BK7 Grade A Optical Glass Corner Cube Retro Reflector

Corner Cube Retro Reflector are used to reflect light beam back to the direction that it comes from. The reflected beam is always parallel to to the incident beam, and it travels in the reverse direction of the incident beam. This hold true regardless of the angle of incident beam. The beam reflection is achieved either through total internal reflection or by mirror coating on the rear surface of the retro reflector . An Incident beam filling the effective aperture, is reflected exactly back on itself. 
The Protective Al2 coating can be given to the rear reflecting Surface to avoid total internal reflection failure at high incident Angle.