Line Finder Configuring Line Finder Properties - Advanced Conformity Tolerance Conformity Tolerance corresponds to the maximum distance in calibrated units by which a matched edge can deviate from either side of its expected position on the line. Default Conformity Tolerance is a read-only value that the tool computes by analyzing the cal- ibration, the edge detection parameters, and the search parameters. This can be a fixed value, or, if disabled, the Default. To manually set Conformity Tolerance you must check the Enable checkbox. l If you set a value lower than the Minimum Conformity Tolerance value, the Con- formity Tolerance value will be automatically reset to the minimum valid value.
l If you set a value higher than the Maximum Conformity Tolerance value, the Con- formity Tolerance value will be automatically reset to the maximum valid value. Contrast Threshold Contrast Threshold sets the minimum contrast needed for an edge to be detected in the input image. The threshold value expresses the step in light values required to detect edges. This threshold is expressed in terms of a step in grey-level values. The property can be set to Low, Normal, or High Sensitivity, or a fixed value. l This value can be set manually only when Contrast Threshold Mode is set to Fixed Value. l Higher values reduce sensitivity to contrast.
This reduces noise and the amount of low-contrast edges. l Lower values increase sensitivity and add a greater amount of edge at the expense of adding more noise. This may generate false detections and/or slow down the search process. Contrast Threshold Mode Contrast Threshold Mode defines how contrast threshold is set. Contrast threshold is the level of sensitivity that is applied to the detection of edges in the input image. The contrast threshold can be either Adaptive, or Fixed. Adaptive thresholds set a sensitivity level based on image content. This provides flexibility to variations in image lighting conditions and variations in contrast during the Search process.
l Adaptive Low Sensitivity uses a low sensitivity, adaptive threshold for detecting edges. Adaptive Low Sensitivity detects strongly-defined edges and eliminates noise, at the risk of losing significant edge segments. l Adaptive Normal Sensitivity sets a default sensitivity threshold for detecting edges. ACEUser's Guide, 3.6.x, 18316-000 Rev A Page 553