Key Technology and Solution for Speed Measurement of Auto-headlamps

EVERFINE Institute ofOptoelectronics

*Contact email address: #669Binkang Road, Hangzhou, China (tech@everfine.cn)

Abstract: Auto-headlamps should provide adequate lightingfor the driver while avoiding dazzling to otherdrivers and pedestrians. Therefore, the luminousintensity distribution of headlamps must meet the requirements of therelevant standards.

Laboratory measurement of headlamps need to be carriedout in a darkroom of at least 25m in length, the structure of goniophotometerused is complicated and a single measurement takes a long time. Although theaccuracy of laboratory measurement is super high, it does not meet the speedinspection requirements in industrial production. Especially, the opticalperformance of LED headlamps is much more variability , and it is necessary tomake a quick correction and conformity assessment in  production line.

It is well known that measurement and measurementuncertainty supplement and complement each other all the way. In the conformityassessment, great uncertainty would produce “misjudgment”. In order to avoidthe above situation, the JCGM106 issued by BIPM has put forward the concepts of“guard band” and “acceptance interval” based on thetolerance limits and measurement uncertainties, which can reduce the risk ofmisjudgment. The relevant details will be introduced in the fullpaper.

However, it is essential to rely on accuratemeasurement methods to substantially increase the confidence level of theproduction line measurement and evaluation. The exiting light distribution measurement of auto-headlamps in production line generally usesthe combination of lens and CCD camera, and laboratory measurement is used tocalibrate the production line measurement. During this process, there are manyfactors affectingthe measurement uncertainty, and the full paper will focus on analysis of the keyfactors.

In addition to optical imaging and intelligent control,the spectral matching accuracy and linearity of the imaging luminance meter(CCD camera) also are two imporatant aspects which is found to have a greatinfluence on the final light distribution assessment and intensity measurement,according to theoretical simulation analysis and actual measurement. The full paper will propose a new solution withprecious V(λ) matching and high dynamic range imaging technology(HDR) toimprove the measurement accuracyin production line. Practicalapplications also prove the effectiveness of this solution, significantlyreducing the misjudgment rate, which can improve production efficiency andproduct quality.

Keywords: Auto-headlamps;Measurement uncertainty; Conformity assessment; High dynamic range(HDR); Precious V(λ) matching