Abstract: An optical glass wherein an amount of change in refractive index (?n: difference in refractive index between a state before radiation and a state after radiation) caused by radiation of laser beam at wavelength of 351 nm having average output power of 0.43 W, pulse repetition rate of 5 kHz and pulse width of 400 ns for one hour is 5 ppm or below is provided. The optical glass comprises a fluorine ingredient and/or a titanium oxide ingredient and/or an arsenic oxide ingredient. The optical glass suffers little change in refractive index by radiation of strong light having wavelengths of 300 nm to 400 nm such as ultraviolet laser.

Abstract: An optical glass wherein an amount of change in refractive index (?n: difference in refractive index between a state before radiation and a state after radiation) caused by radiation of laser beam at wavelength of 351 nm having average output power of 0.43W, pulse repetition rate of 5 kHz and pulse width of 400 ns for one hour is 5 ppm or below is provided. The optical glass comprises a fluorine ingredient and/or a titanium oxide ingredient and/or an arsenic oxide ingredient. The optical glass suffers little change in refractive index by radiation of strong light having wavelengths of 300 nm to 400 nm such as ultraviolet laser.

Abstract: An optical glass wherein an amount of change in refractive index (?n: difference in refractive index between a state before radiation and a state after radiation) caused by radiation of laser beam at wavelength of 351 nm having average output power of 0.43 W, pulse repetition rate of 5 kHz and pulse width of 400 ns for one hour is 5 ppm or below is provided. The optical glass comprises a fluorine ingredient and/or a titanium oxide ingredient and/or an arsenic oxide ingredient. The optical glass suffers little change in refractive index by radiation of strong light having wavelengths of 300 nm to 400 nm such as ultraviolet laser.

Abstract: An optical glass wherein an amount of change in refractive index (&Dgr;n: difference in refractive index between a state before radiation and a state after radiation) caused by radiation of laser beam at wavelength of 351 nm having average output power of 0.43W, pulse repetition rate of 5 kHz and pulse width of 400 ns for one hour is 5 ppm or below is provided. The optical glass comprises a fluorine ingredient and/or a titanium oxide ingredient and/or an arsenic oxide ingredient. The optical glass suffers little change in refractive index by radiation of strong light having wavelengths of 300 nm to 400 nm such as ultraviolet laser.

Abstract: An optical glass wherein an amount of change in refractive index (&Dgr;n: difference in refractive index between a state before radiation and a state after radiation) caused by radiation of laser beam at wavelength of 351 nm having average output power of 0.43W, pulse repetition rate of 5 kHz and pulse width of 400 ns for one hour is 5 ppm or below is provided. The optical glass comprises a fluorine ingredient and/or a titanium oxide ingredient and/or an arsenic oxide ingredient. The optical glass suffers little change in refractive index by radiation of strong light having wavelengths of 300 nm to 400 nm such as ultraviolet laser.

Abstract: An optical glass comprises the following composition in mass percent of: SiO2 18-29%; PbO 68-78%; and TeO2 0.1-3.5%; wherein the glass has optical constants which are a refractive index (nd) having a range of 1.75 to 1.87 and an Abbe number (&ngr;b) having a range of 21 to 28; and a wavelength of a light transmitted through the glass having a thickness of 10±0.1 mm at a transmittance of 80% by including a reflection loss, is not more than 420 nm.

Abstract: An optical glass wherein an amount of change in refractive index (&Dgr;n: difference in refractive index between a state before radiation and a state after radiation) caused by radiation of laser beam at wavelength of 351 nm having average output power of 0.43W, pulse repetition rate of 5 kHz and pulse width of 4OO ns for one hour is 5 ppm or below is provided. The optical glass comprises a fluorine ingredient and/or a titanium oxide ingredient and/or an arsenic oxide ingredient. The optical glass suffers little change in refractive index by radiation of strong light having wavelengths of 300 nm to 400 nm such as ultraviolet laser.

Abstract: An optical glass having optical constants of refractive index within the range of 1.55-1.75 and Abbe number (.nu. d) within the range of 25-51 and having large negative anomalous dispersion which is substantially free of lead and arsenic compounds includes as its essential ingredients in weigth percent 10->40% SiO.sub.2, 12.5-35% B.sub.2 O.sub.3, 3-20% ZrO.sub.2 and 6-30% Nb.sub.2 O.sub.5.

Abstract: An optical glass which is a SiO.sub.2 --TiO.sub.2 --K.sub.2 O--RO (where R represents Mg, Ca, Sr, Ba and Zn metal elements) system glass of a specific content range exhibits optical constants of a refractive index (Nd) of about 1.58-1.78 and Abbe number (.nu.d) of about 28-45, is free of PbO and has an improved property against devitrification.

Abstract: An optical glass which is a SiO.sub.2 --B.sub.2 O.sub.3 --(TiO.sub.2 +ZrO.sub.2)--SrO--BaO--R'.sub.2 O system of a specific composition range exhibits optical constants of a refractive index (Nd) of 1.57-1.75 and Abbe number (.nu.d) of 30-55, is free of PbO and has improved stability against devitrification and tinting and improved chemical durability.

Abstract: An optical glass consisting basically of a B.sub.2 O.sub.3 -La.sub.2 O.sub.3 - ZrO.sub.2 -Nb.sub.2 O.sub.5 -PbO-BaO (and/or ZnO) system is free from a poisonous CdO or ThO.sub.2 component and has an excellent light transmission property in a transition region from an ultraviolet portion to a visible portion as compared with conventional optical glasses having the same optical properties.

Abstract: An optical glass consisting essentially of a B.sub.2 O.sub.3 --La.sub.2 O.sub.3 --Gd.sub.2 O.sub.3 --WO.sub.3 --ZrO.sub.2 and/or Ta.sub.2 O.sub.5 system has high refractive and low dispersive characteristics with optical constants of 1.85-1.96 for Nd and 43-28 for .nu.d, is free of poisonous ThO.sub.2, CdO and BeO ingredients, and suitable for mass production.

Abstract: An optical glass consisting basically of a B.sub.2 O.sub.3 -- SiO.sub.2 -- La.sub.2 O.sub.3 -- ZrO.sub.2 -- TiO.sub.2 -- ZnO -- BaO system can be produced at a lower melting temperature and in a shorter melting time than it has heretofore been possible by replacing Ta.sub.2 O.sub.5, Nb.sub.2 O.sub.5 and WO.sub.3 used in the conventional optical glasses with ZnO.