Image processing method for appearance inspection
First Claim
1. An image processing method for appearance inspection, said method comprising the steps of:
- a) taking a picture of an object to be inspected to provide an object image for comparison with a reference image;
b) extracting an outline of said object image to give an object outline;
c) extracting an outline of said reference image to give a reference outline;
d) processing data of said object outline and said reference outline in accordance with a least-square error function for deriving error parameters including a position, a rotation angle, and a scale of the object outline relative to said reference outline, and applying the resulting error parameters to transform said reference outline;
e) repeating the step of (d) until said resulting error parameters satisfy a predetermined criterion indicative of a linear transformation factor of said object image;
f) applying said error parameters to transform said reference image into a final reference image;
g) comparing said object image with the final reference image to select pixels of said object image each having a grey-scale intensity far from a corresponding pixel of said final reference image by a predetermined value or more, and h) analyzing thus selected pixels to judge whether the object image is different from the reference image, and providing a defect signal if the object image is different from the reference image.
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Accused Products
Abstract
A method for appearance inspection utilizes a reference image and an object image. Before determining a final reference image for direct comparison with the object image, the outlines of the reference and object images are extracted and processed in accordance with an error function indicative of linear or quadric deformation of the object image in order to derive error parameters including a position, a rotation angle, and a scale of the object image relative to reference image. The resulting error parameters are applied to transform the reference outline. The step of updating the error parameters and transforming the reference outline is repeated until the updated error parameters satisfy a predetermined criterion with respect to a linear or quadric transformation factor of the object image. Thereafter, the last updated parameters are applied to transform the reference image into the final reference image for direct comparison with the object image.
56 Citations
7 Claims
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1. An image processing method for appearance inspection, said method comprising the steps of:
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a) taking a picture of an object to be inspected to provide an object image for comparison with a reference image;
b) extracting an outline of said object image to give an object outline;
c) extracting an outline of said reference image to give a reference outline;
d) processing data of said object outline and said reference outline in accordance with a least-square error function for deriving error parameters including a position, a rotation angle, and a scale of the object outline relative to said reference outline, and applying the resulting error parameters to transform said reference outline;
e) repeating the step of (d) until said resulting error parameters satisfy a predetermined criterion indicative of a linear transformation factor of said object image;
f) applying said error parameters to transform said reference image into a final reference image;
g) comparing said object image with the final reference image to select pixels of said object image each having a grey-scale intensity far from a corresponding pixel of said final reference image by a predetermined value or more, and h) analyzing thus selected pixels to judge whether the object image is different from the reference image, and providing a defect signal if the object image is different from the reference image. - View Dependent Claims (3, 4, 5, 6, 7)
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2. An image processing method for appearance inspection, said method comprising the steps of:
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a) taking a picture of an object to be inspected to provide an object image for comparison with a reference image;
b) extracting an outline of said object image to give an object outline;
c) extracting an outline of said reference image to give a reference outline;
d) processing data of said object outline and said reference outline in accordance with a least-square error function for deriving error parameters including a position, a rotation angle, and a scale of the object outline relative to said reference outline, and applying the resulting error parameters to transform said reference outline;
e) repeating the step of (d) until said resulting error parameters satisfies a predetermined criterion indicative of a quadric transformation factor of said object image;
f) applying said error parameters to transform said reference image into a final reference image;
g) comparing said object image with the final reference image to select pixels of said object image each having a grey-scale intensity far from a corresponding pixel of said final reference image by a predetermined value or more, and h) analyzing thus selected pixels to judge whether the object image is different from the reference image, and providing a defect signal if the object image is different from the reference image.
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Specification