A control system for an image forming device includes a sensor mounted on an
optical
path unobstructed by elements that are subject to wear for detecting a time varying
signal representing reflected light from both a photoconductive element and a transfer
sheet internal to the image forming device, a memory storing reference values,
and a controller to control an image forming operation based on the reference values
stored in the memory and the time-varying signal received from the sensor. The
controller reads the time-varying signal from the sensor and compares the time-varying
signal read to the reference values to determine a condition of the image forming device.
