Optimization of an optical film for highly collimating the emerging light

This paper proposes an approach for optimizing an optical collimation film with duplex microstructures to access the more collimated light. In the optimization, the lenticular lens on the upper surface of the optical film was replaced with an elliptical cylindrical lens that can eliminate spherical aberration and induce the light emerging from its focus to become a completely collimated beam. Moreover, the microstructure on the lower surface of the optical film was replaced by a multisloped asymmetric microstructure to induce the incident light to concentrate on the region closer to the focus of the upper elliptical cylindrical lens and to be reflected by total internal reflection; then the reflected light became a more collimated beam through the upper elliptical cylindrical lens. All of the related parameters were optimized and determined by performing simulations in a series of optimization processes. In addition, the optimization was implemented for two types of reflector: white and specular reflectors. Compared with the collimation film without being optimized, the light emerging from the optimized collimation film is more collimated and exhibits a higher intensity peak. The full widths at half maximum of the transverse angular distribution of the emerging light for the both conditions with the white and specular reflectors are further reduced by 25% and 38%, respectively, and the intensity peaks increase by 32% and 50.2%, respectively. Compared with the general inverted-prism film, the intensity peaks of the optimized collimation film for the both conditions considerably increase by 99.1% and 139.7%, respectively. Furthermore, the optimized collimation film has an optimal optical efficiency that is greater than 90%.