| 摘要 |
There is provided an optical glass with a high refractive index and a low dispersion having a refractive index (nd) of not less than 1.75 and an Abbe's number (&ngr;d) of not less than 35 where the image formation characteristic is hardly affected by changes in temperature of the using environment. SiO2, B2O3 and La2O3 are contained as essential components and the ratio of the constituting components are adjusted whereby an optical glass in which a product of α and &bgr; where α is an average linear expansion coefficient at −30 to +70° C. and &bgr; is an optical elasticity constant at the wavelength of 546.1 nm is not more than 130×10−12° C.−1×nm×cm−1×Pa−1 is able to be achieved.
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