Wednesday, December 17, 2008

New Projector! & Designs for a new LLP "Coffee" Table

** As an update to this post, I have since changed my table to a DSI table and sold the projector for $600, and bought a better one.**

Well, I finished up this school quarter finally and have been working on a bunch of flash/as3 stuff, tooling around with different ideas and projects. I messed around with the Youtube API a bit and have turned my attention back to building a cool 3D menu, now using Papervision3D and the Tweener add-in.

I received some lasers from Aixiz for another project, but they are too weak, so new ones will be ordered in the coming weeks. While playing with the lasers, I came to appriciate the easy setup of a multitouch LLP (Laser Light Plane) table, and have decided to make my next table a LLP one.

I randomly popped onto for projectors this week and the first most recent post was about an Optoma EP7155 projector for $200!!! I assumed something was wrong with it, but called anyways. The guy said nothing was wrong with it, so I drove out there to have a look, not expecting much. I was first surprised at how small the thing was and it all looked good so I swapped for cash and took it home to play with it.

The OPTOMA EP7155 is known as a ultraportable "laptop" projector, hence why it is so small:

It has a bunch of useful ports on the back and should work really well for my new table. It's native resolution is 1024x768, but can do up to 1600x1200. I will be running it at 1280x768, as that is the resolution of my 720p HD projector in my living room. The table will also act as a controller for the HD one, along with displaying it's own image. Only thing is that it is quite loud, at about 35db or so since the fan must be on high to cool it off since it gets hot. Thus I will have to make sure there is good ventilation and to enclose it in such a way as to reduce noise.

A rough diagram of my new table:

And the placement of the mirrors to achieve the shallow 2 foot depth using this website:

I picked up some mirror tiles at Home Depot for cheap and played around with angling the image, but I will need bigger mirrors for my final table

So looks like this will be a smooth topped table probably using a single layer of frosted glass or with a piece of vellum underneath as the projection surface. The lasers will be around the corners. I will test with 2 lasers first and decide if I need 4 or not.


  1. I am also planning a low MT table. I could get a short trough projector (benq 512st) at a reasonable price. The problem is the camera with that wide angle lens. What are you planning to do? Keep going with this great work.


  2. The best way to do it is to put the camera in a way that it uses the mirrors to get a bigger viewing angle. For my above setup, I'll probably only need to put my PS3 Eye cam in such a way that it uses the last mirror that the projected image bounces off of.

  3. Nice find!

    Keep in mind if you want a good image, you'll need First Surface mirrors as normal mirrors will cause ghosting.

  4. Be aware that if you have a projector that can natively display 1024x768 pixels and you change the resolution to 1280x800, you will in fact get a very bad image for two reasons:

    First, the projectors hardware determines the maximum resolution. If the image chip only has 1024x768 pixels and you want it to display 1280x800, where should the additional pixels come from? In fact, the projectors software will accept the bigger image from your computers output and internally down-size it to the 1024x768 pixels it can display. So your image will become blurry, and elements like buttons, type, etc. will appear ~15% smaller.

    And subsequently because the image chip has a 4:3 ratio but you want to display a almost 16:9 ratio, your hardware pixels won't even be used all! This is due to the fact that when the projector tries to fit the 1280 pixels width to your 1024 available pixels, the 800 pixels height will not even use your total available 768 hardware pixels but only ~600 of them.

    In the end you think you get a high-res picture but in fact loose image quality two times! You paid for a projector with a 1024x768 chip so the best you will get is a 1024x768 projected image.
    Good luck with your ambitious project!

  5. I am fully aware of everything you said Mr. Anonymous. The only reason I am planning on running my projector at 1280x720 is because it is going to be a mirrored image from the one on my HD projector overhead. I am not looking for an amazing picture out of the table design as it mainly will run flash animation based software, and not for watching HD content. Thanks for the advise though.

  6. I really like the idear of a MT coffee table, however are there nice applications out there to have a good use for this table as a coffee table? I mean applications that for example recognize putting a cup of coffee on the surface and then display information about coffee or show rss feeds of your favorite websites on the table. That would be awesome, however you will unfortunately need a DI setup to recognize cups :-(

  7. When making any other table design other than a DI table, you have to have the fidicial itself light up, with an internal IR LED in order for the fidicial patterns to work. Other methods of getting objects to recognize are using RFID tags or bluetooth. As for apps specifically for a "coffee" table environment, the current released apps would be cool, but I am constantly making new projects so drop me an email or hit me up on the nuigroup forums to suggest something.

  8. hi... i was still searching the tutor of study material of AScripts... will you please send me the link of that web from where u r studying the AS3 and ur multitouch is awesome but i've a sujjestion to u u r using IR their is an another option to make ur LCD sensible. You can also use Organic semiconductors to make an surface sensible then after that their is no need of photo diodes and web cams for IR. Try this and plz mail me that link from where u r studying AS3.
    my e-mail address is

    -- Aatur Harsh (India(Rajasthan)).

  9. What size were the lasers you determined to be underpowered and what did you end up going with. I am considering (4) 780nm 25mw for a 4' x 8' touch wall.

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  11. The table actually got changed to a DSI table as I needed to make sure that glasses and plates and such placed on the table didnt direct the laser light into anyone's eyes. If I was still going with the setup, I would be going with probably (2) 25mW 780nm IR lasers from Aixiz, placed in two opposite corners of the table. Since you are going with a larger wall, Id recommend 4 of them as you mentioned.