Fig. 1. Schematic of beam drifts caused by environmental factors. (a) Parallel drift model; (b) angular drift model

Fig. 2. Measurement principle of beam drift caused by air disturbance

Fig. 3. Spectral characteristics of beam drift caused by air disturbance. (a) Signal power spectrum; (b) signal processing result

Fig. 4. Measurement principle of two-dimensional displacement with laser beam drift compensation

Fig. 5. Optical path for differential compensation

Fig. 6. Result of angular drift compensation by differential structure

Fig. 7. Compensation effect of total drift by differential structure

Fig. 8. Common path compensation structure

Fig. 9. Compensation effect of angular drift by common path structure