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Fresnel lens is one optical device. It has the same curvature of traditional lens. But it removes unnecessary parts of lens. It is often used in optical system for its less cost, lighter mass, and smaller focal length. In this work, effect geometric parameters of Fresnel lens on imaging and focusing is investigated and discussed.
The trenches directions of Fresnel lenses would affect the focusing phenomena. Trenches outward would have better focusing effect and smaller optical aberration due to two refractions. However, trenches inward would have advantage of smaller focal length. It is found that draft angle has no significant effect on focusing and imaging. However, from simulation, the trenches direction should be considered in the design of the draft angle. For Fresnel lens design, draft angle of 5° for trenches outward and 2° for trenches inward have better performance.
By observation of light trajectory, it is found that the number of rings has less effect on illumination. But it would induce optical aberration for ring number less than 15. The ring number had better be more than 15.
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