Abstract
Low optical efficiency of light-emitting diode (LED) based headlamp is one of the most important issues to obstruct applications of LEDs in headlamp. An effective high-efficient LED headlamp freeform lens design method is introduced in this paper. A low-beam lens and a high-beam lens for LED headlamp are designed according to this method. Monte Carlo ray tracing simulation results demonstrate that the LED headlamp with these two lenses can fully comply with the ECE regulation without any other lens or reflector. Moreover, optical efficiencies of both these two lenses are more than 88% in theory.
Highlights
Since light-emitting diode (LED) have many advantages over the light sources conventionally used in automotive applications, such as good reliability, energy and space savings, non fragile, environmental friendly and long life [1], LEDs were used in dashboard lighting, interior lighting and exterior signal lighting in most recent decades
LEDs are rarely applied in headlamp, which is believed to be due to two reasons: low flux of one single LED compared with conventional one single light source and low optical efficiency of optical device
There is a baffle in the projection headlamp to obtain a sharp horizontal and 15°inclined cut-off line in the measuring screen, substantial lights radiated from LEDs are kept out by the baffle, so that the optical efficiency of this type headlamp is just about 50% [3]
Summary
Since LEDs have many advantages over the light sources conventionally used in automotive applications, such as good reliability, energy and space savings, non fragile, environmental friendly and long life [1], LEDs were used in dashboard lighting, interior lighting and exterior signal lighting in most recent decades. LEDs are rarely applied in headlamp, which is believed to be due to two reasons: low flux of one single LED compared with conventional one single light source and low optical efficiency of optical device. If the optical efficiency of optical device is low, more LEDs are needed to comply with the regulation, which will raise the electrical power consumption of headlamp greatly. Oliver Dross et al have invented an excellent approach to designing the optical device of LED headlamp based on SMS method [4]. In their design, the optical efficiencies of both low-beam and high-beam lamp are more than 75%, which are very high values so far. Both of the two lenses have optical efficiencies of more than 88%
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