Please don’t allow the concept of the Fourier transform to intimidate you! The Fourier plane is simply the focal plane of a converging optical lens such as the lens of the eye. This is the plane that most of us as children used with a magnifying glass to image the sun and burn holes in leaves, paper,etc. If this puts one off in believing that the eye would never be so constructed, consider that pupillary constriction of the eye limits the amount of light allowed to enter the eye and that we never look directly into a bright source such as the sun. Moreover, in this explanation, this constriction is controlled not only by the intensity but also by wavelength of incident light. This wavelength is determined by the diameter of rod receptors and corresponds to the precise short wavelength limit of visual response determined by the rod-to-rod appositional distance. In the Fourier equation information about the image is encoded at this plane in two terms (instead of one if the eye were the analogue of a camera) light amplitude (related to intensity) and phase. Lying behind the Fourier plane is the “image plane” used by cameras and other imaging devices to form an image. These images are formed using only light amplitude and not phase information. The eye therefore possesses a superior ability to utilize phase detection in it’s image-forming process!
Perhaps obscure (I will write more about this) , the retina actually performs the second transform of a “Fourier Pair” (Zernike) reconstituting an image from the first diffractive FT of the lens of the eye.
