 Edge blended areas where projectors overlap often have some smearing, double images, and can have very obvious additive black level areas if poorly designed or configured.A wide variety of video projection technologies has been employed in domes, including cathode ray tube (CRT), Digital Light Processing (DLP), liquid crystal display (LCD), liquid crystal on silicon (LCOS), and most recently, two varieties of laser projectors (see the laser video projector).For multi-projector systems, in particular, display devices must have a low black level (i.e., project little or no light when no signal is sent to them) to allow for reasonable edge-blending between the different projector footprints.