Lazy Mans Beam Expander for 445nm NUBM44 6+ watt laser diode.

Finally have a driver installed for my decanned NUMB44 blue laser diode set to 4.5 amps of current which is producing 6.5 watts out of a S1 lens in a MrCrouse Zaser XL host. For as much power as this thing is producing, the beam isn't all that impressive compared to 1 watt of 520nm and the divergence is horrible but, I expected that - What would be really cool is to PBS a pair of these, or knife edge a few, then you would really have something. I probably should be more impressed at the power, just that 520nm green is so much brighter at far less power I'm spoiled, but I'm over half way there with this pointer after losses, at this wavelength/color our eyes are less sensitive to, over 6 watts out is near 70 percent as bright as a 1 watt 520nm green laser.

Due to the high divergence, I threw together a fast beam expander from parts I had purchased in the past but never used, they happened to work out just right for the host I put a NUMB44 445nm 6 watt laser diode in. To be able to adjust the focus, I put a 2 inch camera helical focuser on the end of my pointer by just attaching it with black tape and then a 100mm focal length 50.8mm/2 inch diameter PCX on top with more black tape and I'll be damned, the thing makes a nice beam expander with plenty of focus range. Inside, I'm using a S1 lens which is purposely adjusted out of focus so the beam output matches the size of the 100mm FL lens on the end of the focuser and everything is working out great, although the beam could still use correction prior to the PCX lens as it is still a rectangle shape.

Correcting the output of the NUBM44 multimode laser diode to be less of a rectangle shape is another project, not sure how well it would work with this kind of beam expander, since the input of corrective optics need to be focused to infinity first and this setup depends upon the output to be de-focused out of infinity so the "spot" size closely matches the diameter of the PCX lens on the end which collimates it.

Three more hours and it should be dark enough to get some beam shots





Link to focuser I bought on ebay: New 2 inch 2" Double Helical Focuser 0 02mm Scale for Telescope Guider Precision | eBay

Link to PCX lens I bought on ebay (later replaced due to splash problem, see posts below): Newport PCX Plano Convex Lens KPX187 50 8mm x 100mm N BK7 Uncoated NIP | eBay

If a wheel were put on the S1 (or G2) lens you could turn from the outside, you could have a variable diameter beam expander. That whole black tube on the end with the lens attached moves in and out to focus to infinity. Only problem I'm trying to work out is how to get rid of the wings which show up when focused to infinity They are not very noticeable in the beam itself, but when pointing at something in the far distance they can be clearly seen. Perhaps adjusting the size of the spot on the PCX lens will get rid of them, more experimentation to come and will update the thread when I find the solution. I don't even know what to call the splash right and left of the spot, anyone? Maybe this is a product of the S1 lens being out of focus? Same problem regardless of which way the PCX lens is facing.

Here's a link to another thread showing a LaserGlow 10X beam expander on this same type of host:

http://laserpointerforums.com/f40/z...9w-modified-hercules-beam-expander-91215.html

Re: Quick and dirty beam expander with 445nm NUBM44 6+ watt laser diode.

i'm waiting to see the beam shot!!
and this laser can melt Solders right?

Re: Quick and dirty beam expander with 445nm NUBM44 6+ watt laser diode.

I have only one decent beam shot tonight, the on-off button in the cap doesn't work right on this host, only acts as a momentary switch. Holding the host, pushing the button and taking a photo with my iPhone at the same time is quite a task. I have to spend some time to figure out why and fix the switch but having too much fun playing to do so yet



I did some trouble shooting regarding the "wings" or splash left and right of the spot and found they existed with or without the S1 lens inside, only when I went to a 3 inch diameter PCX lens would they disappear! Strange! Unfortunately, the focal length of the bigger lens is longer so it won't work with this helical focuser without adding a longer extension tube but due to the expansion of the beam prior to collimation, it needs to be funnel shaped so as not to cut off any of the hard earned output power before getting to it.

If I took off the beam expander and focused the beam on solder, it would melt, but I imagine there would be some bright reflections I wouldn't want to look at without laser safety googles on for 445nm.

Edit: Got rid of the splash wings using a 2.4 inch diameter lens with a little longer focal length, fortunately, the range of the helical focuser would allow me to have enough adjustment to get to infinity with enough left over for short or long distance zooming too. I have a huge selection of hundreds of lenses to choose from, so isn't too difficult to find the right match. Thank you ebay for the deals I've been able to find over the last two years buying up lenses when the price was right. Sometimes you can find a hundred lenses from someone who has been collecting for years and wants to off load them for cheap.

Note: only about 1.8 inches of the 2.4 inch PCX lens is being used, the diameter of the tube cuts off anything larger than about 2 inches from exiting the tube but for some reason, a larger diameter lens, even if you aren't using all of its aperture will focus much better without splash than using a lens which is the right diameter for the clear aperture of the tube. Hoping someone who might know why will chime in and post the reason.

Pointer with the larger lens on it:





Here's a photo of a plano-convex cylinder lens I rubber cement glued over the S1 lens, once I had it's adjustment right. This simple lens helped square up the rectangle shaped output to a much fatter rectangle, close to a 2X widening of the thin/slow axis. Not the square output I'd like, but closer to it with minimal corrective optics, only loosing an additional 30 mw of output power.



This photo, below, shows the output after the cylinder lens was inserted in front of the S1 lens, if I didn't have that lens in there the output would be half as wide in the slow axis and more of a stripe shape. The light was so bright it washed out the photo so much I had to adjust the saturation and contrast to make the shape of the output stand out better:



There is a slight twist to the shape I could fix, but I don't want to have to remove the cylinder lens from its glue, twist it a tiny amount and glue it back down again, good enough for me.

The beauty of this kind of beam expander is you can use it with a normal G2 type of lens found on most pointers, just defocus its output so the diameter of the beam is close to the diameter of your PCX lens on the end of the tube, adjust to its focal length and whala, you have a beam expander focused to infinity. The position of the G2 lens can affect where the focal length will be for infinity focus, some adjusting to find the right trade-off between filling most of the aperture of the lens and infinity focus will probably be needed. If you defocus your G2 lens too far, some of the light will be cut off from exiting it, so there is a limit for how far you can defocus that lens but I've found there is plenty of room for output collimation PCX lenses which are several inches in diameter, although the smaller the PCX lens, the less you need to defocus the G2.

The adjustable focal length of the helical focuser is from 50 to 90mm, but with the G2/S1 lens adjusted out of focus, I've found longer focal length lenses work well with the unit. I have a 125mm FL lens on the end of the focuser which is working perfectly with the combination of the G2 out of focus lens to reach infinity with plenty of extra play on both ends of the range. That is when using a lens which is quite a bit larger than the aperture, so it's hard for me to give advice on which lens to get if you want to build one of these. Also, there is an extension tube you can unthread which I am using to reach the FL of my lens, without it, I would need a much shorter FL but the extender tube comes with it, if you buy it.

Here's a link to another thread showing a LaserGlow 10X beam expander on this same model by LPF member Minamoto Kobayashi but his is all black, wish mine was:

http://laserpointerforums.com/f40/z...9w-modified-hercules-beam-expander-91215.html

My 18650 batteries are good but drain kinda fast, better to use 26650 batteries with the NUMB44 diode.

PS: With freshly charged batteries my pointer is putting out 6.0 watts after lens losses, mine might not be so cool looking with mismatched colors, but it's more powerful :wave:

Very interesting :drool:... I'm a little bit jelaous :na: .. but I think the pointer will be very unbalanced toward the aperture, right?
I had many experience with the LG BE, and You are right: it is very important to found the correct input divergence to avoid coating damage, to have the minimum power loss, the correct gap from min to max focus distance and without cut part of beam.
Just a curiosity: I do not know S1 lenses: they are similar to the G2? Have You also tried the G9?

Hello friend,

I have some G9 lenses, but haven't mounted them in a barrel yet to try them out. Yes, the fast axis side is unbalanced, but you can't see the divergence in that plane expand any faster than the other at the amount of expansion they both have. S1 lenses are, in my opinion, no quite as good as a G2 because mine produce a little bit of splash but the power loss measurements show they are slightly less loss than a G2. They are nearly identical, just some G2 copy cat lenses made in China which were bought in a group buy through LPF last year for cheap.

edit: Tonight I took some time to confirm that both the fast and slow axis of the rectangular output focus to infinity together and was surprised to find that they do not! They are somewhat close together when you focus one or the other, but on close inspection one side is not focused to infinity when the other is. A good reason to try to correct the beam to as close to round as you can get so both sides focus together.

Ehm LOL .. I mean unbalanced talking about the weight of the head+beam expander Vs the rest of the laser body

It looks way unbalanced that way, but it really isn't, mostly air inside that end. When handling it I don't notice anything heavy about the business end of the laser at all. The heavy duty thick walled host and batteries keep that end of the stick heavy, I just wish I had 26650 batteries in the tube instead of 18650's which drain down faster than I'd like.

Edit: I found the balance point, it is exactly in the middle behind the fins on the head. If you hold it near the knot in the middle as in the first photo I posted in this thread, you don't notice any extra weight on the lens end.

That's a pretty darn neat project, especially considering you just "threw it together!"

I've been buying way too much laser stuff on ebay, buying parts I need for projects in parallel instead of in series, or completing a single project first before buying parts for the next... this leaves lots of stuff to choose from.

Hi Alaskan.
Do You think that this item:

New Adjustable Extension Tube for 1 25" Telescope Eyepiece T Rings and Scope | eBay

... will be a good extension to found the correct distance between the two lenses?

Since the adjustment range is so wide at 34mm ( from 113mm to 147mm ), if you found the right lens it certainly should work but not sure how stable it will be compared to a threaded zoom mechanism, I like the helical zoom because it has such a smooth movement. They make a smaller helical zoom, if that is what you are looking for:

New 1 25 inch Double Helical Focuser 0 1mm Scale for Telescope Guider Precision | eBay

By the way, it just happens that earlier today I bid on the same kind of adjustable extension tube you are asking about, but the 2 inch size, if I can get it cheap enough, I am going to give it a try myself.

Edit: I just edited this same statement into an earlier post in this thread where I said both the fast and slow axis focus to infinity together, tonight I looked close and found they don't! Best to correct the beam to as close to round as you can get if you want to focus all of the power output to infinity.

Another beam shot, this one with the new lens using my iPhone, no time lapse needed:


See that little bit of spreading on the end of the beam where it fans out slightly? I think that is due to the opposite polarity fanning out some due to being unable to perfectly focus both the slow and fast axis outputs to infinity together. I'd love to see the beam from some of these 6W blue diodes knife edged together to produce 3X or more the power through an expander!

The big lens is biconvex?
Surfing in internet I saw that the perfect focus in one point is reached only with that kind of lens:



while the plano-convex cause this:



Besides this, I think that a 2 lenses beam expander system may be less effective of a three or more lenses system.
I saw a similar problem with the Jetlaser (Keplerian) beam expander.
I found the best results with my three Laserglow (Galileian) beam expanders, that mounts three different kind of lenses. And before the BE, there is a three elements glass lens, so I have really a big control over the beam :beer:

All of the lenses I use on these simple but imperfect beam expanders are PCX, or plano-convex. I have tried the lens both ways as far as which side, the flat, or the round side, is facing the laser diode and always choose to use a configuration where the flat side is pointing towards the diode. Just seems to make a nicer close in spot, perhaps it is better to have it the reverse for a better long distance beam, but I can't see that far out to see what it is doing

Thanks for sharing your ideas and findings, I will turn the lens around and see if the small amount of fanning still exists at the end of the beam that I can see, but I still think that is due to being unable to exactly match the infinity focus for both the fast and slow axis of the diodes output, since the pattern is a rectangle shape.

Hi.
I have just bought this:

Linos Zoom Beam Expander Telescope for 532nm Laser 2 8x Expansion Rodenstock | eBay

It was a real deal, because new it cost about 1000 dollars!
I contacted both the seller and the company that sell this expander,
and I learned much things about it!
It has 4 lenses, it is Galileian type, has two kind of regulations (beam diameter and beam divergence), professional lenses and professional coating (this one for the 532nm), and it is in excellent condition.
It was originally mounted on a professional engraving machine.
In general those beam expanders are not designed for focusing the laser. A typical application looks like this:




this expander is perfect only for the mid/long focus.
Focusing near the aperture is done by a special focus lens (F-Theta or Focus Ronar). The beam expander can be used to make some fine tuning on the focus layer after the focus lens. But in general it is not used without this focus lens. Magnification and divergence hovewer are not fully independent. The design is diffraction limited, therefore I should not experience any beam quality degradation.
My idea is to use this expander with another simple focusing mechanism before the expander (G2 or 3 elements), or with another big lens after the expander: in these scenarios I should obtain different gap ranges.
If my idea works, I search for an identical BE like this, but suitable for the 445/470nm.

Very nice, I also have one of those, the same model, but I have not used it for anything. I think I probably paid 200 for it about 2 years ago on ebay too.

Sorry, pic added.
But .. why You haven't used it yet?
Ok, now it is a job of mine :na: