Comparing laser and polychromatic confocal optical displacement sensors for the 3D measurement of cylindrical artefacts containing microscopic grooved structures

A scanning system has been developed for measuring the surface of early cylinder mechanical sound recordings to high precision, both for surface preservation and for post-processing of the data to recover the sound encoded in the grooves. Research has identified that high sensor axial resolution is required to resolve the smallest amplitude groove modulations contained on typical cylinder artefacts resulting in the selection of confocal laser and white light (polychromatic) confocal sensors as suitable sensing technologies. This paper presents data acquired by the two confocal sensor technologies, comparing the measured surface profiles with data obtained using a stylus profilometer. We investigate limitations of the sensors, relating their characteristics to the ongoing development of the scanning system.