Design of an Ultra Thin Secondary Lens for Visible Light Communication Based on a White LED

Light-emitting diodes (LEDs) have begun to penetrate the traditional lighting industry and have left a profound impact on the illumination of thin and portable personnel telecommunication devices. Aside from this, LEDs can also be used in the design of visible optical wireless communication systems. In lighting applications, Surface Mount Device (SMD) LEDs play an important role; however, their low light flux brought about by the large viewing angle should be redistributed to increase luminescence and the communication range in communication applications. For this reason, the current study issue in this application is how to achieve a long data transmission range while dramatically reducing the overall system size for use in thin electronic products. This work presents a proposed design of an ultra-thin secondary lens for visible light communication based on white LEDs. The accurate physical modeling of a chip die and its package can make ray-trace simulation a powerful tool in predicting power distribution of the SMD LEDs in the near-field. To verify the proposed method, modeled ray data was compared with measured data. While relaxing several design constraints, the secondary light colliminator was carried out with a solution of a central refractive aspheric surface and an outer reflective surface. The optical performance of the modeled LEDs was very similar to the real one. The designed lens reduced the viewing angle of white SMD LEDs from 120 degrees to 20 degrees in FWHM. The proposed lens is extremely compact and efficient and is a good starting point in achieving an effective design of visible light communication between personnel telecommunication devices.