Developed mass per unit area (DMA) controller to correct for development errors

摘要

In process control loops by keeping the DMA (Developed Mass per unit Area) under control, the print quality can be satisfactorily maintained to within tolerance in spite of temporal variabilities in subsystem parameters. The DMA is measured by creating patches in the interdocument zones. Three patches are created, one at high area coverage (90% to 100%), one at low area coverage (0 to 20%) and one at mid tone (around 50%). These DMA readings are compared to the setpoints. The errors are processed in the controller to generate the internal process parameters known as the cleaning voltage, discharge ratio and development voltage. These internal parameters have well known meaning to the physical xerographic process. The cleaning voltage is used to indicate the background in printing. The discharge ratio gives an indication of how much dot growth is present in the halftones. Finally, the development voltage is proportional to how much toner is laid on the photoreceptor. A controller is shown with these three process parameters, so that when used appropriately, good quality color prints can be obtained.