title: Reference-free Shack-Hartmann wavefront sensor.
abstract: The traditional Shack-Hartmann wavefront sensing (SHWS) system measures the wavefront slope by calculating the centroid shift between the sample and a reference piece, and then the wavefront is reconstructed by a suitable iterative reconstruction method. Because of the necessity of a reference, many issues are brought up, which limit the system in most applications. This Letter proposes a reference-free wavefront sensing (RFWS) methodology, and an RFWS system is built up where wavefront slope changes are measured by introducing a lateral disturbance to the sampling aperture. By using Southwell reconstruction two times to process the measured data, the form of the wavefront at the sampling plane can be well reconstructed. A theoretical simulation platform of RFWS is established, and various surface forms are investigated. Practical measurements with two measurement systems-SHWS and our RFWS-are conducted, analyzed, and compared. All the simulation and measurement results prove and demonstrate the correctness and effectiveness of the method.
authors.affiliation: Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075, Singapore.
authors.forename: Liping
authors.initials: L
authors.lastname: Zhao
authors.forename: Wenjiang
authors.initials: W
authors.lastname: Guo
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.forename: I-Ming
authors.initials: IM
authors.lastname: Chen