GB281248A - Improvements in or connected with the recording or reproducing of sound in talking cinematography - Google Patents

Abstract

281,248. De Forest Phonofilms, Ltd., (Assignees of Forest, L. de). Nov. 27, 1926, [Convention date]. Records, photographic; records, combined photograph and kinematograph; optical apparatus. - Relates to photo-electric recording of sound on a kinematographio film and reproduction therefrom, and particularly to systems of the kind described in Specification 274,118, involving the simultaneous production of two records of sound from the same source (such as an orchestral, on one film. According to the invention, the positive film, from which sound is reproduced, is a composite one, consisting of two attached films with the sound records thereon superposed. The component films are differently coloured; and light-filters are used in association with a duplex photo-electric reproducing apparatus, in order that the records may individually, but simultaneously, effect the operation of their own loud-speakers. In making the records, the sound is picked up by two microphones 11, 12, or groups thereof, spaced apart, the microphones being connected to amplifiers 7, 8, Fig. 1; these operate photographic recorders 5. 6, which are placed behind slits 2, 3 past which the film 4 moves, the slits being located as shown in Fig. 2, so that the two sound records are formed on opposite edges of the film. Alternatively, the sound records may be made at other places on the film than the marginal edges, or on separate films. The two records are printed on separate positives, in such a manner that when the positives are superimposed, one sound record lies directly over the other, with a vertical displacement corresponding to the vertical distance between the slits 2. 3 of the recording-apparatus. Before the two films are cemented together, they are dyed different colours, one being dyed blue, for example, and the other red. For reproducing the sound, apparatus such as is shown in Fig. 3 is used, comprising lamps 17, 18 arranged on one side of a film gate 21 having two slits 22, 23 past which the film moves, and photo-electric cells 26, 27 on the opposite side. The cells, whicli are connected to amplifiers 30, 31, operating loud-speakers 34, 35, are sensitive to different kinds of monochromatic light; the cell 26 is specially sensitive to red or infra-red rays, while the cell 27, of the potassium mirror type, is sensitive to light near the blue end of the spectrum. In order that each cell shall be influenced only by one of the two records, appropriate light filters 24, 25 are placed in front of the photoelectric cells; thus, in the case described, the filter 24 transmits red light only, and the filter 25 blue light. With this arrangement, each of the superposed sound records effects reproduction by its own loud-speaker. The horns are arranged with respect to the screen 38 in a manner corresponding to the location of the components of the original source of sound.