Latest Standard and Measurement Technologies on The Spatial Color Nonuniformity of LED Auto Lamps

YanHuang  Zhijun Guo  Qian Li Jiangen Pan

EVERFINEInstitute of Optoelectronics   tech@everfine.cn

Abstract

LED is firstly applied inthe daytime running lamps, brake lamps and width lamps etc. of auto vehicles.During 2007-2008, the LED headlamps, overcoming the key issues on the design ofluminaire system, gradually appeared in luxury autos, such as Lexus LS600h /LS600hl, Audi R8 and Benz CLS. With the unique features, e.g. high qualitylight, extremely low consumption and free design, LED headlamps have deeplyattracted more and more attentions from many auto manufactures. In recentyears, they have been applied in many mainstream automobiles in the globalmarket, which brings forward a new era with whole LED lighting for automobiles.

The LED headlamps, like eyes of autos, play animportant role on the driving safety. But their light emitting mechanisms andstructures are much different from the traditional lamps, such as halogentungsten lamps and HID lamps. Their performance evaluation and the relevantmeasurement technologies have been the focus recently, especially the spatialcolor nonuniformity which more likely happens to LED headlamps.

The LED headlamps always consist of many LEDs as lightsources, which are particularly designed to meet the light distributionrequirements of relevant standards. The spatial color distribution of LEDheadlamp is affected by multiple factors, including the spatial colornonuniformity of single LEDs and the color nonconsistency of different LEDscaused by inappropriate color binning etc.. Besides, the color performance ofLEDs also depends on temperature. If the thermal design can not ensure theuniform thermal environment for operated LEDs, the color nonuniformity will beworse, which can not realize the designed light pattern, and even endanger thedriving safety.

The spatial color nonuniformity also happens to otherLED lamps/luminaires, which obtains wide attentions from CIE and IESstandardization bodies etc. The relevant standards are increasingly developedor published in recent years. This paper will introduce the standardrequirements on LED spatial color distribution, and analyze the latest progresson the measurement technologies. The measurement solutions appropriate tovarious LED auto lamps will be provided with detailed application examples andmeasured data.

Keywords:LED headlamps, spatial color nonuniformity, relevant standards, measurementsolutions.