Discrimination circuit arrangements

摘要

A discrimination circuit operable to discriminate between an input signal in the form of a pedestal and disturbance signals superimposed thereon has an A-D converter to digitize a disturbance-free reference pedestal signal, circulating shift register to store the digitized reference signal, a D-A converter to produce a pedestal signal from the reference signal, a controlling clock to shift the reference signal in the store in synchronism with the incoming signal such that the two pedestal signals are available together, and a comparator to compare the reference signal with the input signal to produce an output caused by differences due to disturbances. The circuit forms part of an optical surface inspection apparatus.