13 May 2013 Highly accurate surface maps from profilometer measurements
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Abstract
Many aspheres and free-form optical surfaces are measured using a single line trace profilometer which is limiting because accurate 3D corrections are not possible with the single trace. We show a method to produce an accurate fully 2.5D surface height map when measuring a surface with a profilometer using only 6 traces and without expensive hardware. The 6 traces are taken at varying angular positions of the lens, rotating the part between each trace. The output height map contains low form error only, the first 36 Zernikes. The accuracy of the height map is ±10% of the actual Zernike values and within ±3% of the actual peak to valley number. The calculated Zernike values are affected by errors in the angular positioning, by the centering of the lens, and to a small effect, choices made in the processing algorithm. We have found that the angular positioning of the part should be better than 1, which is achievable with typical hardware. The centering of the lens is essential to achieving accurate measurements. The part must be centered to within 0.5% of the diameter to achieve accurate results. This value is achievable with care, with an indicator, but the part must be edged to a clean diameter.
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Kate M. Medicus, Kate M. Medicus, Jessica DeGroote Nelson, Jessica DeGroote Nelson, Mike P. Mandina, Mike P. Mandina, } "Highly accurate surface maps from profilometer measurements", Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 87881A (13 May 2013); doi: 10.1117/12.2020302; https://doi.org/10.1117/12.2020302
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