Green Laser Eye Protection In The Wild

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This fantastic article was submitted earlier today by our great friend and brother, MartyP!

If for any reason you think you might be the subject of a laser attack, this is important information to have.

Thanks again Marty!

-Tex


By HERSCHEL SMITH

We’ve all seen that Antifa/BLM has blinded the border patrol agents sent to protect federal property in Portland. Andy Ngo has been directly attacked with a green laser, and he points out that the threat is expanding (via WiscoDave).
After #antifa were dispersed by police following the attack on the East Precinct, they tried to blind a woman at her home with lasers and attacked her.
This is remarkable video. The communists have found an effective weapon short of using firearms. So the question is necessarily posed, what can you do about this threat? The answer isn’t easy or clear short of deadly force (and this in fact may be the best option, but it may be difficult to effect that end for reasons we’ll discuss below).

Most of this post will be the result of studying I did on laser safety for a very specific examination, and it has been a long time since that study, so some of it will be incomplete, and some may be inaccurate. As readers stumble on better data, knowledge and analysis, feel free to post it here. I make no claims as to the complete accuracy of everything in this post. I offer it up as a starting point. I can follow it up with more information, but I’ll need reader assistance to do that.

To begin with, you need to understand the concept of optical density (OD) calculations. According the ANSI Z136.1-2007, a class IIIa laser is visible and limited to 1-5 mW. Nothing more powerful can be sold in the U.S. without special licensing (if the communists in Portland are using lasers more powerful than 5 mW, then this poses a special and expanded problem, even worse than I am assuming).

I could post calculations of OD, but it’s best simply to watch this short video if you want to pursue it (for folks who have an aversion to math, here is an online application that will do these OD calculations for you). Now listen carefully. He credits the blink, or aversion, reflex in his calculations. The blink reflex is 0.25 seconds. The blink reflex is also credited in laser protection eyewear for green light lasers (532 nM).
The ANSI Z136.1 Standard bases the “blink reflex” MPE on an exposure on 0.25 second exposure. This yields an MPE of 2.5 mW/cm2. When this irradiance is spread over a “worst case” 7mm pupil opening (0.4 cm2), the total power entering the eye can be then computed as follows: Power = (2.5 mW/cm2) x (0.4 cm2) = 1.0 mW. This suggests that laser pointer type devices might be limited to an output of 1 mW (Class II).

In some darkly lit environments, and at some wavelengths, a 1 mW pointer power is perhaps an option, but in rooms with a high ambient light level and if operation is at the longer 670 nm wavelength, 1 mW is just marginal for visibility and, therefore, 3-5 mW is generally required for better visibility. Note that if the exposure is raised to a maximum of 5 mW (Class IIIA), then an eye filter with an optical density of 0.7 would be required for protection in the event of an intrabeam exposure of 0.25 seconds. This suggests that caution is needed when the pointer emits near the 5 mW power level!
When they speak of optical density, remember that lasers emit radiation, and just like radiation emitted from the nucleus of an atom (laser wavelengths are emitted from the electron shell), it is attenuated exponentially (or in this case, log base 10 will describe the effectiveness of eyewear). You don’t stop it – you just attenuate it.

OD1+ = 10% gets through

OD2+ = 1% gets through

OD3+ = .1% gets through

OD4+ = ..01% gets through

This video shows you how poor the cheap eye protection purchased from EBay and Amazon might behave.


It’s up to you. You can opt for the cheaper stuff being marketed to military and law enforcement, or you can purchase ANSI Z136.1 rated and tested eye protection marketed for industrial laser safety use. Either way, remember that in all cases of which I’m aware, no eye protection can enable you to stare directly into a laser nonstop with no aversion response (or maybe a better way of saying it is that the OD calculations would show an extreme level of protection that no one sells to be able to look at a laser nonstop). All eye protection design assumes the blink reflex of 0.25 seconds.

Also, it may be that wearing this eye protection isn’t conducive to good vision at night and in a threatening environment where you need all of your faculties and senses. In the case Andy Ngo links above, the lady under threat has perhaps dozens of green light lasers pointed at her, little time to respond, and the communists are gleefully taking video of the suffering of the innocent.

The best bet in case of threat from visible lasers is to not be around those who would threaten you. If you do happen to be in proximity of those threats, then remember that looking into an array of lasers in order to try to effect self defense isn’t advised, even if you are wearing eye protection. Blink. Be averse to this threat. Get away from it.

This is a serious threat folks. Being tactically careless or thoughtless in dealing with the threat isn’t recommended.


Original Here

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