Fig. 1. Physical model of LED. (a) Exterior photograph of LED; (b) interior structure model of lens

Fig. 2. Optical experimental device

Fig. 3. Comparison between experimental and calculation results (a) and thermal infrared images (b)

Fig. 4. Variation of surface temperature of lens with x. (a) Inner surface; (b) external surface

Fig. 5. Variation of surface temperature of lens with t. (a) Inner surface; (b) external surface

Fig. 6. Variation of central temperature of lens inner surface with ε

Fig. 7. Variation of thermal stress of lens with x

Fig. 8. Variation of total displacement of lens with x

Fig. 9. Variations of maximum thermal stress and maximum total displacement with α