Patent GB-716365-A (GB)
Title: Improvements in and relating to camera backs for taking photographs of the lined screen type, especially photographs of objects moving at high speed
IPC: G03B17/26
Filed: 1950-09-06
Abstract: 716,365. Photographic cameras. KODAK, Ltd. Sept. 6, 1950 [Sept. 7, 1949], No. 21930/50. Classes 97(1) and 98(1) A camera back comprises a holder for locating a light-sensitive material with its surface in the focal plane of the camera lens, a line screen mounted in front of said holder parallel to the focal plane, the lines of the screen being transparent spaces separated by opaque areas many times wider than the opaque areas; a capping shutter mounted in front of said holder and adjacent to and parallel to said line screen said capping shutter consisting of alternating transparent and opaque lines parallel to the lines of the screen, the transparent lines of the capping shutter being wider than those of the screen and the grid intervals of both the line screen and capping shutter being equal; and driving means to effect relative parallel continuous movement between the lightsensitive material, the line screen and the capping shutter in a direction across and at right angles to the grid lines from a starting to an end position in both of which the opaque lines of the capping shutter cover the transparent lines of the screen, said driving means giving such different relative speeds to the light-sensitive material and the grids that during the relative movement each of the transparent lines of the line screen exposes the light-sensitive material for a distance of relative travel not more than and preferably equal to the grid interval of the screen. As shown, a camera back 12 attachable to the rear supporting board of a bellows connected to the camera lens is provided with two fixed shafts 29, 33 on which are rotatably mounted members 34<SP>1</SP>, 35<SP>1</SP> along arms 39' of which are pivoted at 40<SP>1</SP> by means of links 30' and directly at 43<SP>1</SP> grid members 10, 11. respectively so that as the members 34<SP>1</SP>, 35<SP>1</SP> rotate they move uniformly but at different speeds across a stationary photographic plate 24 to expose progressively the.area behind each screen interval. The grid 10 acts as an exposing line screen and comprises a thin (.005 inch) copper sheet having etched line apertures of width .001 inch on a screen interval of .030 inch which is held taut by tapes attached along top and bottom to the links 30<SP>1</SP>. The grid 11 acts as a capping shutter for the line screen and comprises an exposed photographic plate having transparent lines of width .010 inch on the same screen interval of .030 inch. The capping shutter 11 is driven at 4/3 of the speed of the line screen 10 so that starting with the grids in the Fig. 5 position, the shutter 11 when it has moved .080 inch in the direction of the arrow opens the transparent lines of the screen 10 to expose the plate for the-next .040 inch travel of the shutter so that the line screen effects progressive exposure of the .030 inch width space-covered by each screen interval, whereafter the two grids are brought to rest before their apertures again register. Preferably the start and rest positions of the two grids are with the shutter grid apertures opposite the middle of the opaque lines of the line screen, a complete exposure lasting for a travel of .090 inch of the screen. Operation. The main camera shutter being closed, the line screen 10 and capping shutter 11 are moved to their set position by anticlockwise rotation against a return spring of a knob 51 bearing an eccentrically mounted pin 53 engaging an arm 39<SP>1</SP> of the member 34<SP>1</SP>. which is moved against a spring 46 urging it anticlockwise about the shaft 29. The manual setting action overcomes a clutch 62 which is adapted to prevent double exposures due to clockwise rebounding movement of the member 34<SP>1</SP> on the arm 39<SP>1</SP> engaging an adjustable stop 75. The clutch 62 comprising an outer member 63 fixed to the member 34<SP>1</SP> and an inner clutch member 64 which has wedge shaped recesses, as at 65. each containing a clutching roller 66 and which is carried by a sleeve 67 rotatable on the shaft 29 and provided with a friction disc 68 engaging with a similar disc 69 splined for spring-resisted axial movement only on the shaft 29. The two grids 10, 11 are held set by a similar clutch 78 having its inner member 79 fixed to the shaft 33 and disposed to resist anticlockwise movement of the member 35'. The main camera shutter is then opened by making a bulb exposure and either simultaneously from operation of said shutter release or subsequently as by manual movement of the button 86 a rod 87 moves a pin 88 on a friction disc 83 overcoming the resistance of a fixed friction disc 85 so that a peg 84 on the disc moves the rollers, such as 81. of the clutch 78 to free the outer clutch member 82 and hence the member 35<SP>1</SP> to make an exposure. If it is desired only to expose a fraction of the available space on the plate behind each opaque line of the screen 10 so that several different objects may be recorded on one plate, the knob 75<SP>1</SP> is set to bring the appropriate mark 76 against the fixed index 77 thereby moving the pin 75 to limit accordingly the movement of the member 34<SP>1</SP>. Since the screen 10 and capping shutter 11 are then brought to rest with the screen 10 uncapped, the plate is fogged over one transparent screen line width at the end of each area exposed so that the maximum number of different objects which can be recorded is fifteen and the elements of each different picture is separated from its' neighbours by an opaque line. Modifications. The capping shutter 11 may be pivoted on a separate set of arms on the members 34<SP>1</SP>, 35<SP>1</SP> by links instead of directly on the arms 39<SP>1</SP> while the two grids 10, 11 may be held set by a L-shaped blade with an upturned finger attached to a push button release engaging in its underpressed position a lug on the member 34' when this is in the set position. Specifications 117,342, [Class 97(i)], and 716.420 are referred to.