Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[taggalucci]

with my current 3.3fl lens i got a beam of just under 4mm at aperture and a divergence around 1.1

Was this uncorrected? I'd be interested to know what the uncorrected beam specs are for both axes in the near and far field.

I have new lenses from dave and 2 other company's on the way with FL from 2 to 2.25 to 2.5 and my current setup was done with a 3.3FL lens

So i will have enough lenses to do alot of testing.

Would you be happy to post your findings on these lenses? It would be good to know the near and far field beam specs for both axes of each lens (with power readings too if possible).

Stack vertically before the correction optics. this will get you the beam of 4mm by 4mm.
So the question now is how do we do a quad.

What was the stacking height difference you've used, and was it with the 3.3FL lenses?

A 8 build would not work.

I'd be interested to see how tight 8 diodes could be knife-edged/stacked (depending on diode orientation) and how bad the divergence would be without correction but with some de-focussing of the collimators to square up the beam. Might be OK for large scanners, aerial laser projectors...

[steve-o]

steve what is your power before optics?

I'm getting 661mW raw output from the diode w/my (diy) meter. I'm sure that the lens and barrel that I'm using are chopping the edges off for a significant power loss and making for a slightly better beam profile.

[kiyoukan]

i will try to answers those above questions when i have the time sry.
So you are getting 661mw raw and what about after diode lens?
You should not be dropping below 500mw unless one of your lenses is very bad.

[steve-o]

I'm having the best luck with a aixiz triple element red ar coated. It's 471mW after the lens. I'm losing 190 mW. Yes, it's definitely not the best lens in the world. At this point, I don't care. I'm ready to start building a red to go w/ the green/ blue. I need to see an RGB SOON or elst me start looosing me mind ............... ........................... ..AAhhhh-hahahahahah ..

[kiyoukan]

So you are losing 28.7% on the diode lens.
you are losing about 8.8% on correction optics.
you are losing 37.5% total. err 35%
You need to find a better diode lens.
Also how clean are your correction optics?
That loss on the diode lens could be due to back reflections to the diode and that is bad, not just power loss but will shorten the life of the diode.

[steve-o]

Ok, I got some sleep. Re-editing post.
I'll take your word for the percentages k.
I do need a better collimation lens, I have experimented with all the ones that I have, and am holding my breath in anticipation for new findings here. I have posted my findings a few pages back.
My optics are clean. The lava lenses are brand new, fresh out of the box. What you are seeing in my pic are a few specs of dust, highly amplified by the camera and the laser light.
Back reflections. They can kill a diode, not just shorten the life (I speak from experience ;] I will check the aixis' AR coating .. I doubt that they are good quality, don't know for sure.
To sum it up, I believe that the losses are coming from the long FL lens and the small diameter of the barrel, chopping off part of the beam.
Thanks for your concerns and I appreciate the advise

[steve-o]

My reason for this approach is simple. Price and expedience. I currently have (3) G71 diodes, (3) col. lenses (3) retainers /housings, etc.
If I were to start construction right now I would be able to have 1.3 Watts of red in a couple weeks. The other option is to wait .. hmmm .. I think I'll take the losses and start building now, rather than keep experimenting. It's good enough. No doubt you guys will find a setup with >90% throughput, eagerly awaiting that, but I gotta build something .. now .. lol ..

[Solarfire]

For what it’s worth, I’m going with Dave’s lens a PBS, wave plate and lava cylinder correction. As Simon suggested a while back, vertical stacking is the way to go, imo this is probably the best way to go with minimal optics for a good quad. In the setup below all beam paths are equal length and 4mm x 4mm @ the aperture and 1-1.2mrad is doable.

[kiyoukan]

While i think lava optics are kinda nice they are a bit small, and hard to work with.
The larger lenses are more forgiving. You can be a little bit off and not get any power loss.
If you were to be 1mm of with lava's correction lenses you would get a good amount of loss.
The fact that you got 8% on fresh lenses might be the sign they are not in position perfectly.
The last set of lava optics was cd beams and i think he tested the power loss of around 4% but he stated that took several hours to get that low.
So tonight im going to have my setup redone with the vertical stacking.
Solarfire, i know for my correction optics at least that distance from the diode lenses is very important.
I found around 30mm to be the sweet spot.
Is this the same with lavas?
If so what distance is that in your setup?
As much as i hate the aixiz housings they were nice precision forward and back movement, so it allowed me to quickly adjust the distance to make sure the spot size was the same.
Once my setup is done im going to see if any one wants to get in on getting more of these correction optics made.
This is the price quote from the manufacturer.

EFL(mm)_______L(mm)____________H (mm)______unit price (USD)
60_____________32_______________30__________25
10_____________20_______________10__________15
So the price is about the same as drlavas however with much more forgiveness as far as positioning.
I am looking to order some and i know a few other members want them.
They are very simple and have a working distance of 62mm between the 2 lenses, so for a beam under 1 mrad you would want about from the diode lens 30mm then each lens is around 6mm thick so an extra 12mm plus the 62mm between them gives you a total of 104mm.
Its slightly large but it does have it benefits as far as use and less power loss.
Right now the coating they have gets a tiny bit over 1% for 635nm but is less than 1% for most other colors.
Seeing as we only need these for red i could change the coating to have around 0.48% loss for 635nm

[logsquared]

I have been working with these diodes a lot over the past few months. Although I think I may have been the first to suggest moving the telescope away from the collimator to get different magnifications I don't think its the best sollution. Most of my builds and testing have been with 4mm lenses. So, I haven't tested much with Daves 2mm lens. Here is what I've found through practice with 4mm lenses..... Moving the telescope further from the collimator gives the ability to focus the spot through a larger range of sizes than if the first lens is very close to the collimator. However, there is only one point where the spot is truly in focus. Trying to reduce the spot size by slightly de-focusing the telescope works to make the spot smaller but doesn't change the aperture much. So, you can get lower divergence but not the smallest aperture possible. I have found that putting the first tele lens as close the the collimator as possible and making the tele ratio what the math says is should be gives the best quality spot and smallest aperture size. So, if you have 8mRad with your collimator and want 1mRad corrected use a 8X tele and put the lenses as close as possible.

Because the divergence is so great with a 2mm lens the actual results will probably be slightly different than the math would indicate. Unfortunately, I have not had the chance to test with Dave's lenses much. But my guess is the will be the best for quads with minimum optics, just needing a really long telescope.