| 摘要 |
<p>An adjustable diaphragm is driven by an adjusting motor. A first light sensor is positioned behind a first light attenuator, and a second light sensor behind a second light attenuator. The attenuators are likewise driven by the adjusting motor. A negative-feedback control circuit actuates the adjusting motor to keep the amount of light incident upon the first light sensor negative-feedback-regulated. As the position of the motor output element changes, the fraction of incident scene light transmitted by the first light attenuator, that transmitted by the second light attenuator, and that transmitted by the diaphragm, vary. The variations in the fraction of light transmitted by the second light attenuator are the same as those in the fraction of light transmitted by the diaphragm, but different from the variations in the fraction of light transmitted by the first light attenuator. For each different value of scene-light brightness, a different respective combination of exposure-duration and diaphragm-setting can be preprogrammed, for subsequent automatic selection of these value combinations in dependence upon scene-light brightness, during operation of the system in the camera.</p> |
