How to calculate spatial frequency after taking fft in case of oversampling?

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Swati Jain
Swati Jain 2018-4-2
编辑： Swati Jain 2018-4-3
Hi,
I am calculating Fourier transform of an image. Width of each pixel is 0.004 mm. I re-sample my image at every pixel
dx=0.004; %mm
Fs=1/dx; %pixel/mm
f=Fs*(0:L/2-1)/L; %L is the length of signal in unit of pixel
But, now I want to over-sample my signal and want to re-sample at every half pixel,so I choose the following parameters:
dx=0.004/2;
Fs=1/dx; %pixel/mm
f=Fs*(0:L/2-1)/L; %L is the length of signal in unit of pixel
The Final output I obtain is off by a factor of 2 from the previous case and I think it should not because I am just decreasing re-sampling width and length of the signal is same. I am not sure, if this is correct way of calculating spatial frequency in case of oversampling. Could anyone suggest me in case of oversampling how do we define spatial frequency axis??

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Matt J
Matt J 2018-4-2
If dx has been cut in half, then L must be doubled in order to cover the same continuous space signal.

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