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FrozenGate by Avery

line gen - optics vs spinning mirrors

W

wicked1

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May 18, 2008
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I want to build a line generator for a hand held laser..
would I be be better off w/ spinning mirrors, or a glass optic?

Space isn't really a concern, as I was going to build a 3 motor spiro into this.. so, either option will be smaller than my original plan.

I guess, which has the least losses, and is there a way to control the spread of the beam with either method (as in, a 45 degree spread, or 90 degree, etc)

thanks!
 





Spinning mirrors will not be able to generate a line. Only galvanometers can do that. Your best bet is to buy a line generating optic, and no, you will not be able to control the angle.

DealExtreme: $4.07 Red Laser Module - Focused Line (3.5V~4.5V 16mm 5mW)

Get one of those, and take out the lens. Thats what I did and it works well. It's definitely wider than 90 degrees, probably more like 130 degrees. I don't know where else to get just the line lens for any cheaper.

-Tony
 
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Really? I've done it before with good success.
just epoxy a tiny mirror to the top of a motor shaft.
The line optic is of course easier!
 
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I dont think you understand.
You glue it on the other way ;)

Ill take a pic if you don't know what I mean, if i can find it.
 
CrazyMonkey said:
Really? I've done it before with good success.
just epoxy a tiny mirror to the top of a motor shaft.
The line optic is of course easier!
Click to expand...

Did you mean on the side?

Yes that'll work but you'll loose half of of the power and the angle still will not be adjustable. There is no point not to just use the optic.

-Tony
 
Correct. Top of shaft, side of mirror.

I needed a line because I was making 3d models.
DAVID 3D Scanner

I had a powerful laser, loosing 50% was nothing :)
was faster to make one in a few minutes then order an optic.
 
Xplorer877 said:
Spinning mirrors will not be able to generate a line. Only galvanometers can do that. Your best bet is to buy a line generating optic, and no, you will not be able to control the angle.

DealExtreme: $4.07 Red Laser Module - Focused Line (3.5V~4.5V 16mm 5mW)

Get one of those, and take out the lens. Thats what I did and it works well. It's definitely wider than 90 degrees, probably more like 130 degrees. I don't know where else to get just the line lens for any cheaper.

-Tony
Click to expand...

WHAAT?!?! Your kidding right? a spinning set of mirrors can indeed create a line. It's called a polygon scanner and they are very easy to get. the mirror spins around the outside diameter creating your line.
SHARP LASER ASSEMBLY - Surplus Shed
 
I know you understand now, so please don't think I'm trying to insult your intelligence, but I was bored, so here is a Google SketchUp(Highly recommended) pic.
Pictures are so much easier to understand! Top is circles, bottom line.


3069-mirrors.jpg
 
And, it seems to me that having the spinning mirror, both sides reflective (or I could even build a little square w/ 4 mirrors or somteing) would be less lossy than a glass optic, but im not sure...
Its for a 1watt 450, if that makes any difference..

Im all for easy and small so the glass has pluses there...
Any way to change the spread w/ mirrors? number of mirrors, or angle you hit them w the beam or something? (im thinking # of mirrors might change that.. but am on vacation today and not thinking too hard :) )

a 90 degree or slightly less spread would be ideal..
 
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They make something called a polygon mirror just for these sorts of applications...
 
CrazyMonkey said:
I know you understand now, so please don't think I'm trying to insult your intelligence, but I was bored, so here is a Google SketchUp(Highly recommended) pic.
Pictures are so much easier to understand! Top is circles, bottom line.


3069-mirrors.jpg
Click to expand...

Still is a "circle" though. It's just your projecting the circle differently. Rather than having the circle hit the wall parallel it's hitting it perpendicular. In other words, if the mirror was thinner than the beam diameter and the beam was centered over each side of the mirror when it becomes parallel with the beam, it will "paint" a circle around the things in it's path. Sure if your in a box, each of the four flat walls it hits will have a "line" but it still really is a "circle." So really whats happening from your view point is each wall is taking a 2d shape from its side. If you were to slowly angle the mirror, you would then see the circle fold back on to one wall. Does that make any sense?

I'm not saying it's not a line from your viewing point to a flat wall, but it is still coming from a circle. Also, if I did, I'm not trying to sound harsh or anything at ALL. Sorry if I did, just wanted to say. :)
 
haha.. I know what you mean.
With a front side mirror though, it wont do a line 360 of course.
You can block off whatever angles you want though.
Do be careful with this approach. Don't be anywhere in the laser plane.
This is possible of course due to persistence of vision.
A optic will make a real solid line. If you jiggle the laser/mirror you may see the swipes.
 
CrazyMonkey said:
haha.. I know what you mean.
With a front side mirror though, it wont do a line 360 of course.
You can block off whatever angles you want though.
Do be careful with this approach. Don't be anywhere in the laser plane.
This is possible of course due to persistence of vision.
A optic will make a real solid line. If you jiggle the laser/mirror you may see the swipes.
Click to expand...

Yeah, that's true. It will need to have both sides reflective. Missed that. Thanks. :)
 
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