Circle Gauge Tool


Posted by Brad Quist on Fri, Sep 02, 2011 @ 04:08 PM

  The Circle Gauge Tool in PPT VISION's VPM software lets you find the center of a circle very accurately. Because it combines a large number of sub-pixel results, it averages out the errors associated with individual measurements.

In the image below, the circle Region of Interest (ROI) is searching for the transition of dark pixels to bright pixels from the outside of the circle to the inside. Once the edge points are determined, a best-fit line is drawn through those points. Then, based on other tolerances defined in the tool, the center point of the circle is calculated as a best-fit circle and drawn on the image.


The circle ROI can be adjusted over just a fraction of the circle and the tool will still calculate the best-fit center of the circle.

The image below shows only a part of the circle within the Field of View (FOV), with the circle ROI drawn on the image. The calculated center point X-Y coordinate is actually outside the FOV, but this is not a problem for the software. Even though this center point is not displayed on the image, it can still be used for measurements and tolerances can be placed on these measurements.

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