Sensor and method for continuous health monitoring
An optical proximity sensor assembly includes an optical proximity sensor with an IR LED emitting light having an infrared wavelength, an IR photo detector sensitive to the infrared wavelength, an optical barrier blocking direct light rays from the LED to the IR photo detector and permitting reflected light rays to reach the at least one photo detector; and an electronic integrated circuit with an amplifier for amplifying a signal detected by the photo detector, an analog to digital converter, LED drivers, noise reduction and ambient light cancellation circuitry, and a digital interface for communication with a microcontroller. The optical proximity sensor is accommodated on a wearable carrier. A single sensor may include a plurality of identical or different LEDs, a plurality of photodiodes, or both. Also, several sensors may be placed on a person's skin along a vascular path to obtain data relating to blood flow and artery stiffness.
1. An optical proximity sensor assembly for cardiovascular monitoring, the optical proximity sensor assembly comprising:
an optical proximity sensor having
a first IR LED emitting light having an infrared wavelength;
a first IR photo detector sensitive to the infrared wavelength; and
an electronic integrated circuit with an amplifier for amplifying a signal detected by the first IR photo detector, an analog to digital converter, LED drivers, noise reduction and ambient light cancellation circuitry, and a digital interface for communication with a microcontroller; and
a wearable carrier accommodating the optical proximity sensor and configured for placing the optical proximity sensor in contact with skin;
wherein the wearable carrier is a clip wearable on an earlobe, the clip including the first IR LED and the first IR photo detector in a first portion of the clip to be placed on a first side of the earlobe and a metallic reflector in a second portion of the clip to be placed on a second side of the earlobe opposite the first side, the metallic reflector being arranged to reflect the light emitted by the first IR LED toward the first IR photo detector; and
wherein the clip includes a battery disposed in the second portion of the clip, wherein the battery has a reflective surface facing the first IR LED and the first IR photo detector that provides the metallic reflector.
2. The optical proximity sensor assembly of claim 1 , wherein the optical proximity sensor further comprises a transparent cover covering the first IR LED and the first IR photo detector.
3. The optical proximity sensor assembly of claim 1 , further comprising an optical barrier between the first IR LED and the first IR photo detector, the optical barrier blocking direct light rays from the first IR LED to the first IR photo detector and permitting reflected light rays to reach the first IR photo detector.
4. The optical proximity sensor assembly of claim 1 , wherein the analog-to-digital converter has at least a 12-bit resolution.
5. The optical proximity sensor assembly of claim 1 , further comprising a wireless transmission system and an electronic processor with an operating system compatible with a remote wireless device.
6. The optical proximity sensor assembly of claim 1 , wherein the optical proximity sensor further comprises a visible light blocking filter shielding the first IR photo detector.
7. The optical proximity sensor assembly of claim 1 , wherein the battery has a capacity sufficient to operate the optical proximity sensor assembly for at least 24 hours.
8. The optical proximity sensor assembly of claim 1 , wherein the first IR LED is pulsed.
9. The optical proximity sensor assembly of claim 8 , wherein the first IR LED is configured to operate in a low-duty-cycle mode by burst operation.
10. The optical proximity sensor assembly of claim 8 , wherein the first IR LED is pulsed at a frequency of at least 100 Hz.
11. The optical proximity sensor assembly of claim 8 , wherein the first IR LED is pulsed at a frequency of at least 1 kHz.
12. The optical proximity sensor assembly of claim 8 , wherein the first IR LED is pulsed with a pulse width of at most 100 μs.
13. The optical proximity sensor assembly of claim 1 , wherein the first IR LED, the first IR photo detector and other components of the optical proximity sensor assembly are arranged on two circuit boards.
14. The optical proximity sensor assembly of claim 13 , wherein at least the first IR LED and the first IR photo detector are arranged in a package covering an area of at most 1 cm 2 .
15. The optical proximity sensor assembly of claim 14 , wherein the area is at most 20 mm 2 .
16. The optical proximity sensor assembly of claim 15 , wherein the area is at most 17 mm 2 .
17. The optical proximity sensor assembly of claim 15 , wherein a first electronic board and a second electronic board are arranged on the clip, the clip forming electric conduits connecting the first and second electronic boards.
18. The optical proximity sensor assembly of claim 1 , further comprising a second LED.
19. The optical proximity sensor assembly of claim 18 , wherein the first IR LED and the second LED are pulsed at a different frequencies so as to enable frequency multiplexing.
20. The optical proximity sensor assembly of claim 18 , wherein the first IR LED and the second LED are pulsed in an alternating order so as to enable time multiplexing.
21. The optical proximity sensor assembly of claim 18 , wherein the second LED emits red light.
22. The optical proximity sensor assembly of claim 21 , wherein the first IR photo detector is also sensitive to the red light emitted by the second LED.