US6753965B2
Expired / Lapsed
US
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Defect detection system for quality assurance using automated visual inspection
Assignee: University of Hong Kong
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Filing: 2001-10-25
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Granted: 2004-06-22
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Expires: 2021-10-25
Abstract
Abstract A defect detection method and system for the automated visual inspection of web materials is provided. The invention utilize real Gabor function (RGF) filters with a non-linear function for estimating the local energy. An example method for quality assurance using automated visual inspection in accordance with the invention includes the steps of: automated design of a bank of RGF filters; using these RGF filters to sample the features of image under inspection; using a non-linear function to compute local energy estimate in the filtered images; combining all the filtered images using image fusion; and finally thresholding the resultant image to segment the defects in the inspection image. Possible embodiments of the described invention include detection of only a class of defects using a single tuned real Gabor filter or a bank of real Gabor functions.
Inventors
- 👤 Ajay Kumar
- 👤 Kwok-Hung Grantham Pang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:17
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/84; G01N21/88; G01N21/89; G01N21/892; G01N21/898; G01N21/8983
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
160 words
A quality assurance method for inspecting a surface of an object for defects against a texture background in uniform and textured web products using automated visual inspection comprising the steps of: imaging a web material to obtain an image; detecting, automatically, at least one frequency component associated with the background texture of a reference image; applying a pre-designed set of real Gabor function based filters associated with the at least one frequency component and a mask parameter to evaluate features of the image under inspection and generate a plurality of derived images corresponding to the pre-designed set of real Gabor function based filters; estimating energy in a local region by computing a local energy function from at least one of the plurality of derived images to generate a blob-detecting image; combining at least two blob-detecting images with the aid of an image fusion rule to obtain a resultant image; and thresholding the resultant image to further segment any possible defect(s).
Claim 2
Dependent Claim
160 words
A quality assurance method for inspecting a surface of an object for defects against a texture background in uniform and textured web products using automated visual inspection comprising the steps of: imaging a web material to obtain an image; detecting, automatically, at least one frequency component associated with the background texture of a reference image; applying a pre-designed set of real Gabor function based filters associated with the at least one frequency component and a mask parameter to evaluate features of the image under inspection and generate a plurality of derived images corresponding to the pre-designed set of real Gabor function based filters; estimating energy in a local region by computing a local energy function from at least one of the plurality of derived images to generate a blob-detecting image; combining at least two blob-detecting images with the aid of an image fusion rule to obtain a resultant image; and thresholding the resultant image to further segment any possible defect(s).
Claim 3
Dependent Claim
17 words
The method according to claim 1 wherein the combining step employs image using Bernoulli's rule of combination.
Claim 4
Dependent Claim
19 words
The method according to claim 1 wherein the combining step further employs image fusion using vector addition of pixels.
Claim 5
Dependent Claim
21 words
The method according to claim 1 wherein the step of imaging includes generating a set of pixels corrected for illumination irregularities.
Claim 6
Dependent Claim
20 words
The method of claim 1 wherein the local energy function is a rectified sigmoid in the step of estimating energy.
Claim 7
Dependent Claim
18 words
The method of claim 5 wherein the rectified sigmoid is tuned by adjusting β in the range 0.2-0.3.
Claim 8
Dependent Claim
19 words
The method according to claim 1 , wherein image correction compensates for illumination irregularities by comparison with a reference.
Claim 9
Dependent Claim
34 words
The method according to claim 1 , further including the step of computing the threshold by estimating at least one maximum value for a pixel in an integrated image generated from the reference image.
Claim 10
Dependent Claim
16 words
The method according to claim 1 wherein the surface under inspection is that of a textile.
Claim 11
Dependent Claim
15 words
The method according to claim 1 wherein the surface under inspection is that of wood.
Claim 12
Dependent Claim
16 words
The method according to claim 1 wherein the surface under inspection is that of a metal.
Claim 13
Dependent Claim
16 words
The method according to claim 1 wherein the surface under inspection is that of a paper.
Claim 14
Dependent Claim
12 words
The method according to claim 1 wherein the mask parameter is 5×5.
Claim 15
Dependent Claim
13 words
The method according to claim 1 , wherein the mask parameter is 9×9.
Claim 16
Dependent Claim
13 words
The method according to claim 1 , wherein the mask parameter is 7×7.
Claim 17
Independent Claim
74 words
A method for quality assurance in uniform and textured web products with known yarn density using automated visual inspection comprising the steps of: imaging a web material to obtain an image of a surface; applying a pre-designed Gabor filter to the image to generate a filtered image; applying a nonlinear function to a pixel in the filtered image to generate a resultant image; and thresholding the resultant image to segment at least one defect.
Claim 18
Independent Claim
74 words
A method for quality assurance in uniform and textured web products with known yarn density using automated visual inspection comprising the steps of: imaging a web material to obtain an image of a surface; applying a pre-designed Gabor filter to the image to generate a filtered image; applying a nonlinear function to a pixel in the filtered image to generate a resultant image; and thresholding the resultant image to segment at least one defect.
Claim 19
Dependent Claim
15 words
The method according to claim 16 , wherein the nonlinear function is a median filter.
Claim 20
Dependent Claim
15 words
The method according to claim 16 , wherein the nonlinear function is a squaring function.
Claim 21
Dependent Claim
29 words
The method according to claim 16 , wherein computing the threshold includes estimating a maximum value for a pixel in an integrated image generated from a defect-free web material.
Claim 22
Dependent Claim
14 words
The method according to claim 16 , wherein the surface is a textile surface.
Claim 23
Dependent Claim
14 words
The method according to claim 16 , wherein the surface is a wood surface.
Claim 24
Dependent Claim
14 words
The method according to claim 16 , wherein the surface is a metal surface.
Claim 25
Dependent Claim
14 words
The method according to claim 16 , wherein the surface is a paper surface.
Claim 26
Independent Claim
99 words
A method for quality assurance in uniform and textured web products with known yarn density using automated visual inspection comprising the steps of: imaging a defect-free web material by generating a set of pixels corrected for illumination irregularities to obtain an image; selecting at least one frequency component associated with the background texture of the image; designing at least one real Gabor function based filter using the at least one frequency component associated with the background texture of the image; and computing, automatically, a threshold associated with the at least one real Gabor function based filter using the image.
Claim 27
Independent Claim
99 words
A method for quality assurance in uniform and textured web products with known yarn density using automated visual inspection comprising the steps of: imaging a defect-free web material by generating a set of pixels corrected for illumination irregularities to obtain an image; selecting at least one frequency component associated with the background texture of the image; designing at least one real Gabor function based filter using the at least one frequency component associated with the background texture of the image; and computing, automatically, a threshold associated with the at least one real Gabor function based filter using the image.
Claim 28
Dependent Claim
18 words
The method according to claim 24 wherein image correction compensates for illumination irregularities by comparison with a reference.
Claim 29
Dependent Claim
44 words
The method according to claim 24 wherein the step of selecting includes automatically determining the at least one frequency component associated with the background texture of the image from a set of pixels in the warp direction whereby reducing the need for manual tuning.
Claim 30
Dependent Claim
12 words
The method according to claim 24 wherein the mask parameter is 5×5.
Claim 31
Dependent Claim
12 words
The method according to claim 24 wherein the mask parameter is 9×9.
Claim 32
Dependent Claim
12 words
The method according to claim 24 wherein the mask parameter is 7×7.
Claim 33
Dependent Claim
16 words
The method according to claim 24 wherein the surface under inspection is that of a textile.
Claim 34
Independent Claim
142 words
A method for quality assurance in the uniform and textured web products using automated visual inspection comprising the steps of: imaging a defect-free web material by generating a set of pixels corrected for illumination irregularities to obtain an image; detecting, automatically, a first frequency component associated with the background texture of the image from a set of pixels in the warp direction and a second frequency component associated with the background texture of the image from a set of pixels in the weft direction; selecting a highest frequency component following comparison of at least the first and the second frequency components; designing at least one real Gabor function based filter using the selected frequency component associated with the background texture of the image; and computing, automatically, a threshold associated with the at least one real Gabor function based filter using the image.
Claim 35
Independent Claim
142 words
A method for quality assurance in the uniform and textured web products using automated visual inspection comprising the steps of: imaging a defect-free web material by generating a set of pixels corrected for illumination irregularities to obtain an image; detecting, automatically, a first frequency component associated with the background texture of the image from a set of pixels in the warp direction and a second frequency component associated with the background texture of the image from a set of pixels in the weft direction; selecting a highest frequency component following comparison of at least the first and the second frequency components; designing at least one real Gabor function based filter using the selected frequency component associated with the background texture of the image; and computing, automatically, a threshold associated with the at least one real Gabor function based filter using the image.
Claim 36
Dependent Claim
19 words
The method according to claim 31 , wherein image correction compensates for illumination irregularities by comparison with a reference.
Claim 37
Dependent Claim
17 words
The method according to claim 31 , wherein the surface under inspection is that of a textile.
Claim 38
Dependent Claim
32 words
The method according to claim 31 , wherein the step of computing the threshold includes estimating a maximum value for a pixel in an integrated image generated from the defect-free web material.
Claim 39
Dependent Claim
27 words
The method of claim 34 wherein the integrated image is generated from a plurality of real Gabor functions that include the at least one real Gabor function.
Claim 40
Independent Claim
181 words
A system for automatically detecting defects against a textured background in a surface of a material, the system comprising: image acquisition means; at least one processor configured to execute the steps for detecting, automatically, at least one frequency component associated with the background texture of a reference image, applying a pre-designed set of real Gabor function based filters associated with the at least one frequency component and a mask parameter to evaluate features of the image under inspection and generate a plurality of derived images corresponding to the pre-designed set of real Gabor function based filters, estimating energy in a local region by computing a local energy function from at least one of the plurality of derived images to generate a blob-detecting image, combining at least two blob-detecting images with the aid of an image fusion rule to obtain a resultant image, and thresholding the resultant image to further segment any possible defect(s); and a memory for storing at least one mean and standard deviation value for a blob detecting image, and at least one threshold based on a defect-free image.
Claim 41
Independent Claim
181 words
A system for automatically detecting defects against a textured background in a surface of a material, the system comprising: image acquisition means; at least one processor configured to execute the steps for detecting, automatically, at least one frequency component associated with the background texture of a reference image, applying a pre-designed set of real Gabor function based filters associated with the at least one frequency component and a mask parameter to evaluate features of the image under inspection and generate a plurality of derived images corresponding to the pre-designed set of real Gabor function based filters, estimating energy in a local region by computing a local energy function from at least one of the plurality of derived images to generate a blob-detecting image, combining at least two blob-detecting images with the aid of an image fusion rule to obtain a resultant image, and thresholding the resultant image to further segment any possible defect(s); and a memory for storing at least one mean and standard deviation value for a blob detecting image, and at least one threshold based on a defect-free image.
References Cited (Backward Citations)
US4630304A
Cited
US5301129A
Cited
US5737072A
Cited
US5740048A
Cited
US5774177A
Cited
US5825501A
Cited
EP0974831A2
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2007-06-22 | 2007-12-22 | 2008-06-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2011-06-22 | 2011-12-22 | 2012-06-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2015-06-22 | 2015-12-22 | 2016-06-22 | $7700.00 | Window Closed / Lapsed |