Lasers?

[Diver Dennis]

Hmmmm. I wonder if these work underwater? Jeff would like one of these...

Capt. Drew F. Goettler, of the Air Force Research Laboratory' Directed Energy Directorate, demonstrates the Personnel Halting and Stimulation Response, or PHaSR, a non-lethal illumination technology developed by the laboratory's ScorpWorks team. The technology is the first man-portable, non-lethal deterrent weapon intended for protecting troops and controlling hostile crowds. The laser light used in the weapon temporarily impairs aggressors by illuminating or "dazzling" individuals, removing their ability to see the laser source. (AF photo)

 

[Cacia]

don't encourage him, he is mean enough topside. I think it is time he look for a peaceful avatar. Thanks for reminding me about my laser, i am packing it for my top secret mission this weekend.

I will be shallow, so I bet it works better with the red not filtered out. I forgot I had this.

 

[MSilvia]

I will be shallow, so I bet it works better with the red not filtered out. I forgot I had this.

It's not the depth that filters red, it's the distance the light has to travel through water. If you shine it at someone 30' away, they'll see the same red as if viewing a red surface light from 30 fsw.

 

[dherbman]

I will be shallow, so I bet it works better with the red not filtered out.

I've never considered you to be shallow.


Are there other components to the beam that would not be filtered out, but might be invisible?

 

[Reinoud]

Can anyone think of a good reason that a reliable underwater laser pointer couldn't be used for maintaining buddy contact in place of a can light on recreational dives in open water?

A primary light in DIR serves two purposes:

• as a communication device
• to illuminate things in the dark

I think a laser fails in both ways. If I am out of air and signal distress with my 18 W HID, the beam is much more visible than a tiny red dot.
Furthermore, either the laserbeam is not visible when nothing is in the way (which makes locating your buddy much harder), or the beam is visible, which means that the red dot will be a lot less visible. (people that have experience with laser projections know what I mean: above water you can only see a laserbeam in smoke, and then only when looking into the general direction where the light comes from).
So it is not a good communication device compared to a focused HID light.

And I think it is clear that a laser is not suited for illumination.

So it is obvious it can never replace a HID (not even in recreational diving). It does not add any functionality either in my opinion.
I've seen laserpointers marketed as pointing devices underwater, but I do not see any benefit over using my index finger ";-)
If it adds no functionality underwater in DIR, you leave stuff above water.

Playing with your cat seems the only usable a diver could do with a laser to me ";-)

 

[SeanQ]

www.wickedlasers.com

Rule 6 compliant!

 

[dherbman]

Tempting.

 

[M_Bipartitus]

Aside, not to get away from the topic but...

Don't count on it. The lasers sold as laster pointers are *supposed* to be 3a or lower, but I have seen several gas station/truck stops selling higher rated ones as laster pointers. The laser safety officer where I worked would find these regularly and bring them in as examples on how regulations don't protect you, responsibility does.

True, I was obligated to test many laser pointers last year for that reason. Specifically the green laser pointers are most likely to be under-rated. (Ironic as the same power of green light is more easily seen by the eye than red.... no need for it to be more powerful) Still I would argue that there is very little chance of these slightly overpowered lasers doing much damage either as the regulations have a fair amount of over-protection built into the maximum exposure limits (just as a diving NDL is not the consensus limit at which point DCS is likely)

 

[M_Bipartitus]

Are there other components to the beam that would not be filtered out, but might be invisible?

Most red laser pointers are diode-based lasers, which results in them having only one color component. Many green laser pointers are frequency doubled from IR light. From my experience less than .1% of the light that exits the laser pointer is IR light, and like red light it tends not to propagate long distances in water.

 

[kidspot]

So when used in clear water (tropical conditions) are there enough suspended particles to leave a "beam" of red (or green or blue etc..) in the water column, or do you simply get a beam as you would in air? If it leaves a beam in the water it would be a good signalling device and be much better than an HID which even with a 21 Watt gets washed out in the day time over here. My 10 watt cannot even be seen most of the time during the day. The 21watt HID's that I've seen only leave a spot on the "ground", but still no beam in the water column, unless it's a murky day of diving.