Focused line identifier for a bar code reader
First Claim
1. A focused line identifier for a bar code reader comprising:
- photodetector means for generating a pattern of analog signal lines representative of illumination of the photodetector means by light reflected from a bar code;
means for selecting a zone within the field of the pattern having the greatest illumination by light reflected from the bar code;
means for locating the line within the selected zone having the sharpest focus of the bar code; and
means for feeding the analog signals in the located line to a digitizer.
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Accused Products
Abstract
A focused line identifier is useful in a bar code reader employing Scheimpflug optics for focusing an illuminated line from the bar code on a two dimensional array of photodetectors. One line or a small group of lines somewhere on the array is the sharpest focus of a bar code within the working range of a bar code scanner. The best focused line is located with the analog signal before digitizing by generating a signal having an amplitude representative of the high frequency component of the lines of signal from the photodetector array. The maximum high frequency component may be found by passing the signal through a high pass filter for detecting the signal having the largest amplitude. The best focused line is, in effect, found in one field scan and used to open a gate in the next scan for passing the best focused line to a digitizer. One may also hop from the best focused line to a line or lines adjacent to the best focuesd line for feeding a slightly unfocused line to the digitizer. Further, a zone within an array of photodetectors which has the greatest illumination may be selected for disregarding spurious signals from other objects that may happen to lie in the field of view of the bar code reader.
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Citations
33 Claims
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1. A focused line identifier for a bar code reader comprising:
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photodetector means for generating a pattern of analog signal lines representative of illumination of the photodetector means by light reflected from a bar code; means for selecting a zone within the field of the pattern having the greatest illumination by light reflected from the bar code; means for locating the line within the selected zone having the sharpest focus of the bar code; and means for feeding the analog signals in the located line to a digitizer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A focused line identifier for a bar code reader comprising:
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a two dimensional photodetector array for generating a pattern of scan lines; means for identifying a line in the array having a maximum high frequency component; and means for gating the identified line to a digitizer for digitizing a bar code signal. - View Dependent Claims (9, 10)
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11. A focused line identifier for a bar code reader comprising:
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means for generating a pattern of a vertical plurality of horizontal scan lines representative of illumination of an area by light reflected from a bar code; analog means for identifying a line in the pattern with the sharpest focus of light reflected from the bar code; and means for gating the pattern to a digitizer during an interval corresponding substantially to the identified line. - View Dependent Claims (12, 13, 14)
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15. A focused line identifier for a Scheimpflug optics bar code reader comprising:
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photodetector means for generating a pattern of signals comprising a vertically extending plurality of horizontal scan lines including an image of a bar code from a Scheimpflug optical system; a high pass filter for passing a high frequency component of the scan lines; means connected to the filter for generating a signal representative of the amplitude of the high frequency component in each scan line during a scan across the pattern; a first peak detector responsive to the amplitude; a second peak detector responsive to the amplitude; means for resetting the first peak detector every scan across the array and for resetting the second peak detector every second scan across the array; and means for gating at least one line to a digitizer when the first and second peak detectors both record a maximum amplitude during such a second scan across the array. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 33)
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24. A focused line identifier for a bar code reader comprising:
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photodetector means for generating a pattern of a vertical plurality of horizontal scan lines, at least one of the lines being illuminated by light reflected from a bar code; auxiliary means at an end of the photodetector means subdividing the photodetector means into a plurality of zones of lines; and means for identifying the auxiliary means having the maximum illumination by light reflected from a bar code. - View Dependent Claims (25, 26)
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27. A method for operating a bar code reader having a two dimensional array of photodetectors for generating a train of signals representing scan lines across the array comprising the steps of:
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identifying by analog means a line in the train of signals having the sharpest focus of light reflected from the bar code onto the array of photodetectors; and gating a train of signals representing the identified line to a digitizer. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification