GHOST IMAGE EXTINCTION IN AN ACTIVE RANGE SENSOR

An apparatus is provided that includes a plate beamsplitter having a first surface coated with a partially reflective coating, and a second surface coated with an anti-reflective coating, and a polarizing filter, oriented with respect to the plate beamsplitter so as to substantially block light of substantially incompatible polarization that has traversed the plate beamsplitter, has been reflected by the object to be range imaged, and has been reflected by the plate beamsplitter towards the polarizing filter, thereby substantially preventing the formation of a ghost image of the object to be range imaged. Thus, the invention does not suffer from optical ghost images which commonly occur due to imperfect anti-reflection coatings used to make plate beam splitters. Also, the invention makes practical the use of plate beam splitters in depth from defocus and depth from focus range imaging systems employing coaxial active illumination and viewing.