Abstract: A toner monitor particularly suited for monitoring toner concentration in a two-component development mixture includes an electrically conductive probe mounted in a wall of a development apparatus but the probe does not extend substantially into the developer mixture. A square wave generator or other multifrequency signal source generates a first signal so that electromagnetic energy is carried along the probe and into the mixture. A second signal is generated in response to an impedance mismatch between the mixture and the probe. In response to the second signal, a third signal is generated relating to adjustment of composition content of the development mixture.

Abstract: A monitor for sensing the concentration of toner particles in the development station of an electrostatographic machine, which has a curved sump inner wall surface, includes a solenoid having a coil-form with one end adapted to be positioned adjacent to the outer surface of the sump wall, and a shield at least partially surrounding the solenoid. The shield has an end adjacent to the wall, and the surfaces of the ends of the central coil-form and the shield define a substantially cylindrical surface which conforms to the shape of the inner wall of the sump. Preferably, the surfaces of the ends of the coil-form and the shield are adapted to be substantially equal distant for the inner wall of the sump of a received development station.

Abstract: A densitometer includes a light source positioned to project light rays to a test surface. A photodetector is positioned to receive light rays from the surface, and has an output which is characteristic of the amount of light received. The densitometer includes a voltage source and a photodetector which generates an output signal which is a function of a measured density and of the voltage of the source. A log amp produces a signal which is substantially proportional to the ratio of the output of the photodetector and a second output signal which is also a function of the voltage of the source.

Abstract: Image frame registration apparatus and methods are disclosed which have particular utility in a printing or reproduction apparatus that processes multiple image frames on a transported photosensitive member. Registration indicia for registering an image frame are written on the photosensitive member in an interframe or frame margin area. The indica are composed of discharged line patterns that are readable by a sensor array according to the charge variation or, after toning, the pattern of toned lines therein. The sensor array provides in-track and cross-track signal information to a control unit for synchronizing the electrostatographic processing of the registered image frames. In particular, servo-controlled drive means in the exposure and transfer stations are controlled with precision to provide, after the development and transfer of several registered component images to one or more receivers, an accurate multicolor reproduction.

Abstract: A toner replenishment control structure operates optimally for developer materials which exhibit toning contrast characteristics which vary predictably with the concentration of toner particles in the developer mix, and for developer materials which do not exhibit predictable changes in toning contrast as the toner concentration changes. An electrostatographic machine produces a contrast signal having a value proportional to toning contrast and a concentration signal having a value indicative of the ratio of toner to carrier in the mix, the concentration signal being substantially insensitive to the toning contrast. The system has a first state for actuating replenishment of toner of the first type according to the value of said contrast signal and a second state for actuating replenishment of toner of the second type according to the value of said concentration signal.

Abstract: A toner replenishment control apparatus does not require waiting between replenishment cycles for a period sufficient to insure that the toner in the station is well mixed and charged, and yet does not require artificially limiting the amount of toner added to avoid over-concentration. Information is stored concerning the rates of toner addition in response to a detected concentration error, and the stored information is used in conjunction with future measurements of conconetration error to determine the correct amount of toner needed. More specifically, the replenishment rate is based on (1) the present toner concentration error, (2) an initial replenishment rate which occurred sufficiently prior to insure that the added toner is well mixed and charged, and (3) the toner concentration error which dictated that initial replenishment rate.

Abstract: An electrostatographic machine replenishes the toner in a developer mix proportionally in response to a toner depletion signal having a value indicative of the rate of toner usage. A second signal is produced having a value proportional to toning contrast; and the contrast of proportionality between toner replenishment and the depletion signal is adjusted in response to the second signal value. The toner depletion signal may be indicative of the number of character print signals applied to a print head; the characters preferably being pixels to be toned.

Abstract: A control mechanism for a toner monitor used in an electrographic reproduction apparatus having interchangeable developer stations, respectively containing developer material of different colors, and in which the toner monitor measures reflectivity of the developer material and produces a signal corresponding to the measured reflectivity in order to enable regulation of toner concentration. The mechanism comprises a sensor, associated with a developer station located in the reproduction apparatus, for differentiating between at least two colors of toner and producing signals corresponding respectively to such colors. In response to the corresponding to a particular color, a signal is produced representative of the concentration of toner of that color. The signals respectively representative of toner concentration are substantially equal for like toner concentrations.