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ZERODUR® glass ceramic is a material well established in stability-critical industrial markets. While ZERODUR®’s chemical formulation has been unchanged for over 50 years, its thermal attributes can be tailored for specific temperature ranges. Especially, its near-zero thermal expansion, its homogeneous properties and its extensive characterization are favorable for applications requiring heightened dimensional stability performance. SCHOTT invested extensively into both comprehensive material characteristic studies, and into a newly dedicated highly capable machining and metrology facility. We will describe the capabilities of SCHOTT’s newly-build ZERODUR® competence center focusing on CNC machining and precise characterization of monolithic lightweight mirrors through 4-meter sizes. Beside the production of various light-weighted designs, any optical form on a mirror’s specular surface can be generated. This is done by precision grinding while, at the same time, minimizing the sub-surface damage. Subsequently, the optical finishers can expect a better starting point and the utility to the telescope designer becomes evident. Latest results on optimizing the front figure tolerance for different mirror substrate diameters are presented. We will emphasize the capabilities of the precisely controlled 5-m coordinate measurement equipment. These refined manufacturing methods support the design of better, more affordable, higher performance future optical assemblies and enable design-to-cost approaches for cost-critical projects. |
