| 摘要 |
<p>667,231. Photo-electric exposure control. POLLASCHEK, V. Oct. 31, 1949 [Nov. 2, 1948; Sept. 5, 1949], Nos. 27820/49 and 27821/49. Class 40 (iii). [Also in Group XX] An automatic exposure adjusting device for a camera comprises a rotatable screen 4 between the objective 6 and the film carrier 25, controlled by an electromagnetic rotor 3 energized by a photo-cell 1, the opacity of which screen varies in such a way that the reduction of light to the film for each position of the screen is proportional to the luminosity of the object, independently of the response characteristics of the photo-cell and the rotor. The screen 4, Fig. 1, is carried on the shaft 3<SP>1</SP> of the rotor 3, and its surface is divided into a series of segments 51, Fig. 2, whose opacity in the light path is made, by a photo-chemical or other process, to be proportional to the light intensity to the photo-cell 1 for that position of the rotor 3, the extremes of rotation being indicated by two coloured marks 7, 8 visible through the viewfinder 12. As shown (Fig. 2), the window 23 in the film carrier 25 contains at least three sections 5<SP>1</SP>, and the speed and direction of travel of the shutter slide 13 is therefore arranged to compensate for the variation in opacity over the area of the window. Alternatively, (Fig. 3) the shutter may comprise a rotary disc 14 whose exposure part 15 is also segmentally graded in opacity, to compensate for the varying opacity of the screen 4. The screen may alternatively consist of an opaque screen with slots of varying width to vary the intensity of light reaching the film. An adjustable screen 16 may be introduced in front of the photo-cell 1 to allow for different film sensitivities and/or colour filters, controlled by a knob 17, its position being indicated on a dial 18. A further screen 19 may be introduced to allow for variations in exposure time, this screen being automatically adjusted by gears, levers, &c. not shown.</p> |
