Patent ID: 8570587

Claim:
An apparatus to measure the speed of a moving imaging surface having a primary movement direction, the apparatus comprising: marking means for providing a plurality of reference patterns formed of slant lines provided on the moving surface, wherein the marking means includes means for creating and developing an electrostatic image on the imaging surface; a sensor to detect the plurality of reference patterns being moved on the moving surface, wherein the sensor produces a timestamp when it detects a reference pattern; an encoder comprising at least one encoder roll associated with the moving imaging surface, the encoder generating encoder pulses; an ROS master clock to generate discrete clock pulses; and a logic circuit coupled to the sensor, the encoder, and the master clock to determine the speed of the moving surface by: counting the number of encoder pulses generated by the encoder between a first timestamp and a second timestamp; determining a leading fractional encoder count relative to the first timestamp; determining a trailing fractional encoder count relative to the second timestamp; and determining an elapsed interval of time between the first timestamp and the second timestamp; wherein the reference patterns being spaced along the moving imaging surface by a predetermined distance substantially corresponding to a circumference of the encoder roll.