OPTICAL ELEMENT ESPECIALLY OF ZINC SULPHIDE OR SELENIDE HAVING IMPROVED OPTICAL QUALITY

摘要

Articles of polycrystalline zinc sulphide and zinc selenide achieve substantially improved optical quality by a treatment of heat and isostatic pressure by means of an inert working fluid, e.g. argon. The treated specimens are transparent and have substantial transmission in the infrared and visible range of the spectrum. Additional improvement in the transmission characteristics is achieved by wrapping the specimens in a foil of an inert material prior to treatment. Temperatures from 700 DEG C to 1050 DEG C and pressures from 34 MPa to 205 MPa may be used over periods from 3 hours upwards.