Validation of upgrades to the NIST M48 vision measurement system

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Abstract

One-dimensional and two-dimensional vision artifacts are calibrated at NIST using the Dimensional Metrology Group's M48 vision measurement system. The vision system replaces the tactile probing system on the primary M48 CMM (coordinate measurement machine) with a camera system integrated into the CMM controller, combining the ultra-accurate 2D positioning of the M48 CMM with non-contact edge detection. Typical expanded measurement uncertainties (k = 2) are between 0.15-0.50 μm, dependent upon artifact quality. However, degradation of the hardware over time has made the system less reliable, causing long lead times for calibrations. Currently, resolution and image quality limit the artifacts which can be measured on the machine, and there is customer-based need to improve the scope of artifacts which can be measured. Line width limitations are currently 5μ-10 μm and customer needs are pushing toward lines widths ⩽5 μm and need greater flexibility in artifact illumination. This work details the first steps taken toward improving the reliability and capabilities of this system. Using the CTE of common glass vision artifacts, 8.0 × 10−6/ °C, the expanded measurement uncertainty (k = 2) is proposed as 0.092 μm + 1.2 × 10−7 l for one-dimensional measurements and 0.24 μm + 1.1 × 10−7 l for two-dimensional measurements. Measurements of long term NIST check standards and standard reference materials are used to validate these uncertainties.

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Metrology and Dimensional metrology

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