To abandon restrictions from the multiple and irregular radiation patterns of many existing LED products, the free-form microlens optics is designed based on Snell's law and the "edge-ray principle." This secondary optics can redistribute any LED radiation onto the target surfaces to achieve prescribed uniform illuminations without concern for the initial radiation patterns of LED sources. According to practical illumination requirements, the surface shape of the single free-form microlens can be calculated by using the ray tracing method and B-spline fitting. Some modules of free-form microlens optics were constructed to achieve rectangular illumination as well as other styles of illumination. The simulation results show that the illumination achieved has high uniformities and precise illuminating shapes as prescribed. The free-form microlens optics is very applicable in LED lighting, with cogent competitive advantages.
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