GB251018A - Improvements in or relating to optical systems for photographic and kinematographic cameras and projectors and the like - Google Patents

Abstract

251,018. Crow, A. B., and Dunn, E. M., (Executrix of Dunn, E. J.). Jan. 22, 1925. Addition to 228,207. Optical systems for cameras and projectors, utilizing achromatic prisms, for the production of a number of identical images, arranged radially round the principal axis, with the thin edges meeting, are provided with divisions arranged to prevent overlapping of the images, and to provide for the correct area of each prism in accordance with the time factors for suitable exposures. The prism-combination e, e<1> is disposed near to the objective a, b, which is, together with the prism combination, divided into quadrants by partitions p<l> - - p<4>. These partitions may be extended throughout the camera. Alternatively, the divisions may be spaced at unequal angles, Fig. 4, but the prisms cut so that the images p are equally spaced. In a modification the effective areas of the prisms may be modified by the insertion of opaque wedge-shaped stops e - - b, Fig. 2, so that the areas are proportional to the exposures required for the various colour filters used, such filters being placed between the prisms and the focal plane of the lens. In one construction, the divisions do not pass through the elements of the lens, but are fitted with narrow flanges covering a portion of the lens to prevent overlapping of the images. Focussing may be effected by a supplementary lens movable along the axis of the objective, or by altering the distance between the elements of the objective.