# Optical system & diffraction limit

• Kamdinsh

#### Kamdinsh

can you please let me know if this sentence is true about optical systems or not?
"Diffraction may limit the resolution achivable by an optical system"
Thanks.

yes ( not just may limit ... it WILL limit)

now had you pasted you question into google, you would come up with dozens of links telling you that and why it happens

Dave

yes ( not just may limit ... it WILL limit)

Does that include systems which are primarily limited by aberrations?

Does that include systems which are primarily limited by aberrations?

Im no optics expert :)

good Q ;) maybe, depending on the type of aberration ? take spherical or chromatic aberration ... they effects are mainly seen around the
outer part of the lens/mirror, and it may be quite bad ... I have seen more than one poorly ground telescope mirror over the years ;)
I would expect that maybe for the central part of the optics, resolution is still diffraction limited

The final / fundamental resolution limit is due to diffraction.

Dave

While diffraction limits the maximum possible resolution an optical system may have, I'd say that an optical system can be limited by aberrations and not diffraction if the aberrations are severe enough.

Optical engineer here. The absolute limit to the resolution of an optical system is known as the diffraction limit. The spot you get is an airy disk pattern, which is 2.44 *(lamda)*F/#. This means that with no aberrations, i.e. a perfect optical system, that is the smallest spot size you can get. As you introduce aberrations the spot size increases and deforms according to the aberrations present. So if you have any aberrations present, the system is now limited by the aberrations and not the diffraction limit. Because no real system is perfect, all physical optical systems are in fact aberration limited. However, giving a quick look at the first order diffraction limit to a system is a great way to get an idea about how well a theoretical system could work for a given job.

berkeman and davenn
While diffraction limits the maximum possible resolution an optical system may have, I'd say that an optical system can be limited by aberrations and not diffraction if the aberrations are severe enough.

Agreed, and that is why so much effort goes into design to eliminate them :)

Thanks for your input mrlgravesl :)

and welcome to PF

Dave