Instrument determining fiber orientation in band of paper during manufacture employs infrared light source with polarization filters, achieving accurate results in any of several configurations

摘要

The source (12) passes light through the paper (10) from one side, to be received by a sensor (16) on the other. Between a source and sensor, optical units (14, 15) disperse light as a function of their polarization characteristics. An Independent claim is included for a corresponding method. Preferred features: The optical system is based on units producing and transmitting linearly-polarized light in accordance with their orientations relative to the band. At least one polarization filter (14, 15) is included and can be rotated about an axis perpendicular to the band axis. With two such units, there is one on each side of the band. They can both be on the same side, preferably between it and the sensor. Each is at a different orientation with respect to the band. Two of them (15) are symmetrical with respect to another (14) on the other side of the band. Several such filters are employed, preferably rotatable relative to each other about an axis at right angles to the band. There is just one optical unit (15) located between band and sensor (16). There is just one (14) between source and band. For each optical unit there is at least one sensor. The source emits a spectrum at a discrete and/or a continuous wavelength. The radiation is visible and/or IR light. The sensor is a spectrometer or photodiode.