Fig. 1. Structural sketch of LED collimating lens

Fig. 2. Divergence characteristic of outgoing beams in collimating illumination system with extended source

Fig. 3. Principal plane position of a plane-convex lens in collimating illumination system with extended source

Fig. 4. Divergence of the outgoing beam in the propagation process

Fig. 5. Collimation of point source by a flat-convex lens

Fig. 6. Two-dimensional (left) and one-dimensional (right) illumination distributions of the outgoing beam on the detection plane at different distances. (a) z=200 mm; (b) z=10 m; (c) z=1 km

Fig. 7. Relationship between the divergence angle of the outgoing beam and the source size

Fig. 8. Relationship between the divergence angle of the outgoing beam and the focal length of collimating lens

Fig. 9. Relationship between the divergence angle of the outgoing beam and the aperture of collimating lens

Fig. 10. Photos of collimation lens (left) and LED with XHP50.2-type, XD16-type (right)

Fig. 11. Searchlight and its illumination spot. (a) Searchlight in lighting; (b) propagation of the outgoing beam; (c) illumination spot of the searchlight with XHP50.2-type LED at a 50 m distance