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# Making an oscillatory motion happen for a mirror

## Making an oscillatory motion happen for a mirror

(OP)
I would like to invite suggestions for a +/-20 degrees oscillatory motion for 300 mm dia/8 mm thick aluminium mirror at 5-15 Hz.
The main problematic requirement is the uniform velocity of excursion throughout the travel of the mirror.

### RE: Making an oscillatory motion happen for a mirror

300mm dia and 8mm thick is a large mirror to move at that speed.  Typically motion in that bandwidth is done by driving the mirror with voice coils and suspending it on flextures.  A digital control loop is then closed to some displacement sensor.  Accuracies in the tens of micro radians are possibe with this type of setup.  The size and therefore the resulting inertias are a bit larger than I have ever done though.  A reactionless design may be necessary to prevent coupling those forces back into the support structure.

### RE: Making an oscillatory motion happen for a mirror

Is the frequency constant or variable/programmable ?
Do you want sinusoid, sawtooth or triangle motion?
Can't you reduce the mirror size ? Why not ?

### RE: Making an oscillatory motion happen for a mirror

I can't remember the vendor name but check into laser shows such as the old "Laserium" who used both mirror galvanometers and servo driven scanners. I think it might have been called General Scanning.

This won't drive your mirror that big but might give you some ideas. Perhaps going to a pellicle type system would lower the mass enough for you to drive something that big in diameter.

Good luck and let us know how you solve this!

### RE: Making an oscillatory motion happen for a mirror

I think you should go back to the drawing board -- find out
what you want and find on other way to do it.

### RE: Making an oscillatory motion happen for a mirror

It's probably too late to jump in. There is a simple solution to your problem, as long as you can get by with motion in only one direction. Instead of using an oscillating mirror, use a continuously-rotating polygonal mirror. There is a diagram on this web page:

http://nb.beckman.uiuc.edu/biophotonics/...

You can rotate the mirror very fast, you can make it as large as you want, and the angular velocity is constant.

CV

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