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Rethinking Scratch-and-Dig Specifications

Presentation will begin: Wednesday, January 11, 2023 - 12:40 PM EST
Presented by: Dave Aikens, Savvy Optics

The scratch-and-dig specification, described in the MIL-PRF-13830B standard, has been the de facto method of controlling surface imperfections on optics for most components and systems since it was first introduced by McLeod and Sherwood in 1945. It uses a subjective visual comparison for specification grades based on a set of limit masters retained at Picatinny Arsenal. Today, it is the only remaining specification that is validated with a subjective visual examination.

Increasingly, Army-traceable comparison standards are expensive and hard to come by. With the advent of machine vision applied to surface imperfections, it is reasonable to consider remastering the scratch-and-dig standard to be based on brightness under specific conditions. Such a remastering could provide a more linear grading system with a wider range of specifications, for applications in which 10-5 is too loose or 80-50 is too tight.

Aikens discusses the details of such a specification and test method, how it could address the community's needs, and what remains to be developed to rethink scratch-and-dig specifications.


About the presenter
Dave AikensDave Aikens is president and founder of Savvy Optics Corp. He is the world’s foremost expert in surface imperfection specifications. Aikens has worked in the field of standardization since 1983, and he was the chair of the U.S. Technical Advisory Group to ISO/TC 172 Optics and Photonics. Aiken’s SPIE course, “Understanding Scratch and Dig,” has been the definitive guide to surface imperfection specifications on optics since 2005. His company pioneered applying machine vision technology to surface imperfection inspection with the introduction of the SavvyInspector in 2009. He holds bachelor’s and master’s degrees in optics from the University of Rochester, has secured more than a dozen patents, and has published more than 40 papers in the field. Aikens is an SPIE fellow and the 2021 recipient of the prestigious A.E. Conrady Award.




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