Abstract: A pair of Electronic Voltmeters (ESV) are utilized to control the photoreceptor charging voltage in a Tri-Level imaging apparatus. One of the ESVs is used to control the voltage increases of a charging device. The other ESV is used to monitor the charge level of the charged area image of a Tri-Level image. When a critical value is sensed the control of the charging device is shifted to the ESV that monitors the charged area image level and limits the output from the charging device to a predetermined target value.

Abstract: Infra-Red Densitometer (IRD) readings are utilized to check the efficiency of two-pass cleaning of the black toner patch in a tri-level imaging apparatus. The IRD examines the background patch of the tri-level image and declares a machine fault if excessive toner is detected.

Abstract: A single pass tri-level imaging apparatus and method. Compensation for the effects of dark decay on the background voltage, V.sub.Mod, and the color toner patch, V.sub.tc readings is provided using two ESVs (ESV.sub.1 and ESV.sub.2), the former located prior to the color or DAD housing and the latter after it. Since the CAD and black toner patch voltages are measured (using ESV.sub.2) after dark decay and CAD voltage loss have occurred, no compensation for these readings is required. The DAD image voltage suffers little dark decay change over the life of the P/R so the average dark decay can be built into the voltage target.

Abstract: A process for controlling the amount of film buildup on a photoreceptor surface caused by certain print mode and/or material throughput conditions in a single pass highlight color printer which enables or promotes photoreceptor filming by the DAD toner additive (i.e. zinc stearate). Such filming results in the tri-level Image Push defect. This process utilizes toner coated cleaner brushes to control the film buildup thus preventing the defect. This process defines a functional equation that maintains a toner concentration at the cleaner brush fiber tips thereby controlling photoreceptor filming.

Abstract: A process for controlling the amount of film buildup on a photoreceptor surface caused by certain print mode and/or material through conditions in a single pass highlight color printer which enables or promote photoreceptor filming by the DAD toner additive (i.e. zinc stearate). Such filming results in tri-level image Push defect. This process utilizes toner coated cleaner brushes to control the film buildup thus preventing the defect. This process defines a functional equation that maintains a certain toner concentration at the cleaner brush fiber tips thereby controlling photoreceptor filming.

Abstract: Recalculation of electrostatic target values in a tri-level imaging apparatus are utilized to extend the useful life of the photoreceptor (P/R). The increase in residual voltage due to P/R aging which would normally necessitate P/R disposal is obviated by resetting the target voltage for the full ROS exposure when it reaches its exposure limit with current P/R conditions. All contrast voltage targets are then recalculated based on this new target.The new targets are calculated based on current capability of the overall system and the latitude is based on voltage instead of exposure.

Abstract: In a single pass, tri-level imaging apparatus, machine cycle down is initiated when the color developer housing is functioning improperly. The voltage level of the color image prior to its development is read using an electrostatic voltmeter (ESV). The voltage level thereof is also read after development. The difference between these two readings is compared to an arbitrary target value and a machine cycle down is initiated if the difference is greater than the target.