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How Do 3D Glasses Work?

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Dr. Marc Weinstein

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3D technology has been a popular novelty since the first 3D movie came out in 1922. The 3D effect is also used in some still photos and there are even home televisions that can convert shows into a 3D experience. While most people have used 3D glasses before, do you really know how they work? Keep reading as we break down the science behind 3D technology!

What is a 3D Image?

Under normal circumstances, your eyes already see the world from two slightly different angles - one from each eye. You can test this phenomenon by focusing on something, then closing one eye, and then the other. The object you are looking at will move slightly as each eye opens and closes. These separate angles provide depth perceptions and help humans judge the distance between objects in their line of sight.

It's this same concept that allows 3D technology to trick our brains into thinking that two-dimensional images have depth.

When looking at an image in 3D, you are actually seeing two separate angles of the same image that have been superimposed on top of each other. In a classic 3D scenario one of the angles is projected in red and the other in blue. The corresponding red lens on your 3D glasses filters out all the red in the image causing red to look white and blue to look black. The blue lens does the opposite for the blue angle of the image, causing all blue to look white and the red to look black. As one color passes through the first eye and the other through the second - the brain is tricked into perceiving each angle as a single image that has a total of three dimensions.

Are There Different Types of 3D Glasses?

As 3D technology has advanced, glasses have become more nuanced and better at tricking the brain into perceiving depth. Nowadays, there are three main types of 3D glasses.

Anaglyph 3D Glasses - The most classic form of 3D technology, these glasses typically have one red lens and one blue lens. However, they can also come in other chromatically-opposite colors like red and green. When you are thinking about old-school 3D movies, these cardboard glasses are probably what come to mind. The drawback to this type of 3D glasses is that they only filter out two colors. This may be fun for a short viewing period, but watching a full movie in only red and blue isn't very realistic or fun.

Polarized 3D Glasses - This type of 3D technology was developed to allow more colors to be perceived while also inducing the 3D experience. Instead of filtering images by color, the two separate angles are projected onto the same screen but with different light polarizations. Each eye filters out light in either a clockwise or counterclockwise circular polarization again, tricking the brain into adding 3D depth to the separate two-dimensional images. This type of glasses typically have gray lenses and since they work using light and not color, allow for a full range of hues to be perceived. If you attend a 3D movie in a modern-day theater, plastic, polarized glasses are what you will be wearing.

Shutter 3D Glasses - The future of 3D, these glasses are the most advanced type of 3D technology available today. Both Anaglyph and polarized 3D glasses use "passive 3D", while shutter 3D glasses use "active 3D" technology. Instead of filtering out images or colors, LCD screens in the glasses alternate darkening each lens creating the ultimate 3D effect. This process happens so quickly, that it's hard to notice unless you are paying close attention! The tradeoff for improved 3D quality is that these glasses rely on battery or even USB power to work. They are much heavier than manual 3D glasses options, and for now, pretty expensive too. Shutter glasses are typically sold as a premium home-viewing 3D option and haven't been adopted by the majority of viewers yet.

Are 3D Glasses Harmful to Use?

Many times when using 3D technology, you may see a warning about using 3D glasses for an extended period. Some people may develop headaches, nausea, dizziness, and eyestrain if they try to trick their brain for too long. In most cases, taking a break from using any 3D technology will cause these side effects to stop. While there isn't any concrete evidence that using 3D glasses can permanently damage your eyes, like any media viewing, taking frequent breaks and limited use may be best.

Are There Prescription 3D Glasses?

In most cases, commercial 3D glasses are large and can fit over a standard pair of prescription lenses. Some eyeglass wearers may also specifically utilize contact lenses when they want to attend a 3D movie. However, some companies manufacture pairs of prescription 3D glasses for serious 3D fans. Talk to your eye care provider about potential options if you are considering buying a prescription pair of 3D glasses.

In conclusion, 3D technology is simply a way to trick the brain into perceiving separate two-dimensional images as having three dimensions! Everyone should experience a 3D movie at least once, so If you haven't seen one yet, this is your sign to try it!