Patent ID: 7001458

Claim:
A process for growing optical fluorite crystals, said process comprising: (a) having a furnace having a melting zone and an annealing zone; (b) placing in the furnace a crucible having (i) a seed crystal unit in the bottom thereof with a seed crystal in said unit, and (ii) a fluorite material to be melted, wherein said crucible and seed crystal unit are placed in the furnace such that the fluorite material to be melted is in the melting zone, and a top portion of the seed crystal within the seed unit is within the melting zone; (c) holding the crucible as described in step (b) in the melting zone for a time for the melt to become homogeneous; (e) moving the crucible and seed crystal unit in a direction such that 10–40% of the seed crystal extends into the melting zone; (f) holding the moved crucible and seed crystal unit in the melting zone for a dime in the range of 10–20 minutes; (g) moving said crucible and seed crystal unit from the melting zone to the annealing zone; and (h) lowering the temperature in a programmed manner to room temperature.