Maintaining consistent photodetector sensitivity in an optical measurement system

Patent metadata

Field	Value
Publication number	US-12059262-B2
Application number	US-202117202657-A
Country	US
Kind code	B2
Filing date	Mar 16, 2021
Priority date	Mar 20, 2020
Publication date	Aug 13, 2024
Grant date	Aug 13, 2024

Abstract

An illustrative optical measurement system includes a light source configured to emit light directed at a target. The optical measurement system further includes a photodetector configured to detect a photon of the light after the light is scattered by the target. The optical measurement system further includes a control circuit configured to arm the photodetector by applying a bias voltage to a first terminal of the photodetector and applying, for a predetermined amount of time using a current source, a current to a second terminal of the photodetector to produce a predetermined voltage difference across the photodetector.

First claim

What is claimed is:

1. An optical measurement system comprising:
a light source configured to emit light directed at a target;
a photodetector configured to detect a photon of the light after the light is scattered by the target; and
a control circuit configured to arm the photodetector by:
applying a bias voltage to a first terminal of the photodetector; and
applying, for a predetermined amount of time using a current source, a current to a second terminal of the photodetector for the predetermined amount of time to produce a predetermined voltage difference different from the bias voltage and higher than a breakdown voltage of the photodetector across the photodetector.

2. The optical measurement system of claim 1 , wherein the control circuit comprises a current mirror coupling the current source to the second terminal of the photodetector.

3. The optical measurement system of claim 2 , wherein:
the first terminal comprises a cathode of the photodetector;
the second terminal comprises an anode of the photodetector; and
the applying the current comprises discharging the anode of the photodetector to produce the predetermined voltage difference across the photodetector.

4. The optical measurement system of claim 2 , wherein:
the first terminal comprises an anode of the photodetector;
the second terminal comprises a cathode of the photodetector; and
the applying the current comprises delivering charge to the cathode of the photodetector to produce the predetermined voltage difference across the photodetector.

5. The optical measurement system of claim 1 , further comprising an array of photodetectors including the photodetector;
wherein the control circuit is configured to arm the array of photodetectors by:
applying the bias voltage to first terminals of the array of photodetectors; and
applying the current using the current source to second terminals of the array of photodetectors.

6. The optical measurement system of claim 5 , wherein the current source is a shared current source configured to apply the current to the second terminals.

7. The optical measurement system of claim 6 , further comprising a plurality of current minors coupling the shared current source to the second terminals of the array of photodetectors.

8. The optical measurement system of claim 7 , wherein the plurality of current mirrors comprise a shared transistor and a plurality of local transistors each corresponding to a different photodetector of the array of photodetectors.

9. The optical measurement system of claim 1 , wherein the photodetector comprises:
a single photon avalanche diode (SPAD); and
a fast gating circuit configured to arm and disarm the SPAD.

10. The optical measurement system of claim 1 , wherein the photodetector is included in a wearable device configured to be worn by a user.

11. The optical measurement system of claim 10 , wherein the wearable device includes a head-mountable component configured to be worn on a head of a user.

12. A wearable system for use by a user comprising:
a head-mountable component configured to be attached to a head of the user, the head-mountable component comprising a photodetector configured to detect photons from a light pulse after the light pulse reflects off a target within the head; and
a control circuit configured to arm the photodetector by:
applying a bias voltage to a first terminal of the photodetector; and
applying, for a predetermined amount of time using a current source, a current to a second terminal of the photodetector for the predetermined amount of time to produce a predetermined voltage difference different from the bias voltage and higher than a breakdown voltage of the photodetector across the photodetector.

13. The wearable system of claim 12 , wherein the control circuit comprises a current mirror coupling the current source to the second terminal of the photodetector.

14. The wearable system of claim 13 , wherein:
the first terminal comprises a cathode of the photodetector;
the second terminal comprises an anode of the photodetector; and
the applying the current comprises discharging the anode of the photodetector to produce the predetermined voltage difference across the photodetector.

15. The wearable system of claim 13 , wherein:
the first terminal comprises an anode of the photodetector;
the second terminal comprises a cathode of the photodetector; and
the applying the current comprises delivering charge to the cathode of the photodetector to produce the predetermined voltage difference across the photodetector.

16. The wearable system of claim 12 , further comprising an array of photodetectors including the photodetector;
wherein the control circuit is configured to arm the array of photodetectors by:
applying the bias voltage to first terminals of the array of photodetectors; and
applying the current using the current source to second terminals of the array of photodetectors.

17. The wearable system of claim 16 , wherein the current source is a shared current source configured to apply the current to the second terminals.

18. The wearable system of claim 17 , further comprising a plurality of current mirrors coupling the shared current source to the second terminals of the array of photodetectors.

19. The wearable system of claim 18 , wherein the plurality of current minors comprise a shared transistor and a plurality of local transistors each corresponding to a different photodetector of the array of photodetectors.

20. The wearable system of claim 12 , wherein the photodetector comprises:
a single photon avalanche diode (SPAD); and
a fast gating circuit configured to arm and disarm the SPAD.

Assignees

• Hi Llc

Inventors

• Field Ryan
• Do Valle Bruno

Classifications

• A61B5/0075

  by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy (A61B5/0071 takes precedence) · CPC title

• A61B5/0073

  by tomography, i.e. reconstruction of 3D images from 2D projections (A61B5/0066 takes precedence) · CPC title

• A61B5/6803

  Head-worn items, e.g. helmets, masks, headphones or goggles · CPC title

• G06F3/015

  Input arrangements based on nervous system activity detection, e.g. brain waves [EEG] detection, electromyograms [EMG] detection, electrodermal response detection · CPC title

• A61B2562/046

  in a matrix array · CPC title