2.11.10

I was able to construct some modes for DM31 (the 31 actuator DM) using influence functions reconstructed from the poke matrix instead of the theoretical, simulated versions. When applied, both sets actually look pretty similar until the 10th mode or so, after which the experimental modes start to look like crap. I think part of the problem is that the WFS only samples the interior 80% or so of the beam, so several actuators peak on the edge or just outside of the frame. Since the experimental influence functions are actually pretty similar to the simulated versions (amazingly, even the amplitudes are within an order of magnitude!), I suspect that resizing the beam such that all the actuators are fully measured would help this out a little. Something to play with next week.

In the mean time, it'd still be interesting to construct modes for DM61 using its poke matrix. I found out yesterday that most of the actuators respond linearly to the square of the voltage command just like with D31, but there are 3 that don't seem to be moving at all, or or moving strangely. Tomorrow the plan is to swap out the mirror that's installed now with the spare to see if that solves the problem, and then take a look at the modes using that mirror's poke matrix.

I'm pretty clear on how to construct the modes now given a set of influence functions. Basically it just involves some clunky linear algebra. Maybe I'll write up a little short story about them one day.