I think some people think you need to wear the safety glasses all the time. Even when your done tuning the display. When your using it after you built it.

justin - 03 July 2008 05:17 PM

I think some people think you need to wear the safety glasses all the time. Even when your done tuning the display. When your using it after you built it.

I’m not an expert in this by any means, but consider this:

- Under DI method, hundreds of IR LEDs shine directly in the user’s eye all the time.
- Under LLP (and FTIR) method the IR light shines only when there is a touch and this reflected light is not directed towards the user’s eye but in the opposite direction (towards the camera). According to the Class 3B specs, unless you touch the surface with an extreme reflective object, the use without the glasses should be safe.

~Alex

780nm 10mW 3.2VDC 12 x 30mm Laser Module
Would this work? Is 10mW ok or 5mW better. 10mW is brighter right?

I believe it’s better to get 850nm if you can.  It’s easier for the camera to see or something.  Although I’m sure 780nm would be fine too if you can get a bandpass filter rated for that wavelength.

I have 2 850nm at 5mW
I wanted to know if I could go to a 10mW but at 780nm AlexP has been testing 780nm with luck. just wanted to know about the 10mW

Gotcha ... I misunderstood ... my bad

It’s all good

Hello all, I have been working on building a MT table for the last month and I have built two different versions using IR LEDs, neither one has produced very good blobs (they work but not as well as i have seen others) so I have decided to look at the LLP setup instead as it seems these produce very good blobs.  I have read all the posts and have seen people talking about what to use, but have found very few links to places to buy them, I want to do 850nm because the filter I have works better for this range
on this post you give the list but not where to buy them

850nm laster diode with 10mW - http://www.thorlabs.com/thorProduct.cfm?partNumber=L850P010
Laser diode power supply circuit - ????
Focusable line with 120° spread using a special non-linear lens - ????

Also, there is a lot of talk about using safety glasses and how important it is to have these so where do I buy them?

Would it be possible to use a lower intensity laser?  I’d love to make a multi touch for my little girl and me to play with, but I can’t really reconcile the danger of damaging her eyes. I’d love to discover that I could use a low enough intensity laser that --once dispersed into a plane-- is relatively harmless.

Hello All,

We have been working with lasers for multi-touch surfaces for quite some time now and I can confirm it works great. You can check our website at http://www.future-instruments.net for a video and more information (there is a paper that we presented at the NIME conference this year - New Interfaces for Musical Expression - with title ‘Transforming Ordinary Surfaces into Multi-touch Controllers).

There is a serious issue though, concerning the security. The limit value for Class 1 is 0.6 mW for IR lasers (this value stands for 810 nm). So, even a 5 mW laser is Class 3B, which means it can seriously harm the eyes. Fortunately the danger is only for direct rays in the eye (even with line generator) and not for reflected light. We are using 80 mW (780 nm)lasers and it happened a few time that I got them directed in the eyes when manipulating them, causing some blurr that I could feel before it desapeared after some time. So anyone tempted to work with IR lasers should really be carefull, especially since we don’t see the beam.

However, we found a solution to the security problem, by pulsing the laser in sync with the shutter of the camera. We are using OptiTrack cameras from Natural Point that offer embedded blob tracking up to 100 fps and a sync pin out. With 1ms shutter time there is only a fraction of the light power that is used, while it makes no difference for detection (when the shutter is closed, the light that is still emmitted by the laser is useless). Our lab is going to invest in 5’000 $ measurement equipment to be able to determine precisely the conditions that allow to stay within Class 1. I’ll keep you informed…

By the way, it would be helpful if some of you find a RELIABLE cheap laser provider. We have been purchasing through AixiZ with mixed results. The first time it went fine but the second time it took two months to receive our order after multiple emails and confusion from their side (we received the order from someone else!).

We called this technology MUTE, standing for MUlti-Touch Everywhere. But LLP is nice too

Best
EL

This is very good news.  Please do keep us updated.  Which optitrack camera are you using?

@Easy Looping: Fantastic idea of modulating the laser beam! It makes total sense, definitely worth doing.

I also agree with finding a better laser dealer. The prices on the AixiZ site are very appealing, but I’ve been hearing from many more unhappy customers than satisfied ones.

We are using the SLIM:V100 with the optional enclosure and the 2.6mm - 800nm pass filter. http://www.naturalpoint.com/optitrack/products/slim-v100/

All together it’s about 300$. Since we don’t need the illumination LEDs, it’s a lot cheaper than the FLEX:V100 (549$).

We have developed a software for calibrating the surface and outputting TUIO events using the provided SDK. We’ll make it available soon, when it will be sufficiently stable.

As for a laser supplier, I guess the source is in China. I remember of some new member from Shenzhen recently, who is supplying various accessories for electronics. Maybe he could be of some help.

Update: I posted a message to Eric (that’s his name) asking if he could find some IR lasers module. We’ll see…

What are the benefits using LLP vs other methods

LLP = Brighter blobs, easy to install (especially on exisiting monitors), more versitle.

Check out MS LaserTouch for an example of the LLP technique here