An optical scanning system is provided for producing a signal representative of a spatial distribution of indicia having different degrees of reflectivity to light, such as a bar code (14).
The invention further relates to a method of reading an indicia where the electrical signal representative of the indicia is selectively sampled, the samples being analyzed to establish whether they will represent true data or noise, and signal collection, processing and sampling is then adjusted allowing more aggressive decoding techniques to be used. In another aspect, a non-linear edge strength digitizer is employed capable of decoding both poorly printed and high density bar codes. A matched filter for bar code symbol signals is also proposed; as there is no inherent synchronisation in the bar code signals, a peak or edge detector is used to trigger the system. An automatic deblurring signal processor also proposed wherein a first derivative of an input bar code signal is compared against a threshold range and, if no match is found, then parameters of the processor system are varied to increase the likelihood of a comparison being successful.