A narrow bandpass filter is a bandpass filter held to a tighter discipline: the transmitted band shrinks to the width of the feature being measured, and the blocking outside it has to deepen, because the whole point is that the wanted light is weak and the unwanted light is strong. Fluorescence is the textbook case and a documented one here — a customised narrowband-coating green bandpass filter is listed for fluorescent applications.
The second documented anchor is medical testing: a narrow band pass / notch filter line built around a 520 nm centre wavelength (CWL 520 nm) for medical tests. Around those two anchors the documented range extends to 850 and 940 nm narrow band pass filters for face-recognition illumination, an 800 nm optical glass narrow band pass filter, and white-glass narrow band pass versions at 900 and 1640 nm.
Documented Narrow Bandpass Range
| Listing (storefront) | Application | MOQ |
|---|---|---|
| Narrowband coating green bandpass filter | Fluorescence | 10 pieces |
| Narrow band pass filter, CWL 520 nm | Medical test instruments | 10 pieces |
| Narrow band pass filter, 800 nm | Optical glass | 10 pieces |
| Narrow band pass filters, 900 / 1640 nm | White glass versions | 10 pieces |
| Narrow band pass filters, 850 / 940 nm | Face-recognition illumination | 10 pieces |
Specifying a Narrow Bandpass Filter
Centre wavelength and bandwidth lead the specification, followed by the blocking range and the angle of incidence. The catalogue does not record angle behaviour for these listings, so if your instrument illuminates at an angle, state the angle in the enquiry. The bandpass selection guide explains the shift and the tolerance questions in full, and the wider bandpass filters page covers the standard-bandwidth range this page narrows down from.
Frequently Asked Questions
How narrow is 'narrow'?
Narrow enough that centre wavelength and angle of incidence dominate the specification — the documented applications are fluorescence, the 520 nm medical-test filter line, and the 850/940 nm recognition filter lines.
Can the centre wavelength be customised?
Custom centre wavelengths are part of the documented bandpass programme; state yours in the enquiry.
What is the minimum order?
10 pieces on the documented narrow bandpass listings.
Narrow Filters in Production Instruments
Specifying a narrow bandpass filter for a one-off experiment and for a production instrument are different disciplines. In production, the filter's centre wavelength becomes part of the instrument's calibration chain, so the specification conversation includes the tolerance the production line can absorb, the temperature range the instrument will meet, and the angle the filter will actually sit at in the shipped product — three numbers that belong in that conversation if unit two hundred is to measure like unit one. Those are checks on the buyer's side of the specification: the documented catalogue facts about the 520 nm medical-test filter are its centre wavelength and its medical-test use, and what repeatability a production run of it achieves is something the buyer's own qualification testing establishes against the quoted tolerance — it is not a property this catalogue records for that filter. Buyers at that stage should also discuss evaluation quantities honestly — the documented 10-piece minimum suits a design-verification batch, after which the production specification can be frozen with data in hand rather than frozen on hope.
Request a Quotation
Tell us the component, material, dimensions and coating you need. Pricing and lead time for your specification are confirmed in the written quotation.