mhakali
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then what makes a good IR filter? I notice the price varies much.
You should look at how much of the IR light the filter blocks. If you can block over 98% of the IR output over 800nm you do have a good IR filter.
On both filters on Alibaba you can see:
700~1000nm Tmax. ≤2%, Tave<1%
1000~1100nm Tmax≤4%
This is an excellent block rate. Maxmum throughput for IR in this range is 2% at 808nm and 4% at 1064nm.
The lower light throughput at these wavelengths the better.
You can also see the following figures:
420~620 nm Tmin≥88%, Tave≥90%
This means that this IR filter will reduce your green output with about 10%. So if you measure 200mW output with the IR filter, you can be fairly confident that it performs around 222mW without IR filter.
John7788 said:Will one or two IR filter be enough for all my lasers?
The reason why you want to use 2 IR filters is to test the accuracy of the IR filters themselves. As said above those IR filters will shave off 10% of your green output.
Lets say you once again measure 200mW with an IR filter. That means in theory that it should output 222mW green without the IR filter.
To test this you put another IR filter in front of the first. Now you should see a drop from 200mW to 180mW. As the IR filter shaves off 10%. If you see a larger drop than this, lets say 200 -> 150mW, you know the IR filter also eats up 25% green 532nm.
So from these figures you can calculate that the laser performs 266mW green without the IR filter.
John7788 said:A IR filter for yellow will fit for green, red,or violet laser?
IR filters block IR wavelengths. As such they should be applicable to All lasers creating it's emission via DPSS or similar technologies, where you usually use a 808nm IR pump diode in the back which then gets processed into different wavelenghts.
It is because of this you actually get the stray readings. A 100mW laser which leaks a lot of this "processing" light may only do 20mW of green. While another may do 80mW green. Both will read 100mW on the LPM.
This is why you want an IR filter for testing.
A fair assumption is around 15-30% worth of IR on the types of lasers you resell. The one I reviewed was about 50mW stable green, with 65mW inclusive IR. So about 23% IR.
Hope this clarifies some stuff!