Many interference techniques have been employed for the thickness measurement of thin films. An interference technique which is inexpensive and easy to operate consists of a silvered lens placed over a stepped film with silver overlay. The resultant interference pattern when viewed in reflection is a series of sharp dark rings against a bright background, modified Newton's rings. The step in the film to be measured causes a shift in the rings from which the thickness is calculated. Step heights in silver films, vacuum deposited on fire‐polished microscope slides, of 160 and 780 Å were measured.