Optical glass

Abstract

An optical glass that contains Si, Al, Mg, and O is provided. The optical glass contains Si in an amount of 40% or more and 60% or less, in cation percent, Al in an amount of 10% or more and 35% or less, in cation percent, and Mg in an amount of 20% or more and 35% or less, in cation percent. In the optical glass, the total amount of Si, Al, and Mg is 99.5% or more, in cation percent. Furthermore, the optical glass contains Fe and Na each in an amount of 0.01 wtppm or less and has a transmittance to a light having a wavelength of 248 nm of 40% or more at a thickness of 5 mm.

1 . An optical glass comprising Si, Al, Mg, and O,
 wherein said optical glass contains Si in an amount of 40% or more and 60% or less in cation percent, Al in an amount of 10% or more and 95% or less in cation percent, and Mg in an amount of 20% or more and 35% or less in cation percent, a total amount of Si, Al, and Mg being 99.5% or more in cation percent, and   wherein said optical glass contains Fe and Na each in an amount of 0.01 wtppm or less and has a transmittance, to a light having a wavelength of 248 nm, of 40% or more in a thickness of 5 mm.   
     
     
         2 . An optical glass according to  claim 1 , wherein said optical glass contains an OH group in an amount of 5000 wtppm or less. 
     
     
         3 . An optical glass according to  claim 1  or  2 , wherein said optical glass has a refractive index, to a light having a wavelength of 248 nm, of 1.57 or more.