Transcript:

So, let us look at Fourier transforms. So, what Fourier transforms do is that they convert a given function, let us say, in the time domain, to another function in the frequency domain. And then the function in the frequency domain is easier to analyze or to work on.

The good thing about the Fourier transform is if you know the inverse Fourier transform, if I give you an inverse Fourier transform, you can recreate the original signal. So, this is how it works. The original signal is this function of time, and what Fourier did was he multiplied that by this complex integral, and he integrated over all time, and that gives him the Fourier transform. And if I have the Fourier transform, I can always invert it to get to the original function.

Now, why is this important? Because this is how the eye enables the brain to see. So, this is what is happening.

In the eye, there is this lens, and that is the centre line of the lens. And what is happening in the lens is it is getting light from the outside, which it is focusing on the retina. This is the retina, right? And this light is coming in at an angle theta, let us say. Except there is more than one light ray.