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Tools of the trade - Vol 18 - 36188 Vibration Isolation Systems for Optical Tabletops

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Vibration isolation systems are used to maintain stability in theenvironment around an optical table so that there is no contribution from ground borne vibrations to the relative motion between components mounted to the optical table and the table itself. Vibrations may result from seismic activity from the building, pedestrian traffic or nearby machinery. The amount of transmitted vibration transferred to the tabletop represents an important factor in defining an optimized setup. For an ideal mounting system with appropriate seismic activity arigid tabletop should be mounted to the floor by a combinationof dampers and springs. Maintained by inertia, the springs compress and relax to stabilize the tabletop position. Minimum oscillation resonance and short settling times are ensured by a damping mechanism.Air springs are ideally suited to low-resonance with short travelranges along with high load capacities. As the floor vibrates, airpressure alternately increases and decreases to maintain stability. Objects placed on the tabletop remain stationary. The rigidity of the air springs operate independently from the load, yet it is dependent upon the height of the tabletop. Optimum performance is achieved by floating a load isolator to a working height that is nominal.Air springs that peak on a transmissibility curve at 3.25Hz, areideal for isolation of vibrations above 10Hz. Should significantvibration occur below 10Hz, a more sophisticated, verticallyenhanced table design is required.When enhanced vibration isolation is required, a two-chamber airspring can accomplish the additional isolation. In this configuration, an upper chamber connects to a lower reservoir through a resistance damper. Vibration damping is optimized when the friction fromcompressed air is forced through the resistance damper.In certain sensitive optical experiments, horizontal isolation isrequired. Vibrations ranging from 1Hz to 10Hz, can be virtually eliminated when horizontal isolating elements are employed. The SuperDamp™ design combines both a vertical isolation chamber and a horizontal vibration damper for optimal vertical andhorizontal isolation.Load balancing distribution on an optical table may need to bechanged frequently. To maintain optimum isolation performance automatic height adjustment is necessary to keep a level table.

Supports Optical Tables Table Supports Non-Magnetic

Selecting a Vibration Isolation System

TYPICAL APPLICATIONSNOISERIGID SUPPORTPUMP & GO™SUPERDAMP™Demanding Applications • Nanopositioning Quiet â�‘â–  • Submicron Precision • Phase Related:Typical • Interferometry• HolographyNoisy â–  • Single Mode Fiber Alignment â–  General Photonic Applications • Bioimaging Quiet â–  • Raman Spectroscopy • Micro PositioningTypical • Micro Machining â�‘â–  • Non-Interferometric• Laser ChemistryNoisy • Single Mode Fiber Alignment â–  Less Demanding Applications • Pulse Laser• General SpectroscopyTypical Quiet â–  • Velocimetry• Multimode Fiber AlignmentNoisy â�‘â–  â�‘â–  â–  Recommended â�‘ Suitable

Isolator System Performance Comparison

Rigid Nonisolating SupportsPump & Go™ Passive vibration IsolatorsSuperDamp™ Self-Leveling Vibration Isolator ParameterStandard DutyHeavy Duty (see page 61)(see page 60)(see page 60)(see page 58) VertHorizVertHorizVertHoriz Resonant FrequencyNonisolating<5 Hz<4 Hz<5.5 Hz<4.5 Hz<1.35 Hz1.0 HzTranmissibility (at Resonance)Nonisolating<6dB<9.2dB<6.5dB<9dB<4dB<4dBTransmissibility (at 10 Hz)Nonisolating<0.25dB<0.13dB<0.4dB<0.25dB<0.02dB<0.03dBIsolation Type NonisolatingPassivePassiveActive Damping EfficiencyNonisolatingGoodGoodBestLoad Capacity(Set of 4)2500 kg (5500 lb)1100 kg (2425 lb)2200 kg (4840 lb)2500 kg (5500 lb)

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