EP0449645A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Locating bar code symbols
Assignee: Omniplanar Inc
•
Filing: 1991-03-28
•
Granted: —
•
Expires: 2011-03-28
Abstract
Abstract A bar code reader (10) includes an optical system (26, 28) for storing a two dimensional image in memory (32), which stored two dimensional image contains a bar code symbol. A method and apparatus is disclosed for detecting the location of the bar code image by computing the accumulated sum (64) of the products of the derivatives (62) of respective first and second scan lines (60) as a location score (68) for the image under consideration. The higher the location score, the higher the probability that the area under consideration contains a bar code image. Also, a method and apparatus is disclosed (Fig. 5B) for determining the fine orientation of a located bar code image by the cross-correlation of interpolated scan line data. The bar code image is filtered by shifting interpolated scan line data in accordance with the detected peak of the cross-correlation and combining the shifted scan line data.
Inventors
- 👤 Donald G. Chandler
- 👤 Eric P. Batterman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 11:44
CPC Classifications
G; G06; G06K; G06K7/00; G06K7/10; G06K7/10544; G06K7/10821; G06K7/10861; G06K7/10871; G06K7/1093; G06K7/14; G06K7/1404; G06K7/1439; G06K7/1443; G06K7/1456; G06K7/146; G06K7/1491
Claims Analysis
Total Claims: 44
Claim 1
Independent Claim
191 words
In a bar code reader, a method for detecting the location of a bar code symbol comprising: capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; approximating the derivative of a first scan line in a given area of said stored two dimensional image; approximating the derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; and accumulating the sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score for said stored two dimensional image, wherein said location score represents the relative likelihood that said given area of said stored two dimensional image contains a bar code image.
Claim 2
Dependent Claim
83 words
A method in accordance with claim 1, for detecting the location of a bar code symbol, wherein said steps of approximating the derivatives of said first and second scan lines respectively comprises: subtracting a previous pixel value from a present pixel value along said first scan line to determine the approximate derivative of said first scan line; and subtracting a previous pixel value from a present pixel value along said second scan line to determine the approximate derivative of said second scan line.
Claim 3
Dependent Claim
60 words
A method in accordance with claim 1 or 2, for detecting the location of a bar code symbol further comprising: determining whether said location score corresponding to said given area exceeds a predetermined threshold, wherein said location score exceeding said predetermined threshold is an indication that said given area of said stored two dimensional image contains a bar code image.
Claim 4
Dependent Claim
68 words
A method in accordance with claim 1 or 2, for detecting the location of a bar code symbol further comprising: storing respective location scores for a plurality of areas of said stored two dimensional image; and determining by region growing, which of said plurality of areas of said stored two dimensional image have respective location scores which correspond to a region which includes said located bar code image.
Claim 5
Dependent Claim
152 words
In a bar code reader, a method for determining the orientation of a bar code symbol comprising: capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; interpolating a first scan line in a given area of said stored two dimensional image; interpolating a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; calculating the cross-correlation function of said interpolated first scan line data and said interpolated second scan line data; and detecting the peak of said cross-correlation function of said first and second interpolated scan line data, wherein the position of said peak of said cross-correlation function of said interpolated first and second scan line data corresponds to the orientation of said bar code image.
Claim 6
Dependent Claim
47 words
A method in accordance with claim 5, further comprising: shifting said interpolated second scan line data so as to be aligned with said interpolated first scan line data in accordance with said detected peak of said cross-correlation function of said interpolated first and second scan line data.
Claim 7
Dependent Claim
54 words
A method in accordance with claim 5, for determining the orientation of a bar code symbol further comprising: interpolating a plurality of scan lines in said given area of said stored two dimensional image; and calculating the respective cross-correlation function of selected pairs of interpolated scan lines from said plurality of interpolated scan lines.
Claim 8
Dependent Claim
23 words
A method in accordance with claim 7, further comprising: shifting said interpolated plurality of scan line data respectively so as to be aligned.
Claim 9
Dependent Claim
32 words
A method in accordance with claim 8, further comprising: filtering said bar code image by taking the average of corresponding data points from said plurality of shifted and interpolated scan line data.
Claim 10
Dependent Claim
32 words
A method in accordance with claim 8, further comprising: filtering said bar code image by taking the median of corresponding data points of said plurality of shifted and interpolated scan line data.
Claim 11
Dependent Claim
64 words
A method in accordance with claim 8, further comprising: filtering said bar code image by taking the weighted average of corresponding data points of said plurality of shifted and interpolated scan line data, said average being weighted according to the magnitude of said cross-correlation function between said plurality of said respective interpolated scan line data and said plurality of interpolated first scan line data.
Claim 12
Dependent Claim
31 words
A method in accordance with claim 7 or 8, further comprising: filtering said bar code image by combining corresponding data points of said shifted and interpolated plurality of scan line data.
Claim 13
Dependent Claim
39 words
A method in accordance with claim 12, further comprising: converting said filtered bar code image to a binary function using the average value of said combined shifted and interpolated plurality of scan line data as the binary threshold value.
Claim 14
Dependent Claim
201 words
In a bar code reader, an apparatus for detecting the location of a bar code symbol comprising: means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for approximating the derivative of a first scan line in a given area of said stored two dimensional image; means for approximating the derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; and means for accumulating the sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score for said stored two dimensional image, wherein said location score represents the relative likelihood that said given area of said stored two dimensional image contains a bar code image.
Claim 15
Dependent Claim
87 words
An apparatus in accordance with claim 14, for detecting the location of a bar code symbol, wherein said means for approximating the derivatives of said first and second scan lines respectively comprises: means for subtracting a previous pixel value from a present pixel value along said first scan line to determine the approximate derivative of said first scan line; and means for subtracting a previous pixel value from a present pixel value along said second scan line to determine the approximate derivative of said second scan line.
Claim 16
Dependent Claim
62 words
An apparatus in accordance with claim 14 or 15, for detecting the location of a bar code symbol further comprising: means for determining whether said location score corresponding to said given area exceeds a predetermined threshold, wherein said location score exceeding said predetermined threshold is an indication that said given area of said stored two dimensional image contains a bar code image.
Claim 17
Dependent Claim
72 words
An apparatus in accordance with claim 14 or 15, for detecting the location of a bar code symbol further comprising: means for storing respective location scores for a plurality of areas of said stored two dimensional image; and means for determining by region growing, which of said plurality of areas of said stored two dimensional image have respective location scores which correspond to a region which includes said located bar code image.
Claim 18
Dependent Claim
162 words
In a bar code reader, an apparatus for determining the orientation of a bar code symbol comprising: means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for interpolating a first scan line in a given area of said stored two dimensional image; means for interpolating a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for calculating the cross-correlation function of said interpolated first scan line data and said interpolated second scan line data; and means for detecting the peak of said cross-correlation function of said first and second interpolated scan line data, wherein the position of said peak of said cross-correlation function of said interpolated first and second scan line data corresponds to the orientation of said bar code image.
Claim 19
Dependent Claim
49 words
An apparatus in accordance with claim 18, further comprising: means for shifting said interpolated second scan line data so as to be aligned with said interpolated first scan line data in accordance with said detected peak of said cross-correlation function of said interpolated first and second scan line data.
Claim 20
Dependent Claim
59 words
An apparatus in accordance with claim 18, for determining the orientation of a bar code symbol further comprising: means for interpolating a plurality of scan lines in said given area of said stored two dimensional image; and means for calculating the respective cross-correlation function of selected pairs of interpolated scan lines from said plurality of said interpolated scan lines.
Claim 21
Dependent Claim
25 words
An apparatus in accordance with claim 20, further comprising: means for shifting said interpolated plurality of scan line data respectively so as to be aligned.
Claim 22
Dependent Claim
34 words
An apparatus in accordance with claim 21, further comprising: means for filtering said bar code image by taking the average of corresponding data points from said plurality of shifted and interpolated scan line data.
Claim 23
Dependent Claim
34 words
An apparatus in accordance with claim 21, further comprising: means for filtering said bar code image by taking the median of corresponding data points of said plurality of shifted and interpolated scan line data.
Claim 24
Dependent Claim
57 words
An apparatus in accordance with claim 28, further comprising: means for filtering said bar code image by taking the weighted average of corresponding data points of said plurality of shifted and interpolated scan line data, said average being weighted according to the magnitude of said cross-correlation function between said plurality of said respective interpolated scan line data.
Claim 25
Dependent Claim
33 words
An apparatus in accordance with claim 20 or 21, further comprising: means for filtering said bar code image by combining corresponding data points of said shifted and interpolated plurality of scan line data.
Claim 26
Dependent Claim
41 words
An apparatus in accordance with claim 25, further comprising: means for converting said filtered bar code image to a binary function using the average value of said combined shifted and interpolated plurality of scan line data as the binary threshold value.
Claim 27
Dependent Claim
148 words
In a bar code reader, a method for determining the orientation of a bar code symbol comprising: capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; selecting a first scan line in a given area of said stored two dimensional image; selecting a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; calculating the cross-correlation function of said selected first scan line and said selected second scan line; and detecting the peak of said cross-correlation function of said first and second selected scan lines, wherein the position of said peak of said cross-correlation function of said selected first and second scan lines corresponds to the orientation of said bar code image.
Claim 28
Dependent Claim
44 words
A method in accordance with claim 27, further comprising: shifting said selected second scan line so as to be aligned with said selected first scan line in accordance with said detected peak of said cross-correlation function of said selected first and second scan lines.
Claim 29
Dependent Claim
56 words
A method in accordance with claim 27 or 28, for determining the orientation of a bar code symbol further comprising: selecting a plurality of scan lines in said given area of said stored two dimensional image; and calculating the respective cross-correlation function of selected pairs of selected scan lines from said plurality of selected scan lines.
Claim 30
Dependent Claim
22 words
A method in accordance with claim 29, further comprising: shifting said selected plurality of scan lines respectively so as to be aligned.
Claim 31
Dependent Claim
31 words
A method in accordance with claim 30, further comprising: filtering said bar code image by taking the average of corresponding data points from said plurality of shifted and selected scan lines.
Claim 32
Dependent Claim
31 words
A method in accordance with claim 30, further comprising: filtering said bar code image by taking the median of corresponding data points of said plurality of shifted and selected scan lines.
Claim 33
Dependent Claim
61 words
A method in accordance with claim 30, further comprising: filtering said bar code image by taking the weighted average of corresponding data points of said plurality of shifted and selected scan lines, said average being weighted according to the magnitude of said cross-correlation function between said plurality of said respective selected scan lines and said plurality of selected first scan lines.
Claim 34
Dependent Claim
30 words
A method in accordance with claim 29 or 30, further comprising: filtering said bar code image by combining corresponding data points of said shifted and selected plurality of scan lines.
Claim 35
Dependent Claim
38 words
A method in accordance with claim 34, further comprising: converting said filtered bar code image to a binary function using the average value of said combined shifted and selected plurality of scan lines as the binary threshold value.
Claim 36
Dependent Claim
158 words
In a bar code reader, an apparatus for determining the orientation of a bar code symbol comprising: means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for selecting a first scan line in a given area of said stored two dimensional image; means for selecting a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for calculating the cross-correlation function of said selected first scan line and said selected second scan line; and means for detecting the peak of said cross-correlation function of said first and second selected scan lines, wherein the position of said peak of said cross-correlation function of said selected first and second scan lines corresponds to the orientation of said bar code image.
Claim 37
Dependent Claim
46 words
An apparatus in accordance with claim 36, further comprising: means for shifting said selected second scan line so as to be aligned with said selected first scan line in accordance with said detected peak of said cross-correlation function of said selected first and second scan lines.
Claim 38
Dependent Claim
59 words
An apparatus in accordance with claim 36, for determining the orientation of a bar code symbol further comprising: means for selecting a plurality of scan lines in said given area of said stored two dimensional image; and means for calculating the respective cross-correlation function of selected pairs of selected scan lines from said plurality of said selected scan lines.
Claim 39
Dependent Claim
24 words
An apparatus in accordance with claim 38, further comprising: means for shifting said selected plurality of scan lines respectively so as to be aligned.
Claim 40
Dependent Claim
33 words
An apparatus in accordance with claim 39, further comprising: means for filtering said bar code image by taking the average of corresponding data points from said plurality of shifted and selected scan lines.
Claim 41
Dependent Claim
33 words
An apparatus in accordance with claim 39, further comprising: means for filtering said bar code image by taking the median of corresponding data points of said plurality of shifted and selected scan lines.
Claim 42
Dependent Claim
55 words
An apparatus in accordance with claim 39, further comprising: means for filtering said bar code image by taking the weighted average of corresponding data points of said plurality of shifted and selected scan lines, said average being weighted according to the magnitude of said cross-correlation function between said plurality of said respective selected scan lines.
Claim 43
Dependent Claim
32 words
An apparatus in accordance with claim 38 or 39, further comprising: means for filtering said bar code image by combining corresponding data points of said shifted and selected plurality of scan lines.
Claim 44
Dependent Claim
40 words
An apparatus in accordance with claim 43, further comprising: means for converting said filtered bar code image to a binary function using the average value of said combined shifted and selected plurality of scan lines as the binary threshold value.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.