Microinterferometer

an instrument used to measure unevenness of external surfaces that have directional machining marks, and also to determine the thickness of films and the magnitude of small displacements. The first microinterferometers were developed by V. P. Linnik in 1933.

The optical scheme of a microinterferometer includes an interferometer and a microscope, which make possible simultaneous observation of the surface being studied and the interference pattern produced by two coherent light waves (a reference wave, which is reflected from a reference mirror, and a wave that is reflected from the surface being studied and is distorted by its microscopic unevenness). For monochromatic light the interference pattern consists of alternate dark and bright fringes, the shape of which reproduces a magnified profile of the portion of the surface being inspected. The height h of a surface unevenness is determined from the warping a and width b of the interference fringe: h = a/b . λ/2, where A is the average wavelength of the region of the spectrum used. Heights of 0.03 to 1 micron (JLL) can be measured.

Microinterferometers are manufactured for operation in white and monochromatic light. They are equipped with an eyepiece micrometer for making measurements or with an eyepiece and camera to record the interference pattern. Some microinterferometers have devices for measuring unevennesses up to 10 ju from impressions of the surfaces being studied.