| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical material which has a large negative abnormal dispersibility and is useful as a raw material for various optical apparatuses.SOLUTION: An optical material includes particles comprising a rare earth phosphate. When an Abbe number and a partial dispersion ratio of the particles are denoted by &ngr;and &thetas;, respectively, &ngr;ranges from 30 to 100 and &Dgr;&thetas;, which is defined by expression (1): &Dgr;&thetas;=&thetas;-(-1.665×10&ngr;+5.213×10&ngr;-5.656×10&ngr;+0.7278), ranges from -0.10 to -0.01. It is preferable that the rare earth phosphate has a monoclinic crystalline structure. |
