Orthogonal crossed gratings, or two-dimensional (2D) gratings are key optical elements in plane optical encoders. In this paper, Scanning Dammann lithography (SDL) was implemented to fabricate gold-coated 2D gratings by stepping and scanning a 2D air-bearing stage and rotating Dammann gratings. A displacement measurement interferometer (DMI) was applied to monitor the 2D stage which ensured the positioning accuracy of exposing. A series of experiments by varying the exposure dose were conducted. The atomic force microscope (AFM) results indicted the duty cycle changed with the exposure dose. A 2D gold-coated grating with a size 100*100mm was also fabricated. Since it is straightforward to extend the size of the substrate up to hundreds of millimeters, SDL is a promising method to fabricate large-sized 2D gratings with controllable duty cycle.
In this paper, we propose a high-density grating interferometry system, which can be applied to measure displacement on the nanometer precision. We make use of the optical subdivision module to improve the measurement resolution which is better than the traditional one. The core part of the whole system is a grating with high-density of 1780 lines/mm and long-range of 100mm*100mm. The apparatus adopts a symmetrical structure to reduce the error resulting from environmental disturbance. The system provides a novel measurement technique to improve the grating interferometry. The experimental results show that the grating interferometer system has good stability, and the in-situ measurement error is within ±5 nm for a long time. The grating interferometer can measure the short distance displacement of 30 nm and can control the error within ±2 nm. The measurement of the distance of 10 mm can control the error within ±20 nm. The results proves the feasibility of our proposed improved.