Wearable brain interface system comprising a head-mountable component and a control system
An exemplary wearable brain interface system includes a head-mountable component and a control system. The head-mountable component includes an array of photodetectors that includes a photodetector comprising a single-photon avalanche diode (SPAD) and a fast-gating circuit configured to arm and disarm the SPAD. The control system is for controlling a current drawn by the array of photodetectors.
1. A wearable brain interface system comprising:
a head-mountable component comprising an array of photodetectors that includes a photodetector comprising:
a single-photon avalanche diode (SPAD), and
a fast-gating circuit configured to arm and disarm the SPAD; and
a control system for controlling a current drawn by the array of photodetectors.
2. The wearable brain interface system of claim 1 , wherein the control system comprises a plurality of switches connected in parallel to an anode or a cathode of the SPAD.
3. The wearable brain interface system of claim 2 , wherein:
the fast-gating circuit comprises a gating transistor gated by a gating voltage, and
each switch of the plurality of switches is connected to a respective additional transistor gated by the gating voltage.
4. The wearable brain interface system of claim 2 , wherein the control system is configured to control the current drawn by controlling the plurality of switches to control a slew rate of the fast-gating circuit.
5. The wearable brain interface system of claim 2 , wherein the control system further comprises a quenching transistor connected in parallel with the plurality of switches, the quenching transistor configured to control an avalanche current drawn by the SPAD.
6. The wearable brain interface system of claim 1 , wherein
the control system comprises a plurality of switches connected in parallel between an anode or a cathode of the SPAD and a transistor configured to control a disarming of the SPAD; and
the control system is configured to control the current drawn by controlling the plurality of switches to control a slew rate of the fast-gating circuit.
7. The wearable brain interface system of claim 1 , wherein
the control system comprises a plurality of voltage sources configured to gate a gating transistor of the fast-gating circuit;
the array of photodetectors comprises:
a first subset of photodetectors including the photodetector, each photodetector of the first subset of photodetectors connected to a first voltage source of the plurality of voltage sources, and
a second subset of photodetectors, each photodetector of the second subset of photodetectors connected to a second voltage source of the plurality of voltage sources; and
the control system is configured control the current drawn by controlling the plurality of voltage sources to selectively arm the first subset of photodetectors and the second subset of photodetectors.
8. The wearable brain interface system of claim 7 , wherein the first and second subsets of photodetectors are determined based on a characteristic of the photodetectors.
9. The wearable brain interface system of claim 8 , wherein the characteristic of the photodetectors includes a dark count, and the determining of the subsets of photodetectors includes grouping photodetectors with a larger dark count rate in the first subset of photodetectors and photodetectors with a smaller dark count rate in the second subset of photodetectors.
10. The wearable brain interface system of claim 7 , wherein:
the array of photodetectors is configured to measure a light pulse response of a target; and
the subsets of photodetectors are determined based on a characteristic of the light pulse response.
11. The wearable brain interface system of claim 1 , wherein the control system is configured to control the current drawn by abstaining from disarming the SPAD during one or more measurement time periods.
12. The wearable brain interface system of claim 11 , wherein:
the control system includes a combinational logic gate coupled to a transistor of the fast-gating circuit configured to disarm the SPAD; and
the control system is configured to abstain from disarming the SPAD by providing a signal to the array of photodetectors configured to keep open the transistor of the fast-gating circuit configured to disarm the SPAD.
13. The wearable brain interface system of claim 1 , wherein:
the control system comprises a timer coupled to the fast-gating circuit, the timer configured to disarm the SPAD subsequent to the SPAD detecting a photon until a particular point in time relative to a light pulse; and
the control system is configured to control the current drawn by controlling the timer.
14. The wearable brain interface system of claim 13 , wherein the timer is configured to disarm the SPAD by setting a voltage across the SPAD to a value smaller than a breakdown voltage of the SPAD.
15. The wearable brain interface system of claim 13 , wherein the particular point in time is a time after a light pulse subsequent to the SPAD detecting the photon.
16. The wearable brain interface system of claim 1 , wherein:
the control system comprises a plurality of switches connected in parallel to an anode or a cathode of the SPAD;
the control system is configured to control the current drawn by at least one of:
controlling the plurality of switches to control a slew rate of the fast-gating circuit, and
abstaining from disarming the SPAD during one or more measurement time periods.
17. The wearable brain interface system of claim 1 , wherein the control system is included in the head-mountable component.
18. The wearable brain interface system of claim 1 , wherein the control system is included in a housing separate from the head-mountable component.
19. A wearable brain interface system comprising:
a head-mountable component comprising an array of photodetectors that includes a photodetector comprising:
a single photon avalanche diode (SPAD), and
a fast-gating circuit configured to arm and disarm the SPAD; and
a control system comprising a plurality of switches connected in parallel to the SPAD, the control system configured to control a current drawn by the array of photodetectors by controlling the plurality of switches to control a slew rate of the fast-gating circuit.
20. A wearable brain interface system comprising:
a head-mountable component comprising an array of photodetectors that includes a photodetector comprising:
a single photon avalanche diode (SPAD), and
a fast-gating circuit configured to arm and disarm the SPAD; and
a control system configured to control a current drawn by the array of photodetectors by abstaining from disarming the SPAD during one or more measurement time periods.