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Optically corrected pen: MM 638 V1

RA_pierce

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I've been planning this project for a long time but finally had some time to get around to setting it up today.

The idea: Make a tiny, optical correction assembly to improve the beam quality from high power multimode diodes while minimizing losses and cost.

The materials:
  • HL63193MG 638nm Diode
  • 6mm cylindrical lens (AR coated for 633nm)
  • 25mm cylindrical lens (AR coated for 633nm)
  • Flexdrive V5
  • Spare parts

Phase 1: Proof of concept

There are a few hurdles to overcome with this project.
The first is that I don't own my own metal-working tools so I am limited to scraps from disassembled modules and basic tools one might find in a relatively well-equipped garage.
After rummaging through my spare parts box, I found a few pieces I could put together with a little modification to get an adjustable otpics assembly.
The second hurdle is finding the right optics. I went to Edmund Optics and selected a couple lenses that would provide decent correction for the average divergence specifications given by the datasheet for the diode. This required some algebra, a little trigonometry, and less physics. The basic idea is to select focal lengths that provide the same ratio as the divergence angles of the diode's emission axes.

Once I had the materials in hand, it was just a matter of finding the time and doing the work.
The design is crude but effective.
The diode is seated, for now, in a threaded mount so that it can be removed or rotated if necessary.
The first lens is mounted on a threaded ring in a brass tube that threads onto the diode mount.
The second lens is also mounted on a threaded ring in a brass tube that is connected to the first lens assembly by another threaded ring.
That's it.

This design allows me to adjust the z-position of each lens relative to the diode by threading in or out the ring that the lens is to be mounted on.
The lens rotation and x-y position can be adjusted freely. This part is tedious and difficult.
To ensure a good alignment, I first mounted the diode and powered it up above lasing threshold (around 40mW) then redirected the output to an adjacent wall with a first-surface mirror.
The z-position of each lens was set first by crudely aligning the lenses one at a time to achieve the smallest divergence angle at the other side of the garage.
I marked on the wall what I could approximate was the center of the beam profile with a marker. For each lens, I would target this mark for the center of the beam when making adjustments to the x-y position.
When positioned, I applied a small drop of UV-cure liquid plastic to set the optic in place. This required a lot of patience and a steady hand but the process is simple.

Results:

I achieved about 1.5mRad divergence on the fast-diverging axis of the diode.
Unfortunately, while setting the lenses with epoxy for a more permanent hold, I had to disassemble the optic mounts. When I put it back together the second lens had shifted somehow and the divergence is around 2.5mRad on one axis now. This will be corrected for the second iteration of this assembly when it is ready to go into a host.

Addendum 5/28: After adjustment I'm getting approximately 1mRad measured at 20 feet for the fast-diverging axis.

The module as it is now, is about 35mm long which can be shortened by a couple millimeters by clipping the diode pins. It may be possible to achieve a total module length of about 40mm with the switch board included. I will try my best to keep the size small so that it can fit nicely into a pen.

After alignment, I increased the power a bit to check losses to the optics.
The raw output from the diode (no optics) was 200mW. After both correction lenses, I was getting 150mW. This comes out to about 25% loss which I think is quite good when considering that these lenses ended up being a bit too small to collect the entire beam (the divergence of the fast axis is a bit higher than specified on the diode's datasheet) and that the apertures at the first lens cuts off some of the output as well.
400mW is easy to obtain with this setup (and it's bright!).

What I learned:

One issue I have is that the mounting method for this diode does not provide enough heat transfer to the module. A press-fit would be much better. In future renditions, this will be possible if I can get someone to machine the parts I need. Because heat transfer is poor, power drops rapidly at high current input.

Choosing lenses with shorter focal lengths should allow a more compact design but it will be difficult to find such lenses with a large enough clear aperture that will minimize losses.

There is still some crap spilling over the main output modes after correction. This will be difficult to eliminate without spatial filtering (another project) but can be cut down a little with masking using a narrow exit aperture. I have to experiment with this more.

Addendum 5/28:The ratio of the focal lengths for this diode is not exactly right so I still get more of a line-shaped beam. I think that for the finished set-up, I'll try leaving the first lens slightly de-focused to match the divergence of both axes for more of a square beam.
Additionally, I measured the output power at 2 inches from the LPM sensor and at 24 inches. I estimate that about 30% of the total power is contained within the lobes. I'm curious to know how this scales when power is increased. I'll do more testing for that later.

The photos:

Positioning the first lens


Positioning the second lens


I can check for the presence of a positive focal point and observe the general profile by passing the beam through clear acrylic


Before optical correction


After the first lens is roughly aligned


After the second lens is roughly aligned you can see that the main portion of the output is concentrated and there is some spill from the uncollimated modes at low intensity on either side of the beam


A close-up of the profile before final alignment (slightly imperfect collimation)


A first-surface mirror can be used to position the beam in a more convenient location so the lenses can be installed vertically with the help of gravity to keep them in place


Divergence at 20 feet (markings for centimeters and 5mm intervals


A power test showing raw output power (bottom measurement) and the power after optics are installed (top measurement)


Beamshots. The perspective exaggerates the beam size but divergence is lower than with 3-element glass lens





Phase 2: Fine-tuning and assembly into host

Because of the heat transfer issues I was having, I took the module apart and set the diode in a regular ol' nickel plated brass Aixiz module.
This improves heat-sinking but has some drawbacks.
First, this makes it a little more difficult to install the first cylindrical lens within the narrow space of the Aixiz module aperture.
Second, I would need spacer tubes threaded for 9mm lens holders to allow me to make the module long enough for correct placement of the second lens. To get these parts, it took a few hours of manual sawing, filing, sanding, fitting, re-filing, re-sanding, re-fitting, then more testing...
There is also a third issue that I haven't addressed previously but I have a solution for already. The module length extended past the length of the leadlight host. I couldn't leave it that way as it would look unfinished and a little ugly.

Optical Assembly:

Lens 1: I took an old 9mm threaded lens ring from a 3-element lens , then filed and sanded the surfaces flat and smooth, and removed burrs to prevent scratching the lens.
Because the lens must be positioned close to the diode (4.55mm), I couldn't easily mount the lens on top of the lens mount. Fortunately, the lenses I purchased are the same diameter as the lenses that go into the 3-element lenses. This allowed me to drop lens 1 into the mount, adjust the height and then rotate it to correct the fast-axis properly.
While this simplifies the setup process, the centering is not perfect and is unfortunately not adjustable this way. It is close enough for me, for this prototype.

Lens 2: To mount the second lens, I sawed off the diode mounting socket from a couple of Aixiz modules, filed and sanded the surfaces flat and smooth, and removed the burrs. This produced two 12mm M9x0.5 threaded tubes Next, I took another 3-element lens holder and cut this one in half.
Of these two pieces, one would be used to join the module pieces together and the last one would be used to mount the second lens.
I'll save the explanation and update this section with a drawing.

After all the parts were verified to fit together, I started assembling the optics.

Part of the complication introduced by this design is that the first lens mount also serves to join pieces of the module together. This means that when the second module spacer tube is threaded on, it introduces a little rotation to the lens mount. To get around this, I used teflon tape to tighten the threads around the section of the lens mount that would be installed inside the module containing the diode. This minimizes rotation of this section while allowing the spacer tube to be threaded on freely.
I also installed the lens mount a quarter-turn short of where it needed to be so that when the spacer tube is tightened down, it makes that last quarter turn of the lens mount and gets it into the right place. This took a lot of trial and error to get just right.

Once the first lens was in position, I bonded it in place by carefully applying a tiny amount of bondic to secure the position instantly and then 2-part epoxy for a more permanent hold.

The second lens was easy. Because it protrudes from the module, access is good so its position can be adjusted easily in all directions.
The setup was essentially the same as in Phase 1.

With the optical assembly completed, that just left wiring up the driver for installation in a pen host, assembling all the little bits for that, then fitting it into the host.

Final Assembly in the Leadlight host:

To make the module as short as possible, I cut off a few millimeters from the back portion of the module (the threaded tube that threads onto the back of the diode socket). However, because this leaves an open tube, mounting the switch board assembly is a little harder with less surface area to bond everything with epoxy.
To mediate, I found a piece of plastic in my spare parts bin that had a "lip" that fit right into the back of the module. I trimmed it to 12mm diameter and epoxied it in place. This would provide more surface area to bond with the module back and provide a more secure bond with the switch board assembly (plastic-plastic bonds more strongly than brass-plastic especially between two flat surfaces). This is shown in one of the photos.

One thing about this build that turned out quite nice is the amount of mass contained within this pen. Because I am using these cut up Aixiz modules, there is a lot more metal available for heat-sinking than with the previous setup using the wider brass threaded tube. The laser feels heavy and I think all that metal helps move the heat away effectively.

As I mentioned several paragraphs ago, one issue with this module is that it's too long for the host. It protrudes almost exactly 10mm.

The solution for this is simple: hack off a section of another Leadlight host and stick it on top.
That's what I did. Of course, I took care to make sure the sawed surface was flat and flush. I did this for the 532nm aspheric pen I put together a few months ago (I still haven't showed that one off yet).

There's not much more to say about it. I crammed everything together then buffed out the smudges and put a sticker on it.

Voilà!

Photos, then final details follow:

The module. I have the knurled focus ring on there just to protect lens 2 which would otherwise be exposed.


The switch board assembly and the plastic spacer to get a stronger bond to the module




A comparison with 150mW 638nm single-mode (right)


The newest addition to the collection


In case you were wondering about what some of these other lasers are:
638 MM, 450 SM, 495 SM, 488 SM, 638 SM


Here's a view of the beam profile.
The "wings" are quite pronounced but there's no easy way to get rid of them in this setup. I think it gives this laser a unique character.



Summary and final thoughts:

Divergence (corrected fast-axis): 0.9mRad
Divergence (G- lens fast axis):
Power output: 400mW peak
Loss to optics: 25%

This build was challenging but a lot of fun.
I think that the optical correction done here is quite effective, though, depending on what you expect and want from a diode like this, the results could be disappointing.
While the corrective optics do substantially improve the divergence of the output from these notoriously bad red multimode diodes, a lot of the total power is lost in the lobes that extend beyond the "main beam." Some might call it ugly and I can understand that. However, it's about what I expected and now that I have this thing all put together, it really doesn't bother me.
"It's a different type of laser," my girlfriend says.
It's true. We have a bunch of cool stuff available these days and it seems there is a lot of discussion surrounding correcting the "artifacts" or improving the beam quality from the less-than-perfect diode lasers. But I think if you can appreciate the weirdness of the engineering and physics that go into making these, by appreciating the unique aesthetic of each type of laser, you'll find that there is another aspect to our laser collections that is underrated: the variety of beam types.
 
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DTR

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Very nice work. Maybe just look at adding a little cap for the spacial filtering to block the last remaining stray light leaving just the little cube/dot.:beer:

If you have any of the ball lens cans removed from a NUG/NUB diode try knocking out the glass lens and see if sticking that on the aperture will work. Played around with that once to clean up the spray out of a three element lens on one of these diodes with some success as the lip sat nicely between a three element lens and the focus ring when screwed together and the tube was just narrow enough and long enough to grab a lot of it. Never got around to mentioning it but this just reminded me.:beer:
 

trinh hong phuoc

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great work-As DTR said-you needed something to block the extra light-that would be better
 

steve001

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An option regarding the threaded lens rings. Once in your possession accurately measure with a digital caliper the diameter of each lens. Then find a member that will machine two rings with a slightly recessed inner depth and slightly wider width than each lens diameter to help with precise centering. An option to the uv adhesive is Beacon 527 adhesive. This is a good adhesive because it holds securely yet if you choose or need to remove a lens sometime later you can without a solvent. It comes off without leaving any residue or damaging the AR coatings. I see apparently you choose round cylindrical lenses. A good choice, but why?
 

RA_pierce

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If you have any of the ball lens cans removed from a NUG/NUB diode try knocking out the glass lens and see if sticking that on the aperture will work. Played around with that once to clean up the spray out of a three element lens on one of these diodes with some success as the lip sat nicely between a three element lens and the focus ring when screwed together and the tube was just narrow enough and long enough to grab a lot of it. Never got around to mentioning it but this just reminded me.:beer:
I've never used one of the NUG/NUB diodes so I'm not sure what the cans look like. Is it rectangular or round?

great work-As DTR said-you needed something to block the extra light-that would be better
Right. It can be difficult to clean up the beam in a short distance.
I may ask you to make a few parts for me to help this project along.
I'll be in contact.

An option regarding the threaded lens rings. Once in your possession accurately measure with a digital caliper the diameter of each lens. Then find a member that will machine two rings with a slightly recessed inner depth and slightly wider width than each lens diameter to help with precise centering. An option to the uv adhesive is Beacon 527 adhesive. This is a good adhesive because it holds securely yet if you choose or need to remove a lens sometime later you can without a solvent. It comes off without leaving any residue or damaging the AR coatings. I see apparently you choose round cylindrical lenses. A good choice, but why?
Thanks for the recommendation for the adhesive. I'm using Bondic which works to set things in place but will break if handled firmly. This is good for this type of project where I am likely to make mistakes but it isn't so good for permanent fixture.

I chose round lenses because the dimensions fit within the 12mm module space and because mounts can be manufactured for them with a lathe if needed. This reduces the complexity, cost, and accessibility of a more tailored assembly (if I pursue it).

Thanks for the feedback everyone. This is a really fun project and I can't wait to continue work on it. :beer:
 

paul1598419

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Rather than using a spatial filter, I think masking will work fine for eliminating the splash you have left over after alignment. I think the circular cylindrical lenses are a good option as you need only worry about rotation instead of pitch and yaw of the rectangular cyls. You will have to press any diode you use in the future, otherwise you can't move waste heat away from the LD fast enough. Great first effort.
 

Benm

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Very nice work!

The end result does have some sidelobes to it, but i wonder how much power is actually in those - it could only be a tiny amount. One way to measure that would be to make an aperture (say a hole drilled into a small L shaped piece of aluminium stock) and compare power measurements with and without that in the beam path.

A more interesting thing would be to take a picture of this laser shining on a far away (say 100 meters?) target - it would probably still have those sidelobes, but they could be so dim they're hardly noticeable at that point.
 

RA_pierce

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Rather than using a spatial filter, I think masking will work fine for eliminating the splash you have left over after alignment. I think the circular cylindrical lenses are a good option as you need only worry about rotation instead of pitch and yaw of the rectangular cyls. You will have to press any diode you use in the future, otherwise you can't move waste heat away from the LD fast enough. Great first effort.
Masking will be difficult. The "lobes," as Benm calls them, diverge rapidly but not appreciably within a distance at which I would want to have a masking aperture, especially for a handheld build. A mask at this distance would waste some of the output I want.
I don't intend to apply spatial filtering to this build as it adds additional complexity and size but I haven't come up with any alternatives.
Yeah, I'm surprised by how poorly the mount I'm using is for moving heat. It's enough to run this diode up to 200mW but beyond that it gets problematic.
I need to redesign the first lens assembly so I can have this diode properly mounted.

Very nice work!

The end result does have some sidelobes to it, but i wonder how much power is actually in those - it could only be a tiny amount. One way to measure that would be to make an aperture (say a hole drilled into a small L shaped piece of aluminium stock) and compare power measurements with and without that in the beam path.

A more interesting thing would be to take a picture of this laser shining on a far away (say 100 meters?) target - it would probably still have those sidelobes, but they could be so dim they're hardly noticeable at that point.
Thanks!
Yeah, I'm curious, too. Clearly some of the 25% loss is due to the lobes since the raw power measurement included as much as the beam I could fit on the sensor straight out of the diode.
The lobes are bright enough to show up at 10m but I haven't yet taken this outdoors to experiment at longer distances. I'll have to readjust everything to the optimal alignment again before I do that.

I am having trouble visualizing the aperture you describe.
I could try measuring power at a close distance so that most of the lobes fall on the sensor and then again at a greater distance so that very little of the lobes are measured. However, I don't know how much heat from the close distance measurement will bias the results. In my experience it doesn't seem like the thermopile sensors are so sensitive that my hand at 10cm is a problem.
 

paul1598419

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If the splash is no big deal for you, then I agree. I have some lasers that have splash. I doesn't bother me at all. My point was masking was a better option than spatial filtering. Good luck with this build. I'm very interested to see how you over come some of these issues and get it up to full power.
 

Benm

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Masking will be difficult. The "lobes," as Benm calls them, diverge rapidly but not appreciably within a distance at which I would want to have a masking aperture, especially for a handheld build. A mask at this distance would waste some of the output I want.
I don't intend to apply spatial filtering to this build as it adds additional complexity and size but I haven't come up with any alternatives.
Yeah, I'm surprised by how poorly the mount I'm using is for moving heat. It's enough to run this diode up to 200mW but beyond that it gets problematic.
I need to redesign the first lens assembly so I can have this diode properly mounted.



Thanks!
Yeah, I'm curious, too. Clearly some of the 25% loss is due to the lobes since the raw power measurement included as much as the beam I could fit on the sensor straight out of the diode.
The lobes are bright enough to show up at 10m but I haven't yet taken this outdoors to experiment at longer distances. I'll have to readjust everything to the optimal alignment again before I do that.

I am having trouble visualizing the aperture you describe.
I could try measuring power at a close distance so that most of the lobes fall on the sensor and then again at a greater distance so that very little of the lobes are measured. However, I don't know how much heat from the close distance measurement will bias the results. In my experience it doesn't seem like the thermopile sensors are so sensitive that my hand at 10cm is a problem.
It's not your hands that are an issue here.

What i propose is shining the laser onto the power meter without any obstruction, and then through some hole that fits the 'main beam' but blocks those sidelobes to see the difference in power.

Although well visible those sidelobes may not contain that much of the total light - if you just lose a few percent in them the long range result would be very good.
 

CDBEAM777

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Well...another project that attempts to tame the 63193 LD....It is a Bitch of a LD !!

See the " Dragon's Head Build" in my sig !!

No one has attempted to do this on such a small scale !!! Bravo for that !!!!!

To tame the 63193....at all....is a high goal !! And without a Machine shop at your disposal !!!!! Yikes !!!! I am surprised at the good result you obtained !!!

Sooo...let me throw in here !!!

Firsty...I understand why you choose the round Cylinderical lens set....ease of mounting....but....in using any set of Cylindrical Optics....well....we must solve several problems....ALL at the same time !!

1) The beam....as it enters the first lens ( Round or rectangular ) must be in the exact correct radial orientationn. So....one can rotate the LD....or rotate the Round PCV. In your case...you rotated the PCV lens to accomplish this alignment.

2) The distance (Z axis) between the first Cylindrical -PCV, and the second Cylindrical lens PCX is absolutely critical to obtain maximum slow axis magnification....and therefore derive minimal divergence on the slow axis.....and achieve the most compact Far Field geometry we can obtain.

3) The position of the second Cylindrical Cylinder(PCX) must also be in the correct radial orientation to the first Cylindrical PCV.... for the Cylindrical pair to work properly.

All these things must be darn near perfect....or aberrations, wings, or lobes....call them what you will....will be present.
Even with perfect positioning....vertical wings will be present...below and above the main spot ( Read round cornered rectangle ).

How do you set the Z axis distance ?? If I read correctly, you screw...in/out... the second Cylindrical PCX lens retainer barrel...to get the least divergence. Since the PCX is not yet fixed....you can then rotate the PCX lens to achieve the optimal Far Field beam geometry.

I assume....by trial and error.....you satisfy the three (3) conditions I stated above....then epoxy it in place. What a PITA that must be !!!!

While I understand why round Cylindrical lenses were chosen......at least with rectangular Cylindrical lenses....you know that...If ya set the lenses on a flat base....the correct radial orientation is automatically achieved.....and then...you must achieve all the other conditions !!

Problem is that rectangular Cylindrical Lenses would likely take up some more space....and a Machine shop would be demanded to achieve a Flat Ledge design for the C-Lenses.

I know....Always a stink'in critic...SORRY....I have dealt with these optical demands for many years....and....just would like to help !!

Now...On to the question asked by Steve001....what is the separation distance between the Collimation lens and the first Cylindrical lens (PCV).
This is an important dimension !!

The closer one positions the Cylindrical set to the Collimation lens output.......the smaller the Near Field footprint presents on Cylindrical lens set....especially on the second Cylindrical Lens PCX.

If you are having an issue with getting all the Near Field Beam geometry to fit on the Cylindrical Lens pair....then keep this distance to a minimum. But...I assume with such a small build....the distance measures at about 10mm.

Finally, You do not state which Aspherical Collimation lens you are currently using ?? This is really critical !!! You must use the special lens from Laser Show Parts. This is a 2mm EFL lens. Email LSP / Dave. Advise him you need this lens, epoxied into the Brass Retainer barrel !! I have done the epoxy setting DIY....Forget it....have Dave do it....for the lens....is really small...about 3.5mm in diameter....and also a real PITA to fix !!!

This is the only lens I use when working with the P73 or 63193 LD. This lens is critical to taming the 63193 !!!!

Good Luck. If you are not using the 2mm EFL Coli lens....once you do....the beam will be truly be tamed.

Oh....and yes....mask the output to reduce the vertical wings. Just pass the beam thru an oval horizontal slot just down beam of the Cylindrical set.

I have shared all I know. Hope it helps. Keep us advised !!

CDBEAM
 
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RA_pierce

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What i propose is shining the laser onto the power meter without any obstruction, and then through some hole that fits the 'main beam' but blocks those sidelobes to see the difference in power.
I get what you mean.
I tried what I proposed in my earlier response to you and ended up with a 30% drop in power after excluding the lobes. A worse result than I hoped for.

The only way to get all of the lobes on the power meter sensor is to get the laser very close. At this distance, masking may strip off the lobes but will also take some of the "main beam" with it.
I'm not sure how else I can clarify.

How close did you place the first cylindrical lens from the diode?
The working distance of the first lens is 4.55mm.
I have a spreadsheet with all the numbers.

Well...another project that attempts to tame the 63193 LD....It is a Bitch of a LD !!

See the " Dragon's Head Build" in my sig !!

No one has attempted to do this on such a small scale !!! Bravo for that !!!!!

To tame the 63193....at all....is a high goal !! And without a Machine shop at your disposal !!!!! Yikes !!!! I am surprised at the good result you obtained !!!
...
Thank you! Yes, I have taken a look at your build. Very cool. I couldn't do the same thing (where's the fun in that?) so I thought I'd try a tiny version.

How do you set the Z axis distance ?? If I read correctly, you screw...in/out... the second Cylindrical PCX lens retainer barrel...to get the least divergence. Since the PCX is not yet fixed....you can then rotate the PCX lens to achieve the optimal Far Field beam geometry.

I assume....by trial and error.....you satisfy the three (3) conditions I stated above....then epoxy it in place. What a PITA that must be !!!!
That's correct. A PITA? Yes. But only a little pain.

While I understand why round Cylindrical lenses were chosen......at least with rectangular lenses....you know that...If ya set the lenses on a flat base....the correct radial orientation is automatically achieved.....and then...you must achieve all the other conditions !!

I know....Always a stink'in critic...SORRY....I have dealt with these optical demands for many years....and....just would like to help !!
Yes, I considered that.
As I think I mentioned, I decided against the rectangular lenses because I didn't have appropriate mounts and didn't find any that fit the dimensions I wanted to achieve. I appreciate the input so no need to apologize. Isn't that what this place is for?

Now...On to the question asked by Steve001....what is the separation distance between the Collimation lens and the first Cylindrical lens (PCV).
This is an important dimension !!
I have all the theoretical dimensions in a spreadsheet. It's a little difficult to check the actual dimensions but I'll do that and perhaps include a drawing.
I think that may help to clarify the design.
The theoretical spacing between lenses for optimal collimation (plano surfaces) is 18.5mm.

Finally, You do not state Aspherical Collimation lens you are currently using ?? This is really critical !!! You must use the special lens from Laser Show Parts. This is a 2mm EFL lens. Email LSP / Dave. Advise him you need this lens, epoxied into the Brass Retainer barrel !! I have done the epoxy setting DIY....Forget it....have Dave do it....for the lens....is really small...about 3.5mm in diameter....and also a real PITA to fix !!!
...
Good Luck. If you are not using the 2mm EFL Coli lens....once you do....the beam will be truly be tamed.
...
CDBEAM
I'm not using any aspherical collimation. Because I want to minimize - well, everything - I chose to correct and collimate with only the cylindrical lenses.
The resulting beam is not spectacular, however this project is more about doing something hard than getting a beam that'll win a beauty pageant. I have other projects in mind for that.

I added some notes to the original post including new divergence measurements and a photo of the beam profile at 20ft.
I'm getting about 1mRad on the fast diverging axis now after refining the second PCX lens position.

I really appreciate the feedback. Thanks for your comments. :beer:
 

CDBEAM777

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Raw LD output...pouring into the first cylindrical.....Holy Sh$t.....Well.....therein lies the problem of not fitting that Near Field geometry onto this very small Cylindrical lenses.

The beam slow axis is rapidly diverging....every mm down beam of the LD window !!!

I do not know what you have room for....but I would sure throw a 2mm EFL Collimation lens in front of that LD !!!!!!

I appreciate the drive to keep things small....but....elimination of the Collimation lens...is....well....unadvisable !!

Good Luck !!

CDBEAM
 

LewDude

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Sweet work - I'll be following this closely. Good luck with Phase 2!!
 

RA_pierce

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Raw LD output...pouring into the first cylindrical.....Holy Sh$t.....Well.....therein lies the problem of not fitting that Near Field geometry onto this very small Cylindrical lenses.

The beam slow axis is rapidly diverging....every mm down beam of the LD window !!!

I do not know what you have room for....but I would sure throw a 2mm EFL Collimation lens in front of that LD !!!!!!

I appreciate the drive to keep things small....but....elimination of the Collimation lens...is....well....unadvisable !!

Good Luck !!

CDBEAM
I hear ya.
The loss from that first optic is not huge. As I said, the divergence figures straight out of the diode, in reality, seem to be a bit worse than what is specified on the datasheet.
Theoretically, the small diameter lenses should have been sufficient but I didn't expect it to be perfect. I am pretty content with the beam profile despite the 25% loss to the optics (excusing the wings).

Seeing what I have here I wonder if the aspheric collimator will help a bit with the lobes/wings/whatever.

Do you report a number for losses in your Dragon's Head build?
I'll go check that thread again...
Edit: it appears you're getting just under 1W at around 1200mA.
Based on what to expect with a regular ol' lens in front of the diode, that doesn't seem too bad.

Sweet work - I'll be following this closely. Good luck with Phase 2!!
Thanks!
 
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