[ATMoB-discuss] Green Lasers?

[BERNARD KOSICKI]

With all the discussions about Green Lasers (which I take the blame for starting), I thought a bit of quantitative input would help.  I found a good discussion of laser pointer safety here from a Rockwell group

http://www.rli.com/resources/pointer.asp

The authors define reaction to several levels of a typical 5mW pointer laser exposure:

Bioeffect
                   Condition
                                                   MPE Level *
                   (W/cm2 )
                                                   Nominal Hazard Zone
                   (feet)
                                                                                         BLINK REFLEX
                                                         2.6 x 10-3
                                                         51
                                                                                           FLASH-BLINDNESS/AFTERIMAGE
                                                         100 x 10-6
                                                         262
                                                                                           GLARE
                                                         5 x 10-6
                                                         1,171
                                                                                           "NO EFFECT"
                                                         50 x 10-9
                                                         11,707



If we assume a 20mW laser (which is relatively commonly used according to the replies to this topic), and assume a pilot flying at 5km (3.25 miles) is hit directly in the eye, and a 1mr beam divergance, then the average power level at the pilot's eye is about 10E-7 W/cm2.

This dose is about 2x above the NO EFFECT hazard MPE, but about 500x below the GLARE MPE.  Neither of these levels would cause permanent damage, but GLARE could affect vision-related functions temporarily (see the web site).

This paper also discusses another type of hazard that is not officially recognized- that is, "OUTRAGE":

"n addition to the above light induced factors that could certainly effect perception during vision-critical activities, the authors also believe there to be yet another factor . This is the case of an individual exposed and having the perception for a significant potential harm. In some cases, this can lead to reactions based on factors other that retinal damage or flashblindness. This would be considered as the Concerns of a Perceived Hazard (CPH). This is often referred to as "outrage". There is growing evidence that adverse physical effects can be deemed by some who are exposed by what is usually considered as a non-harmful beam exposure. In this case, the exposed person feels "victimized". In this case, the person becomes "outraged" at the perception of being harmed and is convinced that harm has been done."

This might be the greatest hazard to distant aircraft.

The authors also warn of the dangers of removing the 1064 filters from any diode pumped lasers (these are supposed to be permanently installed by the manufacturer, but are not in many imported lasers).  Many imported lasers are therefore not "certified", ie, don't comply with construction or safety warnings that they are supposed to have.

The authors also show a database of about 20 "incidents" which is pretty interesting (one of these is a pilot hit).  They also discuss various government actions (>Class 2 outlawed in UK).

My opinion is that IIIB lasers can be used safely if the user is  careful.  The biggest danger of permanent damage is to those on the ground near the laser.  Don't fool around with the filters and optics of your laser, and try to buy one that is Certified.

Bernie Kosicki 

Virginia Renehan <vrenehan at gis.net> wrote: Paul,
I posted a response earlier today.  Read the March '05 Newsletter, page 4 
for the club's green laser policy.
~Virginia

----- Original Message ----- 
From: 
To: ; 
Sent: Wednesday, March 07, 2007 10:25 PM
Subject: RE: Re: [ATMoB-discuss] Green Lasers?


> At this point, we need a response from the Executive Board or the 
> Clubhouse committee.
>
> The FAA has concluded that a laser beam directed staight into the cockpit 
> at a critical point in operations such as landing "could" result in a 
> crash. I don't think that is unreasonable considering the NJ guy that was 
> targeting landing planes at Newark. He tried to get off the hook by 
> claiming that his kids were doing it without his knowledge.
>
> So, I my mind, it is not out of the realm of possibility.
> Better safe than sorry, fines begin at $10,000.
>
> Paul
> _______________________________________________
> ATMoB-discuss mailing list
> ATMoB-discuss at atmob.org
> http://lists.atmob.org/mailman/listinfo/atmob-discuss
> 


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