With an infrared radiator, the surface temperature of which is kept constant during measurement, a measuring area on a roughened material surface is thermally irradiated with oblique incidence of the rays. The temperature of the reflected thermal radiation is measured by an infrared thermometer, which...http://www.google.se/patents/US5352038?utm_source=gb-gplus-sharePatent US5352038 - Method of and measuring arrangement for contactless on-line measurement
