Browse Prior Art Database

INK DROP SENSOR

IP.com Disclosure Number: IPCOM000024808D
Original Publication Date: 1982-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 170K

Publishing Venue

Xerox Disclosure Journal

Abstract

An improved optical drop sensing technique is disclosed for utilization in an ink jet marking system. United States Patent 4,255,754 discloses the use of optical fibers for sensing both the position and/or speed of an ink jet droplet in its trajectory towards a recording medium. Drop speed and position information is needed in order to calibrate the ink jet system. If, for example, the system comprises a number of ink drop nozzles which throw ink droplets to specific portions of a recording medium, the sensors can help "stitch" together ink from adjacent nozzles to insure all regions of the medium are covered. The present disclosure comprises an improvement over the optical sensing technique discussed in the '754 patent.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

INK DROP SENSOR
Proposed R. D. Houston Classification

U.S. C1. 346/75 Int. C1. Gold 15/18

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DETECTOR

FIG. 2

FIG. 3

Volume 7 Number 2 March/April 1982 81

[This page contains 1 picture or other non-text object]

Page 2 of 4

INK DROP SENSOR (Cont'd)

An improved optical drop sensing technique is disclosed for utilization in an ink jet marking system. United States Patent 4,255,754 discloses the use of optical fibers for sensing both the position and/or speed of an ink jet droplet in its trajectory towards a recording medium. Drop speed and position information is needed in order to calibrate the ink jet system. If, for example, the system comprises a number of ink drop nozzles which throw ink droplets to specific portions of a recording medium, the sensors can help "stitch" together ink from adjacent nozzles to insure all regions of the medium are covered. The present disclosure comprises an improvement over the optical sensing technique discussed in the '754 patent.

Illustrated in Figure 1 is a schematic representation of an ink drop printing system I having a nozzle 2 for generating a column of ink 3 in a trajectory towards a recording member 4. At a position intermediate the nozzle 2 and the recording member 4, the column 3 breaks up into individual droplets 5 which are charged by a charging electrode 6 and deflected through a controlled trajectory by a pair of deflection electrodes 7 (only one of which is illustrated in Figure 1). The improved sensor 8 comprises an input light bar 9 and a pair of light output bars 10, 11. Mounted to an input portion of the light bar 9 is a light emitting diode 12 coupled through a lead 13 to a pulse generator which activates the light emitting diode 12 at controlled intervals with a pulse waveform.

Light from the light bar is transmitted across the path of the droplets to the output light bars 10, 11. Coupled to an output portion of those light bars are two light detectors 14, 15 which in turn are coupled to a differential amplifier 16. The light emitting diode is pulsed on for a period long enough to capture the fastest and slowest moving drops at the boundary line between the two output bars. The output configuration to the differential amplifier is similar to that disclosed in the '754 patent so that the point at which droplet passes the interface between the two output bars is well defined on the output from the differential amplifier. Further discussion relating to the technique for analyzing this output signal may be found by reference to the '754 patent.

Illustrated in Figure 1A is a view of the light bar sensor 8 from the plane of the recording medium. As seen in that view the light bar sensor extends a substantial distance along the width of the recording member and as a result ink droplets are detected even though the droplets have been swept from side to side due to interaction with an electric field generated by the deflec...