Fast evaluation of a linear scale for a linear encoder with a Fizeau interferometer and stitching technique

In this paper, a Fizeau interferometer is used to evaluate the out-of-flatness error and the pitch deviation of a reflective-type linear scale. The out-of-flatness error of the linear scale is evaluated by analyzing the zeroth-order diffracted beam and the positive and negative first-order diffracted beams are measured to evaluate the pitch deviation of the linear scale. Basic stitching technique is also studied and simulated to connect the phase map obtained by the sub-apertures.