SYSTEM FOR ON-LINE MEASUREMENT OF COLOR, OPACITY AND REFLECTANCE OF A TRANSLUCENT MOVING WEB

摘要

Systems (10) for the on-line optical measurement of properties of a translucent moving web (12), such as paper or plastic, as it is continually produced, colored or otherwise converted. Measured properties include color, reflectance and opacity. A backing roll (22) has a cylindrical or approximately cylindrical surface (24) which comprises at least one optical standard. The roll is positioned such that a circumferential portion (26) of the roll surface contacts the back web surface (16) where the web characteristic is to be measured, with the web curving around the circumferential portion. An optical sensing device (34) is positioned so as to view the front web (14) surface backed by the optical standard or standards. In several embodiments, two sets of reflectance data are collected, one with a "white" optical standard backing and the other with a "black" optical standard backing. The backing roll surface and the optical sensing device can be arranged such that the sensing device either alternately or simultaneously views portions of the front web surface backed by each of the optical standards. In other embodiments, the backing roll has a uniform optical standard surface.