Megneto resistive sensor:

http://www.digikey.ca/product-highli...r-Series/52414


Taken from Wikipedia:

The AMR effect is used in a wide array of sensors for measurement of Earth's magnetic field (electronic compass), for electric current measuring (by measuring the magnetic field created around the conductor), for traffic detection and for linear position and angle sensing. The biggest AMR sensor manufacturers are Honeywell, NXP Semiconductors, and Sensitec GmbH.


So Im sure you can sense the angle of the galvos with it. With something like this you might even be able to electrically dampen the system with a closed loop angle feedback from the magnetic sensor.

For those familiar with control loop theory:

Youd have your input signal with a voltage proportional to what angle the mirror would be.
Next it would go to your amplifier circuit to drive the mirror.
From the mirror you would then have a positional measurement by the magnetoresistive sensor.
The error is defined by where the mirror actually is, and where you wanted it, and this signal is fed back to combine with the original signal to close the loop and subtract away the error. A system like this should auto dampen.

The physical setup would need to be decided... I would imagine a circuit board re-work to get the sensors close to the mirrors' magnets... Or maybe they sell chasis mountable sensors.

Personally I would have just made two PCBs for each mirror axis, combining their motors, sensors, drivers and tuning. Then they would mate with the snap fits. You could have the exact same PCB design for each mirror PCB.

A jumper connector can connect both boards together. When assembling the PCB's youd just populate the computer connections for one board, and leave the second blank (having the jumper wire connector between these two PCB mirror assemblies).

I hope I am being clear, the goal would be to modularize the design, and use a PCB for electronics, AND the mirror support structure. It might hopefully elliminate

1) some wiring to the coils, as they would be now on board
2) the main PCB, making the overall device smaller
3) make it much easier for standardization and mass production.
4) use less plastic.
5) reduce assembly time, and possible wiring mistakes.

Im sure there are more advantages, the one I am most interested in, being an electrical engineer, is the standardizing for mass production.

BUT, All this depends on the accuracy and usability of these types of sensors.

-UD