Automatic exposure device

摘要

An automatic exposure device for a photocopying machine. A signal indicative of exposure light intensity and a signal indicative of the received light intensity from an original are obtained by initially exposing two types of original documents the densities of which are different from each other. A proper exposure light intensity is established corresponding to the density of the original document to be copied on the basis of the above-obtained intensities. If the exposure light intensity changes in accordance with the density of an original document and the exposure light intensity to be changed should exceed an upper limit value or be less than a lower limit value, that limit value is established as the proper exposure light density.