Vector pinning in an electrophotographic machine

摘要

Apparatus and method for pinning the value of a white, gray or otherwise colored, single-shaded vector in an electrophotographic machine. The vector is the value of the image voltage minus the developer voltage. Valuation of changes in the image voltage are obtained by (1) sensing the reflectivity of a developed single-shaded image and converting that into a representative voltage; (2) sensing the reflectivity of the bare photoconductor and converting that into a representative voltage; (3) obtaining a comparison of the representative image and reference voltages; and (4) noting changes in the comparison. Pinning the vector calls for adjusting the member for producing the vector such as the developer voltage or document illumination intensity level an amount necessary to compensate for the change in image voltage.