US 5,291,013 AGranted

Fiber optical monitor for detecting normal breathing and heartbeat motion based on changes in speckle patterns

AssigneeAlamed Corporation

InventorsAntonio B. Nafarrate, Eric G. Rawson

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Abstract

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.

Claims61

Dependent claims

A fiber optic body motion monitor comprising:

a light source;
an optical fiber waveguide including an input end, an output end, and a sensing section intermediate said input and output ends, said optical fiber being positioned to receive light from said light source at said input end;
movable means for transmitting motion of a body being monitored, said sensing section being coupled to said movable means so as to move therewith;
photodetector means positioned proximate to said output end for receiving a speckle pattern of light therefrom, which pattern changes in response to movement of said sensing section, said photodetector means generating electrical signals representative of changes in said speckle pattern;
and
means for identifying electrical signals indicative of normal breathing and heartbeat motion and for differentiating them from electrical signals indicative of deviations from normal breathing and heartbeat motion, comprising,
power determination means for producing a power signal indicative of an amount of power in a frequency band relevant to breathing and heartbeat in the signals generated by said photodetector means,
breathing extraction means coupled to said power determination means for extracting from said power signal signals indicative of breathing of said body and outputting a signal indicative of the breathing of said body,
heartbeat extraction means coupled to said power determination means for extracting from said power signal signals indicative of heartbeat of said body and outputting a signal indicative of the heartbeat of said body, and
indicating means for producing at least one of a display indicative of at least one of the extracted breathing signals and the extracted heartbeat signals and an alarm when at least one of the extracted breathing signals and extracted heartbeat signals is indicative of a deviation from normal breathing and heartbeat motion, respectively.

7 more elements

A fiber optic body motion monitor comprising:

a light source;
an optical fiber waveguide including an input end, an output end, and a sensing section intermediate said input and output ends, said optical fiber being positioned to receive light from said light source at said input end;
movable means for transmitting motion of a body being monitored, said sensing section being coupled to said movable means so as to move therewith;
photodetector means positioned proximate to said output end for receiving a speckle pattern of light therefrom, which pattern changes in response to movement of said sensing section, said photodetector means generating electrical signals representative of changes in said speckle pattern;
and
means for identifying electrical signals indicative of normal breathing and heartbeat motion and for differentiating them from electrical signals indicative of deviations from normal breathing and heartbeat motion, comprising,
power determination means for producing a power signal indicative of an amount of power in a frequency band relevant to breathing in the signals generated by said photodetector means,
breathing extraction means coupled to said power determination means for extracting from said power signal signals indicative of breathing of said body and outputting a signal indicative of the breathing of said body, comprising,
low pass filter means for passing signals in a passband in which breathing signals have significant content,
threshold means for detecting when signals passed by said bandpass filter means exceed a threshold,
processor means for generating said signal indicative of breathing based on signals detected by said threshold means, and
indicating means for producing at least one of a display of said signal indicative of breathing and an alarm when said signal indicative of breathing is indicative of a deviation from normal breathing.

9 more elements

A fiber optic body motion monitor comprising:

a light source;
an optical fiber waveguide including an input end, an output end, and a sensing section intermediate said input and out ends, said optical fiber being positioned to receive light from said light source at said input end;
movable means for transmitting motion of a body being monitored, said sensing section being coupled to said movable means so as to move therewith;
photodetector means positioned proximate to said output end for receiving a speckle pattern of light therefrom, which pattern changes in response to movement of said sensing section, said photodetector means generating electrical signals representative of changes in said speckle pattern;
and
means for identifying electrical signals indicative of normal breathing and heartbeat motion and for differentiating them from electrical signals indicative of deviations from normal breathing and heartbeat motion, comprising,
power determination means for producing a power signal indicative of an amount of power in a frequency band relevant to heartbeat in the signals generated by said photodetector means,
heartbeat extraction means coupled to said power determination means for extracting from said power signal signals indicative of heartbeat of said body and outputting a signal indicative of the heartbeat of said body, comprising,
bandpass filter means for passing signals in a passband in which breathing signals have significant content,
threshold means for detecting when signals passed by said bandpass filter means exceed a threshold,
processor means for generating said signal indicative of heartbeats based on signals detected by said threshold means, and
indicating means for producing at least one of a display of said signal indicative of heartbeats and an alarm when said signal indicative of heartbeats is indicative of a deviation from normal heartbeats.

9 more elements

A fiber optic motion monitor comprising:

a light source;
an optical fiber waveguide including an input end, an output end, and a sensing section intermediate said input and output ends, said optical fiber being positioned to receive light from said light source at said input end;
movable means for transmitting motion of an object being monitored, said sensing section being coupled to said movable means so as to move therewith;
photodetector means positioned proximate to said output end for receiving a speckle pattern of light therefrom, which pattern changes in response to movement of said sensing section, said photodetector means generating electrical signals representative of changes in said speckle pattern;
and
means for processing said electrical signals to identify predetermined variations in said electrical signals, comprising,
power determination means for producing a power signal indicative of an amount of power in a predetermined frequency band in the electrical signals generated by said photodetector means,
extraction means coupled to said power determination means for extracting from said power signal signals indicative of said predetermined variations, a signal indicative of the predetermined variations comprising,
filter means for passing signals in said predetermined frequency band in which predetermined variations have significant content,
threshold means for detecting when signals passed by said filter means exceed a threshold, and
processor means for generating said signal indicative of said predetermined variations based on signals detected by said threshold means, and
indicating means for producing at least one of a display of said signal indicative of predetermined variations and an alarm when said signal indicative of predetermined variations is indicative of a deviation from a predetermined range.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/975,853Filed 13 Nov 1992 · continuation in part
Priority: 6 Dec 1991
Granted: 1 Mar 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

A61B 5/6892
Mounted on external non-worn devices, e.g. non-medical devices: mats
A61B 5/02444
Measuring pulse rate or heart rate: details of sensor
A61B 5/113
Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb: occurring during breathing
G01P 13/00
Indicating or recording presence, absence, or direction, of movement