Coma optical aberration

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Coma aberration:

Definition of coma aberration:

Spherical aberration that occurs in off-axis of an optical system is called as coma aberration.

Optical system with coma aberration:

When all the refracted rays doesn’t  passes through the center of focus in non optical axis results in coma aberration and the below diagram describes how a coma will look like

coma aberration

 

Coma aberration free optical system:

aberration free optical system

This is how an optical system with coma aberration free looks like.

Properties of coma aberration:

transverse ray aberration for coma

  • Coma has very undesirable characteristics
  • Aberration increases linearly with increase in field angle 
  • Comatic image cant be improved by focal shift
  • In general, Lateral shift too don’t improve the image image quality 

Reference:

W T Welford FRS, “Aberrations of optical systems”, Adam hilger imprint by IOP publishing Ltd, ISBN 0-85274-564-8, 1991.

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