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
Properties of coma aberration :
- Coma has very undesirable characteristics
- Aberration increases linearly with increase in field angle
- Comatic image can’t be improved by focal shift
- In general, Lateral shift too don’t improve the image image quality
Coma aberration free optical system:
This is how an optical system with coma aberration free looks like
James C Wyant, Katherine Creath, “Applied Optics and Optical Engineering,” Academic Press Inc, Vol. XI, pp. 03-39, ISBN 0-12-408611-X, 1992.