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FrozenGate by Avery

results: different lenses and red/br efficiency

Krutz

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Nov 21, 2007
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like the topic states, i did some tests with the lenses i have laying around.

testbed:
-40mw red 16x diode, 100mA, low output so heat and outputchanges dont interfere. uncollimated diode (with small heatsink) held in place, the tested lens moved in front of it with a "third hand", so it wasnt absolutely exactly parallel and centered. took care not to mess up the measure by carefully aligning it by eye though. uncollimated beam collimated by the tested lens to form a round, undistorted dot at 1 meter, putting a comparable dot-size on the sensor for each lens (more about that later)
-13mw 405nm pointer, with original lens left in. beam focussed to small dot onto the sensor, tested lens put close to the sensor. that way the dot-size is almost exactly the same (tiny) size for every lens. it makes sure that the lens-diameter doesnt interfere too, since my collimated output from the pointer is larger than the smaller tested lenses.
-"Die4Thing" powermeter. small, dynamic, quick and sensitive heatsensor. the reading moves about 1 mw up and down spontaneously (which is really really great for a thermal meter! quite accurate readings down to less than 5mw!!)

problem: the reading changes with dot-size on the sensor. the same laser, focussed to burn-mode, would read up to double the power! thats why i took care to always put a same-size-dot onto the sensor. but still, it could be wrong readings up to perhaps 10% because of this, beware! but the results are so obvious, that you come to conclusions still. even sttanger, this only happened with the red laser. the bluray didnt move the reading, no matter if 5mm dot or smallest focus possible. probably because of the low power, 13mw.

lenses:
1) the acryl uncoated bare lens from brass aixiz-modules
2) the acryl uncoated threaded lens from silver aixiz-modules, with "pinhole"
3) the acryl uncoated threaded lens from silver aixiz-modules, without "pinhole"
4) a common acryl AR-coated bare lens from a random dvd-pickup
5) a smaller acrylic AR-coated bare lens from the 16x dvd burner "Pioneer DVR-109"
6) a smaller acrylic AR-coated bare lens from the KES-300A ps3 BR sled

sizes:
1) 7mm x 2mm, focallength 5mm, same as inside 2) and 3)
2) 7mm x 2mm, inside a M11x0.5 threaded plastic holder, focallength 5mm (3mm to the holder, inside 2mm recessed)
3) 7mm x 2mm, inside a M11x0.5 threaded plastic holder, focallength 5mm (3mm to the holder, inside 2mm recessed)
4) 7.1mm x 3.5mm, little too wide for the small brass module (you can file a half mm away without problem), but fits the plastic-holder from silver modules when you remove the original lens, focallength 1.5mm
5) 3mm x 2mm, focallength 1mm
6) 4mm x 3mm, focallength 1mm or less

readings red:
0) naked diode: 40mw
1) aixiz,acryl uncoated loose: 35mw
2) aixiz,acryl uncoated threaded, pinhole: 32mw
3) aixiz, acryl uncoated threaded, no pinhole: 35mw
4) dvd, acryl AR-coated "7mm": 35mw
5) dvd, acryl AR-coated "6mm": 37mw

readings 405:
0) no lens: 13mw
1) aixiz,acryl uncoated loose: 11mw
4) dvd, acryl AR-coated "7mm": 9mw
5) dvd, acryl AR-coated "6mm": 7mw
6) BR, acryl, AR-coated: 12mw

so far no news here. the AR coated ones perform a bit better than uncoated ones. the focallength doesnt seem to affect the output much. in my case, the "pinhole" in threaded aixiz collimators didnt waste that much, only 6%. worth it, if you like a clean dot without specles around, perhaps. the dvd's red AR coated lenses absorb a fair bit of 405nm light.

if that would have been all, i wouldnt bother posting this.
the real surprise for me was the performance of "5) dvd pickup"! in experiments some time ago they seemed useless, producing rings and distorted patterns. indeed the itself relatively small lens has rings (like those flat fresnel lenses) between the rounded middle and the outer holding/gluing-ring. no idea what i did wrong last time, but now i had no problems. the focallength is so short, that the diode almost touches the lens. therefore the laser"beam" didnt widen enough to even shine onto the "bad" outer section of the lens! it looks to be only a mm when it reaches the lens! which means: the beam, when collimated, will be that tiny diameter as well! in the size of a nice green laser, in fact, and not those fat 5mm+ beams from regular collimators! that will mean you wouldnt even have to focus the beam to burn, 1mm² should be enough for fun already! :-)
the bad news is, of course, that a thin beam expands more over distance. you can only have one at a time, diameter or beamquality. same prob with all lasers, and no way to get around this. so the beam-behaviour should be a bit worse than that of a greenie.
that said, i didnt test that lens in a carefully set-up test yet.
problem two, now, is how to put a lens so close to the diode. both aixiz modules dont work for this. the brass one cant work at all. the silver one works, if you swap the installed lens in the black holder with the new one. you can screw it in close enough (i think), but then its so far inside that there is no way to install the metal focussing-ring.
my fix for this is to use a brass module, put the diode on top of the holding-part instead of at the far end, and then shorten the top lens-holding-part and glue the new lens onto it.

so far my findings, i think i will only use pickup-lenses in the future! fortunately i have them left here!
i will write more when i tested it in a real-world-setup.
no pics yet.. if enough people scream, i'll do some to show you the lenses and my aixiz-module-mod at least.

what do you guys think so far?

manuel
 





Re: results: different lenses and red/br efficienc

Thanks for posting this interesting and informative comparison.

Bill.
 
Re: results: different lenses and red/br efficienc

glad you like it!
hmm, not too many replies here.. doesnt matter, i am happy with my findings anyway! :-P

manuel
 
Re: results: different lenses and red/br efficienc

Nice job putting this info together for future reference....
Thanks for your effort. ;)
 
Re: results: different lenses and red/br efficienc

Thank you for posting these results, i have seen different lenses being offered on some websites and was wondering which lens performs better for reds, and for BRs.

Ted
 





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