Dual micro projector shutter glasses setup.

[Okta]

With micro lcd projectors on arriving on the market they create another option for compact s3d setups so here is an idea we were throwing around in another thread.



Its about time I put an explanation of what is going on in this drawing. Using 2 lcd projectors (with small lenses) and place a set of shutter glasses over the lenses to alternatly block the outputs while another set worn by the viewer synched to the first set acts as normal shutters. Its simply turning 2 passive projectors into a single active.

This is an alternative to using a polarized filter setup and may have less ghosting?





ps. link fixed thanks crim3

Update- its been tried before , of course great minds think alike http://www.uni-weimar.de/cms/fileadmin/ ... 004ipt.pdf" onclick="window.open(this.href);return false;

[Tril]

Can they give good brightness at such a small size? Probably not on a very big screen.

[Okta]

I think you need a pretty dark room for them by the look of this picture here-

http://cgi.ebay.com.au/Pocket-Led-Micro ... 18Q2el1247

[Tril]

20 lumens! That's low. That means you need to keep the screen size very small.

[Likay]

Lol! I had no idea such projectors existed but here's some math:
To have a decent experience with light you need 700-1000 ansilumen/squaremeter. Since shutterglasses are polarized you probably will have a light throughput of max 45% through those wich gives appr 9 lumens/eye left. With these projectors you will have a ridiculously small screen: appr 0,1x0,13 meters @ 700lm/sqm.....
I could say you can increase the size to the double if you're not too eager to see everything bright. Keeping the room coaldark will of course help.
I know it says Projective Size: 0.6m ~ 2.0m 15" ~ 50" in the specs but that cannot be possible without lightamplifier behind the watchers shutterglasses.

On the other hand: If you use e-dimensional shutterglasses which easily can be controlled by externally electronics you can simply use an oscillator to control both shutters. If the shutters handle 500Hz you can choose that without problems for flickerfree reproduction.

One other advantage with these kind of solutions: The only thing you need for compability is a graphiccard with dual outputs which all present stereodrivers supports. You will not depend on just shutterglass support from stereodrivers. I can only speak for e-d glasses here since i don't know if other shutters can be controlled without disassembling them.

cheers

[Welder]

I think I read that the max size you can get with mini projectors was just 15 inches wide. Don't quote me, But I did read that, may be a different one though.

[nubie]

I am very confused here, if you have 2 projectors why do you need shutterglasses?

Shutterglasses = 2 polarizers per eye (one each side of the LCD, integral to all LCD technology) No silver screen needed.

Polarized projection = 2 polarizers per eye (one on the projector and one in the passive glasses) + Silver screen.

Single DLP Shutterglasses = cheaper, brighter, higher resolution no Silver screen needed. (do some DLP Projectors offer a shutter port?)



It looks like the only benefit is that you don't need a silver screen, but buy 2-4 pairs of shutters and you could just get the silver screen for the money you spent. If going shutters a DLP with shutter support would make more sense.

I don't understand the drawing, I don't think it would work, the shutterglasses and the projectors would all need to be synchronised, so 4 things in sync (PJ1+PJ2+Left Eye+Right Eye) instead of only 3 (PJ+Left+Right.)

When the Laser DLP come out they should have enough brightness. But you should still use regular DLP Checkerboard shutter with them.

[nubie]

Uh-oh, I think I just figured out the drawing (a short explanation would be nice, or a link to "other thread").

You basically traded 2 polarizing layers for 4!!! Shutter glasses have 2 polarizing layers, so sending them through 4 layers isn't going to decrease ghosting.

Passive polars are going to have better contrast than active at every price point (IE $10 polars are better than $10 glasses, $20 polars are better than $20 glasses, etc. There are some $400+ Shutters that are for projection use, but ouch!).

When I came on the scene ~10 years ago they were called "LCD Shutterglasses", and LCD tech is made from 2 polars and some movable gel/liquid that you can excite electrically.

Your idea is interesting to take software out of the equation (as long as it can offer each eye on a single output). Unfortunately it isn't better than dual passive polarized (it is more like quad active polarized), and costs more to implement.

The only dubious advantage this has it working on surfaces that don't preserve polarization, and since standard shutter projection offers that as well there isn't a benefit.

It was pretty close to working though . It could be made to work with a rotating wheel that shuttered the light mechanically, but it would be a hack (I love hacks, I have hackaday as my homepage , but when researching methods of display for S3D this one doesn't have much more than curiosity value, as a fun thing to do if you have all the parts to play with.)

[Likay]

If you set the shutterfrequency at 500 Hz or even more i don't think you would have any sync problems. Just set the frequency as high as possible where the shutters works well. And yes: You have to be careful that eventual polarization of the projectors (lcd's) is not interfering with the polarization of the shutterglasses. Upgrading the projectors may cause glasses burnout (because of a lot of radiant energy). Don't know how big the risk is but i managed to fry a pair of camerapolarizers with my 2000lm projectors. Therefore i once in another thread suggested using lcd-based welderglasses. You definitely have to make some hardware changes to make a proper function of those though. There might be an issue with high light energy problems with those too since the beam is concentraded. Think they manage more that shutterglasses if they turn in.
Agree with Nubie with comparing to a passive setup. This is hardly cost effective but would make a nice experiment. In a very small scale it might even pay off. You can try beaming on the backside of a paper (and mirroring images on projectors) and then having a S-3D tv.
One of the biggest plusses with a passive rig is that everybody can watch at a time. Only a pair of polarized glasses/person is needed. Of course that's is rule for shutterrigs too but there everybody need to have shutterglasses....
Still don't know where people have the idea that a passive rig ghosts? f it comes from an IMAX cinema their screen is hollowed in a sort of beecake pattern probably to let sound through(thanks Jahun), and i can't imagine that would help.
I can see ghosting at home if i have two different images on each projector (one extremely dark and the other extremely light and both images having big contrasts) but i can't see any ghosting when gaming or watching movies.

[nubie]

Still don't know where people have the idea that a passive rig ghosts? f it comes from an IMAX cinema their screen is hollowed in a sort of beecake pattern probably to let sound through(thanks Jahun), and i can't imagine that would help.

I can see ghosting at home if i have two different images on each projector (one extremely dark and the other extremely light and both images having big contrasts) but i can't see any ghosting when gaming or watching movies.

I just saw my first passive projection Imax movie, unfortunately from an aisle seat , there was some extreme ghosting in about 2 spots, and minimal ghosting in other places, but the subject matter was the space shuttle, so you would expect extreme brightness differences.

My home polarizing projectors were pretty good actually, better on the one I stripped the anti-glare coating from .

The irony is that people go "ooh shutterglasses don't ghost", when the technology is identical, with the same number of polarizing layers. The only difference is the screen, it should preserve the polarization properly. I may be a little to curious for my own good though, I take apart everything and read a lot about how things work (I was 6 or 7 when I went through our encyclopedias learning about helicopters for example.)

[Likay]

Maybe it depends. In my experience it's the silverscreen that causes ghosting (if you're not having too bad glasses and/or filters). Can't imagine they use a giant silverscreen material in an imax cinema because just a small wind will make it flutter. So i think you get better materials if you get it for homestudios. Just a thought but cannot really tell before i cut out a sample from an imax screen and compare it with my own.

[LukePC1]

wasn't there someone who wanted to create a HMD of it?

I think the SG solution might be good to transport the 'projector rig' and project everywhere

[Likay]

wasn't there someone who wanted to create a HMD of it?

I think the SG solution might be good to transport the 'projector rig' and project everywhere

Good memory It's staticbuddha's project: HERE

And the shuttersolution would work excellently here i think. Unless you have too much interference with ev projectorpolarization. It's easily handled by using carefully aligned cheap retarders though.

[nubie]

Maybe it depends. In my experience it's the silverscreen that causes ghosting (if you're not having too bad glasses and/or filters). Can't imagine they use a giant silverscreen material in an imax cinema because just a small wind will make it flutter. So i think you get better materials if you get it for homestudios. Just a thought but cannot really tell before i cut out a sample from an imax screen and compare it with my own.

I used the plain Da-Lite silverscreen (it was a new screen, shipped direct-from-factory).

I don't see why they can't use a good polarization material, iMax is made for 3D movies. And they call it the "silver screen" for a reason .

I don't think that a small wind will make it flutter, it can be mounted permanently just fine, it is a screen material just like any other: http://www.dalite.com/products/selecting.php . They might use the 3D Grey at the bottom of the front-projection section, it looks like 1.3 gain and 99% polarization preserving.

[chrisdfw]

You can't just let shutter glasses do their thing at whatever high frequency you want to. The projectors are still updating the screen 60 times per second and if your left eye is looking at the screen during the time the projector has only had time to update 5% of the screen then that is all you will see.

The shutters have to be synched to the video card that is drawing the screen or your eye won't see a complete frame.

You can see an example of what will happen if you aim a video camera at a TV screen and video tape a show. You will get banding across the video where the camera didn't catch the complete frame.

[Tril]

It depends on the technology used by the projector. It should be fine with LCD projectors because the pixels are lighted all the time. It can cause problems with CRT projectors or DLP projectors.

[LukePC1]

but wouldn't it work if the picture was fast enough? I mean the human eye works differently (slower and faster) than cameras. They compensate for many things, so I think it wouldn't be that bad if these projectores were LCD based. However if they were DLP style the eye would miss some lines, which are only projected realy short!

about the frequency: I'd choose something different than the output frequencey*n (n=natural number like 1,2,3,4), so you get always a different image and not always half the image from left and half the image from the right...

And I think a HIGH frequency could help, too. However I'm not convinced, if all this is even necessary

[Okta]

It depends on the technology used by the projector. It should be fine with LCD projectors because the pixels are lighted all the time. It can cause problems with CRT projectors or DLP projectors.

This seems to be the case i just did an experiment with my phone camera and the lcd screen was fine but the crt tv showed some brighter horizontal bars shifting around.

[Okta]

You can't just let shutter glasses do their thing at whatever high frequency you want to. The projectors are still updating the screen 60 times per second and if your left eye is looking at the screen during the time the projector has only had time to update 5% of the screen then that is all you will see.

The shutters have to be synched to the video card that is drawing the screen or your eye won't see a complete frame.

You can see an example of what will happen if you aim a video camera at a TV screen and video tape a show. You will get banding across the video where the camera didn't catch the complete frame.

If your eye normaly doesnt have a problem with the update of an lcd i dont think it will matter when shuttered.

[smoothy]

are you guys still working on this project?

I would love to see the results, please share?

[bastian74]

Put a flashlight through one polarized lens and look through another towards the flashlight. How much light does it block? Notice that near perpendicular it's pretty sensitive, so you have to keep your head perfectly level.

Also, how well does your screen do at preserving the ploarization without scattering.
The quality of the polarizing lenses comes in to play too. They're not all created equal.

At least for the projector, I'd buy decent polarized lenses for a 35mm camera. I would not use the ones torn out of a 2nd set of free glasses. And if you're using circular polarizers ensure the circular plane is facing the projector / your eyeballs. Circular polarizers filter the light with a polarizer and then scramble it again so it's unpolarized. They do that because camera autofocus sensers require two polarized planes to focus.

Two circular polarizers are fascinating to play with, especially when you look at a LCD screen through two of them. Hold one up to your eye and black out the entire LCD screen. Then hold another one between the screen and it allows you to see the screen only through the polarizer. It's a very unusual sight to see. You're used to a small disc creating a sillouette not creating a portal in the blackness that you can see through. You have to have at least one circular polarizer and they have to be facing the right way.

[Okta]

I have added an explanation is the OP. It uses 2 active glasses, not passive lenses so no special screen required.
Also i have just been made aware my idea has been tried before http://www.uni-weimar.de/cms/fileadmin/ ... 004ipt.pdf" onclick="window.open(this.href);return false;

[iondrive]

here's how I would do it using one projector:

get a DLP projector running properly in shutterglass mode. I have this already and am happy at 60 Hz.

use a 45 degree angled half-silvered mirror to deflect half the beam sideways onto a first-surface mirror that directs that beam onto your screen. Put your shutterglass lenses over the beams and make sure the outputs have opposite polarizations. The video is in sync with the lenses so it should work. I did a little test with this and wasn't happy with the light that got through my LCD glass and I was happy with my shutterglass setup already so I didn't go any further. Still, I just wanted to share this idea with you all. I suppose the reason to do this would be if you had an audience and not enough shutterglasses but did have enough polarized glasses. The view would still flicker as each eye gets 30 FPS but if it's dark, then I think it's fine. It's fine for me. You need a silver screen of course but I still think it's a slick idea to save the cost of a second projector.

[Okta]

Heh thats pretty clever So you turned an active setup into a passively viewd setup? Cool.