Alamed Corporation

Antonio B Nafarrate

Eric G Rawson

A fiber optic body motion monitor in which light is transmitted through an optical fiber waveguide physically coupled to a body being monitored, and modal noise at the output of the optical fiber waveguide is applied to a photodetector filtered, rectified and analyzed to detect breathing and heartbeats. Detection of breathing is performed by low-pass filtering the rectified and filtered signal, and adaptive thresholding of the low-pass filtered signal. A similar but separate technique is used to detect heartbeats. In one embodiment, reliability of detection is enhanced by reducing the number of speckles of light applied to the photodetector to approximately 50%, thereby to maximize modal noise current. In another embodiment the photodetector has two halves separately illuminated by approximately two-thirds of the light from the optical fiber waveguide. Outputs of the photodetector halves are applied to the positive and negative inputs of an operational amplifier, whereby common mode noise is eliminated and modal noise current and therefore sensitivity of modal noise detection increased.

Fiber optical monitor for detecting normal breathing and heartbeat

A motion monitor using coherent or partially coherent light passing through an optical fiber which is in contact or close to an object whose motion is to be monitored. An optical speckle pattern is formed near the output of the optical fiber which pattern changes as the fiber moves in response to the motion of the object being monitored. An optical detector monitors all or a part of the speckle pattern and electronically processes the optical detector's electrical output signals to derive information on the status of the object being monitored.

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San Jose, CA, United States of America

Antonio B Nafarrate