Design and research of the LED edge lighting systems for displays

摘要

Currently, there is a tendency to minimize the lighting system of the displays of portable electronic devices. Various approaches are taken, including placing the lighting source on the edge of a display, which helps to decrease the size of the device significantly. However, edge lighting has some disadvantages, the most important of which being non-uniformity of illumination. Several methods can be applied to provide uniform illumination of displays with edge lighting. In the most modern displays, Brightness Enhancement Films (BEFs) are used together with the wedge lightguides. In the project, we consider systems for the edge lighting of relatively small displays approximately 20 × 30 mm. Only one LED with nearly lambertian spatial distribution was used in the system. The optical system consisted of a wedge lightguide and a reflective surface, the surface can be either smooth or structured (with array of certain structure). Various combinations of the wedge lightguides with the structured reflective surfaces were considered in the study, the designed variants were also compared to the systems with BEFs. The designed systems provide acceptable illuminance uniformity for the central display zone, with small dark zones on the display margins. As a result of its simple construction and the ease with which it can be manufactured, the developed system, which has only one LED source, has potential applications in situations where the requirements for illuminance uniformity are not very high, for instance, in indicator devices.