Thread Subject:

change signs after ifft2 ?

I have an image which I first fft2 to fourier space and then multiply with an exponential function. After that, I ifft2 the whole thing. In order to test if the program is working well, I've tested with using exp(i0), which is 1, which means that after ifft2, the image should be exactly the same as my starting image. However, I found half of the data points with an opposite sign. Can anyone tell me why it is like that? and how to fix this?
Thanks in advance!