Abstract: Two sets of targets, one for use during cycle up convergence of electrostatics and one during runtime enable single pass cleaning of developed patches, during cycle up convergence. To this end, different targets from those used during runtime are used for the preclean, transfer and pretransfer dicorotrons during cycle up.Proper charging of the photoreceptor during runtime and cycle up convergence is also enabled by the provision of two charging targets, one for each mode of operation.

Abstract: Toner patch generation for use in tri-level imaging is effected using a laser ROS. Two toner patches are formed using a single toner patch generator of the type commonly used in the prior art. The patch generator, used by itself serves to form one toner patch latent image and together with the ROS exposure device of the imaging apparatus is used to form the other toner patch latent image.

Abstract: The Infra-Red Densitometer (IRD) readings of developed toner patches in a tri-level imaging apparatus are compared to target values stored in Non-Volatile Memory (NVM) and are also compared to the previous IRD reading. Toner dispensing decisions (i.e. addition or reduction) are based on both comparisons. In this manner, not only are IRD readings examined as to how far the reading is from the target, they are examined as to current trend (i.e. whether the reading is moving away from or toward the target). Thus, if the IRD reading indicates that the toner concentration is low but is heading toward the target then the amount of added toner is somewhat reduced.

Abstract: In order to shorten cycle up convergence, a stored or resident image is utilized. It is contained on an external control or pixel board forming a part of the machine image output terminal (IOT). The resident image together with a raster output scanner (ROS) is used to form two charge, V.sub.CAD, two discharge, V.sub.DAD and two background, V.sub.Mod patches in every frame for a total of six patches. A pair of electrostatic voltmeters (ESV) are used to read all six patches and control decisions are made on the basis of the average of the two readings for each voltage level.Because of their physical locations relative to the ROS the readings of one ESV are used in forming the two charge area patches while the other ESV is used in forming the discharge area images. Both ESVs are employed for forming the two background patches.

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: 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.

Abstract: In a single pass, tri-level imaging apparatus, erroneous voltage readings of an Electrostatic Voltmeter (ESV) which has become contaminated by charged particles (i.e. toner) are negated by using two ESVs.During each cycle up following a normal cycle down, a pair of Electrostatic Voltmeters (ESVs) are utilized to measure the voltage level on a portion of relatively uncharged portion of a photoreceptor (P/R). Using one of the ESVs, which is less prone to contamination, as a reference, the zero offset of the other is adjusted to achieve the same residual P/R voltage reading. The difference in the readings which is due to toner contamination is the zero offset between the two ESVs. The offset is used to adjust all subsequent voltage readings of the ESV until a new offset is measured.

Abstract: An apparatus in which a latent image recorded on a member is developed with a developer material comprising at least carrier granules and toner particles. Toner particles are dispensed into the developer housing and mixed with unused developer material. The toner particles and developer material are advanced along an extended path so that the toner particles are gently mixed and triboelectrically charged to substantially the nominal level prior to contacting the latent image. A system of this type is particularly useful for toner particles requiring extensive gentle mixing to achieve the desired triboelectric charge.