Performance evaluation of a vibration desensitized scanning white light interferometer

Abstract

Surface metrology instruments normally require thermal, seismic and acoustic isolation. Shop-floor metrology solutions offer reduced cost and process time. If they operate on the same principles as laboratory devices, an inherent sensitivity to vibration remains. This paper describes a methodology for evaluating 'environmental tolerance' and applying it to characterize a recently introduced 'environmentally tolerant' scanning white light interferometer (SWLI). Previously published measurements of replicated nickel reference standards on the new instrument and on a stylus profilometer showed good correlation. Surface topography repeatabilities (per ISO 25178-604:2013) were insignificantly different when evaluated on the SWLI instrument in a metrology laboratory and in a manufacturing area. Measurements of reference standards under forced vibration of the entire instrument show maximum ripple error and data dropout in regions of structural resonance. Measurements were performed with large forced horizontal and vertical sample oscillation beneath the objective, exhibiting maximum ripple error near odd integer multiples of half the instrument detector frequency. Error due to data dropout was also investigated.

Robustness of Surface Roughness against Low Number of Picture Elements and Its Benefit for Scaling Analysis

“…Typically, the as-measured morphological images have fixed pixels, e.g., 512 × 512 in AFM measurements. Thus, the pixels of a segmented sub-images is lower than that of an image attained by an actual measurement at the same L, which may partly decrease the credibility of Rq results, as many researchers [38][39][40] reported in their relevant studies. Therefore, questions may arise about the similarity and difference between the RSE and TR methods.…”

Performance Evaluation of a Robot-Mounted Interferometer for an Industrial Environment

“…This could be done by measuring the vibrations with a sensor (e.g., accelerometer) and re-calculating (correcting) the Z values assigned to each image taken by the interferometer during its scan motion before surface data is reconstructed. Alternatively, the effectiveness of vibration-removal strategies originally developed for laboratory-based instruments can be tested [33,[38][39][40].…”

“…This compact nature also enables robotic deployment, as demonstrated in [22][23][24][25] through the combined use of a laser line scanner (low resolution, for large area coverage) and a scanning interferometer (Heliotis H6, high resolution, for local high resolution measurements) mounted on a robot arm. While the performance evaluation of such high resolution instrumentation in a laboratory environment has been widely addressed [26][27][28][29][30][31][32][33], the application of these sensors in non-ideal, shop-floor applications, as well as in robotic deployment, clearly demonstrates the need for re-evaluating and extending performance standards [34].…”

“…Based on the evaluation, a summary and strategy for optimal robotic deployment of the interferometer is provided. such high resolution instrumentation in a laboratory environment has been widely addressed [26][27][28][29][30][31][32][33], the application of these sensors in non-ideal, shop-floor applications, as well as in robotic deployment, clearly demonstrates the need for re-evaluating and extending performance standards [34]. By evaluating the performance of the Heliotis H6, this paper attempts to answer three key questions: (i) how does the lightweight H6 performance compare to a lab-based coherent scanning instrument (Bruker NPFLEX); (ii) how applicable are existing performance test standards, developed for laboratory-based scanning interferometers, to a robot-mounted scenario, and what can be learned from these to improve robotic deployment; (iii) how can these standards be extended to include novel aspects arising from in-factory, robot-mounted deployment.…”

Electropolishing effect on roughness metrics of ground stainless steel: a length scale study

“…This ripple pattern is an artificial artifact due to the limited environmental noise that exists during measurement. A detailed classification and quantitative study of the noise sources can be found in [33,34].…”