Bar code symbol scanning system employing time-division multiplexed laser scanning and signal processing to avoid optical cross-talk and other unwanted light interference
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Abstract
A laser scanning system that employs synchronous time-division-multiplexed laser scanning operations and signal processing operations (for bar code detection). A plurality of successive non-overlapping time slots are defined and logically assigned to a unique laser scanning beam and corresponding photosensor. During a given time slot, the laser scanning beam logically assigned thereto is selectively generated (or selectively projected) into the scanning volume while generation (or projection) of the other laser scanning beam is disabled. Moreover, during the given time slot, the photosensor logically assigned thereto is operably coupled to signal processing circuitry that performs bar code detection operations on the data signals derived therefrom while the other photosensor is operably decoupled from such signal processing circuitry. The frequency of time slots logically assigned to a given laser scanning beam and corresponding photosensor is preferably greater than at least two times the highest frequency component expected in the scan data signal received at the photosensor. In other embodiments, the time slots logically assigned to a given laser scanning beam and corresponding photosensor correspond to scanning planes (or scanning plane groups) generated by the given laser scanning beam during revolution of at least one rotating polygonal mirror. In the preferred embodiment, such synchronous time-division-multiplexed laser scanning operations and signal processing operations (for bar code detection) are embodied in a bioptical laser scanning system comprising a plurality of laser scanning stations, each of which produces a plurality of groups of quasi-orthogonal laser scanning planes that are projected within predetermined regions of space contained within a 3-D scanning volume defined between the bottom and side-scanning windows of the system.
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Citations
76 Claims
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1-50. -50. (canceled)
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51. A bar code symbol scanning system comprising:
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at least one laser light source for generating a plurality of laser scanning beams;
optical elements for projecting said plurality of laser scanning beams into a scanning volume at different orientations for scanning one or more bar code symbols on objects within the scanning volume, collecting light reflections from said laser scanning beams, and directing these light reflections to a plurality of photosensors corresponding in number to the plurality of laser scanning beams and producing electrical signals corresponding to light reflections from the scanned bar code symbols;
signal processing circuitry operably, coupled to the output of said photosensors, for processing said electrical signals and detecting and decoding the bar code symbols scanned by the laser scanning beams;
timing signal generation circuitry for generating timing signals that correspond to successive non-overlapping time slots, wherein each said laser scanning beam and corresponding photosensor is logically assigned to one of said successive non-overlapping time slots;
a laser light source control mechanism for operating, during a given time slot, in response to the timing signals generated by said timing signal generation circuitry, so as to selectively enable one said laser scanning beam, logically assigned to the given time slot, to be generated and/or projected into said scanning volume; and
a signal processing control mechanism for operating, during the given time slot, in response to the timing signals generated by said timing signal generation circuitry, so as to selectively enable one said photosensor, logically assigned to the given time slot, to be operably coupled to said signal processing circuitry. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76)
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Specification