Patent ID: 6481625
Filing Date: 2002-11-19
Classification: G02B,G06K,G07F,G07G

Abstract:
A multi-focal zone laser scanning system comprising:a scanner housing; a laser scanning beam mechanism disposed within said scanner housing, for producing laser scanning beam and scanning said laser beam so as to produce laser scanning pattern that is focused along a plurality of different predefined focal zones, and automatically generating an analog scan data signal corresponding to the structure of a bar code symbol structure scanned by said scanned laser beam; a scan data signal processor for processing said analog scan data signal, and including a first derivative signal generator for receiving said analog scan data signal and generating a first derivative signal representative of the first time-derivative of said analog scan data signal, a plurality of pass-band filter structures, each one of said plurality of pass-band filter structures being preassigned to one of said predefined focal zones and having frequency response characteristics for optimally filtering said first derivative signal produced while said scanned laser beam scans said bar code symbol structure within said predefined focal zone, and control circuitry for dynamically switching one of said plurality of pass-band filter structures into operation so that said first derivative signal produced in response to said laser beam scanning said bar code symbol within one of said predefined focal zones is optimally filtered by said dynamically-switched pass-band filter structure preassigned to said predefined focal zone; a bar code element width measurement processor for measuring in real-time the width of the signal levels in said analog scan data signals, and producing signal level width measurement data representative thereof; and a data processor for converting said signal level width measurement data into control signals for use by said control circuitry so that one of said plurality of pass-band filter structures is automatically switched into operation so that said first derivative signal produced in response to said laser beam scanning said bar code symbol within one of said predefined focal zones is optimally filtered by said dynamically-switched pass-band filter structure preassigned to said predefined focal zone.