Integrated detector assemblies for a wearable module of an optical measurement system
An optical measurement system includes a wearable module having at least one time-resolved single photon photodetector configured to detect photons from at least one light pulse after the at least one light pulse is scattered by a target within a body of a user; at least one light guide configured to receive the photons and guide the photons to the at least one photodetector; and a housing that houses both the at least one photodetector and at least a portion of the at least one light guide. The optical measurement system further includes a signal processing circuit configured to determine a temporal distribution of the photons detected by the at least one photodetector and generate a histogram based on the temporal distribution of the photons.
1. An optical measurement system for time-domain near-infrared spectroscopy (TD-NIRS), the optical measurement system comprising:
a wearable module comprising:
a housing having an external surface that faces a body of a user when the wearable module is worn by the user;
a light source housed within the housing and configured to emit a light pulse;
an elongate light-emitting light guide configured to convey the light pulse toward a target within the body of the user, the light-emitting light guide having a proximal end portion housed within the housing and a distal end portion protruding from the external surface of the housing;
a plurality of time-resolved single photon photodetectors housed within the housing and configured to detect photons from the light pulse after the light pulse is scattered by the target; and
a plurality of elongate light-receiving light guides positioned equidistant from the light-emitting light guide and configured to receive the photons from the target and convey the photons toward the plurality of photodetectors, each light-receiving light guide having a proximal end portion housed within the housing and a distal end portion protruding from the external surface of the housing; and
a signal processing circuit configured to:
determine a temporal distribution of the photons detected by the plurality of photodetectors, and
generate a histogram based on the temporal distribution of the photons.
2. The optical measurement system of claim 1 , wherein:
the wearable module further comprises at least one time-to-digital converter (TDC), and
the at least one TDC is configured to measure a time difference between an occurrence of the light pulse and an occurrence of an output pulse generated by a photodetector included in the plurality of photodetectors, the output pulse indicating that the photodetector has detected a photon.
3. The optical measurement system of claim 1 , wherein the signal processing circuit is housed in the housing.
4. The optical measurement system of claim 1 , further comprising an additional housing separate from the housing,
wherein the signal processing circuit is housed in the additional housing and communicatively coupled with the plurality of photodetectors by way of a wired or wireless communication link.
5. The optical measurement system of claim 4 , wherein the additional housing is wearable by the user.
6. The optical measurement system of claim 1 , further comprising a head-mountable component configured to be worn on a head of the user,
wherein the wearable module is included in the head-mountable component.
7. The optical measurement system of claim 6 , wherein the head-mountable component comprises a plurality of wearable modules.
8. The optical measurement system of claim 1 , wherein the target comprises a brain of the user.
9. The optical measurement system of claim 1 , wherein each photodetector included in the plurality of photodetectors comprises a plurality of single-photon avalanche diode (SPAD) circuits.
10. The optical measurement system of claim 1 , further comprising:
a plurality of lenses housed within the housing and configured to direct the photons to the plurality of photodetectors,
wherein each lens of the plurality of lenses is positioned at a proximal end of a light-receiving light guide of the plurality of light-receiving light guides and integrally formed with the light-receiving light guide.
11. The optical measurement system of claim 1 , wherein:
the wearable module further comprises a light guide block housed within the housing and comprising a plurality of chambers,
each light-receiving light guide is disposed in a chamber included in the plurality of chambers, and
the plurality of chambers maintains the plurality of light-receiving light guides in optical alignment with the plurality of photodetectors.
12. The optical measurement system of claim 1 , wherein:
the wearable module further comprises a support assembly housed within the housing,
the plurality of photodetectors are disposed on the support assembly, and
the support assembly maintains the plurality of photodetectors in optical alignment with the plurality of light-receiving light guides.
13. The optical measurement system of claim 1 , wherein a distance of an optical path from each photodetector included in the plurality of photodetectors to a distal end of a corresponding light-receiving light guide optically aligned with the photodetector is less than 50 millimeters.
14. The optical measurement system of claim 1 , further comprising a spring member configured to bias the distal end portion of each light-receiving light guide away from the external surface of the housing.
15. The optical measurement system of claim 1 , wherein each light-receiving light guide is movable along an optical axis of the light-receiving light guide.
16. The optical measurement system of claim 1 , wherein each light-receiving light guide is configured to be pressed toward the external surface of the housing by the body of the user when the wearable module is worn by the user.
17. The optical measurement system of claim 1 , wherein:
the light source comprises:
a first light source configured to emit a first light pulse in a first wavelength;
a second light source configured to emit a second light pulse in a second wavelength that is different from the first wavelength;
the light-emitting light guide is configured to convey the first light pulse and the second light pulse toward the target; and
the optical measurement system further comprises an optical member housed within the housing and configured to receive the first light pulse from the first light source and the second light pulse from the second light source and direct the first light pulse and the second light pulse to the light-emitting light guide,
wherein the light pulse comprises one of the first light pulse and the second light pulse.
18. The optical measurement system of claim 17 , further comprising a controller configured to control one or more of the first light source or the second light source to output the light pulse.
19. The optical measurement system of claim 18 , wherein the controller is housed within the housing.
20. The optical measurement system of claim 17 , wherein the first light source and the second light source each comprises a laser diode.
21. The optical measurement system of claim 17 , wherein the optical member comprises one or more of a prism, a mirror, or another light guide.
22. The optical measurement system of claim 17 , wherein:
the optical member is configured to direct the first light pulse and the second light pulse to a proximal end of the light-emitting light guide, and
the light-emitting light guide is configured to emit the first light pulse and the second light pulse from a distal end of the light-emitting light guide toward the target.
23. A wearable module for use in an optical measurement system for time-domain near-infrared spectroscopy (TD-NIRS), the wearable module comprising:
a housing having an external surface that faces a body of a user when the wearable module is worn by the user;
a light source housed within the housing and configured to emit a light pulse;
an elongate light-emitting light guide configured to convey the light pulse toward a target within the body of the user, the light-emitting light guide having a proximal end portion housed within the housing and a distal end portion protruding from the external surface of the housing;
a plurality of time-resolved single-photon photodetectors housed within the housing and configured to detect photons from the light pulse after the light pulse is scattered by the target; and
a plurality of elongate light-receiving light guides positioned equidistant from the light-emitting light guide and configured to receive the photons from the target and convey the photons toward the plurality of photodetectors, each light-receiving light guide having a proximal end portion housed within the housing and a distal end portion protruding from the external surface of the housing.
24. The wearable module of claim 23 , further comprising at least one time-to-digital converter (TDC),
wherein the at least one TDC is configured to measure a time difference between an occurrence of the light pulse and an occurrence of an output pulse generated by a photodetector included in the plurality of photodetectors, the output pulse indicating that the photodetector has detected a photon.
25. The wearable module of claim 23 , further comprising a signal processing circuit configured to:
determine a temporal distribution of the photons detected by the plurality of photodetectors, and
generate a histogram based on the temporal distribution of the photons.
26. The wearable module of claim 23 , wherein each photodetector included in the plurality of photodetectors comprises a plurality of single-photon avalanche diode (SPAD) circuits.