Fabrication of lightweight mirrors from low expansion glasses can be achieved using several techniques. Simple machining can reduce the weight of a typical solid mirror blank by up to 50 percent. Even more weight reduction can be realized through a sandwich type assembly of a lightweighted central core and two faceplates. The central core can be fabricated by cutting out cells form a solid blank using traditional fixed abrasive diamond grinding or abrasive waterjetting technology, or by fusion bonding thin struts into a honeycomb structure. The resultant lightweight core can then be bonded to mirror faceplates using either a fusion or frit bonding process. Each mirror fabrication approach offers its own advantages and disadvantages in term so weigh reduction, design flexibility, manufacturing time, and cost. These factor will be discussed, along with Corning's current size capability for each techniques.
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