Fig. 1. Schematic diagram of signal processing with EMD-LS method

Fig. 2. Laser linear reference test experiment under random disturbance of air environment

Fig. 3. Results of laser beam drift compensation

Fig. 4. EMD and time-frequency analysis results of laser collimation signal

Fig. 5. Reconstruction results of laser collimation signal

Fig. 6. Filtering results of laser collimated signals by different methods with temperature of （20±0.5） °C， pressure of 103.5 kPa±5 Pa and humidity of 50%

Fig. 7. Filtering results of laser collimation signals by different methods with temperature of （23±1） °C， pressure of 103.5 kPa ± 20 Pa and humidity of 55%