Photoplethysmography sensor apparatus and method
AssigneeKoninklijke Philips N.V.
InventorsOlaf Thomas Johan Antonie Vermeulen, Koen Geenen
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Abstract
The present invention relates to a photoplethysmography sensor apparatus (200, 300), a photoplethysmography sensor method (400), and a photoplethysmography sensor computer program product. It is proposed to measure a photoplethysmographic signal without ambient light interference. Ambient light signals are rejected by subtraction of a compensation current at the input of a transimpedance amplifier (240, 340). The compensation current is controlled via a closed loop, without interfering with the low duty cycle operation of a photoplethysmography LED (210, 310).
Claims14
A photoplethysmography sensor apparatus comprising:
- a light source unit configured to generate a first light signal;
- a photodetector unit configured to observe a second light signal, where said second light signal is indicative of an absorption of said first light signal in a target, wherein said photodetector unit is further configured to output a photodetector output signal in response to observing said second light signal;
- and
- an ambient light compensating feedback loop comprising a track-and-hold unit configured to receive said photodetector output signal;
- wherein said photoplethysmography sensor apparatus is configured to compare an output signal of said track-and-hold unit to a reference signal (VR), and wherein said ambient light compensating feedback loop comprises a first amplifying unit configured to provide a compensation current based on said comparison to the track-and-hold unit.
A photoplethysmography sensor method comprising the steps of:
- generating a first light signal by a light source unit;
- observing a second light signal by a photodetector unit, wherein said second light signal is indicative of an absorption of said first light signal in a target;
- receiving, in response to observing said second light signal, a photodetector output signal by an ambient light compensating feedback loop comprising a track-and-hold unit and an amplifying unit;
- comparing an output signal of the track-and-hold unit to a reference signal (VR), wherein said output signal of said track-and-hold unit is based on said photodetector output signal;
- and
- providing a compensation current by the amplifying unit to the track-and-hold unit based on said comparison.
A photoplethysmography sensor computer program product comprising a computer readable memory storing computer program code means for causing a photoplethysmography sensor apparatus to carry out the following steps, when the program is run on a computer controlling the photoplethysmography sensor apparatus:
- generate a first light signal by a light source unit;
- observe a second light signal by a photodetector unit, wherein said second light signal is indicative of an absorption of said first light signal in a target;
- receive, in response to observing said second light signal, a photodetector output signal by an ambient light compensating feedback loop comprising a track-and-hold unit and an amplifying unit;
- compare an output signal of the track-and-hold unit to a reference signal (VR), wherein said output signal of said track-and-hold unit is based on said photodetector output signal;
- and
- provide a compensation current by the amplifying unit to the track-and-hold unit based on said comparison.
Dependencies are inferred from the claim text.