Just a quick idea: does somebody allready experimented with “blacklight”? This is basicaly UV light betwenn 350 and 370nm. Used often in dicotheques an in theatres etc. I’m not sure if webcams can see this part of the spectrum, but if yes it would be a cheap and efficient method to do DI and FTIR with that. The lamps are fairly cheap and they have pretty much powe compared with LEDs. Beside that you would not need to solder etc, since you can get the lamps in different legths between 30 and 150cm. I’m not sure but a bandpass filter should be also available for 350nm… Another interresting point would be that FTIR could also easily work with Fiducials - you just had to use fluorescent paints or foils for the fiducials…

What do you think about?

Maybe.  I think it would be more practical for DI then FTIR, given the size of the bulbs.  Here is a bandpass filter for UV light.

http://www.asahi-spectra.com/opticalfilters/syousaik2_ver2.asp?key=ZUS0350

You should try it out and see, that is the best way to find out if it works.

Isnt UV light harmful to eyes?

UVB is the cause of skin cancer! 

From WIKI “While “black lights” do produce light in the UV range, their spectrum is confined to the longwave UVA region. Unlike UVB and UVC, which are responsible for the direct DNA damage that leads to skin cancer, black light is limited to lower energy, longer waves and does not cause sunburn. However, UVA is capable of causing damage to collagen fibers and destroying vitamin A in skin.”

You have been warned

You can also get UV LEDS cool!

Allright, i have done some theoretical research the past few days. I think now that an FTIR setup is possible with blacklight (i’m not sure if rear DI could work...). There is no exact literature anyhow about the sensitivity of the camera sensors (the cameras we are using) in that wavelenght, but deducing the spectral curve of the Fire-I, the sensor should be able to receive enough information at 370-380nm. To avoid damages to the eye, it should be easy to use a transparent UV-blocking film in your setup (on top of your setup or under the projection layer). I assume that we can use the glass of the lightsource for the camera as bandpass filter - that sould block the visible spectrum and allow the exact emmited wavelenght. But this is theory - i try to find some time over the weekend and test out some things… But feel free to do the same - blacklight are realy cheap and easy to get )

Cheers!

I’m not sure I understand your proposal. If you use a UV blocking material on the projection screen to protect your eyes, how will UV light be transmitted from your fingers to the camera?

Technodai,

take a look at the schematic of Tim Roth about his layer setup for FTIR. Exchange the IR blocking film with UV blocking film an there you are… http://www.timroth.de/180/page5/page5.html .... But far as i can judge there is not more risk using blacklights than IR. Both spectral waves burry the same risk - too much or too strong “invisible” light CAN damage your eyes over the time. Sorry but my english is not sufficient for an exact explanation why this will happen Anyhow if the camera can see that wavelenght the idea COULD work. Will keep the community update…

I’m sorry I didn’t realise you were talking about FTIR. I’m new to this mularkey and am a bit DI focused at the moment! I still think there might be some confusion about the differences between the two methods though…

Hey All,

here’s a short update regarding my “blacklight research” I brought 2 blacklight sources over the weekend 1 is 120cm wide for illumination another one was a smaller bulb (used just for breaking out a piece of glass for testing as a provisorical UV filter). Far as i can tell my cam (Fire-I) is brightly illuminated with the UV-Light. A funny thing tough: first i was trying to see what happens keeping the two layers of foto-film inside the camera as IR-Filter. The lightsource was clearly visible - reminded me at star-wars somehow . I removed the IR-Filter after that and just put a piece of the broken glass from the second lightsource in front of my cam - the results looked promissing - just like the filtered results in the IR-spectrum… Anyhow: now’s time to test this stuff realy out I will get this week two standard “edge-light aluminium-profiles” from a friend (this edge-lighted displays with blacklights a very common...) and i will build a quick setup with 2x120cm lightsources and a 1200x900x10mm polished acrylic plate. I am very curious how this stuff acts in a “real” environment… Will keep you updated…

Any results Sandor? I’ve been thinking along the same lines recently and discovered your post. By the looks of it, it should theoretically give better results than infrared setups due to increased camera sensitivity at that range and decreased background radiation from the sun (when compared to infrared).

http://nuigroup.com/forums/viewthread/3007/

@Nade: his results

http://nuigroup.com/forums/viewthread/2564/

edit: you already found it, my bad