In open loop operation, the platform angle roughly corresponds to the drive voltage. The open loop model is ideal for applications where the position is controlled by an external loop based on data provided by a sensor (e.g., quad cell, CCD chip, ...).
The closed loop tip/tilt stage version is equipped with two pairs (one per axis) of Strain Gage sensors operated in a bridge circuit for ultra-high resolution and angular stability. They provide sub-µrad resolution and repeatability (with PI control electronics).
S-330.10 θX and θ Y Piezo Laser Steering Mirror Tilt Platform ±1 mrad, Strain Gage Sensor
S-330.30 θ X and θ Y Piezo Laser Steering Mirror Tilt Platform ±1 mrad