Digitizer for bar code reader

摘要

A multi-bit digitizer for a bar code reader for detecting and reading bar code symbols, which are generally printed on a label or on the surface of an article. The multi-bit digitizer detects the presence of edges of a scanned bar code symbol, and also measures the strength of each detected edge therein. During a scanning operation, a sensor senses light reflected from a bar code symbol and produces an analog scan signal representative thereof. Positive and negative edges in the analog scan signal are detected, and timing signals are developed representative thereof. The strength of each detected edge in the analog scan signal is determined by measuring the pulse-widths of the timing signals. A separate edge-direction signal is also developed which indicates the nature of the edge. The signals are directed as inputs to a decoder which performs multiple threshold processing on each individual analog scan signal by processing each analog scan signal a multiple number of times at different detection threshold levels. The ability to perform multiple thresholding on a single scan is significant for the development of very aggressive wands in which only a single scan is available for processing.