International Business Machines Corporation

E Hal Bogardus

Menachem Levanoni

Walter W Hildenbrand

An electrostatic lens is disposed between a charge electrode and deflection plates to electrostatically focus each of the droplets on a recording surface at a position in alignment with the nozzle supplying the stream. The lens preferably comprises three electrodes with each of the outer electrodes having the same potential, which is substantially equal to the kinetic energy per unit charge of each of the charged droplets and of opposite polarity to the charge on the droplets, and the third electrode preferably being grounded. Each of the electrodes has a circular aperture through which the charged droplets pass with the electrodes being spaced from each other in the direction of the stream a distance preferably no greater than the diameter of the aperture. If desired, the electrode, which is furthest from the nozzle, can be omitted although this will produce some deceleration of the droplets.

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Poughkeepsie, NY, United States of America

E Hal Bogardus