Laser Galvo - Arduino Controlled

Arduino controlled laser galvo. The servo driven mirrors steer the UV laser leaving a phosphorescent trail on the glow-in-the-dark vinyl sheet.

Originally posted on notes.robives.com

Step 1:

Starting with a sheet of luminous vinyl from eBay and a UV laser pointer. Waving the laser pointer round on the vinyl leaves a persistent glowing trace, just like an old style cathode ray tube. Fun, but even better if we can computer control the laser beam!

I’ve come up with a hardware platform that I hope will let me start simple but then experiment with more complex ideas.

Step 2:

I’m using off the shelf servos driven by an Arduino to steer the beam from the laser.

There are two servos, one for the x axis, one for the y. I’ve attached a small circular mirror tile to the servo.

Step 3:

This stand is made from 3mm laser cut ply – there is a pdf of the parts attached - glue the pieces together using PVA glue.

Step 4:

The servos are clamped in place rather than gluing then to make it easy to make small adjustments. These are cheap off the shelf clamps from Wilkos in the UK

Step 5:

All the parts fit together like this:

Step 6:

…and the servos are connected to the Arduino board. I’ve used pins 9 &10 for the servo control lines.

The code for the arduino is attached

Step 7:

Here’s the code in action.
Next step, I think I’ll have a go at a simple raster display.

Comments

[webohub]

how fast those servos can go? do you have any updates on this project?

[Johenix]

You don't need servos. Just put a boron super magnet in the center of the mirror and hang the mirror and magnet by a two axis gimbal using nylon monofilament sewing thread inside a three axis Helmholtz Coil volume.

A Helmholtz Coil is two identical coils, in series, spaced a distance apart equal to their radii. The coils produce a uniform magnetic field in the space between them and can cancel out the Earth's magnetic field. Vary the Helmholtz coil current and make the mirror dance.

[DrStein99]

P.S. - With a quick Amazon search, I can buy a 1-axis Helmholtz coil for a thrifty $400. Not something an average hobby experimenter plays with for a toy. If anyone owns these coils, I'm sure they're probably also using something bigger then a dollar-store laser diode pointer.

[NoPinky]

You have link to a more detailed description or visualization to the mentioned setup? Thanks.

[Johenix]

Some years ago "Scientific American"'s Amateur Scientist series had an earth field magnitometer (I know the spelling is wrong) that used a Neodymium Iron Boron magnet to measure changes in the Earth's magnetic field. The magnet was glued to a mirror made from a microscope slide cover glass and mounted on a horizontal nylon monofilament thread mounted on a 'U' shaped support that hung from an other nylon thread. The Helmholtz Coils nulled out the Earth magnetic field so that only changes in the field would move the magnet and mirror. A laser pointer was reflected off the mirror and on to a scale so that changes could be read.

[DrStein99]

The Helmhotz coils are interesting. thanks for mentioning that. I was looking for a way to steer a laser beam for raster and vectoring images. It would take a bit of effort to calibrate the size of the magnet, center the mirror & string with the array of current drivers on that field. The software to drive the field is complicated enough just to angle x,y precisely - and has to factor corrective signal for the inertia of the magnet/mirror on rapid movements.

[artmez]

I found that article here:

https://metodosgeofisicos.files.wordpress.com/2007/04/0199106b.pdf

[robives]

There's also this showing another galvo project http://elm-chan.org/works/vlp/report_e.html

[aasukisuki]

Pretty cool, but why don't you just have the servos move the laser pen instead of 2 mirrors?

[DrStein99]

The laser has more mass & weight then the mirrors. The greater the mass, the more difficult it is to control and stabilize, change direction, etc...

[robives]

I moved the mirrors rather than the laser as they are very light weight and therefore faster to move.

[GeekMomProjects]

Very cool project! If you're looking for more precision, you might consider switching to stepper motors over servos. Nicely done.

[robives]

I went with servos as they are cheap and easily to use - but I like the idea of stepper motors, I'll give it a go.

[DrStein99]

Stepper motors can do the trick, except the image is choppy at best. They are made to rotate from one degree to the next. When an optical beam is applied to that shaft, across a distance you can see the amount of deflection and jittter & bounce that is caused on the magnetic field and bearings that deflect off of the mass of the housings, mounts, and desk it's sitting on. In order to make a steady image, you need the least mechanical mass as possible. There are no moving parts in a CRT television tube, which uses only a magnetic field to control the beam of light. Laser projection TV relies on spinning gyroscopic mirrors and complex electronics to make that image. Try and research how common laser-printers bounce that laser off the mirror to render the toner print-out. You can buy used laser printers for cheap, take them apart and see inside. Of course you can use the mirror, motor, focus lens with the perfectly manufactured jig it's already mounted on. You may also need a good understanding of electronics to fabricate the electronic control driver for that setup.

[DrStein99]

Stepper motors can do the trick, except the image is choppy at best. They are made to rotate from one degree to the next. When an optical beam is applied to that shaft, across a distance you can see the amount of deflection and jittter & bounce that is caused on the magnetic field and bearings that deflect off of the mass of the housings, mounts, and desk it's sitting on. In order to make a steady image, you need the least mechanical mass as possible. There are no moving parts in a CRT television tube, which uses only a magnetic field to control the beam of light. Laser projection TV relies on spinning gyroscopic mirrors and complex electronics to make that image. Try and research how common laser-printers bounce that laser off the mirror to render the toner print-out. You can buy used laser printers for cheap, take them apart and see inside. Of course you can use the mirror, motor, focus lens with the perfectly manufactured jig it's already mounted on. You may also need a good understanding of electronics to fabricate the electronic control driver for that setup.

[Smelter_uk]

This could be a real time sign writing gizmo. How long does the image persist?

[robives]

No more than a few seconds - you can see the fade on the YouTube video. As long as you keep rescanning though I'm sure you could make a sign. I'm planning to try making a clock display which would use roughly the same idea.

[Smelter_uk]

Hmm, anything like this?
http://www.yugop.com/ver3/stuff/03/fla.html

[robives]

Yep - but without the eraser :-)

[Yonatan24]

So are you saying in step #1 that if I shine a laser pointer at an old CRT TV, It will glow a bit?