High Quality Content by WIKIPEDIA articles! A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects light back to its source with a minimum scattering of light. An electromagnetic wave front is reflected back along a vector that is parallel to but opposite in direction from the wave`s source. The device or surface`s angle of incidence is greater than zero. This is unlike a planar mirror, which does this only if the mirror is exactly perpendicular to the wave front, having a zero angle of incidence.