Round robin comparison study on the form measurement of optical freeform surfaces

Fortmeier, Ines; Schachtschneider, Reyko; Lédl, Vít; Matoušek, Ondřej; Siepmann, Jens; Harsch, Antonia; Beisswanger, Rolf; Bitou, Youichi; Kondo, Yasuhiko; Schulz, Michael; Elster, Clemens

doi:10.1186/s41476-019-0124-1

Cited by 21 publications

(22 citation statements)

References 13 publications

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“…To make the differences between the different measurement results more visible, the design topography is usually removed after the measurements have been aligned with the design. Additionally, the different measurement systems usually have large uncertainty contributions for the measurement of the spherical components of the surface such as the best-fit sphere (BFS) [23]. For some optical applications, the spherical contribution can be compensated if an optical system is mounted or adjusted in a certain way.…”

Section: Comparison Concept For Aspheres and Freeform Measurements An...mentioning

confidence: 99%

“…In the following, the concept of data comparison within the scope of a typical round robin comparison of measurements of aspheres and freeform surfaces is briefly described. For this purpose, we limit ourselves to procedures that have recently been used [18][19][20][21]23]. In most cases, the absolute form measurement data sets (design and deviation from the design) are analyzed in terms of Cartesian coordinates.…”

Section: Comparison Proceduresmentioning

confidence: 99%

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Comparison of form measurement results for optical aspheres and freeform surfaces

Fortmeier

Schulz

2022

Meas. Sci. Technol.

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Comparing form measurement data for aspheres and freeform surfaces is an important tool for ensuring the quality and functionality of the devices used to take such measurements and may also allow the underlying measurement methods to be evaluated. However, comparing the highly accurate form measurements of such complex surfaces is a demanding task. It is diﬃcult to analyze measurement results whose accuracies are in the range of several tens of nanometers root-mean-square, especially when comparing data with diﬀerent, and anisotropic distributions of the 3D measurement points on the surface under test. In this paper, we investigate eight diﬀerent 3D measurement point distributions that are typical of highly accurate measurement systems currently in use and demonstrate the eﬀects of these distributions on the comparison results by using virtually generated data and applying diﬀerent evaluation strategies. The results show that, for the examples investigated, the diﬀerent 3D measurement point distributions can yield diﬀerent levels of accuracy for the comparison. Furthermore, an improved evaluation procedure is proposed and recommendations on how to signiﬁcantly reduce the inﬂuence of the diﬀerent 3D measurement point distributions on the comparison result are given. A method of employing virtually generated test data is presented that may be generalized in order to further improve and validate future comparison methods.

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Section: Comparison Concept For Aspheres and Freeform Measurements An...mentioning

confidence: 99%

Section: Comparison Proceduresmentioning

confidence: 99%

Comparison of form measurement results for optical aspheres and freeform surfaces

Fortmeier

Schulz

2022

Meas. Sci. Technol.

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“…In the scientific field, telescopes and x-ray mirrors for synchrotron radiation facilities are especially famous 1 – 6 To meet the complex optical performance, optical elements with more complex shapes are required, and the demands for spherical, aspherical, and free-form surfaces are becoming more sophisticated 7 , 8 . Various measuring devices have been developed to meet the demands for these complex shapes.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6] To meet the complex optical performance, optical elements with more complex shapes are required, and the demands for spherical, aspherical, and free-form surfaces are becoming more sophisticated. 7,8 Various measuring devices have been developed to meet the demands for these complex shapes. Interferometers and coordinate measuring machines (CMMs) are commonly used.…”

Section: Introductionmentioning

confidence: 99%

Cylindrical surface shape measurement method and measurement comparison

Miyawaki

Endo

2022

Opt. Eng.

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Optical elements are used in various fields, in which it is required to measure spherical, aspherical, and free-form surface shapes. We use a nanoprofiler previously developed by our research group to measure a cylindrical surface shape. Unlike spherical or aspherical shapes, the cylindrical surface shape of free-form surface is rotationally asymmetrical and thus difficult to determine the measured position. Therefore, we processed fiducial marks on the measured sample and specified the measurement position by fiducial marks. Then we performed comparative measurements with a Fizeau interferometer using a computer generated hologram (CGH) as a reference plane. The nanoprofiler and interferometer measured to accuracies of 43.7 nm peak-tovalley (PV) and 60.9 nm PV, respectively; the difference between the two was 17.2 nm PV. Furthermore, a spherical shape and an aspherical shape were similarly measured by both devices. The spherical shape had a difference of 8.4 nm PV and that of the aspherical shape was 9.7 nm PV; thus the difference between the measurements of the cylindrical surface shape was larger. Considering that the guaranteed accuracy of CGH for measuring a cylindrical surface shape is ∼30 nm PV, we concluded that this is a reasonable result and fiducial marks are effective to determine the position.

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“…They are used for repeated measurements of specimens with the same design. Another example is the tilted wave interferometer, 10 , 11 which uses spatially distributed light sources (instead of a positioning system) to determine a surface topography from several interferograms. The surface form is reconstructed by recreating the observed interference patterns with a numerical simulation of the system, thus solving an inverse problem.…”

Section: Introductionmentioning

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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Round robin comparison study on the form measurement of optical freeform surfaces

Cited by 21 publications

References 13 publications

Comparison of form measurement results for optical aspheres and freeform surfaces

Comparison of form measurement results for optical aspheres and freeform surfaces

Cylindrical surface shape measurement method and measurement comparison

Traceable stitching interferometry for form measurement of moderately curved freeform surfaces

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