Abstract: An apparatus for developing a latent electrostatic image on a charge retentive surface moving in a process direction with toner, the apparatus comprising: a supply of toner; a donor structure spaced from the charge retentive surface for conveying toner from the supply of toner to an area adjacent the charge retentive surface, a device for applying an alternating current directly to the donor structure to create an alternating electrostatic field between the donor structure and said charge retentive surface to produce a toner cloud adjacent the charge retentive surface for developing the latent electrostatic image thereon; and an edge enhancement device, adjacent to the donor structure, for redistributing toner on the developed latent electrostatic image.

Abstract: In a xerographic development system, a primary developer supply is used to develop electrostatic latent images. A secondary developer supply is available to dispense new developer, as needed, into the primary developer supply. A series of inputs, including counting the number of printed pixels and monitoring the reflectivity of a set of test patches, is entered into an algorithm which controls the dispensing of new developer. The various inputs are converted into metrics which relate to an amount of time fresh developer is dispensed into the primary developer supply.

Abstract: In a control system for xerographic development, an important value to be monitored in real time is the ratio of toner to carrier (T/C) in the developer supply. However, direct measurements of T/C, whether by magnetometer readings of the developer, or densitometer readings of developed test patches, tend to be noisy. To exclude unusual T/C measurements, after every T/C reading, a likely range of change in T/C is calculated. If a subsequent T/C reading is not within this likely range, the reading is substituted with an upper or lower boundary of the calculated likely range.

Abstract: In a xerographic development system wherein toner is conveyed from a donor member to a charge receptor by a development field having a DC bias and an AC component, reflectivities of a first test patch having a first target halftone density and a second test patch having a second target halftone density are measured, resulting in first and second possible errors. If the first error and the second error have the same sign, i.e., both patches are too light or too dark, the errors are substantially cured by altering the DC bias. If the first error and the second error have different signs, i.e. one patch is too dark and the other too light, a different correction strategy is employed.

Abstract: In a xerographic development system in which an AC field is set up in a gap between a donor member and the photoreceptor to develop an electrostatic latent image, a series of tests are performed to ascertain that the width of the gap is within a suitable range. In test mode, various DC and AC biases associated with the field are systematically altered, and the reflectivities of resulting test images are read. Based on these reflectivity readings, it can be determined if the gap is too wide, such as to cause poor print quality, or too narrow, such as to cause arcing.

Abstract: In a xerographic printing apparatus wherein a development field is maintained between the photoreceptor and a donor member, there is always a danger of arcing across the field, particularly at high elevations. An arcing-avoidance system interacts with the print quality control system of a printing apparatus, to monitor the biases within the apparatus being demanded at various times by the control system. If a bias consistent with arcing conditions is approached, the arcing-avoidance system constrains the control system to avoid the arcing conditions. The arcing-avoidance system accepts as an input the elevation of a particular printing apparatus.