Why do we need to wear 3d glasses?

When you view the world, you do so through two eyes separated by about 2.5 inches. This creates a parallax difference since each eye sees things from a different angle. Your brain interprets this as depth. (Try walking around your house with one eye covered - you'll be walking into things at first). 3D movies accomplish the same thing by using two cameras separated by a horizontal distance. But for your eye/brain system to recreate the depth effect, the left eye must see ONLY the left camera view and the right eye must see ONLY the right camera view. That's what the glasses accomplish. For home 3D TV systems, all current ones, AFAIK, use active shutter glasses (not polarized glasses). The TV alternates frames between the left and right views and the glasses are synced with that. In theaters, active shutter glasses are not used - they're far too expensive at over $100 each. Instead they use either polarized glasses matched to polarized projectors (Real3D), or narrow band color glasses matched to identical filters on the projectors (Dolby3D).

Because the effect of 3D is created when your left eye and right eye see different images and your brain stacks them on top of each other as one image. The glasses have polarized lenses so that each eye gets a different spectrum of the image on screen. It would be nearly impossible to do this without glasses, at least with the current technology.

Actually there are 3d televisions that don't require glasses to see 3d. They are called autostereoscopic televisions. Here on yahoo answers I have answered questions from people who have seen these televisions. On guy saw one at some Disney World type park in England. He said you could just walk up to the tv with no glasses on and things would pop out in front of the screen. There are still some problems with them that they are fixing, but they do work. The thinking is they will become available at stores for home use in 2 or 3 years. Don't know why but you hardly hear about these televisions.

Let me put this in the simplest way possible screen do special thing eyes cant see special thing need special glasses to see special thing.

It's not that simple. You can't 'put the technology of the glasses into the tv' because you are forgetting about the technology of the human eyes. We see 3D because there is a space between our eyes, which gives them slightly different view points and when our brain combines them, we see the world in three dimensions. We have to wear 3D glasses to make sure the correct 'view' enters the correct eye. Glasses-less 3D displays are being worked on, but they still have their problems. You have to be in exact correct position to see the effect and this isn't practical for home television. There are also issues with picture clearity that are side effect of the prisms needed on the surface of the screen to direct the light in different directions. Holograms? That requires a completely different process to create still 3D photographs. There currently is no way to make it work with motion images.

There is a technology being developed that uses multiple screens on top of each other to create virtual 3D. The images will not have the strong wow effect (at lease not at first) but it will be 3D with no glass. I call it mild 3D. Give it few years and it will be here. And holograms are here but not for TV's just yet.

Samsung and others have not figured out how to display the image for the left eye without the right eye seeing it too unless you use glasses.

'3D Without Glasses' Tech Improving, But Needs Work

agreed it is so stupid