Methods and systems for modulation and demodulation of optical signals
AssigneeApple Inc.
InventorsSteven P. Hotelling, Marcelo M. Lamego
Life of this patent
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Abstract
An electronic device includes one or more light sources for emitting light toward a body part of a user and one or more optical sensors for capturing light samples while each light source is turned on and for capturing dark samples while the light source(s) are turned off. A signal produced by the one or more optical sensors is filtered and demodulated produce multiple demodulated signals each associated with a light source. Each signal associated with the light source(s) is analyzed to estimate or determine a physiological parameter of the user.
Claims20
An electronic device comprising:
- a housing comprising a surface adapted to be positioned proximate a measurement site of a subject;
- a biometric sensor positioned at least partially within the surface and comprising:
- a plurality of light sources for emitting light toward the measurement site at a selected modulation frequency;
- and
- an optical sensor for obtaining light exiting the measurement site;
- and
- an input amplifier coupled to the output of the biometric sensor and disposed within the housing;
- a high pass filter coupled to an output of the input amplifier and disposed within the housing, the high pass filter having a cutoff frequency above that of a periodic biometric property of the measurement site;
- an output amplifier coupled to an output of the high pass filter and disposed within the housing;
- and
- an analog to digital converter coupled to an output of the output amplifier and disposed within the housing.
A sensor system for measuring a periodic biometric characteristic of a subject, the sensor system comprising:
- a plurality of light sources operative to emit a series light pulses at a selected modulation frequency toward a measurement site of the subject;
- an optical sensor operative to receive light exiting a portion of the measurement site, the light originating from the series of light pulses;
- a transimpedance input amplifier coupled to the output of the optical sensor;
- a high pass filter coupled to the transimpedance input amplifier and configured to filter frequencies lower than the selected modulation frequency;
- an output amplifier coupled of the high pass filter and configured to amplify an output of the high pass filter;
- and
- an analog to digital converter coupled to the output amplifier configured to associate a signal amplitude of the output amplifier with a digital value.
A method of optical sensing, comprising:
- emitting light toward a measurement site of a subject at a selected modulation frequency;
- obtaining light exiting the measurement site;
- converting the obtained light to an electrical signal;
- amplifying the electrical signal to obtain an amplified signal;
- filtering low frequency components below the selected modulation frequency from the amplified signal to obtain a filtered signal;
- and
- amplifying the filtered signal to obtain an output signal.
Dependencies are inferred from the claim text.