Fourier transform of a picture?
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Hi, I'm trying to create a model that simulates a lens with fourier optics. Studying fourier optics I have this formula:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/359164/image.png)
Now, when d=f we have a simple fourier transform. Now I think that matlab doesn't put f (that states for focal lenght) in the exponential. How can I change the factors in the exponential?
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Bjorn Gustavsson
le 11 Sep 2020
Note that the actual Fourier transform is the second row of your equation, while the first factor you can see as a matrix with normalization coefficients that varies over the Fourier-plane (main contribution here is to include a spatial variation of the phase due to optical path-lengths differences). Just calculate the FFT of your image, then calculate the normalization-coefficient-matrix, take care to calculate u and v correctly scaled, and use sensible values for f, k and lambda. That should be manageable. The f in the Fourier-transform is just a scaling-factor - accounting for the scaling of the u and v coordinates - those are given by the optical system and your image-size.
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