Light23 wrote:The more I think about the 3D version of my laser monitor, the more I am convinced of a better way to do 3D than polarization. Since the lasers use VERY narrow wavelengths I could use bandpass filters for glasses.
Each of the Bandpass filters pass 3 narrow band of spectrum as illustrated in the following figure.
This bandpass filter system can provide good separation of the right and left images as seen by the viewer’s right and left eyes, and thus low 3D crosstalk/ghosting, no light loss with this filter system make it VERY practical for use with my 2 laser video projectors outfitted with the appropriate wavelength lasers for each projector.
The advantage of this system over the use of polarization as the basis for a passive 3D system is this system is brighter and can be used with my unconventional projection screens instead of requiring the use of a silver screen.
The system you're describing is basically 6P 3D, ala Dolby 3D. It's indeed much more efficient than dual-projector passive 3D polarization which loses 50% of the light, twice, once at the projector end and once at the viewer through their glasses, for an overall lumen efficiency of 25%. Dolby has achieved about 43% lumen efficiency with their 6P system, which is the best achieved so far. The max theoretical efficiency is 50%, regardless of the technique used. Intuitively, when you wear the polarizing glasses, you lose 50% of the light, namely the light meant for only one eye, not both.
However with direct laser projection you could easily just rotate one set of lasers by 90% and thereby cut down your loss of light to the bare minimum theoretically possible, which is 50%, by removing the need to use a polarizing filter at each projector. Lasers are already linearly polarized.
Of course to eliminate cross-talk you'd still want a single polarizing lens at each projector just to make 100% sure that 100% of the light coming out is aligned properly, but that would only lose a couple % of lumens.
The big problem with polarized 3D projection is because your screen needs to preserve polarization, which means it has to be silver or metallic which has its own issues (hotspotting, and speckle would be worse, plus the cost). I'm not even sure it's possible to do passive polarized 3D with rear-projection anyway, I'd be curious how the polarization could be maintained when light is travelling through a screen. Pretty sure it's impossible, so 6P is indeed a much better way to do it if you're going rear-projection.
But direct laser projection is only going to remain a very low lumen device, due to FCC regulations which are your enemy (but your eyes' friends). No commercial company is going to sell high lumen direct laser beam projectors, it would literally burn people's retinas if they walked by the image and sat on the couch. Rear projection might be one way to get around the dangers of direct laser projection, but good luck trying to convince a government regulator to approve your product unless you've run safety tests.
Projectors like this are totally different in practice from laser-illuminated projectors, which simply replace the xenon or LEDs with lasers (usually two blue lasers, with one for blue color and the other for yellow pumped phosphor to create green and red) and hit the DMD or Lcos chips with a purer / cleaner white instead. (instead of it being broadspectrum).
It's a very exciting and innovative project and I wish you all the best. 6P should reduce speckle and metamerism (eg :is the dress blue or is it gold? debate)
But those micromirror patents that the Picopro / Sony use are not likely to get licensed that cheaply, certainly not enough to undercut their own products, and these projectors have some fundamental issues like the fact that laser regulations are there for a reason, to protect people going being blinded.
That's why you see 5mw lasers in these pocket projectors, otherwise Sony would get sued to smithereens the second some kid blinded himself by staring into it. The regulations exist for a reason, to protect people from accidental exposure. Laser-illuminated projectors have their light spread out and de-speckled and don't directly project towards the user. In commercial cinemas they have to guarantee that the light cannot cross someone's face as they sit down in their seats, so they get a pass for that reason. The home market is something else entirely. There is a consortium out there trying to get more sane laser regulations implemented but the FCC are conservative bunch, as they should be (because people's safety matters more than short-term corporate profits. Blindness is possibly permanent and not a fun thing to have, one would imagine). Lawsuits and damages could be in the millions. Financial backers would be aware of this. One of the first things a lawyer would ask is : "what's the chance of someone damaging their vision from this?". You could say zero but they would likely need independently verified scientific proof, to limit liability exposure.
