What this application demands
Analytical instruments are judged by what they can measure at the bottom of their range. Stray light, autofluorescence and coating pinholes all set a floor beneath which a real signal cannot be distinguished from an artefact, and no amount of signal averaging recovers information that the optical path has already destroyed. This is why scientific optics are specified around rejection and background rather than around peak transmission.
Where the instrument is a spectrometer, spectral precision and the accuracy of the wavelength scale matter most. Where it is a fluorescence microscope, the requirement shifts to blocking the excitation band while passing the much weaker emission, often within a few tens of nanometres.
Specifications we recommend
| Component | Typical specification | Why |
|---|---|---|
| Spectrometer filters | Edge and band-pass filters with steep transitions and deep blocking | Prevents order overlap and stray light from reaching the detector |
| Fluorescence filter sets | Excitation, dichroic and emission filters as a matched set | The set has to work together, not as three independent parts |
| Quartz sample windows | Low-autofluorescence fused silica, both faces AR-coated | Keeps the background low in weak-signal measurements |
| Reference and calibration plates | Polished substrates with verified flatness and transmission | Provides a stable baseline for the instrument |
Failure modes we design against
Pinholes and coating defects are the most common source of unexpected background: a single pinhole in a blocking filter passes a disproportionate amount of excitation light straight onto the detector. Dense blocking specifications combined with careful handling and cleaning protocols address this, and where the application is critical we inspect for pinholes specifically.
Autofluorescence from the substrate is the second issue in fluorescence work. Ordinary glass fluoresces enough to matter when the signal is weak, which is why fused silica is used for the optical elements closest to the sample. Advice on which elements genuinely need quartz — and which do not — is part of the design review rather than an automatic upcharge.
Frequently asked questions
Do you supply complete fluorescence filter sets?
Yes — excitation, dichroic and emission filters designed together for the fluorophore, so the set works as a system.
How low can background be?
It depends on the blocking specification and the substrate. Send the detection limit and we will specify a set that supports it.