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Positioner Stability

Knowing a positioners stability characteristic is fundamental when planning an application. Stability is the accuracy with which zero-motion can be sustained over time, or the ability of a system to resume its state after being displaced. When qualifying the stability characteristic of the any positioner there are three major components that must be taken into consideration: temperature sensitivity, sensitivity to external forces and sensitivity to actuator drift. Luminos positioners have been meticulously engineered for high stability in these major areas. Luminos positioning systems have been carefully characterized and have been proven time and again to easily outperform other stages on the market.

Temperature Sensitivity

The athermalized design of Luminos CORALIGN™ Positioners allows them to effectively react to temperature changes as if each were a single piece of aluminum. Luminos positioners are axially symmetrical and all components are thermally matched with aluminum. This ensures that they have the same co-efficient of thermal expansion (CTE). Since all parts are symmetric and matched with aluminum any adverse effects of thermal expansion are nullified. Luminos positioners have been tested to show no hysteresis due to temperature changes. Environmental testing illustrate variation has been characterized as highly repeatable. When they are subjected to a series of thermal cycles the variation is highly repeatable and cyclic. There is virtually no distortion of components and temperature fluctuations have no detrimental effect on the stability. See Temperature Stability of the I3000 for detailed information.

Sensitivity to External Forces

Conventional flexure stages have extreme responses to everyday vibrational frequencies. Ordinary activities such as someone walking across a lab floor can cause serious effects. Usually extreme measures are employed to achieve a protective environment. The aggressive modifications employ expensive and sometimes impractical filtering agents such as optical tables, special flooring, isolations chambers etc. However, Luminos CORALIGN™ Positioners are so stable that shifts due to everyday vibration are not a factor. Luminos' approach to this problem was to design a damping system directly into each postioner. Also all CORALIGN™ positioners have a protective exterior shell. This shell is designed to shunt any operator induced vibrations away from the sensitive moving parts. Furthermore, an internal damping structure dissipates any external vibrational forces that may attempt to reach the flexure element. The internal damping coupled with a stiff exterior shell also provides high stiffness making for an extremely stable positioner.

Sensitivity to Actuator Drift

All drive mechanisms, micrometers, actuators etc. are vulnerable to drift. Grease between threads, lead nuts and other composite materials causes the threads to migrate when exposed to temperature changes and vibrations. With Luminos CORALIGN™ Positioners the patented Ratio Drive™ System diminishes drift by leveraging the input to drive the output. Ratio Drive™ also diminishes drift contributed by the actuators. If a non-Luminos positioning unit experiences 1µm of drift from the drive mechanisms, the result will be an output drift of 1µm. However, for a Luminos 25x Ratio Drive™ positioner a drift of 1µm is reduced by a ratio of 25:1 resulting in only a 0.04µm output deviation. Thus Ratio Drive™ significantly improves the stability of Luminos CORALIGN™ Positioners.

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