Optical glass, preform for precision press molding, and optical element

An optical glass comprising, denoted as cationic percentages:

• BO1.5
• 20 to 70 percent;
• LaO1.5
• 6 to 30 percent;
• GdO1.5
• 4 to 25 percent;
• SiO2
• 0 to 20 percent;
• LiO0.5
• 0 to 10 percent;
• ZnO
• 0 to 28 percent;
• ZrO2
• 0 to 8 percent;
• TaO2.5
• 0 to 10 percent;
• TiO2
• 0 to 8 percent;
• NbO2.5
• 0 to 8 percent;
• WO3
• 0 to 10 percent;
• YbO1.5
• 0 to 3 percent;
• GeO2
• 0 to 5 percent;
• as well as O and F,
• with the F/O molar ratio of the F content to the O content being 0.01 to 0.30;
• the combined sum of twice the LiO0.5 content, the ZnO content, and ½ the F content (2LiO0.5+ZnO+(F/2)) when the total quantity of cations is denoted as 100 being 26 percent or greater;
• the value of twice the LiO0.5 content divided by the combined sum of twice the LiO0.5 content and the ZnO content (2LiO0.5/(2LiO0.5+ZnO)) being 0.7 or less;
• the combined sum of the ZnO content, three times the ZrO2 content, and 5 five times the TaO2.5 content (ZnO+3ZrO2+5TaO2.5) being 55 percent or less;
• the value of BB—(BO—BB) falling within a range of −60 to 0, with the value BB being 1.5 times the content of BO1.5 denoted as a cationic percentage, the total quantity of all cations in the glass being denoted as 100, and the molar ratio of the total oxygen content relative to this total quantity being denoted as BO;
• the refractive index nd being 1.825 to 1.90;
• the Abbé number vd being 35 to 43;
• the degree of the refractive index and dispersion represented by nd−(2.25−0.01×vd) being 0.009 or greater;
• and
• the glass transition temperature Tg being 570° C. or lower.