A Novel Technique for Increasing Concentration Ratio and Uniformity of Fresnel Lens

In this paper, we propose a technique using the conservation of optical path length and edge ray theorem to design a Fresnel lens, which can achieve high concentration ratio, high uniform irradiance, and small f-number. The structure of the Fresnel lens consists of three parts: Inner part, middle part, and outer part. The design process is carried out by solving the equations of the conservation of optical path length in Matlab
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program. In addition, a wide range of wavelengths is applied to do rays tracing so that the system becomes more suitable in real conditions. In this technique, the Fresnel lens is constructed by many grooves that are built by the ideal Cartesian oval surface. Thus, the optical efficiency of the designed lens is improved. The simulation results by LightTools
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software show that the Fresnel lens has good optical properties such as a high concentration ratio of 900x, f-number = 0.46, high uniform irradiance distribution, and optical efficiency larger than 85%.