Wideband or narrowband filters from the VIS to MWIR.
Bandpass coatings transmit only a limited range of wavelengths; while a broad range of wavelengths are effectively blocked (i.e., reflected and/or absorbed). They are widely used wherever there is a need to separate signals from ambient background. Narrow bandpass filters are generally defined as those in which the bandwidth (FWHM) is 10% or less of the center wavelength (e.g. 100 nm FWHM for a 1000 nm center wavelength filter). Wide bandpass filters are just the opposite. Dual bandpass filters feature two passbands, rather than a single one.
DSI BANDPASS FILTER APPLICATIONS
- Laser systems
- Spectroscopy and fluorescence imaging
- Military imaging, target designation and countermeasures
- Digital cinema
- Medical imaging
- Hyperspectral and multispectral sensor systems
THE DSI DIFFERENCE
DSI has extensive experience designing and manufacturing bandpass coatings for use at wavelengths ranging from the visible through the mid-wave infrared. These include broad bandpass, narrow bandpass and even dual (or multi-wavelength) bandpass designs. DSI bandpass filters are characterized by high in-band transmission, strong out of band blocking and immunity to shifts due to changing humidity.
SPECIFYING COST EFFECTIVE BANDPASS COATINGS
For the buyer of bandpass coatings, it’s useful to understand some of the most common design and production tradeoffs in order to avoid writing specifications in a way that drive up cost unnecessarily. The graph here shows the key performance parameters commonly used to specify a bandpass coating.
Definitions of bandpass filter performance parameters. The Out of Band blocking may be specified to start at the first 1% or 0.1% point on either side of the bandpass, or sometimes at a given wavelength away from the half-power point, or even at a particular wavelength. It may be specified as a maximum value, average value, or total integrated power within the blocking range