Monday, 25 April 2011

3D projectors?

Well, I was pondering what it would take to do a 3D projector. It is pretty simple if you take a "side by side" image format. You can do it all in optics.

You would need a simple lens to double the width and a pair of mirrors to overlay one half on to the other. You would have to use a non polarising technology like DLP or some such (not LCD) and add polarising filters to each side. Then simple polarised (cinema style) glasses will work without all the usual flicker you get.

But doing a search it looks horribly like projectors are going down the "shutter glasses" route. Why? It just makes more expensive active glasses that are less comfortable to use and gives horrid flicker effects. Projects *can* use polarisation which LCD TVs cannot easily do so why are they not doing this. Oh well.


  1. It's obvious - as the manufacturer would you want to sell one projector or one projector and a room full of glasses?

    TBH - the 3D revolution comes around every 15-20 years and goes away quite quickly because you get loons creating content with gratuitous 3D effects to the detriment of the story line.

  2. 3D shutter glasses are a popular option because they just need you to have a refresh rate high enough to avoid flicker despite the shutters - 240 to 300 Hz is the sort of range we're talking about, and is very manageable. Indeed, to some extent, 3D TV in the home exists because manufacturers were finding it easy to raise refresh rates to crazy values (600 and 1200Hz have been achieved in LCDs, let alone high refresh rate plasmas), and wanted to find a way to extract more money for this.

    On the other hand, special lens and polarised glasses are investment purely for the sake of 3D; this is extra cost that they wouldn't be incurring if they didn't do 3D, which misses the point of 3D TV for the manufacturers (extra money for something they'd have made anyway).

  3. Except they don't set the refresh rate high enough... there's still dis ernible flicker, and for some reason active 3d is very tiring on the eyes compared to passive.

    Of course the reason retailers pick active is they can sell the customer 6 pairs of glasses at £100 a throw (which of course only work with that model of TV so no buying cheap clones anywhere) whereas with passive the customer walks away having only paid the headline price..

    All you need for 3d projection is two projectors and a couple of polarising lenses. Then a PC to split the signal.

  4. One problem with 3D projection using polarised output from the projector is that a silver screen is needed to retain the polarisation of the projected image. A standard projector screen (or a wall) leads to loss of polarisation.
    Silver screens are more expensive and more fragile than standard screens so this could be one reason for taking the active glasses approach.