Browse Prior Art Database

Original Publication Date: 1977-Aug-31
Included in the Prior Art Database: 2004-Mar-30

Publishing Venue

Xerox Disclosure Journal


In the development system of an electrophotographic printing machine, dispensing of additional toner particles into the developer mixture is controlled to maintain the concentration thereof substantially optimum. As shown in the drawing, toner particles descend between plates 62 and 64. Light source 72 illuminates plates 62 and 64, plates 62 and 64 are alternately electrically biased to a suitable potential attracting toner particles thereto. The light rays from light source 72 are transmitted through plate 62 and 64 and detected by photosen-sors 74 and 76. The peak transmittance of optical filter 78 corresponds to the peak transmittance of the toner particles passing between plate 64 and 62. Contrawise, the peak trans-mittance of optical filter 80 corresponds to the peak absorb-ance of the toner particles passing therebetween, Electrical output signals are processed to obtain the ratio of the electrical signal between photosensors 74 and 76. Thereafter, the anti-log of this resultant signal is determined. The resultant linear signal is substantially insensitive to devel-oper flow and provides greater control accuracy. This signal is compared to a reference signal which, in turn, results in an error signal for controlling the dispensing of toner par-ticles into the developer material.