Metrologic Instruments, Inc.

Frank Check

C Harry Knowles

LeRoy Dickson

Xiaoxun Zhu

Mark Lucera

John Groot

Timothy A Good

A diffractive-based laser scanning system that monitors portions of the laser light beams generated by a laser light source (e.g., VLD) employed therein to generate a mode switching signal indicative of a shift in the characteristic wavelength of the laser light beams emitted from the laser light source. In response thereto, a temperature controller selectively heats or cools the laser light source to minimize and avoid such wavelength changes. Mode switching is detected by monitoring a zeroth diffractive order beam produced by a diffractive element of the system. Temperature control of the laser light source is accomplished using active heating elements and passive cooling elements in thermal contact with the laser light source. In addition, temperature control of the laser light source is preferably accomplished over a heating range, whereby temperature within this range is approximated by a look-up table.

Laser scanning system employing laser mode switching using a binary mode switching signal

A bioptical holographic laser scanning system employing a plurality of laser scanning stations about a holographic scanning disc having scanning facets with high and low elevation angle characteristics, as well as positive, negative and zero skew angle characteristics which strategically cooperate with groups of beam folding mirrors having optimized surface geometry characteristics. The system has an ultra-compact construction, ideally suited for space-constrained retail scanning environments, and generate a 3-D omnidirectional laser scanning pattern between the bottom and side scanning windows during system operation. The laser scanning pattern of the present invention comprises a complex of pairs of quasi-orthogonal laser scanning planes, which include a plurality of substantially-vertical laser scanning planes for reading bar code symbols having bar code elements (i.e. ladder-type bar code symbols) that are oriented substantially horizontal with respect to the bottom scanning window, and a plurality of substantially-horizontal laser scanning planes for reading bar code symbols having bar code elements (i.e. picket-fence type bar code symbols) that are oriented substantially vertical with respect to the bottom scanning window.

Bioptical holographic laser scanning system

A holographic laser scanner of ultra-compact design capable of reading bar and other types of graphical indicia within a large scanning volume using holographic optical elements and visible laser diodes. The holographic optical elements are arranged on the scanning disc in such a manner so that none of the laser scanning planes generated within the 3-D scanning volume of the system are spatially and temporally coincident with any other laser scanning plane within the 3-D scanning volume. This novel feature of the present invention ensures that there is substantially zero cross-talk at the plurality of photodetectors provided within the system, significantly improving the performance of the system.

Laser scanning based bar code symbol reading system for producing a 3-D scanning volume substantially free of spatially and temporally coincident laser scanning planes

A diffractive-based laser scanning system of the present invention monitors portions of the laser light beams generated by a laser light source (e.g., VLD) employed therein to generate a mode switching signal indicative of a shift in the characteristic wavelength of the laser light beams emitted from the laser light source. In response thereto, a temperature controller selectively heats (or cool) the laser light source to minimize and avoid such wavelength changes, thereby mitigating any potential problems caused by such wavelength changes. Preferably, mode switching (e.g., change in characteristic wavelength of light emitted from the laser light source) is detected by monitoring a zeroth diffractive order beam produced by a diffractive element of the system. Moreover, temperature control of the laser light source is preferably accomplished using active heating elements (e.g., a heating resistor) and passive cooling elements (e.g., a heat sink) in thermal contact with the laser light source.

Method of and system for detecting and correcting mode switching in diffractive-based laser scanning systems

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 decoe 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.

Laser scanning bar code symbol reader employing variable passband filter structures having frequency response characteristics controlled by time-measurement of laser-scanned bar code symbol elements

Bar code symbol scanning system having multiple scanning stations for producing a 3-D scanning volume free of substantially and temporally coincident scanning planes

Compact bioptical laser scanning system

Disclosed is a bioptical laser scanning system that provides 360&#xb0; of omnidirectional bar code symbol scanning coverage at a point of sale (POS) station. The system generates a 3-D omnidirectional laser scanning pattern between the horizontal and vertical scanning windows during system operation. The laser scanning pattern of the present invention comprises a complex of pairs of quasi-orthogonal laser scanning planes, each composed by a plurality of substantially-vertical laser scanning planes for reading bar code symbols having bar code elements (i.e. ladder-type bar code symbols) that are oriented substantially horizontal with respect to the horizontal scanning window, and a plurality of substantially-horizontal laser scanning planes for reading bar code symbols having bar code elements (i.e. picket-fence type bar code symbols) that are oriented substantially vertical with respect to the horizontal scanning window.

Bioptical laser scanning system providing 360&#xb0; of omnidirectional bar code symbol scanning coverage at a point of sale (POS) station

A holographic laser scanner of ultra-compact design capable of reading bar and other types of graphical indicia within a large scanning volume using holographic optical elements and visable laser diodes. The holographic optical elements are arranged on the scanning disc in such a manner so that none of the laser scanning planes generated within the 3-D scanning volume of the system are spatially and temporally coincident with any other laser scanning plane within the 3-D scanning volume. This novel feature of the present invention ensures that there is substantially zero cross-talk at the plurality of photodetectors provided within the system, significantly improving the performance of the system.

Laser scanning system having multiple laser scanning stations for producing a 3-D scanning volume substantially free of spatially and temporally coincident scanning planes

A bioptical holographic laser scanning system employing a plurality of laser scanning stations about a holographic scanning disc having scanning facets with high and low elevation angle characteristics, as well as positive, negative and zero skew angle characteristics which strategically cooperate with groups of beam folding mirrors having optimized surface geometry characteristics. The system has an ultra-compact construction, ideally suited for space-constrained retail scanning environments, and, generate a 3-D omnidirectional laser scanning pattern between the bottom and side scanning windows during system operation. The laser scanning pattern of the present invention comprises a complex of pairs of quasi-orthogonal laser scanning planes, each composed by a plurality of substantially-vertical laser scanning planes for reading bar code symbols having bar code elements (i.e. ladder-type bar code symbols) that are oriented substantially horizontal with respect to the bottom scanning window, and a plurality of substantially-horizontal laser scanning planes for reading bar code symbols having bar code elements (i.e. picket-fence type bar code symbols) that are oriented substantially vertical with respect to the bottom scanning window.

The improved diffractive-based laser scanning system of the present invention monitors portions of the laser light beams generated by a laser light source (e.g., VLD) employed therein to generate a mode switching signal indicative of a shift in the characteristic wavelength of the laser light beams emitted from the laser light source. In response thereto, a temperature controller selectively heats (or cool) the laser light source to minimize and avoid such wavelength changes, thereby mitigating any potential problems caused by such wavelength changes (for example, unwanted beam distortion and signal processing errors as described above). Preferably, mode switching (e.g., change in characteristic wavelength of light emitted from the laser light source) is detected by monitoring a zeroth diffractive order beam produced by a diffractive element of the system. Moreover, temperature control of the laser light source is preferably accomplished using active heating elements (e.g., a heating resistor) and passive cooling elements (e.g., a heat sink) in thermal contact with the laser light source. In addition, temperature control of the laser light source is preferably accomplished over a heating range (between a minimum heat and maximum heat applied to the laser light source), whereby temperature within this range is approximated by a look-up table. Such a scheme may be implemented by an inexpensive microcontroller, which eliminates the costs for directly measuring the temperature of the laser light source thereby contributing further to a simple and cost-effective design.

Diffractive-based laser scanning system employing microcontroller programmed for mode-switching correction in response to binary mode switching signal generation

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.

ANALOG SCAN DATA SIGNAL PROCESSOR EMPLOYING A TIME-DOMAIN SUBSTRATE NOISE FILTER FOR NON-LINEARLY PROCESSING ANALOG SCAN DATA SIGNALS AND REDUCING SUBSTRATE NOISE SIGNAL LEVELS THEREIN PRIOR TO FIRST DERIVATIVE SIGNAL GENERATION AND PROCESSING OPERATIONS CARRIED OUT WITHIN SAID ANALOG SCAN DATA SIGNAL PROCESSOR

The 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 using a control signal produced by determining the spot speed of the laser scanning beam producing the analog scan data signal being processed. 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.

MULTI-FOCAL LASER SCANNING BAR CODE SYMBOL READING SYSTEM EMPLOYING A SCAN DATA SIGNAL PROCESSOR HAVING A VARIABLE PASS-BAND FILTER STRUCTURE WITH FREQUENCY CHARACTERISTICS CONTROLLED BY MEASURING THE BEAM SPOT SPEED OF THE LASER SCANNING BEAM PRODUCING THE ANALOG SCAN DATA SIGNAL BEING PROCESSED BY SAID SCAN DATA SIGNAL PROCESSOR

A multi-focal zone laser scanning system for scanning bar code symbols having a minimum bar element width (MBW). The multi-focal zone laser scanning system comprises a laser beam producing device for producing a laser beam, and a laser beam scanning mechanism for scanning the laser beam so as to generate a laser scanning pattern having a plurality of different focal zones. In the system, the scanned laser beam has a minimum beam dimension (MBD) with each focal zone, and the ratio of the minimum beam dimension (MDB) within each focal zone to the minimum bar element width (MBW) of a scanned bar code symbol therewithin (i.e. MDB/MBW) is greater than or equal to 2.0. Consequently, less modulation of the laser scanning beam is required during scanning operations, and therefore, bar code symbols having narrower minimum bar element widths can be resolved.

METHOD OF AND SYSTEM FOR SCANNING BAR CODE SYMBOLS USING A LASER SCANNING PATTERN HAVING MULTIPLE FOCAL ZONES, WHEREIN THE MINIMUM BEAM DIMENSION/MINIMUM BAR WIDTH (MBD/MBW) RATIO IS GREATER THAN OR EQUAL TO 2.0

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 deactivates the second-derivative zero-crossing detector, in response to the detection of the absence of bar code element data encoded within the analog scan data signal. By virtue of the present invention, it is now possible to enable the detection of zero-crossings occurring in the second derivative of the analog scan data signals only when bar code element data has been detected, indicative that a bar code symbol has been scanned. This results in more accurate generation of digital output signals from the scan data signal processor.

METHOD OF AND APPARATUS FOR PROCESSING ANALOG SCAN DATA SIGNALS DERIVED BY SCANNING BAR CODE SYMBOLS USING A LASER BEAM, WHEREIN A REAL-TIME BAR CODE ELEMENT DETECTOR IS USED TO CONTROL THE DETECTION OF ZERO-CROSSINGS OCCURRING IN THE SECOND DERIVATIVE OF SAID ANALOG SCAN DATA SIGNALS

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San Jose, CA, United States of America

Frank Check