| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical glass having a refractive index (n<SB POS="POST">d</SB>) and an Abbe number (ν<SB POS="POST">d</SB>) which are in each desired range, a small partial dispersion ratio (θg, F), and heightened transparency to visible light, and to provide a preform and an optical element using the optical glass. <P>SOLUTION: The optical glass contains in mol%, a ≤60.0% SiO<SB POS="POST">2</SB>component and a ≤25.0% Ta<SB POS="POST">2</SB>O<SB POS="POST">5</SB>component to a total amount of a glass material of a composition in terms of oxides, and the partial dispersion ratio (θg, F) satisfies following relations with the Abbe number (ν<SB POS="POST">d</SB>): in the range of ν<SB POS="POST">d</SB>≤25, (-0.00160×ν<SB POS="POST">d</SB>+0.63460)≤(θg, F)≤(-0.00563×ν<SB POS="POST">d</SB>+0.75573), and in the range of ν<SB POS="POST">d</SB>>25, (-0.00250×ν<SB POS="POST">d</SB>+0.65710)≤(θg, F)≤(-0.00340×ν<SB POS="POST">d</SB>+0.70000). <P>COPYRIGHT: (C)2013,JPO&INPIT |
