurement in the region of short wavelength, especially EUV and soft X-ray.