Abstract: The optical glass of the present invention comprises a composition in terms of weight ratio within the range of 0 to 14.8 wt % of SiO2, 30 to 60 wt % of B2O3, 0 to 17.5 wt % of Al2O3, 0 to 0.4 wt % of Li2O, 0 to 3 wt % of Na2O, 0 to 3 wt % of K2O, 0 to 5 wt % of MgO, 0 to 30 wt % of CaO, 0 to 30 wt % of SrO, 0 to 35 wt % of BaO, where RO (MgO+CaO+SrO+BaO) is 8 to 35 wt %, 0 to 20 wt % of ZnO, 0 to 6.5 wt % of La2O3, 0 to 15 wt % of Gd2O3, 0 to 15 wt % of Y2O3, 0 to 10 wt % of Ta2O3, 0 to 9.5 wt % of ZrO2, 0 to 1 wt % of As2O3, and 0 to 0.5 wt % of Sb2O3; and has a refractive index (nd) of 1.52 to 1.65, an Abbe number (vd) of 55 to 61, and an 80% transmission wavelength (at a thickness of 10 mm including no reflection loss) of 330 nm or shorter.

Abstract: The optical glass of the present invention comprises a composition in terms of weight ratio within the range of 0 to 14.8 wt % of SiO2, 30 to 60 wt % of B2O3, 0 to 17.5 wt % of Al2O3, 0 to 0.4 wt % of Li2O, 0 to 3 wt % of Na2O, 0 to 3 wt % of K2O, 0 to 5 wt % of MgO, 0 to 30 wt % of CaO, 0 to 30 wt % of SrO, 0 to 35 wt % of BaO, where RO (MgO+CaO+SrO+BaO) is 8 to 35 wt %, 0 to 20 wt % of ZnO, 0 to 6.5 wt % of La2O3, 0 to 15 wt % of Gd2O3, 0 to 15 wt % of Y2O3, 0 to 10 wt % of Ta2O3, 0 to 9.5 wt % of ZrO2, 0 to 1 wt % of As2O3, and 0 to 0.5 wt % of Sb2O3; and has a refractive index (nd) of 1.52 to 1.65, an Abbe number (vd) of 55 to 61, and an 80% transmission wavelength (at a thickness of 10 mm including no reflection loss) of 330 nm or shorter.

Abstract: Dense crown optical glass comprises, in percent by weight:______________________________________ SiO.sub.2 20-28 B.sub.2 O.sub.3 24-34 BaO 17-32 CaO 5-7 Al.sub.2 O.sub.3 2-6 La.sub.2 O.sub.

Abstract: Optical glass of high refractive index and low dispersion comprises 25-40% of B.sub.2 O.sub.3 11-30% of ZnO, 28-44% of La.sub.2 O.sub.3, 1-25% of Y.sub.2 O.sub.3, 0-20% of alkaline earth metal oxides, 0-5% of SiO.sub.2, 0-5% of Al.sub.2 O.sub.3, 0-15% of PbO, 0-10% of ZrO.sub.2 and 0-10% of Ta.sub.2 O.sub.5, all percentages being by weight.

Abstract: In thorium-free optical glass containing oxygen ions and fluorine ions as anions, cations in the glass calculated as oxides are in the following ranges of percentage by weight:______________________________________ B.sub.2 O.sub.3 10-44, La.sub.2 O.sub.3 30-66, Y.sub.2 O.sub.3 4-31, ZrO.sub.2 0-11, Ta.sub.2 O.sub.5 0-21, Gd.sub.2 O.sub.3 0-12, Nb.sub.2 O.sub.5 0-19, RO 0- 9, PbO 0-10, TiO.sub.2 0- 8, and GeO.sub.2 0-26, ______________________________________where RO is an ingredient or a combination of two or more ingredients of MgO, CaO, SrO, BaO and ZnO, and part of the oxygen ions is substituted for 0.2 to 10% by weight of fluorine ions relative to the glass. The thorium-free optical glass has a refractive index of 1.71 to 1.85 and Abbe number of 40 to 57.