Optical glass for polarizing optical system, production process therefor and polarizing beam splitter

An optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10−8 cm2/N] with respect to a wavelength of 633 nm, the optical glass having the following composition (2):

• composition (2):
• when represented in terms of mol %:
• SiO2O:
• 40.0-54.0 mol %
• R2O (R:
• alkali metal):
• 0.5-9.0 mol %
• PbO:
• 43.0-45.5 mol %
• As2O3+Sb2O3:
• 0.1-1.5 mol %;
• and
• the composition (2) further containing fluorine in the following range when represented in terms of mol %:
• fluorine/oxygen (F/O) ratio:
• 0.1-18.0.

An optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10−8 cm2/N] with respect to a wavelength of 633 nm, the optical glass having the following composition (3):

• composition (3) when represented in terms of mol %:
• SiO2:
• 40.0-54.0 mol %
• R2O (R:
• alkali metal):
• 0.5-9.0 mol %
• RF:
• 0-16.0 mol %
• R2SiF6:
• 0-3.3 mol %
• PbO+PbF2:
• 43.0-45.5 mol %
• PbF2:
• 0-10.0 mol %
• As2O3+Sb2O3:
• 0.1-1.5 mol %;
• and
• the composition (3) further containing fluorine in the following range in terms of mol %:
• fluorine/oxygen (F/O) ratio:
• 0.1-18.0.

A process for producing an optical glass for polarizing optical system, the process comprising:

• changing the ratio of Pbo in a lead-containing optical glass to control the photoelastic constant C thereof to provide an optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10−8 cm2/N] with respect to a wavelength of 633 nm,
• the optical glass having the following composition (1):
• composition (1):
• when represented in terms of wt. % of oxides:
• SiO2:
• 17.0-27.0% (35.5-57.0 mol %)
• Li2O+Na2O+K2O:
• 0.5-5.0% (0.7-20.0 mol %)
• PbO:
• 72.0-75.0% (39.1-45.0 mol %)
• As2O3+Sb2O3:
• 0.1-3.0% (0.1-2.0 mol %).

A process for producing an optical glass for polarizing optical system, the process comprising:

• changing the fluorine/oxygen (F/O) ratio of a fluorine-containing optical glass so as to regulate the refractive index thereof while retaining the photoelastic constant C of the optical glass in the range of substantially zero to provide an optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10−8 cm2/N] with respect to a wavelength of 633 nm,
• the optical glass having the following composition (2):
• composition (2):
• when represented in terms of mol %:
• SiO2:
• 40.0-54.0 mol %
• R2O (R:
• alkali metal):
• 0.5-9.0 mol %
• PbO:
• 43.0-45.5 mol %
• As2O3+Sb2O3:
• 0.1-1.5 mol %;
• and
• the composition (2) further containing fluorine in the following range when represented in terms of mol %:
• fluorine/oxygen (F/O) ratio:
• 0.1-18.0.

A process for producing an optical glass for polarizing optical system, the process comprising:

• changing the fluorine/oxygen (F/O) ratio of a fluorine-containing optical glass so as to regulate the refractive index thereof while retaining the photoelastic constant C of the optical glass in the range of substantially zero to provide an optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10−8 cm2/N] with respect to a wavelength of 633 nm, the optical glass having the following composition (3):
• composition (3) when represented in terms of mol %:
• SiO2:
• 40.0-54.0 mol %
• R2O (R:
• alkali metal):
• 0.5-9.0 mol %
• RF:
• 0-16.0 mol %
• R2SiF6:
• 0-3.3 mol %
• PbO+PbF2:
• 43.0-45.5 mol %
• PbF2:
• 0-10.0 mol %
• As2O3+Sb2O3:
• 0.1-1.5 mol %;
• and
• the composition (3) further containing fluorine in the following range in terms of mol %:
• fluorine/oxygen (F/O) ratio:
• 0.1-18.0.