Photoplethysmographics using phase-division multiplexing
First Claim
1. An instrument for evaluating the concentration of a constituent in an object by measuring the transmission of light of two wavelengths therethrough, comprising:
- (a) first and second light emitter means for emitting light at respective, first and second different wavelengths;
(b) modulator/driver means for driving the light emitter means simultaneously with respect first and second carriers which vary as a function of time, the carriers being continuous time-varying signals of the same carrier frequency and having a phase difference other than 0°
degrees and other than an integer multiple of 180°
degrees, wherein said first and second light emitter means have at least one time period when they are both substantially emitting;
(c) detector means disposed to receive light from the first and second light emitter means after it has passed through the object, for generating a resulting detector signal carrying information relating to transmission of the object at both wavelengths;
(d) demodulator means for generating, in response to the detector signal, in a first channel, a first demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the first wavelength and one or more carrier modulated components, and, in a second channel, a second demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the second wavelength and one or more carrier modulated components; and
(e) a demodulated signal filter, coupled to said first and second channels, wherein said demodulated signal filter filters out carrier modulated components of the signals from the first and second channels.
4 Assignments
0 Petitions
Accused Products
Abstract
First and second carrier signals, distinguishable by phase, are respectively applied to infrared and red energy emitters. A detector receives the sum of the energy after modulation at the infrared and red wavelengths. The signal received by the detector is then demultiplexed into its original first and second components, thereby allowing determining of both the infrared and red modulation components. The first and second carrier signals may comprise time-varying periodic signals with identical frequency and frequency spectra, such as a pair of sine waves which are indistinguishable except by phase and amplitude. A 90° phase difference is preferred, but any phase other than 0 or an integer multiple of 180° is workable. A carrier frequency which avoids excessive interference from ambient light is preferred.
-
Citations
56 Claims
-
1. An instrument for evaluating the concentration of a constituent in an object by measuring the transmission of light of two wavelengths therethrough, comprising:
-
(a) first and second light emitter means for emitting light at respective, first and second different wavelengths; (b) modulator/driver means for driving the light emitter means simultaneously with respect first and second carriers which vary as a function of time, the carriers being continuous time-varying signals of the same carrier frequency and having a phase difference other than 0°
degrees and other than an integer multiple of 180°
degrees, wherein said first and second light emitter means have at least one time period when they are both substantially emitting;(c) detector means disposed to receive light from the first and second light emitter means after it has passed through the object, for generating a resulting detector signal carrying information relating to transmission of the object at both wavelengths; (d) demodulator means for generating, in response to the detector signal, in a first channel, a first demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the first wavelength and one or more carrier modulated components, and, in a second channel, a second demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the second wavelength and one or more carrier modulated components; and (e) a demodulated signal filter, coupled to said first and second channels, wherein said demodulated signal filter filters out carrier modulated components of the signals from the first and second channels. - View Dependent Claims (2, 6, 7)
-
-
3. An instrument for evaluating the concentration of a constituent in object by measuring the transmission of light of two wavelengths therethrough, comprising:
-
(a) first and second light emitter means for emitting light at respective, first and second different wavelengths; (b) modulator/driver means for driving the light emitter means simultaneously with respective first and second sinusoidal carriers which are of the same carrier frequency and having a phase difference other than 0°
degrees and other than an integer multiple of 180°
degrees, wherein said first and second light emitter means have at least one time period when they are both substantially emitting;(c) detector means disposed to receive light from the first and second light emitter means after it has passed through the object, for generating a resulting detector signal carrying information relating to transmission of the object at both wavelengths; (d) demodulator means for, in a first channel, multiplying the detector signal with a sinusoidal signal in phase with the first carrier to generate a first demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the first wavelength and one or more carrier modulated components, and for, in a second channel, multiplying the detector signal with a sinusoidal signal in phase with the second carrier to generate a second demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the second wavelength and one or more carrier modulated components; and (e) a demodulated signal filter, coupled to said first and second channels, wherein said demodulated signal filter filters out carrier modulated components of the signals from the first and second channels. - View Dependent Claims (4, 5, 8)
-
-
9. A method for evaluating the concentration of a constituent in an object, comprising:
-
(a) simultaneously driving a first and a second light emitter, which emit light at different wavelengths, with respective first and second carriers which vary continuously as a function of time and are of the same carrier frequency and having a phase difference other than 0°
degrees and other than an integer multiple of 180°
degrees, wherein said first and second light emitters have at least one time period when they are both substantially emitting;(b) directing the light from the emitters through the object; (c) receiving the light from the emitters at a detector after it has passed through the object, which detector generates a detector signal carrying information relating to transmission of the object at both wavelengths; (d) demodulating the detector signal to generate, in a first channel, a first demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the first wavelength and one or more carrier modulated components, and, in a second channel, a second demodulated signal which is a sum of a component proportional to the object'"'"'s transmission at the second wavelength and one or more carrier modulated components; (e) filtering out carrier modulated components of the first and second demodulated signals and (f) evaluating the concentration of oxygen from the demodulated and filtered signals.
-
-
10. A method for evaluating the oxygen concentration in a body structure of an animal, comprising:
-
(a) simultaneously driving a first and a second light emitter, which emit light in the red and infra-red regions, respectively, with respective first and second sinusoidal carriers of the same carrier frequency and having a phase difference other than 0°
degrees and other than an integer multiple of 180°
degrees, wherein said first and second light emitters have at least one time period when they are both substantially emitting;(b) directing the light from the emitters through the body structure; (c) receiving the light from the emitters at a detector after it has passed through the body structure, which detector generates a detector signal carrying information relating to transmission of the body structure at both wavelengths; (d) demodulating the detector signal to generate, in a first channel, a first demodulated signal which is a sum of a component proportional to the body structure'"'"'s transmission of red light, and one or more carrier modulated components, and, in a second channel, a second demodulated signal which is a sum of a component proportional to the body structure'"'"'s transmission of infra-red light and one or more carrier modulated components; (e) filtering out carrier modulated components of the first and second demodulated signals; (f) evaluating the concentration of oxygen from the demodulated and filtered signals. - View Dependent Claims (11)
-
-
12. A device for collecting photoplethysmographic data, comprising
means for generating a first and a second signal, said first and second signals being distinguishable by phase; -
means for simultaneously applying said first and second signals to a modulating medium, said means for simultaneously applying comprising a first and second emitter, said first and second emitters having at least one time period when they are both substantially emitting; means for detecting a composite signal at an output of said modulating medium, said modulating medium having a first and a second modulating effect; and means for generating a first and a second output signal responsive to said composite signal, said first output signal indicating said first modulating effect and said second output signal indicating said second modulating effect, said means for generating comprising means for multiplying at least part of said composite signal with a continuous time-varying signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
-
-
34. A device for collecting photoplethysmographic data, comprising
means for phase-division multiplexing a plurality of modulating signals; -
means for modulating a resultant of said means for phase-division multiplexing; and means for phase-division demultiplexing said plurality of signals, in response to a resultant of said means for modulating, said means for phase-division demultiplexing comprising means for multiplying at least part of a resultant of said means for modulating with a continuous time-varying signal. - View Dependent Claims (35, 36)
-
-
37. A method of collecting photoplethysmographic data, comprising the steps of
generating a first and a second signal, said first and second signals being distinguishable by phase; -
simultaneously applying said first and second signals to a modulating medium, including substantially emitting in response to said first signal and substantially emitting in response to said second signal, both during at least one time period; detecting a composite signal at an output of said modulating medium, said modulating medium having a first and a second modulating effect; and generating a first and a second output signal responsive to said composite signal, said first output signal indicating said first modulating effect and said second output signal indicating said second modulating effect, said step of generating comprising multiplying at least part of said composite signal with a continuous time-varying signal. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
-
-
52. A method of collecting photoplethysmographic data, comprising the steps of
phase-division multiplexing a plurality of modulating signals; -
modulating a resultant of said step of phase-division multiplexing; and phase-division demultiplexing said plurality of signals, in response to a resultant of said step of modulating, said step of phase-division demultiplexing comprising multiplying at least part of a resultant of said step of modulating with a continuous time-varying signal. - View Dependent Claims (53)
-
-
54. A device for collecting photoplethysmographic data, comprising
means for generating a first and a second signal, said first and second signals being distinguishable by phase; -
means for applying said first and second signals to a modulating medium, said means for applying comprising a first and second emitter, said first and second emitters having at least one time period when they are both substantially emitting; means for detecting a composite signal at an output of said modulating medium, said modulating medium having a first and a second modulating effect; means for sampling said composite signal at a rate higher than a frequency component of said first signal; and means for generating a first and a second output signal responsive to said composite signal, said first output signal indicating said first modulating effect and said second output signal indicating said second modulating effect. - View Dependent Claims (55, 56)
-
Specification