A repetitive surface detector includes an image capture device capturing
an image. An autocorrelator receives the image and generates a signal
indicative of a repetitive background of the image. A controller
determines a maximum and minimum value in the auto-correlated signal. An
adder determines the signed difference between the maximum and minimum
value. A comparator compares the signed difference with a threshold and
generates an output that indicates when the image includes a repetitive
background.