Fig. 1.
Schematic diagram of experimental configuration of the laser feedback interference microscope. Linearly polarized light from a low power continuous-wave helium-neon laser passes through a broadband electro-optic phase-modulator and is subsequently expanded so that the TEM00 mode fills the back aperture of a high numerical microscope objective. The modulated intensity due to laser feedback of light from the sample is monitored with a photodetector at the back mirror. A single computer controls the phase shifts to the modulator, reads the photodetector signal and controls the piezoelectric stage that moves the sample.