Detection of surface defects employing subsampled images

Abstract

A method for determining a location of a border in a color image, the image including at least two color populations, between a first color region associated with a first one of the two color populations and a second color region associated with a second one of the two color populations, both the first color region and the second color region being in the color image, the method includes identifying an approximate border location between the first color region and the second color region, determining a plurality of candidate border locations between the first color region and the second color region, each of the plurality of candidate border locations being determined by applying a corresponding border location method chosen from among a plurality of border location methods, choosing one method from among the plurality of border location methods as a preferred method, and determining a location of a border between the first color region and the second color region by designating one of the plurality of candidate border locations associated with the preferred method as the border. Also, an automated optical inspection device suitable for inspection of patterned articles.

Description

FIELD OF THE INVENTION [0001] The present invention relates to apparatus and methods for analyzing images, especially but not exclusively color images, and more specifically to apparatus and methods of image analysis which are useful in inspection of a patterned object. BACKGROUND OF THE INVENTION [0002] Apparatus and methods for analyzing images, and in particular for image analysis which is useful in inspection of a patterned object, are well known in the art. [0003] The following references describe image processing methods which may be useful in understanding the present invention: [0004] C. Gonzalez and P. Wintz, Digital Image Processing, Addison Wesley, Reading, M A, 1987; and [0005] John C. Russ, The Image Processing Handbook, CRC Press, 1994. [0006] The following references describe edge detection methods which may be useful in understanding the present invention: [0007] D. Marr and E. Hildreth, Theory of Edge Detection, Proceedings of the Royal Society of London; and [0008]...

AI Technical Summary

Benefits of technology

[0024] All prior art object inspection systems suffer from certain limitations which make them useful for inspecting only certain types of objects, even if the objects being inspected are limited to the fields of printed circuit boards, integrated circuits, and similar electronic components. The present invention seeks to provide improved apparatus and methods of analyzing images, particularly color images, particularly for the purpose of improving the functionality of object inspection systems, increasing the diversity of objects that can be inspected by the system, and generally reducing the limitations thereof.

[0025] It is believed that improved color processing may be particularly effective in analyzing images of multi-colored objects, particularly in cases where adjacent colored areas in the multi-colored objects have colors which are difficult to distinguish from each other in a monochrome image. For example, in the case of inspection of a ball grid array substrate or a laminated printed circuit board, it may be desirable to distinguish between areas which are, on the surface thereof, gold and areas which are, on the surface thereof, copper, and to distinguish between metallic areas which are covered by partially transparent masks and areas which are uncovered. Similarly, areas which are, on the surface thereof, silver may be distinguished from other areas. It is believed that distinguishing between such areas may be accomplished more effectively using the methods and apparatus of the present invention than in the prior art.

Problems solved by technology

All prior art object inspection systems suffer from certain limitations which make them useful for inspecting only certain types of objects, even if the objects being inspected are limited to the fields of printed circuit boards, integrated circuits, and similar electronic components.

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