Optical Glass Properties
The properties and characteristics of Ohara optical glass necessary for glass handling.
The properties and characteristics of Ohara optical glass necessary for glass handling.
Ohara Corporation Western Office
23141 Arroyo Vista, Suite 200
Rancho Santa Margarita, CA 92688
TEL: (949) 858-5700
FAX: (949) 585-5455
Ohara Corporation Eastern Office
50 Columbia Road, Branchburg
New Jersey 08876-3519
TEL: (908) 218-0100
FAX: (908) 218-1685
Each optical glass has its own properties which are closely connected to the key chemical elements contained therein. In OHARA’s glass type designation system, the first or second characters include the atomic symbols of one or two important chemical elements for that glass type. The third letter of the glass type designation refers to the refractive index of each glass type within its glass group: H, M, or L for high, middle, or low index. Lastly, we assign a one- or two-digit number to each glass type within a given glass family. Thus, each glass type is typically represented by three letters plus a one- or two-digit number. The prefix “S-“ stands for environmentally safe, and the prefix “L-“ is used for low transformation temperature (Tg) glass types. The suffix “Y” is used for i-Line-glass types, and the suffix “W” is used for glasses with improved transmittance. For example, the glass type S-BSL 7 is environmentally safe (S-), contains Boron (B) and Silicon (S), shows a low index (L) and is the seventh (7) glass within this BS glass family. Along with OHARA’s glass type designation, each single glass type is identified by a six-digit code. The first three digits represent the refractive index at the helium line (nd) and the last three digits represent the Abbe number (νd). This six-digit code is internationally recognized within the optical community.
When light enters the glass, it slows down inversely proportional to the refractive index compared to in a vacuum or in air. The refractive index of optical glass is usually expressed as the speed ratio of light in the air to themedium (glass sample).<br>
The refractive index is measured by sending a predetermined wavelength of light into the sample and measuring theminimum deviation angle of the emitted light bent by refraction, according to JIS B 7071-1. For the 20 spectral lines shown in the table below, numerical values are shown to five decimal places. The refractive indices (principal refractive indices) for d-line (587.56 nm) and e-line (546.07 nm) are also shown to six decimal places.
Spectral Line Symbol |
t |
||||
Light Source |
Hg |
Hg |
Hg |
Hg |
Hg |
Wavelength (nm) |
2325.42 |
1970.09 |
1529.58 |
1128.64 |
1013.98 |
Spectral Line Symbol |
s |
A′ |
r |
C |
C′ |
Light Source |
Cs |
K |
He |
H |
Cd |
Wavelength (nm) |
852.11 |
768.19 |
706.52 |
656.27 |
643.85 |
Spectral Line Symbol |
He-Ne |
D |
d |
e |
F |
Light Source |
レーザー |
Na |
He |
Hg |
H |
Wavelength (nm) |
852.11 |
589.29 |
587.56 |
546.07 |
486.13 |
Spectral Line Symbol |
F′ |
He-Cd |
g |
h |
i |
Light Source |
Cd |
レーザー |
Hg |
Hg |
Hg |
Wavelength (nm) |
479.99 |
441.57 |
435.835 |
404.656 |
365.015 |
