Non-Contact Whole-Part Inspection

Abstract

Optical scanners can collect millions of points of reasonable individual accuracy, and the advantages over touch probing are obvious enough – speed, coverage, ease of operation, price. So why has non-contact inspection not displaced the CMM? The paper's answer is that automatic extraction of actual dimensional and GD&T values from non-contact data is not yet a repeatable and reproducible procedure, and it works through the reasons: individual point accuracy still below a touch probe's, though the gap is closing; glossy and transparent surfaces that cause their own errors, though there are materials no touch probe can measure either; and the fundamentally different approaches the two kinds of data require.