A polarized differential-phase laser scanning microscope, which combines a polarized optical heterodyne Mach–Zehnder interferometer and a differential amplifier to scan the topographic image of a surface, is proposed. In the experiment the differential amplifier, which acts as a PM–AM converter in the experiment, converting phase modulation (PM) into amplitude modulation (AM). Then a novel, to our knowledge, phase demodulator was proposed and implemented for the differential-phase laser scanning microscope. An optical grating (1800 lp/mm) was imaged. The lateral and the depth resolutions of the imaging system were 0.5 µm and 1 nm, respectively. The detection accuracy, which was limited by the reflectivity variation of the test surface, is discussed.
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