The Spectroscopy Net
Gateway to Spectroscopy > Spectrometers > Design concepts > Aberrations


The rays emanating from any point on a source and travelling different paths though a spectrometer will not converge to ideal points on the detector. This divergence (blurring) is called aberration. The main types of aberration are:

  • spherical aberration: some rays focus in line with the paraxial (design) focal point but focus before or after it;
  • coma: some rays focus in the focal plane but are off to the side of the paraxial (design) focal point;
  • astigmatism: some rays focus both not in the focal plane and off to the side of the paraxial (design) focal point.

For further reading see:

J F James and R S Sternberg, The Design of Optical Spectrometers, Chapman & Hall, London (1969).

For a more general but demanding discussion of optical design see

R R Shannon, The Art and Science of Optical Design, Cambridge University Press, Cambridge (1997).

First published on the web: 15 March 2000.

Author: Richard Payling