| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an optical glass having predetermined optical constants by a composition containing no GeO<SB>2</SB>and Ta<SB>2</SB>O<SB>5</SB>at all, which are expensive, and containing a certain amount or more amount of rare earth oxides; and to provide a preform for precision press molding, and an optical element. <P>SOLUTION: The optical glass includes a composition of, in mass%, 0.5-9.0% SiO<SB>2</SB>, 10.0-22.0% B<SB>2</SB>O<SB>3</SB>, 30.0-50.0% La<SB>2</SB>O<SB>3</SB>, 14.0-30.0% Gd<SB>2</SB>O<SB>3</SB>, 0.5-10.0% ZrO<SB>2</SB>, 9.0-18.0% TiO<SB>2</SB>and 1.0-13.5% Nb<SB>2</SB>O<SB>5</SB>, which is constituted so as to satisfy 50.5%≤(La<SB>2</SB>O<SB>3</SB>+Gd<SB>2</SB>O<SB>3</SB>)≤64.0%. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
