Laser-Community | The Laser Magazine from TRUMPF
© Michael Mazohl
LIGHT HEARS SOUND
2017-03-29
Balthasar Fischer’s microphone relies not on a diaphragm, but a laser. This
founder’s invention has caught the attention of enthusiastic researchers and
entrepreneurs.
The start-up scene is thriving. Armed with ideas and business models, these minicompanies are competing for publicity, investors and sponsors. But not only in
Silicon Valley – creative minds and their ingenious ideas are enjoying tremendous
success in Europe as well. Optical technologies, for instance, are truly booming,
and their start-up scene is especially dynamic. Photonics is regarded as cuttingedge. Whether in Industry 4.0, intelligent lighting solutions of tomorrow or new
imaging techniques in medical technology, light has a bright future. Established
companies and research institutes are just as sure of this as are aspiring up-an-coming scientists.
LASER INSTEAD OF DIAPHRAGM
Balthasar Fischer is one of the believers – with the invention to prove it. Fischer’s
idea? An optical microphone that has no moving parts. This invention made him an
entrepreneur. His long list of customers includes research institutes and
corporations such as CERN, Fraunhofer, Zeiss and Siemens. TRUMPF Venture is
an investor. As for Fischer’s company, Xarion Laser Acoustics GmbH in Vienna, it
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has graduated from the start-up phase: it now has 15 employees working on the
small sensor.
We are revolutionizing the monitoring of
processes and machinery in industrial
manufacturing
BETTER THAN THE HUMAN EAR
Whereas conventional microphones rely on a vibrating diaphragm, Fischer’s
invention uses a laser beam. When a sound wave hits the laser light of his optical
microphone, the pressure slightly alters the light’s speed. In turn, the laser beam
propagates more slowly. The light intensity thus indirectly measures the sound
wave, which is converted to an electrical signal.
Laser beam instead of diaphragm: sound waves alter the speed of laser light. The light
intensity thus indirectly measures the sound. (photo: Xarion)
Results can then be visualized. Merely a few square millimeters in size, the sensor
needs no moving parts and is thus resistant to external influences. The sensor can
also measure sounds ranging from low infrasound to ultrasound in the megahertz
range. This frequency range is 50 times broader than that of the human ear – and
ten times greater than the best airborne-sound sensor available today. “We are
revolutionizing the monitoring of processes and machinery in industrial
manufacturing,” says Fischer. “If we can listen to a machine that uses a laser for
material processing, for instance, then we can ascertain whether a nozzle is
clogged or precisely how deep the laser beam penetrates the material. We obtain
this information by using the microphone at very high ultrasonic frequencies.”
Fischer envisions fields of application in Industry 4.0 and elsewhere.
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HEARING THE DEFECT
Xarion manufactures optical microphones in a clean room in Vienna. (photo: Xarion)
Another area where the optical microphone could soon be used is nondestructive
material testing in fields such as aircraft manufacturing. Non-contact analysis
allows the microphone to “look” inside materials, as demonstrated by an
experimental setup at Xarion. An ultrasound transmitter was mounted on the top of
a carbon-fiber composite plate, with the sensor on the bottom. “The microphone
measures how much sound passes through the plate. Because the sensor is very
sensitive and measures a very wide range, it can detect even very small defects,
and with a high level of accuracy,” stresses Fischer.
EARLIER DETECTION OF CANCER
Small and precise: this microphone with no moving parts measures sounds from
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low infrasound to ultrasound in the megahertz range. (photo: Xarion)
Thanks to its lack of moving parts, the microphone is resistant to vibration, wind
noise and solid-borne sound. And because there is no inertial mass, there can be no
reverberations. As a result, the microphone provides reliable measurements at
frequencies up to 25 megahertz – even underwater or in a radioactive environment.
This makes it appealing for use in medical technology – particularly photoacoustic
tomography, which employs laser pulses to make biological tissue vibrate. The
microphone then measures the resulting ultrasonic waves. This makes it possible to
see whether there have been any changes in the tissue. This facilitates early
detection [BW2] of cancer and eliminates the need for invasive techniques.
READY FOR THE HARSH REALITY OF EVERYDAY USE?
Little sensor, big potential. Fischer was initially by no means certain, however, that
his idea would prove good enough to serve as the foundation for a company. “It’s
very risky to found any company. You just can’t know if it’ll work out in the long
run. You feel like somebody has thrown you in the deep end,” says Fischer. He
consequently recruited Leonhardt Bauer, formerly a principal at McKinsey &
Company, in 2012 to be co-founder. Bauer had experience with start-ups, which
would help put Xarion on solid footing. “Engineers are often so excited about their
work that they’re oblivious to key economic aspects that must be considered,” says
Fischer.
Engineers are often so excited about their work
that they’re oblivious to key economic aspects
that must be considered
Balthasar Fischer’s invention paved the way to founding a company. (Foto: Michael
Mazohl)
But entrepreneurial risk was not all he faced in the beginning; he also had his
hands full with technological challenges. “Nobody had ever measured sound in this
way – it was uncharted territory. We regularly had to cope with minor setbacks. But
if the laws of physics say no, that’s impossible, then you can’t argue with that –
which occasionally cost me some sleep.” Sleepless nights are a thing of the past for
Fischer; his product works. The Xarion team is now working to establish their
optical microphone in heavy-duty, everyday industrial use. After all, there is no
guarantee that a sensor that performs well under laboratory conditions will be
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similarly reliable in a production facility. “We’re currently integrating our sensor
into a lot of exciting projects. Our focus is less on the microphone now and more on
our customers’ needs. We keep approaching things from a new angle.”
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