BK7 Optical Glass | N-BK7 Crown Optical Substrate - Felix Glass
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- Felix Glass Co., Limited
- Issue Time
- Oct 21,2026
Summary
N-BK7 is a widely used crown glass for visible & NIR optics. Felix Glass provides precision BK7 windows, lenses, prisms with AR coatings for imaging and laser systems.
BK7 Optical Glass
Overview
BK7 optical glass, also named N-BK7, is a standard borosilicate crown optical glass and the workhorse material for visible and near-infrared optical design. It features excellent optical homogeneity, low bubble and striae grade, stable chemical performance and easy polishing.
BK7 has good transmission from 350 nm to 2.2 μm. It is widely preferred when designers need cost-effective, high-quality substrates for visible light systems. Compared with fused silica, BK7 is cheaper, but its transmission drops sharply below 300nm UV band. BK7 remains the mainstream material for general imaging, low-power visible lasers and laboratory optical components.
Key Optical & Physical Properties
| Transmission Range | 350 nm – 2.2 μm |
|---|---|
| Refractive Index (@632.8nm) | 1.5168 |
| Abbe Number | 64.17 |
| Knoop Hardness | 610 Knoop |
| Density | 2.51 g/cm³ |
| Coefficient of Thermal Expansion | 7.1 ×10⁻⁶ /K |
Common Optical Components We Fabricate
- BK7 plano-convex, plano-concave, biconvex spherical lenses
- BK7 optical protective windows, cover plates and flat substrates
- Right-angle prisms, beam splitter prisms, equilateral prisms
- Custom BK7 blanks, wedges and optical flats
Coating Options
We provide standard coatings optimized for BK7 visible optics:
- Single-layer & broadband AR coating for visible spectrum (400–700nm)
- AR coating for 532nm, 633nm, 1064nm laser wavelengths
- Anti-reflection coating for VIS-NIR combined band
- Chrome / aluminum reflective coating for prisms and mirrors
Typical Applications
- Industrial vision imaging and machine vision lenses
- Educational optics, laboratory test assemblies
- Low-power visible laser systems, alignment optics
- Photography optics and beam shaping components
- Optical measurement, autocollimator instruments
Machining Capability
Felix Glass processes high-grade N-BK7 blanks with strict internal quality control. Surface scratch/dig quality up to 20/10; surface flatness can reach λ/10 @632.8 nm. We can produce round, square, rectangular and angled BK7 optics with tight angular and dimensional tolerances for volume and prototype orders.
Datasheet & Custom Inquiry
Download our BK7 material datasheet for full dispersion curve and design parameters. Send your drawing, target wavelength and coating requirements to get a custom quotation.
Request Datasheet & Custom Quote