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ArcticMyst Security by Avery

Help focusing my 50mw laser pointer into a burning laser

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Oct 12, 2012
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I bought this 405nm 50mw Laser pointer. I wanted to use it to pop balloons and light matches but unfortunately it was not powerful enough. While browsing the forums I found this guide and decided to see if it would work.

I was able to get the laser opened up successfully and I purchased this laser housing kit off of ebay. When I tried to screw in the lens to my housing in my laser it was too small. It turns out that it didn't matter because my laser had no thread lockers and I could focus it with the original lens. So I did my best to focus the beam. The dot did get tighter but I still was not able to burn anything.

My question is: Is there a technique to focusing that I'm not aware of, or do I have to purchase a different lens to get the job done? If I have to buy a new lens, what type would it have to be and if possible I would appreciate links!

Thanks,
FrozenClear
 





mwang

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First off, before you start to burn anything with any laser, remember, ANY laser that can pop a balloon or light a match is extremely dangerous to your eyes, and you should get the appropriate safety glasses for the laser. Remember, you only have one set of eyes.

If you want a burning laser, you should probably invest more than you did. Those Chinese lasers rarely ever perform on spec. Your laser probably only outputs 5-10mW if you are lucky, and is probably not powerful enough to do any burning tasks, even with a lens. Try searching around on this forum for reliable people, stores, and websites to buy quality lasers.
 
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If you want a burning laser, you should probably invest more than you did. Those Chinese lasers rarely ever perform on spec. Your laser probably only outputs 5-10mW if you are lucky

You might be surprised - and I'm guessing you've never used this model.

I have the very same (well, it looks exactly the same) and although I don't have an LPM, it must be putting out a fair whack of power as it has a prominent beam in a dark room, lights a room up enough to act as a sort of UV bulb, and does burn when focussed.

Back to the OP: you can try focussing it using a magnifying glass or, as I did, a camera lens. I only did this because I couldn't find a magnifying glass at the time and I just wanted to try it out, but as soon as the dot had focussed to a tiny point, smoke immediately started appearing from the black box I'd focussed it on. That should light at least a black match head and probably burst a dark balloon or two.

The best way of course is to simply buy a proper focusable laser, they usually come in much better hosts than the pen lasers and so have a whole ..host.. (pun intended) of advantages, like longer duty cycle, sturdier build and safety features like an aperture shutter or key lock.

Regardless I'd look after your current laser as it's a lovely wavelength - try shining it in a glass of tonic water for instance and you'll see what I mean - but be safe and aware of reflections.
 
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mwang

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You might be surprised - and I'm guessing you've never used this model.

I have the very same (well, it looks exactly the same) and although I don't have an LPM, it must be putting out a fair whack of power as it has a prominent beam in a dark room, lights a room up enough to act as a sort of UV bulb, and does burn when focussed.

If he cannot pop a balloon even with an unfocused beam, the laser is pretty weak. You cannot assume that his laser is the same as yours just because of the appearance, I know that that host is used extremely widely among Chinese sellers. I have seen one 405nm laser that barely put out anything, and was metered at 4-7 mW.
 
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Many many years ago someone posted instructions and demonstration on the web showing a 5mw red laser leaving burn small marks in wood. There was no modification of the laser itself or the optics of this laser. It was done using two external optics. The first optic was used to expand the beam greatly and the second optic was used to focus the beam into a very tiny spot. A focused 5mw laser can produce millions of watts in a small area. What matters is power density.
 
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Many many years ago someone posted instructions and demonstration on the web showing a 5mw red laser leaving burn small marks in wood. There was no modification of the laser itself or the optics of this laser. It was done using two external optics. The first optic was used to expand the beam greatly and the second optic was used to focus the beam into a very tiny spot. A focused 5mw laser can produce millions of watts in a small area. What matters is power density.

You posted this somewhere else too, and my answer there was the same as it will be here.

With 5mW, you will NOT be burning anything. You just won't.
 
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Sep 29, 2013
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I have videos of my $20 burning laser, but it can FOCUS. I have smaller pens like yours and while the measure roughly the same (55mw) cannot be focused and therefor cannot burn. If you want a burning one just get a focusable one.

dqktgk.jpg


http://laserpointerforums.com/f46/lpm-test-videos-2-ebay-405nm-bluray-lasers-86944.html

Lighting a match

https://www.youtube.com/watch?v=oPWlfxTJm3k
A little wood burning

https://www.youtube.com/watch?v=sHIndeism2U
 
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Zeebit

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If he cannot pop a balloon even with an unfocused beam, the laser is pretty weak. You cannot assume that his laser is the same as yours just because of the appearance, I know that that host is used extremely widely among Chinese sellers. I have seen one 405nm laser that barely put out anything, and was metered at 4-7 mW.

The pens are are mostly overspec in the range of ~50mW but its possible the the one the OP got is just weak. How can you say that when an unfocused laser can't pop a balloon it is weak? It would make more sense if could not pop when its focused.

Many many years ago someone posted instructions and demonstration on the web showing a 5mw red laser leaving burn small marks in wood. There was no modification of the laser itself or the optics of this laser. It was done using two external optics. The first optic was used to expand the beam greatly and the second optic was used to focus the beam into a very tiny spot. A focused 5mw laser can produce millions of watts in a small area. What matters is power density.

Your statement is partially false. Focusing the spot does not produce millions of watts. A mw of power will always be a mw no matter how big or small the spot is.
 
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Pman

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Take a look at my pen tutorial. Can't imagine how many <$5 pens I've made fully focusable with some well over 100mw. Safety first, last and always;)
 
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You posted this somewhere else too, and my answer there was the same as it will be here.

With 5mW, you will NOT be burning anything. You just won't.
Technically you are correct stating 5mw won't burn, but that is not the question asked by the OP which is:
My question is: Is there a technique to focusing that I'm not aware of, or do I have to purchase a different lens to get the job done? If I have to buy a new lens, what type would it have to be and if possible I would appreciate links!

For the second part yes it can add up to million or millions of watts either 2.2 million or 22 million if the spot is made small enough. I don't remember clearly because this how to was online more than 14 years ago.

Correction.
Here's the evidence:
it is important to note that extremely high power densities are achieved at the focal point of a concentrated laser beam. A 10-milliwatt beam focused to a diffraction-limited spot 0.22 micrometers in diameter results in a power density of approximately 30-million watts per square centimeter. Molecular Expressions Microscopy Primer: Specialized Microscopy Techniques - Laser Systems for Optical Microscopy

A 5mw would be approximately 15 millions watts sq. cm and per sq. millimeter 150,000 watts. It comes down to power density.
 
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that is correct, similar to how pixel density goes up the more pixels are packed into a square inch. but that does not mean that focussing a 5mW laser suddenly turns it into "millions of watts". I know now that's probably not what you meant but your original post read like that. the power is the same, it's just focussed energy.

ANd remember kids, energy cannot be created or destroyed - only changed.
 
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that is correct, similar to how pixel density goes up the more pixels are packed into a square inch. but that does not mean that focussing a 5mW laser suddenly turns it into "millions of watts". I know now that's probably not what you meant but your original post read like that. the power is the same, it's just focussed energy.

ANd remember kids, energy cannot be created or destroyed - only changed.
You missed the sentence where I said " It all comes down to power density"
You also followed the link?
 
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You missed the sentence where I said " It all comes down to power density"
You also followed the link?

yes I followed the link, and power "density" is not what I am disputing. However, the following, is wrong:
A focused 5mw laser can produce millions of watts in a small area.

A 5mW laser beam does not suddenly become a "millions of watts" laser beam just because it was focussed. It's just 5mW concentrated over a small area. The two ARE NOT the same thing. Focussing the energy does not create more energy.
 




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