phi phenomenon A perceptual illusory phenomenon that explains the fact that people hallucinate, or believe they see, a continuous action where a series of still images is presented in rapid succession. Psy-chologist and film theorist Hugo Münsterberg explained the process in 1916. Modern television and video systems create the illusion of motion by refreshing screens in rapid succession, a dot at a time and a line at a time. Film projectors refresh the entire screen at once. See also persistence of vision. |