Surface Topography
Non-contact metrology techniques allow for the detailed mapping of paper surfaces without causing physical damage to the sample. Using laser profilometry, a technician can create a three-dimensional model of the peaks and valleys on a sheet of board. This method provides a more accurate view of texture than traditional air-leak tests or physical probes.
Scanning Mechanism
Measurement starts by projecting a focused light beam onto the substrate and capturing the reflected signal with a high-resolution sensor. As the laser profilometry system moves across the material, it records tiny changes in height caused by the arrangement of the fibres. These data points are then used to calculate the root mean square roughness and the average height of the surface features.
Because the laser does not touch the paper, it can measure soft or wet coatings that a physical needle would scratch. This precision allows for the detection of micro-voids that might lead to ink pinholes during the printing process. The speed of the scan allows for multiple samples to be tested in a single session.
Measurement Precision
Data gathered from these scans help mills adjust their calendering pressure to achieve a smoother finish. Since laser profilometry captures the actual geometry of the surface, it is more reliable for predicting how a varnish will flow. Consistent results depend on the stability of the scanning platform.