An overview of optical fabrication of the JWST mirror segments at Tinsley

Cole, Glen; Garfield, Robert E.; Peters, T.; Wolff, W.; Johnson, Kris W.; Bernier, Robert; Kiikka, C.; Nassar, Taha; Wong, Howard A.; Kincade, J.; Hull, Tony; Gallagher, Ben; Chaney, David; Brown, Robert; McKay, Andrew; Cohen, Lester M.

doi:10.1117/12.672926

Cited by 13 publications

(13 citation statements)

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“…[ 133,134 ] The infrared scanning Shack–Hartmann test was employed for surface metrology during optical fabrication of James Webb Space Telescope (JWST) segment mirrors before transition to visible interferometry with CGH nulls. [ 135 ]…”

Section: Non‐interferometric Areal Measurementmentioning

confidence: 99%

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

Chen

Xue

Zhai

et al. 2020

Laser & Photonics Reviews

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Freeform optical surfaces are advantageous to optical designers, as they provide additional degrees of freedom for optimization. The loss of rotational symmetry, however, makes measurement of freeforms more challenging. Herein, advances in interferometric areal measurement of freeform optical surfaces, including null tests, non-null tests, near-null tests, and adaptive null tests, are reviewed. Some new developments, in the Hartmann test, deflectometry, and phase retrieval, as representatives of non-interferometric areal measurement, are then presented. Overall, the focus is on single-point-probe-based profilometry categorized into coordinate measurements and slope-or curvature-based measurements. Innovative measurement technology is trying to bridge the gap between high accuracy and high dynamic range as freeform optical surfaces are finding more applications in visible and shorter-wavelength optics.

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Section: Non‐interferometric Areal Measurementmentioning

confidence: 99%

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

Chen

Xue

Zhai

et al. 2020

Laser & Photonics Reviews

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“…Beryllium is challenging to use in fabricating optical elements for several reasons. First, the material can be toxic if small particles enter the airways, which requires extensive safety procedures when being machined [120]. Further, material removal rates are low, surface pitting is precarious, and the material is stress-sensitive even for typical process stresses.…”

Section: 2a Primary Mirror Surfacesmentioning

confidence: 99%

“…This metrology tool guided the fabrication from 25 to 12 μm loose abrasive grinding, which resulted in a 1 μm RMS surface[122]. After the surface reaches this level of roughness, a clear reflection is obtained by a minimal polishing-out run and other more traditional test methods may be used in conjunction with finer fabrication methods.The JWST primary mirror segments were measured during the generation stage using a coordinate measuring machine for initial qualification, providing a spatial resolution of 0.25 mm with an accuracy of 0.3 μm[120]. As the grinding progressed to the point of obtaining a 10 μm RMS roughness, an infrared scanning Shack Hartmann system (SSHS) was employed as a full aperture test.…”

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confidence: 99%

Optics technology for large-aperture space telescopes: from fabrication to final acceptance tests

et al. 2018

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This review paper addresses topics of fabrication, testing, alignment, and as-built performance of reflective space optics for the next generation of telescopes across the x-ray to far-infrared spectrum. The technology presented in the manuscript represents the most promising methods to enable a next level of astronomical observation capabilities for space-based telescopes as motivated by the science community. While the technology to produce the proposed telescopes does not exist in its final form, the optics industry is making steady and impressive progress toward these goals across all disciplines. We hope that through sharing these developments in context of the science objectives, further connections and improvements are enabled to push the envelope of the technology.

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“…The James Webb Space Telescope (JWST), the successor of the Hubble Space Telescope, is made up of a primary mirror containing 18 segments. Its entrance pupil diameter is 6.6m and its global radius of curvature (GROC) is 15.8m whereas the segment-to-segment radius difference is required to be ±0.1 mm [1] . In our previous research, we suggested the tolerance on radius mismatch was very stringent, and a method of independent radius of curvature (ROC) control was proposed for the individual segments [2] .…”

Section: Introductionmentioning

confidence: 99%

“…In order to reduce the wavefront error close to zero, because the local control method can only change the sag of the center area of each segment, we need to push the wavefront in the outer area to zero and use the coef of the local control to compensate the center area. Therefore, the equation (9) is used to replace the equation(6) in the fourth level compensation and the coef compensation is approximated by Equation (10):1 1…”

mentioning

confidence: 99%

Effect of radius mismatch on performance of segmented telescopic systems

et al. 2007

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There exist great interests in using segmented mirrors instead of monoliphic primary mirror to build large aperture telescopes. The use of segmented mirrors reduces the difficulties in fabrication, transportation and replication as well as decreases the impact of gravity. In the meanwhile, one of the grand challenges in this approach lies in matching the individual mirrors to yield the form of a continuous surface. The erroneous differences between the global radii of curvature (GROC) of the segmented mirrors have significant influence on image quality. In this paper, we present a model of segmented systems and an analysis technique which reveals the effect of these errors on the image quality. Our analytical results show that the GROC differences have great influence on image quality and the impact remains high despite of using active optics to compensate these errors. The local radii of curvature of individual mirror segment should be used to correct these errors. We propose a new approach to generate compensators that controls the local radius of curvature of each segment efficiently. Finally, through simulation results, we demonstrate that the new compensators can dramatically reduce the effect of radius mismatch.

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An overview of optical fabrication of the JWST mirror segments at Tinsley

Cited by 13 publications

References 0 publications

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

Optics technology for large-aperture space telescopes: from fabrication to final acceptance tests

Effect of radius mismatch on performance of segmented telescopic systems

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