Apparatus for determining the thickness, moisture content or other parameter of a film or coating.

摘要

The apparatus employs two or more beams of radiation of different spectral composition which are transmitted through a sample (3) and received by a detector (8) which provides signals for computing the required parameter by ration measurements. The beams are directed to a sample zone where a part is transmitted through, and a part is reflected by a sample (3). The invention provides diffusing means (7) to receive the transmitted and reflected parts and pass the same onto a radiation responsive detector (8). The diffusing means (7) may be a ground glass plate or a member made of fused alumina. A concave mirror (9) may be used to reflect the reflected part back through the sample zone which is close to or at the centre of curvature of the mirror: A beamsplitter (12) may also be used so that the beams are directed substantially normal to a plane in the sample zone.