hi there

after being part of the nuigroup for roughly one year i wanted to show off some pics and some information about the second table that i have built.

this one is called The Virttable, which stands for “Versatile Illumination Touch Table”. Here is a CAD drawing of it:

the nice part about the Virttable is that i have got the money to build it from the Computer Sciences department of my university, which is the Wiesbaden University of Applied Sciences. By the way, our Computer Sciences department has very nice information visualization research possibilities under the lead of my professor Dr. Doerner. so anyone, who is interested in studying Compuer Sciences in Germany and likes multi-touch and visualization: Wiesbaden would be a good choice for you for sure

to get back to the table: versatile illumination regards the different illumination techniques that you can use with the Virttable, which include FTIR, DI and DSI. FTIR and DSI are supported by 48 Osram SFH 485P LEDs that sit in aluminum bars to the sides of the acrylic glass. we have got both a pane of regular 8mm acrylic glass with polished borders and a pane of Plexiglas Endlighten XL glass with polished borders that we can switch by removing the lid and changing the glass pane. anyway, our DSI results were not good. thus, we are now using only the regular acrylic glass pane (or to be more precise: we have tried out toluene on the Endlighten glass, which attacked the pane’s surface and ruined it).

DI is supported by 3 aluminum bars with SFH 485P LEDs underneath the surface of the table that emit their light diagonally on the table’s surface. these are only a few but they are enough to illuminate the surface in a way to allow the use of fiducials on the table. check out this image to understand what i’m talking about (high resolution after a click):

on the left there is no illumination. the second picture shows only FTIR, 3rd only DI and finally on the right picture there is the hybrid solution with FTIR and DI. this works nicely.

we’ve built the Virttable’s setup in a way that everything is accessibe and can be exchanged easily. something that is not shown in the CAD drawing are two fans that we use to guide the hot air inside of the casing out through the ventilation openings.

some ingredients that we used for the Virttable:
- Panasonic PT AX 200
- Pointgrey Firefly MV and Unibrain Fire-i
- optical highpass filter B+W IR filter 52 093 (i tried 2 thorlabs bandpass filters but they did not work AT ALL for me. the b+w filter, which is made for photography, costs the half and yields better results than the negatives and lots better results than the thorlabs filters.)
- A Mac Mini
- for multi-touch tracking: fast touchlib version from AlexP
- for fiducial tracking: reacTIVision
- Gerrites OptiTrans
- lots of Osram SFH 485P

here is an ‘x-ray’ image of the Virttable:

and a view from all sides:

and a front/top view:

and finally you can see that i measured the dimensions in a way that the Virttable fits in a locker:

you can find some more pics of the Virttable’s build process and some more background information about the Virttable here in my blog.

Wow now thats one plush looking build!

Very very nice

Woa Nice table man. Love the DI+Ftir mashup.

Do you have a compliant layer for the FTIR?
What is the projection surface?

thanks for the compliments @sharath and @ajlovegrove!

@cyandesign we use a layer of sortaclear (5 scotch tape layers thick ) and as a diffuser we use a Gerriets optitrans foil. however, the optitrans is not the best choice for object tracking. thus, when we figure out problems with the lighting in bright surroundings we instead use another acrylic glass pane with a white lee diffuser foil, which provides a better contrast for the fiducials. besides, the lee acrylic glass pane is also provided with a sheet of sorta clear.

It is a very nice setup. Love it. Looks very solid.
I ask about your projection surface because I used a piece of vellum on my prototype and I didn’t expect it to warp as much as it does when the temperature and humidity changes, how does the Gerriets optitrans foil work in different atmospheres?
And did you acquire it online? Is there a site you can link us to purchase the Gerriets optitrans foil?

hi cyancdesign

actually, i do not know how the optitrans behaves under hot conditions. it does not get hot from below as we installed two strong old server fans, which do a pretty good job. and in Germany i has not been that hot since like half a year or so. thus, i can’t tell you definitely how the optitrans would behave under hot weather conditions. but since half a year or so the optitrans lies flat on the acrylic glass pane/ silicone sheet.

i asked gerriets (http://www.gerriets.com/de/index.php) via email ( ) if they could send me an offer and they did. you have to buy at least 100 cm x 214 cm and it did cost 61,55 euro for us. by the way, it’s a German company so i don’t know how much they want for shipping in other countries…

Hi Johannes,

This is a fantastic piece of work - the finish quality of the product as well as the apparent performance are very impressive!  I’m curious about a statement you made in a post above:

>> thus, when we figure out problems with the lighting in bright surroundings we instead use another acrylic glass pane with a white lee diffuser foil, which provides a better contrast for the fiducials.

What is “white lee diffuser foil”?

I’m also curious - is the system able to track fiducial markers that are above the surface?  If so, how far up?  I’m interested in designing a system that can track fiducial markers both on the surface, and up to ~10cm above the surface.

Cheers,

Jason Morrison

http://projectsmartlab.org

very nice work , hows the interface of your table is it ON/OFF by switch.did you made any video of it

Hi Johannes,

Impressive piece of work I must say. I am curious about one thing, and I quote from your personal blog:

In the Virttable DI is provided by a few aluminum bars equipped with Osram SFH 485P LEDs underneath the tabletop. The bars are diagonally emitting their light onto the underside of the acrylic glass. Each LED is covered with a piece of masking tape to disperse its light evenly and to prevent hotspots.

I have tried both DI and FTIR as well as a combination of them, which seems to produce the best results, but I have huge problems with hotspots due to the LEDs reflecting at certain positions at the bottom of my acrylic. I am using the same LEDs as your setup, about 300 of them and I was wondering what kind of masking tape did you use to prevent the hotspots. I myself have even covered them with a 5mm thick piece of projection screen acrylic but that was no success. Even turning the LED’s upside down seems hopeless, as the hotspots become weaker but are still present. So I ended up sticking my projection material (Mylar) at the bottom of the acrylic to avoid the LED’s reflections (that doesn’t seem to be the right solution however).

A picture of the DI LED’s would be really helpful here, if that is possible for you.

Thanx a lot and keep up the good work

thank you very much jayunit, password and MelCy.

i’ll try to answer your questions.

@jayunit

What is “white lee diffuser foil”?

A sheet of frosted Lee 225 foil.

I’m also curious - is the system able to track fiducial markers that are above the surface?  If so, how far up?  I’m interested in designing a system that can track fiducial markers both on the surface, and up to ~10cm above the surface.

unfortunately not. the diffuser foil blurs the markers quickly. this means that if you want to track fiducials on your table you will get much better results if you put the diffuser foil on top of the acrylic glass. if you put it underneath the acrylic glass it will blur the contrast of the fiducials for the camera. in that case you would need MUCH bigger fiducials. thus, if you used VERY big fiducials you could track them up to a certain distance above the table. how much above i don’t know.

@password

very nice work , hows the interface of your table is it ON/OFF by switch.

unfortunately not. but i have bought all switches and push buttons to do so. you can connect a push button to the power button of your windows xp pc and if you push it it will start the pc and it will shut down the pc GENTLY. thus, you can attach that push button easily on the outside of your pc. a very nice example for such a push button is this one. but i do not know how to attach a switch to my projector. i cannot switch it off at once because it needs to cool out after using it…

did you made any video of it

not of the actual table. in that post you will find a video of Vispol, which is running on that table. but unfortunately not of the table…

@MelCy

I have huge problems with hotspots due to the LEDs reflecting at certain positions at the bottom of my acrylic.

we have used only a few LEDs (around 30) for DI and the focus of the LEDs is pointing on the border of the acrylic glass as you can see in that picture (clicking enlarges the picture):

thus, the hotspots do not interfere with the actual tracking as they lie outside of the tracking cutout of the Touchlib.

I am using the same LEDs as your setup, about 300 of them and I was wondering what kind of masking tape did you use to prevent the hotspots.

i don’t know if there is an english term for it but in germany it is the tape that you use to mask doorframes and so on when you are painting a room. maybe it is called paint masking tape? in german it is malerkrepp.

A picture of the DI LED’s would be really helpful here, if that is possible for you.

i have no access to the Virttable until next thursday but then i will shoot some photos! but until then maybe that picture will be sufficient:

the picture really helps me on:

1. the tape that u r using
2. I got confirmation on the lower LEDs setup (I sorta figure the setup out, when you said “focus on the frame border")

I really want to go to wiesbaden (got my diplom in germany), but I’m still waiting for my KTH admision

nice setup man. vielen dank

What white material did you line the box with to get that look? Nicest box ive seen!

nevermind i see the over spray off paint, did you build it with mdf? paint spray or roll on?

hi jyoung58,
thanx for the compliments!

the box is built out of 16mm mdf boards. the paintwork has been done by a carpenter from our university. it is painted with standard white furniture lacquer. it has been sprayed on, looks really professionel and, well for a better imagination, it looks like the lacqer on white ikea furniture like the (in Germany very popular) ikea billy shelves.

nice build! Is it necessary to have a compliant surface with a FTIR/DI setup? Could you just have the following?

(Top)
- glass or acrylic
- diffuser
(Bottom)

Thanks

hi adtuent,
if you want to use objects you will need to put the diffuser on top of the glass or otherwise the objects will be blurred.

if you want to use the hybrid setup with ftir you will need to use a silicone sheet between diffuser and glass or otherwise you have problems in producing appropriate ftir blobs.

alternatively, you can use an endlighten glass (for dsi) instead of the usual (acrylic) glass. then you do not need the compliant surface. however, then you would not need the additional di illumination either.

but i have to admit that i do not like the results that i had in my experiments with dsi. anyway, there are others that had good results with it.

as you might have guessed i prefer my di/ftir hyprid approach as compared to the dsi approach.

cheers

we have refurbished our setup with more and stronger led’s.

for ftir we now use osram sfh4550 which are WAY stronger than the in comparison poorly performing sfh485p’s.

in addition we used more led’s: now we use 180 sfh4550’s, eheheh. so that is a strong ftir-setup. we soldered the sfh4550’s on these pcb’s. we power them with a standard atx pc power supply.

to get a stronger di-illumination we used six of those high power infrared led’s with 4 led’s on one dye (Aculed VHL IR 4-chip High Power LEDs). we glued them on heat sinks that look like stars (see the pictures below).

the results are quite nice. fiducials on the table (that we run in Flash with our framework fiducialtuioas3) are now working effortlessly on the grey Gerriets Optitrans where before we could only use those fiducials on the white frosted LEE diffuser foil.

we plan to use two cameras in future (one for fiducials and one for touches) in order to use different camera parameters. touches can be better sensed with a camera with a low exposure and fiducials can be better tracked by a camera with a high exposure.

however, currently we only use one camera and use reactivision to track fiducials and touch.

In your blog you say you use a Unibrain Fire-I.

Did you use the B/W or Color Digital Board Camera? And which lens did you use?

I’m kinda new to this and have to order all my stuff from Europe as I live in South Africa, so it would be nice to get the correct components first time.

Thanks.

at first we used the fire-i, which ran with only . afterwards we have switched to the firefly, which supplies 30Hz@640x480 and a better near-infrared performance. both cameras are firewire and the color version.

we tried both, a zoom lens and a fixed wideangle lens.

this is the wideangle lens: http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&item=220432406193
the zoom lens is a Tamron 13VM308ASIR.

the wideangle lens is cheaper and i think it’s sharper in the details. however, you can’t zoom with it…

can you please check the links for the LEDs of the DI setup, because perhaps the type of the LEDs you used is no longer available. would be nice to have the type of the LEDs to get a datasheet. and what about heat and illumination with those LEDs? is the heatsink enough? do you get even illumination? no hotspot? is the frosted side of the acrylic on the bottom or on top(do you touch the frosted side)?

i’m trying the osram ostar sfh4730 LEDs:
http://catalog.osram-os.com/catalogue/catalogue.do?favOid=000000000000cd9800da0023&act=showBookmark

what do you think about these?