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Multi-Axis Tilt Platforms
PI offers two versions of Multi-Axis Tilt Platforms:A) Differential Piezo Drive Tilt Platform
The platform is supported by 4 piezo actuators (2 pairs) spaced at 90 degree intervals. Each actuator pair is operated in push/pull mode.
The differential design exhibits an excellent angular stability over a wide temperature range. With this design temperature changes only affect the vertical position of the platform (piston motion) and have no influence on the angular position. After the operating voltage is removed the platform returns to the center position.
B) Triple Piezo Drive Tilt Platform
Examples:
S-315 and S-316.The platform is supported by 3 piezo actuators spaced at 120 degree intervals. Control is more complicated because expansion of each individual Piezo actuator affects both qX and qY rotation. External coordinate transformation (software or hardware) is required to allow platform position commands in qX and qY coordinates. See equations and Fig. 3.5/1 below for details.
Fig. 3.5/1:
A,B,C is the linear displacement of the corresponding piezo actuators
(between 0 and 12 µm).a = [A-1/2 * (B+C)] / a
b = (B-C) / b
z = (A+B+C) / 3
Example:
S-315 and S-316 Tilt Platforms.Æ = 13.9 mm
a = 10.4 mm
b = 12.0 mm
A, B, C 0 to 12 µmThe triple piezo drive has another advantage. In addition to tilt motion it allows active vertical control (piston motion) of the platform an important feature for interferometric applications and correction of path length errors. Also, the design allows for a central clear aperture, ideal for transmitted light applications.
Like the differential drives, the triple piezo actuator design exhibits an excellent angular stability over a wide temperature range. With this design temperature changes only affect the vertical position of the platform (piston motion) and have no influence on the angular position. After the operating voltage is removed the platform returns to the center position.
