Patent ID: 9176057
Filing Date: 2015-11-03
Classification: G01N

Abstract:
1. An apparatus for measuring retroreflectivity of a surface, the apparatus comprising: a light source for illuminating an area of said surface at an incident angle relative to the surface; a detector for detecting light reflected back from an observation area of the surface at an observation angle relative to the surface; a signal processing unit adapted to receive a detector signal from the detector and to determine, from at least the received detector signal, a measure of the retroreflectivity of at least a part of the surface; at least one device for measuring a distance between the apparatus and the illuminated area, the device for measuring a distance between the apparatus and the illuminated area comprising the light source, the detector and the signal processing unit; wherein the signal processing unit is further adapted to adjust the measure of the retroreflectivity responsive to the measured distance; characterised in that the detector comprises a position-sensitive detector for detecting light as a function of a position within a light receiving area of the detector, wherein the signal processing unit is adapted to determine the distance from a position within the light receiving area of the detected light reflected back from the surface.