This is a show-stopper question right now and I’m hoping for a really quick response:

Does tempered glass interfere/block infrared light?

Many forum members talk of using glass instead of acrylic for it’s increased stiffness. And since most touch surfaces span open gaps, tempered glass seems to be the safest bet to prevent shattering. But I’m hearing conflicting reports that tempered glass blocks infrared light. If true, wouldn’t the mean that tempered glass can’t be used for rear illumination DI surfaces?

I have done primitive experiments with frosted glass and it doesn’t block IR light.

Thanks for the response.

I’ve actually been doing a tremendous amount of research and experimentation with different materials and films. These NUI Group forums have been a fantastic resource and I hope to reciprocate once my imminent deadline passes.

As regards frosted glass, otherwise known as sandblasted or acid-etched glass (depending on what effect you’re going for), it’s a surface alteration so I wouldn’t particularly have expected it to affect transmissive properties. Tempering glass, or heat strengthening glass, is more of a chemical alteration because (I imagine) the tempering process affects the crystal structure of the glass. For one, suddenly the glass is a poor conductor of heat. It’s much harder and it also shatters differently.

I’m mainly concerned about IR transmissivity because, obviously, that’s a requirement for rear illumination DI. I had been hearing various tales about how tempered glass can be used as a heat shield and became concerned about how that might involve blocking IR light. I gave one of the engineers at Edmund Optics a call though, and she’s fairly confident that all glass, tempered or not, will only begin to affect light when it’s wavelength approached 1 micron. As we’re all mainly using 880nm IR LEDs, near-IR, she doesn’t think tempering the glass will be a problem.

I sent out an order for a large plate of it just this morning and wanted to check with the NUI Group forums to see if any of you had a more definite answer or maybe even some experience working with tempered glass?

I think a couple people have used tempered glass for DI. If I recall correctly, a couple people used frosted tempered glass from ikea with no issues. I don’t believe there should be any issues where it reflects or blocks IR. I’m pretty sure you should be fine.

Well regular glass windows of a house don’t block IR light, point your camera out the window and you’ll see.

Frosted glass might have issues depending on how it gets the frosted look. If it’s sandblasted or something like that, it may work well. If there is a film on the top or a substance mixed in with the glass it may cause problems.

Hey Johnny, how did everything turn out? I too am considering tempered glass for a very large (160” wide x 60” tall) DI multitouch wall…

I’m eager to gear what you chose to go with.

Thanks!

Warren

Im in the middle of a 72"diag one, will let you know how it works (using ikea glass)

Glass does absorb a bit of light, one thing i noticed while experimenting...I needed tons more leds with my sandblasted glass compared to a piece of plexi w/ projection surface.

Does anyone have any updates on this?  I’ve been experimenting with a 1/2” piece of tempered glass.  The glass isn’t the best quality and has a slight tint to it.  I’m using 850nm IR led arrays, and it’s amazing how much absorbtion (or possibly reflection) the glass has.  comparing it to acrylic, it doesn’t look like its refecting any more light though.

Ignore the crappy job I did applying the projection material.  Notice the huge difference in open air reflection on my hand vs. through the glass.  I think the Fe content (slight green tint) plays a huge roll in this.  Especially when companies like Ideum are able to use tempered with their product.

I’m building a table with an IKEA coffee table that comes with a tampered glass top.
The glass is perfectly transparent and IR light goes through it easily.

a_netanel - 14 November 2010 03:18 PM

I’m building a table with an IKEA coffee table that comes with a tampered glass top.
The glass is perfectly transparent and IR light goes through it easily.

Are you using 850nm Wavelength for your emitting IR?

Chadzero - 16 November 2010 03:13 PM

Are you using 850nm Wavelength for your emitting IR?

Nope. I’m using 780nm lasers.

a_netanel - 14 November 2010 03:18 PM

I’m building a table with an IKEA coffee table that comes with a tampered glass top.
The glass is perfectly transparent and IR light goes through it easily.

Was it this one, by any chance..?

http://www.ikea.com/ie/en/catalog/products/S49870870

I’m putting together a table and this would be a quick and easy solution.

Thanks,
L.

After doing quite a bit of research and testing.  You’ll want to go with a low-iron glass to help with any transmission problems.  The difference is drastic.  Guardian Ecoguard and PPG Starphire are two brands that have worked well in my 850nm testing.  I haven’t tried Pinkerton Optiwhite.

The toughest part is sourcing this glass in low quantities.  Craftsmen Glass in Houston is where I was able to find the Starphire at for a great price.

hi guys am new and i have been following frosted glass forum, am wondering what thickness can be used and will it work for DI.THANKS

Liam - 04 January 2011 02:12 PM

a_netanel - 14 November 2010 03:18 PM

I’m building a table with an IKEA coffee table that comes with a tampered glass top.
The glass is perfectly transparent and IR light goes through it easily.

Was it this one, by any chance..?

http://www.ikea.com/ie/en/catalog/products/S49870870

I’m putting together a table and this would be a quick and easy solution.

Thanks,
L.

have you tested the IKEA glass? How does it perform in case of IR reflection? Is the effect so massiv as Chadzero noticed - would be nice if you share your experience!