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Need help/advice with a r&g to yellow dual diode bulid.

BobMc

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I trying to get rid of the splash I have on a dual diode build. It has a ndg7475 adjustable by a 10 turn 5k pot for the green and a mitts 500 for the red, adjustable by a single turn 5k pot, pbs'd together get get yellow.
Have a splash problem I'm trying to fix. Was thinking of getting an adapter made, that would fit Sanwu's 3x BE, thinking that might fix the problem? Swapping other lens has already been tried.
I'm open to other ideas that might be better. Appreciate any and all ideas, thanks. :thinking:



















Sorry the pictures are so fuzzy. :(
 
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diachi

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Why PBS and not a dichro?

A beam mask on the output would likely remove all or most of the splash.

A BE would probably do it too, but you end up with differing beam divergence on each colour, refractive index is not constant with changes in wavelength, it's inversely proportional to wavelength.

Edit: Alaskan bet me to it, damn! :p
 
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BobMc

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Can you mask the splash so it can't get out?
Was thinking that but, how to mask, with what?

Why PBS and not a dichro?

A beam mask on the output would likely remove all or most of the splash.

A BE would probably do it too, but you end up with differing beam divergence on each colour, refractive index is not constant with changes in wavelength, it's inversely proportional to wavelength.

Edit: Alaskan bet me to it, damn! :p
I can research into a dichro.
BE was my thoughts?

Only simple solution I could think of is a mask. If you use a beam expander get a achromatic BE so it can be used at more than one vis wavelength, you can buy them, I have one.

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1580
You don't think Sanwu's BE would be up for the task? Wouldn't expand/mix the wave lengths?
 
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grainde

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What about changing the lenses? If you are using a G lens you will more than likely have splash, a 3 element or an acrylic (if low powered) on the other hand will improve it.

Heres a link to my build if it helps:
http://laserpointerforums.com/f40/my-first-yellow-build-updated-yellow-beam-91523.html

:beer:

Edit: A mits 500 probably isnt the best choice. You could try lower powered single modes instead; LPC826 etc and either a 532 or single mode 520?
 
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BobMc

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What about changing the lenses? If you are using a G lens you will more than likely have splash, a 3 element or an acrylic (if low powered) on the other hand will improve it.

Heres a link to my build if it helps:
http://laserpointerforums.com/f40/my-first-yellow-build-updated-yellow-beam-91523.html

:beer:

Edit: A mits 500 probably isnt the best choice. You could try lower powered single modes instead; LPC826 etc and either a 532 or single mode 520?
Have tried changing the lens. No joy. :cryyy:

Thinking of trying the adapter for the Sanwu BE. See the four screws on the front of the unit. Was thinking of trying to get a mount or something that could be attached there, that would fit the 3x BE. Still thinking though, thanks for your thoughts. :)

Very nice dot your r&g to yellow produces,like to get something close to that. Thanks for the link, sweet build. :)
 

paul1598419

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The two diodes you chose to match are both too high power for acrylic lenses and are never going to match as the Mits has far greater Divergence in the slow axis than the NDG does. If you just have to use these diodes, I'd use a single dichro to either pass green and reflect red, or visa versa. You will still have the mismatch in divergence, but it should be easier to sync them up and your splash problem should resolve.

Edit: The Thor Labs BE are pricey, but starting at X10 and going up you have to have a maximum beam input of 3mm or less down to 2mm or less for a X20 BE. With the Mits in the picture this may not be possible.
 
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BobMc

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The two diodes you chose to match are both too high power for acrylic lenses and are never going to match as the Mits has far greater Divergence in the slow axis than the NDG does. If you just have to use these diodes, I'd use a single dichro to either pass green and reflect red, or visa versa. You will still have the mismatch in divergence, but it should be easier to sync them up and your splash problem should resolve.
I'm sorry, forgot to mention which lens are in it. They are 3 element lens, other have been tried. but no joy.:cryyy: :thanks: for your input. :)
 
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thebouljello

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Check out the yellow build on my page if your interested. I just used cheap ebay lasers and a dicro from ebay but it worked well. However, the green laser began to degrade after some time. I also found it difficult to adjust the brightness of the green laser; it probably has to do with the ir diode and DPSS process.

<----- That's it in my profile picture
 
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paul1598419

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If you used a 532nm, the driver has a current adjustment on it and you can adjust the brightness of the green that way. It is always a good idea to heat sink the output transistor on the driver as it tends to run hot.
 

BobMc

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Check out the yellow build on my page if your interested. I just used cheap ebay lasers and a dicro from ebay but it worked well. However, the green laser began to degrade after some time. I also found it difficult to adjust the brightness of the green laser; it probably has to do with the ir diode and DPSS process.

<----- That's it in my profile picture

Nice build idea. Sorry that it started to degrade but still a nice build.

Going to try to get an adapter made for a 3x BE. Don't know if it's going to work but going to give it a try. :thinking:
 

thebouljello

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The green laser that I used doesn't have a potentiometer on the driver, but it doesn't really matter because I was just testing to see how well the concept works. I think Bobmc will have better results with higher quality lasers and optics.
 

Cyparagon

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If you use a beam expander get a achromatic BE so it can be used at more than one vis wavelength
I'm pretty sure that is not necessary since each of the prior collimating lenses are variable.
 

Alaskan

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I bought my Thorlabs achromatic BE on ebay fairly cheap, I'd only use a BE if you want to expand the beam too, otherwise not necessary, a small length tube will probably do the trick.
 

BobMc

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I bought my Thorlabs achromatic BE on ebay fairly cheap, I'd only use a BE if you want to expand the beam too, otherwise not necessary, a small length tube will probably do the trick.
Not necessary to expand the beam. Searching for a nice yellow dot. Thinking the BE may be the best way to do it. ???
 




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