Two-dimensional grating line parameter calibration based on biaxial phase mapping

Two-dimensional grating is the core device of plane grating interferometer to achieve high-precision and multi-degree-of-freedom displacement measurement. The detection and calibration of its groove density and grating line orthogonality can improve the positioning accuracy of grating interferometer on the one hand, and provide feedback guidance for the fabrication of two-dimensional grating on the other hand. In this paper, a method of simultaneous calibration of two-dimensional grating groove density and grating line orthogonality by orthogonal heterodyne laser interferometer is proposed. A two-dimensional grating interferometer is built with the grating to be measured, and a biaxial laser interferometer provides a displacement reference for it. The phase mapping relationship between grating interference and laser interference is established.