What is coma in optical systems?

Coma is an optical aberration that causes off-axis point sources to appear distorted.

Coma is a type of aberration that occurs in optical systems, such as telescopes and cameras. It causes off-axis point sources to appear distorted, with a comet-like shape. This distortion is caused by the fact that the light rays passing through the outer parts of the lens do not converge at the same point as those passing through the centre. Instead, they converge at a point slightly off-axis, causing the image to appear distorted.

Coma can be corrected by using specially designed lenses or by adjusting the position of the lens elements. In some cases, it may be possible to correct for coma by using software to process the image after it has been captured. However, this is not always possible, and in some cases, the distortion caused by coma may be severe enough to render the image unusable.

In addition to coma, there are several other types of optical aberrations that can affect the quality of an image. These include spherical aberration, astigmatism, and chromatic aberration. Understanding these aberrations and how to correct for them is an important part of designing and building high-quality optical systems.