Jet Li Birthday Cakes

Applications of Fourier Transform

Unas gafas viejas, o papel de transparencia; la possibility of printing a black and white design on the glass or plastic, and basic knowledge of the Fourier Transform is all you need to build this funny toy:

Without glasses	With glasses

Imagine seeing fireworks with them, or a laser show, or just the traffic at night. Each wavelength on this (ie, each color light intensity) concentrated in an area small enough, see a hologram around the surface, replicating the same color that generates it. In the above example we have only white light.

are generated by computer, and for this reason are called CGH (Computer Generated Hologram). Do not know who invented it, but the idea gave us David Brady Duke University. There is a fantastic patent on the invention, so if you happen to make money copying the idea, you may lose your hair.

started with a black square image, on which is printed on a corner a white pattern.
Your Discrete Fourier Transform in two dimensions we gives a matrix of complex numbers. We consider the argument (angle) of each of the entries in that matrix, which is a number between -180 º and 180 º. If that number is negative, put a zero (or white), and if the number is positive, we put a one (or black). Thus we get a square image like this: The right image is what we have to print on the lenses. When we look through them, we can see the desired effect in this case, we will see word "IMA" instead of "Duke" of course.

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