Image analysis – Pattern recognition – Template matching
Reexamination Certificate
1999-01-25
2003-04-08
Mehta, Bhavesh M. (Department: 2625)
Image analysis
Pattern recognition
Template matching
C382S156000
Reexamination Certificate
active
06546137
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improving images and more particularly to object localization with an advanced search hierarchy.
2. Description of the Prior Art
The needs for accurate and efficient object localization prevail in many industrial applications, such as automated visual inspection and factory automation. The efficiency of the object localization system is directly related to the throughput of the product. In addition, the machine vision system should also be general enough to perform different kinds of tasks in a very short period of task switching time. This can significantly increase the applicability as well as the productivity of the system, which is very important for adapting to the fast changing needs of customers and markets.
The image reference approach is very popular in automatic visual inspection due to its general applicability to a variety of inspection tasks. This is further described by R. T. Chin in “Automatic Visual Inspection: 1981 to 1987”, Computer Vision, Graphics, and Image Processing, Vol. 41, No. 3, pp. 346-381, 1988. However, it requires very precise alignment of the inspection pattern in the image. To achieve very precise pattern alignment, traditional template matching is extremely time-consuming when the search space is large. Some methods have been proposed to resolve this alignment problem. These are described by T. S. Newman and A. K. Jain in “A Survey Of Automatic Visual Inspection”, Computer Vision and Image Understanding, Vol. 61, No. 2, pp. 231-262, 1995; by A. A. Rodriguez and J. R. Mandeville in “Image Registration For Automated Inspection Of Printed Circuit Patterns Using CAD Reference Data”, Machine Vision and Applications, Vol. 6, pp. 233-242, 1993; and by T. Hiroi, S. Maeda, H. Kubota, K. Watanabe and Y. Nakagawa in “Precise Visual Inspection For LSI Wafer Patterns Using Subpixel Image Alignment”, Proc. Second IEEE Workshop on Applications of Computer Vision, pp. 26-34, Florida, December 1994. Rodriguez and Mandeville proposed an image registration technique by fitting feature points in the zero-crossings extracted from the inspection image to the corresponding points extracted from the CAD model via an affine transformation. However, the correspondence between the two set of feature usually can not be reliably established. Hiroi et al. presented a sum-of-squared-differences (SSD) based method to determine the shift between the two images. Unfortunately, this method is restricted to recover small shifts.
SUBJECT OF THE INVENTION
The present invention provides a new FLASH (Fast Localization with Advanced Search Hierarchy) system for fast and accurate object localization in a large search space. This object localization system is very useful for applications in automated visual inspection and pick-and-place systems for automatic factory assembly. This system is based on the assumption that the surrounding regions of the pattern within the search range are always fixed. The FLASH system comprises a hierarchical nearest-neighbor search system and an optical-flow based energy minimization system. The hierarchical nearest-neighbor search system produces rough estimates of the transformation parameters for the optical-flow based energy minimization system which provides very accurate estimation results and associated confidence measures.
REFERENCES:
patent: 5048100 (1991-09-01), Kuperstein
patent: 5757287 (1998-05-01), Kitamura et al.
patent: 6026189 (2000-02-01), Greenspan
patent: 6175644 (2001-01-01), Scola et al.
Fang Ming
Lai Shang-Hong
Azarian Seyed
Mehta Bhavesh M.
Paschburg Donald B.
Siemens Corporate Research Inc.
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