ok
 
Thank you very much for this explanation very clear now I understand
 
but this is not really necessary to have a filter or better to have one?
 
Thank you for all your information that I'm pretty boring I always ask a question.
 
Thank you for everything.
		
		
	 
 It's better to have an 
Infrared filter, so you know that 
all of the laser light (power) is just 
Green light.  For powers less than 50mW, you don't really 
need an 
IR filter.  For powers greater than 50mW, you want an IR filter because of the the higher quantity of IR light.  
A 100mW 
Green without 
IR filter can have as much as 25mW of "invisible laser radiation" that can damage your vision.
Example: Last year, I got one of my first +100mW 
Green lasers, and it did not have an 
IR filter.  I was using 
these safety glasses while ignighting matches and burning wood around the house, but the safety glasses only protect against 
Green, and I noticed that my eyes were actually aching after only a few seconds of looking at the point of "burning".
I then ordered 
these safety glasses that protect against 
IR and Green, and my eyes no longer hurt when burning with my non-
IR filtered 
Green lasers.
So, either purchase a laser with an 
IR filter, or purchase safety glasses with 
Green and 
IR protection. 
