How to detect/measure IR

Most of the cheap 532nm lasers around come without an IR filter. It isn´t only dangerous because standard 532nm safety goggles can´t protect you from this, we also want to know if and how much of IR power is in our lasers!


Here are some ways I know about...

To detect IR in the output of your laser, put on the safety goggles and look at the dot. If there is another light arounf the proper green dot, looks like a plasma for me, the laser is non IR-filtered.

Another way to detect IR is to buy a IR detection card like JETLASERS has on their site Laser IR Detection Card - Jetlasers.org
I haven´t test this yet, but I´ll update this thread as soon as I get one.


To measure the IR power you need a Laserpowermeter. There are two options according measuring the IR with a LPM.
The first is to put an IR filter from a old cam or whencever you find one between your LPM and the laser. It is important to know/calculate how much light pass the IR filter and how much gets reflected back.
The second option is to measure the IR of your laser with a 532nm safety goggle. Put the safety goggle between the laser and the LPM and measure how many mW go through the goggles. Then measure the output without the goggle in front of the laser and subtract the measurement from the second output to know how much IR is in your green laser.

Notice: You get the most exact measurement with combining the IR and goggle method due to the reasin that a few mW of green (depend on the goggle) will go through the safety goggles.


Other methods/improvements are welcome :beer:

Cant i measure mws or ir with my eye through goggles? What about holding a webcam/iphone through the savety goggles?
I dont need exact mw numbers but guessing can do?

When I was doing the "fun test" of the DIY Digital Thermal LPM I used a IR filter from scontony. It was on one of the cheap overspec pointers that most estimate abt 30-40mw.
The DIY unit , with no standard, is really no more than a good comparator.
It does work well for % comparisons of power output and of loss. I had a reading of 60% IR on a 5mw 532nm el cheapo pointer.
I believe it was HIMNL9 that suggested using 2 filters and taking 2 readings. The second reading with the 2nd IR filter will show the actual 532nm loss from the filter. By doing this you can subtract the 2 readings and account for the filter loss, reflectivity and so on giving you a pretty accurate % of the IR produced.
Pretty slick idea. Now I need to do it again when I have the DIY unit back out with the target on it.

borgqueenx said:

Cant i measure mws or ir with my eye through goggles? What about holding a webcam/iphone through the savety goggles?
I dont need exact mw numbers but guessing can do?

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I do hope your kidding. The eyeball mk1 is one of the most inaccurate power meters around.. Not only does it have a very low damage threshold and replacement parts are impossible to acquire, but it's output is highly subjective and no two sets will agree with each other.

Not to mention the fact that it's hard to 'measure' what you can't see with it.. namely IR...

qumefox said:

I do hope your kidding. The eyeball mk1 is one of the most inaccurate power meters around.. Not only does it have a very low damage threshold and replacement parts are impossible to acquire, but it's output is highly subjective and no two sets will agree with each other.

Not to mention the fact that it's hard to 'measure' what you can't see with it.. namely IR...

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i am not talking about power meters. i dont follow you.
wont it help to use a iphone? it can see IR on a green laser i received from priceangels with it...(a 50mw laser....with no green at all)

borgqueenx said:

i am not talking about power meters. i dont follow you.
wont it help to use a iphone? it can see IR on a green laser i received from priceangels with it...(a 50mw laser....with no green at all)

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If your not talking about measuring power, then why are you posting in this thread discussing measuring laser power? :thinking:

If you want to measure laser power, you need a LPM.. Plain and simple. Eyeballs won't work. Camera's wont work. All that will get you is laser A is brighter/dimmer than laser B. You won't have any clue what power either really is.

Using a camera will only tell you that IR is present. not how much. There is no way to accurately guess. There are way too many unknown variables.

But brighter means more mw...right? I dont need a so accurate measurement.

Yep, brighter equals more power.. However how can you tell if your looking at 1mW or 100mW?

qumefox said:

Yep, brighter equals more power.. However how can you tell if your looking at 1mW or 100mW?

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I dont know how ir works...if its same as green (terms of brightness) i can make a guess how much mw it is...so the circle around the dot represents IR...so if i can barely see it it is <5mw? I hope i dont see anything at all

You can easily put a pair of safety goggles in front of a camera to see if the DPSS laser is IR filtered, however most cheap goggles don't filter out all of the green, still leaving about 1-5mW which may cover up the IR. Instead, I like to use a diffraction grating and then have a camera look at the output after the grating with goggles in front of the camera. The diffraction grating will separate the IR from the 532nm light.

laser_freak said:

You can easily put a pair of safety goggles in front of a camera to see if the DPSS laser is IR filtered, however most cheap goggles don't filter out all of the green, still leaving about 1-5mW which may cover up the IR. Instead, I like to use a diffraction grating and then have a camera look at the output after the grating with goggles in front of the camera. The diffraction grating will separate the IR from the 532nm light.

Click to expand...

I never heard about this before! But it should work YES!

Thank you +1