Industrial Nucleonics Corporation

Jon Francis Pugh

Paul Williams

A property of a thin, infrared radiation-transmissive film of plastic or the like with specular surfaces is measured with substantial freedom from errors caused by wave interference effects, utilizing first and second infrared radiations having wavelengths selected so that one of the radiations is subject to greater absorption in the film material than the other radiation. Beams of each of the radiations are directed from a multiplicity of points as on the diffusively reflective inner surface of a sphere to a surface of the film at a broad spectrum of incidence angles so that the beams traverse a multiplicity of paths through the film constituting a broad spectrum of path lengths. Radiations leaving the film are intercepted and redirected from a multiplicity of points to a surface of the film at a broad spectrum of incidence angles so that the redirected radiations also traverse a multiplicity of paths through the film constituting a broad spectrum of path lengths. Each of the first and second radiations are detected with detecting means so arranged with respect to the directing and redirecting points that detected components of each radiation are added at substantially all possible phase angles and so that the components of each of the respective radiations at each of the possible phase angles approach equality of intensity as detected by the detecting means. A response produced is indicative of the film property as a function of the ratio of the detected intensities of the first and second infrared radiations.

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Columbus, OH, United States of America

Jon Francis Pugh