Optical Bandpass Filters
Precision interference bandpass filters for wavelength selection in fluorescence, spectroscopy, machine vision and laser systems. Narrow band (FWHM 1-10nm) and broadband designs from UV to NIR with high out-of-band blocking (OD 4-6).
Key Specifications
Material Options
Select the optimal optical material based on your wavelength, power, thermal environment and mechanical requirements.
- BK7 — Standard substrate for visible-NIR bandpass filters. Cost-effective and widely available.
- UV Fused Silica — For UV bandpass filters (< 400nm) or applications requiring higher LIDT.
- Borosilicate (BK7 equivalent) — Alternative substrate with similar optical properties. Good for fluorescence and machine vision.
Coating Options
Coatings are engineered around your specific wavelength and operating conditions.
- Narrow Bandpass (FWHM 1-10nm) — Hard-coated multi-cavity interference design. For laser line selection, Raman spectroscopy and fluorescence.
- Standard Bandpass (FWHM 10-40nm) — Multi-cavity design for machine vision, sensor filtering and wavelength isolation.
- Broadband Bandpass (FWHM 40-100nm) — Fewer cavity design for broad spectral selection. VIS, NIR or custom ranges.
- Multi-band Bandpass — Dual or triple passband in a single filter. For multi-fluorophore imaging.
Manufacturing Tolerances
We optimize specifications to match your system requirements — not over-specify. Tighter tolerances increase cost without always improving system performance. Typical manufacturing capabilities:
- Surface quality: from 60-40 to 10-5 scratch-dig
- Surface flatness: from λ/4 to λ/20 per inch
- Dimensional tolerance: ±0.01mm to ±0.05mm
- Centration: <3 arc min standard, <30 arc sec precision
Inspection & Quality
Every component undergoes 100% inspection before shipment with full documentation including interferometer reports, spectral curves, surface quality images and dimensional data.
- Laser interferometry: λ/100 resolution
- Spectrophotometry: 190nm – 25μm
- Surface inspection: MIL-PRF-13830B compliant
- Dimensional metrology: ±0.01mm accuracy
Applications
- Fluorescence microscopy excitation and emission filters
- Raman spectroscopy Rayleigh line rejection
- Machine vision wavelength-specific inspection
- Laser line selection and cleanup
- Environmental monitoring gas sensing
- Astronomical photometry filters
- Medical diagnostics and flow cytometry
- LiDAR signal filtering
Engineering Considerations
Bandwidth selection: Narrower bandwidth (FWHM 1-3nm) provides better spectral isolation but lower peak transmission and higher cost. Choose the widest bandwidth that still provides adequate signal-to-noise for your application.
Angle tuning: Bandpass filters shift to shorter wavelengths when tilted from normal incidence (~0.1-0.3% per degree). This can be used for fine wavelength tuning, but for fixed-wavelength applications, maintain consistent AoI.
Blocking level: OD 4 (10,000:1 rejection) is sufficient for most applications. For fluorescence with strong excitation sources, OD 6 may be needed to suppress excitation leakage. Specify both the passband and the blocking range.
Frequently Asked Questions
Related Products
Related Technical Resources
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