GB341071A - Improvements in apparatus for reproducing sound from records - Google Patents

Abstract

341,071. Reproducing recorded sound. WILLIAMS, W. E., Kildare, Ethelbert Road, Bromley, Kent. Oct. 4, 1929, No. 30190. [Class 40 (ii).] Optical apparatus.-A method of reproducing sound by optical means from a record of usual or normal form (i.e. a record which has been produced without any deliberate distortion), comprises the insertion in the path of the light beam of an aperture of such a shape that the displacement or dimensional variation of the beam and the amount of light passing to the light-sensitive device are in non-linear relationship. The aperture may be of lozenge or triangular shape as shown in Figs. 1 and 2 or of double triangle shape as shown in Fig. 3, and the sides of such triangles may be concaved if desired. In another form the aperture may be of general triangular shape with the taper of the sides suddenly increasing at a point say half way from the apex. The record may be in the form of a photographic or other film having recorded thereon a wavy line e, f, Fig. 1, representing the sound trace and dividing the film into two portions of different transparency or reflecting powers or otherwise optically distinguishable. Thus a beam of light reflected from or transmitted through the record reaches the diaphragm containing the aperture as an image of the record with a dark portion g and light portion h or vice versa. Alternatively, the dark portion g may represent an image of a record having one edge cut or serrated in accordance with the sounds. The image j, k, Fig. 2, represents an image formed by light transmitted through a disc or cylinder having a groove recorded on it in such a way as to be more or less transparent than the remainder of the disc or cylinder. Or, the trace j, k may represent the optical image of the sound groove on an ordinary gramophone record. For use with an aperture of double triangle form as shown in Fig. 3, the record may be in the form of a thread in which the sounds are delineated by varying thicknesses of the thread. Alternatively such a record may be formed by a film or flat band of varying width. The apertured diaphragm may be arranged so that the image of the diaphragm may be projected on to the sound groove. The diaphragm may be arranged after a condenser, the concentrated light from which is adapted to be passed through the shaped aperture and thence deflected by a totally-reflecting prism and caused to pass through a lens system which forms an image of the diaphragm on the sound groove. The sound groove is adapted to reflect the shape of the aperture back through the lens system to the photo-electric cell having a further diaphragm arranged with a vertical elongated aperture. The diaphragm provided with the shaped aperture may be formed integrally with the lightsensitive device. Specification 328,317, [Class 40 (ii), Phonographs &c.], is referred to.