Design And Performance Analysis Of Multi-focus Fresnel Lens Array

Headlamps are an important part of car’s lighting system which can improve the driving safety effectively. At present, more and more design methods of automobile headlamp are brought forth to adapt for great variety of light source. The multi-focus Fresnel lens array can be applied to the headlamp design with the collimated light source.In the present thesis, a lens array is employed to gather the lights emitted from source. The lens array is a combination of a Fresnel lens array and a deflection array in back-to-back way. The incident rays can be redirected to the target place by the lens array to yield a desired illuminance pattern.Firstly, the design method for the Fresnel lens is based on the geometrical optics laws or nonimaging optics theory. A single Fresnel lens is investigated by using some optical or design software, such as Tracepro and Solidworks. The effect on focus, which is caused by different diameter, focal length and band width, has been discussed in detail. The ideal one with small focus radius and uniform luminance is selected as the unit lens.Secondly, a honeycomb lens array which can yield the Chinese characters “工” and “大” pattern on its focal plane is carried out in this thesis. The array can be obtained by using the relation between the pattern and the focus. One side of the array lens is constituted of Fresnel lens, and the other side is a prism array. The simulation result shows that the lens array can meet the design requirement.Finally, two kinds of lens with different focal length were integrated into one array, so different pattern can be showed on the different focal plane when the parallel lights pass through the array. The optical simulation result shows that this method is feasible.