Patent GB-668681-A (GB)
Title: Improvements in photographic high speed cameras
Inventor: BAIRD KENNETH MCCLURE
IPC: G03B39/02
Filed: 1950-02-17
Abstract: 668,681. High-speed photography. SCIENTIFIC & INDUSTRIAL RESEARCH, HONORARY ADVISORY COUNCIL FOR. Feb. 17, 1950 [March 10, 1949], No. 4149/50. Classes 97 (i) and 98 (i). A photographic camera for taking a rapid succession of pictures of an object comprises an aperture for admitting light from an object to be photographed, adjacent light reflecting elements each located to reflect light from said aperture to a fixed location within the camera, a rotatable light reflector at said fixed location having at least one light reflecting surface movable by rotation of said reflector to reflect light consecutively from each of the light reflecting elements to the photographic film, and means for rotating the reflector. As shown in Fig. 3, a light ray 33 entering through the objective 28 is reflected by a mirror 36 on to the end reflecting face of a mirror 35<SP>5</SP>, which is one of a set of mirrors 35, the reflecting faces of which are arranged at an angle to each other. The ray is then reflected from a face 37<SP>1</SP> of a rotating prism 37 through a system comprising mirrors 39, 41, 43 and lenses 38, 40, 44 to a face 37<SP>13</SP> of the prism 37. The ray is finally reflected by a face of a second rotating prism 45 on to a strip of photographic film 31 in a magazine 23, Fig. 2. Prism 37 is continuously rotated by an electric motor 24 through a gear-box, so that images formed by the several mirrors 35 are successively reflected through lens 38 to form, by mirror 39, an image in the plane of lens 40 limited by a stop 40a. Mirrors 39, 41, 43 are adjusted by screws 46 so that mirror 39 is parallel to the axis of prism 37, but mirrors 41, 43 are at a slight angle thereto. If prism 45 were omitted, the images formed after the second reflection from prism 37 would move slowly upward, and could be recorded on a film moving at the same rate; but it is preferred to compensate for the image movement by means of the prism 45, driven by motor 24, so that the images are recorded on stationary film in the form of strips 31, Fig. 2, held in arcs by holders 30 to equalize the optical paths. The holders are supported on curved end-pieces of the magazine 23 at an angle of nearly 90 degrees thereto. The images are successively recorded at a very high speed, and the film developed. The single set of mirrors 35 may be replaced by two or more sets arranged in staggered tiers, to increase the speed of recording of images. The speed may be further increased by using an objective lens with a diaphragm having a plurality of apertures, and replacing stop 40a by a stop with staggered slits. In an alternative arrangement, a set of objectives is used, being rendered operative in turn by means of Kerr cells. Light rays, after falling on the mirrors 35, fall on a rotating prism and are reflected by a mirror and lens system back to a coaxially mounted prism and thence to the film. -In a third arrangement, prism 37 is replaced by a rotating mirror. Light reflected from the mirror is reflected back thereon at a different angle by a mirror and lens system, and is thence reflected to the film.