DUAL DENSITY GRAY PATCH TONER CONTROL

A method and apparatus are provided to calibrate a xerographic print engine toner concentration sensor to accurately control the toner concentration to a specified operating target. At least two control patches are imaged onto a photoreceptor. Each patch has a different voltage level where the voltage levels are the difference between the exposure discharge voltage and the developmental roll voltage. The relative reflectivity of each patches is obtained. The latent patches are repeatedly developed at different toner concentrations. The reflectivities of the patches formed at the same toner concentration are combined to obtain a combined reflectivity for that toner concentration. As a result, a toner concentration curve is obtained that has an improved response relative to the toner concentration curves that correspond to each of the individual voltage levels.