A highly efficiency flashlight module based on modified fresnel lens

This study presents a design method of flashlight module with discontinuous refractive surfaces and total internal reflection (TIR) surfaces to achieve high optical qualities with thin lens. Our design is applied to the lens of 30mm focal length, which is generally the focal length of a mobile device. The flashlight module was constructed by optical simulation tool ASAP. We analyzed interrelation between the TIR surfaces and multiple optical qualities, such as the angle of light emitting and the uniformity of illuminance. The TIR surfaces were designed to maximize the uniformity and optical efficiency in the target viewing angle. After designing corresponding microstructures on the TIR surfaces, we can get a flashlight module of modified Fresnel lens with high optical qualities. Compared with the original LED source, the central illuminance improves to 1.5 times and the uniformity of target area improves to 1.3 times. This flashlight module can be used in products that require high quality photograph, such as cellphone, and tablet computer. The flashlight module of modified Fresnel lens is more energy-saving and carbon reduction due to optical efficiency increasing 1.7 times.