A simplified system for sensing the movement and/or position on both axes of a
moving surface, such as a photoreceptor belt of a xerographic printer, or a sheet
transport of an ink jet printer, utilizing a linear track of small and closely
spaced "Z" shaped marks on or in a moving belt or roller surface. These marks are
used to accurately incrementally directly detect surface motions in both orthogonal
axes with a co-linear optical sensor linear array of a multiplicity of individual
pixel optical detectors which respectively detect and compare the changes in positions
relative thereto of the transverse and angled lines of those Z marks during frequent
short measurement intervals. This exemplary system provides direct, and thus more
accurate, surface movement measurement information, with much less critical and
less costly marking requirements, and greater tolerance for variations in the subject
surface, as compared to indirect or conventional encoder type positional sensors.
