Heterodyne interference microscopy for non-invasive cell morphometry

摘要

This paper describes two setups suitable for interference microscopy for high resolution morphological measurements on living cells in culture medium. The first system incorporated a PZT actuator in the reference path of a Mach Zehnder configuration to facilitate digital phase-stepping interferometry. The second system employed two phase-locked acousto-optic modulators to generate a temporal optical carrier to allow a heterodyne approach to phase demodulation. This setup incorporated a digital CMOS camera with full random pixel access which allowed the heterodyne approach to be implemented as a full-field method without any need for electromechanical scanning. The heterodyne approach offers benefits over the phase-stepping method in terms of measurement resolution and speed, typically offering the equivalent of nanometer resolution for cell height measurements with a bandwidth in the order of 200-300 Hz for 1000 pixels. Results for morphological measurements using both systems on red blood cells and keratinocytes are presented.