Xerographic copier.

摘要

In a test cycle, either at the end of a short copy production run or during an interruption in a longer copy production run, a xerographic copier is arranged to produce a toned test patch (30) in an otherwise cleaned imaging area (28) of the photoconductor (26). The optical density of both the cleaned and test areas are sensed by an electro-optic system to provide output signals indicating the respective densities. These signals are compared in a control circuit primarily to provide output signals indicating requirement for replenishment of the developer mix with toner.