GB611622A - Improvements in photographic cameras particularly photo-mechanical cameras - Google Patents

Abstract

611,622. Photographic cameras. HULL, S. V., SMITH, F. H., and PICTORIAL MACHINERY, Ltd. Nov. 24, 1945, No. 31742.. [Class 98 (i)] An optical system, for use in a photographic camera and adapted to produce at will either normal unreversed or laterally reversed images while the directional relations between object and image remain constant, comprises two reflecting surfaces, one of which is fixed in directional relationship to the object and the other is fixed in relation to the optical axis of the camera, but is movable in directional relation to the fixed reflecting surface so that in one position of said movable surface the light beam is reflected only by the movable surface to produce a reversed image, while in the other position it is reflected by both reflecting surfaces to produce an unreversed image. As shown, the known combination of camera lens 12 and isosceles right-angled prism 14 having entry and exit faces 21, 22 is used to produce a reversed image. A second prism 16 lies below the lens and the first prism, its two perpendicular rectangular faces 25, 26 being parallel and perpendicular respectively to the plane containing the axial ray and the faces 22, 26 lying in the same plane. By rotating the prism 14 through 90 degrees about the axis of the camera lens 12, so that the faces 22, 25 are adjacent and parallel and the two prisms are arranged Porro-wise, an inverted and reversed, i.e. normal, image is produced. In modifications, the prism 14 is rotatably carried on the front wall 18 of the camera and carries the lens 12 on its face 22 while the prism 16 may be disposed above the prism 14. The prisms need not be right-angled, but merely of supplementary angles although in such cases the object and image planes may be non-vertical. The Provisional Specification refers to the . use of mirrors instead of prisms and specifies aluminium as an alternative to silver for the reflecting surfaces. The Provisional Specification also describes an arrangement wherein the axis of the light beam from the object is at 60 degrees to the camera axis. A mirror is arranged at 30 degrees to the camera axis and this alone produces a reversed image. A second mirror is arranged on the axis of the camera at 60 degrees to it and farther from the camera than the first mirror. To produce unreversed images the first mirror is caused to turn through 120 degrees about the point of intersection of its own plane with the normal to the second mirror at the point at which the camera axis meets it. Instead of mirrors, the first reflector may be an equilateral prism, while the second fixed reflector may be a 120 degrees prism.