Patent ID: 7521668

Claim:
An optical audio microphone arrangement, comprising at least a sensor, arranged to be movable in response to sound waves and comprising a reflecting surface, a Michelson type interferometer for measuring the displacement of the sensor, comprising at least, a light source for generating a light beam, a reference mirror, a beam splitter for splitting the light beam from the light source for the sensor and for the reference mirror and for splitting the light beams reflected from the sensor and from the reference mirror, means for providing a phase difference between different parts of the light beams, and a group of at least two detectors arranged to receive light beams with a phase difference relative to each other, the light beams coming from the sensor and from the reference mirror via the beam splitter, the group of at least two detectors arranged to convert the received light beams into electric signals, wherein the microphone further comprises means for focusing the light beam coming from the light source and split by the beam splitter essentially on the surface of both the sensor and the reference mirror.