Fig. 1. Principle block diagram of laser tracking measurement system

Fig. 2. (a) Center of laser beam at the center of four quadrant detector; (b) center of laser beam deviates from the center of four quadrant detector

Fig. 3. Block diagram of laser tracking control system

Fig. 4. Flow chart of PID servo regulation

Fig. 5. Schematic diagram of tracking control

Fig. 6. Experimental graph of spot offset measurement

Fig. 7. Line chart of measurement errors of spot offset

Fig. 8. Experimental device of tracking measurement

Fig. 9. Line chart of tracking measurement experimental data