Method and apparatus for determining the fine angular orientation of bar code symbols in two-dimensional CCD images
First Claim
1. A method for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising the steps of:
- (A) selecting a window from said two-dimensional image for processing;
(B) determining an edge magnitude and an edge direction for a plurality of pixels in said selected window;
(C) selecting a pixel from said plurality of pixels;
(D) if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold, then associating said edge magnitude and said edge direction of said selected pixel with at least one of a plurality of directional ranges;
(E) repeating steps (C)-(D) for each pixel in said plurality of pixels;
(F) selecting one directional range from said plurality of directional ranges;
(G) determining a density value associated with said selected directional range in accordance with the number of pixels associated with said selected directional range;
(H) repeating steps (F)-(G) for each of said plurality of directional ranges;
(I) selecting at least one candidate directional range in accordance with said associated density values; and
(J) determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range.
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Abstract
A system for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image. A window is selected from the two-dimensional image for processing. Edge magnitude information and edge direction information are determined for a plurality of pixels in the selected window. For each pixel in the plurality of pixels, the edge magnitude and the edge direction of each pixel is associated with at least one of a plurality of directional ranges if the edge magnitude associated with the pixel exceeds a threshold. For each directional range in the plurality of directional ranges, a density value associated with each directional range is determined in accordance with the number of pixels associated with the directional range, an angular mean value is determined in accordance with the edge directions associated with the directional range, and a noise value is determined in accordance with the edge directions associated with the directional range. At least one candidate directional range is selected in accordance with the associated density values. The fine angular orientation of a bar code symbol is determined in accordance with the edge directions associated with the candidate directional range.
139 Citations
34 Claims
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1. A method for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising the steps of:
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(A) selecting a window from said two-dimensional image for processing; (B) determining an edge magnitude and an edge direction for a plurality of pixels in said selected window; (C) selecting a pixel from said plurality of pixels; (D) if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold, then associating said edge magnitude and said edge direction of said selected pixel with at least one of a plurality of directional ranges; (E) repeating steps (C)-(D) for each pixel in said plurality of pixels; (F) selecting one directional range from said plurality of directional ranges; (G) determining a density value associated with said selected directional range in accordance with the number of pixels associated with said selected directional range; (H) repeating steps (F)-(G) for each of said plurality of directional ranges; (I) selecting at least one candidate directional range in accordance with said associated density values; and (J) determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising the steps of:
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(A) selecting a window from said two-dimensional image for processing; (B) determining an edge magnitude and an edge direction for a plurality of pixels in said selected window; (C) selecting a pixel from said plurality of pixels; (D) if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold, then associating said edge magnitude and said edge direction of said selected pixel with at least one of a plurality of directional ranges; (E) repeating steps (C)-(D) for each pixel in said plurality of pixels; (F) selecting one directional range from said plurality of directional ranges; (G) determining a deviation value associated with said selected directional range in accordance with said edge directions associated with said selected directional range; (H) repeating steps (F)-(G) for each of said plurality of directional ranges; (I) selecting at least one candidate directional range in accordance with said associated deviation values; and (J) determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range. - View Dependent Claims (10, 11, 12, 13)
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14. A method for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising the steps of:
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(A) selecting a window from said two-dimensional image for processing; (B) determining an edge magnitude and an edge direction for a plurality of pixels in said selected window; (C) selecting a pixel from said plurality of pixels; (D) if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold, then associating said edge magnitude and said edge direction of said selected pixel with at least one of a plurality of directional ranges; (E) repeating steps (C)-(D) for each pixel in said plurality of pixels; (F) selecting one directional range from said plurality of directional ranges; (G) determining an angular mean value associated with said selected directional range in accordance with said edge directions associated with said selected directional range; (H) repeating steps (F)-(G) for each of said plurality of directional ranges; (I) selecting at least one candidate directional range in accordance with said associated angular mean values; and (J) determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range. - View Dependent Claims (15, 16, 17)
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18. An apparatus for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising:
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(A) a window selector for selecting a window from said two-dimensional image for processing; (B) means for determining an edge magnitude and an edge direction for each of a plurality of pixels in said selected window; (C) a classifier for associating said edge magnitude and said edge direction of a selected pixel with at least one of a plurality of directional ranges if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold; (D) means for applying said classifier to each of said plurality of pixels; (E) a calculator for determining a density value associated with a selected directional range in accordance with the number of pixels associated with said selected directional range; (F) means for applying said calculator to each of said plurality of directional ranges; (G) a candidate directional range selector for selecting at least one candidate directional range in accordance with said associated density values; and (H) means for determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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26. An apparatus for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising:
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(A) a window selector for selecting a window from said two-dimensional image for processing; (B) means for determining an edge magnitude and an edge direction for each of a plurality of pixels in said selected window; (C) a classifier for associating said edge magnitude and said edge direction of a selected pixel with at least one of a plurality of directional ranges if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold; (D) means for applying said classifier to each of said plurality of pixels; (E) a calculator for determining a deviation value associated with a selected directional range in accordance with said edge directions associated with said selected directional range; (F) means for applying said calculator to each of said plurality of directional ranges; (H) a candidate directional range selector for selecting at least one candidate directional range in accordance with said associated deviation values; and (I) means for determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range. - View Dependent Claims (27, 28, 29, 30)
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31. An apparatus for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image comprising:
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(A) a window selector for selecting a window from said two-dimensional image for processing; (B) means for determining an edge magnitude and an edge direction for each of a plurality of pixels in said selected window; (C) a classifier for associating said edge magnitude and said edge direction of a selected pixel with at least one of a plurality of directional ranges if said edge magnitude associated with said selected pixel exceeds a first predetermined threshold; (D) means for applying said classifier to each of said plurality of pixels; (E) a calculator for determining an angular mean value associated with a selected directional range in accordance with said edge directions associated with said selected directional range; (F) means for applying said calculator to each of said plurality of directional ranges; (G) a candidate directional range selector for selecting at least one candidate directional range in accordance with said associated angular mean values; and (H) means for determining said fine angular orientation in accordance with said edge directions associated with said at least one candidate directional range. - View Dependent Claims (32, 33, 34)
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Specification