HIGH-SPEED OPTICAL SCANNER FOR REFLECTANCE SPECTROSCOPY

A WEB OPTICAL SCANNER IS BEING DEVELOPED FOR ON-LINE DIFFUSE REFLECTANCE AND TRANSMITTANCE, AND SPECULAR REFLECTANCE MEASUREMENTS IN PROCESS CONTROL APPLICATIONS. A FIBER-OPTIC COUPLER WILL BE THE MODULAR COMPONENT FOR THE ON-LINE DEVICE. THIS DEVELOPMENT WILL PROVIDE THE BASIS FOR COUPLING UV/VIS/NIR ILLUMINATION TO THE WEB, AND COUPLING REFLECTANCE FROM A HIGH-DENSITY (200 PER METER) LINEAR PIXEL ARRAY TO A SINGLE DETECTOR. THE FIBEROPTIC COUPLER WILL BE INTEGRATED WITH A SHUTTER MECHANISM TO PROVIDE SERIAL READOUT IN A LINE ACROSS THE WEB. AT PIXEL DENSITIES OF 200 PER METER, THE CROSS-WEB SCAN OF COMMERCIALLY OPERATING WEBS WILL BE 100 MS FOR THE ENTIRE SHEET WIDTH. THE REFLECTANCE SCANNER WILL BE COMPACT, NONCONTACTING, AND ADAPTABLE TO A RANGE OF ILLUMINATION AND DETECTION ANGLES. THE WEB SCANNER PROVIDES THE MEANS FOR MEASURING HIGH RESOLUTION (1 MM) CROSS-DIRECTIONAL PROFILES OF SHEET CONSTITUENT CONCENTRATIONS AND MACHINE-DIRECTION CONCENTRATION VARIATIONS. REFLECTANCE/TRANSMITTANCE SPECTROSCOPY IS THE BASIS FOR COATWEIGHT MEAN AND VARIANCE PROFILE MEASUREMENTS IN ADDITION TO THE FUNDAMENTALLY SIMILAR DETERMINATIONS FOR GLOSS, MOISTURE, BINDER CONCENTRATION, COLOR, FLUORESCENCE FACTORS, ETC. DURING PHASE I, APPLICATIONS OF REFLECTANCE SPECTROSCOPY TO COMMERCIALLY IMPORTANT MIXTURES WILL BE INVESTIGATED UTILIZING THE FIBEROPTIC COUPLER. THESE INVESTIGATIONS WILL FOCUS ON UV SPECTRA REFLECTANCE NORMALIZATION FOR WEB GLOSS AND MOISTURE DIFFERENCES. IN REGARD TO COATWEIGHT MEASUREMENT, THE PROPOSED SCANNER TECHNOLOGY PROVIDES SIGNIFICANT ADVANTAGES OVER TRAVERSING, BETA-RAY MEASUREMENTS USING RADIOISOTOPES WHICH ARE WIDELY APPLIED IN MANUFACTURING TECHNOLOGY. GLOSS STREAK AND BASIS WEIGHT STREAK DETECTION WITH A RESOLUTION OF 1 MM IS ANOTHER EXAMPLE OF THE UTILITY OF THIS SCANNER FOR THE PAPER INDUSTRY.