Laser Line Triangulation Profilometry Principles on Continuous Paperboard Substrates
Inline blue laser triangulation measures paperboard surface topography at high speeds by overcoming fiber light penetration and isolating mechanical flutter.
Dual Head Sensor
Differential Measurement
An inline measurement configuration consisting of two opposing transceivers positioned on either side of a moving paper web provides continuous tracking of material properties. Using a dual head sensor allows for the simultaneous collection of data without contacting the delicate surface of the sheet. This setup typically measures basis weight by transmitting radiation or light from one head to the other.
By comparing the emitted signal to the received signal, the system calculates the physical density of the moving sheet.
Web Stabilization
Mechanical alignment between the top and bottom heads must be maintained to sub-micron accuracy during scan cycles. Because the dual head sensor moves back and forth across a wide paper machine, any deflection or tilt in the supporting frame will introduce measurement errors. High-precision magnetic or optical sensors are used to track the position of the heads relative to each other.
If the heads shift out of alignment, the system interprets the change as a variation in paper thickness.
Operational Benefit
Operational benefits of this non-contact approach include the elimination of sheet marking. By utilizing a continuous air cushion to maintain a precise gap, the dual head sensor avoids tearing the sheet at high speeds. This method is essential for mills producing high-quality coated fine papers.