A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects light back to its source with a minimum of scattering. An electromagnetic wave front is reflected back along a vector that is parallel to but opposite in direction from the wave's source.

RETROREFLECTOR
Retroreflector
Retroreflector
Assembled corner-cube retroreflector quadruplet
Retroreflector-based system and method for detecting intrusion into a restricted area
Effects of retroreflector positioning on nighttime recognition of pedestrians
An omnidirectional retroreflector based on the transmutation of dielectric singularities.
Ray trace through a corner-cube retroreflector with complex reflection coefficients
Design and analysis of a diffraction-limited cat's-eye retroreflector
DESIGN NOTE: Whole-viewing-angle cat's-eye retroreflector as a target of laser trackers
Improved limb atmospheric spectrometer (ILAS) and retroreflector in-space (RIS) for ADEOS
Backscatter suppression for underwater modulating retroreflector links using polarization discrimination
Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles