Bandpass Filters

Bandpass Filters

Bandpass Filters

A bandpass filter is an inexpensive optical filter used as a wavelength selector that allows transmission of a predetermined wavelength while rejecting or blocking other wavelengths. Along with our wide selection of standard infrared filters, Optometrics designs and manufactures custom bandpass filters for instrument manufacturers world wide.

  • Clinical chemistry instrumentation
  • Spectral radiometry
  • Environmental testing
  • Colorimetry
  • Elemental and laser line separation
  • Flame photometry
  • Color separation
  • Fluorescence
  • Immunoassays

Optical Bandpass Filter – Typical Transmission Curve

Filter terminology
Filter Terminology

Transmission Curves are graphs or mathematical functions that characterize optical filters. Typically expressed as the percent or fraction of light transmitted versus wavelength.

  • Bandwidth is a range of wavelength that specifies the transmitted part of the spectrum.
  • Central Wavelength (CWL) is the midpoint wavelength of the bandwidth.
  • Peak Transmittance is the maximum percentage of light transmission through the filter. It is often centered at the CWL, but many filters have fairly flat transmittance across the bandwidth.
  • Half Bandwidth (HBW) or Full Width-Half Maximium (FWHM) is the wavelength range that characterizes a bandpass filter. It is bound by the wavelengths where transmittance is half (50%) that of the peak transmission.
  • Upper and Lower Blocking Regions are the ranges of wavelengths where the light is attenuated.

Choosing an Optical Filter

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