Photonics Online - April 2009
Negative-Stiffness Vibration Isolation Gaining Popularity As The Need For Refined Imaging With Laser/Optical Systems Increases
By Jim McMahon
Laser and optical systems, whether used in academic labs
or industry, are very susceptible to vibrations from the
environment and these instruments frequently need vibration
isolation. When measuring a very few angstroms or nanometers
of displacement an absolutely stable surface has to be maintained
upon which to rest the instrument. Any vibration, coupled
into the mechanical structure of the instrument, will cause
vertical noise and fundamentally an inability to measure
these kinds of high resolution features.
Traditionally, large air tables have been the isolators
used for laser/optical equipment. The ubiquitous passive-system
air tables, adequate up until a few years ago, are now being
seriously challenged by the need for more refined imaging
requirements. Bench top air systems, however, provide limited
isolation vertically and very little isolation horizontally.
Yet, Scanning Probe Microscopes (SPMs), for example, have
vibration isolation requirements that are unparalleled in
the laser/optical world. The vertical axis is the most sensitive
for most SPMs. They can also be quite sensitive to vibrations
in the horizontal axes. In order to achieve the lowest possible
noise floor, on the order of an Angstrom, vibration isolation
must be used. Negative-Stiffness Mechanism (NSM) isolators
have the flexibility of custom tailoring resonant frequencies
vertically and horizontally, providing increased isolation
performance for SPMs over air tables.