Edison helped design the kinetoscope, a precursor(前身、先駆者)to the modern motion picture projector. It worked through a phenomenon known as "persistence of vision," in which a sequence of images is blended by the eye to create the illusion of motion. Because the work of so many others had gone into its invention, Edison never bothered to apply for an international copyright on the device, believing that it would not stand up(受け入れられる、通用する)in European courts.