Bidirectional two-degree-of-freedom grating interferometer with biased Littrow configuration

Traditional grating interferometer with Littrow configuration suffer from low optical subdivision factor and high grating base surface shape error. To solve these problems, a grating interferometer with bidirectional Littrow configuration is proposed. Using a high linear density grating of 1800 gr/mm with quadruple optical subdivision is achieved on the optical path. A three-dimensional contour analysis method is proposed to calculate the influence of surface shape error. The experimental result shows that the error of the 10 mm/2 mm displacement test in the X/Z direction fluctuates in the range of +/- 25 nm, and the actual resolution in the X and Z direction is all 1.5 nm. In summary, the system has good repeatability and high resolution, and can achieve nanoscale displacement measurement in the X/Z direction, and has broad application prospects in the field of precision machining and manufacturing.