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US 6,587,582 B1Granted
Semiconductor device image inspection with contrast enhancement
AssigneeCognex Corporation
InventorsSanjay J. Nichani, Joseph Scola
Life of this patent
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Abstract
Machine vision methods for inspection of semiconductor die lead frames include the steps of generating a first image of the lead frame, generating a second image of the lead frame and any defect thereon, and subtracting the second image from the first image. The methods are characterized in that the second image is generated such that subtraction of it from the first image emphasizes the defect with respect to the lead frame.
Claims15
A machine vision method for inspecting a substantially flat surface, the method comprising:
- generating with a digital camera a first image of the substantially flat surface and a defect thereon;
- generating with the digital camera a second image of the substantially flat surface and the defect thereon, such that the defect in the second image is of a different contrast polarity with respect to the substantially flat surface than the defect in the first image with respect to the substantially flat surface;
- comparing, for the purpose of contrast enhancement of reflectivity features of the defect with respect to the substantially flat surface, each pixel of the second image to each corresponding pixel of the first image;
- generating a third image representing results of comparing each pixel;
- and
- isolating the defect using the third image.
3 more elements
A method according to 9, wherein the normalizing step includes the steps of
- determining distributions of intensity values of each of the first and second images;
- generating a mapping function for matching extrema of those distributions;
- and
- transforming the intensity values of at least one of the first and second images with that mapping function.
1 more element
Dependencies are inferred from the claim text.