Updating the peak-to-valley (PV) irregularity specification for the modern world

Paul E. Murphy

doi:10.1117/12.2690828

29 November 2023 Updating the peak-to-valley (PV) irregularity specification for the modern world

Paul E. Murphy

Proceedings Volume 12778, Optifab 2023; 127780Z (2023) https://doi.org/10.1117/12.2690828
Event: SPIE Optifab, 2023, Rochester, New York, United States

Abstract

Communicating fabrication tolerances is a vital part of the optical manufacturing process. The most common surface form tolerance is peak-to-valley (PV) irregularity, and its specification and evaluation has largely remained unchanged for decades. Fabrication, testing, and computation capabilities, however, have evolved considerably over that time, exposing PV’s extreme sensitivity to outlier data points. When everyone was using the same measurement and analysis technique (visual inspection of test plate interferograms), this sensitivity was of secondary concern to ease of computation. Today, however, numerous measurement techniques are viable for evaluating surface form, computation power is cheap, and different measurements of the same surface can easily result in wildly different PV results. This creates confusion as to whether a surface conforms to tolerance or not. To address this issue, we propose standardized methods for evaluating a PV tolerance value that are resistant to outliers. We first provide an example of the problem on an actual surface measurement and demonstrate how trimmed PV estimators can mitigate it. We review two such estimators, robust peak valley (PVr) and clipped peak-to-valley (PV%). We then review the conceptual trade-offs involved with choosing an appropriate estimator and demonstrate estimator behavior on a variety of simulated surface profiles. Finally, we explore the challenges in adopting a more reliable PV metric and outline the plans for updating the ISO 10110-5 surface form standard to achieve this.

Conference Presentation

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Paul E. Murphy "Updating the peak-to-valley (PV) irregularity specification for the modern world", Proc. SPIE 12778, Optifab 2023, 127780Z (29 November 2023); https://doi.org/10.1117/12.2690828

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