A mechanism and process for detecting mottle or banding in a developed electrophotographic
image. Within an electrophotographic reproduction apparatus 10, a photoconductor
is used for receiving and developing a latent image. The photoconductor traverses
a path that passes a charging station 28, an exposure station 34,
a toning station 38, and a transfer station 46. Either a densitometer
76 for measuring the density of the developed image on the photoconductor,
or an electrometer 50a or 50b for detecting the voltage
of the image on the photoconductor, detects mottle or banding on the developed
image. The densitometer 76 or electrometer 50a or 50b
has an aperture small enough to detect mottle or banding with wavelengths perceptible
by human eyes. A logic and control unit 24 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.
