by Lluis Milà, Panasonic Connect Europe
Mention 3D and many of us will immediately think of the pioneering 3D movies that we first saw in the cinema. For the older reader, it might be the shark in Jaws jumping out of the screen to shock the audience. For those who are younger, it might be their first view of an incredible 3D world in the movie Avatar.
Sitting down in the darkened cinema and putting on those strange red and green lensed glasses for the first time sticks in the memory. And I bet we all wondered, just how does this work?
It’s all about depth perception
Stereopsis, more commonly known as 3D depth perception, occurs when the brain combines the two images received from each eye and creates one single 3D image. This allows us to easily engage and interact with the world around us.
Around five per cent of the population is thought to suffer from stereo blindness, meaning they are unable to see in 3D. A fun way to test your vision is to take a look at these Magic Eye pictures, otherwise known as Autostereograms. They are effectively, a picture within a picture. Focus your eyes behind the 2D pattern. As you start to look at the pattern from a slightly different angle the brain constructs the 3D image.
Can you see the spider and two dinosaurs in 3D in these images? Stare in the middle of the image. Then cross your eyes until a third shape appears between them. Then relax your eye focus until the 3D image appears.
Not new but evolving
We may still think of 3D as being a relatively recent invention. However, simple systems have been around for many years. Two types of 3D projector technology dominate the market today: active and passive 3D Technology.
Active 3D projection is based on the use of active shutter alternate frame sequencing and battery-powered (active) glasses with transparent LCD panels in front of each eye. The biggest recent improvements in this technology have been the ability to deliver higher frame rates. These range from 60 frames to 120 frames per eye and provide a much more seamless effect with better separation.
Only a single projector is required to create a 3D effect and any projection surface can be used. It’s also a very scalable solution as multiple projectors can be synchronised together. However, active systems are mainly used in specialist areas such as medical training, where they provide a high-quality image.
Only specific projector models can decode and synchronise active shutter 3D systems. The glasses are expensive and also require a wireless data link active at all times. This makes them challenging to use in Location Based Entertainment (LBE) environments.
Types of dominant passive 3D projection
There are two types of dominant passive 3D projection: anaglyph and pure passive – polarised.
In the LBE industry, anaglyph has seen the biggest improvements in passive 3D technology because of innovations from German technology company Infitec. Just like the early 3D movies, the system uses different wavelengths of light to encode the left and right eye images. Both images are superimposed and shown simultaneously. Any display device or single projector can display anaglyph content.
Historically, the main downside of anaglyph encoding is the loss of colour accuracy, and in early systems colour saturation as well. However, the most advanced Infitec anaglyph system uses two projectors with notch filters for each primary colour to reproduce a full-colour image per eye. This means that the viewer’s brain sees the image in a much more natural colour giving a very life-like experience.
Specific filters need to be added to the projector to use Infitec glasses but specialist manufacturers like Panasonic offer laser projector models with the filters already included. External filters can also be bought as accessories for Panasonic lamp projectors.
A pure passive 3D system uses polarisation to restrict the light that reaches each eye to create the 3D effect. Two projectors, with appropriate filters, project two matching images superimposed on top of each other onto a special polarisation-preserving screen surface. This reflective surface looks silver, hence the old movie theatre term “the silver screen.” The standard passive glasses then capture each colour in a separate eye – creating the 3D effect.
The use of two projectors can make this system more expensive but two projected images also doubles the brightness of the image providing higher quality. A method to separate the left and right to each projector is also required.
Careful selection is key
All 3D systems have their advantages and compromises. It is important to carefully consider the individual requirements and use of the system before purchase.
For more information, download Putting 3D into Perspective, the Panasonic 3D Tech Guide for Location Based Entertainment.
