GB567391A - Mapping camera - Google Patents

Abstract

567,391. Cameras for aerial photography. CHICAGO AERIAL SURVEY CO. Nov. 7, 1941, No. 14366. Convention date, Oct. 26, 1940. [Class 98 (i)] A camera for producing a continuous photograph of the ground flown over by an aircraft, in which the film is continuously moved during exposure, comprises a finder having a continuously moving member driven in synchronism with the film and bearing spaced transverse lines which are visible through the finder screen, means for conjointly controlling the speed of this member and of the film, and longitudinal lines on the screen extending in the direction of movement of the member. The speed control is adjusted to maintain the speed of movement of the finder image equal to that of the moving member, and the camera is angularly adjusted so that the image does not move laterally in relation to the longitudinal lines on the finder screen. In the camera shown, film is constantly fed during exposure from a spool 29 to a take-up spool 33 by an apertured feed-roll 32, the film being held to the roll by the action of suction means connected to the hollow interior of the roll. The take-up roll is rotated from the feed roll through a slipping spring belt drive 65. The film passes over an exposure slot formed between two plates 26, 27, the former of which is movable by means of a wedge plate 31 to vary the width of the slot. The feed roll is rotated through helical gearing and a clutch 63 from a motor 47, the speed of which is adjustable by means of a control button 76. A finder lens projects an image on a ground glass plate 40 behind which moves a transparent endless indicator strip 38 driven by the motor, on which are uniformly-spaced transverse lines. By controlling the speed of the motor, the cross lines may be made to maintain coincidence with the moving finder image, when by closing the clutch 63 the film will be driven synchronously with the strip and at the speed at which the main image crosses the exposure slot. Lines 42 on the plate 40 extending longitudinally, i.e. in the direction of movement of the strip 38, indicate lateral movement of the image, which is corrected by angular adjustment of the camera. The camera is carried in a gimbal mounting so that the optical axis may be inclined to correct for aircraft movements, and may also be rotated about a vertical axis so that the direction of movement of the film and indicator strip may be rendered parallel to the movement of the aircraft as modified by drift. A film footage indicator operated by a pivoted arm engaging the outer turn of the supply roll is provided.