A pattern of light is projected upon a surface to be measured which may be devoid of surface detail. A sharply focused image of the surface provides distance discrimination. Although the projected pattern may be separate from the imaging optics, a common optics path removes distortion, provides maximum...http://www.google.se/patents/US4629324?utm_source=gb-gplus-sharePatent US4629324 - Arrangement for measuring depth based on lens focusing
