| 摘要 |
<p>870,963. Photo-electric exposure control. AGFA A. G. Sept. 21, 1959 [Sept. 25, 1958], No. 32125/59. Class 40(3) [Also in Group XX] A camera lens aperture is controlled by a photo-resistance with a permissible loading at least five times as great as the maximum expected loading. A photo-resistor 14, Fig. 3, is mounted behind two slide plates 16 and a cats-eye diaphragm 4 whose setting is controlled via spiral cams 29 by the position of a setting ring 3 which is adjusted for film speed. A galvanometer in the photo-resistor circuit is coupled to the camera lens diaphragm. log, Fig. 4, is the currentillumination curve for the photo-resistor where illumination is plotted in terms of the corresponding stop valve which has to be set. Ig is the curve of current required by the galvanometer to set a given stop value. For correct aperture setting these curves should coincide. Iog is moved parallel to the illumination axis to I 1 . Fig. 6, by adjusting the plates 16, to coincide with Ig at the point 39. I 1 is depressed to I 2 by insertion of the series resistance 40, Fig. 7, and I 2 is raised to I 3 , which closely approximates to Ig, by insertion of the shunt 43. The resistors 40, 43 may be variable. The lens situated a distance f/3 to f in front of the photo-resistor has the same field of view as the camera lens and may have its rear face finely matted. The photosensitive surface is the same shape as the photographic image and the diaphragm in front of the photo resistor is the same as the camera lens diaphragm. The galvanometer may be used, by actuating a switch, to check the battery voltage.</p> |
