Method and apparatus for extending operating range of bar code scanner
First Claim
Patent Images
1. An imaging system for imaging an object located in a target region, comprising:
- an illumination source;
an optical path between said illumination source and said object;
a first optics assembly in said optical path;
phase masking means in said optical path for receiving light and modifying a phase thereof as a function of position within said phase masking means, thereby creating phase modified light having known effects therein;
means for traversing said phase modified light across said object in said target region;
image sensing means for receiving light reflected from said object and producing an intermediate image signal therefrom;
said intermediate image signal including at least a misfocus error that is dependent upon a distance between said first optics assembly and said object; and
processing means for correcting for said known effects of said phase modified light to produce a final image signal of said object.
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Abstract
Briefly stated, the operating depth of field for a bar code scanner, preferably a laser scanner, is increased by placing a cubic phase mask (CPM) in the scanning beam. The masked beam is then scanned and reflected off a bar code and received by a photodetector. The received signal is then processed to recover the original unperturbed representation of the bar code pattern. The processed signal has an increased depth of field over an unmasked scanner signal.
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Citations
34 Claims
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1. An imaging system for imaging an object located in a target region, comprising:
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an illumination source;
an optical path between said illumination source and said object;
a first optics assembly in said optical path;
phase masking means in said optical path for receiving light and modifying a phase thereof as a function of position within said phase masking means, thereby creating phase modified light having known effects therein;
means for traversing said phase modified light across said object in said target region;
image sensing means for receiving light reflected from said object and producing an intermediate image signal therefrom;
said intermediate image signal including at least a misfocus error that is dependent upon a distance between said first optics assembly and said object; and
processing means for correcting for said known effects of said phase modified light to produce a final image signal of said object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. An imaging system for imaging an object located in a target region, comprising:
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a laser illumination source;
a first optical path between said laser illumination source and said object;
a first optics assembly in said first optical path;
a cubic phase mask in said first optical path between said first optics assembly and said object within 0.5 inches of said first optics assembly for receiving light and modifying a phase thereof as a function of position within said cubic phase mask, thereby creating phase modified light having known effects therein;
an amplitude mask in said first optical path;
means for moving said phase modified light across said object;
a photodetector for receiving light reflected from said object and producing an intermediate image signal therefrom;
said intermediate image signal including at least a misfocus error that is dependent upon a distance between said first optics assembly and said object;
a second optics assembly in a second optical path between said object and said photodetector; and
processing means for correcting for said known effects of said phase modified light to produce a final image signal of said object.
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31. A method of scanning for a laser scanning system suited for reading indicia located in a target region, comprising the steps of:
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generating an illumination beam for illuminating an indicia located in an operational depth of field;
changing locally a phase of said illumination beam as a function of position before said beam illuminates said indicia;
changing locally an amplitude of said illumination beam as a function of position before said beam illuminates said indicia;
receiving light reflected from said indicia;
converting the received light to an intermediate image signal; and
processing said intermediate image signal such that said operational depth of field is extended.
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32. A method of modifying a laser beam to maximize the system resolving ability as a bar code indicia is moved throughout an operational depth of field, comprising the steps of:
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generating a laser illumination beam;
modifying a phase of said illumination beam a function of position in said beam;
modifying an amplitude of said illumination beam as a function of position in said beam;
scanning said phase and amplitude-modified beam across said bar code indicia;
receiving light reflected from said bar code indicia;
converting the received light to an intermediate image signal; and
processing said intermediate image signal using a precalculated recovery function to reduce effects of a position of said bar code indicia.
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33. A method of scanning a barcode indicia, said indicia containing information encoded therein, comprising the steps of:
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illuminating said indicia in an operating range with light;
modifying an amplitude and phase of said light to reduce variations in a localized illumination distribution of said light over said operating range before said light illuminates said indicia;
directing said light to said operating range;
scanning said light across said indicia;
receiving light scattered from said indicia;
converting said scattered light to an intermediate image signal; and
processing said intermediate image signal to recover said information encoded in said indicia.
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34. A method of increasing an operating depth of field, comprising:
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providing illumination;
distorting a phase of said illumination in a predetermined manner at a specific distance from an object;
directing said distorted illumination to said object;
receiving light scattered from said object;
converting said received light to an intermediate image signal; and
processing said intermediate image signal using a precalculated recovery function to reduce effects of said specific distance.
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Specification