Have you seen Avatar(《阿凡达》)? It's a popular3Dflm, and you may have to wear 3D glasses to see it. The 3D glasses make the images(图像) from the film look as if they are coming straight towards you.
More and more 3D films are coming to theatres. Some say that 3D TV sets will come into our homes in the near future. 3D technology can make TV and films more exciting. However, people with eye problems may get headaches if they spend too much time watching 3D films. Why?
When we look at an object(物体), each eye sees it at a different angle. Our eyes send the two images to our brain(大脑), and the brain puts them together. 3D technology uses two film projectors(投影机). One projects a left—eye image and the other projects a right—eye image. 3D glasses allow us to see a different image in each eye. So, when we are watching a 3D film, our brain can't put together the images. The brain needs to work harder at reading "the images. That makes it easier for people with eye problems to get dizzy(头晕的) or have headaches. A famous eye doctor said if your eyes can't focus(聚焦)on the same object at once, you will have trouble watching 3D films.
