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why are there so many different laser lenses?

reloader45

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Hello,

looking for DIY laser parts, I see, that there are a lot of differént lenses for different wavelengths.

Do I need a special lense for every different wavelength?

What will happen, if I use a "red lense" for a 450 nm Diode? Is there only a bad focus, or will it destroy the Diode by backreflection?

best regards

Edgar
 



DTR

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Depending on the application different lenses will be more suited to get the best results or more desired tradeoff.

The most common multi-element lenses are AR coated for a narrow range and it would be best to use the ones that have the right range for your diode. There are also several common single element lenses which are broadband coated and even though they will have a peak within the 400nm to 700nm range the efficiency is high enough across that full spectrum to be considered safe to use for any visible laser diode.

Using say a 600nm-700nm for red on a blue can have several negative effects. Worst case is back reflection into the diode cavity at some random point causes a COD failure. If not a straight failure an accelerated degradation rate from that back reflected energy causing higher running temps from the extra waste heat generated as well as more wear from any of the light being reflected directly back into the laser cavity. And obviously there is a loss in optical energy output from the unit.🍺
 
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reloader45

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Hello,

thank you for this Information. I have differnet boxes for different lenses. But when i look atn them, I can not see any difference (chinese glas lenses)

That is the reason, why i am a little bit afraid to mix them accidently.


best regards

Edgar
 

hakzaw1

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Someday you will understand more.. this happens to all of us at one time.

Not to be rude BUT...
It is not all that different than asking why there are so many eyeglasses?-
Or safety glasses?

Keeping them unmixed is a no brainer.. look closely and in the 'reflection' (somewhat depending on WHAT kind of light)-- this afaik is mainly the AR Coating (look that one up plz) also this may not look the same from 'both ends'
example- to me at least the AR coating for all lasers looks a gold/amber-ish color.

another helpful way is to get permanent markers in as many colors you can get.

Devise a 'system' for yourself (make a word file for that) and every new buy needs to be marked.. we also do this to NEVER get an urge to insert batts to see which way the go.. (never!)
I use many colors of shrink to mark wires. There is a bunch of uses for shrink--& a little can go a long way.
Best friend of LPF at ebay is heatshrinkbuddy--(IIRC) By just asking nice, Buddy will include free small sample pcs. He is now very aware of LPF.... but plz do mention 'us' (including me -- ebay snapplz.)


You can somewhat see the red or black marks only by refection-- on black items.

To get around that i keep a fine tip white-out pen which writes great on black items- & fairly perm if you let it dry.
AND DTR is a huge asset to LPF and by far the best we have here in regards to questions and tutorials.
Every one of his should be required reading when joining LPF..
Be sure to always search before asking questions .. IMHO none of us has enough/any 'extra time' and you can help with that by just searching FIRST... (we need the 'let me google that for you' emojie back. lol)

WE all thank you ...Jordan ---

vr
hak
 
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reloader45

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Hello,

my experience is, that you save the most time, if you don`t answer to a question you do not like.
If you get no answers to your questions, you quickly find out, that something goes wrong.

best regards

Edgar
 

hakzaw1

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Not totally sure what you mean..
My experience is based upon 10 years at LPF AND a lot upon help I was given when asking my questions.
either way best wishes Edgar
VR
Leonard
 

Alaskan

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If you had a laser power meter and three cheap low power RGB laser pointers, you could test which lenses of the same design have the least loss through them at one of the three colors or wavelengths to know which lens to use.
 

reloader45

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Hello,

I have a laser power meter. The problem is, that a 5 W blue Diode died short after i tried a "red lense" . I am not willing to make such expensive experiments in the future. That was the reason for my question. But DTRs answer works well for me.

Yesterday evening i started to build a 9mm copper host for a 520 nm Diode. I will finish it today, but next time I will order some copper Hosts from DTR. His copper heat sinks are made very nice and from the construction details you can see, that he knows his business.

Thinking about my time, I can not build them for the money he takes.


best regards

Edgar
 

Alaskan

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I would ‘t use the lenses you are questioning to collimate a laser, instead use a laser pointer which already has a proper lens in it to test the loss through each of the lenses you are unsure of its AR coating to see which ones have the least loss for R, G or B.
 

paul1598419

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Hello,

I have a laser power meter. The problem is, that a 5 W blue Diode died short after i tried a "red lense" . I am not willing to make such expensive experiments in the future. That was the reason for my question. But DTRs answer works well for me.

Yesterday evening i started to build a 9mm copper host for a 520 nm Diode. I will finish it today, but next time I will order some copper Hosts from DTR. His copper heat sinks are made very nice and from the construction details you can see, that he knows his business.

Thinking about my time, I can not build them for the money he takes.


best regards

Edgar
I seriously doubt the lens caused this failure. It is more likely that the diode failed because it was over-driven. We forget sometimes how very hard we over-drive these diodes, often just under fold-back, and this alone will cause some failures.
 

RedCowboy

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Hello,

I have a laser power meter. The problem is, that a 5 W blue Diode died short after i tried a "red lense" . I am not willing to make such expensive experiments in the future. That was the reason for my question. But DTRs answer works well for me.

Yesterday evening i started to build a 9mm copper host for a 520 nm Diode. I will finish it today, but next time I will order some copper Hosts from DTR. His copper heat sinks are made very nice and from the construction details you can see, that he knows his business.

Thinking about my time, I can not build them for the money he takes.


best regards

Edgar
So I take it your 5W laser diode was not in a DTR copper module, if so then that's likely your problem, the typically overdriven 5W+ blues need that high quality copper ( high purity of copper ) module and the full copper back half with pedestal to carry away waste heat.

For instance a nubm44 driven at 4.5a is also drawing around 4.5v+ so you have basically 20 watts in and 7 watts out in light 13 watts of waste heat, almost twice the waste heat as what's coming out the front, so yea, go heavy on the heat sink and make sure your module is not a bottle neck, I tested some of the Chinese " red copper " modules and they are garbage for moving heat, red copper is dirty copper and a poor conductor of heat.
 
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reloader45

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Hello,

no it was a chinese 5,5W laser with Aluminium heat sink and fan. The heat sink did not even get warm. When someone overdrived the diode , than it was the producer.

It was this one:



best regards

Edgar
 

RedCowboy

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I bought a black aluminum housing like that with a brass heat sink that fits inside and it was absolutely pittitiful at moving heat, a real joke, my diode was dropping power by the second as it overheated.

Yours probably came with a de-canned NUBM diode, did you look inside when you took the lens out and see a window can or just the emitter ?

I was really surprised at how poor the heat sink was, the little fan is pointless when the diode overheats and the case would not feel hot because the heat never got out, I don't see how they can sell such crap.

This is the type I tested, that brass looking heat sink is no good for the 5w+ blues,

 
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CDBEAM777

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Hmmmm...I did NOT know Red Copper was crap !!!! Good to know !!!!!!!!!

Hmmm...Now that Laser Show Parts site has been off line....since late 2018 !!!! Hmmmm ??? I am not sure if bits are available from LSP ????
They had good quality in CU and I have used their CU in both 5.6mm and 9mm style !! Email Dave !!

Lasertrack has really nice product...IF looking for a rectangular design. They have both 5.6mm and 9mm in CU. Somewhat more expensive....BUT….their design and quality....are very, very good !!!!

Of course....for a round design LD mount...DTR is the man !!!

CDBEAM
 
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reloader45

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Hello,

I think, the thermal conductivity of brass is not so bad compared to Aluminium alloys.

Of course, pure copper is better, pure silver is a little bit better than copper and natural Diamonds are perfect (joking)

If pure silver would be cheaper, i would built a heat sink from silver. It would look nice and precious.

At the moment, i build all my heatsinks from pure copper. My favourite diameter is 20 mm. This Diameter is sufficient to install a compact laser Driver into the milled pocket of the heatsink.
My next project will be a 3.5W 470 nm blue laserpointer. This is a very nice color, compared to the 445 nm lasers.


best regards

Edgar
 

steve001

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Hello,

I think, the thermal conductivity of brass is not so bad compared to Aluminium alloys.

Of course, pure copper is better, pure silver is a little bit better than copper and natural Diamonds are perfect (joking)

If pure silver would be cheaper, i would built a heat sink from silver. It would look nice and precious.

At the moment, i build all my heatsinks from pure copper. My favourite diameter is 20 mm. This Diameter is sufficient to install a compact laser Driver into the milled pocket of the heatsink.
My next project will be a 3.5W 470 nm blue laserpointer. This is a very nice color, compared to the 445 nm lasers.


best regards

Edgar
Consider using beam correction optics.
 




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