Definition of coma aberration:
Spherical aberration that occurs in off-axis of an optical system is called as coma aberration.
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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 free optical system:
This is how an optical system with coma aberration free looks like.
Properties of coma aberration:
- 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
W T Welford FRS, “Aberrations of optical systems”, Adam hilger imprint by IOP publishing Ltd, ISBN 0-85274-564-8, 1991.