Status of highly accurate flatness metrology at PTB for optics up to 1.5 meters in diameter

Ehret, Gerd; Spichtinger, Jan; Schulz, Michael

doi:10.1117/12.2602680

Cited by 3 publications

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“…PTB is currently developing a new traceable form measurement system for large optics up to 1.5 m in diameter 27 . Methods and experiences gained while working on this publication will be used in the new system.…”

Section: Discussionmentioning

confidence: 99%

Traceable stitching interferometry for form measurement of moderately curved freeform surfaces

et al. 2022

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We present an interferometric form measurement system that is capable of measuring the form of optical surfaces from flats to moderately curved freeforms. A Fizeau interferometer is scanned over the specimen measuring its topography and the distance to the surface in subaperture measurements. The angle between the interferometer and the specimen is adjusted for each position and additionally relevant stage angle errors are measured with two tiltmeters. An optical surface with a spherical form (50 mm diameter, 10 m radius of curvature) is measured, and an uncertainty budget yields an uncertainty of 69 nm ðk ¼ 2Þ for its topography. The determined radius of curvature agrees well with the nominal specifications and a measurement with a coordinate measurement machine. Furthermore, a form measurement of a car's side window is presented. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Discussionmentioning

confidence: 99%

Traceable stitching interferometry for form measurement of moderately curved freeform surfaces

et al. 2022

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“…Low-uncertainty flatness tests are usually accomplished with interferometry. Remarkably, some varieties of DM are able to improve on its performance and reach down to sub-nm uncertainty levels (Illemann et al, 2002;Pedreira et al, 2019;Siewert et al, 2019;Ehret et al, 2021). Slope maps are recorded here with a scanning autocollimator, and the surface reconstruction is based on several 1D scans.…”

Section: Scanning Deflectometric Techniquesmentioning

confidence: 99%

Deflectometry for specular surfaces: an overview

et al. 2023

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Deflectometry as a technique to assess reflective surfaces has now existed for some 40 years. Its different aspects and variations have been studied in multiple theses and research articles; reviews are available for certain subtopics. Still a field of active development with many unsolved problems, deflectometry now encompasses a large variety of application domains, hardware setup types, and processing workflows for different purposes, and spans a range from qualitative defect inspection of large vehicles to precision measurements of microscopic optics. Over these years, many exciting developments have accumulated in the underlying theory, in the systems design, and in the implementation specifics. This diversity of topics is difficult to grasp for experts and non-experts alike and may present an obstacle to a wider acceptance of deflectometry as a useful tool for research and industrial applications. This paper presents an attempt to summarize the status of deflectometry and to map relations between its notable branches. Its aim is to provide a communication basis for experienced practitioners and also to offer a convenient entry point for those interested in learning about the method. The list of references introduces some prominent trends and established research groups in order to facilitate further self-directed exploration.

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“…Low-uncertainty flatness tests are usually accomplished with interferometry. Remarkably, some varieties of DM are able to improve on its performance and reach sub-nm uncertainty levels [53][54][55]. Slope maps are recorded here with a scanning autocollimator, and the surface reconstruction is based on several 1D scans.…”

Section: Scanning Deflectometric Techniquesmentioning

confidence: 99%

Deflectometry for specular surfaces: an overview

Burke¹,

Pak²,

Höfer³

et al. 2022

Preprint

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Deflectometry as a technical approach to assessing reflective surfaces has now existed for almost 40 years. Different aspects and variations of the method have been studied in multiple theses and research articles, and reviews are also becoming available for certain subtopics. Still a field of active development with many unsolved problems, deflectometry now encompasses a large variety of application domains, hardware setup types, and processing workflows designed for different purposes, and spans a range from qualitative defect inspection of large vehicles to precision measurements of microscopic optics. Over these years, many exciting developments have accumulated in the underlying theory, in the systems design, and in the implementation specifics. This diversity of topics is difficult to grasp for experts and nonexperts alike and may present an obstacle to a wider acceptance of deflectometry as a useful tool in other research fields and in the industry.This paper presents an attempt to summarize the status of deflectometry, and to map relations between its notable "spin-off" branches. The intention of the paper is to provide a common communication basis for practitioners and at the same time to offer a convenient entry point for those interested in learning and using the method. The list of references is extensive but definitely not exhaustive, introducing some prominent trends and established research groups in order to facilitate further selfdirected exploration by the reader.

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Status of highly accurate flatness metrology at PTB for optics up to 1.5 meters in diameter

Cited by 3 publications

References 0 publications

Traceable stitching interferometry for form measurement of moderately curved freeform surfaces

Traceable stitching interferometry for form measurement of moderately curved freeform surfaces

Deflectometry for specular surfaces: an overview

Deflectometry for specular surfaces: an overview

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