Single-shot 3×3 beam grating interferometry for self-imaging free extended range wave front sensing

Abstract

Crossed grating 3×3 beam lateral shear interferometry for extended range wave front sensing is presented. A Fresnel diffraction pattern of two multiplicatively superimposed linear diffraction gratings each generating three diffraction orders is recorded. A simple solution employs a common crossed binary amplitude Ronchi grating with spatial filtering. Digital processing of a single-shot pattern includes separating multidirectional pairs of orthogonal lateral shear interferograms, retrieving second harmonics of their intensity distribution, and calculating shearing phases. Single-frame automatic fringe pattern processing based on the Hilbert-Huang transform is used for this purpose. Using second harmonics extends the aberration measurement range since they encode self-imaging free two-beam interferograms without contrast modulations. Experimental works corroborate the principle and capabilities of the proposed approach.

Grating-based common-path quantitative phase microscopy in low photon budget regime

“…In the CMOS sensor area, the object "negative" -1 replica then interferes with the object-free "positive" +1 replica. Processing the second harmonic simplifies phase demodulation, as demonstrated in our prior work [25,26]. The second harmonic is achromatic (wavelength-independent), with double the interference fringe spatial frequency as the first harmonic [23,24].…”