Methods for improving and calibrating a retroreflection defects determination system are disclosed. The retroreflection system includes a light source which directs light to an area of a surface such that the light is reflected therefrom, a retroreflective member positioned such that the reflected light...http://www.google.com.au/patents/US5074661?utm_source=gb-gplus-sharePatent US5074661 - Methods and apparatus for retroreflective surface inspection and distortion measurement
