ITT has patented and continues to develop processes to fabricate low-cost borosilicate mirrors that can be used for both
ground and space-based optical telescopes. Borosilicate glass is a commodity and is the material of choice for today's
flat-panel televisions and monitors. Supply and demand has kept its cost low compared to mirror substrate materials
typically found in telescopes. The current technology development is on the path to having the ability to deliver imaging
quality optics of up to 1m (scalable to 2m) in diameter in three weeks. For those applications that can accommodate the
material properties of borosilicate glasses, this technology has the potential to revolutionize ground and space-based
astronomy. ITT Corporation has demonstrated finishing a planar, 0.6m borosilicate, optic to <100 nm-rms. This paper
will provide an historical overview of the development in this area with an emphasis on recent technology developments
to fabricate a 0.6m parabolic mirror under NASA Earth Science Technology Office (ESTO) grant #NNX09AD61G.
The 25 m aperture Cornell Caltech Atacama Telescope (CCAT) will be the first segmented telescope of its size and precision. A new technology was required to be able to economically manufacture the segments for the primary mirror. This technology had to be a low cost, low risk, volume manufacturing process in addition to meeting all of the optical and mechanical requirements. The segments had to be lightweight (10-15 kg/m<sup>2</sup>), have high specific stiffness and be thermally stable. The segments had to have sufficient robustness for practical transport and use and be compatible with high-reflectivity coatings. ITT has designed a replicated, lightweight glass mirror solution to these manufacturing problems. This technology can be used to fabricate segments for CCAT. It can be used to fabricate segments for visible wavelength segmented telescopes or any other application requiring lightweight optics in large quantities. This technology enables the fabrication of large, lightweight mirror segments in a few weeks to a couple of months, depending on the figure requirements. This paper discusses the design of these mirrors and presents demonstrated results to date, including a 0.5 m diameter, 8 kg/m<sup>2</sup> borosilicate mirror blank and 0.2 m diameter replicated borosilicate mirrors.
Finish polishing of optics with magnetic media has evolved extensively over the past decade. Of the approaches conceived during this time, the most recently developed process is called magnetorheological finishing (MRF). In MRF, a magnetic field stiffens a fluid suspension in contact with a workpiece. The workpiece is mounted on the rotating spindle of a computer numerically controlled machine. Driven by an algorithm for machine control that contains information about the MRF process, the machine deterministically polishes out the workpiece by removing microns of subsurface damage, smoothing the surface to a microroughness of 10 angstroms rms, and correcting surface figure errors to less than 0.1 micrometers p-v. Spheres and aspheres can be processed with the same machine set-up using the appropriate machine program. This paper describes MRF and gives examples which illustrate the capabilities of a pre-prototype machine located at the Center for Optics Manufacturing.
Conference Committee Involvement (3)
Active and Passive Signatures VI
22 April 2015 | Baltimore, Maryland, United States
Active and Passive Signatures V
7 May 2014 | Baltimore, Maryland, United States
Optical Materials and Structures Technologies III
26 August 2007 | San Diego, California, United States