Boron Crown
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Optical Glass
Steps nd/νd
Tolerances according to ISO 12123 for refractive index (0.5: ±0.0001; 1: ±0.0002; 2: ±0.0003; 3: ±0.0005) and Abbe number (0.5: ±0.1%; 1: ±0.2%; 2: ±0.3%; 3: ±0.5%)
Refractive Index nd
Refractive index at the yellow helium line at 587.5618 nm
Refractive Index ne
Refractive index at the green mercury line at 546.0740 nm
Abbe Number νd
Abbe number is a measure for the dispersion. It is calculated by νd=(nd-1)/(nF-nC)
Abbe Number νe
Abbe number is a measure for the dispersion. It is calculated by νe=(ne-1)/(nF-nC)
Standard Dispersion nF - nC
Standard dispersion results from the difference of the refractive indices nF-nC
Principal Dispersion nF' - nC'
Principal dispersion results from the difference of the refractive indices nF'-nC'
Relative Partial Dispersion Pg,F
The relative partial dispersion Pg,F of the spectral lines g and F is derived the equation Pg,F= (ng - nF)/(nF - nC).
Deviation Of Relative Partial Dispersion ΔPg,F
Deviation of the relative partial dispersion from the normal line between the g- and F-line
Humidity Resistance Class CR
Climate resistance is resistance to moisture in the air expressed in CR classes 1 (high) to 4 (low).
Stain Resistance Class FR
Stain resistance class in accordance with SCHOTT optical filter glass catalog.
Acid Resistance Class SR
Acid resistance class in accordance with ISO 8424.
Alkali Resistance Class AR
Alkali resistance class in accordance with ISO 10629.
Phosphate Resistance Class PR
Resistance to alkaline phosphate containing solutions according to ISO 9689 expressed in PR classes 1 (high) to 4 (low).
Thermal Expansion α(-30/+70)
Linear coefficient of thermal expansion in 10-6/K in the temperature range [-30°C to +70°C].
Transformation Temperature Tg
Transformation temperature in °C according to ISO 7884-8
Temperature Viscosity T107.6
Temperature of the glass in °C at which the glass has a viscosity of 107.6 dPa·s
Density ρ
Density in g/cm³
Knoop Hardness HK[0.1/20]
Knoop Hardness HK[0.1/20] in accordance with ISO 9385.
N-BK10
N-BK7HT