To understand our world, it is essential to know the laws of nature. Over centuries these laws have been deduced from measurements, but there are still a lot of open question. One of these open questions is the exact measurement of profiles under very clean conditions, which is hereby solved. This book describes in detail the design, construction and implementation of an optical profilometer which can measure complex surface profiles under ultra high vacuum conditions. The surface profile (in vacuum) is obtained by scanning an optical sensor across a viewport. The instrument was designed with...