Browse Prior Art Database

Raster Scan Control for an Ink Jet Printer

IP.com Disclosure Number: IPCOM000086419D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Arnold, RW: AUTHOR

Abstract

Ink drops 10 of a ferrofluid ink are projected by a drop generator 11 past magnetic selector 12, magnetic deflector 13 and deposited either in gutter 14 or on paper 15 to form characters or other symbols. The height of the scan signal from raster generator 16 applied to deflector 13 must be regulated, if the character height across the line of printing is to be regular in appearance. For this purpose, a drop detector 17 is positioned adjacent the drop stream between the deflector 13 and gutter 14.

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Raster Scan Control for an Ink Jet Printer

Ink drops 10 of a ferrofluid ink are projected by a drop generator 11 past magnetic selector 12, magnetic deflector 13 and deposited either in gutter 14 or on paper 15 to form characters or other symbols. The height of the scan signal from raster generator 16 applied to deflector 13 must be regulated, if the character height across the line of printing is to be regular in appearance. For this purpose, a drop detector 17 is positioned adjacent the drop stream between the deflector 13 and gutter 14.

The drop detector 17 preferably comprises a mask 18 in the vicinity of Q light source with a horizontal slit 19, which produces a horizontal light beam to be projected through lens 20 across the stream of drops 10 to a phototransistor 21. The phototransistor 21 and the light beam are located so as to detect drops near the desired apex of the raster scan of the ink drops. The horizontal slit 19 must be wide enough in the direction of stream flow to assure that the raster is sensed, but because of this width, more than one ink drop might be sensed for a single scan.

Fig. 3 shows details of an automatic gain control circuit 30 which tolerates the detection of up to four successive ink drops. Phototransistor 21 normally conducts about 5 milliamps of current. As a drop 10 passes the light beam the current decreases about 50 microamps. The input current from transistor 21 is amplified by operational amplifier 22 to a voltage e(1).

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