Compact high-precision heterodyne interferometer with equal optical path and common light path quadruple doppler shifts

• “Compact”: This measurement device is more suitable for miniaturization in terms of size. • “High-Precision”: The influence of the interleaving configuration on the optical path change is analyzed. • “High Precision”: The influence of vibration of displacement stage and optical path variation on optical system error is analyzed, and eight times optical subdivision is used to improve measurement accuracy. • “Equal Optical Path and Common Light Path”: The optical path consistency of measurement arm and reference arm (temperature, humidity and other environments are consistent) is clarified, and the position characteristics and polarization characteristics of spatial incident light are effectively utilized to ensure the same interference signal amplitude and obtain high signal-to-noise ratio. The energy utilization rate and measurement accuracy of the measurement system are improved by using anti-reflection film and QWP polarization characteristics. • “Quadruple Doppler Shifts”: Eight times optical subdivision is obtained by four incidence to achieve the purpose of Quadruple Doppler Shift, it is equivalent to the laser displacement being magnified eight times synchronously to improve the measurement accuracy. In addition, four laser incident points on the measurement mirror can realize accurate positioning of the measurement mirror in space. Laser displacement measurement systems are extensively utilized in ultra-precision five-axis linkage machines for nanometer-scale displacement control and in high-end lithography machine for sub-nanometer high-speed workpiece stage positioning. However, the current laser displacement measurement system has a limitation, that is, the real-time displacement measurement accuracy is limited to the optical subdivision multiple and the mirror group size, which makes it difficult for compact measurement accuracy to reach the sub-nanometer level. Based on this, we propose a compact high-precision heterodyne interferometer with equal optical path and common light path quadruple doppler shifts, which achieves high-precision displacement measurement with eight times optical subdivision accuracy by four doppler frequency shifts. The results show that the theoretical resolution of the 110 × 85 × 50 mm 3 laser displacement measurement device is better than 0.077 nm, the linear displacement measuring error at 200 μm is better than ± 5 nm, and the actual step measuring error of 10 nm is better than ±1 nm. Therefore, the laser displacement measurement device has the measurement potential of high stability, high measurement accuracy and high reliability in the field of high-end equipment.