Life is full of small distractions we get used to, like trains rumbling by.
But small things can mean a lot, especially when you're trying to make optical components to microscopic tolerances.
And so it was that the National Optical Astronomy Observatory began worrying last year about what will happen when Tucson's modern streetcars start rumbling by the agency's home on the University of Arizona campus by late 2013.
NOAO, which is run by the Association of Universities for Research in Astronomy, operates telescopes on Kitt Peak and elsewhere as the national research and development center for ground-based nighttime astronomy.
But the streetcar will run along East Second Street, immediately north of NOAO's headquarters at 950 N. Cherry Ave.
NOAO staff members were worried that vibration generated by the streetcar - which will run by daily every 10 minutes from 6 a.m. to 11 p.m. - would hamper very precise measurements of optical components made with instruments called interferometers.
While there are many different kinds of interferometers, laser-based interferometers reflect laser beams off a test surface and a reference surface, superimpose the resulting light-wave images and create patterns that can be measured to spot surface imperfections in things like telescope lenses, in NOAO's case.
Responding to NOAO's concerns, the Modern Streetcar Project hired a California-based acoustical consulting firm to analyze the streetcar's potential impact by planting vibration detection equipment throughout NOAO's optics shop.
The result: Vibration from the streetcar could, indeed, interfere with NOAO's interferometry.
Isolating NOAO's large test setup from vibration was deemed too expensive to be practical.
So the agency sought a different solution - and found one not far away.
After evaluating several systems, NOAO ended up selecting a type of vibration-insensitive instrument, known as a Fizeau interferometer, made by Tucson-based 4D Technology Corp.
The AccuFiz interferometer provided by 4D in December is based on "dynamic interferometry," a technology pioneered by 4D a decade ago.
Among those pioneers are 4D President James Millerd and company Chairman James Wyant, former dean of the UA College of Optical Sciences and a world-class optical scientist who has co-founded several optics firms.
More traditional "phase shifting" interferometers capture multiple frames of measurement data sequentially.
"Traditional interferometers take a fair amount of time, typically hundreds of milliseconds," Millerd said.
That sounds fast, but it's not fast enough to avoid the effects of vibration, Millerd noted.
In contrast, dynamic interferometers like 4D's AccuFiz acquire all measurement data simultaneously in a single camera frame in less than a millisecond, 4D says.
That essentially takes vibration out of the equation, allowing very precise measurements.
Other companies, including some other local optics houses, offer Fizeau interferometers.
But 4D's AccuFiz, which debuted about a year ago and costs about $100,000, won out.
"In this case, I think one of the things they really liked about it was its very compact size, its versatility," Millerd said, adding that the system's relatively low cost, feature-filled software and the company's hands-on service approach also helped.
NOAO is just one customer, but as 4D celebrates its 10th anniversary this year, Millerd said the future of dynamic interferometry is bright.
"I think the whole thing is moving in this direction," Millerd said. "Typically it has been more expensive, and that's one of the things that the AccuFiz did, is kind of hit a new price point."
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