Optical Glass, Preform for Precision Press Molding and Method of Manufacturing Thereof, Optical Element and Method of Manufacturing Thereof

摘要

The present invention relates to an optical glass having a refractive index (nd) of greater than or equal to 1.65 and an Abbé number (ν(nu)d) of greater than or equal to 50 for use in precision press molding. The glass exhibits that a ratioα(alpha)1/α(alpha)2 is less than 17 when temperature denoting maximum value of differential in amount of elongation of glass relative to temperature differential DELTAT (where DELTAT denotes a constant value of 1° C. or less) over a temperature range from glass transition temperature (Tg) to sag temperature (Ts) is denoted as T1, average coefficient of linear expansion over a range from T1−5° C. to T1+5° C. is denoted as alpha1, and average coefficient of linear expansion over a range from the glass transition temperature (Tg)−160° C. to the glass transition temperature (Tg)−140° C. is denoted as alpha2.