Quantifying surface roughness-induced deviations in dimensional measurements: Comparison and compensation between chromatic confocal distance sensing and tactile probing

Chromatic confocal sensors (CCSs) offer nanometric resolution and sub-micrometric accuracy, making them increasingly valuable in industrial dimensional metrology. When CCS-based dimensional results are compared with tactile probing, surface roughness may lead to systematic optical-tactile deviations due to the different probe-surface interaction mechanisms. An extensive experimental campaign on 29 steel specimens with varied roughness (Ra from 0.0125 µm to 50 µm) produced by diverse machining processes was conducted, complemented by modelling of the probe–surface interactions using morphological filtering simulations. Results reveal that for fine surfaces (Ra < 3 µm), the optical-tactile deviation remains limited, indicating consistency between CCSs and tactile probing under the adopted measurement configuration, while on rougher surfaces, the optical-tactile deviation increased systematically, reflecting the different interaction mechanisms of the probes with surface topography. A proportional relationship between such deviations, the mean peak height roughness parameter Rp and the stylus tip diameter dtip was identified, enabling a simple compensation model to reduce the optical-tactile deviation and align CCS-based dimensional results with the tactile reference. These findings enhance the understanding of CCS metrological performance for dimensional measurements on rough surfaces, extend their applicability and comparability to tactile measurements, and support their reliable integration in advanced manufacturing applications.