This part might be a bit overkill, it allows you to create the OTF to deconvolve using a possibly non-cubic PSF possibly smaller than a possibly non-cubic object while all we really need for propagator deconvolution is to convert cubic PSF (for now, same size as the object) to cubic OTF. I have decided to leave it there so the LR deconvolution is a more general function (except for the fact it is hard-coded with 3 dimensions).