| 摘要 |
It is known to make glass products, especially rods for use in facsimile and LED lens arrays, which have a gradient of refractive index between their central and peripheral portions by permeating into micropores of porous borosilicate glass a solution of dopant, e.g. CsNO3, or Pb(NO3)2 in an amount of up to 40g/100ml of water, and leaching out part of the dopant to form the desired gradient of dopant, solidifying the dopant in the pores and drying the rod and heat treating to collapse the pores.
<??>To provide a high gradient of refractive index without causing instability of the glass during heat treatment with loss of transparency, the dopant now used is TINO3; if an alkali metal compound, e.g. CsNO3 is used therewith the concentration of TINO3 can be increased from not more than 80g TINO/100 ml water to 100 to 400 g/100 ml; preferably lead nitrate is also used. |
