Reflective fiducial marks, or targets, permit the location of objects relative to a robot. Usually, object luminance falls off as the inverse square of the distance from the source. However, selected retroreflective marks illuminated by a source near the sensor can have luminances which are almost constant over a wide range of distances and which are also over one hundred times greater than those of diffuse reflectors. Retroreflective materials and illuminator design guidelines are discussed.
Gordon T. Uber,
"Constant-Luminance Retroreflective Targets For Robot Guidance", Proc. SPIE 0958, Automotive Displays and Industrial Illumination, (24 October 1988); doi: 10.1117/12.947732; https://doi.org/10.1117/12.947732