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Published in Barat Ken, Laser Safety Tools and Training, 2017
Isolators filter vibrations between structural elements by reducing the transmission of such disturbances. Isolation can be achieved through the use of springs, rubber pads, air-filled bladders, pneumatic self-leveling isolation legs, or active isolation systems using piezoelectric or electrodynamic elements. Each offer varying levels of capability, performance, and of course price. In most cases an isolation performance is measured by a reduction in noise (dB) or a transmissibility plot that shows the isolator’s performance over a specified frequency range. A sample transmissibility plot is shown in Figure 18.2. Because isolators prevent vibrations on the floor from reaching the work surface, they generally eliminate 70% of all vibration problems experienced in typical laboratories. However, vibrations that do reach the work surface from either acoustic, surface mounted equipment, or airflow generated sources require effective vibration damping (structural damping within the optical table) to reduce their effect on sensitive systems.
Practical Tools for Laser Safety and Traps to Avoid
Published in Ken Barat, Laser Safety Management, 2017
Any investment counselor will tell you real estate is a premium asset. The same is true for laser labs. If only our labs were like the TARDIS from the BBC Dr. Who TV series, which is larger on the inside than the outside. For those of us who have not solved the space-time dimensional problem, space is a real issue. Even as lasers become smaller, we still find objects to fill all our space. Therefore, many laser labs looks like people’s garages. Unfortunately, this clutter is not confined to the space around the optical tables, but is also on optical tables themselves (even vertical optical table set-ups are not immune to clutter). Spare optical mounts, tools, lenses, mirrors, plastic bags, and plastic and cardboard boxes all tend to find a home on optical tables. Rather than being in a staging area separate from beam paths, they are under and next to active beam paths, acting as lures to attract hands into live beams or a reflection source when lifted through the beam.
Applications and case studies
Published in Roderic S. Lakes, Viscoelastic Solids, 2017
Many scientific instruments are vulnerable to vibration [10.21.5]. For example, scanning probe microscopes such as the scanning tunneling microscope and atomic force microscope are capable of resolving individual atoms on a size scale below 0.2 nm. An atomically sharp tip supported by a microscopic cantilever is scanned across the specimen. Tip deflection is measured via a reflected laser beam and held constant by a feedback circuit driving a piezoelectric actuator. In view of the high resolution desired, vibration must be minimized. Structural beam elements within the instrument may be made of magnesium, which has a low density ρ and comparatively high damping. Stresses are low in such an instrument, so the limited strength of magnesium is not a problem. Moreover, magnesium has a high value of E/ρ2, which is favorable for bending stiffness per unit weight. As another example consider the optical tables used to support laser equipment used in holography, interferometry, and other optical procedures which are sensitive to vibration. The table is supported upon pneumatic legs in which pressurized air supports the table via force upon a piston. The legs provide compliant support so that the table-leg system has a low natural frequency v0 near 1 Hz. Following Eq. 10.6.7, the transmissibility for vibration goes as (v0/v)2 for frequencies ν well above the natural frequency. Therefore, little vibration above 1 Hz gets through to the table. The table is made using a honeycomb sandwich construction which confers a high rigidity per unit mass, and hence a high fundamental resonance frequency. That resonance is damped by a tuned damper [10.21.6] consisting of a mass supported by flexure springs and immersed in a viscous fluid.
Preparation and characterization of a silver-magnesium fluoride bi-layers based fiber optic surface plasmon resonance sensor
Published in Instrumentation Science & Technology, 2020
Vicky Kapoor, Navneet K. Sharma
For the characterization of the fiber optic probe, one end of the fiber is coupled to a tungsten halogen lamp as a polychromatic light source (Ocean Optics, model HL-2000HP) with a microscope objective and three-dimensional translation stages. The role of microscope objective is to introduce all light rays from the source to one end of the fiber, while the three-dimensional translation stages hold the fiber such that maximum quantity of light is coupled. The complete setup is on a vibrationless optical table to eliminate any disturbances during the experiment. Wavelength interrogation method was exercised for characterizing the probe. The other end of the fiber is connected to a spectrometer (Ocean Optics, model: flame S-VIS-NIR-ES). The spectrometer is attached to a laptop to record the SPR transmission spectrum of the samples.