Fig. 1. Relationship between CNR measured by the system and the radius of probe beam on the target

Fig. 2. Structure of optical transformation system

Fig. 3. Simulation results of optical transformation system using the parameters in Table 1

Fig. 4. When the L₀, f₂and Δ is fixed, the variation of L and ω. (a) Relationship among L, ω₀and f₁; (b) relationship among ω, ω₀and f₁

Fig. 5. Simulation results of optical transformation system using the parameters in Table 3. (a) Relationship between L and Δ; (b) relationship between ω and Δ

Fig. 6. Experimental system of LDV. (a) Structure of LDV probe; (b) experimental system using the parameters in Table 2; (c) experimental system using the parameters in Table 3

Fig. 7. Measured velocity and Doppler signal quality factor curves of systems with different parameters. (a) Velocity measured by system in Fig. 6(b); (b) quality factor measured by system in Fig. 6(b); (c) velocity measured by system in Fig. 6(c); (d) quality factor measured by system in Fig. 6(c)

Fig. 8. Spot diameter (D) at the working distance of 50 m for different systems. (a) System in Fig. 6(b); (b) system in Fig. 6(c)

Fig. 9. Structure of LDV prototype

Fig. 10. Depth of field of LDV

Fig. 11. Diagram of the installation of attitude sensor on LDV

Fig. 12. Pictures of field campaign. (a)Diagram of airborne LDV; (b) reflector

Fig. 13. Statuses of UAV. (a) Hovering; (b) moving forward

Fig. 14. Data of flight test. (a) Pitch angle variation of the UAV measured by MEMS attitude sensor during flight; (b) comparison among V_GPS, V_LDV and V_LDV with pitch angle correction; (c) diagram of the height variation of UAV during flight; (d) quality factor variation during flight

Fig. 15. Airborne LDV with two probe beams. (a) Hovering; (b) moving forward