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How could it be possible???

D

Donmichaelo

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Jun 21, 2013
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Friends:
Perhaps it is a supernewbie question but how could be possible that two green lasers, one reading 151 mW and another 377 mW, both on a LaserBee A 2W, the one with 151mW burnt easily a match and the higher one couldn't do it?
One hint is that the higher one came direct from a Chinese Company and the other one came from one of our members....
What does it make the difference here, in term of parts? the lens? construction? Both?
I have promoted myself here to buy our lasers, but never thought it would be that severe the differences.

Thanks

Miguel
 





The focus is probably different. But a 377mW laser should light matches
 
It's not about output power, it's about power density.

How big are the two lasers' dots compared?

I'd bet 370mW one is several times larger and as such has lower power density projected on the surface, compared to 150mW laser.
 
Yeah i would be pretty pissed if a 377mW would not light a match and one at half the power did, usually less than 50mW no matter how well focused has a really hard time lighting matches unless blackened and no movement and if your lucky you may get a match lit 75 mW and up is a lot easier 40mW is really hard but i digress the focus area ie density as mentioned would have to be the reason
 
Blaster said:
Yeah i would be pretty pissed if a 377mW would not light a match and one at half the power did, usually less than 50mW no matter how well focused has a really hard time lighting matches unless blackened and no movement and if your lucky you may get a match lit 75 mW and up is a lot easier 40mW is really hard but i digress the focus area ie density as mentioned would have to be the reason
Click to expand...

Dude, no offense, but seriously... punctuation.

You payed for all the keys of your keyboard, might as well use them.

It's difficult to read through your posts with same speed as normally formatted text. If you don't put periods and commas, I have to when I read it. It takes twice the time to understand what you wrote and it's frustrating.

Pretty please?
 
Eudaimonium said:
Dude, no offense, but seriously... punctuation.

You payed for all the keys of your keyboard, might as well use them.

It's difficult to read through your posts with same speed as normally formatted text. If you don't put periods and commas, I have to when I read it. It takes twice the time to understand what you wrote and it's frustrating.

Pretty please?
Click to expand...
I use my phone for 95% of my posts so i go back and typo fix when i can, so its a rather small keyboard lol
 
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Blaster said:
I use my phone for 95% of my posts so i go back and typo fix when i can, so its a rather small keyboard lol
Click to expand...

If you have an Android phone, you can edit your keyboard layout so that period and comma are immediately near Space key, which gets shrunken down a little to make room for them. It's a neat feature.

Not sure how it works on iOS though.
 
Eudaimonium said:
It's not about output power, it's about power density.

How big are the two lasers' dots compared?

I'd bet 370mW one is several times larger and as such has lower power density projected on the surface, compared to 150mW laser.
Click to expand...

Yes, you are damn right, the higher one's dot is several times bigger than the other.
Then a question comes to my mind, what part is responsible for the power density? Lenses? focal distance?
I don't see very far the moment when I will put the trigger and try to build one humble laser, at my 60's and being a MD will be a good experience.

will manner, Speedy78:
Thanks for the explanation about divergence and thickness, I got it! :)

Duplicated....really?? I wasn't aware about it, sorry to have duplicated it!! :( I can not see it duplicated now...If it is, how can be removed? (Thanks!)

Miguel
 
Donmichaelo said:
Yes, you are damn right, the higher one's dot is several times bigger than the other.
Then a question comes to my mind, what part is responsible for the power density? Lenses? focal distance?
I don't see very far the moment when I will put the trigger and try to build one humble laser, at my 60's and being a MD will be a good experience.

will manner, Speedy78:
Thanks for the explanation about divergence and thickness, I got it! :)

Duplicated....really?? I wasn't aware about it, sorry to have duplicated it!! :( I can not see it duplicated now...If it is, how can be removed? (Thanks!)

Miguel
Click to expand...

Power density is a function of total power output, and size of the dot (that is, area being illuminated by that power). I'm not 100% sure of exact formula but I'm sure you can google that easily.

Smaller dot is higher power density. If the laser is focusable, simply shifting the focus so that the dot is smaller is enough.

If the laser is fixed focus, there's not much you can do about it.
 
Well if it's easy to take apart you could hunt around for the collimating lens and adjust it yourself
 
It is possible that the 377mW you measured on your LPM is not all green light.
DPSS green lasers will leak some infrared light if it is not filtered. This extra light will contribute to the power measurement but will not affect the brightness of the green light or contribute to burning power.
The typical beam diameter near the aperture of a DPSS green pointer is about 1.5-2mm. For higher power lasers it is sometimes closer to 2-3mm. However, even at 5mm beam diameter, 377mW of green light should light a dark colored (black or red) match with little difficulty.

There are several ways to test for IR leakage and you can probably find a thread about it.

If you want to adjust your laser anyway, show us a picture of it and we can tell you if it can be adjusted and what it might involve to do so.
Although, generally green lasers are designed to be fixed focus and the beam diameter is a result of the optics used to expand the "raw" beam from the crystals. That is, adjusting the output lens/aperture lens will only change the focal point and divergence of the beam with a negligible effect on the beam diameter at the aperture. In order to get a thinner beam, one or both of the optics will probably need to be replaced.

I hope this helps...
 
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Thanks all!
Now I am doing some conferences in the Caribbean area. As soon as I can I will upload a picture of it.
I have learned so many interesting things. Thanks!!!!!

Miguel
 
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