One of the most known men of all times is Salvador Dali. Even if you don’t know any of his work you can still say you heard of him. He is the creator of the next visual optical illusion and he made some very impressive stereograms in his life. You will soon find out what I meant.
What to see?
If you look at this picture what to you see first: a man or a woman?
Every one of you is correct! In this image there is a man and there is also a woman depending how you look at the painting. If you focus your look with your left eye you will see a woman body, but if you focus your visual attention of your right eye you will see the head of a man.
How does it work?
This kind of illusion is called a stereogram because in a stereoscope a person can see a representation rather than a real image.
Now let’s explain a little the stereogram. It is pair of two-dimensional panels that can depict the view of a scene or an object depending on the vantage points of the right or left eye. In time, this kind of „illusion” was forgotten and in our days people use 3D images created by computers and they are called autostereograms.
In conclusion the stereoscopic imaging is based on the stereoscope that presents a different image to each eye. All this kind of stereo images can be seen normally if they are placed side by side