[Aritomi, Yuhang]

We measured closed loop transfer function (G_CL) of galvo by measuring ADD_OUT/ADD_IN in galvo servo. From G_CL, open loop transfer function (G_OL) can be calculated as follows.

G_OL = -1+1/G_CL

Note that sign of formula (3) in the attached galvo document should be opposite.

We measured OLTF of QPD2 DC pitch (X) (attached figure). UGF is 800Hz and phase margin is 30 deg. Compared with design (figure 8 in the galvo document), shape is similar, but UGF is smaller (design is 2kHz).