Corning Inc. of Corning, N.Y., has agreed to acquire Optovac Inc. of North Brookfield, Mass., from EM Industries Inc. The terms of the agreement were not disclosed. Optovac produces calcium fluoride optics for ultraviolet lithography of semiconductors. The move followed Corning's announcement that it has agreed to purchase the Munich, Germany-based Siemens AG's optical cable and hardware businesses worldwide and to assume ownership of its co-investments with the company, Siecor Corp. and Siecor GmbH. Under the $1.4 billion agreement, Corning will also assume $120 million in debt.