What is the difference between a reflectometer and an interferometer?
An interferometer is a device for measuring very small changes in thickness, a reflectometer measures changes in reflectance. We sell a reflectometer which measures changes in reflected light intensity, the changes are due to the thin film causing interference fringes; the thin film is the interferometer. The Reflectometer. In its simplest form a reflectometer consists of a laser, a beam-splitter and a photo-detector arranged as shown below; Provided the thin film that is being deposited is transparent at the wavelength of the laser, then the incident laser beam will undergo multiple reflections at the thin film / substrate interface and the thin film surface as shown below; In effect, the thin film is itself acting as an interferometer. These reflected rays will interfere constructively (bright fringe) or destructively (dim fringe) depending on the thickness d(t) of the thin film.
