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 electronic musical instrument with which, without difficulty to a user, it is possible to reproduce and save and the like the musical tones that the user has performed and to carry this out in units having musically satisfactory breaks. For each count of one beat by a beat counter, the time information for the musical tone data that are stored at that timing is stored in a beat time information table. When a skip-back button is operated during the recording, an address having a musically satisfactory break is acquired by computation based on the time information and the storage address of the operation timing, the time information of said table, and the sampling period. Therefore, even in those cases where optimization processing of the memory has been done during the recording, there is no need to update the storage address at that time.

Abstract: An electronic musical instrument with which, without difficulty to a user, it is possible to reproduce and save and the like the musical tones that the user has performed and to carry this out in units having musically satisfactory breaks. For each count of one beat by a beat counter, the time information for the musical tone data that are stored at that timing is stored in a beat time information table. When a skip-back button is operated during the recording, an address having a musically satisfactory break is acquired by computation based on the time information and the storage address of the operation timing, the time information of said table, and the sampling period. Therefore, even in those cases where optimization processing of the memory has been done during the recording, there is no need to update the storage address at that time.

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 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: 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.

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.