Kabushiki Kaisha Ohara

Kabushiki Kaisya Ohara

Tatsuya Senoo

Muneo Nakahara

Satoru Matsumoto

Akira Masumura

Katsuhiko Yamaguchi

Hisao Yatsuda

An optical glass wherein an amount of change in refractive index (&#x394;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.

Optical glass suffering little change in refractive index by radiation of light

An optical glass wherein an amount of change in refractive index (&#x394;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.

A low alpha-ray level glass which emits only an extremely small amount of alpha-ray while maintaining excellent chemical durability, coefficient of thermal expansion and hardness is obtained by introducing fluorine into a SiO.sub.2 --B.sub.2 O.sub.3 --Al.sub.2 O.sub.3 --R.sub.2 O (R being an alkali metal) system glass of a specific content range. The amount of alpha-ray emitted from this glass is below 0.02 count/cm.sup.2.hr.

Low alpha-ray level glass and method for manufacturing the same

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.

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Sagamihara, Japan

Tatsuya Senoo