Reduction of banding and mottle in electrophotographic systems

a b a b A mechanism and process for detecting mottle or banding in a developed electrophotographic image. Within an electrophotographic reproduction apparatus , a photoconductor is used for receiving and developing a latent image. The photoconductor traverses a path that passes a charging station , an exposure station , a toning station , and a transfer station . Either a densitometer for measuring the density of the developed image on the photoconductor, or an electrometer or for detecting the voltage of the image on the photoconductor, detects mottle or banding on the developed image. The densitometer or electrometer or has an aperture small enough to detect mottle or banding with wavelengths perceptible by human eyes. A logic and control unit averages the image density or voltage measurements, calculates the variations of the measurements about the average and the periodicities of the measurements, and if the variations or periodicities indicate mottle or banding is present, changes the operation of one or more stations to reduce mottle or banding.