Glass Type: Optical Glass
Description
SCHOTT N-BK7® is an optical glass with high transmission and is virtually free of bubbles and inclusions. SGP can CNC mill, drill, cut, lap, and polish this material to many shapes, sizes, and surface finishes.
| Thermal Properties | Mechanical Properties | ||||||
|---|---|---|---|---|---|---|---|
| Thermal Coefficient of Expansion | (0/300°C): 70 X 10 -7/°C | Density | 2.51 g/cm3 | ||||
| Annealing Point | 550°C/1022 °F | Knoop Hardness | 610 | ||||
| Softening Point | 719°C /1326 °F | Young's Modulus | 8.20 X109 dynes/mm2 | ||||
| Strain Point | 624°C/1155 °F | Poisson's Ratio | .206 | ||||
| Chemical Properties | Electrical Properties | ||||||
|---|---|---|---|---|---|---|---|
| Hydrolytic Resistance | class 2 | Dielectric Constant | N/A | ||||
| Acid Resistance | class 1 | Resistivity | N/A | ||||
| Alkali Resistance | class 1 | Dielectric Strength | N/A | ||||
| Optical Properties | |||
|---|---|---|---|
| Refractive Index | 1.509 | ||
Schott N-BK7 is the industry-standard optical crown glass widely recognized for its exceptional purity, high homogeneity, and cost-effective performance. As an eco-friendly, lead- and arsenic-free alternative to classic BK7 glass, N-BK7 delivers high-grade optical clarity without sacrificing environmental safety, making it the premier choice for commercial and precision optics worldwide.
Characterized by a stable refractive index (nd = 1.5168) and a high Abbe number (vd = 64.17), N-BK7 offers minimal chromatic dispersion and superb light transmission throughout the visible and near-infrared (NIR) spectrums. It features low bubble and inclusion content, excellent mechanical hardness, and chemical stability under standard operating conditions, ensuring high yield during precision grinding and polishing.
With its outstanding balance of structural uniformity, optical clarity, and broad stock availability, Schott N-BK7 serves as the benchmark material for optical designs where reliable quality and cost efficiency are paramount.
Characteristics of Schott N-BK7 Glass:
- High Optical Clarity and Transmittance: Delivers high transmission across the visible spectrum and into the near-infrared region (approx. 350 nm to 2,000 nm).
- Exceptional Optical Homogeneity: Available in high homogeneity grades (up to H4), ensuring minimal wave-front distortion in high-precision applications.
- Low Chromatic Dispersion: A high Abbe number (vd = 64.17) minimizes chromatic aberration, making it ideal for color-correcting doublet lenses.
- Eco-Friendly Composition: Fully RoHS and REACH compliant, manufactured without toxic heavy metals like lead and arsenic.
- Superior Surface Polishability: Hard, durable glass structure enables surface polishes to sub-nanometer roughness levels and tight scratch-dig tolerances.
- Low Inclusion and Bubble Content: Produced under strict manufacturing controls to guarantee high internal purity and minimal internal scattering.
- Predictable Mechanical & Thermal Stability: Features consistent physical properties and moderate thermal expansion suitable for standard ambient environments.
- Good Chemical Stability: Highly resistant to chemical staining and atmospheric corrosion under normal optical laboratory and industrial conditions.
Top Five Industries and Applications of Schott N-BK7 Glass:
- Optics and Photonics:
- Standard singlet and doublet optical lenses (plano-convex, biconvex, achromatic).
- Precision prisms, beam splitters, corner-cube retroreflectors, and optical windows.
- Substrates for antireflective (AR), dielectric, and metallic mirror coatings.
- Medical and Life Sciences:
- Lenses and optical assemblies for surgical endoscopes and diagnostic instruments.
- Microplate reader windows, flow cell optics, and microscopy components.
- Optical elements for automated blood analyzers and bio-imaging equipment.
- Defense and Aerospace:
- Target designator optics, laser rangefinder components, and alignment systems.
- Periscope prisms and heads-up display (HUD) optical relay systems.
- Protected internal camera optics and alignment sensors for aviation.
- Industrial and Machine Vision:
- Focusing and collimating lenses for industrial laser diode modules.
- High-resolution camera lenses and filters for automated inline inspection systems.
- Precision optical encoders, reticles, and alignment targets for robotics.
- Research and Metrology:
- Reference optical flats, interferometer optics, and precision beam splitters.
- Spectroscopy components, light guides, and alignment cubes.
- Custom optical prototypes and educational optical bench setups.
Schott N-BK7 Glass remains the definitive baseline material in modern optical engineering. Its combination of optical clarity, high polishability, structural uniformity, and affordability makes it an indispensable asset across virtually every optical sector.
SGP is a trusted leader in precision glass machining and fabrication, backed by years of expertise working with Schott N-BK7 glass across a wide range of industries and applications.
Whether you’re seeking more information about this high-performance material, or need a quote for your specific project, our team is here to help. Contact us today with your questions or requirements—we’re ready to support your application from concept to completion.