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AssigneeMetrologic Instruments, Inc.
InventorsMARK G. LUCERA, C. HARRY KNOWLES, XIAOXUN ZHU, LEROY DICKSON
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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. Only spectral components associated with the produced analog scan data signal and noise existing over this pass-band are allowed within the analog signal processor. By virtue of the present invention, first and second derivative signals can be generated and processed to produce a corresponding digital scan data signal for use in subsequent digitizing and decode processing operations, without compromising system performance due to the destructive effects of thermal and substrate noise outside the spectral pass-band of interest for the bar code symbol being scanned.
A laser scanning system, wherein without increasing or otherwise changing the laser beam power characteristics, the length of each focal zone in the system can be increased to allow either more overlap between adjacent focal zones, or a larger overall depth of field.
A laser scanning system that has an increased depth of field without increasing the power level of the laser scanning beams, or adding additional focal zones to the system.
A laser scanning system which employs a scan data signal processor having a plurality of pass-band filter structures that are electronically-switched in response to control signals derived from information about the focal distance of the laser beam scanning a bar code symbol at each instant in time and producing a corresponding analog scan data signal which requires processing.
A multi-focal zone laser scanning bar code symbol reading system, wherein each scan data producing channel includes a scan data signal processor that employs a variable pass-band filter that is dynamically controlled by the focal distance of the laser scanning beam producing the analog scan data signal being processed in a real-time manner.
A multi-focal zone laser scanning bar code symbol reading system, in which the ratio of the minimum laser beam cross-section dimension (MBD) to the minimum bar element width (MBW) in each focal zone of the system is greater than or equal to 2.0.
A multi-focal zone laser scanning system, wherein a scan data signal processor is used having a higher overall signal-to-noise ratio (SNR), thereby requiring less modulation of the laser scanning beam during scanning operations, and decreasing the effective laser beam diameter (i.e. beam spot size) at each focal zone in the system, and thus increasing the bar code scanning resolution of the system.
A multi-focal zone scanning system, wherein without increasing or otherwise changing the laser beam power characteristics, the length of each focal zone in the system can be increased to allow either more overlap between adjacent focal zones, or a larger overall depth of field in the system.
A laser scanning system that has an increased depth of field without increasing the power level of the laser scanning beams, or adding additional focal zones to the system.
A laser scanning system which employs a scan data signal processor having a plurality of first derivative signal pass-band filter structures that are electronically-switched into operation in response to control signals derived from information about the focal distance of the laser scanning beam at each instant in time.
A multi-focal zone laser scanning bar code symbol reading system, wherein
A laser scanning bar code symbol reader employing a variable first derivative signal pass-band filter structure having frequency characteristics that are controlled in a real-time manner by measuring the time duration of binary signal levels in digital scan data signals produced in response to laser scanning bar code symbol elements located within the scanning range of the system.
A laser scanning bar code symbol reader employing a variable second derivative signal pass-band filter structure having frequency characteristics that are controlled in a real-time manner by measuring the time duration of binary signal levels in digital scan data signals produced in response to laser scanning bar code symbol elements located within the scanning range of the system.
A laser scanning bar code symbol reading system, wherein time measurement of bar code symbol elements is carried out using an application specific integrated circuit (ASIC) chip that compares real-time measurement of binary signal levels in digital scan data signals with predetermined time measures thereof, stored in an EPROM or like device, for bar code symbols of different resolutions and scanning distances from the bar code symbol reading system.
A bar code symbol reading system, wherein a rotating polygon-type mechanism is used to scan the laser scanning beam over the scanning field or volume of the system.
A bar code symbol reading system, wherein a variable laser beam focusing mechanism and rotating polygon-type mechanism are used to produce an X-bar or like laser scanning pattern at varying depths of focus over the scanning field of the system.
A laser scanning bar code symbol reading system mounted over a high-speed conveyor-belt system in order to identify packages, parcels and the like transported therealong in a highly reliable manner.
Dependencies are inferred from the claim text.