Analog-to-digital image signal conversion

摘要

A system for converting an analog image signal into a digital image signal is provided. The system comprises an analog-to-digital signal converter for producing a digital signal by subjecting an incoming analog signal to threshold processing with a threshold level. The system also comprises a peak/valley extracting circuit for extracting peak and valley points corresponding to thin lines and narrow gaps between lines, respectively, in the original image scanned. The extracted peak and valley points are utilized in the analog-to-digital conversion processing so as not to lose information as to thin lines and narrow gaps between lines. Especially, in extracting peak and valley points, the concentration or level of a particular picture element is compared with that of the adjacent picture elements at least in two directions.