Another project red?

[logsquared]

Hey guys i just found this thread and happen to be working on a multi diode red project right now. Here are some things i have found / measured in my experiments so far.

Here are some things a found necessary for my design to be feasible:

1. Simplicity. When using large numbers of diodes like 18-36 diodes it needs to be easy to build and adjust. Also, parts should be readily available.

2. Cost. Expensive lenses sound good at first but when you do the scaling it gets real pricey. 18 lenses X $20 = $360.

3. Size. My first designs had 4 axis mounts for every knife mirror mount and a 1 axis mount for the diode mount. All with 1/4 80 adjusters. It soon became apparent this thing would be huge.

Here is where i am at after 2 months of scratching my head and a full tablet of sketches. I decided to use the aixis modules and glass lenses with the LOC diodes. I decided to use a 2 axis mount on the mirrors and a slotted mount for each diode. the mirror mounts are set and glued. This should provide the best long term stability. For mounting the mirror to the mount itself i will use a jig to place the mirror with good accuracy. This may lead to a small amount of clipping of some of the beams. This has to be accepted for simplicity reasons.

Here is some data i measured that may be useful to those designing their combiners. With a LOC in an aixis barrel with aixis glass lens @ ~ 2 inches from the lens the beam is at 82% power if put thru a .8" X .16" window, if the window is .75" X .15" the power is 78 %, and for .75" X .13" i got 75% transmission.

Using this data a 3mm X 3mm beam is attainable with a 2 rows of 4 diodes and a 2.5X telescope with 82% transmitted. ~.55 mRad

Or 3 rows of 6 (18 diodes) with a 4X telescope with 82% transmitted. ~.88mRad

Or 4 rows of 7 (28 diodes) with a 4X telescope with 75% transmitted. ~.88mRad

Just for fun. if a 5mm aperture is ok then: 6 rows of 10 (60 diode) 4X tele with 75% transmitted.

Of course any of the these can them be run thru a PBS for 2x the power.


To date i have made a few versions of the 2 axis mirror mount i think i have finally setteled on the final design. I set it up at a target ~ 100 ft away and adjusted the mount waited about 48 hrs and the mount has stayed true on target without glue. In the next few days i will have a complete 2 row of 4 combiner machined. Still waiting on the rest of my aixiz barrels to come in. oh yeah, the base size for 8 diodes is aprox 3" X 5" and for 18 diodes (no PBS used) 3.5" X 13" this doesn't include the telescope optics. I will post pics when i get it machined and running.

Question for andy_con?

I am curious to the mRad divergence of the roithner lens you use? Also, what diode is used with that lens? With the aixiz glass i can get about .2 -.225 mRad full angle. When i tried using shorter focal length lenses i did get considerable size reduction at aperture but what ever percent reduction at aperture was multiplied in divergence or far field spot size. The roithner lens must be a very special aspherical type. If the far field and near field spot size are proportionally smaller than a simple lens then they would be a god send for increasing the combined beam power density.

[logsquared]

@mecheng3

If I where you I would do it good (with good lenses) or don't do it at all.

Also when you use the lens 27, they have just metric screw in threat for lens adjustment, this is in mu opinion not fine enough for a multi diode setup because you will get alignment issues with that many diodes.

My lenses got very special fine threat for very fine adjustment of the lens and no need to secure it, a stable and thin beam is mandatory for a multi diode setup.

I think spending some more money on quality lenses will safe you allot of trouble.

Sounds like a hack but using teflon tape on the loose aixiz threads makes adjusting smooth and easy. Once you have a good focus ( i set my target at about 200 ft) epoxy the lens in place.

I agree better lenses are good. I think there is a price/ performance tipping point when using lots of diodes though.

[edison]

If you need mounts for collimators let me know. I have bought 20 of these. The baseplate for a quad is worked on this weekend.

The mount will hold a collimator up to 11mm and the beamheight is 20 mm. The flexure mounts of chad are the same height so together they are perfect making a good setup.

[badger1666]

If you need mounts for collimators let me know. I have bought 20 of these. The baseplate for a quad is worked on this weekend.

The mount will hold a collimator up to 11mm and the beamheight is 20 mm. The flexure mounts of chad are the same height so together they are perfect making a good setup.

how much did the mounts cost edison they look quiet nice

[andy_con]

Question for andy_con?

I am curious to the mRad divergence of the roithner lens you use? Also, what diode is used with that lens? With the aixiz glass i can get about .2 -.225 mRad full angle. When i tried using shorter focal length lenses i did get considerable size reduction at aperture but what ever percent reduction at aperture was multiplied in divergence or far field spot size. The roithner lens must be a very special aspherical type. If the far field and near field spot size are proportionally smaller than a simple lens then they would be a god send for increasing the combined beam power density.

although i have 30 roithner 7020h lens, im still yet to even out one on a diode, so i dont know the beam specs yet. but yes im using LOC diodes.

there is a person on this forum who is mega Knowledgeable when it comes to reds and lens. he may see this post and respond during today, if not ill email him later.

do you have any pics of your setup?

[logsquared]

do you have any pics of your setup?

No pics yet. At this point I have only one mirror mount machined and mounted to a scrap piece of plate to test stability i am going to try and machine the rest of the 8 combiner today and hopefully finish it on sunday. i only have 4 LOC + aixiis modules right now. Hopefully the other4 get here soon.

Anyone have a good source for the LOC diodes? Seems like the aixis ebay site has the best deal on the barrels (10 for $25 with plastic) and glass lenses ($5 each). If the 8 banger works well i want to build two 18 or 28 combiners and PBS them together. Need lots of diodes for that!

[hobbybob]

@logsquared:
You just missed a great groupbuy !
5 dollars for a sled containing a LOC diode and mirror.

I am very interested in your build and look forward seeing your pictures !
Especially the 8 or greater number of diodes combined.

[daedal]

Anyone have a good source for the LOC diodes? Seems like the aixis ebay site has the best deal on the barrels (10 for $25 with plastic) and glass lenses ($5 each). If the 8 banger works well i want to build two 18 or 28 combiners and PBS them together. Need lots of diodes for that!

Shameless plug...

See my signature

I do have PBS cubes and drivers as well that will be posted on there by the end of Sunday

--DDL

[hobbybob]

@DDL: any info on the PBSes and drivers ?
PBS: Transmission/reflection losses, for what colors etc ?
Drivers: positive / negative drivers ? Max. drive current ?

looking forward seeing more info on them. Cool addition to your shop !

[p1t8ull]

I have used the 7020H from Roithner before and using a LOC diode got beam with about 3x5mm hotspot area out of it with ~.3mR divergence.
These are AR coated and less lossy than either the acrylic or glass Aixiz, not quite as good as a LENS27 but they are a fraction of the price..
If combining >4 diodes and don't object to using a 3x or 3.5x telescope to correct the beam then these seem like a cheap way to go

[hobbybob]

I have used the 7020H from Roithner before and using a LOC diode got beam with about 3x5mm hotspot area out of it with ~.3mR divergence.
These are AR coated and less lossy than either the acrylic or glass Aixiz, not quite as good as a LENS27 but they are a fraction of the price..
If combining >4 diodes and don't object to using a 3x or 3.5x telescope to correct the beam then these seem like a cheap way to go

But what will a telescope cost ? Dunno what to look for and who is selling them and what prices should be expected ? Then you save on the lenses but spent it all on a telescope ?
Maybe a telescope can be had cheap ? If so, where ?

[shrad]

hi guys

for what I know, as soon as you have more than 4 diodes you'll need a telescope (at least a 2:1) if you don't wand to end up with a fat beam

you can then either buy a telescope, or build one yourself with two lenses

[p1t8ull]

Andy posted a way to get going here with a pair of lenses as a telescope.
If using a 3x or 3.5x telescope with 7020H (.3mR) collimators for example, a telescope is not only required to make a smaller beam but also works out a hellava lot cheaper as the diode count rises.

Back on to the best collimator for the job.. apart from shifting the beam diameter/divergence to a more acceptible specification, when combining > 4 diodes there are other advantages to having longer FL lenses and bigger diameter beams as opposed to the shorter FL LENS27's and CAY046's etc. especially when knife edging them together. For one it's easier to work with the larger diameter beam, secondly smaller gaps between individual beams result in a more dense beam with smaller overall diameter.

The only thing about the 7020H is that being an acrylic I wouldn't like to say how well they will hold up if the LOC's are wound up to silly current, maybe Andy will have some details on these lens' performance as his build progresses

[andy_con]

listen to the man (p1t8ull) he really does know what hes talking about.

[hobbybob]

Thanks p1tbull, will look into the lenses and see what they cost.
What is, by approximation, the distance needed between the lenses for a nice result ?

[shrad]

you have to take plano-convex lenses with focal lengths with the same ratio as the telescope (for example a 3X telescope will need a 3cm focal length and a 1cm focal length) and superpose the focal points, basically

(correct me guys if I'm wrong here)

[danielbriggs]

What is, by approximation, the distance needed between the lenses for a nice result ?

Try this:
http://webphysics.davidson.edu/physl...ics_bench.html

Use nominal figures. e.g. Add a beam, add a convex lens X=1.00, fl=3.00, add another concave lens, X=3.00, fl=-1.00.
You could use two convex lenses, but overall telescope length would be increased. e.g. X=5.00, fl=1.00

Dan

[hobbybob]

Thanks Dan, excellent link which allowed me to play with the lenses.
But does this really mean if i come in at 6 mm diameter i can bring it down to 2mm with very little divergence using a 3:1 telescope ?
Sounds too good to be true...

[danielbriggs]

Divergence increases as diameter decreases by same factor. Steve (MixedGas) posted the technical description for this (and whether which way round worked or not - can't remember). Also can't remember the thread...

[daedal]

@DDL: any info on the PBSes and drivers ?
PBS: Transmission/reflection losses, for what colors etc ?
Drivers: positive / negative drivers ? Max. drive current ?

looking forward seeing more info on them. Cool addition to your shop !

They are now on the site and available.

I've measured the PBS's to have <5% loss. I've got PBS's for 405, blue, and red. They measure 0.5".

The drivers are positive, and will supply up to 400mA with full analog modulation. I've used these drivers and am very pleased with the results. The price is not bad at all either

--DDL

[daedal]

I want to add another one to the mix... another lens that is...

http://www.thorlabs.com/thorProduct....mber=C110TME-B

What do you guys think?

--DDL

[edison]

If anyone is looking for a driver have a look at the bottom of this PDF:

http://www.versatis.nl/download/Shortform%20catalog.pdf

It,s an 8 diode drver with 2 amps per driver on one board. Its easy to miss so scroll slowly :-)

I tried to contact the company but i didn,t hear from them yet. Hopefully someone here want to pick it up from here and get a price from them. The company is B&Wtec


info@bwtek.com www.bwtek.com

[p1t8ull]

I want to add another one to the mix... another lens that is...

http://www.thorlabs.com/thorProduct....mber=C110TME-B

What do you guys think?

--DDL

I tried to read the blurb but my eyes kept darting back to the £60 GBP price tag and started watering profusely

[edison]

As the search goes on for the perfect lens maybe this is something:

http://www.egismos.com/support/laser...O1-CO-6Mv2.pdf


Specifications(typical@tc=25℃)
Item. symbol O1-CO-6.5-8.9-M O1-CO-6.3-9.8-M
Material Glass (OHARA L-TIM28) Glass (OHARA L-BAL42)
Operating Wavelength λ 600~810nm 630~850nm
Numerical Aperture NA 0.29 0.17
Effective Focal Length EFL 8.9mm 9.8mm
Working Distance
(Back Focal Length)
WD
BFL 7.55mm 8.25mm
Collimated Beam Size ≤6mm at 10m ≤8mm at 10m
Collimated Beam Divergence 0.2~0.3mrad ≤0.3mrad
Wave Front Error ≤0.05λ (635nm) ≤0.04λ (780nm)
Outer Diameter OD (φ) 6.50mm 0/-0.03mm 6.35mm±0.02mm
Clear Aperture
(Effective Diameter) CA 5.2mm (R1)3.5mm (R1)
R1 Φ5.2mm / R2 Φ4.6mm R1 Φ3.5mm / R2 Φ3.0mm

Center Thickness CT 2.36mm±0.03mm 3.00mm±0.02mm
Transmission (AR Coating) Tr ≥97%(635nm) ≥97% (650nm,780nm)
Operating Temperature -40℃ to +160 ℃ -40 ℃to +160 ℃
Storage Temperature -60 ℃to +200 ℃ -60 ℃to +200 ℃
Surface Quality
(Mill Standard) 60/40 60/40

[logsquared]

Update on my combiner project.

FU*K! how many diodes can a person kill in one day? Finally got the mounts machined for the 8 diode test combiner. Only have 4 diodes at the moment. That's cool, i will just put them on the four "corners". Put 2 in to get started then go ahead and ground the chassis with a high side driver. Doh!! now i only have 2 diodes to work with.

Good news is the 4-40 screws have enough resolution to aim and overlap the beams at a distance. The initial idea seems to work. Now I only need to make a small change to the mirror holders to allow more movement in the +X direction. pictures coming soon.