Surgery – Truss – Pad
Patent
1978-12-04
1981-03-31
Michell, Robert W.
Surgery
Truss
Pad
307311, 328 2, A61B 502
Patent
active
042587190
ABSTRACT:
A pulsed IR reflectance plethysmograph for heart rate measurement and display in a digital watch or as a medical instrument using, for example, a pulsed LED light emitting diode for transmitting light pulses and a photodiode for receiving light pulses reflected from a finger. The LED and photodiode are mounted in a small sensor on the watch or medical instrument. The photodiode is connected directly to a signal conditioning circuit which rapidly removes unwanted asynchronous ambient background light signals such as from sunlight, by means of a switched ambient light subtractor circuit which performs the subtraction without requiring amplification or conversion of the detector signal photocurrent to another electrical parameter. The signal current after cancellation of the ambient background signal is sampled in an integrate and hold circuit to provide a heart systolic pressure wave. The synchronous steady state IR pulse carrier envelope signal is cancelled by a perfect second-order feedback loop via an integrating amplifier and a switched transconductance element that operates with fast response, even under conditions of large overloads that occur at the sensor. Pulses of the heart systolic pressure wave are then detected to determine the pulse rate which is displayed. When only the presence of an unmodulated IR light carrier is to be detected, as in an IR light beam detector, an ambient light subtractor in accordance with the invention is provided in an unswitched configuration that removes ambient light with a minimum number of components over an extremely wide dynamic range.
REFERENCES:
patent: 3328590 (1967-06-01), Kapsambelis
patent: 3408578 (1968-10-01), Smith
patent: 3790288 (1974-02-01), Hostetter
patent: 3857047 (1974-12-01), Knight
patent: 3970840 (1976-07-01), De Bruine
patent: 4047023 (1977-09-01), Key et al.
patent: 4063551 (1977-12-01), Sweeney
patent: 4166454 (1979-09-01), Meijer
Adam Walter J.
Hughes Aircraft Company
Jaworski Francis J.
MacAllister W. H.
Michell Robert W.
LandOfFree
Heart rate measurement system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heart rate measurement system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heart rate measurement system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2238223