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Stereo Vision

Understanding how we see in three dimensions took time.

We can see in three dimensions, because we have two eyes. Each eye sees the world from a slightly different angle. Our brain combines the information from both eyes to work out the distance of objects we are looking at. This is called binocular vision.

Binocular vision was not fully appreciated until the 19th century. Before this time our three dimensional vision was always a bit mysterious.

One early attempt to explain this mystery was the emission theory. Greek scientists such as Euclid and Ptolemy realised that light creates a flat image inside the eye. They suggested that light alone was not enough to explain three dimensional vision and proposed that the eye emitted a substance that mixed with light to allow vision.

The Arabic scientist Al-Haytham discredited the emission theory. While previous scientists had disputed this theory, Al-Haytham was the first to satisfactorily develop the alternative theory with vision caused solely by light entering the eye. Al-Haytham's detailed anatomical studies of the eye, his work on pinhole cameras and his experiments on vision all suggested that perception could be satisfactorily explained by light entering the eye.

A stereograph
magnifyA stereograph image

Al-Haytham's anatomy of the eye
magnifyAl-Haytham's anatomy of the eye
© Museum Victoria Australia