Ionographic printhead gating control for controlling charge density image defects due to surface velocity variations

摘要

In an ionographic device having a printhead, including a source of ions, a modulation channel defining a path for a stream of ions from the the ion source towards a moving imaging surface, an array of modulation electrodes arranged along the path to modulate the stream of ions in imagewise fashion, a gating electrode is provided at a location adjacent to the path of ion stream, biased to create a field to block or allow passage of the ion stream in accordance with movement of the imaging surface, the biasing arrangement allowing passage of ions for a maximum period over which ions for a line of the image are deposited on the moving imaging surface. The bias on the electrode is controlled in accordance with movement of the imaging surface, as detected by a motion detecting encoder, and in accordance with a predetermined period to produce a constant charge density on the imaging surface at the writing position.