Optical filters
Service stock filters,
Wavelength range UV, VIS, NIR & IR
- Bandpass Filters, HW > 3 % of CWL
- Narrow Bandpass Filters, HW < 3 % of CWL
- Longwave-Pass Filters
- Shortwave-Pass Filters
- Broad-Bandpass Filters
- Neutral Density Filters
Custom design
Technical information
Glossary
Term |
Symbol |
Definition |
|
Wavelength |
λ | Usually stated in nanometers (1 nm = 10-9 m) or microns (1 µm = 10-6 m). |
| Wavenumber | δ | Reciprocal of wavelength, usually expressed in cm-1 (1 µm = 10,000 wavenumbers (cm-1)). |
| Central Wavelength | CWL | Wavelength at the centre of the pass band measured at the half of the peak transmittance point. |
| Transmittance | T | Ratio of the transmitted energy to the incident energy, usually expressed in %. |
| Peak Transmittance | T peak | Maximum of the transmittance. |
| Average Transmittance | T avg | Average of the transmittance. |
| Peak Wavelength | λ peak | Wavelength at the maximum of the transmittance. |
| Bandwidth | HW | Full width of the pass band measured at half the maximum of the peak transmittance. |
| Blocking Region | The region outside the pass band where the filter is designed not to transmit light. Usually expressed as a percentage of the incident energy, blocking is typical less than 0.1 % transmittance. | |
| Cuton / Cutoff Wavelength | λc | Wavelength at which a filter begins/ ceases to transmit. Specified at 5% of the absolute transmittance point. |
| Cuton / Cutoff Slopes | A measure of the transmittance cuton or cutoff slope. Defined as:  |
|
| Half Power Point 1 | HP1 | Wavelength at which a broad band pass filter begins to transmit. Specified at 50% of the peak transmittance. |
| Half Power Point 2 | HP2 | Wavelength at which a broad band pass filter ceases to transmit. Specified at 50% of the peak transmittance. |
| Band Pass Filter | BP | A filter which transmits energy in a specified wavelength band but rejects energy above and below. HW > 3% of CWL. |
| Narrow Band Pass Filter | NB | A filter which transmits energy in a specified wavelength band but rejects energy above and below. HW < 3% of CWL. |
| Broad Band Pass Filter | BBP | A filter which transmits energy in a specified wavelength band but rejects energy above and below. |
| Shortwave Pass Filter | SP | A filter which transmits energy at wavelengths below its cutoff point. Sometimes called a low pass filter. |
| Longwave Pass Filter | LP | A filter which transmits energy at wavelengths above its cuton point. Sometimes called a high pass filter. |
| Neutral Density Filter | ND | A filter which attenuates energy levels accurately in a defined wavelength range. |