Fig. 1. Schematic diagram of direct laser triangulation ranging

Fig. 2. Influence of working distance a when α=π/6 and f=25 mm

Fig. 3. Influence of angle α when a=300 mm and f=25 mm

Fig. 4. Influence of focal length f when a=300 mm and α=π/6

Fig. 5. Device structure diagram after placing planar mirror

Fig. 6. Flow chart of gravitational search algorithm

Fig. 7. Algorithm iteration procedure

Fig. 8. Target S_max/S_min changes with the number of iterations

Fig. 9. Comparison of three structures