As someone who has trouble understanding and following movies without subtitles, I got into the habit of not jumping to go see new movies in the theater growing up. My local theaters’ closed captioning devices were these small, LED screens you could set in a cup holder that would provide titles, and did not lend themselves to easy viewing experiences. A few years ago, Regal Entertainment theaters began rolling out Sony holographic glasses that project captions. In addition to providing a better visual experience for viewing closed captions in movies, it puts to use some interesting physics.
|Sony Entertainment Access Glasses. Image Credit: Sony Product Details|
It’s hard to say exactly how the glasses work - it's in Sony's best interested not to disclose all the technical specs - but we can make some solid guesses. In 2008, scientists from Sony published a white paper on a full-color version of the holographic glasses that look similar to the glasses that you can pick up at the movie theater.
These glasses are heavier than an average pair of glasses, and feature a clear lens that the captions appear on. Unlike the movie screen, where images are projected, these glasses use holograms, which use interfering light beams to form an image. This particular system uses holograms and planar waveguides to keep the images clear and focused for the viewer.
The particular types of holograms (volume holograms if you want a little more detail) they used allowed them to cut down on images ghosting for the wearer. The image below shows a basic example of what the ghosting might look like - images might show up on top of each other; appear as a second, lighter image off to the side; or become distorted.
|An example of what image ghosting might look like in a projection. |
You can read the text, but there is a lot of visual interference from other images.
After the hologram receives the light and converts it into a useable signal, the waveguide directs (or 'guides') the light in a single direction. The glasses use planar waveguides, which are usually made of three layers - the light comes in (the acceptance cone in the image below) and two outside layers (labeled 'cladding' below) with a different refractive index than the inside layer (labeled 'core' below). The image is for an optical fiber, but it shows the general idea of the waveguide they use in the glasses.
|Propagation of light through an optical fiber. Image Credit: WikiCommons|
The light is directed into the middle layer, allowing it to be reflected back and forth in a zig-zag pattern to a second volume hologram that converts the signal back into light for your eyes to see. When Regal started putting the glasses in their theaters, they released a video that can show you the glasses in action.
I normally wear my contacts with these glasses (they're designed so that you can use them over glasses if you need to), but the end experience is very similar to viewing open captions at a movie. It's a cool technology that made a huge difference for me personally in going to see movies, but there's also something futuristic about being able to use holograms for something as mundane as going to the movies.