Dynamic Pass Line Vibration Cancellation in Laser Thickness Gauging Systems
Dynamic pass line vibration cancellation restores laser caliper gauge resolution down to sub-micron accuracy by eliminating phase-lag z-axis position errors.
Laser Thickness Gauge
Measurement Instrument
Precision measurement of a moving substrate occurs when optical triangulation sensors determine the distance between two light beams. A laser thickness gauge replaces traditional mechanical shoes that touch the paper, allowing for high speed monitoring without the risk of marking the sheet. This technology provides a continuous stream of data that is used to control the calender nips and ensure a uniform profile.
Optical Mechanism
The system typically consists of two sensor heads positioned on opposite sides of the web that project a beam onto the surface. By calculating the exact position of the reflected light, the laser thickness gauge derives the total distance between the heads and subtracts the empty space to find the board thickness. Digital filters remove the effects of pass line vibration and surface roughness to provide a stable reading that matches laboratory standards.
Process Integration
Installing these gauges at the end of a paper machine allows for immediate feedback into the automation system. This rapid response time enables the production of grades with very tight specifications for high end packaging. Unlike contact sensors, these optical units can operate in harsh environments with high temperatures and dust without losing accuracy or requiring frequent cleaning.
Reliability remains high even in the presence of steam or flying debris during a break.