Understanding DLP link standard & using DLP link Glasses to sync single image with multiple projectors

Hi Stewart,

You can find basic details on DLP Link operation in this link http://www.dlp.com/projector/dlp-innovations/dlp-link.aspx

Regards,

Sanjeev

Hi sanjeev - yes I had found this page allready, unfortunately it doesn't answer my question.

I need to know the DLP link standard & understand timing of the pulses, tolerance of the system/glasses, blanking period, does the DLP link signal just trigger the switch or does it contain L/R data?

Hi Steward,

In your question by "L/R data" are you using the term for  "video data". If so then, the answer is "NO". The DLP Link signal doesn't contatin information regarding the video data. DLP Link signal is just a trigger signal to actuate DLP Link enabled glasses, the DLP Link enabled glasses can uses 'active shutter glasses' principle, these glasses become either transparent (Open) or Opaque (Close). At any given point of time one will be open and the other closed.

The DLP Link signal output from the projector is decoded by DLP Link enabled glasses and use this information to Open or Close 'active shutter' glasses. When the DMD is loading "left eye" data the DLP Link signal sent from the projector will indicate DLP Link enabled glasses to 'open' left eye and 'close' right eye shutter glass and vice versa.

Regards,

Sanjeev

Thanks Sanjeev

Is there a standard for timing, pulse widths, light intensity etc?

Do you know how projector manufacturers enable the function to swap eyes, when in active stereo mode so that the stereo image is presented correctly? Do they miss a DLP link pulse or add another DLP link pulse between left & right frames? 

Stewart

Hi Stewart,

The timing information is not publicly available.

Projector manufacturers don't have direct control on the timing parameters. There is no chance of missing DLP Link pulses between the left & right frames as DMD puts these signals. It is possible that due to external light conditions the DLP Link glasses not able to read the signals properly then loose the synchronization.

I suggest you to talk to the projector manufacturer directly and explain the situation on when (like light conditions, angle, distance from projector etc.) you start seeing flickering effect. Mention the projector model and DLP Link glass details.   

Regards,

Sanjeev

Did you get any success with this?

I am trying to do a similar thing. 

Hi Ben,

Can you please be more specific on this? Are you planning to desing DLP Link glasses or you are interested to use DLP Link information for synchronisation between the different projectors?

Regards,

Sanjeev

We are trying to synchronize multiple projectors that are using DLP Link.

We use AMD's Eyefinity to create a quad buffered 120Hz output that seems to make the projectors VGA vsync with each other and then by inverting some projectors we make sure the left and right eye DLP link tokens are all the same. After this sometimes the system works but others times the glasses get confused and we get rainbow colours after a few seconds etc...  The more projectors the worst it gets. We want to use six.

We are starting to think we need to ditch DLP Link and use RF glasses unless we can come up with a solution.

Would there be a way to make the projector work normal but just disable the DLP link signals. We could then do this on five of the projectors and the glasses would only see the signals from one projector. We dont mind opening up the units and doing some tinkering if there's a chip or connection that would control this. Or maybe covering up part of the colour wheel? We really dont know much about it.

Thanks

Ben

Hi Ben,

DLP Link intended to work with one projector at a time. In DLP Link technique the projector basically insert light pulses to indicate whether it is a right or left frame. When you run multiple DLP enabled projectors it will create problem for the glasses to sync unless all the inserted light pulses very much aligned.  Have you ensured the all the VYSNC going to the projectors is aligned perfectly?

One more thing, when you mentioned it works sometime, it could be because you are not moving and standing at a fixed position, you can experiment if it allways failing when you move your head to look at different projectors.

It would be interesting to see whether DLP Link locks if you disable DLP Link in all projectors except  one. Before disabling DLP Link you can call projector manufacturer to see if it allows highspeed mode i.e., 120Hz input to 120Hz output.

Regards,

Sanjeev

I'm pretty sure if I disable 3D sync on the projector it doesnt do 120Hz (shows either L or R frame) so I guess doesnt support highspeed mode.

Will try and contact the manufacturer but I dont like my chances. Any other ways to disable DLP Link on the electronics side?

Hi Ben,

Unfortunately there is NONE on the electronics side.

The DLP Link enable and disable is realized by projector firmware functionality based on the user selection in the UI it will reconfigure the DLP processor. So it is not possible to avoid remove DLP Link byremoving/modifying elctronic component in the projector. Check with your projector manufacturer if they can allow 120Hz passthrough mode.

Regards,

Sanjeev

Stewart, 

I am currently tasked at my research lab to construct a 6-sided, fully-immersive, VR environment. I have come into the task after some other people have worked on it. I currently possess six Benq DLP projectors. The projectors have frame sequential and (I believe) top-bottom 3D projection modes. The screens for the walls already exist and I don't think they are compatible with passive 3D techniques using polarization. I can get all six projectors synced on an image/environment from the computer side. My issue is that I don't know if it is possible to sync the projectors together so that the active glasses don't have to adjust when looking between different screens.

I was mainly wondering if you or anyone figured out how to get multiple projectors, operating with DLP-Link, synchronized.

-Jake

Unfortunately we discovered it wasnt possible. Those cheap BenQ projectors arnt made for what you are trying to do. You need to buy the more expensive projectors with polarized light and paint your room in a special silver paint. Then you can use passive glasses and you wont have any sync issues.

Ben,

I was pretty confident that the projectors I have would not be able to all be synced together. Using a passive setup would be feasible but my concern is that we are using a rear projection setup and I'm not sure how the polarized light would interact with our screen material. That is something I can look into. Another option I have considered is putting two projectors per screen and manually forcing, via LCD shutter screens, the stereoscopic 3D. If I could control when all of the screens are shuttering then I could use that signal to drive some type of RF or IR active glasses. What are your thoughts about that approach?

Also, thank you for your reply.

-Jake

Both those ideas should work. As a last resort you could always do red/blue glasses :-)

Hello

Hm.I am probably    silly  now but maybe 2  things  could  help you out.

1.synchronise  starts  of all projectors  by adding one common  triger in theris softwere

2.put all projectors in posicions  that  would  not  allowed  to  lose any   signal by  glasses

regards