Caliper Configuring Caliper Properties - Advanced The Advanced Properties section of the Caliper tool interface provides access to advanced Cal- iper parameters and properties. Edge Detection Parameters Edge Detection settings configure the parameters that the Caliper will use to find potential edges in the region of interest. The display represents the Caliper region of interest and provides information to assist in configuring Edge Detection parameters. Edge Filter Half-Width The filtering process attenuates peaks in the magnitude curve that are caused by noise. Edge Filter Half Width should be set to a value approximately equivalent to the width of the edge, in pixels.
An incorrect value can cause edges to be incorrectly detected. Tool Sampling Parameters Sampling refers to the procedure used by the tool for gathering values within the portion of the input image that is bounded by the tool region of interest. Two sampling parameters, the Sampling Step and Bilinear Interpolation, can be used to create the desired balance between speed and accuracy. Bilinear Interpolation Bilinear Interpolation uses pixel averaging to improve the quality of the image. It is applied before the image is analyzed. To ensure subpixel accuracy in inspection applications, Bilinear Interpolation should always be set to True (enabled).
Non-interpolated sampling (Bilinear Interpolation disabled) should only be used in applications where the speed requirements are more critical than accuracy. Custom Sampling Step (1 - 100) The Sampling Step is the step used by the tool to sample the area of the input image that is bounded by the tool region of interest. The sampling step represents the height and the width of a sampled pixel. For applications where a more specific tradeoff between speed and accuracy must be estab- lished, the sampling step can be modified by enabling the Custom Sampling Step and setting the desired value. ACEUser's Guide, 3.6.x, 18316-000 Rev A Page 454