GLOSSARY

Absolute accuracy  : Deviation between the actual position and the desired one. If a stage has to move 100µm but it moves only 99.99µm (measured through an ideal scale), then the inaccuracy is 10nm. The permanent positioning error along an axis is designated as accuracy. Absolute accuracy is aff­ected by calibration errors, linearity errors, hysteresis, Abbe errors and positioning noise.

Backlash : Backlash is a positioning error occurring upon change of direction. Backlash can be caused by insufficiently preloaded thrust or inaccurate meshing of drive components, for example gear teeth. Piezoconcept’s flexure motion translation mechanism and piezo actuator designs are inherently backlash free.

Bandwidth : The frequency range to which the amplitude of the stage's motion is dropped by 3dB. It reflects how fast the stage can follow the driving signal.

Drift : A position change over time, which includes the e­ffects of temperature change and other environmental e­ffects. The drift may be introduced from both the mechanical system and electronics.

Friction : Friction is defined as resistance between contacting surfaces during movement. Friction may be constant or speed dependent. Because they use flexure, the nanopositioners from Piezoconcept are friction free.

Hysteresis : The positioning error between forward scan and backward scan. A closed-loop control is an ideal solution for this problem and is done by using a network of High Resolution silicon sensor to provide feedback signals.

Linearity error : The error between the actual position and the first-order best fit line (straight line). Our nanopositioning products are calibrated with laser interferometry and the non linearity errors are compensated down to 0.02% of the full travel.

Orthogonality error : The angular off­set of two defined motion axes from being orthogonal to each other. It can be interpreted as a part of crosstalk.

Position noise : The amplitude of the stage shaking when it is on a static command. It is usually measured and specified with Peak-To-Peak value. It is a combination of the sensor noise, driver electronics noise and command noise, etc. The position noise of our stages is very limited due to the very high Signal-To-Noise ratio of the Silicon HR sensors we use.

Range of motion : The maximum displacement of the nanopositioners.

Resolution : The minimum step size the stage can move.

Resonant frequency : Piezostage are oscillating mechanical systems characterized by a resonant frequency. The resonant frequency that we give is the lowest resonant frequency that can be seen on a nanopositioner. In general, the higher the resonant frequency of a system, the higher the stability and the wider working bandwidth the system will have. The resonant frequency of a piezostage is determined by the square root of the ratio of sti­ness and mass.

Silicon HR sensor : Piezoconcept use temperature compensated High-Resolution silicon sensors network for reaching highest long-term stability. This measuring device is capable of measuring position noise in the picometer range and its response is not dependent of the presence of pollutants, air pressure changes like other high-end sensors can be.

Step response time : The step response time is the time needed by the nanopositioner to do the travel from 10% of the commanded value to 90% of the commanded value. The step response time reflects the dynamic characteristics of the system and is relatively independent of the step size.