Spectrometers and Figures of Merit

Figures of Merit

“Figure of merit” is a generic expression, not specific to spectroscopy, that refers to the specifications considered most useful for comparing the utility of devices or systems. According to Merriam-Webster, the term’s first known use dates to 1865, during the latter part of the Industrial Revolution.

Today, figures of merit identify the most significant specifications in a system and help people weed out those specifications that do not directly correlate to overall performance. For spectrometers, these are the key figures of merit:

• Dynamic Range – ratio between the maximum and minimum signal intensities that a spectrometer can detect
  
  
• Optical Resolution – the resolving power of a spectrometer, typically its ability to discern closely aligned peaks
  
  
• Signal to Noise Ratio – the signal intensity divided by the noise intensity at a particular signal level
  
  
• Sensitivity – a measure of how the optical input (light) relates to the spectral output (counts) in the spectrometer
  
  
• Stray Light – at its simplest, the light that unintentionally lands on any part of the spectrometer’s detector and gives a false reading
  
  
• Wavelength Range – in the context of a spectrometer system, the range of wavelengths over which the device effectively captures and processes incident light
  
  
• Thermal Stability – a measure of how spectral response varies as a function of temperature

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