| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical glass having refractive index (n) in a desired range and besides, having small Abbe number (ν), further small partial dispersion ratio (θg,F) and enhanced transparency to visible lights, and to provide a preform and an optical element each obtained by using the optical glass.SOLUTION: The optical glass contains, by mass%, SiOcomponent of 15.0% to 50.0%, BaO component of over 0% to 25.0%, LaOcomponent of over 0% to 35.0%, and NbOcomponent of over 0% to less than 30.0%, and a partial dispersion ratio (θg,F) and an Abbe number (νd) satisfy a relations (-0.00162×νd+0.63822)≤(θg,F)≤(-0.00275×νd+0.68125) in the range ofνd≤31 and (-0.00162×νd+0.63822)≤(θg,F)≤(-0.00162×νd+0.64622) in the range ofνd>31. |
