New Mitsu P73 quad build

[drm916]

Pretty cool mounts. I have tried building a p73 setup and centering the diode to the lens is a big pain in the butt. I finally gave up trying to get them centered perfectly.

[buffo]

Speak with Bob Snyder (CDBeam here on PL). He has a new mount design that is a SNAP to align. He's got a full set of drawings too. Just need to find someone with a mill to make you a couple.

The LDAM V.7 was specifically designed to work with the Mitsubishi reds and the tiny 2 mm aspheric primary lenses. Of course, they can be used with any diode, but the alignment issue is most crucial with those small lenses and the Mitsubishi 637 nm red diodes.

Adam

[MountainGoat]

This post is primarily focused (no pun intended) for Planters and Logsquared, but of course anyone is welcome to comment.

They say your posts may stay on the Internet forever, so hopefully sharing my proposed design and ignorance won’t haunt me too badly.

I too am working on a multi-red knife edge array using the 500mw ML501P73-02 Mitsubishi diodes. The array/ projector is intended for both graphics and beams, thus I’m trying to clean up and align the beams as best as possible.

The diagram below is basically what I am thinking (though it will be an incremental build as my budget allows.)

Many of the specs I’ve listed here are from TechIngredients YouTube video, though I suspect Planters is this fine engineer I’ve seen on YouTube.

A few notes for clarity:
- I’m planning on using diodes already mounted in those copper/ aluminum cylindrical mounts commonly available off ebay (e.g. from dtr-lpf). This just seems easier that soldering and installing individual diodes into the various brass diode housings also available on eBay (albeit this is likely a more expensive approach.) I also through adjusting the rotation would be easier using these pre-mounted diodes.
- I am planning to include the G2 lens (installed in the mounted diodes) as I suspect they’ll contribute to cleaning up the beam, but without experimenting I’m not certain whether they are necessary.
- The beam path is just an illustration and divergence is not calculated, though the lens focal lengths are to scale so perhaps the illustrated beams are not that far off.


Here are the questions or uncertainties I’m struggling with:

1) Should I need to correct each individual diode with cylindrical lenses before knife edging them together, or could they perhaps be knife edged and then corrected?

2) Am I correct that the diode mounts need to be staggered (as illustrated), such that all the diodes will be the same distance from the correcting optics (and spatial filter)?

3) Are brass tilt/ tip mounts with right angle prisms sufficient for the knife edge? I understand heat management is a concern, but I’m hoping to manage this with the cooler Chamber TechIngredients suggests in his builds.

4) For the wave plate, should I be looking at a “zero order” or “multi-order” plate? I’m not clear on the difference and which is normally used. I do understand that cheap mica plates are not up for this task.

5) Any other issues, concerns, or suggestions you’d have for me?


Oh, and lastly, one more design question:

Since a wave plate can set the polarization of a beam, has anyone tried ganging up multiple dual diode/ PBS arrays with wave plates? (i.e. Two diodes at 90 degrees into a PBS, take the resulting combined beam and shoot it through a wave plate to align the polarization in one direction. Then take another dual diode/ PBS array, shoot it through a wave plate (oriented at 90 degrees to the over wave plate) and combine the output of the two wave plates using yet another PBS.)

I can submit a drawing if my description makes no sense.

My thinking is that this would provide a tighter beam than what knife-edging creates, but at the obvious expense of multiple wave plates.

Anyway, would this work? Why or why not?

Thanks everyone, and special thanks to Tech Ingredients (I’m still assuming this is Planters) for his very educational videos on YouTube. It’s very generous to share his experience and knowledge in this manner.

-Mountain Goat

[planters]

Mountain,

I looked at your diagram and based on the power output of your green and blue sources, I recommend decreasing the number of P73 diodes, a lot. If you are going to go the boxing and cooling route as I do in all my projectors then two diodes will be enough. By driving these diodes hard @ around 1.4 -1.5A you will get nearly 3W of very bright 625-630nm light. This will likely be more than enough to balance the green laser in your set up. The advantages of a dual are numerous. Firstly, the red lasers have the worst beam quality and divergence and once you use more than a polarization combined dual, the beam will become proportionally larger or the divergence will worsen. Secondly, aligning more and more diodes becomes more difficult to achieve and to maintain and because of the unavoidable spacing that even the best knife edging requires, a quad beam will be MORE than twice the size of a dual. And thirdly, the cost of the drivers, lenses, mounts, mirrors, TEC's and housings will well exceed the cost of the diodes themselves. It makes more sense to risk a few overworked, $40 di0des (I haven't lost one yet..knock on wood) than build a $1,000, 8 diode array.

I have learned a few things about cooling these diodes. A three stage TEC can be assembled easily, but to optimize the performance, set up each stage to be driven independently, by a lab power supply once the dual is enclosed and running. You can fine tune the driving current to each stage and this will improve the cooling effectiveness significantly. Once known, the appropriate currents can be delivered by the projector's power supply(s) by inserting appropriate resistance loads in series with the TEC to lower the delivered current. I do not regulate the cooling. It is allowed to run down to equilibrium. Take a look at the new, self contained water cooling systems for CPUs from a company like Corsair. These are inexpensive, don't leak and are way,way better than any air cooled heat sink system I've tested (I've tested a lot). They're also quieter.

I will be doing a video soon that highlights some of this information, but I am waiting on new scanners from Pangolin and EMS before I do this.

No, you can't cheat the system and use series polarizers to continuously add in additional lasers. Each additional polarizer rotates the electric field of all the beams that pass through it, even those that have been rotated previously and so the best you can do is to overlay one beam onto another by aligning their electric fields at 90 degrees to each other. Any intermediate angle, whether less than or more than 90 degrees,will simply fail to pass through the polarizing combiner at a rate that is proportional to its rotational angle from one of these two primary beams.

[MountainGoat]

Thanks so much for the reply Planters.
The other lasers were kind of place holders, but I like your comments and think I'll follow your suggestion... Maybe do a larger projector later.
For the liquid coolers, have you had luck placing a corsair cooler under your cooling chamber and just using thermal compound to link the corsair cooling plate to the base plate that the diodes are placed on?
I started looking at liquid cooling technologies and there were some devices for cooling hard drives that looked like they might adapt well for my purpose, but the Corsair CPU coolers look easier to setup assuming they can chill the cooling chamber suffiently.
Any more advice would be appreciated, and I'll watch for your next video too.
Thanks so much.
- Mountain Goat

[planters]

Mountain,
If you do decide to upgrade the green and blue, I think you will still be happy with a dual red with as much as 2.5W of green and a typical 4W dual m-diode blue. Beyond this point, the green will cost about $2,000 for a 4W and a dual 9mm blue with 5-6W will be easy to switch for the lower power m-diode if you want more blue as well. The limit I have found has been the quantity of green in these higher power ranges.

The CPU design works VERY well by simply screwing the cooling head to the underside of the plate near the location of the TEC stack. Even with multiple Zalman crown style coolers mounted under this plate and multiple high speed case-cooling fans ventilating the lower level the optical plate would still get a little warm (35? degrees). With the water cooling I can't tell when the cooling stack is on or off! With this setup I can hit -40C at the diodes and actually back off to prevent the reds moving too far toward the orange.

Be aware that the cooling tubes between the radiator and the head are very stiff and pretty short. Buy one before you engineer how you plan to mount the components. Also, include an on/off switch for the cooling stack so that you can run the reds and the projector at RT, without the enclosure, to align and focus the diodes. They don't then defocus or misalign when cold, in the designs I have shown in the videos.

[MountainGoat]

Thank you again "Mr Planters", I really can't express my appreciation for your thoughts and the videos you've shared with the community.

I may follow up with some more questions if you don't mind, and I will keep the community posted with my progress and any learnings.

Mountain Goat

[drm916]

Planters

If not cooling these diodes aggressively and only letting them run at ambient (plus a small fan to move air across them), how much power do you think we can extract out of 2 combined with a PBS?

[planters]

I think you can produce 2W with the same margin of safety. This is allowing for combining losses prior to the 2W output. You will probably be producing near 642nm at that current and therefore the red will look about 1/2 as bright as with aggressive cooling. I am making these estimates based on the tests where I measure the efficiency gains as well as the wavelength shifts as they cool.

[drm916]

I think you can produce 2W with the same margin of safety. This is allowing for combining losses prior to the 2W output. You will probably be producing near 642nm at that current and therefore the red will look about 1/2 as bright as with aggressive cooling. I am making these estimates based on the tests where I measure the efficiency gains as well as the wavelength shifts as they cool.

Seems like it makes more sense then to not over drive them as much and run less power, lower temps and a lower wavelength. No good reason to run more power with less brightness.

Thank you for your input.