Polarization wavefront shaping for quantitative phase contrast imaging by axially-offset differential interference contrast (ADIC) microscopy

摘要

Axially-offset differential interference contrast (ADIC) microscopy was developed for quantitative phase contrastimaging (QPI) by using polarization wavefront shaping approach with a matched pair of micro-retarder arrays. In ADICmicroscopy, wavefront shaping with a micro-retarder array (μRA) produces a pattern of half-wave retardance varyingspatially in the azimuthal orientation of the fast-axis. For a linearly polarized input beam, the polarization patterninduced from the linearly polarized plane wave through the μRA is identical to the interference between a slightlydiverging right circularly polarized (RCP) and a slightly converging left circularly polarized (LCP) plane wave. Using a10× objective, two axially offset foci separated by 70 μm are consequently generated from the patterned wavefront withorthogonal polarization states, serving as the sample and reference focal planes respectively for QPI. A paired μRA intransmission coherently recombines the two orthogonal components to recover the incident polarization state in theabsence of sample. The large spatial offset (roughly 1/10 of the field of view) between the two foci provides a stable anduniform reference. Quantitative phase contrast images are directly recovered from sample-scan measurements with asingle-channel detector and lock-in amplification with fast polarization modulation. This method has been successfullyused for bio-sample imaging, nanoparticle detection and refractive index calculation of silica microbeads.