Patent ID: 7595272

Claim:
An optical glass that is a fluorophosphate glass comprising, as essential cationic components, P 5+ , Al 3+ , at least two members selected from Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ as divalent cationic components (R 2+ ) and Li + and comprising, by cationic %, 10 to 45% of P 5+ , 5 to 30% of Al 3+ , 0 to 20% of Mg 2+ , 0 to 25% of Ca 2+ , 0 to 30% of Sr 2+ , 0 to 33% of Ba 2+ , 1 to 30% of Li + , 0 to 10% of Na + , 0 to 10% of K + , 0 to 5% of Y 3+ , and 0 to 15% of B 3+ , the molar ratio of the content of F − to the total content of F − and O 2− , F − /(F − +O 2− ), being 0.25 to 0.85, the optical glass (1) having a refractive index (N d ) of 1.40 to 1.58 and an Abbe's number (ν d ) of 67 to 90, and (2) exhibiting a transmittance (excluding a reflection loss on sample surfaces) of at least 80% over a wavelength range of 400 nm to 2,000 nm when a glass sample having flat surfaces in parallel with each other and having a thickness of 10 mm is prepared and light is caused to enter the sample from the direction perpendicular to the above surfaces.