The microscopy with the use of the principles of ellipsometry. The beam of light comes out of the lamp (marked in red), then the first polarizer (green) selects an angle for linear polarization, then the 1/4 wavelength plate compensator (blue) generates the correct elliptically polarized light such that it reflects off the specimen spot linearly, then the analyzer (green) is adjusted to cross with that angle to find a minimum. As a result the specimen becomes visible as a dark spot on the white background of substrate, which reflects the light in elliptical polarization .