Six-degree-of-freedom displacement sensing method using a diffraction grating as a cooperative target

A novel six-degree-of-freedom displacement sensing method utilizing typical features of a diffraction grating is presented. It employs a laser source, three position sensitive detectors, a circular diffraction grating, and several optical components. Six-degree-of-freedom displacement is calculated from the coordinates of diffracted rays on the detectors. A forward and an inverse problem were solved to compute the full pose of an object through kinematic analysis. Experimental results show maximum full scale error of less than 0.5% for translation and 0.6% for rotation.