Patent ID: 7072598

Claim:
A method for determining a proper transfer bias for each one of a plurality of colors, wherein said proper transfer bias is applied to a primary transfer member which enables transfer of said color images from a photoconductive drum so as to generate full color images, the method comprising: providing a photoconductive drum having an image region and a nonimage region; determining a plurality of nonimage potentials for the nonimage region, wherein each nonimage potential corresponds to a respective one of the plurality of colors; for said first color, determining a proper transfer bias voltage by, applying a first nonimage potential corresponding to the first color to the photoconductive drum, applying at least two predetermined voltages to the primary transfer member, obtaining at least two currents corresponding to said two predetermined voltages during rotation of said primary transfer member, and using the two currents and predetermined voltages to determine the proper transfer bias voltage for the first color; and for all subsequent colors, determining a proper transfer bias voltage for each subsequent color by employing the first nonimage potential and the nonimage potential for the subsequent color.