Patent ID: 7428999

Claim:
A reader for electro-optically reading symbols located in a range of working distances from the reader, the symbols having bars and spaces of different light reflectivity, each bar and space having widths between respective edges, comprising: means for generating and optically modifying a light beam to have a beam spot in cross-section at a beam waist within the range of working distances; an oscillatable microelectromechanical systems (MEMS) scan mirror having a reflecting surface area for directing the light beam along an outgoing path, and for scanning the beam spot over the symbols for reflection as return light of variable intensity therefrom; a non-retro-reflective collection system for detecting, and for generating an electrical analog signal indicative of, the return light, the system including a photodetector directly facing the symbols, and a collector having a collection aperture area larger than the reflecting surface area for directly collecting and directing a major portion of the return light along a return path to the photodetector, the MEMS mirror being located in the return path and blocking only a minor portion of the return light en route to the photodetector; and a digitizer for resolving the edges even when the widths of the bars and spaces are smaller than the beam spot at far-away distances from the reader within the range of working distances, the digitizer including a differentiator for differentiating the analog signal to generate a first derivative signal, a peak detector for detecting voltage peaks in the first derivative signal, and a comparator for comparing voltage drops after the voltage peaks with a predetermined voltage value, and for determining the presence of each edge when each voltage drop at least equals the predetermined voltage value.