Fabrication and metrology of high-precision freeform surfaces

Supranowitz, Chris; Dumas, Paul; Nitzsche, Tobias; Nelson, Jessica DeGroote; Light, Brandon; Medicus, Kate; Smith, Norman F.

doi:10.1117/12.2030144

Cited by 14 publications

(3 citation statements)

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“…MRF [12] and ion-milling [13] provide successful state-ofthe-art asphere surface finishing technologies. The MRF process routinely polishes surfaces to so-called 'super polish' leaving microroughness of the surface (parameter Ra) well below 1 nm [10].…”

Section: Mrf and Ion-milling Aspheric Surface Finishingmentioning

confidence: 99%

Ultra-smooth finishing of aspheric surfaces using CAST technology

Kong¹,

Young²

2014

Advanced Optical Technologies

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Abstract:Growing applications for astronomical groundbased adaptive systems and air-born telescope systems demand complex optical surface designs combined with ultra-smooth finishing. The use of more sophisticated and accurate optics, especially aspheric ones, allows for shorter optical trains with smaller sizes and a reduced number of components. This in turn reduces fabrication and alignment time and costs. These aspheric components include the following: steep surfaces with large aspheric departures; more complex surface feature designs like stand-alone off-axis-parabola (OAP) and free form optics that combine surface complexity with a requirement for ultra-high smoothness, as well as special optic materials such as lightweight silicon carbide (SiC) for air-born systems. Various fabrication technologies for finishing ultra-smooth aspheric surfaces are progressing to meet these growing and demanding challenges, especially Magnetorheological Finishing (MRF) and ion-milling. These methods have demonstrated some good success as well as a certain level of limitations. Amongst them, computer-controlled asphere surface-finishing technology (CAST), developed by Precision Asphere Inc. (PAI), plays an important role in a cost effective manufacturing environment and has successfully delivered numerous products for the applications mentioned above. One of the most recent successes is the Gemini Planet Imager (GPI), the world's most powerful planet-hunting instrument, with critical aspheric components (seven OAPs and free form optics) made using CAST technology. GPI showed off its first images in a press release on January 7, 2014 . This paper reviews features of today's technologies in handling the ultra-smooth aspheric optics, especially the capabilities of CAST on these challenging products. As examples, three groups of aspheres deployed in astronomical optics systems, both polished and finished using CAST, will be discussed in detail.

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Section: Mrf and Ion-milling Aspheric Surface Finishingmentioning

confidence: 99%

Ultra-smooth finishing of aspheric surfaces using CAST technology

Kong¹,

Young²

2014

Advanced Optical Technologies

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“…In order to achieve higher precision freeform surface, sub-aperture deterministic polishing processes are necessary. [6,7] Deterministic polishing processes are dependent on the metrology method used to measure the initial figure error. The area of freeform metrology is currently under investigation by a number of different research groups.…”

Section: Current Freeform Optical Manufacturing and Testing Processesmentioning

confidence: 99%

“…The area of freeform metrology is currently under investigation by a number of different research groups. [7][8][9][10] Achievable surface form error of freeform surfaces is a function of the complexity of the shape and the uncertainty of the measurement method. A typical scanning probe coordinate measuring machine is limited to approximately ±1 µm PV form error.…”

Section: Current Freeform Optical Manufacturing and Testing Processesmentioning

confidence: 99%

Fabricating and Testing Freeform Optics: Current Capabilities, Lessons Learned and Future Opportunities

Nelson

Medicus

Brophy

2014

Classical Optics 2014

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Freeform optical shapes or optical surfaces that are designed with non-symmetric features are gaining popularity with lens designers and optical system integrators. A common question about freeform optics is, "If I design it, can you really make it?" This paper will overview a freeform optical fabrication process that includes generation, high speed VIBE polishing, subaperture figure correction, surface smoothing and testing of freeform surfaces. This paper will briefly highlight the progress made to each of the processes as well as the challenges associated with each of them.

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