Sennheiser Announces Optical Microphone Technology
March 3, 1999The optical microphone principal has now reached a higher level. A technique
newly developed by SENNHEISER and PHONE-OR Ltd. makes it possible to realize
the principle of the optical converter with remarkable new characteristics.
A beam of light is projected from an optical glass fibre onto a reflective
diaphragm. A second glass fibre captures the reflected light and conducts it
to a photodetector.
Glass fibres of this type are widely used in high quality data and phone networks,
and experience only very minor losses in light transmission. This advantage
enables the optical microphone transducer to be placed a considerable distance
away from the light source (LED) and photodetector with their associated active
electronic components.
As a result this novel microphone system can be applied in locations which
have previously been unsuitable for conventional microphones, including locations
subject to extreme electric or magnetic fields, e.g. nuclear magnetic resonance
imaging, computer tomography, in the vicinity of power output stages, and even
in volatile or hazardous environments.
Particularly interesting advantage of this new microphone derives from its
diminutive size, which makes it suitable for live applications. Quality microphones
of less than 3 mm (1/8") diameter are easily achievable with a frequency
responsecomparable to that of the standard for such applications,
our classic Sennheiser MIKE 2. Of further importance for these applications
is this model's high degree of tolerance to moisture, since the actual transducer
function is purely optical, with no sensitive electronic components needed in
the capsule.
The new optical microphone has been developed by SENNHEISER, based on the optical
converter principle of Phone-Or (US
Patent #. 5771091). For more information, visit Sennheiser at http://www.sennheiser.com/ | 
