Optical system & diffraction limit

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Discussion Overview

The discussion revolves around the limitations of optical systems, specifically focusing on the role of diffraction and aberrations in determining resolution. Participants explore the conditions under which diffraction may or may not be the primary limiting factor in optical resolution.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that diffraction will limit the resolution achievable by an optical system.
  • Others question whether systems primarily limited by aberrations can still be considered diffraction limited.
  • One participant notes that the effects of aberrations, such as spherical or chromatic aberration, are primarily seen at the outer parts of the optics, suggesting that central resolution may still be diffraction limited.
  • Another participant states that while diffraction sets a maximum resolution, severe aberrations can lead to a situation where the system is limited by those aberrations instead.
  • An optical engineer explains that the absolute limit to resolution is defined by the diffraction limit, represented by the airy disk pattern, but acknowledges that real systems are typically aberration limited.
  • There is a recognition that significant efforts are made in optical design to minimize aberrations.

Areas of Agreement / Disagreement

Participants generally agree that diffraction limits resolution but express differing views on the conditions under which aberrations may take precedence as the limiting factor. The discussion remains unresolved regarding the interplay between diffraction and aberrations in practical optical systems.

Contextual Notes

Participants highlight the complexity of optical systems, noting that the presence of aberrations can alter the expected diffraction limit, but the exact conditions under which this occurs are not fully resolved.

Kamdinsh
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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.
 
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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
 
davenn said:
yes ( not just may limit ... it WILL limit)

Does that include systems which are primarily limited by aberrations?
 
Drakkith said:
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.
 
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Drakkith said:
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 PFDave
 

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