3D Ready Projectors and 3D Projection

Most people are familiar with the concept of 3D movies and projection as it has come in and out of fashion several times over the years.
Up to now 3D was available mainly in cinemas but projector manufacturers are now releasing 3D ready projectors, bringing 3D to the classroom, office and home.

• How does 3D work?
• What are the different types of 3D technologies?
  • Anaglyph 3D
  • Active Shutter 3D
  • Polarised 3D
  • Interference Filter Technology 3D
• Is 3D here to stay?

To see a list of 3D Ready projectors with prices and specifications, click here

How does 3D work?

Basically 3D uses two overlapping images to give an impression of depth. One image is for the left eye and the other is for the right eye.
Using special glasses, each eye sees a slightly different image increasing the sense of depth and making it look like the image extends into the background and towards the viewer.

There are different ways of creating the two images and different types of glasses used to show the different images to each eye.
We will explain here the different technologies used in projection.

What are the different types of 3D technologies?

Anaglyph 3D

Anaglyph 3D is probably the technology most people think about when they think about 3D images and movies. In fact if you have seen a 3D movie on DVD in the past, it most likely was using the anaglyph method.

The anaglyph images are made up of two superimposed and offset colour layers. When viewed with two colour glasses (usually with one red lens and one cyan lens), the image appears to have some depth.

Anaglyph image

Advantages of anaglyph 3D

• The main advantage of anaglyph 3D is that it's inexpensive and accessible to most people.
  You don't need a new 3D ready projector or television as any equipment capable of showing a video will be able to show an anaglyph 3D video.
  Also because the technology is passive (no electronic components are needed in the glasses), the glasses are cheap to produce and usually are included with 3D movie DVDs.

Disadvantages of anaglyph 3D

• Having two coloured lenses causes a loss of brightness. Because some of the light is blocked by the colour filter, so the image may appear dimmer than the equivalent standard 2D movie.
• The colours can appear a bit off since one lens will give a red tint to the whole image while the other gives a blue tint.

Active Shutter 3D

Active shutter 3D is a technology where the display or projector shows alternating 'left eye' then 'right eye' images at very high speed (up to 120 frames per second).

The active shutter glasses are made of glass containing liquid crystal and a polarising filter. The glass becomes dark when some voltage is applied.
Using this property, the glasses alternately darken each lens, effectively blocking the view of one eye then the other. The glasses receive the timing signal from the display using DLP link, Bluetooth, Infra Red or Radio frequency, so they can synchronise with the display's alternating rate.

Because this process is extremely quick we can't distinguish the alternating images as our brain combines them into one image that appears in 3D.

DLP-Link Active Shutter Glasses

Active shutter 3D is the technology found in the new DLP 3D ready projectors released by Optoma, Viewsonic, BenQ, Mitsubishi etc.

Advantages of active shutter 3D

• Problems with 'ghosting' (where we see two different images at the same time) are more or less eliminated since the glasses block the view to the eye not being used.

Disadvantages of active shutter 3D

• Unless the display and glasses are working at very high speed such as 120Hz, some flicker may be seen. This is because each eye only sees half of the frames and a low refresh rate can cause a sort of stop motion effect.
• As the glasses block half of the light at any given moment, the perceived brightness will be reduced by at least 50%. Some glasses also are slightly darker which will reduce the brightness even more.
  It will however improve the perceived contrast as dark levels will be reduced.

Polarised 3D

Polarised 3D is used in cinemas and high end applications.
The polarised method uses polarising filters on the projector(s) that make the light waves oscillate in the same direction while filters on the glasses only allow the light meant for each eye to pass through the lens.
Each eye sees a different image creating a 3D effect and perception of depth.

There are two different systems used in commercial 3D. One uses two projectors with a polarising filter each (e.g. IMAX 3D) and the other uses one projector with one fast switching polarising filter (e.g. RealD). There are also two different types of polarisation: linear (left and right polarisation) as used in IMAX 3D and circular (clockwise and counter clockwise) as used in RealD. The main difference is that unlike the older linear polarisation systems, the circular polarisation systems allow viewers to tilt and move their heads naturally without a loss of 3D perception.

Advantages of polarised 3D

• Problems with 'ghosting' (where we see two different images at the same time) are more or less eliminated since the image for the right eye cannot be seen by the left eye and vice versa.
• Like anaglyph 3D, polarised glasses are passive which means they are relatively cheap to produce making them a good choice for commercial cinemas. They also have plastic frames which makes them more durable than the paper made anaglyph frames, and they can be re-used over and over.

Disadvantages of polarised 3D

• Single projector systems (e.g. RealD) suffer from a brightness loss as each eye only sees half of the light reflected from the screen. Like active shutter 3D, this results in a 50% loss (at least) of perceived brightness. This is not a problem with two projector systems as each eye benefit from the full brightness of the projector.
• Polarised 3D requires the use of expensive projectors and other equipment making the system itself quite expensive. It also requires the use a silver screen that maintains polarisation as standard white screens cause depolarisation voiding the effect.

Interference Filter Technology 3D

Interference filter technology 3D is another technology used in cinemas. Made by the German company Infitec, it is licensed by Dolby and is also known as Dolby 3D in cinemas.

The interference filter method uses a colour filter wheel between the lamp and the imaging device in the projector. While the human eye can see a light spectrum composed of the basic colours red, green and blue, the filter wheel will divide each colour in different wavelengths. One wavelength for red can only be seen by the left eye and another wavelength for red can only be seen by the right eye. The same applies for blue and green.
The glasses then have filters allowing different red, green and blue wavelength for each eye. Additional filters also correct colour perception so what you see if as close to the original as possible.

Advantages of interference filter 3D

• There is no need for a silver screen as with polarised systems.
• Like anaglyph 3D and polarised 3D, the glasses are passive. They are however harder to make than polarised glasses so they are built to last with stronger frames and more resitant lenses.

Disadvantages of interference filter 3D

• The system, like others, suffers from a loss of brightness compared to a 2D movie on the same projector.
• Other than the cost of buying new equipment (either a new projector, or modifying the existing projector), the cost of the glasses is higher than for polarised glasses despite being passive glasses. Some cinemas may be put off by the cost, and others go to great length to ensure that the glasses aren't taken away by movie viewers.

Is 3D here to stay?

3D has been around for a long time: invented in 1890 it only became more mainstream in the 1950s before falling out of fashion again until the 80s. After another spell of lower popularity, 3D is now making its comeback. The question is it here to stay?

Projector manufacturers certainly seem to see it as the next thing in non commercial projection.
However many people think it has come too soon after HD technology and they are not prepared to 'upgrade' their equipment again so soon. Others aren't convinced about having to wear unflatering glasses to watch TV or movies, even at home.

So is 3D here to stay? It could be but there's also a chance it will fade away as it has in the past. We will have to wait and see.

Sources: projectorcentral.com, Wikipedia