High density optical measurement systems with minimal number of light sources

1. An optical measurement system comprising:

a wearable assembly configured to be worn by a user and comprising a plurality of modules each configured to fit within a different slot of a plurality of slots of the wearable assembly, the plurality of slots each surrounded by a wall, the plurality of modules including a first module that comprises:

a first light source and a second light source each configured to emit light directed at a target, and

a first set of detectors configured to detect arrival times for photons of the light emitted by the first and second light sources after the light emitted by the first and second light sources is scattered by the target;

wherein

the first light source is configured to emit light having a first wavelength,

the second light source is configured to emit light having a second wavelength different than the first wavelength,

a ratio of a total number of the detectors of the first module to a total number of the light sources of the first module is at least two to one,

the walls that surround the plurality of slots physically separate the first module from a second module included in the plurality of modules, and

a positioning of the first and second modules in the slots of the wearable assembly is configured to cause one or more detectors of the first set of detectors to also detect arrival times for photons of light emitted by a third light source included in the second module.

2. The optical measurement system of claim 1 , wherein the second module further comprises:

a fourth light source configured to emit light directed at the target, and

a second set of detectors configured to detect arrival times for photons of the light emitted by the third and fourth light sources after the light emitted by the third and fourth light sources is scattered by the target.

3. The optical measurement system of claim 2 , wherein:

the third light source is configured to emit light having the first wavelength; and

the fourth light source is configured to emit light having the second wavelength.

4. The optical measurement system of claim 2 , wherein the first and second modules are configured to be removably attached to the wearable assembly.

5. The optical measurement system of claim 2 , wherein:

the positioning of the first and second modules within the wearable assembly causes one or more detectors included in the second set of detectors to detect arrival times for the photons of the light emitted by the first light source.

6. The optical measurement system of claim 1 , wherein the first set of detectors includes at least two detectors.

7. The optical measurement system of claim 1 , wherein:

the first light source is located at a center region of a surface of the first module; and

detectors included in the first set of detectors are distributed around the first light source on the surface of the first module.

8. The optical measurement system of claim 7 , wherein the detectors included in the first set of detectors are all equidistant from the first light source.

9. The optical measurement system of claim 1 , wherein the first light source is located away from a center region of a surface of the first module.

10. The optical measurement system of claim 1 , further comprising a processing unit configured to perform an operation based on the detected arrival times.

11. The optical measurement system of claim 10 , wherein the performing of the operation comprises generating at least one histogram based on the detected arrival times.

12. The optical measurement system of claim 10 , wherein the processing unit is included in the wearable assembly.

13. The optical measurement system of claim 10 , wherein the processing unit is not included in the wearable assembly.

14. The optical measurement system of claim 1 , wherein each detector in the first set of detectors comprises:

a photodetector configured to generate a photodetector output pulse in response to detecting a photon of the light; and

a time-to-digital converter configured to record a timestamp symbol in response to an occurrence of the photodetector output pulse, the timestamp symbol representative of an arrival time for the photon.