METHOD AND APPARATUS FOR ELECTROMAGNETIC DETECTION FOR USE IN THE MANUFACTURE OF FIBROUS WEB

摘要

An apparatus for measuring parameters, such as moisture content or basis weight, of a fibrous web, e.g. paper or non-wovens, comprises optical elements (52, 54, 58, 64, 66, 68) and a wavelength selection device (56) for selectively directing a beam of electromagnetic radiation comprising wavelengths in at least the mid infrared (MIR) spectral range through the web (70); an element, such as a beam stop (72), arranged in the path of electromagnetic radiation emerging from the web, for separating directly transmitted from scattered electromagnetic radiation; a collector (74) for collecting the scattered radiation; and at least one detector (78) for detecting the scattered radiation collected by the collector.