Vrad

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Originally Posted by planters

...Jon, These look pretty small.

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a) As a wise Frenchman once said: 'it's not the Size of the galvo that counts, it's ..' ..well, you know the rest.. :)

b) Uh, No.. I would not categorize these as 'small'..

Attachment 49940 Attachment 49941 ..I don't know of any reason why these could Not do something even rediculous like.. Attachment 49942

..No, not as 'big-as the CT 6650's, there, but... these puppies are Strong. It's mag holds-up it's own weight on a 'fridge' or metal-cabinet..

Attachment 49939

..I think we have Both the 519s (which I - believe - were / are the same galvo-body, perhaps with a different Coil / V-rating (?), kinda like they have with the different size / rating 'GM20-style' actuators, But.. we've also got the 264s (I think that Might be a Z, not a 2, there, Sir W..)

..But, they are not likely to be as 'accurate' as the CTs 6630s - If those can handle a mirr-mount, Big-enough, to Mount your 75mm mirrs, on.. These GS's Can.

Again, Fwiw..
j

... one thing with fast moving big mirrors is the 'elasticity' of thin glass plates - with 0.5mm thick mirrors in sizes of 25x25mm I've already got some deflection at 20kpps, so changed to thicker/stiffer mirrors with much higher mass and servos to handle them ...

Viktor

Planters, I've seen those move ~45 mm round mirrors at a trade show, scanning a short persistence phosphor panel with a UV laser. The mirrors were thin, but had the lightweight 3D bracing installed on the backside. The image was barely flickering. The display was owned by Cambridge's parent company, who admitted they had a few techniques that are proprietary for using big mirrors for marking and scanning.
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With the right waveforms, amplifier tuning, and mirrors, those suckers can really move, due to the immense magnets. The mirrors that are on them were used to project lay-ups in a Carbon Composites plant, making structures for aircraft. The system they were in guided the employees on how to orient the sheets of composite using a 15 mW Hene, and modern ones use Green at 532. It could even produce 5 characters or so of text next to the outline to tell the employees what piece to select. yeah, it flickers when they use them at huge angles, but the systems save the companies huge amounts of money from bad layups of very expensive carbon fiber aircraft parts.
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The reason the mirrors are so big, is they also looked at a telescope that collected light from what are basically bicycle reflectors used as positioning targets in the field of view. They could actually triangulate on the reflections and get a position to within a fraction of a millimeter. Multiple scan heads (3) were used to do this. A hole drilled in the center of all the telescope optics allowed a 1 mm graphics beam to pass thru the collection optics, un-molested or altered.
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The slew rate limiter in those amps will prevent the oscillation and destruction one would expect if a traditional scanner is attached to an oversize mirror and driven hard. If it is properly configured per the manual I sent you.
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I've ran 24K graphics into them with the mirrors I shipped you, and they do a decent job of trying to replicate the ILDA test pattern at 4 degrees, with the slew rate limiter protecting them from induced oscillation. If they can't scan it, they simply wait and then slew to the next part of the image they can scan.
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Note to others reading this, slew rate limiters are not a panacea or overall remedy for persons who do not understand how to tune and use fast galvos. They do have effects on the image that have to be compensated for, and if mis-used, badly degrade beam shows. SRLs degrade your ability to use just a few points to define a beam shot, yet allow graphics. Again, with the right waveforms, proper tuning, and by selecting the right amount of slew rate limiting he needs, Eric can do what he wants..
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I sold you those for nefarious reasons Eric, I figured you would have shot a video by now on large mirror scanners and how to properly implement them. They do move very, very, fast for their size. You can always slow Cambridge scanner amps down with proper tuning, they typically have huge reserves of damping/scan angle/output drive for larger mirrors, if you wish to go slower. Speeding them up them up beyond design spec is the real problem, as I cannae defy the laws of physics, Captain!. (I do have two more pairs with amps)
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Spec, I wish you would fix the spacing problem on my posts so I have whitespace instead of !!!!! for spacing.
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!Steve

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one thing with fast moving big mirrors is the 'elasticity' of thin glass plates

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Yes, this is very interesting to me. I did some analysis last year and discussed with both Bill at Pangolin and even mentioned this to Eye Magic. Mirror inertia and stiffness can be improved. Materials such as beryllium and light weighting techniques such as edge taper and side drilling were both explored because of the potential and low cost vs the exotic materials. The major problem was the small size of the scanner mirrors. With larger mirrors a trapezoidal design becomes easier to fabricate and even a machined shaft that supports the mirror outboard from the axis could be fabricated from aluminum (twice as stiff as glass) or ORIENTED carbon reinforced fiber.

With all this alphabet soup, I don't know which motor /driver combo is likely to be the best bet. From my description above, I think the mirror may be able to benefit from a very strong motor and accuracy is always a good thing, but depending on the trade off, will all these motors be super accurate compared to the typical motors we are using in the average show projectors?

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Steve,
Just now saw your post. Thanks. The other projects (lasers for these scanners) have been incredibly complex, hence the delay.

Eric, that Galvo has the capacitive position sensors for best linearity and accuracy.. In use they had 14 bit accurate Dacs plus a sign bit for direction. As shipped, they are tuned for accuracy.

Steve

I will send you a schematic of my old Accelerator 124. You could build a handful of those and get about the best performance possible from a VRAD 1510.

The only "problem" I have is that a VRAD 1510 has pretty high (50 ohm) coil resistance and pretty high (millihenrys) inductance. The resulting system isn't going to be terribly fast... but I guess it also won't be very expensive either, so...

Bill

If you really mean "very slow" I can let you know the results I get with Escap p532 disk magnet motors that I mentioned on another thread. They should be on my desk at work by now. Basically they're high speed steppers. If you stick a gear head in front of each you'd have somewhere near 2 minutes of arc resolution without ministepping and you can make sure the bearings can handle the load of the mirrors...

Hey Bill, with a good feedback system would a digital driver that chose between whole, half, and various ministeps be a thing? After all this P532 motor has a .7 mH inductance with a 100 steps/rev

I have two of these boards for sale if anyone wants them.

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Originally Posted by Pangolin

I will send you a schematic of my old Accelerator 124. You could build a handful of those and get about the best performance possible from a VRAD 1510.

The only "problem" I have is that a VRAD 1510 has pretty high (50 ohm) coil resistance and pretty high (millihenrys) inductance. The resulting system isn't going to be terribly fast... but I guess it also won't be very expensive either, so...

Bill

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Lol.. dream beamz is showing his laser age... No worries, all us old timers have them around also.. :)