How to proof that your 1.5W does not meet the spec if you don't have a LPM

My Arctic can light plain white paper on fire fairly quickly.

weeba2kv said:

i don't belive that ( video plz )

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It's quite possible for 100mW of 405nm to burn through white paper. White paper absorbs 405nm light much differently than it absorbs light at higher wavelengths. My 100mW 405nm also burns holes in white paper, it's far from being able to ignite paper like my Arctic though.

I dont think there is any means to tell power without a LPM. The only method would be comparison to a laser of known power at the same wavelength - at least you can see if its brighter or not.

r8nd0m said:

My Arctic can light plain white paper on fire fairly quickly.

It's quite possible for 100mW of 405nm to burn through white paper. White paper absorbs 405nm light much differently than it absorbs light at higher wavelengths. My 100mW 405nm also burns holes in white paper, it's far from being able to ignite paper like my Arctic though.

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well i kinda don't give much care about burning properties
it's the beam what makes a good beam show WOaaawWw btw ive a 800MW laser MEGA cool ( sigh )

Benm said:

I dont think there is any means to tell power without a LPM. The only method would be comparison to a laser of known power at the same wavelength - at least you can see if its brighter or not.

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I would disagree with that from 0-150mW

I have found that I can accurately 'guess' 405, 473,
532, and 650.

It got to the point where id be guessing while setting
the focus on 405 modules prepping them for testing on my LPM.

Recently ive been working with a bunch of 473nm units,
and sure enough I was ball-parking after the first few tested.

The 445's seem to bother my eyes even at lower outputs,
and seeing most 445's I work with are no less than 400mW
there is know way to guess. Though judging by the beam
brightness with the beam terminating in another room, im
getting the feel for them too.

Keep in mind, ive assembled and tested in the hundreds
with a calibrated LPM at hand...

It all comes back to having a power meter in the end.

There is no such thing as accurately guessing things: either you take an accurate measurement, or you guess.

I have nothing against 'guestimating' values, but they are nothing more than (to some degree educated) guesses

And in the end, the power you hold is ~equal to the power your LPM reads. (good song!!)
At class IV power, you can't trust your eyes as a power meter.

HMike

My labby 445 @ 1000mA with Axiz AR glass lens burns the paint right off the wall at 7 meters when focused tight. This only takes a few seconds.

I can also burn a pin hole through 1/2" pine in a few minutes.

My guesstimate of optical power: bloody dangerous.

How many time does it take to burn a hole through an orange BIC pen at 10' ? If we can find an object that it easy to find everywhere in the world we could have at least a way to compare. CD cases doesn't apply, there are lots of qualities, colors, even for the same distributor.

Benm said:

I dont think there is any means to tell power without a LPM. The only method would be comparison to a laser of known power at the same wavelength - at least you can see if its brighter or not.

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There would be another problem... as you know diodes vary a bit according their wavelength. The difference is noticable especially at WL near UV (like 405nm) or at the longer WL (635nm). The weaker the lasers, the bigger is the noticable different between a few nm to or away from the visibility peak.

Not everybody has a spectrometer like LED_MUSEUM (why aren´t there DIY spectrometers around?)

Pilgor said:

It needs to be a specific type of paper to actually catch on fire and not just burn.

As for having shorter reach, hmmm how would you measure that?

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weeba2kv said:

My 445 laser focused can burn trough white paper ( not set it on fire ) and it's not more than 1 watt

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My 1.2W 445nm can set paper on fire in 15 seconds: http://laserpointerforums.com/f48/1-2w-diy-445nm-spyder-ii-host-53696.html

Comparing burning times really isn't ideal for determining power. It all depends on the focus.

RA_pierce said:

A couple 445nm diodes I used varied by ~125mW at the same current with the same lens.

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And 8% accuracy is enough to tell whether it's still outputting close to 1.5W. I didn't say it was a perfect substitute for a power meter. But it's the best you can do without one. If the diode current is, say, 1.5A and the beam pattern is nominal, it's unlikely the output is anything below 1.2W.

weeba2kv said:

i don't belive that ( video plz )

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Sorry just seen your post, I'll do one when I get home

Measuring Laser beam power by burning something or by
just by eye... is like checking wind speed by sticking a wet
finger in the air...

You will know approximately from which direction the wind is
coming from and if it is weak or strong... but will have no clue
as to the correct wind speed without the use of a calibrated
measuring device (anemometer) to get an accurate reading....

@ Cyparagon...
as a Laser Diode degrades the Laser beam power drops for the
same current... You would need to know that your LD has not
degraded before comparing it to any I/mW charts...
Not to mention the different lenses being used..


Jerry

I'll say it again, IT'S THE BEST YOU CAN DO WITHOUT A METER. It gives a ballpark figure. I also already mentioned beam pattern can be an indication of the degradation. Lens statistics are also readily available.

Cyparagon said:

I'll say it again, IT'S THE BEST YOU CAN DO WITHOUT A METER. It gives a ballpark figure. I also already mentioned beam pattern can be an indication of the degradation. Lens statistics are also readily available.

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No need to scream....
I apologize if my post offended/upset you...

Jerry

I wonder if it would be possible to do something like focus the beam out to a VERY specific width at its widest point and then use an IR thermometer to measure how many degrees above room temperature it is able to heat said object. Perhaps a quarter sharpied black?

If you are wanting to go by burning things, I think you are going the wrong direction. A more reliable direction would be to see how wide you can unfocus the beam before there is no interaction. EX: How wide is the beam when it is no longer able to mark a black CD case. At tight focus the dot is too small to accurately make them even and things happen to fast to accurately measure anything other than seat of the pants.
I did that when comparing my arctic to my DIY. Beam wise, outdoors it is VERY hard to differentiate them. I thought perhaps the arctic was the brighter of the two. Then I defocused my DIY to the same width as the arctic and went to town on some CD cases. The arctic takes about 5 seconds to burn through, the DIY about half of the time. Even that is a bad measure though, I should have went wider to get a more accurate reading BUT I didnt want to mess with the focus on the arctic.