Abstract: A method and apparatus for measuring the width of a strip or the widths of multiple strips being conveyed longitudinally through a sensing region of a gauge. The apparatus includes a correction bar that has very highly accurately machined edges and includes a laser point displacement sensor that traverses across the sensing region of the gauge of the invention. The method of the invention uses the correction bar by sensing its edge distance positions and using the data for the sensed edge distance positions and data for its highly accurately known edge distance positions to generate corrections for all distance positions continuously across the entire sensing region. Corrections are then made to sensed edge distance positions of a strip or strips being sensed by the gauge, regardless of the positions of the strip edges.

Abstract: The entire throat height or air gap of a laser gauge's C-frame enclosure constitutes its accurate measurement range so that any material passing at any height through the air gap will be accurately measured. The laser gauge has at least one laser and usually two lasers housed in an enclosure with at least two arms that are spaced apart for receipt of a target surface in the air gap between the arms. The gauge has a first enclosure barrier attached to a first one of the enclosure arms at a first boundary of the air gap. The first enclosure barrier is positioned away from the laser at or beyond the gauge's proximal measurement limit. A second enclosure barrier is attached to a second one of the enclosure arms at a second boundary of the air gap. The second enclosure barrier is positioned away from the laser at or nearer than the gauge's distal measurement limit.

Abstract: A laser thickness gauge has three laser displacement sensors each transmitting a laser beam onto a target web. Two sensors are spaced along the web and face one surface of the web and the third sensor faces the opposite surface. The thickness of a web that is positioned along a passline plane between the sensor is measured even when the passline plane is not perpendicular to the beams of the sensors. A data processor computes the passline angle from the distance measurements communicated from the three sensors. During setup and calibration, data representing physical characteristics of the gauge are measured and stored and during operation are processed with currently measured data to generate correction factors that are used to correct thickness measurements determined from the three laser sensors.