structure is disclosed for a charge - coupled device for generating reference signals indicative of black and white optical conditions and for generating an end - of - scan indicator signal . the black reference signal is generated by electrically and optically isolating one or more photosites of the ccd . a white reference signal is generated by injecting a controlled amount of charge into one or more elements of a shift register of a charge - coupled device . the end - of - scan indicator signal is generated by injecting a signal into at least one element of a shift register which does not have photosites associated with it . the black and white reference signals allow the utilization of the full dynamic range of the device under a wide range of operation conditions , while the end - of - scan indicator eliminates the need for external counting or reset circuits associated with conventional charge - coupled devices .