A stereoscopic 3D display technology that separates the stereo frames by alternating the viewing path to each eye. Used for 3D gaming and the first 3D TVs, liquid crystal (LC) shutter glasses are synchronized with alternating stereo frames on screen by an infrared (IR) emitter on the monitor or TV. Ceiling-mounted projectors use radio signals rather than IR (see RF shutter glasses). Alternate Open and Closed The liquid crystal lenses turn black to alternately block the light from each eye. The "active" refers to the electronic circuit in the glasses, whereas "passive" glasses have no circuits (see polarized 3D). See 3D visualization, anaglyph 3D, lenticular 3D, parallax 3D and 3D glasses. No Flicker or Ghosting and True Colors By supporting 120 frames per second (fps), active 3D glasses deliver the full resolution at 60 fps to both eyes. Active 3D glasses also eliminate the ghosting sometimes associated with passive polarized 3D methods, and because the frames are not modified in any manner, the viewer sees the full color spectrum. Many users claim active 3D is the best 3D experience; however, light is blocked half the time, causing the screen to be dimmer than polarized 3D. In addition, some people notice the lens flicker.