High-precision 2D grating displacement measurement system based on double-spatial heterodyne optical path interleaving

We propose a high-precision 2D grating displacement measurement system based on double-spatial heterodyne optical path interleaving. The system is based on Doppler-steering interferometry of 2D gratings, heterodyne interferometry, and double-spatial element-staggered configuration. We obtain long-stroke and high-precision real-time 2D displacement information using the optical phase change and interference signal decoupling caused by the 2D grating. The system is tested experimentally and compared with a laser interferometer, and found to have a measurement resolution within 3 nm. The error within a measurement of 40 mm is better than ±175 nm and ±150 nm in the 2D grating directions. The design is then optimized and tested, and the resulting error within the 40-mm range is better than +50 nm and −40 nm in the X-direction and +100 nm and −80 nm in the Y-direction. The results show that the proposed configuration improves the accuracy of the measurement system, is suitable for engineering testing, and has the potential for further improvement.