Establishment of a metric to characterize retroreflector properties using a consumer-grade colour camera

The coefficients of retroreflection and chromaticity coordinates are critical metrics for determining the quality of a retroreflector.However,conventional retroreflection measurement techniques rely heavily on the night-time colour,size and characteristics of thesample being measured.This complicates the measurement process and leads to deviations in the test results.In addition,chromaticitycannot be determined using this approach.Therefore,it is necessary to improve the measurement accuracy,simplify themeasurement process and achieve themeasurement of the traffic sign RA and chromaticity coordinates simultaneously.In this study,an improved method for retroreflector characterization using imaging was proposed.This allowed for the measurement of the coefficientsof retroreflection and the chromaticity coordinates simultaneously,and only a white standard sample was required for calibration.The primary components of the proposed system included a lighting projector,a receiver,two motorized rotational stages,a retroreflective sample holder and customized software that using scaling factors to convert a digital signal into sample retroreflectioncoefficients and retroreflective chromaticity coordinates.The experimental results indicated that the raw data output from thecamera exhibited a positive correlation relationship with the luminous flux from the surface of the retroreflector.The maximummeasurementerrors for the retroreflection and chromaticity were−12.2 cd/(lx·m2)and−2.09%,respectively.Thismethod was inexpensiveand convenient,used a commercially available digital camera,could help to identify defects in retroreflection and chromaticity forretroreflective sheeting and led to increased accessibility for the quality control of retroreflective sheeting.