Calibration and optimization of computer-controlled optical surfacing for large optics

Kim, Dae Wook; Martin, Hubert M.; Burge, James H.

doi:10.1117/12.893878

Cited by 11 publications

(8 citation statements)

References 21 publications

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“…As the size of the footprint is always less than the work-piece in CCP [4,14], the ripple error is generated as a fragmentary structure on the surface [15][16][17]. It is serious in some applications such as intense laser systems and high-resolution image formation systems for scattering [17,18].…”

Section: Introductionmentioning

confidence: 98%

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Strategy of restraining ripple error on surface for optical fabrication

et al. 2014

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The influence from the ripple error to the high imaging quality is effectively reduced by restraining the ripple height. A method based on the process parameters and the surface error distribution is designed to suppress the ripple height in this paper. The generating mechanism of the ripple error is analyzed by polishing theory with uniform removal character. The relation between the processing parameters (removal functions, pitch of path, and dwell time) and the ripple error is discussed through simulations. With these, the strategy for diminishing the error is presented. A final process is designed and demonstrated on K9 work-pieces using the optimizing strategy with magnetorheological jet polishing. The form error on the surface is decreased from 0.216λ PV (λ=632.8 nm) and 0.039λ RMS to 0.03λ PV and 0.004λ RMS. And the ripple error is restrained well at the same time, because the ripple height is less than 6 nm on the final surface. Results indicate that these strategies are suitable for high-precision optical manufacturing.

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Section: Introductionmentioning

confidence: 98%

“…They found that the major trend is that the surface error increases with the pitch of the path. Moreover, the influence of the ripple error on the processing time is investigated [15,22]. However, the high-precision surfacing is affected by many parameters that should be discussed synthetically.…”

Section: Introductionmentioning

confidence: 99%

Strategy of restraining ripple error on surface for optical fabrication

et al. 2014

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“…We developed software to optimize dwell vs position based on a map of surface errors. [18] We are building a new orbital polisher to replace the first-generation system that we installed while polishing Segment 1. It will drive passive laps ranging in size from 60 cm diameter-for correction of large-scale figure errors-to 5 cm in the radial dimension for correction of small-scale radial structure near the edge.…”

Section: Improved Orbital Polishingmentioning

confidence: 99%

Status of mirror segment production for the Giant Magellan Telescope

et al. 2016

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The Richard F. Caris Mirror Lab at the University of Arizona is responsible for production of the eight 8.4 m segments for the primary mirror of the Giant Magellan Telescope, including one spare off-axis segment. We report on the successful casting of Segment 4, the center segment. Prior to generating the optical surface of Segment 2, we carried out a major upgrade of our 8.4 m Large Optical Generator. The upgrade includes new hardware and software to improve accuracy, safety, reliability and ease of use. We are currently carrying out an upgrade of our 8.4 m polishing machine that includes improved orbital polishing capabilities. We added and modified several components of the optical tests during the manufacture of Segment 1, and we have continued to improve the systems in preparation for Segments 2-8. We completed two projects that were prior commitments before GMT Segment 2: casting and polishing the combined primary and tertiary mirrors for the LSST, and casting and generating a 6.5 m mirror for the Tokyo Atacama Observatory.

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“…Figure 3 shows three bending modes of the combined M1-M3. [9], [10] containing a layer of non-Newtonian fluid between a stiff metal disk and (on the polishing side) a thin rubber diaphragm covered with synthetic polishing pads. We used RC laps with diameters of 35 cm, 25 cm and 12 cm.…”

Section: Simulating the Active-optics Correctionmentioning

confidence: 99%

“…This method is very deterministic and effective at controlling mid-scale structure. [10] For M1, most of the final figuring was done using the 80 cm stressed lap with pitch, and the 25 cm RC lap. For M3, when the mirror was nearly finished we noticed that a layer of nylon in the stressed lap was failing at multiple bond joints.…”

Section: Simulating the Active-optics Correctionmentioning

confidence: 99%

Manufacture and final tests of the LSST monolithic primary/tertiary mirror

et al. 2016

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The LSST M1/M3 combines an 8.4 m primary mirror and a 5.1 m tertiary mirror on one glass substrate. The combined mirror was completed at the Richard F. Caris Mirror Lab at the University of Arizona in October 2014. Interferometric measurements show that both mirrors have surface accuracy better than 20 nm rms over their clear apertures, in nearsimultaneous tests, and that both mirrors meet their stringent structure function specifications. Acceptance tests showed that the radii of curvature, conic constants, and alignment of the 2 optical axes are within the specified tolerances. The mirror figures are obtained by combining the lab measurements with a model of the telescope's active optics system that uses the 156 support actuators to bend the glass substrate. This correction affects both mirror surfaces simultaneously. We showed that both mirrors have excellent figures and meet their specifications with a single bending of the substrate and correction forces that are well within the allowed magnitude. The interferometers do not resolve some small surface features with high slope errors. We used a new instrument based on deflectometry to measure many of these features with sub-millimeter spatial resolution, and nanometer accuracy for small features, over 12.5 cm apertures. Mirror Lab and LSST staff created synthetic models of both mirrors by combining the interferometric maps and the small highresolution maps, and used these to show the impact of the small features on images is acceptably small.

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Calibration and optimization of computer-controlled optical surfacing for large optics

Cited by 11 publications

References 21 publications

Strategy of restraining ripple error on surface for optical fabrication

Strategy of restraining ripple error on surface for optical fabrication

Status of mirror segment production for the Giant Magellan Telescope

Manufacture and final tests of the LSST monolithic primary/tertiary mirror

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