Magnetorheological finishing and subaperture stitching interferometry of large and lightweight optics

Aric B. Shorey; William Kordonski; Marc Tricard

doi:10.1117/12.550997

24 September 2004 Magnetorheological finishing and subaperture stitching interferometry of large and lightweight optics

Aric B. Shorey, William Kordonski, Marc Tricard

Proceedings Volume 5494, Optical Fabrication, Metrology, and Material Advancements for Telescopes; (2004) https://doi.org/10.1117/12.550997
Event: SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom

Abstract

Significant challenges are faced in the manufacturing of the complex optics for the next generation of astronomical telescopes. Process improvements are required to establish cost effective techniques to finish the optics to the tight specification required in a timely manner. An added complication is realized when the optics are lightweight. The non-uniform support of the face-sheet in this case requires special efforts to avoid a print-through of the cell structure due to fabrication processes, gravity and/or cryogenic effects. Magnetorheological finishing (MRF) is a deterministic, sub-aperture polishing process that has been a revolutionary success in the fabrication of optics in the size range of 10-1000 mm. This production proven process is capable of polishing flats, spheres, aspheres and cylinders to a surface figure accuracy of better than 30 nm peak-to-valley (better than 5 nm rms), and microroughness better than 1 nm rms on a variety of glasses, glass ceramics and single crystal materials. Unique characteristics of MRF such as a high, stable removal rate, conformal nature of the sub-aperture tool and shear mode of material removal give it advantages in the finishing of large and lightweight optics. These qualities provide for a cost-effective process with a high rate of convergence that requires few iterations. Such a technology is ideally complemented by a system for the stitching of interferometric sub-aperture data. Stitching inherently enables the testing of larger apertures with higher resolution and, thanks to the built-in calibration, even to higher accuracy in many situations. While this approach enables the non-null testing of parts with greater aspheric departure and can lead to a significantly reduced non-common air path in the testing of long-radius concave parts, it is especially effective for convex optics. That is, stitching is particularly well suited to the testing of secondary mirrors and, alongside the testing of the off-axis primary segments.

Citation Download Citation

Aric B. Shorey, William Kordonski, and Marc Tricard "Magnetorheological finishing and subaperture stitching interferometry of large and lightweight optics", Proc. SPIE 5494, Optical Fabrication, Metrology, and Material Advancements for Telescopes, (24 September 2004); https://doi.org/10.1117/12.550997

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available