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INTRODUCTION
ORDERING
APPLICATIONS

Bandpass Filters

Introduction

Bandpass filters are often used in front of detectors to eliminate or reduce noise due to light at wavelengths different from the wanted signal wavelength. Bandpass filters can be ordered with different bandwidths depending on the need of our customers as seen in the first figure below.

The figure shows three different typical bandpass filters, all manufactured by Ferroperm Optics A/S.

Figur 1 View picture in new window (full size)


Curve A is a measurement of a 6-cavity filter, curve B is a 4-cavity filter and curve C is a narrow 2-cavity filter with a bandwidth of only 3.4 nm. How many cavities you need in a filter depends on your need for Offband Blocking. This is illustrated in the figure below, which shows how effectively an 8-cavity filter is blocking offband compared to a 3-cavity filter.

Figur 2 View picture in new window (full size)

What to consider when ordering bandpass filters

When ordering a bandpass filter from Ferroperm
Optics A/S, the following parameters are important to consider:

  1. Dimensions (e.g. square, circular, size, etc.)
  2. Quantity
  3. Central Wavelength (CWL as seen on curve A)
  4. Half Bandwidth at transmission  (HBW)
  5. Offband blocking
  6. Peak Transmission (Tpeak)

Short list of applications of bandpass filters


  • Photometric measurements within the bio-medical
    field
  • Atomic emissions line filters
  • Environmental analysis measurements
  • Fluorescence measurements within the bio-medical
    field
  • Industrial process control
  • Calibration of optical equipment
  • Laser line filters

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