MULTI-FOCAL LASER SCANNING BAR CODE SYMBOL READING SYSTEM EMPLOYING A VARIABLE SECOND DERIVATIVE SIGNAL PASS-BAND FILTER STRUCTURE HAVING FREQUENCY CHARACTERISTICS THAT ARE CONTROLLED IN A REAL-TIME MANNER BY DETECTING BAR CODE ELEMENTS IN ANALOG SCAN DATA SIGNALS PRODUCED BY SAID SYSTEM
US6540139B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 10, 2000 |
| Grant date | Apr 1, 2003 |
| Priority date | — |
| Expiry date | Feb 10, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K2207/1013
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
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. The control logic circuitry automatically activates the second-derivative zero-crossing detector in response to the detection of the presence of bar code element data encoded within said analog scan data signal, and automatically deactivat…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.