Design of LED edge-lit light bar for automotive taillight applications

摘要

This study investigates the optical design of LED edge-lit curved light bar and applies to the design of automotive taillight. LEDs have been widely used in automotive lighting. However, the designs are mostly of direct backlight using arrays of LEDs with diffusive patterns above, which often causes problems such as low uniformity, glaring, and excess LEDs. Edge-lit light guide devices have been widely used in the back light models of LCD. However, the geometry of the lighting devices in the automotive lighting is often curved and non-rectangular, and the related literatures are very limited. This study addresses the design of edge-lit curved light bars and the optimization scheme for uniform light emitting. An automotive taillight with LED edge-lit light bar is used as an illustrated example. The light tracing software, TracePro is used to simulate the optical characteristics of the proposed design. 90° V-cuts are used as the optical features to distribute the light, and the lead angles of the V-cut are varied to achieve the optimum axial luminous intensity. A Fuzzy optimization scheme is proposed to manipulate the anchor spacing points which continuously varies the V-cut spacing along the light bar to satisfy the requirements of Society of Automotive Engineers (SAE) regulations and the illumination uniformity requirements. This study also proposes a solution to reduce the illuminance difference between the inner and the outer portions of the curved section of a light bar by varying bilaterial thickness of light bar cross section.