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Browse Prior Art Database

Rear Surface Magnetic Toner Sensor for Magnetic Printing

IP.com Disclosure Number: IPCOM000042594D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Chamberlin, TJ: AUTHOR [+2]

Abstract

One form of magnetic printing utilizes a magnetizable medium, such as magnetic tape, upon which a magnetic latent image is formed. This magnetic latent image is made visible with the use of a dry toner containing small magnetic particles commonly referred to as monocomponent toner. The visible image is then transferred to paper and fixed with methods commonly known in the electrophotographic printing art. A critical element of this printing process is the effective toner mass per unit area deposited in the solid areas of an image. For both magnetic printing and electrophotography, this parameter is critical to maintaining print quality for printing characteristics, such as dark reflectance and line width.

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Rear Surface Magnetic Toner Sensor for Magnetic Printing

One form of magnetic printing utilizes a magnetizable medium, such as magnetic tape, upon which a magnetic latent image is formed. This magnetic latent image is made visible with the use of a dry toner containing small magnetic particles commonly referred to as monocomponent toner. The visible image is then transferred to paper and fixed with methods commonly known in the electrophotographic printing art. A critical element of this printing process is the effective toner mass per unit area deposited in the solid areas of an image. For both magnetic printing and electrophotography, this parameter is critical to maintaining print quality for printing characteristics, such as dark reflectance and line width. The reflectance of the transferred, fused image can be used as a guideline to estimate toner mass per unit area; however, resolution at dark printing levels is very poor. In addition, the transfer process efficiency must be estimated to determine the monocomponent toner volume deposited on the developed image. Another parameter of concern is the mass of background toner present in white areas of a printed page. This measurement is complicated by the very low toner mass per unit area which can cause substantial background. A toner mass sensor capable of this measurement and the measurement of toner mass per unit area in black image areas will be described. This monocomponent toner sensor, which will measure toner mass developed on a magnetic image, can be understood with reference to Fig. 1. A balanced magnetic system composed of two specially designed ring core sections 1 and 2 is shown, separated by a spacer 3. A common driving section 4 is wound with several turns of magnetic wire 5 which is driven by a power source 6. The power source 6 operates in two modes: mode (a) produces a low frequency writing current, and mode (b) simultaneously produces a high frequency current and a DC magnetizing current. Uses of these modes will be described. When the power source 6 is producing a high frequency (100 KHz) current in the windings 5, a magnetic field is produced which is equally divided between the upper and lower magnetic paths 7 and 8. Therefore, the sensing coils 9 and 10 will develop the same secondary output voltage, since the magnetic environment of gaps 11 and 12 are identical. If the sensing coils 9 and 10 are wound in series opposition, the resulting output voltage Vdiff will be zero. To assure fine balance and to compensate for fabrication tolerances, a set of balance adjustment coils is shown. Referring now to Fig. 2, the upper magnetic gap 11 is in contact with the rear surface of a magnetic tape belt 13 while the front surface of magnetic belt 13 is used for imaging and mon...