After getting the peak displacement of each mode
vibrational frequency of the device by a single sweep
test, the multi-point fixed-frequency test is
undertaken to set the frequency point and obtain the
overall position morphology of the vibration
membrane, each vibration mode, and validate the
vibration characteristics. In the test, the white-light
fringe is firstly regulated to make the black and white
stripe at equal intervals with no drift in order to get a
sharp image of the device. In addition, we also pick
up the laser spot and move it within the positions of
the three points to determine the scan plane. And then