Smart Printhead Electronics controls Print Quality in Océ's Direct Imaging Process

Abstract

Direct Imaging (DI) is a unique 7 color print process being developed by Océ and applied for the first time in the Océ CPS700 printer/copier that will be introduced this year [1]. In this process digital information is converted into a (dry) toner image on a DI-drum (‘printhead’) in a one-step process. In a single pass process 7 color toner images from 7 separate DI image forming units, are collected on a rubber intermediate roller and subsequently fused onto paper using Océ's Color Copy Press technology. In Direct Imaging, 5000 to 7500 conducting tracks on the surface of each DI-drum are controlled by means of a large number of ASIC's that convert a digital image into either 0 or 40V voltage at appropriate times. When a track is powered with 40V, toner locally adheres to the surface.Recently we discovered a unique feature inherent to the DI Print Process that enables us to use smart driver electronics, implemented in ASIC's specifically designed for Direct Imaging, to control print quality in a very elegant and stable way. The same driver electronics that power the DI-drum tracks, thereby forming a toner image on the surface of a DI-drum, is able to measure directly the amount of toner deposited. This is done by measuring the change in capacitance (or more general impedance) of drum-tracks which shows to be directly related to the amount of toner deposited on each track. Measurements can be done fast enough and with such high sensitivity that toner coverage can be measured directly after or even during printing of each pixel-line if necessary. This holds for toner coverage on a very local scale (on each track, ‘pixel-information’) or averaged across many tracks. This paper will describe how above mentioned ‘tonersensing’ measurements are done and how this offers many opportunities for using feedback schemes for stabilizing or improving print quality.