Auto focusing bar code reader
First Claim
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1. An apparatus for use in reading a bar code having a spaced alternating sequence of electromagnetically absorptive and reflective regions along a scan axis at a distance from a target, said apparatus comprising:
- a housing adapted to be manually placed in communication with said bar code having a port for sending and receiving electromagnetic beams;
an electromagnetic signal source located within said housing for providing an electromagnetic illumination beam at a selected frequency and intensity;
an optical train positioned within said housing includingfixed beam shaping optics for receiving and spreading said illumination beam to exit said housing port and irradiating said bar code completely along said scan axis with said housing at a single position relative to said target, andauto-focusing optics for receiving a reflected beam from said bar code and adjusting the focal point of said reflected beam exiting therefrom;
a motor means for adjusting the position of said auto-focusing optics in dependence on received control signals;
a sensor means for receiving said focused reflected beam from said auto-focusing optics and for providing electrical signal equivalents thereof;
a processor means mounted within said housing, receiving said reflected beam electrical signal equivalents, for first generating said auto-focusing optics control signals in accordance with a method comprising the steps of;
detecting maximum and minimum signal magnitudes in said signal equivalents;
digitizing said maximum and minimum signal magnitudes in said signal equivalents;
computing a contrast value for said maximum and minimum signal magnitudes in said signal equivalents;
generating said control signals to move said auto-focusing optics by an amount inversely proportional to the magnitude of said contrast value;
said processor means repeating said method until said control signals have a minimum value wherein the difference between said contrast value and a previously computed contrast value is less than a preselected value and wherein said contrast value is greater than a threshold value;
said processor means, after generating said control signal minimum value, further for subsequently decoding said reflected beam signal equivalents with a method comprising the steps of;
digitizing said signal equivalents;
measuring the width of portions of said digitized signal equivalents along said scan axis corresponding to said electromagnetically absorptive and reflective regions to generate bar code width sequence signals; and
generating an output signal corresponding to an equivalent bar code digit sequence from said bar code width sequence signals.
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Abstract
A device for reading and interpreting bar codes, which illuminates the bar code with a fixed elliptical beam and images the reflected beam onto a CCD array. The black and white bar information is detected by the electronically scanned elements of a linear CCD array. The limited operational range, determined by the optical system depth of focus, is enhanced significantly to a useful operational range by automatically focusing the image of the bar code on the CCD array.
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Citations
19 Claims
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1. An apparatus for use in reading a bar code having a spaced alternating sequence of electromagnetically absorptive and reflective regions along a scan axis at a distance from a target, said apparatus comprising:
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a housing adapted to be manually placed in communication with said bar code having a port for sending and receiving electromagnetic beams; an electromagnetic signal source located within said housing for providing an electromagnetic illumination beam at a selected frequency and intensity; an optical train positioned within said housing including fixed beam shaping optics for receiving and spreading said illumination beam to exit said housing port and irradiating said bar code completely along said scan axis with said housing at a single position relative to said target, and auto-focusing optics for receiving a reflected beam from said bar code and adjusting the focal point of said reflected beam exiting therefrom; a motor means for adjusting the position of said auto-focusing optics in dependence on received control signals; a sensor means for receiving said focused reflected beam from said auto-focusing optics and for providing electrical signal equivalents thereof; a processor means mounted within said housing, receiving said reflected beam electrical signal equivalents, for first generating said auto-focusing optics control signals in accordance with a method comprising the steps of; detecting maximum and minimum signal magnitudes in said signal equivalents; digitizing said maximum and minimum signal magnitudes in said signal equivalents; computing a contrast value for said maximum and minimum signal magnitudes in said signal equivalents; generating said control signals to move said auto-focusing optics by an amount inversely proportional to the magnitude of said contrast value; said processor means repeating said method until said control signals have a minimum value wherein the difference between said contrast value and a previously computed contrast value is less than a preselected value and wherein said contrast value is greater than a threshold value; said processor means, after generating said control signal minimum value, further for subsequently decoding said reflected beam signal equivalents with a method comprising the steps of; digitizing said signal equivalents; measuring the width of portions of said digitized signal equivalents along said scan axis corresponding to said electromagnetically absorptive and reflective regions to generate bar code width sequence signals; and generating an output signal corresponding to an equivalent bar code digit sequence from said bar code width sequence signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18)
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16. An apparatus for use in reading a bar code having a spaced alternating sequence of electromagnetically absorptive and reflective regions along a scan axis at a distance from a target, said apparatus comprising:
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a housing adapted to be manually placed in communication with said bar code having major and minor portions with an acute included angle therebetween, said minor portion having a port for sending and receiving electromagnetic beams; an electromagnetic signal source located within said housing major portion for providing an illumination beam of electromagnetic radiation at a selected frequency and intensity; an optical train positioned within said housing including fixed beam shaping optics for receiving and spreading said beam to exit said housing port and irradiating said bar code completely along said scan axis with said housing at a single position relative to said target; auto-focusing optics for receiving a reflected beam from said bar code along said scan axis and adjusting the focal point of said reflected beam exiting therefrom, and beam turning optics for turning said electromagnetic beams through said housing acute angle; a motor means positioned in said housing minor portion for adjusting the position of said auto-focusing optics in dependence on received control signals; a sensor means positioned in said housing major portion for receiving said focused reflected beam from said auto-focusing optics and for providing electrical signal equivalents thereof; a processor means positioned in said housing major portion and receiving said reflected beam electrical signal equivalents, for first generating said auto-focusing optics control signals in accordance with a method comprising the steps of; detecting maximum and minimum signal magnitudes in said signal equivalents; digitizing said maximum and minimum signal magnitudes in said signal equivalents; computing a contrast value for said maximum and minimum signal magnitudes in said signal equivalents; generating said control signals to move said auto-focusing optics by an amount inversely proportional to the magnitude of said contrast value; said processor means repeating said method until said control signals have a minimum value wherein the difference between said contrast value and a previously computed contrast value is less than a preselected value and wherein said contrast value is greater than a threshold value; said processor means, after generating said control signal minimum value, further for subsequently decoding said reflected beam signal equivalents with a method comprising the steps of; digitizing said signal equivalents; measuring the width of portions of said digitized signal equivalents along said scan axis corresponding to said electromagnetically absorptive and reflective regions to generate bar code width sequence signals; and generating an output signal corresponding to an equivalent bar code digit sequence from said bar code width sequence signals. - View Dependent Claims (17, 19)
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Specification