Interference microscopy

Abstract

Interference microscopy makes use of the fact that coherent beams of light waves that are out of phase by half a wavelength interfere destructively. Indeed, phase contrast microscopy, discussed in the previous chapter, is a special case of it. The techniques of interference microscopy enable variations in surface level to be shown by interference fringe contours or by changes in contrast. Fringe patterns, called ‘interferograms’, are analogous to contour maps and enable much more accurate quantitative deductions to be made about surface topography than is possible with opaque stop or phase contrast techniques. The principles of the methods are simple and are discussed below.