Title:
PRODUCTION OF FLUORIDE CRYSTAL AND FLUORIDE CRYSTAL LENS
Document Type and Number:
Japanese Patent JP3697008
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To prevent the deterioration of a transmissivity characteristic at the time of repeatedly irradiating a light having short wavelength and high output for a long time by annealing a crystal obtained by forming a mixture of a fluoride starting material and a scavenger into disk shape, melting it and cooling gradually.
SOLUTION: The mixture obtained by mixing the fluoride starting material and 0.05-5mol.% scavenger in a rotating vessel is molten by heating to a temp. higher than the melting point of the fluoride, then the molten matter is cooled to be crystallized, and the crystal is formed into disk shape. After removing a surface layer of the disk like fluoride crystal 305 by 1-2mm thickness, the crystal is put into a cylindrical crucible 304, and after heating the crystal to a temp. higher than the melting point of the fluoride with a heater 303 to melt the crystal, the molten matter is cooled to crystallize under 0.1-5.0mm/hr rate of temp. fall, then the crystal is annealed at 900-1000°C for 20-30hr to obtain the fluoride crystal. Then, an antireflection film is formed at need on the surface of a lens obtained by an external diameter working of the fluoride crystal.
Inventors:
Oba point
Toshio Ichizaki
Toshio Ichizaki
Application Number:
JP3018497A
Publication Date:
September 21, 2005
Filing Date:
February 14, 1997
Export Citation:
Assignee:
Canon Inc
International Classes:
G02B1/02; C30B11/00; C30B29/12; G02B3/00; (IPC1-7): C30B29/12; C30B11/00; G02B1/02; G02B3/00
Domestic Patent References:
| JP9315893A | ||||
| JP1115897A | ||||
| JP50019696A |
Attorney, Agent or Firm:
Hisao Fukumori