Analysis of tolerances in a grating interferometer for high-resolution displacement measurement

A grating interferometer for high-resolution displacement measurements is analyzed. To decrease interferometer sensitivity to inaccuracy of the grating guide, a laser diode beam is focused on the grating surface. The effect of the interferometer geometry on the direction and period of the fringes is analyzed. In addition, the influence of the system geometry on the optical path difference is evaluated. Methods of adjustment of the fringe direction and period and also the zero value of the optical path difference in the interferometer are proposed. The theoretical analysis is verified experimentally by analyzing separately the influence of selected geometrical parameters on fringe direction and fringe constant. The experimental results are compared with regression models obtained by theoretical analysis. More than 92% results variability is caused by the theoretically predicted model of functions.