Wednesday, September 24, 2008
Intensive development in light-emitting diodes (LEDs) for general lighting has yet to yield the reduced energy consumption and long-life lighting necessary to replace incandescent bulbs. But for use in automotive applications, the LED has made great strides. Automotive LED Headlamps from Koito Manufacturing Co., Ltd., Tokyo, Japan, mark the first such devices fitted for low-beam use on a road vehicle, namely the 2007 Lexus LS600h/LS600hL.
Typically, white LED R&D efforts seek to maximize luminous flux (brightness per unit area), but Koito needed both high flux and high overall luminance (raw brightness). Their solution, a blue LED chip with yellow phosphor, achieves more than 200 lumens at 5 W for a two-chip version. When combined with a reflective optical system that uses a perpendicular beam shaper to direct light to the road surface, Koito was able to achieve performance surpassing high-intensity discharge units. Finally, the LED headlamp was equipped with an operational-lifetime-extending convection cooling system with no moving parts and a dynamic mechanical tracking system to aim the bank of LEDs through the curves.
Koito Manufacturing Co., Ltd., www.koito.co.jp/english