N-BK7 Optical Glass for Industrial Laser & Precision Measurement
N-BK7 is the most widely used crown optical glass for visible-spectrum industrial and laboratory optical systems. Felix Glass supplies custom BK7 blanks, lenses, prisms, protective windows and optical flats for industrial laser marking machines, visible light measuring instruments and general precision optical equipment. It delivers excellent homogeneity, stable transmission across visible wavelengths and cost-effective custom CNC machining for North American optical equipment suppliers.
Understanding N-BK7 Crown Glass
N-BK7 is a borosilicate crown optical glass manufactured by SCHOTT, offering a refractive index of approximately 1.5168 at 587.6 nm (d-line) with an Abbe number around 64.2. Its high transmission in the visible and near-infrared spectrum, combined with excellent chemical durability and low bubble content, makes it the default substrate for lenses, prisms, beam splitters and optical windows in industrial laser systems and laboratory instruments.
Felix Glass sources certified N-BK7 blanks and processes them into finished optical components through in-house CNC grinding, precision polishing and coating lines. Every batch is accompanied by material certification and surface inspection reports for full traceability from blank to finished part.
Core Material Advantages
Five key reasons why N-BK7 remains the first choice for visible-spectrum industrial optical systems.
High Optical Homogeneity
Uniform refractive index with minimal internal impurities, ideal for visible-light laser systems, alignment optics and routine spectral measurement.
Stable Visible Light Transmission
Perfect transmittance from 350 nm to 2.5 μm, well-suited for industrial laser marking, machine vision and optical calibration under normal temperature.
Easy CNC Machining & Polishing
Soft enough for fast precision grinding, cutting and surface polishing to λ/4 flatness, lowering prototype and mass production costs compared to sapphire and fused silica.
Balanced Mechanical Performance
Moderate scratch resistance with stable mechanical structure at working temperatures up to 550°C, suitable for indoor industrial and laboratory environments.
Cost-Effective OEM Customization
Lower raw material cost than sapphire and fused silica, supporting small-batch R&D prototypes and large-volume OEM orders for standard visible optical components.
Main Application Scenarios
N-BK7 optical components serve a wide range of visible-light industrial and laboratory applications.
Industrial Laser Marking & Processing
BK7 lenses, beam splitters and protective viewports for fiber laser marking, engraving and low-power industrial laser equipment. Stable performance under continuous visible laser output.
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Visible Light Precision Measuring Instruments
Optical flats, prisms and viewing windows for machine vision, dimensional inspection devices and laboratory optical calibration systems working in visible spectrum.
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General Laboratory Optical Research
Standard optical blanks for university teaching labs, low-power optical testing and visible-spectrum experiment setups that do not require deep UV transmission.
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General-Purpose Custom Optical Components
Cost-effective custom optical parts for indoor sensor modules, inspection cameras and low-temperature industrial optical equipment without extreme UV or high-temperature requirements.
Custom BK7 opticsOur BK7 Processing Services
End-to-end CNC fabrication, coating and packaging for industrial-grade optical components.
Full CNC Cutting, Grinding & Chamfering
Precision shaping for custom blanks, lenses, prisms and windows to your exact dimensional specifications.
Surface Polishing to λ/4 Flatness
Measurement-grade optical surface quality for demanding visible-light instrument applications.
Anti-Scratch & AR Coating
Hard coating and visible-spectrum anti-reflection AR coating to reduce surface reflection and abrasion during industrial operation.
Clean-Room Packaging
Standard clean-room packaging for laboratory and industrial equipment integration, ready for immediate assembly.
Flexible MOQ
Small prototype batches for R&D validation and mass OEM manufacturing for full-scale production runs.
Material Performance Comparison
How N-BK7 compares with fused silica and sapphire across key optical material properties.
| Property | N-BK7 | Fused Silica | Sapphire |
|---|---|---|---|
| Mohs Hardness | 6 | 5.5 | 9 |
| Max Continuous Working Temp | 550°C | 1100°C | 1700°C |
| UV Transmission | Poor | Excellent | Excellent |
| Visible Transmission | Excellent | Good | Good |
| Saltwater Corrosion Resistance | Poor | Good | Perfect |
| Typical Usage | Industrial laser, visible measurement | UV lab, spectrum calibration | High temp, subsea, aerospace |
Industry Standards & Quality Certifications
Surface Quality: 60-40 Scratch-Dig
Standard MIL-PRF-13830B surface quality for industrial laser and measurement optics. Tighter 40-20 or 20-10 grades available for high-precision instruments.
Dimensional Tolerance: ±0.02 mm
CNC-machined to ISO 2768-mK fine tolerance, verified by CMM inspection for every production batch.
Flatness: λ/4 at 632.8 nm
Interferometer-verified surface flatness for measurement-grade optical components. λ/10 available for critical applications.
Full Material Traceability
Every BK7 blank is traceable to its original melt batch with certified refractive index, Abbe number and transmission data.
Frequently Asked Questions
Is BK7 suitable for UV spectrum testing equipment?
No. N-BK7 absorbs deep UV light below 350 nm. For UV testing, choose fused silica instead. If you need help selecting the right UV-transmitting material, our optical engineers can assist with material recommendations.
What coating options do you provide for BK7 optical parts?
We offer visible-band anti-reflection AR coating and anti-scratch hard coating to reduce surface reflection and abrasion during industrial operation. Custom multi-layer coatings are available upon request.
Can BK7 windows work in high-temperature furnace environments?
Not recommended. BK7 softens above 550°C; use sapphire for sustained high-temperature furnace observation viewports. For applications near the temperature limit, consult our engineering team for a material suitability review.
What dimensional tolerance can we achieve for custom BK7 prisms and lenses?
Standard dimensional tolerance ±0.02 mm, surface flatness λ/4, meeting most industrial laser and measuring instrument standards. Tighter tolerances may be achievable for specific applications—please provide your drawing for a detailed capability assessment.
Do you accept small prototype orders for laser equipment R&D?
Yes, we support small-batch sample orders for equipment testing, plus mass OEM production for US laser equipment manufacturers. Typical prototype lead times and minimum order quantities depend on geometry complexity and coating requirements.
Why North American Equipment Manufacturers Choose Felix Glass
Proven BK7 Supply Chain
Consistent N-BK7 glass blanks from certified suppliers, with full batch traceability and material certification for every order.
Optical Engineering Support
In-house optical engineers review your drawings, recommend polishing grades, and optimize coating selection for your specific equipment.
Flexible Production Scheduling
Dedicated prototype lines for quick-turn R&D samples and parallel mass production capacity for ongoing OEM supply.
Ordering & Lead Time for Custom BK7 Optics
Submit Your Drawing & Requirements
Send your CAD drawing, optical prescription, or dimensional sketch with working wavelength, coating preference and quantity. Our engineers review within 24 hours.
Engineering Review & Quotation
We evaluate material feasibility, recommend polishing grade and coating selection, and provide a detailed quotation with lead time estimate.
Prototype Sampling & Approval
Small-batch prototypes shipped for your equipment testing and validation. Typical prototype lead time is 2-4 weeks depending on geometry complexity.
Mass OEM Production & Delivery
After prototype approval, we scale to full production with consistent quality. Standard OEM lead time is 4-8 weeks with flexible shipping options.
Request Custom BK7 Optics
If you need cost-effective N-BK7 optical lenses, prisms, protective windows or custom blanks for industrial laser marking, machine vision or laboratory visible-light measurement, send your drawing, working wavelength and size requirements. Our optical engineers will provide tailored polishing and coating solutions matched to your equipment.
