Patent US 4,174,528

A document scanner array which includes means for compensating for temporal changes in a light source, filters in the optical path, changes in the lens aperture and the like. The scanner array is comprised of a charge transfer device chip, which includes an exposure control section and a document information receiving section. A document holding means includes a reference indicia, with a reflection of the image of the reference indicia being imaged on the exposure control section simultaneous with the reflection of the document being imaged on the document information receiving section, in response to illumination from the light source. A common control signal concurrently applied to each section determines the time the reflected images are processed. The common control signal is terminated in response to the exposure control section sensing a given amount of light from the reflected image of the reference indicia.