Double set of galvos

While watching a video about a very powerful show laser the author mentioned that the galvo mirror mirror size needed to be increased.
And unfortunately increased mirror means bigger galvos and slower. This all makes sense to me.

Then I started thinking, would it not be possible to build a laser with a double set of galvos. Mounted in the illustrated arrangement.
The output beams are offset by 6 mm which makes it possible to divide the scanning workload.

You could have two laser sources or split the beam which is less efficient.

Would I be correct to think that this arrangement makes it possible to double the power and double the scanning capability?
I mean, this is essentially two show lasers that are almost originate from the same point.

Attachment 61142
Attachment 61141

So many questions.
- Has this been done before?
- Are there better ways to do this?
- Can 2 sets of galvos from the same manufacturing batch accurately draw the same graphic with double intensity?

https://www.photonlexicon.com/forums...AASUVORK5CYII=

Yes, been done. Modern software does combine scan heads well for graphics.

They need not be as close as they are in your drawing, they may interact from air currents, internal position feedback system, and vibration.

In the last five years mirror sizes have greatly increased.

No real need to do that for beam shows, in fact, for beams it looks better if the scan heads are spaced apart. More attractive to the eye that way.

What we need these days is more angle, which is best done with lenses such as Omniscan and Discoscan, less galvo angle = more speed, and speed is life.

Steve

Wide angle I have sorted already. I designed a new mirror called Medusa https://www.youtube.com/watch?v=00KeqktfHzE
It was a huge success at our Beatline premiere two weeks ago. https://www.youtube.com/watch?v=gFUYn6QV_SI (light canopy at the end)

Ceiling creeping variants that work without haze here https://www.youtube.com/watch?v=QkVdyl4ETHY

Attachment 61143

I like the haze less version. Neat way to get around the regulatory "low ceiling" problem. It gets cold here in Ohio and a lot of clubs have very low ceilings, making obeying the 3 meter minimum height rule difficult.


FYI, your working with a "Reflective Axicon" or "Reflective Conic Section
in optics speak. I like it.

Steve

Thank you Steve,

It is great to be able to talk to experienced Laserists. I just love well timed lights to a good tune but it's rare. The idea is to do small laser shows at various venues to learn what is required in the real world.
Then take what I learned and create software and hardware dedicated to create razor sharp low lag beam shows involving multiple devices. This software is already taking shape.

Quote:

---

Originally Posted by mixedgas

I like the haze less version. Neat way to get around the regulatory "low ceiling" problem. It gets cold here in Ohio and a lot of clubs have very low ceilings, making obeying the 3 meter minimum height rule difficult.


FYI, your working with a "Reflective Axicon" or "Reflective Conic Section
in optics speak. I like it.

Steve

---

"Reflective Axicon" I like it. It makes me sound smart.

Quote:

---

Originally Posted by dinther

While watching a video about a very powerful show laser the author mentioned that the galvo mirror mirror size needed to be increased.
And unfortunately increased mirror means bigger galvos and slower. This all makes sense to me.


https://www.photonlexicon.com/forums...AASUVORK5CYII=

---

Has anyone considered using beryllium mirrors as a low mass option for scanners? They work great for space telescopes.

Quote:

---

Originally Posted by dchammonds

Has anyone considered using beryllium mirrors as a low mass option for scanners? They work great for space telescopes.

---

Hmm. Google says that Beryllium's density is roughly 1/3 that of Aluminum, and it's stronger as well. Still, the mirrors aren't the major source of weight in a scanning system, so unless we're talking about 2" aperture mirrors or something crazy, I doubt the weight savings would be enough to justify the cost (not to mention the risk of cancer if you break the mirror).

Carbon fiber would be another option, but again, I don't think the weight savings is going to be enough to matter - unless we're taking about some really huge mirrors.

If you really want to save weight in a scanning system, remove the position detection hardware that is usually mounted on the other end of the rotor (opposite the mirror). Instead, add a dichro to combine an IR beam with the incoming RGB right before the scanners, and then add a second, larger dichro to pick off the IR immediately after the scanners (and before the aperture glass). Now place 4 stationary IR detectors in a cross configuration (up, down, left, right) a short distance to the side of that second dichro to sense the position of the IR beam. Presto! You now have accurate position feedback signals to send back to the scanner amps, but everything is completely external to the scanner rotors and there are no moving parts.

Aron Bacs was one of the authors of an AVI patent for this exact technology, but due to a clerical error when they filed the patent application, they didn't include this in their claims declaration, meaning that the concept was basically in the public domain as soon as the patent was published. I'm honestly surprised that this hasn't made it's way into a commercial laser projector yet...

Adam

Quote:

---

Originally Posted by buffo

Hmm. Google says that Beryllium's density is roughly 1/3 that of Aluminum, and it's stronger as well. Still, the mirrors aren't the major source of weight in a scanning system, so unless we're talking about 2" aperture mirrors or something crazy, I doubt the weight savings would be enough to justify the cost (not to mention the risk of cancer if you break the mirror).

Carbon fiber would be another option, but again, I don't think the weight savings is going to be enough to matter - unless we're taking about some really huge mirrors.

If you really want to save weight in a scanning system, remove the position detection hardware that is usually mounted on the other end of the rotor (opposite the mirror). Instead, add a dichro to combine an IR beam with the incoming RGB right before the scanners, and then add a second, larger dichro to pick off the IR immediately after the scanners (and before the aperture glass). Now place 4 stationary IR detectors in a cross configuration (up, down, left, right) a short distance to the side of that second dichro to sense the position of the IR beam. Presto! You now have accurate position feedback signals to send back to the scanner amps, but everything is completely external to the scanner rotors and there are no moving parts.

Aron Bacs was one of the authors of an AVI patent for this exact technology, but due to a clerical error when they filed the patent application, they didn't include this in their claims declaration, meaning that the concept was basically in the public domain as soon as the patent was published. I'm honestly surprised that this hasn't made it's way into a commercial laser projector yet...

Adam

---

Beryllium is common for resonant scanner mirrors (such as CRS 8k and 12k), and for some large galvo mirrors, in the >15mm aperture range, for very high end (expensive) systems.
Novanta, who acquired Cambridge Technology, has their own Beryllium manufacturing cleanroom facility now
https://cleanroomtechnology.com/bouy...novanta-204329
We have some beryllium mirror specimens here, but don't use them for production. We prefer Silicon Carbide for those higher end applications

Quote:

---

Originally Posted by buffo

If you really want to save weight in a scanning system, remove the position detection hardware that is usually mounted on the other end of the rotor (opposite the mirror). Instead, add a dichro to combine an IR beam with the incoming RGB right before the scanners, and then add a second, larger dichro to pick off the IR immediately after the scanners (and before the aperture glass). Now place 4 stationary IR detectors in a cross configuration (up, down, left, right) a short distance to the side of that second dichro to sense the position of the IR beam. Presto! You now have accurate position feedback signals to send back to the scanner amps, but everything is completely external to the scanner rotors and there are no moving parts.

---

How about making the mirrors double sided and bouncing the IR off the back and employing 2 IR sensors for each mirror?

Quote:

---

Originally Posted by rns0504

We have some beryllium mirror specimens here, but don't use them for production. We prefer Silicon Carbide for those higher end applications

---

Less chance of getting lung cancer with silicon carbide, right? :)

Quote:

---

Originally Posted by dchammonds

How about making the mirrors double sided and bouncing the IR off the back and employing 2 IR sensors for each mirror?

---

I'm sure that would also work, but it would make the optical path for the IR feedback a lot more complicated. (Seems like the scanner mounting block itself would be in the way.)

Picking off the IR after the scanners is fairly straightforward (the second dichro only needs to be about 1" square to capture the entire scan field, assuming you mount it very close to the scanners), and the IR detectors can be mounted further to the side so they don't interfere with the scanners or the incoming beam path.

Adam

Quote:

---

Originally Posted by buffo

Less chance of getting lung cancer with silicon carbide, right? :)

Adam

---

That, and the fact that the cost is typically an order of magnitude (or more) less per mirror!

Yes, its been done before, this from my design ~1983-1985.


Attachment 61190

You performed shows with a DIE-ONICs ? You have my utmost respect... (Laser Ionics, notorious for broken gas reservoirs when traveling, but highly cost effective in use!) Not easy to change the tube, as it was glassed in through a hole in the resonator base. If I'm wrong, that is the other blue Ion Laser, made in UTAH... A whatchamacallit... I can't remember, but much better made...

Steve

Quote:

---

Originally Posted by mixedgas

You performed shows with a DIE-ONICs ? You have my utmost respect... (Laser Ionics, notorious for broken gas reservoirs when traveling, but highly cost effective in use!) Not easy to change the tube, as it was glassed in through a hole in the resonator base. If I'm wrong, that is the other blue Ion Laser, made in UTAH... A whatchamacallit... I can't remember, but much better made...

Steve

---

DIE-ONICs. Cute, I hadn't heard that one. No, this Laser Ionics Model 554 mixed-gas laser was for a static planetarium installation. I agree entirely on what a pain in the ass it must have been to service it. Luckily, the planetarium client bought the laser, I designed and built the 4-color, 3W projector and graphics control system around it. I don't accurately recall, but I think the tube lasted 3-4 years of 11 shows per week use. I saw the projector a few years after that and it had a Spectra Physics 164 Krypton laser head on it.

Hi hermit, the thought crossed my mind when I read how galvos with larger mirror are not as fast as those with smaller mirrors. I understand and more powerful beams tend to have larger diameters and therefore require larger mirrors.

Then looking inside my Lasercube 7.5 W Ultra reveals that there are actually many laser diodes for each color all brought together by a forest of dichroic mirrors.

So, my thought was well, why not combine two laser sources at galvo level so that each galvo can work with a smaller mirror.

But I hear you and your comments are quite valid. It's too expensive and I have started to realize that I rather have many smaller lasers than a few big ones, it was more of a thought experiment.

Quote:

---

Originally Posted by dinther

Hi hermit, the thought crossed my mind when I read how galvos with larger mirror are not as fast as those with smaller mirrors. I understand and more powerful beams tend to have larger diameters and therefore require larger mirrors.

Then looking inside my Lasercube 7.5 W Ultra reveals that there are actually many laser diodes for each color all brought together by a forest of dichroic mirrors.

---

I suggest watching zenodilodon's laser repair videos on YT. He covers aligning, cleaning, and troubleshooting many different models of commercial laser projectors, plus he demonstrates DIY builds.
His monologue is very entertaining, as well.

Hope this is helpful.
BR
Roj
😎

Quote:

---

Originally Posted by TheHermit

Saweet & neat galvo configuration!
How was color and beam splitting handled?

---

Thanks, look at post #19 on the "Back then this is what we did" PLF discussion. It is documented there.

This was the first version. In the second version I replaced the four MM1 mounts on the right with two facing, right-angle prism mounted with epoxy directly over the laser beam pass through holes on the right side of this mount that fed the right pair of XY galvos.

Quote:

---

Originally Posted by TheHermit

Yep, just as I suspected and why I asked.
AOMs, the colormod of my wettest dreams, back in the day.
Had the black aluminum channel, interlocked removeable covers, GS120 galvos, and even a (kinda) similar hand drafted RYGB AOM mixer design drawing on graph paper, but just couldn't afford the AOMs. So, I could only use Laser Images' dual prism & beam torquer, instead <sigh>.
I can totally relate to that being your pride and joy projector.
Well done!

Roj

---

Thanks again. It was the use of an Amici prism for the AOM beam path to scanner head that made this design practical (and we thought this was fairly compact back then!). It wasn't long after two versions of this RYGB projector had be fabricated that the new PCAOMs? came out that allowed one cell to switch between wavelengths for colormod'ing.

Well I know where between 4 and 8 IntraAction AOMs w/drivers are that could be had fairly cheap if anyone is interested.