Running the whole block of 445's!

[3ricj]

BTW, I don't know if anyone here has contact with the folks who run this site: Laser Pointer Safety - Laser safety calculations

The calculations on that page are wrong. Specifically:

Most of the math above is wrong. See page 13 of the AC70-1 document here for the correct calculations (tip: it takes into account the energy DENSITY in W/cm2, not just mw).
http://rgl.faa.gov/Regulatory_and_G...oryCircular.nsf/list/AC 70-1/$FILE/AC70-1.pdf

All of this talk of "ED50" is complete garbage, and for the purposes of FAA regulations should be ignored.

Also this table is wrong:

Green 532 nm, VCF = 0.88016. Essentially all green laser pointers and handhelds currently (2011) sold to consumers.
Red 633 nm, VCF = 0.23825. Use this for most red diodes and helium-neon lasers. A 635 nm diode will have a slightly lower VCF (0.2202). If a laser is known to be red, but the exact type or wavelength is not known use a value of 0.23825.
Blue 445 nm, VCF = 0.03050. This is a very popular blue. The original source is diodes taken from Casio “Green Slim” laser projectors. This type of diode is used in the Wicked Lasers Spyder III Arctic and similar blue handhelds.

The correct values are:

532 nm = 0.9524 VCF
633 nm = 0.2653 VCF
445 nm = 0.0380 VCF

See page 19 in AC70-1 to confirm this. It looks like LPS averaged between the two values in the table. The standards state: "If the laser’s wavelength falls between two table entries, use the more conservative (larger) value of the two resulting VCFs."

Hope this helps,
-3ric

 

[Benm]

Pointing an array like that straight up would pose no danger to aircraft passing over a cruise altitude - by the time you are 10 km up in the air, the beam is something like 20x100 meters in diameter and would be safe to look at. Distraction obviously is a relative thing, but it would pose no health hazard at all.

This would be very different if you were close to an airport or in an approach lane where aircraft pass at lower altitudes. Since you are poiting it straight up there is no chance of blinding pilots however, unless they were taking a nosedive for the ground to begin with.

As for the cooling requirements: running the entire array at 1 amp per diode would produce in the order of 100 watts of heat. Water cooling may be the best option to keep the temperature down, but sandwiching the array between two high end CPU coolers would suffice if you can ensure good thermal contact.

 

[Gryphon]

Thats the first thing i did with my projector when i got it, pulled the block free and aimed all those photons into the night sky He heats up mighty fast doing that though.....

 

[NickD070]

In fact, I think we agree completely. Our laser was not a "demonstration laser"; it had no galvos, was not a "laser pointer", was a fixed beam going straight up in a fixed configuration and was for science. If we *could* have done an FDA process we would have, but due to the nature of this laser testing we are not eligible. On the blog post I linked to above, it specifically states:

"Note that if the laser operations are for entertainment as opposed to scientific use, the Food and Drug Administration must be notified in addition to the FAA."

Part of this process (as explained in the blog entry) is to figure out what the hazard area is. Working with the FAA control towers in conjunction with spotters on the ground enables us to perform these sorts of experiments while not posing a hazard to aircraft. We received a letter of non-objection from the FAA based on our proposed laser operations. In addition, we operated our laser without incident under our SOP. This involved coordination with the control tower and our laser safety officer.

There are lots of ways to do this wrong. We did our best to ensure that we did it the right way.

Well don't get me wrong I think that whole operation was done very professionally and properly. I was just answering T_Warne's question.
It's just with the FDA/CDRH's re-interpretation of SLA laser regulations, they pretty much are trying to force every >5mw laser to be grouped into a category that they can regulate the use/sale of.

But again, that was a great/safe setup and demonstration you had there. Good pictures too.

 

[Flaminpyro]

Was this done at burning man ?

Where is Toorcamp ?

I can see now by there being trees in one of the pictures that this was not at Burning Man.