Abstract: An analog scan data signal processor is disclosed, in which a time-domain non-linear substrate noise filter is provided before a first derivative signal generation stage so as to produce, as output, a substantially fixed zero-reference signal level whenever a signal level indicative of a bar code substrate is detected, and the signal level analog scan data signal, whenever a signal level indicative of a bar code element is detected. By virtue of the present invention, it is now possible to reduce the level of substrate noise signals within input analog scan data signals, prior to deriving first derivative signals for subsequent signal processing. Consequently, the accuracy of binary signal level detection within such analog scan data signal processors can be significantly improved, thereby improving the performance of bar code symbol reading systems within which such analog scan data signal processors are employed.

Abstract: A scan data signal processor is disclosed for use with a laser scanning system having a plurality of different focal zones within which a laser scanning beam is scanned across one or more bar code symbols and an analog scan data signal is automatically produced. The scan data signal processor comprises a first and second derivative signal generation stages, a second-derivative zero-crossing detector, a real-time bar code element detector, and a control logic circuitry. The first derivative signal generation stage derives a first derivative signal from the analog scan data signal. The second derivative signal generation stage derives a second derivative signal from the first derivative signal. The second-derivative zero-crossing detector detects zero crossings in said second derivative signal. The real-time bar code element detector automatically detects the presence and absence of bar code element data encoded within said analog scan data signal.

Abstract: The effects of paper/substrate noise are significantly reduced in multi-focal zone laser scanning systems by processing analog scan data signals with a scan data signal processor having a plurality of pass-band filters and amplifiers 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 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.

Abstract: The effects of paper/substrate noise are significantly reduced in multi-focal zone laser scanning systems by processing analog scan data signals with a scan data signal processor having a plurality of pass-band filters and amplifiers 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 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.

Abstract: The effects of paper/substrate noise are significantly reduced in multi-focal zone laser scanning systems by processing analog scan data signals with a scan data signal processor having a plurality of pass-band filters and amplifiers 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 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.

Abstract: The effects of paper/substrate noise are significantly reduced in multi-focal zone laser scanning systems by processing analog scan data signals with a scan data signal processor having a plurality of pass-band filters and amplifiers 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 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.