| 摘要 |
PURPOSE:To obtain the title glass form with the refractive index distribution smoothly corrected by making a heating treatment after ion exchange treatment of a glass form in a molten salt lower in diffusion rate than that used in said ion exchange process. CONSTITUTION:A refractive index distribution-type lens (GI lens) is dipped into a molten salt (normally NaNO3) to carry out ion exchange treatment followed by dipping the resultant lens into a second molten salt lower in diffusion rate and greater in specific gravity than NaNO3 (pref. RbNO3, CsNO3, Sr(NO3)2, Ba(NO3)2, etc.) to make a heating treatment, thus accomplishing refractive index distribution correction. It is preferable that the treatment temperature be higher than the ion exchange treatment temperature by 20-50 deg.C (i.e., 470-500 deg.C) and the treatment time 10-30min. |
