| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain optical glass having a low partial variance ratio (θg, F) and suppressed in time dependent deterioration of spectral transmittance, while its refractive index (n<SB POS="POST">d</SB>) and Abbe number (ν<SB POS="POST">d</SB>) lie within a desired range, and to obtain a preform and an optical element using the same. <P>SOLUTION: The optical glass contains 10.0-40.0 mass% SiO<SB POS="POST">2</SB>component and 1.0-50.0 mass% Nb<SB POS="POST">2</SB>O<SB POS="POST">5</SB>component based on the whole glass mass in a composition in terms of oxide, and has an Abbe number (ν<SB POS="POST">d</SB>) of ≥15 to ≤30 and the partial variance ratio (θg, F) which satisfies the following relations for the Abbe number (ν<SB POS="POST">d</SB>): (-0.00160×ν<SB POS="POST">d</SB>+0.63460)≤(θg, F)≤(-0.00480×ν<SB POS="POST">d</SB>+0.73500) in the range of ν<SB POS="POST">d</SB>≤25, and (-0.00250×ν<SB POS="POST">d</SB>+0.65710)≤(θg, F)≤(-0.00250×ν<SB POS="POST">d</SB>+0.67750) in the range of ν<SB POS="POST">d</SB>>25. <P>COPYRIGHT: (C)2012,JPO&INPIT |
