Abstract: A measuring apparatus is provided having an illumination unit including a source of electromagnetic radiation, fiber optic apparatus and sensing apparatus. The fiber optic apparatus includes first fiber optic structure having an input end for receiving at least a portion of electromagnetic radiation emitted from the radiation source and an output end for directing the received radiation to a web of material, and second fiber optic structure having an input end for receiving radiation reflected from the web of material and an output end for directing the reflected radiation to the sensing apparatus. The sensing apparatus includes a first detector for sensing electromagnetic radiation of a first wavelength band and generating a corresponding first output signal and a second detector for sensing electromagnetic radiation of a second wavelength band and generating a corresponding second output signal indicative of a first property to be measured of the web of material.

Abstract: A single vane shutter flag is asynchronously controlled so that a measuring system light source is interrupted for a minimum necessary amount of time for standardization/calibration and normalization of InGaAs system detectors. Source/detector hemispheres or serially connected randomly oriented fiber bundles homogenize light passing to the detectors. Light source testing is performed by measuring spectral power distributions at a plurality of light source power levels and comparing the measurements to baseline characteristics established for the light source. Calibration sample life is extended indefinitely by controlling the shutter flag to block source light except for short calibration time periods during which standard light levels are provided.

Abstract: A single vane shutter flag is asynchronously controlled so that a measuring system light source is interrupted for a minimum necessary amount of time for standardization/calibration and normalization of InGaAs system detectors. Source/detector hemispheres or serially connected randomly oriented fiber bundles homogenize light passing to the detectors. Light source testing is performed by measuring spectral power distributions at a plurality of light source power levels and comparing the measurements to baseline characteristics established for the light source. Calibration sample life is extended indefinitely by controlling the shutter flag to block source light except for short calibration time periods during which standard light levels are provided.