Systems and methods for optically sensing characteristics of a blood flow
View Patent ↗Systems and methods for optically sensing characteristics of a blood flow provide a light source having a driver circuit that includes a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source. The systems and methods also include a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity. A receiver circuit including a bandpass filter is coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency.
1. An assembly for optically sensing characteristics of a blood flow comprising
a light source,
a driver circuit for the light source including a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source,
a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity, and
a receiver circuit including a bandpass filter coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency.
2. An assembly according to claim 1
wherein the selected carrier frequency is below the frequency components comprising electromagnetic interference.
3. An assembly according to claim 1
wherein the selected carrier frequency is above the frequency components comprising ambient light.
4. A method for optically sensing characteristics of a blood flow comprising the steps of
providing a light source having a driver circuit that includes a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source,
providing a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity, and
providing a receiver circuit including a bandpass filter coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency.
5. A method according to claim 4
wherein the selected carrier frequency is below the frequency components comprising electromagnetic interference.
6. A method according to claim 4
wherein the selected carrier frequency is above the frequency components comprising ambient light.