Patent GB-387803-A (GB)
Title: Improvements in optical apparatus for sound-recording
IPC: G11B7/00
Filed: 1931-12-15
Abstract: 387,803. Sound-recording apparatus; optical systems. REASON, R. E. and KAPELLA, Ltd., 104, Stoughton Street, Leicester. Dec. 15, 1931, No. 34673. [Class 40 (ii).] Comprises an optical system for use with sound-recording apparatus employing a vibratory mirror, wherein the light flux per unit area falling upon the record film is increased by superimposing thereon a plurality of slit images. Fig. 1 shows a plan view of the axial plane of one form of the apparatus, side elevations of the arrangement before and after reflection of the light by a vibratory mirror E being shown by Figs. 1A and 1B respectively. Light from a source A, focussed by a condensing lens B to form an image of the source on the mirror E, is delimited by a member C comprising plurality of masks p .. t, as shown in side elevation by Fig. 1F. A lens D forms an image of the masks on corresponding elements p1 .. t1 of a dissecting member F, Fig. 1c, each element of which is adapted to form an image of the mirror at G with its centre in the axial plane. At G is a second dissecting member whose elements p2 .. t2 receive light from the corresponding elements of the member F to deviate the axis of each illuminating system into the axial plane and to form at K superimposed images of the masks. Lying in the axial plane at K is also a slit which is imaged on the film at M by an objective L, and adjacent to the slit is a field lens J forming on the objective in the axial plane an image of the dissecting member G and hence a plurality of mirror images p3 .. t3. A cylindrical lens H forms on the slit a reduced image of G and the elements are so proportioned that the light from each image of the mirror is converged on the slit sufficiently to illuminate the whole diameter of the objective. Thus there is formed on the objective a plurality of bands of light p3 .. t3 and on the film a corresponding number of superimposed slit images. A dissecting member may be constructed by cutting a plano-convex collecting lens into strips of desired width, suitably displaced as shown in side elevation by Fig. 1c, cemented together to a parallel glass plate or to the face of a reflecting prism. Errors arising from inaccurate construction of the dissecting member are corrected by making the masks independently adjustable. The dissecting members may be constructed of a plurality of relatively-inclined reflecting elements. Instead of forming a plurality of images of the whole mirror there may be formed an enlarged image of the mirror on a dissecting element so that each band of light comprises a real image of a portion of the mirror. As shown by Figs. 4 and 4B, a cylindrical lens P1 forms an image of the masks on the mirror E and a cylindrical lens P2 forms an enlarged image of the mirror on a dissecting member S. The member S comprises a plurality of relatively-inclined displaced reflectors so that a plurality of images will be formed in the axial plane at the dissecting member T the elements of which are displaced along the principal optic axis to compensate for the separation of the reflectors S. If desired the images of the masks need not be superimposed until the light reaches the film, in which case a plurality of slits is employed and reflectors. are adapted to form superimposed virtual images of the slits on the film. Alternatively, an objective may be placed on each side of the film to superimpose one or more slit images on each side of the emulsion. According to a further modification, a plurality of illuminating systems with reflectors may be employed.