Fabrication of high precision metallic freeform mirrors with magnetorheological finishing (MRF)

Matthias Beier; Sebastian Scheiding; Andreas Gebhardt; Roman Loose; Stefan Risse; Ramona Eberhardt; Andreas Tünnermann

doi:10.1117/12.2035986

15 October 2013 Fabrication of high precision metallic freeform mirrors with magnetorheological finishing (MRF)

Matthias Beier, Sebastian Scheiding, Andreas Gebhardt, Roman Loose, Stefan Risse, Ramona Eberhardt, Andreas Tünnermann

Proceedings Volume 8884, Optifab 2013; 88840S (2013) https://doi.org/10.1117/12.2035986
Event: SPIE Optifab, 2013, Rochester, New York, United States

Abstract

The fabrication of complex shaped metal mirrors for optical imaging is a classical application area of diamond machining techniques. Aspherical and freeform shaped optical components up to several 100 mm in diameter can be manufactured with high precision in an acceptable amount of time. However, applications are naturally limited to the infrared spectral region due to scatter losses for shorter wavelengths as a result of the remaining periodic diamond turning structure. Achieving diffraction limited performance in the visible spectrum demands for the application of additional polishing steps. Magnetorheological Finishing (MRF) is a powerful tool to improve figure and finish of complex shaped optics at the same time in a single processing step. The application of MRF as a figuring tool for precise metal mirrors is a nontrivial task since the technology was primarily developed for figuring and finishing a variety of other optical materials, such as glasses or glass ceramics. In the presented work, MRF is used as a figuring tool for diamond turned aluminum lightweight mirrors with electroless nickel plating. It is applied as a direct follow-up process after diamond machining of the mirrors. A high precision measurement setup, composed of an interferometer and an advanced Computer Generated Hologram with additional alignment features, allows for precise metrology of the freeform shaped optics in short measuring cycles. Shape deviations less than 150 nm PV / 20 nm rms are achieved reliably for freeform mirrors with apertures of more than 300 mm. Characterization of removable and induced spatial frequencies is carried out by investigating the Power Spectral Density.

Citation Download Citation

Matthias Beier, Sebastian Scheiding, Andreas Gebhardt, Roman Loose, Stefan Risse, Ramona Eberhardt, and Andreas Tünnermann "Fabrication of high precision metallic freeform mirrors with magnetorheological finishing (MRF)", Proc. SPIE 8884, Optifab 2013, 88840S (15 October 2013); https://doi.org/10.1117/12.2035986

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