Exposure control for copying machine

摘要

Exposure control for an image projecting system, particularly for a projection system in which an image is projected from an illuminated object plane through a lens and onto an image plane of a copier of the full frame exposure type. Illumination means are employed for illuminating an object plane. Transducer means, preferably in the form of a photosensor, are provided in the light path and on the image side of a lens for primarily sensing the intensity of the light incident on the image plane. The transducer means produce an output signal which varies in accordance with the intensity of the projected image, and integrating means coupled to the transducer are adapted to produce a time integral output signal of the intensity of the illumination sensed by said transducer means. Means are further provided for discontinuing the illumination of the object plane by the illumination means when the time integral output signal reaches a predetermined level.