... Plumb Level, Surveying, Alignment, Optical Tooling, Range finding, Distance finding, Distance measurement, Optical signal dispose, Optical signal process, Laser interferometer, ... the angle of incidence. These prisms have 3 mirror surfaces making angles of 90 degrees to each other ... matter the orientation of the Retroreflection Prism. Unlike an Optical Mirror, which needs to be at the normal angle ...