Patent · US Expired

Automatic detection of alignment or registration marks

US6842538B2 · kind B2 · utility

26Cited by

11References

3Claims

0Family size

Inventors

Shih-Jong J. Lee · Bellevue, US
Seho Oh · Mukilteo, US
Larry A. Nelson · Hillsboro, US

Key dates

Filing date	Mar 23, 2001
Grant date	Jan 11, 2005
Priority date	—
Expiry date	Jan 15, 2023

Classification

Technology area (CPC G)Physics
CPC primaryG06V10/44
WIPO fieldComputer technology
WIPO sectorElectrical engineering

Abstract

Mark detection and position determination are improved by use of directional elongated filters, symmetry, gray scale image processing, structural constraints, and learning. Directional elongated filters are used to pre-process images of registration marks to create masks and enhanced images. Working sequentially, portions of the mark are detected and classified. The input gray scale image of the mark is processed using its structural constraints in conjunction with a mask for the detected mark. A cost function estimation determines mark position and orientation with sub-pixel accuracy. Learning is used to improve specific application performance.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.