I have a few CD-ROMS and DVD-ROMS just laying around at home.If i can find a way to disperse it (i don’t understand how alex did it) i may try this.

The plastic rod looks excellent, off I go ordering lasers.

laser what kind of laser :p ?
i break many burner lasers and any laser works fine :(

jajaj

see ya

I thought DVD’s used a 650nm wavelength as opposed to 780nm that CD lasers use.  The longer wavelength would be better suited would it not? (and also be less visible to the naked eye)

Does a cheap dollar store laser emit IR as well? Wouldn’t it be concievable to just use the same principle of an IR bandpass infront of the laser to block the visible spectrum and just allow the IR through.

@ chubbs: with a dollar store laser you the user would also be able to see the blobs which would be a hindrance when combined with a projector or lcd monitor. We really dont want to see the place where we touch on the screen we only want touchlib to see it.

Taha

@ taha

what I was suggesting was putting exposed phoitonegative over a regular near-infrared laser… allowing the radiated ir to pass through for the cam.

I didn’t think of that, it seems like an interesting idea… i’ll go test it out. Thanks

Taha

Chubbs - 30 May 2008 01:45 PM

I thought DVD’s used a 650nm wavelength as opposed to 780nm that CD lasers use.  The longer wavelength would be better suited would it not? (and also be less visible to the naked eye)

Does a cheap dollar store laser emit IR as well? Wouldn’t it be concievable to just use the same principle of an IR bandpass infront of the laser to block the visible spectrum and just allow the IR through.

Lasers emit single very narrow wavelength of coherent light. This means that all the photons of emitted by the laser are in sync - there is no light cancellation in the light beam. So you get all the power of the laser in one single wavelength. This is one of the reasons why the laser light is so powerful and efficient.

So to answer your question, the idea of using a regular red laser and somehow trying to filter out and use the IR will not work here.

You are right, DVD drives use standard red (640nm) laser diode, and CD burners use NIR laser diodes around 780nm.
If you get a combo DVDR/CDR drive it will have both diodes in it. Now the faster the burning speed - the more powerful laser diode is used.

Now again, in order to generate a plane of laser light you would have to use a cylindrical lens that will spread the light in one direction only.

I included some pictures of the lens I’ve been experimented with in the past.

Hey Alex,
Where did purchase this cylindrical lens from and does it have a special name?

Taha

@ Taha : I got the lens from my Craftsman laser leveler. The whole assembly is very easy to remove.
You can even install your own laser diode in it. It is compatible with standard TO-18 (5.6mm) laser diode package.

Alex

Ohh thanks Alex, i’ve got a laser leveler time to rip the lens out and do some testing.

Thanks

Taha

So now the new question is what/where is the best place to order an IR laser… I’m not the most knowledgeable person when it comes down to wiring and circuitry, but I’d love to get this going.

Wouldn’t this system be much more feasible with an LCD screen because you just like embed one on each side of the screen and then you would a quick and dirty way to add multi touch to an LCD screen....
Damnit… that wouldn’t work because you need to ave a camera reading the laser light behind the screen. It would still eliminate one step (building the FTIR assembly and creating a compliant surface) you would still need to remove the back of the LCD and add your own back light though. Has anyone ever tried an LCD screen multi-touch setup with a large LCD screen? and if so; could I get a link to that?

Finally, if noone else has done this then I might be the first one in the large LCD department and the third/fourth(if you count microsoft), to try out the IR laser system.

Thanks in advance for all your help!

@fuz

to my knowledge Microsoft hasn’t done a large LCD IR laser system.

edit: unless that was an lcd projector…

It seems the Microsoft now has a system for Large LCD displays & projectors called LaserTouch see my post below.

Note the link to kurzweilAI.net’s article may or may not be working but I have provided alternative links + some of the article in a fallow up reply.

http://nuigroup.com/forums/viewthread/2096/

Thanks,
Ken