Laser Wall

Hello, I am hoping to build a laser wall and I was wondering if anyone had any advice on how to do so.
The wall will be constructed inside in an entrance way as a way to separate the hallway and the main room. The structure will need to be fairly permanent. Currently I am planning on using two 5mw green lasers reflected across two mirrors to create the criss-cross effect. I am going to try to build a box around each of the lasers to prevent people from looking directly into the beam. The default setting for the lasers will be off but they will be turned on by a motion detector when someone walks in the door. I will either then have them turn off after a certain amount of time or have the person hit a button to turn them off.

The main issue is the visibility of the lasers. The hallway can be dimmed but I am still unsure if people will be able to see the laser beams. Fog machines and misters are not ideal because they will set off the fire alarm as well as leaving residue on the floor. Any suggestions on how to make the lasers more visible? They also have to be low powered so no one gets hurt.

FabLab said:

Any suggestions on how to make the lasers more visible? They also have to be low powered so no one gets hurt.

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Yeah, fog.:beer:

Edit: Really though - you need more particulates in the air for the light to scatter off of. That's the only practical way to make the beams brighter. May consider a hazer, I believe they leave less residue than a fog machine. They are also more expensive.

diachi said:

Yeah, fog.:beer:

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Agreed, there is no other way. It will be very difficult to see the beams otherwise.

Thank you for replying. The issue with fog is that it will set off the fire alarm. And the air in the building all gets recirculated so the air in the building will be all foggy as well.

Sta said:

Agreed, there is no other way. It will be very difficult to see the beams otherwise.

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Added an edit with a bit of a suggestion, but really it's the only practical way to do it.

Unless you go for a different effect. I've seen a cool one with a laser projector on either side each projecting a couple of vertical fans towards eachother, that was cool to walk through.

The idea is to create a barrier with the lasers beams between the hallway and main room. According to the fire code the entrance way cannot be physically or visually obstructed, but the laser beams are fine. I was reading about hazers but I wasn't sure if it was okay to be used a lot because it would need to be on for long periods of time.

FabLab said:

The idea is to create a barrier with the lasers beams between the hallway and main room. According to the fire code the entrance way cannot be physically or visually obstructed, but the laser beams are fine. I was reading about hazers but I wasn't sure if it was okay to be used a lot because it would need to be on for long periods of time.

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That's a stumper. Could you perhaps use a two layers of a transparent thin plastic with the lasers through the space between? It wouldn't be a permanent-looking barrier.

Would something that hangs work? You could make a hanging fiber optic wall.

The best thing I can recommend is using something like a diffraction grating to split the laser into a fan beam. Or, if you like the crisscrossing, you could go with something I've used before, which is one of these lenses Laser Beam Splitters - Diffraction Gratings and bouncing THOSE between the mirrors. Oh, and make sure to keep it as planar as possible so none of the beams escape.

I like the idea of the fiber optics, but that would unfortunately go against the fire code as well.

The laser beam splitter sounds interesting. And relatively cheap too! I will definitely try that option out.

Thank you so much for all the help!

Any chance of replacing the fire detectors with different types?

Heat sensitive ones obviously would have no problem with small particulates flowing around the air.

Also it may be interesting to investigate how sensive the detectors really are. Before smoking bans became common there were fire detectors installed in many places, but those were not easily triggered by cigarette smoke at all (unless you blow smoke straight into them).

Smoking bans are the bane of show lasers really. Before the bans there was enough smoke in the air of the average club to give good laser shows without the aid of fog machines and such.

It's kinda weird how the fire detection is. There are vents right near where the smoke would need to be so the particles from the smoke would go into the vents and trigger the fire alarm...most likely. And even if it didn't set off the fire alarm, all the air in the building gets recirculated so it's not ideal to have the smoke constantly in the air.

Maybe if there was a way to redirect the smoke it could work.

FabLab said:

It's kinda weird how the fire detection is. There are vents right near where the smoke would need to be so the particles from the smoke would go into the vents and trigger the fire alarm...most likely. And even if it didn't set off the fire alarm, all the air in the building gets recirculated so it's not ideal to have the smoke constantly in the air.

Maybe if there was a way to redirect the smoke it could work.

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Bah you need no ventilation.

Benm said:

Any chance of replacing the fire detectors with different types?

Heat sensitive ones obviously would have no problem with small particulates flowing around the air.

Also it may be interesting to investigate how sensive the detectors really are. Before smoking bans became common there were fire detectors installed in many places, but those were not easily triggered by cigarette smoke at all (unless you blow smoke straight into them).

Smoking bans are the bane of show lasers really. Before the bans there was enough smoke in the air of the average club to give good laser shows without the aid of fog machines and such.

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As for Benm's reply it got me thinking to ask what you want this "cool" laser wall for? I'm sure for its wow and said coolness.
If your throwing a party which most throw at night:thinking: thats a good start for visability, more people bring more air pollution whether they stir up some dust particles or smoke. Or even setting the lights low at night just sitting at home.
It doesn't take much in the air to stimulate the beam. Even when I vaccum it usually helps to see.

It's actually for a fabrication lab/machine shop type place. We have a lot of kids and random people that walk into the shop so we want to separate between the entrance hallway and the main lab area. Due to fire code we are limited in what we can put in that entrance way. There's no physical obstruction allowed. I would be able to dim the hallway to help view the lasers. I haven't tested the lasers yet so I'm not sure how visible they will be yet, but I'm assuming it will be difficult to see the beams. I don't think fog/hazers are really going to work due to the fire alarm. Mist might work if I can find a way to deal with the water it leaves behind.

Does any of the machinery put out any type of particles or oil mist. Just double checking as i'm sure youv'e have thought of this. Water mist could be helpful and probably not to much needed. Have you tried any green laser pointers for at least an idea?

They do, but they are not near the vents so it's not an issue. I have not yet tested any lasers. I have order a 5mw green laser diode to try it out but it hasn't come in yet. I think water mist would be the best way to go, but one of the higher ups at the lab said that it would leave too much water. But I was thinking I could probably do it if I had some way to prevent the liquid from building up.