Adjustment recommendations of a conoscopic holography sensor for a reliable scanning of surfaces with roughness grades obtained by different processes

• Analysis of a conoscopic holography sensor for scanning in a CMM.
• Tests performed for surfaces with roughness grades obtained by different processes.
• Quality indicators used: number of scanned points, flatness deviation.
• Work reveals that outliers filtering improves significantly the flatness indicator.
• Adjustment parameters are proposed for a reliable surface digitizing.

Conoscopic holography (CH) is a non-contact interferometric technique used in surface digitizing. Like other laser techniques it is influenced by different factors such as surface reflectance, material, colour or even speckle noise caused by roughness. In this work, a CH system was used for analysing the influence of roughness on surface digitizing. For this purpose, several digitizing tests were performed on roughness specimens corresponding to EDM, face milling and flat grinding processes. Each roughness grade was digitized under different combinations of the sensor setting parameters (frequency F and power P) which satisfy that the signal acquired by the sensor lies within the quality values recommended by the manufacturer. The results were analysed by using two indicators that show quality of the points captured by the sensor regarding the surface geometrical reconstruction and its metrological reliability. Finally, the study provides a series of recommendations for adjusting the sensor in order to satisfy both indicators simultaneously.