Interferometry in Microscopy

Abstract

In this chapter we are concerned essentially with two whole microscopical beams (rather than individual rays) which are caused deliberately to interfere with each other. The graphic result is a pattern of interference fringes analogous to Newton’s rings.⁽¹⁾ With incident white light, the fringes are those of Newton’s series of color bands more or less superimposed on the pictorial image. Figure 10.1, for example, shows three different micrographs of the same surface area of crystalline grains.⁽²⁾ All three micrographs were taken on the same simple microscopical interferometer shown schematically in Figure 10.2. Micrograph (a) in Figure 10.1 was taken with practically no tilting angle α to the reference surface (4 in Figure 10.2); hence there was practically no interference. Incidentally, the reference beam was sufficiently out of phase with the specimen’s beam to produce interference contrast. Thus interference microscopy is related to phase-amplitude contrast (Chapter 9).