Patent DE-19912500-A1 (DE)
Title: Apparatus to monitor characteristics at a running paper web has optic fibers aligned at lateral line of measurement points to register infra red light waves to be converted into pixels at a detector for computer processing
Inventor: ISCHDONAT THOMAS
IPC: G01N21/3554
Filed: 1999-03-19
Abstract: To determine the characteristics of a running web (10), and especially a paper web in a papermaking machine, a number of measurement points (11) are illuminated simultaneously on the web (10). An optical system (15-17) separates the test surface into a number of individual pixels of the proving surface at a detector (14).  The measurement points (11) lie on a straight line at right angles to the direction (B) of web (10) travel. Electromagnetic rays in the infra red spectrum are used to illuminate the measurement points (11) and especially in a wavelength of 1.0-2.5  mu m for reflection or light transmission measurements. At least some measurement points (11) are each illuminated by an individual optic fiber (16) or by a diaphragm assembly with optics before and/or after it. The detector (14) tests the different wavelengths and/or wavelength ranges of the electromagnetic rays at the measurement points (11) in a successive time sequence and especially in periods and especially a discrete ray spectrum contained in a wavelength of 2.05  mu m, 1.94  mu m and 1.83  mu m. The wavelengths are selected by at least one filter (18) between the optical system (15-17) and the detector (14). The measurement points (11) are illuminated by point and/or strip light sources. At least some of the measurement points (11) are registered simultaneously at the detector (14) as separate pixels. One or more of the light sources and/or the optical system (15-17) are moved in relation to the web movement line (B), and preferably at right angles, with preferably a periodic movement and especially with a small amplitude against the web width. The detector (14) has a signal link to a process control unit to control and/or direct the web production. process, where the detector signals are processed. An Independent claim is included for an apparatus. to monitor the characteristics of a running paper web (10) with at least one light source to illuminate measurement points (11). It has a detector (14) to register separate pixels for each point with at least one optical system (15-17). Preferred Features: The free ends of the optic fibers (16) are as close as possible to the web (10) surface, shaped to match the detection surfaces at the detector (14), and they are composed of quartz free of water with a preferably. diameter. of 200  mu m. The detector (14) is a line detector with a strip test surface divided into pixels. The filter (18) has a number of filter elements for different wavelengths, brought into the light path between the optic fibers (16) and the detector (14) in a timed sequence, preferably. as a rotating disk with the filters round its circumference. At least the light source and the entry zone into the optical system (15-17) are combined into one measurement unit (26), which extends across the web (10) width at right angles to the direction (B) of travel, with movements at right angles to the line of web movement (B).