GLASS HAVING LOW PHOTOELASTIC CONSTANT

摘要

A glass having a low photoelastic constant, which contains, in mass % in terms of an oxide, 35 % or more and less than 49 % of P2O5, 30 to 55 % of BaO, and more than 0.5 % of Tl2O, is free of lead, exhibits a photoelastic constant (beta) at a wavelength of 546 nm in the range of -0.25 X 10<-6>nm.cm<-1>.Pa<-1> to +0.30 X 10<-5>nm.cm<-1>.Pa<-1>, and has a refractive index (nd) of 1.60 or more.