Details on Specifications for Active Optics / Steering Mirrors

Motion and Positioning

Performance specifications are valid for room temperature (22° ±3 °C) and closed-loop systems are calibrated at this temperature (specifications for other operating temperatures on request). Recalibration is recommended for operation at a significantly higher or lower temperature. Custom designs for ultralow or ultra-high temperatures on request.

Integrated feedback sensor
Absolute measuring capacitive and strain gauge (SGS) sensors are used to provide position information to the controller. For details see the tutorial "Piezoelectrics in Positioning" section (see link).

Open-loop linear travel @ 0 to 100 V
Typical open-loop travel at 0 to 100 V operating voltage. Max. recommended operating voltage range is -20 to +120 V (extremes for short durations only).

Closed-loop linear travel
Travel provided in closed-loop operation. PI piezo amplifiers have an output voltage range of -20 to +120 V or -30 to +135 V to provide enough margin for the servo-controller to compensate for load changes, etc.

Open-Loop Tilt Angle @ 0 to 100 V
Typical open-loop tilt angle at 0 to 100 V operating voltage. For differential-drive tilt platforms, 0° is reached at 50 V drive voltage, the maximum negative angle at 0 V and the maximum positive angle at 100 V. Max. operating voltage range is -20 to +120 V (outside 0 to 100 V for short durations only).

Closed-Loop Travel
Tilt provided in closed-loop operation at room temperature. PI piezo amplifiers have an output voltage range of -20 to +120 V or -30 to 135 V to provide enough margin for the controller to compensate for load changes etc.

Open-loop / closed-loop resolution
Resolution of piezo flexure stages is basically infinitesimal because it is not limited by stiction or friction. Instead of resolution, the noise-equivalent motion is specified. Values are typical results (RMS, 1 s), measured with E-503 amplifier module in E-500/501 chassis.

Full-range repeatability (typ.)
Typical values in closed-loop mode (RMS, 1 s). Repeatability is a percentage of the total distance or angle traveled. For small ranges, repeatability is significantly better.

Pitch / Yaw / Roll / Rotational Runout
Typical rotational off-axis error; sometimes associated with a particular motion axis, as in "Rotational runout (Z motion)".

Straightness / Flatness / Crosstalk
Typical linear off-axis error; sometimes associated with a particular motion axis, as in "Crosstalk (Z motion)".

Mechanical properties

Stiffness
Static large-signal stiffness of the piezo mechanics in operating direction at room temperature. Small-signal stiffness and dynamic stiffness may differ because of effects caused by the active nature of piezoelectric material, compound effects, etc. For details see the tutorial "Piezoelectrics in Positioning" section (see link).

Unloaded resonant frequency
Lowest tilt resonant frequency around active axis without mirror attached to platform (does not specify the maximum operating frequency). For details see the tutorial "Piezoelectrics in Positioning" Section (see link).

Resonant frequency with mirror
Example of how a load (mirror) attached to the platform affects the resonant frequency (calculated data). See "Dynamic Behavior" (see link) for further details.

Drive properties

Electrical capacitance
The piezo capacitance values indicated in the technical data tables are small-signal values (measured at 1 V, 1000 Hz, 20 °C, no load). Large-signal values at room temperature are 30 to 50% higher. The capacitance of piezo ceramics changes with amplitude, temperature, and load, up to 200% of the unloaded, smallsignal capacitance at room temperature. For detailed information on power requirements, refer to the amplifier frequencyresponse graphs in the "Piezo Drivers / Servo Controllers" (see link) section of this catalog.

Dynamic Operating Current Coefficient (DOCC)
Average electrical current (supplied by the amplifier) required to drive a piezo actuator per unit frequency and unit displacement (sine-wave operation). For example, to find out if a selected amplifier can drive a given piezo tilt platform at 50 Hz with 300 µrad amplitude, multiply the DOC coefficient by 50 and 300 and check if the result is less than or equal to the output current of the selected amplifier. For details see the tutorial "Piezoelectrics in Positioning" (see link) section.

Miscellaneous

Operating temperature range
Typically -20 to +80 °C, the temperature range indicates where the piezo stage may be operated without damage. Performance specifications are valid for room temperature (22 °C) and closedloop systems are calibrated for optimum performance at this temperature (specifications for other operating temperatures on request). Recalibration is recommended for operation at a significantly higher or lower temperature. Custom designs for ultralow or ultra-high temperatures on request.

Material
Flexure stages are usually made of anodized aluminum or stainless steel. Small amounts of other materials may be used internally (for spring preload, piezo coupling, mounting, thermal compensation, etc.).

Al: Aluminum
N-S: Non-magnetic stainless steel
S: Ferromagnetic stainless steel
I: Invar
T: Titanium

Voltage connection
Standard operating voltage connectors are LEMO and sub-D type connectors.

LEMO connector: LEMO FFA. 00.250, male. Cable: coaxial, RG 178, Teflon coated, 1 m

Sensor connection
Standard sensor connectors are LEMO and sub-D type connectors.

Sub-D special connectors contain both piezo voltage and sensor connections.

For extension cables and adapters, see "Accessories", in the "Piezo Drivers / Servo Controllers" Section.