Abstract: Preforms for precision press molding made of optical glass, optical elements, and methods of manufacturing the same are provided. The preforms are suited to precision press molding having a broad range of dispersion characteristics, a low glass transition temperature, a low sag point, and good resistance to devitrification while containing no PbO. The optical element is obtained by precision press molding the preform. One example of the preform has a refractive index (nd) of greater than or equal to 1.7 and an Abbé number (vd) of less than or equal to 32. The other example of the preform has an Abbé number (vd) exceeding 32.

Abstract: An optical glass being free of lead and fluorine, having a low glass transition temperature permitting press-molding with a mold formed of stainless steel and having high climate resistance includes an optical glass comprising, by mol %, 25 to 44% of P2O5, 10 to 40% of a total of Li2O, Na2O and K2O, 5 to 40% of ZnO, 1 to 35% of BaO and at least one components selected from Nb2O5, Bi2O3 and WO3, having a glass transition temperature (Tg) of 370° C. or lower and being free of lead and fluorine and an optical glass which is free of lead and fluorine, has a mass loss ratio of less than 0.25% when immersed in pure water, and has a glass transition temperature (Tg) of 370° C. or lower.

Abstract: An optical glass having a refractive index (nd) of 1.57 to 1.67, an Abbe's number (&ngr;d) of 55 to 65 and a glass transition temperature (Tg) of 560° C. or lower and having a low-temperature softening property and excellent climate resistance or a haze value of 3% or less, or an optical glass comprising, by mol %, 22 to 40% of B2O3, 12 to 40% of SiO2, 2 to 20% of Li2O, 5 to 15% of CaO, 2 to 14% of ZnO, 0.5 to 4% of La2O3, 0 to 3% of Gd2O3, 0 to 3% of Y2O3, the total content of La2O3, Gd2O3 and Y2O3 being at least 1%, 0 to 5% of Al2O3, 0 to 3% of ZrO2 and 0 to 5% of BaO, the total content of the above components being more than 96%, and having a refractive index (nd) of 1.57 to 1.67 and an Abbe's number (&ngr;d) of 55 to 65.

Abstract: Provided are optical glass exhibiting a refractive index (nd) in a range of 1.75 to 1.87, an Abbé number (&ngr;d) in a range of 80 to 45, and excellent low-temperature softening properties even when not incorporating Th2O5 as well as permitting a low production cost; a precision press molding preform and an optical element comprised of such glass; a method of manufacturing the preform; and a method of manufacturing the optical element. The optical glass comprises, in a molar percent, 30 to 45 percent of B2O3, 2 to 15 percent of SiO2, 10 to 20 percent of La2O3, 1 to 10 percent of TiO2, 10 to 30 percent of ZnO, 2 to 15 percent of Li2O, higher than 0 percent and 10 percent or less of WO3, 0 to 15 percent of Nb2O5, and 0 to 10 percent of ZrO2, wherein the total amount of the above-mentioned components is higher than 95 percent, the glass exhibits a refractive index (nd) in a range of 1.75 to 1.87, and an Abbé number (&ngr;d) in a range of 80 to 45.

Abstract: Disclosed is an optical glass comprising, expressed as weight percentages, greater than or equal to 18 percent and less than 30 percent of SiO2, greater than or equal to 12 percent and less than 23 percent of BaO, 22 to 37 percent TiO2, greater than or equal to 7 percent and less than 16 percent Nb2O5, 5 to 20 percent of Na2O, 0 to 6 percent of K2O, 0 to 5 percent of CaO, 0 to 5 percent of SrO, 0 to 4 percent of ZrO2, 0 to 3 percent of Ta2O5, 0 to 1 percent of Sb2O5, and greater than or equal to 0 percent and less than 0.5 percent of P2O5, and by essentially not comprising PbO, As2O3, and F. The optical glass exhibits a refractive index (nd) greater than or equal to 1.80 and an Abbé number (vd) less than or equal to 30. A method of manufacturing a glass material for press molding is disclosed.