# How do these straight line lasers work?

## Main Question or Discussion Point

I am not sure what the thing is actually called, but let me see if I can describe it. It is one of those products advertised on tv, that you put on a wall and it shoots a laser beam all along the surface parallel with the ground.

The problem I can't figure out is, some of them claim it can go around corners (i.e. around a corner onto a wall the device can't even see directly).

It seems like this should be impossible to me, and I can't figure out how it would work. Anyone have any idea?

-JasonZ

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Tide
Homework Helper
Light can go around a corner if you use a mirror! :-)

Tide said:
Light can go around a corner if you use a mirror! :-)
Haha, of course...but they don't claim to use any mirror in this commercial.

-JasonZ

Light can go around a corner to a small degree by diffraction, but in your case I doubt this is so, because from what you described, it sounds like the laser has to make a 90° turn. I don't know what this advertisement is trying to sell, but if it's something like a detector, then it could be possible that this laser can go through walls.

DaveC426913
Gold Member
It's called the Laser Straight, and you can Google it. I found this: http://www.asseenontv.com/prod-pages/laser_straight.html?gid=

As for the "going around corners" mystery, it's a "think outside the box" problem. What does it mean to go around a corner? We *assume* that the device is attached to the same wall that has the corner.

No, the laser is not the trick, the placement is the trick - just attach it to a wall *opposite* your corner, and point it strategically. It shines across everything - inner corners as well as outer corners!

Look at the images here: http://www.surftilyoudrop.com/laser-straight.htm [Broken]

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DaveC426913 said:
It's called the Laser Straight, and you can Google it. I found this: http://www.asseenontv.com/prod-pages/laser_straight.html?gid=

As for the "going around corners" mystery, it's a "think outside the box" problem. What does it mean to go around a corner? We *assume* that the device is attached to the same wall that has the corner.

No, the laser is not the trick, the placement is the trick - just attach it to a wall *opposite* your corner, and point it strategically. It shines across everything - inner corners as well as outer corners!

Look at the images here: http://www.surftilyoudrop.com/laser-straight.htm [Broken]
Yes, it appears from those pictures that the laser comes out as a straight line rather than a single spot. That is, if you shine it on the wall, it looks like:
"____________________________________"
rather than
"."

Thus, if you put it on the opposite wall, it will illuminate all corners.

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DaveC426913 said:
It's called the Laser Straight, and you can Google it. I found this: http://www.asseenontv.com/prod-pages/laser_straight.html?gid=

As for the "going around corners" mystery, it's a "think outside the box" problem. What does it mean to go around a corner? We *assume* that the device is attached to the same wall that has the corner.

No, the laser is not the trick, the placement is the trick - just attach it to a wall *opposite* your corner, and point it strategically. It shines across everything - inner corners as well as outer corners!

Look at the images here: http://www.surftilyoudrop.com/laser-straight.htm [Broken]

Well that makes perfect sense..though I really could have sworn they had it placed on the same wall it was going around, in the commercial. Maybe they really didn't have it attached and the guy was just holding it, to kind of trick the audience...though I don't see why they would do that.

Either way, its a neat little gadget :)

Thanks for the googling.

-JasonZ

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Integral
Staff Emeritus
Gold Member
My first thought is that the beam is scanned. They are moving it rapidly back and forth across the wall. You would see only a spot, if it held still long enough.

The scanning would also enable them to have a bit more powerful beam, and remain safe. Should you happen to look into the device, since the beam is continuously moving, it will not be in one place long enough to instantly damage your eyes.

I would not recommend staring into the beam irregardless.

Averagesupernova
Gold Member
I have used laser levels for preparing the ground prior to concrete work. I would imagine the ones used indoors work the same way. They basically have a laser shooting straight up or down and a revolving mirror to make a complete 360 degree sweep. It is entirely possible that the indoor lasers work the same way. You may have seen it placed next to a wall in the commercial and noticed the beam on that wall. Then the next scene showed a corner on an opposite wall and what do you know, there is a line going around the corner. Advertising gimmick. Although technically not dishonest, it is somewhat misleading. Incidentally, they work quite well. Speeds up dirt work incredibly.

Even if this model doesn't sweep 360 degrees it can still project around a corner (just not very far). If the beamlet sweeps let say 5 degrees and you place it flat on a wall 10 feet from the corner, the beam project along the wall the device is on the 10 feet to the corner and around the corner about 10.5 inches. They could have it sweep any angle they wanted. 5 degrees was just for the sake of example.

Averagesupernova