US 2017/0245803 A1Published application

Bio-sensing device with ambient light cancellation

AssigneeTexas Instruments Incorporated

InventorsHussam AHMED, Jagannathan VENKATARAMAN, Sandeep Kesrimal OSWAL, Antoine Lourdes Praveen AROUL, Hari Babu TIPPANA, Anand Hariraj UDUPA

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Abstract

A bio-sensing device (and method) calibrates a time period used to make bio-physical measurements. The device initiates a light source sense phase followed by a first ambient sense phase and a second ambient sense phase. In the light source sense phase, the device is configured to receive a digital value indicative of current through a photodetector while the light source circuit is enabled and in each of the first and second ambient sense phases, the device is configured to receive digital values while the light source circuit is disabled. The device iteratively varies the time period between the phases until the digital value received during the first ambient sense phase is within a threshold of the digital value received during the second ambient sense phase. It then applies the same time separation between the light source sense phase and the ambient phase thereby equalizing the magnitude of the ambient light in the two phases.

Claims20

Dependent claims

A bio-sensing device, comprising:

a light source circuit;
a first photodetector;
a transimpedance amplifier coupled to the first photodetector and configured to convert a current produced by the photodetector to a voltage;
an analog-to-digital converter (ADC) coupled to the transimpedance amplifier and configured to convert the voltage from the first photodetector to a digital value;
and
a controller coupled to the ADC and the light source circuit and configured to:
initiate a light source sense phase followed by a first ambient sense phase and a second ambient sense phase, wherein in the light source sense phase, the controller is configured to receive a digital value from the ADC while the light source circuit is enabled and wherein in each of the first and second ambient sense phases, the controller is configured to receive a digital value from the ADC while the light source circuit is disabled, wherein a first time period between the light source sense phase and the first ambient sense phase is equal to a second time period between the first and second ambient sense phases;
and
iteratively vary the second time period, while maintaining the first and second time periods equal, until the digital value received during the first ambient sense phase is within a threshold of the digital value received during the second ambient sense phase.

6 more elements

A system, comprising:

a first photodetector coupled to a first transimpedance amplifier and configured to convert a current produced by the first photodetector to a voltage;
a second photodetector coupled to a second transimpedance amplifier and configured to convert a current produced by the second photodetector to a voltage;
an analog-to-digital converter (ADC) configured to convert voltages from the first and second transimpedance amplifiers to corresponding digital values;
and
a controller coupled to the ADC and configured to:
iteratively read digital values from the ADC generated from the second photodetector while a light source is disabled during a plurality of sets of first and second ambient sense phases, wherein the first ambient sense phase is separated from the second ambient sense phase of a given set by a variable time separation, the time separation adjusted for each subsequent set of first and second ambient sense phases;
compute a difference between the digital values read during each set of ambient sense phases;
determine the approximate period of the ambient light from processing the computed differences;
and
using the determined approximate ambient light period, configure a time separation between a light source sense phase in which the light source is enabled and an ambient sense phase in which the light source is disabled.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/298,764Filed 20 Oct 2016
Priority: 29 Feb 2016
Published: 31 Aug 2017
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

A61B 5/7225
Signal processing specially adapted for physiological signals or for diagnostic purposes: details of analogue processing, e.g. isolation…
A61B 5/02416
Measuring pulse rate or heart rate: using photoplethysmograph signals, e.g. generated by infrared radiation
A61B 5/681
Sensor mounted on worn items: wristwatch-type devices
A61B 5/7203
Signal processing specially adapted for physiological signals or for diagnostic purposes: for noise prevention, reduction or removal