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No access to any LPM owner; what's the most accurate and easiest to make DIY LPM?

Sepehr

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Hi guys,
Thanks for this amazing forum, it has lots of useful information from pros and experts and I really like the color theme too.
I'm living in Iran and I couldn't find a single LPM owner whom I could ask for measuring my laser power output. I have a cheap red 650nm and <5mW (if the label is correct) LASER pointer and I'm curious to know if it's 5 mW or more or at least find the range of its output. What's the best approach to measure its output without using professional instruments and equipment? Like using Arduino and electronics parts.

The device which I'm talking about has also UV LED and flashlight, similar to one of these.

Is it possible to guess its range by looking at pictures of the laser dot on surfaces taken in different environments?

I know the following sentences may annoy many users since it has been asked so many times. I accidentally reflected the laser dot off my monitor's glossy black bezel into my left eye. I don't feel any serious problems in my visionary but it feels better to know what was the real power output for the sake of piece of mind! So this is one of the reasons for my curiosity ;)

Thanks.
 



lasersbee

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Sepehr

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Thanks, Jerry. I'm very honored to have a reply from a well-experienced veteran user like yourself. Oh, I really didn't know that you guys have such a nice section in your Forum! Now I am going to introduce myself in the Welcome section ;)
You're right. I actually did some researches on the Forum and came across some interesting Threads, but thought it might be better to ask some users' opinions and their experiences.

EDIT: Here is my greetings post in the Welcome section. Hope you'll like! :)
 
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CynicalBrad

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Those little Keychain pointers tend to use a chip style laser diode and usually don't even emit the 5mW the generic sticker says. I figure some of them might emit more but they don't even have a proper diode in them and if they were made to emit more, the lack of thermal mass would fry them. That being said, at those power levels a meter is pretty much the only option to know for sure
 

BowtieGuy

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Hey Jerry, thanks for the link to that old DIY LPM thread, there's a lot of good ideas in those projects; I used this one myself "DIY Pre-Calibrated LPM under $100.00...." to make the power supply and switch for my Ophir 20C sensor.
I just mounted it all in a project box for a nice neat appearance.
 
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lasersbee

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Hey Jerry, thanks for the link to that old DIY LPM thread, there's a lot of good ideas in those projects; I used this one myself "DIY Pre-Calibrated LPM under $100.00...." to make the power supply and switch for my Ophir 20C sensor.
I just mounted it all in a project box for a nice neat appearance.
N/P..
Yeah... I put that out there when the OPHIR 20C
heads were still well under $100.
Ahh... the good old days....

Jerry
 
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Sepehr

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Those little Keychain pointers tend to use a chip style laser diode and usually don't even emit the 5mW the generic sticker says. I figure some of them might emit more but they don't even have a proper diode in them and if they were made to emit more, the lack of thermal mass would fry them. That being said, at those power levels a meter is pretty much the only option to know for sure
Thanks.

Yes, it's so poor in quality that it can't even hold the batteries inside of it. The rear cap easily opens up and all of the batteries will be thrown off.

Excuse me, I didn't understand what does it mean that they would be fried?

By the way, what a nice Avatar!
 

GSS

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Well iv'e got a swear jar going now towards a "laserbee":shhh: and if I start watching enough movie's like "Scarface" or ruin something with my awful soldering skills I should fill it up in no time.
 
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CynicalBrad

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Lasers produce a lot of heat for the output power. In most of our builds we have decent heatsinking to carry this heat away from the diode to protect it.
In most of these little cheap ones it is a blob of semiconductor material on a chip shoved in a slot in a plastic housing with a lens in front of it.
Thankfully they don't put out much power so heat is never an issue with them and they tend to work just fine as cat toys.
 

Sepehr

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Lasers produce a lot of heat for the output power. In most of our builds we have decent heatsinking to carry this heat away from the diode to protect it.
In most of these little cheap ones it is a blob of semiconductor material on a chip shoved in a slot in a plastic housing with a lens in front of it.
Thankfully they don't put out much power so heat is never an issue with them and they tend to work just fine as cat toys.
Thanks. :)
 

lasersbee

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Thankfully they don't put out much power so heat is never an issue with them and they tend to work just fine as cat toys.
Or with a 5V supply and a simple Laser Beam detector....
an Intrusion Detector...;)

Jerry
 

CynicalBrad

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Lol. Or have a few set up in a way that triggering one causes another mounted on a servo to wiggle and lead to the next. Cat crosses beam, wiggly laser turns on, stuff ensues, entertained cat :p
 

RedCowboy

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If I were to fire my 450nm lasers beam into an appropriately AR coated PBS cube, could I then read 1 of the split off beams then the other and simply add the two readings together?

Would a polarizing beam splitter be ok or should I use a different type of splitter, should I split the beam with a FS mirror rather than a PBS cube?

This is the meter I am thinking of using -

FREE SHIPPING New 5.2 Watt LaserBee? AX3 Laser Power Meter +Thermopile (Blue) | eBay
 

diachi

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If I were to fire my 450nm lasers beam into an appropriately AR coated PBS cube, could I then read 1 of the split off beams then the other and simply add the two readings together?

Would a polarizing beam splitter be ok or should I use a different type of splitter, should I split the beam with a FS mirror rather than a PBS cube?

This is the meter I am thinking of using -

FREE SHIPPING New 5.2 Watt LaserBee? AX3 Laser Power Meter +Thermopile (Blue) | eBay

You'd be better using a 50/50 beam splitter cube than a PBS IMO - easier to get an even split with a polarized beam. The PBS would be more suitable with a randomly polarized beam.

Other option is an ND filter or other partial reflect optic (as long as you know %R).
 

lasersbee

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As diachi stated.. you can use the split beam approach
with lasers that output more than an LPM's max rating
if you can determine the split ratio and any loss due to
power absorption of the splitting medium. Then add up the
2 values.

FYI...If you have that meter in your sights....:shhh:
buy it from our website... No eBay fees passed
on and less expensive.;)

Jerry
 




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