Features
- Highly sensitive, fiber-coupled optical hydrophone
- Detection of small pressure amplitudes with a millimetre-sized sensor head
- Immunity to electromagnetic interference (EMI)
Eta250 L Ultra: Optical Hydrophone
Optical Microphone – World’s first microphone without any moving parts
XARION’s Eta250 L Ultra is a highly sensitive, membrane-free optical hydrophone. Designed to detect faint signals in the frequency range from 10 Hz up to 2 MHz with a millimetre-sized sensor head, it offers unique capabilities for ultrasound metrology in liquids. Using patented technology, the Eta250 L Ultra is immune to electromagnetic interference and features excellent long-term stability.
Besides high-frequency sonar for military and civil applications, it is also the perfect match for medical ultrasound and photoacoustics.
Applications
Ultrasound Measurements
Ultrasound Field Characterization
The small size and the linear frequency response make the Optical Microphone the perfect tool for precise measurements of time signals, frequency distributions and acoustic field maps of ultrasound emitters such as air-coupled ultrasonic piezos.
Measurements in High Electromagnetic Field
All-optical components in the sensor head as well as the optical fiber cabling are insensitive to strong electromagnetic fields. Thus, sound can be recorded in applications that are out of reach for classical microphones due to strong EM- or radioactive fields.
Ultra-high Sound Pressure Levels
The Eta100 Ultra was designed to measure extremely high sound pressure levels (up to 180dB SPL). All our microphones are immune to damage by excessive acoustic pressure levels.
Advantages
XARION’s patent-protected sensor technology platform offers substantial advantages:
- Extreme ultrasound frequency range from 10 Hz up to 2 MHz in air, 20 MHz in liquids
- Acoustic and ultrasound detection greater by a factor of 10 than present state-of-the art
- Transducer principle with a perfectly linear frequency response. Although the enclosure needs to be carefully designed to minimize its influence on the sound field, the transducer itself is not frequency dependent
- Sound detection in air and liquids
- Qualification for ultra-high sound pressure levels (up to 190 dB SPL)
- Since no moving inert mass is involved, the Optical Microphone has a true temporal impulse response.
- Inherent phase match in array configurations
- No metallic parts and glass fiber-coupled, hence operational in high electromagnetic fields.
Publications
Listening to Ultrasound with a Laser
All-optical highly sensitive akinetic sensor for ultrasound detection and photoacoustic imaging
Characterization of polymer-based piezoelectric micromachined ultrasound transducers for short-range gesture recognition applications
Development of an innovative measurement system for audible noise monitoring of overhead lines
Optical microphone hears ultrasound
Videos
Demonstration of Frequency Bandwidth
✔The Optical Microphone is able to detect the entire acoustic frequency bandwidth which is transmitted through air
✔High frequencies often contain significant process-quality information
✔Hence, disturbing background noise (low frequencies) can be separated from process information (high frequencies)
Technology
For the detection of sound waves, conventional microphones use membranes or other moving parts as intermediaries between the incoming acoustic and the resulting electrical quantity. For acoustic ultrasound sensors based on piezoelectric crystals, the approach is similar: the acoustic wave mechanically deforms the crystal. In contrast, the patented idea behind XARION’s Optical Microphone is to exploit another, completely different property of sound: the fact that sound changes the speed of light! In a rigid Fabry-Pérot laser interferometer consisting of two miniaturized mirrors, sound pressure changes the refractive index of the air. This alters the optical wavelength and the light transmission which consequently leads to the respective electrical signal. In contrast to conventional microphones, the Optical Microphone is the world’s first microphone without any moving parts. No mechanically movable or physically deformable parts are involved. By consequence, the sensors exhibit a compelling frequency bandwidth, free from mechanical resonances. The sensor principle is highly sensitive. In fact, refractive index changes below 10-14 can be detected with this technology. This corresponds to pressure changes as small as 1 µPa.
