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RPL laser "dual beam" issue = wasted power demo






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SenKat

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Re: RPL laser "dual beam" issue = wasted power dem

How many of these lasers have you owned, in order to draw the conclusion that ALL RPL's do that ? There is no scientific basis for that statement if you have only experimented with one laser. You should really retitle your summary from, "....the waste of power on all RPL type laser modules" to something alittle more like, "This is what MINE does"
 
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Oct 12, 2007
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285
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28
Re: RPL laser "dual beam" issue = wasted power dem

I have had three and they are IDENTICAL. It's "behavior by design".

I say by design because it's intentionally hidden by the endcap with the tiny hole.

CNI hides their beam artifacts by gluing a tiny piece of metal to the collimator on the inside. ::) (CNI pointers) But I will add that they do NOT have two beams.

The laser in the video is repaired and its previous module did the same thing. The laser "repair" consisted of swapping a laser module.

It's possible that this alignment is to ensure better stability. I've discussed this in fair detail with Jack over a year ago.

The (real) point of this video is not to bash the product just to make everyone aware that there is room for improvement. If the beams were combined downstream of the OC mirror, a significant gain in overall output could be had with no impact on stability and beam quality (if done right).
 

koti

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Re: RPL laser "dual beam" issue = wasted power dem

Well my RPL-225 has 1 single beam when I unscrew the top like You do on the film.
Maybe the funky looking silver ones are screwed up? ;)
 
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Re: RPL laser "dual beam" issue = wasted power dem

SOrry I haven't had time to write a full response to your PM Nordhavn.

Greg, this occurrence happens with my RPL too, and I have been in touch with the manufacturer. A bit gets lost in translation from the engineer to the sales rep, to english, but I was told that ALL RPL units will have this oddity.

At the moment... I'm still hoping the sales rep will have the engineer explain why.
 
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Re: RPL laser "dual beam" issue = wasted power dem

Nordhavn said:
The (real) point of this video is not to bash the product just to make everyone aware that there is room for improvement.  If the beams were combined downstream of the OC mirror, a significant gain in overall output could be had with no impact on stability and beam quality (if done right).  

Unfortunately, unless each beam is well polarized, that's gunna be impossible.


An in fact, I'm wondering if this is because of polarization. These lasers are supposedly linearly polarized >100:1, so perhaps a poorly thought out brewster setup is to blame for this?  :-?


EDIT: On second thought, I don't see how a brewster window would explain any of this. HOWEVER, if the light is indeed polarized, perhaps a birefringent coating is to blame? That would make perfect sense... in its own way...
 
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SenKat

Guest
Re: RPL laser "dual beam" issue = wasted power dem

Nordhavn - my apologies for my error ! That is very interesting, and it got me to thinking HARD. I did a repair job on a PPL about 7 months ago for a CPF member....it had two beams as well - I had assumed I failed in my repair attempts, and that the laser was simply unrepairable, and there was a defective item in the optical train that created that issue. The beams were IDENTICAL to the video you showed - I cannot believe my brain did not kick in until I had posted what I did. So, this is kinda disturbing - to say the least !
 
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SenKat

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Re: RPL laser "dual beam" issue = wasted power dem

FWIW - I posted mostly the same thing in my comments on your video
 

koti

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Re: RPL laser "dual beam" issue = wasted power dem

So how would You explain that my RPL-225 has a single beam and a single large blob on the wall ? I mean is that good or bad or what ?
 
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SenKat

Guest
Re: RPL laser "dual beam" issue = wasted power dem

Read closely :) There is a small meatllic disc inside the optical train taht blocks that second beam from coming out on most RPL &PPL's
 
Joined
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Re: RPL laser "dual beam" issue = wasted power dem

koti said:
Well my RPL-225 has 1 single beam when I unscrew the top like You do on the film.
Maybe the funky looking silver ones are screwed up? ;)

Well mine is silver because it gets used like a tool, the finish was getting bad (worn through on the edges) so I removed all the black paint. Besides that it's no different than your typical RPL.

Most RPL lasers will not show dual beams if the barrel is unscrewed because the final endpiece with a tiny hole drilled serves the purpose to hide this characteristic. This is important because the purpose of a DPSS laser is to produce green obviously. Discarding nearly half is not good. If you bought a Porsche 911 twin turbo knowing the engine could put out 900bhp but really put out 500 in real life wouldn't you be upset?

I'm thinking of just tearing this one completely down as it's obvious in the video that it's not of very decent quality even when run on lower power levels. I've been running the shit out of it too on levels as high as 8 until the battery dies with no noticeable performance trends. That makes me think about stripping the guts and turning this into a 2+ WATT 808 nM laser searchlight. With a variable focus optical train it would make for some nice night vision assist work. ;D Well focused it could be used to "tell" others where to go. (and that's all I'll say about that!)

If the expander is removed the pair of beams is still there with lower divergence on each and much narrower angle. With as many of these lasers in the intermediate to advanced hobbyist sector I cannot believe no one else has found or made mention of this. I guess it could be the fact that it cost over a grand and they don't want to tear it apart. ;D

pseudonomen137 said:
[quote author=Nordhavn link=1193076198/0#2 date=1193078313]
HOWEVER, if the light is indeed polarized, perhaps a birefringent coating is to blame? That would make perfect sense... in its own way...

Yeah but nearly 50% of all green? I need to run this through my profiler but the power is too high for the attentuators I have. Will the bare module run at very low power (just over pump threshold) from a bench supply?

Oh and let me add the reason why the laser was sent back for repair was due to mechanical (shock) damage. It was exposed to high SPL of a large subwoofer array which changed its divergence. (not a matter of adjusting the collimator) Since the Vanadate/KTP elements were previously disassembled about this time last year and reset with epoxy I decided to get the unit repaired. Also the little dial on the switch with the numbers 0-9 had fallen off just exposing the switch (that was fixed by jamming a #0 reed and prince bit heated to 300C into the plastic.) I knew something was up when there was a new switch module installed in the end cap. There was also a new label on the inside with a new SN and (most importantly) ending in -250mW. I'm told all these modules are 250mW spec'd; some do better than others and that's how your seller bins and prices them accordingly. It's like buying CPU's in the old days where you could buy a pretested AXIA TBird 1400 doing 1700 for about $100 more and have a guaranteed stable chip at a speed that didn't commercially exist. (Not all those were 100% stable as well but you get the point!)

The original laser had the dual beams as does this one. I had PPL's that were returned so I never got a chance to see if they had this issue. They did not have near the divergence of the RPL however.
 
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Re: RPL laser "dual beam" issue = wasted power dem

If you do tear it down, photograph (hi rez) the beam path optics and their arrangement. I have a sneaky suspicion that the artifact is created because of a need to prevent reflections back down the beam path toward the pump diode.
 
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Re: RPL laser "dual beam" issue = wasted power dem

FrothyChimp said:
If you do tear it down, photograph (hi rez) the beam path optics and their arrangement. I have a sneaky suspicion that the artifact is created because of a need to prevent reflections back down the beam path toward the pump diode.

Yes I plan on doing that. I have a decent SLR (5D) and lenses.

But it will have to wait for a while as this is the only portable source of 532 I have to use on the water and I need it for a while!

Just to recap; this is a normally functioning laser. But it's the mad part about the scientist or wannabe scientist that yells out MORE MORE MORE!

http://www.youtube.com/watch?v=sF_iHXPq1ds&

Unlike wanting and wishing when you see MORE you want it...yesterday! ;D
 

Milos

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Re: RPL laser "dual beam" issue = wasted power dem

SenKat said:
Read closely :) There is a small meatllic disc inside the optical train taht blocks that second beam from coming out on most RPL &PPL's

So this means there is a second beam with same or almost the same power hitting the metal body of RPL, thus directly heating it up. Thats crazy. What am I missing here?
How the hell other models (CNI) of 200+mW deal with only single beam and still have same heating problems as RPL which has 2 beams one of which is completely transformed to heat inside.
And do RPLs than produce twice the power (inside) than Aries or Hercules who don't produce 2 beams. Or do they?

I'm confused.
 

Gazoo

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Jun 9, 2007
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Re: RPL laser "dual beam" issue = wasted power dem

I admit I am confused as hell...lol. The double beam doesn't make any sense to me a raises a lot of questions.
 

LarryQ

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Re: RPL laser "dual beam" issue = wasted power dem

This is really interesting!!!!

Lots of things to ponder!!!

LarryQ
 




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