IMPROVED SCAN DATA SIGNAL PROCESSORS FOR LASER SCANNING CODE SYMBOL READING SYSTEMS

摘要

The effects of paper/substrate noise are significantly reduced in multifocal zone laser scanning systems (1) by processing analog scan data signals with a scan data signal processor having a plurality of pass-band filters and amplifiers (13A-13D) that are automatically selected for passing only the spectral components of an analog scan data signal produced when a bar code symbol is scanned at a particular focal zone (FZ1-FZ5) in the laser scanning system. Two or more different pass-band filter structures can be provided for use in the scan data signal processor, wherein each pass-band filter structure is tuned to the spectral band associated with a particular focal zone in the laser scanning system. When a bar code symbol is scanned by a laser beam focused within the first focal zone or scanning range of the system, the pass-band filter structure associated with this focal zone or scanning range is automatically switched into operation.