Patent ID: 6811606
Filing Date: 2004-11-02
Classification: C30B,G02B,G03F,Y10S

Abstract:
A manufacturing method for a single crystal of calcium fluoride, having its optical properties improved through an annealing process comprising the steps of:providing a single crystal of calcium fluoride in a sealable container, sealing said sealable container, then heating said sealable container with a heater arranged external to said container such that a temperature inside said sealable container is raised to a first temperature, which is lower than a melting point of said single crystal of calcium fluoride, maintaining the temperature inside said sealable container at said first temperature for a designated period of time, and lowering the temperature inside said sealable container to a second temperature at a first rate, and lowering of the temperature inside said sealable container from the second temperature at a second rate, wherein said first rate is 2Â° C./hour or less, said second rate is 3Â° C./hour or less, the first rate is lower than the second rate, the first temperature is between 1020Â° C. to 1150Â° C., and the second temperature is between 600Â° C. to 900Â° C.