How to realize a Stereoscopic 3D digital photoframe

Step 2 Polarization

Here we call our new, friend, polarization.
What is polarization?

It is a characteristic of light, such as color and intensity, but that you can't see with your eyes.
Think of it as an orientation of the light.
Basically, light is made of photons, that go in random directions.
Using a filter called polarizer, you can force them to go in one precise direction.
If you rotate the filter, you rotate the polarization of the light too.
If you look through a polarizer filter in front oy our eye, to an image with another filter over it, you'll see that if both filters are rotated the same direction, you can see ithe image, if one is rotated 90 degrees and the other is rotated at 0 degrees, you will block exactly the direction you forced the light to go, so.. you wll see a black image.

Now imagine we have two images on the table, both with a polarizer filter over it, one filter rotated at 90 degrees and the other at 180 degrees.

We also have two small flters in fornt of each eye, again one rotated at 90 degrees and the other at 180 degrees;
What we get is the the left eye sees the left image, but not the right one. And same goes for the right eye.

So we have our first achievement: to make sure the each eye sees only what we want it to see.

Is it 3D already? No.
In order to achieve 3D, the tow images must be in the same exact place, one over the other, both visible.

Impossible?