In addition to multiplication of stroke, the design affords momentum compensation.
A mechanical amplifier has been devised to multiply the stroke of a piezoelectric transducer (PZT) intended for use at liquid helium temperatures. Interferometry holds the key to high angular resolution imaging and astrometry in space. Future space missions that will detect planets around other solar systems and perform detailed studies of the evolution of stars and galaxies will use new interferometers that observe at mid- and far-infrared wavelengths. Phase-measurement interferometry is key to many aspects of astronomical interferometry, and PZTs are ideal modulators for most methods of phase measurement, but primarily at visible wavelengths. At far infrared wavelengths of 150 to 300 µm, background noise is a severe problem and all optics must be cooled to about 4 K. Under these conditions, piezos are ill-suited as modulators, because their throw is reduced by as much as a factor of 2, and even a wavelength or two of modulation is beyond their capability. The largest commercially available piezo stacks are about 5 in. (12.7 cm) long and have a throw of about 180 µm at room temperature and only 90 μm at 4 K. It would seem difficult or impossible to use PZTs for phase measurements in the far infrared were it not for the new mechanical amplifier that was designed and built.
This new mechanical amplifier provides both a longer stroke for standard piezo stacks and the necessary mechanical stability through an ingenious mounting arrangement. The device is made of titanium and machined using a wire EDM (electrical-discharge machining) process so as to be as strong and lightweight as possible. It is compact using only a single piezo stack, making it ideally suited for phase-measurement in a cryogenic environment.
This work was done by James Moore, Mark Swain, Peter Lawson, and Robert Calvet of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category. NPO-30289.
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Mechanical Amplifier for a Piezoelectric Transducer (reference NPO-30289) is currently available for download from the TSP library.
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