Advanced Products
Special glass materials for a variety of applications and components
Special glass materials for a variety of applications and components
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
Therefore, we have released the θg, F-νd diagram and the θC, t-νd diagram as means to show the relationship between θx, y and νd of each glass type. In order to numerically express the anomalous dispersibility, 511605 (NSL 7) and 620363 (PBM 2) are used as reference glasses, and the straight line connecting these two glass types is considered the “normal” line. The difference between the “normal” line and the vertical coordinates θx, y of each glass type is calculated as anomalous dispersion Δθx, y (Fig. 2). In this catalog, the partial dispersion ratio is θg, F and θC, t, and the anomalous dispersion is Δθg, F and ΔθC, t.
Although NSL 7 and PBM 2 are not currently produced by Ohara, the conventional NSL 7 and PBM 2 values (Table 2) are used as the reference values .
Reference Values:
θc,t |
θC,A' |
θg,d |
θg,F |
θi,g |
vd |
|
NSL 7 |
0.8305 |
0.3492 |
1.2391 |
0.5436 |
1.2185 |
60.49 |
PBM 2 |
0.7168 |
0.3198 |
1.2894 |
0.5828 |
1.4214 |
36.26 |
>θg,F-νd図とΔθg,F
Relational constant for temperature coefficient of the refractive index
The temperature coefficient of the absolute refractive index of glass for wavelengths not listed in the data sheet can be calculated as a function of wavelength and temperature. Ohara uses the following equation.
| ｎ(λ,T0)： | Refractive index at reference temperature |
| Ｔ0： | Reference temperature (°C) (Ohara defines this as 25°C) |
| Ｔ： | Target temperature (°C) |
| λ： | Vacuum wavelength (μm) |
| D0、D1、 D2、E0、 E1、λTK： | Constant (listed in the data sheet) |
To determine the temperature coefficient of the relative refractive index, refer to the equation given in the previous section, “Temperature coefficient of the refractive index”.
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).
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 |
