We present a simple freeform lens design method for an application to LED collimating illumination. The method is derived from a basic geometric-optics analysis and construction approach. By using this method, a highly collimating lens with LED chip size of 1.0 mm × 1.0 mm and optical simulation efficiency of 86.5% under a view angle of ± 5 deg is constructed. To verify the practical performance of the lens, a prototype of the collimator lens is also made, and an optical efficiency of 90.3% with a beam angle of 4.75 deg is measured.

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We present a freeform lens for application to LED uniform illumination. This lens, which is designed with a method of simple source-target luminous intensity mapping, can produce irradiance uniformity of greater than 0.8 and optical efficiency above 90% with an arbitrary half-beam angle greater than 45 deg. Typically, as compared with a conventional source-target energy mapping method, this design method can achieve better optical performance of lenses for general LED lighting. When a non-Lambertian-type light source is employed, for example, the chip on board LED, the use of the method can result in a compact LED lens without losing the optical performances of high irradiance uniformity and high optical efficiency as yielded by lenses for Lambertian-type LED light sources.

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We present a high-performance cover lens for light-emitting diode ͑LED͒ light sources to be applied to large-scale liquid crystal device television ͑LCD-TV͒ backlight modules. The cover lens with simple structure can redistribute light rays emitted from an LED light source to make the light distribution more extended so that the luminance uniformity of the backlight module can be increased. To gain a better performance, the parameters of the lens structure are optimized using a genetic algorithm. The simulation result shows that using the cover lens can achieve a luminance uniformity of 94.75% and an optical efficiency of 72.29% for a 46-in LCD-TV backlight module.