Color motion-picture projection system

Claim 1

Color motion picture projection apparatus of the additIve synthesis type, in which images obtained by selection by means of several colored light filters and reproduced one after another in a determined order of colors on a black and white film are successively projected in light of a color band adapted to each image, the black and white film having reference marks in predetermined registration with the images, said apparatus comprising: a first motor for continuously advancing the film; a source of white light and an objective lens on the same optical axis; a multiple face prism being disposed on said optical axis and driven in rotation by a second motor, the number of said faces being an even multiple of the number of colored light filters used for selecting the single color images reproduced in black and white on said film, the opposite faces of said prism being provided with transparent colored coatings which are preferably identical, said coatings being respectively determined by filters used for making the film and respectively disposed on said faces in the uniform order of selection of the colors; a support rigid with the shaft of said second motor and comprising reference marks for indicating the angular position of the coatings of a given color of the prism; a first means for detecting the reference marks borne by the film facing each image corresponding to a particular color band; a second means for detecting the reference marks indicating the coatings of the prism; and a phase comparison circuit to which are applied the signals respectively generated by said first and second detection means, said phase comparison circuit delivering an output signal used for synchronizing the rotation of said first and second motors.