Holographic thin film analyzer

Claim 1

A thin film analyzer for determining the thickness of a film on an object comprising: A. a source of coherent light; B. a beam splitter to which a beam of light from said source of coherent light is directed for providing as an output first and second beams of coherent light; C. a photographic plate positioned for viewing said object; D. light colummating means; E. first optical means responsive to said first beam of coherent light for directing said first beam onto and over the thus illuminated area of said photographic plate; F. second optical means responsive to said second beam of coherent light for directing said second beam through said colummating means and through a first discrete area of said photographic plate onto said object from which it is reflected back to a second discrete area of said photographic plate which is within said illuminated area; G. a mirror adapted to be positioned behind a said object with respect to said photographic plate and wherein light passing through said object is reflected back through the object to a third discrete area of said photographic plate within said illuminated area and spaced from said second discrete area; H. a vacuum chamber surrounding said object; I. a source of material positioned within said vacuum chamber and including deposition means for causing said material to be deposited on the surface of said object; and J. control means acting on said deposition means for selectively controlling the deposition of material from said source of material onto a said object; whereby two successive exposures of light directed onto said object and reflected back to said photographic plate provide an indication of thickness of film deposited on said object between said exposures, the photographic plate being developed after one of said exposures.