Edge measurement video tool with robust edge discrimination margin

摘要

A reliable method for discriminating between a plurality of edges in a region of interest of an edge feature video tool in a machine vision system comprises determining a scan direction and an intensity gradient threshold value, and defining associated gradient prominences. The gradient threshold value may be required to fall within a maximum range that is based on certain characteristics of an intensity gradient profile derived from an image of the region of interest. Gradient prominences are defined by limits at sequential intersections between the intensity gradient profile and the edge gradient threshold. A single prominence is allowed to include gradient extrema corresponding to a plurality of respective edges. A gradient prominence-counting parameter is automatically determined that is indicative of the location of the selected edge in relation to the defined gradient prominences. The gradient prominence-counting parameter may correspond to the scan direction.

主权项

1. A method for improving the reliability of edge detection when discriminating between a plurality of edges in a region of interest of an edge feature video tool included in a machine vision inspection system, the method comprising:
providing an edge feature video tool comprising: a region of interest (ROI), edge detection operations governed by a plurality of edge detection parameters including an edge gradient threshold, a profile scan direction and a gradient prominence-counting parameter, and a video tool GUI comprising a region of interest indicator and an edge selection element; placing a workpiece in a field of view of the machine vision inspection system; operating the edge feature video tool to define a ROI including a plurality of edge features in an acquired image of the workpiece; operating the edge feature video tool to select an edge feature within the ROI to be the selected edge that is detected by the edge detection operations of the edge feature video tool; operating the edge feature video tool to determine the profile scan direction and the edge gradient threshold; and operating the edge feature video tool to automatically determine the gradient prominence-counting parameter corresponding to the profile scan direction and edge gradient threshold, wherein:
operating the edge feature video tool to determine the edge gradient threshold comprises operating the edge feature video tool to set the edge gradient threshold within a maximum range having a gradient profile extremum value of the selected edge as one limit and an opposing limit that is not farther from the selected edge extremum value than a limiting one of the two gradient profile neighbor extremum values of the two neighbor extrema that are adjacent to the selected edge extremum along an intensity gradient profile across the selected edge in the region of interest and that have a polarity opposite to the extremum of the selected edge, andoperating the edge feature video tool to automatically determine the gradient prominence-counting parameter corresponding to the determined profile scan direction and edge gradient threshold comprises performing automatic operations of the edge feature video tool configured such that the gradient prominence-counting parameter satisfies conditions comprising:(a) gradient prominences are defined by limits along the intensity gradient profile at sequential intersections between the intensity gradient profile and the determined edge gradient threshold, for at least the intersections that are encountered before the selected edge along the determined profile scan direction;(b) a single gradient prominence is allowed to include a plurality of gradient extrema corresponding to a plurality of respective edges along the intensity gradient profile between the limits defined by the condition (a); and(c) the gradient prominence-counting parameter is indicative of the location of the selected edge in relation to the defined gradient prominences.