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Laser galvanometers in action

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LAN_403

Tesladownunder

Sat Jul 01 2006, 01:53PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I arranged two mirror galvanometers to give two dimensional control of a laser beam. These have a response to about 100Hz but can still be used to about 200Hz. I fed one with 50Hz and the other from a frequency generator. This gives smoothly rotating complex patterns that vary with the ratios of the two frequencies.
So 50Hz + 50Hz gives a circle, 50 + 100Hz gives a figure 8 etc.
These are some examples. I will show and explain the setup in a later post.

Peter

1151761999 10 FT0 Lasergalvos50plus200hz

Hazmatt_(The Underdog)

Sat Jul 01 2006, 11:51PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

That's really great TDU. Now if you can get a really fast response you can sweep one at a concert A and demonstrate modulation, overtones, and all sorts of neat stuff with the two generators, an audio amp, and the laser setup.

Tesladownunder

Sun Jul 02 2006, 12:17AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Hazmatt_(The Underdog) wrote ...

... Now if you can get a really fast response you can sweep one at a concert A and demonstrate modulation, overtones, and all sorts of neat stuff with the two generators, an audio amp, and the laser setup.

A concert requires big lasers (and a license). These galvos came with a diagram of how to passively run them from a stereo. Simply just a series resistor, 100 ohm WW pot and filter cap. This goes to one coil of the 10 pole motor and the other coil goes to 5-10V DC to provide a "spring" to hold it centered on one of the poles.

Here are some pics of the setup with the two miror galvos at right angles and as close together as possible. Power is from a 5mW red diode laser. I have made up an "optical table" with a 3cm beam height to accomodate this sort of stuff and some power so I can put all my mirrors and lenses etc on acrylic blocks.

Peter

1151799425 10 FT12381 Lasergalvossetupminilab

Hazmatt_(The Underdog)

Sun Jul 02 2006, 05:34AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I think you misunderstood a concert A is 440Hz.
I am simply stating that you could demonstrate Lissajou patterns to an audience and let them experience the AV. Its on my to-do list.

cjk2

Sun Jul 02 2006, 05:47AM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

I did something similar like a year ago. I used 3 mirrors and didn't have as sophisticated of a way to control motor speed. If there is any interest, I'll post more pictures and a better description of what i did.

Carbon_Rod

Sun Jul 02 2006, 06:13AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

TDU,
Nice response time â€“ the unit I built made use of Stylus galvo-motors out of an old unit. The unit used a 250-watt Car audio power Amp and shorted the secondary stabilization coils with a shunt resister to break the oscillations. I only managed around 70Hz for a decent complete sweep.
However, the colour bands had a special shutter system with small relays. The 45â€™ angled mirrors glued onto the arms to reflected to a light trap (they work pretty fast.) As yours is a diode unit it should be easy to key -- so this is not an issue.

For laser plotting pictures most use a PWM based system with an optical based feedback loop for high speed absolute positioning (calibration is easier this way.)

Here are some links to test files and stuff:
AVR project with driver software from ELM:

Norms stuff:

Clip Art (and test patterns):

Cheers,

Tesladownunder

Sun Jul 02 2006, 09:48AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Hazmatt_(The Underdog) wrote ...

I think you misunderstood a concert A is 440Hz.

After considerable investigation it has been conclusively demonstrated that I don't have a single musical bone in my body. So your comment fell flat (?A flat).

cjk2 wrote ...

I did something similar like a year ago. I used 3 mirrors and didn't have as sophisticated of a way to control motor speed. If there is any interest, I'll post more pictures and a better description of what i did

I'm interested...

Carbon_Rod wrote ...

TDU,
..I only managed around 70Hz for a decent complete sweep.
..For laser plotting pictures most use a PWM based system with an optical based feedback loop for high speed absolute positioning (calibration is easier this way.)

Performance certainly drops off in mine over 50Hz. I am not looking to take this further apart from trying it on my argon laser. Of course, shooting down aliens will take some further refinement.

Photos show stereo input. First one was the Dresden Dolls.

Peter

1151833687 10 FT12381 Lasergalvosstereo3

Tesladownunder

Fri Aug 18 2006, 06:30PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I have now made up a more compact unit with my 40 mW multiline argon laser which gives some great effects.
Some pics of the setup first, then of the output if any replies.

Peter

1155925857 10 FT12381 Laserlissajousargongalvossmoke

1155925857 10 FT12381 Laserlissajousargonflashoutside

1155925857 10 FT12381 Laserlissajousargonsetup

Hazmatt_(The Underdog)

Fri Aug 18 2006, 06:39PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Now that's what I'm talking about! very nice.

I would want the demo for kids to have 2 large dials for them to change the frequency, or maybe 2 HP signal generators so they could read the dial.

I found a complete laser light show unit in the mall in a store called Spencers. I'm thinking of picking one up and just modifying it for my inputs because its only going to cost me $40.

Marko

Fri Aug 18 2006, 06:47PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Very cool TDU! Holographic laces

I wonder if red and blue bemas could be crossed somehow..

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