3D glasses made simple.
With the huge influx of 3D films exploding into cinema, it might be worth explaining the phenomenon of 3D glasses.
To fully understand the way 3D films and glasses work, we need to understand the basics of eyes:
From the diagram, it’s easy to see that each eye perceives a slightly different image. Humans have an astounding perception of depth and distance – but only in their binocular field of vision. You can put this to the test yourself. If you try to catch a ball with both eyes open, you’ll most likely catch it fine (unless you’re awful at catching…). As soon as you close one eye, it becomes a whole new situation. You’ll find it much harder to catch, because your brain cannot correlate the images from both eyes to perceive the correct distance.
The brain works on the premise that the eyes are roughly 6 inches apart. This way, it uses the two images to come to a “conclusion” about what an image should look like. This helps us perceive the correct distance, depth and see things in 3D.
3D films work in the same way. Two images are projected on the screen at different positions – from very slightly different angles. Most recent films make use of “polarisation” technology; the images on the screen have been polarised to different wavelengths. The glasses you wear have polarised lenses as well. This means only one of the two images can enter each lens. One eye sees one image from one angle, and the other eye sees the remaining image from the other angle.
Speaking in psychological terms, this tricks the brain into believing what you are seeing is actually real. It correlates the two images, as it would in real life, and you perceive a virtual 3D world. It turns the two separate images and gives them a “meaning”; they are turned into a binocular image, allowing you to see distance and depth.
So next time you watch Avatar, Alice in Wonderland, and many of the other 3D films which are critically acclaimed, you know exactly why you’re seeing something that’s not actually 3D!