Electrographic printing with a latent image generation by direct
dielectric charging offers the advantage of continuous toning. Such
continuous toning can be used for both full grey scale and full colour
printing. For high quality imaging, in both cases, the evenness of charge
distribution and image edge sharpness and smoothness become requirements.
The latent image formed by a matrix of electron beams is degraded by
charge-to-charge interactions. Outcomes of such interactions are the
blooming effect, the image deflection, and compression which together
cause non-uniformity in the horizontal charge distribution. Variability in
the horizontal charge distribution is periodic and produce the vertical
banding with DPI/2 frequency. To suppress the banding defect, printing
with variable dot order is suggested.
The charge distribution uniformity can also suffer from the
variability of the charge emission from individual charge generating sites
caused by the printhead manufacturing tolerances. Liberation of the print
quality from the printhead structural imperfections seems to be feasible
using the latent image potential rather then the electron beam timing for
the deposited charge density limitation. The principal structural
arrangement of such a printing system is discussed.
Igor Kubelik, Igor Kubelik,
"Nonlinearity and image distortion in electrographic continuous toning print", Proc. SPIE 1670, Color Hard Copy and Graphic Arts, (1 May 1992); doi: 10.1117/12.2322270; https://doi.org/10.1117/12.2322270