US4975972A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for surface inspection
Assignee: Nokia Bell Labs
•
Filing: 1988-10-18
•
Granted: 1990-12-04
•
Expires: 2008-10-18
Abstract
Abstract Detection of a defect (18) on the surface (15) of an article (10), such as a semiconductor chip, is accomplished by illuminating the chip in a bright field and then capturing the image thereof with a television camera (30) coupled to a machine vision processor (32). To detect the defect 18, the vision processor first adaptively thresholds the captured image to effectively eliminate areas in the image brighter than those associated with the defect (18) which are usually dark. Thereafter, the vision processor (32) erodes and then dilates the dark areas within the image remaining after binarization to isolate those dark areas associated with the defect. The existence of a defect can then be established by the existence of a now-isolated dark area.
Inventors
- 👤 Chinmoy B. Bose
- 👤 Rajarshi Ray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 12:51
CPC Classifications
G; G06; G06T; G06T7/00; G06T7/0002; G06T7/0004; G01; G01N; G01N21/00; G01N21/84; G01N21/88; G06T5/00; G06T5/20; G06T5/30; G06T7/10; G06T7/136; G01N21/8851; G01N2021/8887; G06T2207/00; G06T2207/30; G06T2207/30108; G06T2207/30148
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
211 words
A method for inspecting a surface of an article, having at least one feature thereon, to detect defects, if any, which are either smaller or larger than the linewidth of the feature, the method comprising the steps of: illuminating the surface of the article with light which is directed to strike the surface substantially normal to the plane thereof so that upon illumination of the surface, each defect appears dark; capturing the image of the surface of the article with an image-acquisition device whose optical axis is substantially normal to the axis of the surface; binarizing the captured image to cause those areas within the image having an intensity below a threshold value to appear dark, and those areas having an intensity above the threshold value to appear bright; processing the binarized image to produce a first image in which those defects, if any, which are larger than the linewidth of the feature, are isolated; processing the binarized image to produce a second image in which those defects, if any, which are smaller than the linewidth of the feature, are isolated; logically ANDing the first and second images to yield a third image; and establishing the presence of a defect by the existence in the third image of a dark area.
Claim 2
Independent Claim
211 words
A method for inspecting a surface of an article, having at least one feature thereon, to detect defects, if any, which are either smaller or larger than the linewidth of the feature, the method comprising the steps of: illuminating the surface of the article with light which is directed to strike the surface substantially normal to the plane thereof so that upon illumination of the surface, each defect appears dark; capturing the image of the surface of the article with an image-acquisition device whose optical axis is substantially normal to the axis of the surface; binarizing the captured image to cause those areas within the image having an intensity below a threshold value to appear dark, and those areas having an intensity above the threshold value to appear bright; processing the binarized image to produce a first image in which those defects, if any, which are larger than the linewidth of the feature, are isolated; processing the binarized image to produce a second image in which those defects, if any, which are smaller than the linewidth of the feature, are isolated; logically ANDing the first and second images to yield a third image; and establishing the presence of a defect by the existence in the third image of a dark area.
Claim 3
Independent Claim
174 words
A method for processing an image containing both regularly occurring features and at least one defect which may be smaller or larger than the linewidth of the feature, to isolate the feature from the defect, the method comprising the steps of: binarizing the image to cause those areas within the image having an intensity below a threshold value to appear dark, and those areas having an intensity above the threshold value to appear bright; processing the binarized image by eroding and dilating each dark area therein to yield a first image containing only the defects, if any, larger than the feature; processing the binarized image by eroding and dilating each dark area to yield a second image in which each defect, if any, which is smaller than the linewidth of the feature, is effectively eliminated, while the feature, and the defects, if any, larger than the feature remain; and subtracting the second image from the first image and then inverting the resultant image, the inverted resultant image now containing only the regularly occurring feature.
Claim 4
Independent Claim
174 words
A method for processing an image containing both regularly occurring features and at least one defect which may be smaller or larger than the linewidth of the feature, to isolate the feature from the defect, the method comprising the steps of: binarizing the image to cause those areas within the image having an intensity below a threshold value to appear dark, and those areas having an intensity above the threshold value to appear bright; processing the binarized image by eroding and dilating each dark area therein to yield a first image containing only the defects, if any, larger than the feature; processing the binarized image by eroding and dilating each dark area to yield a second image in which each defect, if any, which is smaller than the linewidth of the feature, is effectively eliminated, while the feature, and the defects, if any, larger than the feature remain; and subtracting the second image from the first image and then inverting the resultant image, the inverted resultant image now containing only the regularly occurring feature.
Claim 5
Dependent Claim
14 words
The apparatus according to claim 1 wherein the image-acquisition means comprises a television camera.
Claim 6
Dependent Claim
39 words
The apparatus according to claim 2 wherein the means for binarizing the image, the means for processing the image, and the means for establishing the size of the defects comprise a machine vision processor coupled to the television camera.
References Cited (Backward Citations)
US4601057A
Cited
US4700225A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-12-03 | 1994-06-04 | 1994-12-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-03 | 1998-06-04 | 1998-12-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-03 | 2002-06-04 | 2002-12-04 | $7700.00 | Window Closed / Lapsed |