Using green LED to compare laserpower.

[Blord]

I have a 50mW green pointer who has been checked by John of Priceangels as true 50-70mW power. And I have a much brighter laserpen of unknown power.
If I lase the pointer on a green LED a current will flow thru the diode and with a uA DMM I can read the output. The 50mW pointer gives 70uA current and the unknown green gives 220uA.

Can I conclude the powerrange is triple of the 50-70mW thus 150-210mW ?
Or are the output not lineair.

 

[MarioMaster]

It's an unreliable method of trying to measure laser power - angle, the LED itself, IR leakage and other factors all screw up the linearity.

 

[JLSE]

You may be able to get a rough idea, but at minimum you
should test with an IR filter in between the lasers and the led.

At best it would be a ballpark comparison.

 

[udanis]

Or you could spend $100 and get an LPM :beer:

 

[Blord]

That thing is never available. I have been clicking every day.

I want a cheap way to compare the green lasers. It is alot brighter than the 50mW Newwish from PA. Sometimes it is almost close to the SKY-Laser 200mW in brightness. I feel definitely a sting when it hits my skin.

left : SKY-laser 200mW but drlava tested it 250mW average
middle : NewWish pen 30mW from dealExtreme
right : NewWish pen 50mW from priceangel

 

[BKarim]

maybe you can compare the rotation speeds of a radiometer ?

 

[Blord]

I don't have a radiometer. I have seen one in college many years ago.
And you need a device to measure the rotation speed. Kinda complicated.

 

[BKarim]

no you can film the radiometer and do the counting at slow motion.
but i don't know if the rotation speed is linearly linked to beam power.

anyway you must buy one or more radiometers. they are very funny.
(not all are correctly equilibrated, you should test them before buying)

 

[Cyparagon]

No, it's not linear. Also, the laser can possibly vaporize some of the coating and compromise the vacuum. It would also be effected by ambient light. Every bulb is different. It would probably be able to tell which laser is more powerful, but not by how much.