Bandpass Filter

Features of and Bandpass Filter

• Center Wavelength: Describes the midpoint of the spectral bandwidth, where the filter’s transmittance reaches its peak at the center wavelength.

  
  

• Full Width at Half Maximum (FWHM): The wavelength width corresponding to half of the peak transmittance, representing the spectral bandwidth of the bandpass filter. Narrowband filters are typically used for laser purification and chemical detection, while broadband filters are used in applications such as fluorescence microscopy.

  
  

• Stopband/Cutoff Band: The low transmittance bands on either side of the filter. The lower the transmittance in the stopband, the better the cutoff effect. High-performance bandpass filters can effectively block stray light and reduce background noise in applications like fluorescence imaging.

  
  

• The design and fabrication of bandpass filters are relatively complex because they require precise control over the positions of the spectral peaks. They are usually made by incorporating special dyes into plastic or glass substrates or by depositing optical films on their surfaces to attenuate specific bands of light while allowing other bands to pass through or be reflected. This design enables bandpass filters to adjust and alter the transmission, reflection, polarization, or phase state of light waves.

  
  

• Bandpass filters are widely used in various fields, including spectroscopy, clinical chemistry, imaging, and wireless transmitters and receivers. In transmitters, bandpass filters limit the bandwidth of the output signal to prevent interference; in receivers, they allow signals within a selected frequency range to be received and decoded while preventing unwanted frequency signals from passing through. Additionally, bandpass filters optimize the signal-to-noise ratio and the sensitivity of the receiver.

Specifications of Bandpass Filter