High-axial-resolution, full-field optical coherence microscopy using tungsten halogen lamp and liquid-crystal-based achromatic phase shifter.

A high-axial-resolution, full-field optical coherence microscope (FFOCM) for topography and tomography applications is presented. The FFOCM is based on a polarization Linnik interference microscope equipped with a tungsten halogen lamp. The phase difference between the reference and test beams in the microscope is precisely and quickly shifted by using an achromatic liquid-crystal phase shifter (LCPS). The cross-sectional amplitude and phase maps of an interferogram are retrieved by using a three-step phase-shifting technique. The LCPS consists of three identical nematic liquid-crystal (NLC) cells sandwiched between two quarter-wave plates so that it functions as a typical quarter-half-quarter phase shifter. Instead of using high-cost NLC cells with precise thickness of half-wave retardation, a method is proposed to operate thicker NLC cells without scarifying the axial resolution. Experimental results reveal that the FFOCM is able to perform three-dimensional micrometer-resolution imaging.