In situ inonographic uniformity correction

Details In situ inonographic uniformity correction In situ inonographic uniformity correction

1990-12-31

1992-02-11

Fuller, Benjamin R.

Recorders

Electric recording

Electrochemical

346155, G01D 1506

Patent

active

050879332

ABSTRACT:
The In Situ Ionographic Uniformity Correction is a method and apparatus which solves the problem of non-uniform density of ion current projected from an ionographic print head (10) caused chiefly by variations in the dimensions of the modulation channel (24). During calibration, the present invention senses ion current (20) using a simplified ion sensor (36) which has an electrode (32), very large in proportion to the width of several modulation electrode (22). Groups (60), (61) of modulation electrodes (22) are electronically addressed in steps of one modulation electrode (22), each, across the width of the print array (16). To prevent cross-talk from rendering the sensed ion current (20) values unusable, the modulation voltage (Vm(i)) is adjusted by a feedback circuit (42) to achieve a fixed value of ion current (20) for each group (60), (61). Values of this modulation voltage (Vm)I)) are stored in an electronic data file (44). Computation of corrected modulation voltage (Vm)i)') to produce uniform ion current (20), based on average modulation voltage and a print head (10) characteristic constant, is made in a data processor (46) by a programmed algorithm which accesses the data file (44). Corrected values of modulation voltage (Vm(i)') are applied to each correlated modulation electrode (22) through a switching circuit (52). Corrected values of modulation voltage a switching circuit (52). Corrected values of modulation voltage (Vm(i)'), when applied to the correlated modulation electrodes (22), produce ion currents (20) of uniform density and result in uniformity of density in large, grey printed areas.

REFERENCES:
patent: 4644373 (1987-02-01), Sheridon et al.
patent: 4819013 (1989-04-01), Beaudet
patent: 4972212 (1990-11-01), Hauser et al.
patent: 4973994 (1990-11-01), Schneider
N. K. Sheridon, "Practical Air Assisted Inographic Printing", Proceedings, SPIE-The International Society For Optical Engineerings, vol. 1252, 13-14 Feb., 1990.

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