The low beam headlamp is characterized by a complex light distribution. The metrological requirements are much more demanding than those of other headlamp light distributions. The paper gives an overview over the luminance measuring procedures based on image-processing, which, in certain fields of photometry, are accepted as alternatives to photogoniometers. However, until now the application of this methods to headlamps has not been possible, because the high contrast ratios in the low beam light distributions are a source of large errors due to scattered light (frequently over 200% of the real measured value). In the context of an extensive research work, possibilities have been created and basic conditions have been defined primarily aiming at reducing scattered light in order to allow the application of these methods in case of headlamps. After the analysis of the origins and composition of the scattered light, different reducing strategies are discussed in the paper. An autonomous scattered light correction model was developed, capable of correcting different inputs independently of position and intensity. The final algorithm can be divided into a calibrating and an operating phase. The purpose of the calibration phase is to determine the parameters needed for the light correction. In the operating phase the software performs the scattered light correction on the initial picture loaded with scattered light, directly during image recording. With the future realization of an automatic identification routine the fine adjustment of the light distribution would become redundant. Such systems could find an application in the quality control in the manufacture of headlamps.
Spatially resolved luminance measuring methods compared with illuminance measurements of automotive headlamps
Bildauflösende Messmethoden der Luminanz und Messung der Beleuchtungsstärke von Fahrzeugscheinwerfern
2005
12 Seiten, 6 Bilder, 4 Quellen
Aufsatz (Konferenz)
Englisch
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