LIGHT FIELD MANAGEMENT IN AN OPTICAL BIOLOGICAL PARAMETER SENSOR

• US 20170164848A1
• Filed: 12/06/2016
• Published: 06/15/2017
• Est. Priority Date: 12/10/2015
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Nadeau, Kyle P., Sarantos, Chris H.
• Granted Patent: US 11,206,989 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 2562/04 Arrangements of multiple sensors of the same type
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: G02B 27/425 in illumination systems mask illumination systems in photolithographic systems G03F7/70158
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876

Abstract

Structures and techniques are provided for shaping or steering a light field for an optical biological parameter sensor such that the light is partially or wholly collimated and enters a person'"'"'s skin at an oblique angle to the person'"'"'s skin such that the light has a direction component oriented towards or away from a photodetector of the optical biological parameter sensor.

Claims

1. An apparatus comprising:

a collimating light source assembly, the collimating light source assembly configured to emit partially or wholly collimated light having a first angular distribution with a first angular centroid defining a first angular direction;

one or more first photodetectors; and

a first optical light field redirector positioned so as to receive at least some of the partially or wholly collimated light emitted by the collimating light source assembly and configured to redirect the received partially or wholly collimated light such that the redirected received partially or wholly collimated light has a second angular distribution with a second angular centroid defining a second angular direction having a directional component extending towards the one or more first photodetectors to a greater extent than a corresponding directional component of the first angular direction.

2. The apparatus of claim 1, further comprising a first light barrier interposed between the collimating light source assembly and the one or more first photodetectors.

3. The apparatus of claim 2, wherein the first light barrier has a first surface facing towards the collimating light source assembly and a second surface facing towards the one or more first photodetectors, wherein the first surface and the second surface define a mid-plane between them that is within ±

10°

of parallel with the first angular direction.

4. The apparatus of claim 2, wherein the first light barrier has a first surface facing towards the collimating light source assembly and a second surface facing towards the one or more first photodetectors, wherein the first angular direction is within ±

10°

of parallel with the average normal vector defined by the first surface and the second surface.

5. The apparatus of claim 2, further comprising a window with one or more transparent portions, wherein:

the first light barrier interfaces with the window such that light from the collimating light source assembly does not have a direct optical path from the side of the first light barrier facing towards the collimating light source assembly to the side of the first light barrier facing towards the one or more first photodetectors,

one of the one or more transparent portions extends over the collimating light source assembly,

one of the one or more transparent portions extends over the one or more first photodetectors, and

the first optical light field redirector is provided by optical light-turning features molded into the window in the transparent portion extending over the collimating light source assembly.

6. The apparatus of claim 1, wherein the intensity of light in the second angular distribution associated with the first angular direction is less than the intensity of light in the first angular distribution associated with the first angular direction.

7. The apparatus of claim 1, further comprising control logic including a memory and one or more processors, wherein:

the memory, the one or more processors, the collimating light source assembly, and the one or more first photodetectors are operably connected, and

the memory stores computer-executable instructions for controlling the one or more processors to;

cause the collimating light source assembly to emit light,

obtain detected light measurements from the one or more first photodetectors in association with the emission of light from the collimating light source assembly, and

determine a biological parameter based at least in part on the detected light measurements.

8. The apparatus of claim 7, wherein the memory stores computer-executable instructions for controlling the one or more processors to:

obtain a photoplethysmogram from the detected light measurements, and

determine the biological parameter from the photoplethysmogram.

9. The apparatus of claim 7, wherein the biological parameter is selected from the group consisting of:

heart rate, blood oxygen saturation (SpO₂), respiration rate, blood perfusion, hydration level, tissue oxygen saturation (StO₂), tissue metabolic rate, melanin composition, structural orientation of collagen tissue fibers, structural orientation of muscle fibers, bulk cell size, bulk cell density, extracellular matrix size, and extracellular matrix density.

10. The apparatus of claim 1, wherein the first angular direction and the second angular direction form an included angle between them of between 5°

and 50°

.

11. The apparatus of claim 1, wherein the collimating light source assembly includes:

a light source; and

a Fresnel lens interposed between the light source and the first optical light field redirector, wherein the Fresnel lens is configured to partially or wholly collimate light from the light source and direct the partially or wholly collimated light towards the first optical light field redirector.

12. The apparatus of claim 1, wherein the collimating light source assembly includes:

one or more light sources; and

one or more optical reflectors, wherein;

each optical reflector has a corresponding light source, and

the one or more optical reflectors are configured to reflect light from the corresponding light sources to generate the partially or wholly collimated light having the first angular distribution.

13. The apparatus of claim 1, wherein the collimating light source assembly includes:

a light source; and

a diffractive optic interposed between the light source and the first optical light field redirector, wherein the diffractive optic is configured to partially or wholly collimate light from the light source and direct the collimated light towards the first optical light field redirector.

14. The apparatus of claim 1, further comprising a window with one or more transparent portions, wherein:

one of the one or more transparent portions extends over the collimating light source assembly,

one of the one or more transparent portions extends over the one or more first photodetectors, and

the first optical light field redirector is provided by optical light-turning features molded into the window in the transparent portion extending over the collimating light source assembly.

15. The apparatus of claim 1, further comprising one or more optical light field collection optics positioned so as to receive sample-modulated light traveling along a first direction having a component opposite the first angular direction, wherein:

the received sample-modulated light has a third angular distribution with a third angular centroid defining a third angular direction, and

the one or more optical light field collection optics are configured to redirect the received sample-modulated light such that the redirected received sample-modulated light has a fourth angular distribution with a fourth angular centroid defining a fourth angular direction that is tilted away from the one or more first photodetectors to a lesser extent than the third angular direction.

16. The apparatus of claim 1, further comprising an optical lens positioned so as to receive sample-modulated light traveling along a first direction having a directional component opposite the first angular direction and having a third angular distribution with a first half-height width, wherein:

the optical lens is configured such that the sample-modulated light, after passing through the optical lens, has a fourth angular distribution with a second half-height width that is less than the first half-height width.

17. The apparatus of claim 1, further comprising:

one or more second photodetectors; and

a second optical light field redirector positioned so as to receive at least some of the partially or wholly collimated light emitted by the collimating light source assembly and configured to redirect the received partially or wholly collimated light such that the redirected received partially or wholly collimated light has a third angular light distribution with a third angular centroid defining a third angular direction having a directional component extending towards the one or more second photodetectors to a greater extent than a corresponding directional component of the first angular direction.

18. The apparatus of claim 17, further comprising:

at least one or more additional photodetectors; and

at least one or more additional optical light field redirectors, wherein;

the one or more first photodetectors, the one or more second photodetectors, and the at least one or more additional photodetectors are located within an annular area centered on the collimating light source assembly, and

each of the one or more additional optical light field redirectors is positioned so as to receive at least some of the partially or wholly collimated light emitted by the collimating light source assembly and is configured to redirect the received partially or wholly collimated light such that the redirected received partially or wholly collimated light has an angular light distribution with an angular centroid defining a an angular direction having a directional component extending towards a corresponding one of the at least one or more additional photodetectors to a greater extent than a corresponding directional component of the first angular direction.

19. The apparatus of claim 17, further comprising:

a first light barrier interposed between the collimating light source assembly and the one or more first photodetectors; and

a second light barrier interposed between the collimating light source assembly and the one or more second photodetectors.

20. An apparatus comprising:

a collimating light source assembly, the collimating light source assembly configured to emit partially or wholly collimated light having a first angular distribution with a first angular centroid defining a first angular direction; and

one or more first photodetectors defining, in aggregate, a substantially planar photosensitive surface, wherein the first angular direction is at an angle of between 5° and

50°

with respect to a normal vector of the substantially planar photosensitive surface and includes a directional component that is directed towards the first photodetector.

21. The apparatus of claim 20, further comprising a first light barrier interposed between the collimating light source assembly and the one or more first photodetectors.

22. The apparatus of claim 20, wherein:

the collimating light source assembly is a surface-mount laser diode that is surface-mounted on a printed circuit and configured to emit laser light along a direction normal to the printed circuit with respect to a surface of the printed circuit at a location corresponding with the surface-mount laser diode, and

the printed circuit is positioned in space relative to the first photodetector such that a major plane of the printed circuit is at an angle of between 5° and

50°

with respect to the substantially planar photosensitive surface.

23. The apparatus of claim 20, wherein the collimating light source assembly includes:

one or more light sources; and

one or more optical reflectors, wherein;

each optical reflector has a corresponding light source, and

the one or more optical reflectors are configured to reflect light from the corresponding light sources to generate the partially or wholly collimated light having the first angular distribution.

24. The apparatus of claim 23, wherein the one or more light sources are arranged in an array that is substantially parallel to the substantially planar photosensitive surface.

25. The apparatus of claim 23, wherein the one or more light sources are arranged in an array that is within 5°

to 50°

of parallel with the substantially planar photosensitive surface.