Convolution of a gaussian function and a hole

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Discussion Overview

The discussion revolves around the convolution of a Gaussian function with a circular aperture, specifically exploring the use of Fourier transforms in this context. Participants are interested in the implications for calculating the spot size of a Gaussian signal after passing through the aperture.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the appropriate functions to use for convolution with a Gaussian function and whether RMS can be applied in this context.
  • Another participant asserts that RMS is not relevant to convolutions or Fourier transforms and emphasizes that the Fourier transform of a Gaussian is also a Gaussian.
  • A participant acknowledges the irrelevance of RMS but seeks clarification on its potential use as an alternative approach.
  • Further clarification is requested regarding the understanding of convolution and its mathematical properties, specifically the relationship between certain Banach algebras and the Fourier transform.
  • One participant expresses frustration, asserting their understanding of convolution and questioning the relevance of the responses to their original inquiry about modeling the physical phenomenon.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the relevance of RMS to the discussion, with some asserting its irrelevance while others seek to clarify its potential applicability. The discussion remains unresolved regarding the best approach to model the physical phenomenon described.

Contextual Notes

There are unresolved assumptions about the definitions of the functions involved and the specific nature of the "hole" referenced in the convolution. The mathematical steps related to the convolution and Fourier transform are not fully explored.

Newser
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Hello,

I want to do the convolution of a gaussian function and a hole. If I want to use Fourier transform which functions should I use? Can I use rms? I want to calculate the spot size of a gaussian signal after a circular aperture.

Thanks!
 
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Newser said:
Hello,

I want to do the convolution of a gaussian function and a hole. If I want to use Fourier transform which functions should I use? Can I use rms? I want to calculate the spot size of a gaussian signal after a circular aperture.

Thanks!

rms has nothing to do with either convolutions or Fourier transforms. Use the Fourier transform for whatever function you mean by a "hole". Fourier transform of a Gaussian is also a Gaussian.
 


Thanks for the reply. Yes, I know rms has nothing to do with Fourier transform, I was asking if I could use it instead...
 
Last edited:


Newser said:
Thanks for the reply. Yes, I know rms has nothing to do with Fourier transform, I was asking if I could use it instead...

Instead of what ?

It has nothing to do with the Fourier transform. It has nothing to do with convolution.

You question involved convolution.

Do you understand what convolution is ? And do you understand the relationship between the convolution algebra L^1(\mathbb R^n) and the algebra C_0( \mathbb R^n) ?

Both are Banach algebras and the Fourier transform is a continuous homomorphism from L^1(\mathbb R^n) to C_0( \mathbb R^n) which is injective but not surjective. Thus the Fourier transform can sometimes be used to calculate convolutions that are difficult to calculate directly. It takes convolutions (hard to understand) to pointwise multiplication (easy to understand).
 


Yes, I do understand what a convolution is, I think you are the one not understanding my question. I am not asking how to calculate a convolution, obviously if I am talking about Fourier transform I know how to do this...I was wondering about the most suited way to model this physical phenomenon (beam after aperture). But I guess I shouldn't have posted in this section of the forum, I thought I would found multi-skilled people...
 
Last edited:

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