Absolute angle measurement using dual-wavelength laser speckle for robotic manufacturing

摘要

A non-contact optical technique employing dual-wavelength laser speckle is investigated for absolute angle mea-surement. The approach uses the separation of the speckle patterns formed by two closely spaced illuminationwavelengths to determine the angle of a surface. Autocorrelation is performed on a single exposure containingboth speckle patterns to find their relative displacement, which is directly related to the absolute surface angle.This absolute angle determination offers an advantage over previous techniques using laser speckle that requirea reference image. The underlying theory linking the speckle pattern displacement and the surface angle ispresented, along with a proof-of-concept sensor. Experimental results from the sensor confirm the validity ofthe theory, with measurements demonstrating a mean difference from applied angles of 0.136°.