Abstract: An optical measurement system includes a detector configured to detect signal photons included in a light pulse after the signal photons enter a body of a user and are scattered by a target within the body and reference photons included in the light pulse, the reference photons being diverted to the detector without entering the body. The optical measurement system further includes a processing unit configured to determine a temporal distribution of the signal photons detected by the detector, determine a temporal distribution of the reference photons detected by the detector, and generate measurement data based on the temporal distribution of the signal photons and the temporal distribution of the reference photons.

Abstract: An illustrative optical measurement system may include a module comprising a light source configured to emit light directed at a target, a plurality of detectors configured to detect target photon arrival times of target photons of the light after the light is scattered by the target, a reference detector configured to detect reference photon arrival times of reference photons of the light after the light is reflected within the module, and a waveguide configured to direct the light reflected within the module through a plurality of channels of the waveguide to the reference detector. The system may further include a controller configured to determine, based on an output from the reference detector, an instrument response function (IRF) of the module.

Abstract: An illustrative optical measurement system may include a module comprising a light source configured to emit light directed at a target, a plurality of detectors configured to detect target photon arrival times of target photons of the light after the light is scattered by the target, and a reference detector configured to detect reference photon arrival times of reference photons of the light after the light is reflected within the module. The system may further include a controller configured to determine, based on an output from the reference detector, an instrument response function (IRF) of the module.

Abstract: An illustrative optical measurement system includes a light source configured to emit light directed at a target. The system further includes a detector configured to detect arrival times for photons of the light after the light is scattered by the target. The system further includes a temperature sensor configured to output a temperature signal representative of a temperature of the light source. The system further includes an optical sensor configured to output a power signal representative of an optical power level of the light emitted by the light source. The system further includes a driver circuit configured to output, based on the temperature signal and the power signal, an input current for the light source.

Abstract: An illustrative optical measurement device includes a light source configured to emit light pulses directed at a target of a user. The optical measurement device further includes a detector configured to detect arrival times for photons of the light pulses after the photons are scattered by the target. The optical measurement device further includes a processing unit configured to determine, while the optical measurement device is being worn by the user, an instrument response function (IRF) associated with the optical measurement device. The processing unit is further configured to generate, based on the arrival times of the photons at the detector, histogram data associated with the target. The processing unit is further configured to determine, based on the IRF and the histogram data, a property of the target.

Abstract: An illustrative optical measurement system includes a light source configured to emit a light pulse directed at a target. The optical measurement system further includes a plurality of photodetectors configured to operate in accordance with an input bias voltage. The optical measurement system further includes a control circuit configured to identify a photodetector subset included in the plurality of photodetectors and that detects, while the input bias voltage has a first value, photons of the light pulse after the light pulse is scattered by the target. The control circuit is further configured to determine, based on the identifying of the photodetector subset, an overvoltage associated with the photodetector subset. The control circuit is further configured to update, based on the overvoltage, the input bias voltage for the plurality of photodetectors to have a second value.

Abstract: An illustrative system may include a memory storing instructions and a processor communicatively coupled to the memory and configured to execute the instructions to: cause a signal to be applied to a component within an optical measurement system; generate, based on a response of the component to the signal, characterization data representative of a timing uncertainty associated with the component; and perform, based on the characterization data, an action associated with the component.

Abstract: An illustrative multimodal measurement system includes a wearable assembly configured to be worn by a user; and a module configured to be removably inserted into the wearable assembly and comprising: a housing, a printed circuit board (PCB) and a light guide assembly configured to emit light directed at a target within the user. The light guide assembly comprises: a lower light guide portion housed within the housing and having a proximal end attached to the PCB, a conductive spring member housed within the housing and comprising a coil positioned around an external surface of the lower light guide portion, and a conductive upper light guide portion connected to the lower light guide portion and configured to protrude from an upper surface of the housing and be in contact with a surface of a body of the user.

Abstract: An optical measurement system includes a light source configured to emit a first light pulse and a second light pulse toward a target, a detector, and a processing unit. The first light pulse has a first wavelength and the second light pulse has a second wavelength different from the first wavelength. The processing unit is configured to determine a plurality of temporal distributions of photons included in the first light pulse and the second light pulse and detected by the detector after the photons are scattered by the target, and determine, based on the plurality of temporal distributions and a source-detector distance estimation model, a distance between the light source and the detector.

Abstract: An illustrative optical measurement system includes a light source configured to emit light directed at a target, an array of photodetectors configured to detect photons of the light after the light is scattered by the target, and a processing unit configured to measure a noise level of a photodetector included in the array of photodetectors, the noise level comprising a dark count rate that measures a dark count divided by a time period, determine that the noise level meets a predetermined threshold comprising a dark count rate threshold, and prevent, based on the determining that the noise level meets the predetermined threshold, an output of the photodetector from being used in generating a histogram based on a temporal distribution of photons detected by the array of photodetectors, the preventing comprising switching the output to a monitoring circuit that monitors a characteristic of the optical measurement system separate from the photodetector.

Abstract: An illustrative system may include a TDC configured to monitor for an occurrence of a photodetector output pulse during a measurement time window that is within and shorter in duration than a light pulse time period, the photodetector output pulse generated by a photodetector when the photodetector detects a photon from a light pulse having a light pulse time period; a PLL circuit for the TDC and having a PLL feedback period defined by a reference clock, the PLL circuit configured to: output a plurality of fine phase signals and output one or more signals representative of a plurality of feedback divider states during the PLL feedback period; and a precision timing circuit configured to adjust, based on one or more of the fine phase signals and/or the feedback divider states, a temporal position of the measurement time window within the light pulse time period.

Abstract: An illustrative biopotential measurement system includes a plurality of electrodes each configured to record a different signal included in a plurality of signals representative of electrical activity of a target within a user; a plurality of non-inverting operational amplifier circuits each connected to a different electrode included in the plurality of electrodes and each configured to output a different amplified signal included in a plurality of amplified signals representative of amplified versions of the plurality of signals; and a common-mode feedback circuit configured to measure a common-mode signal between the plurality of amplified signals and provide the common-mode signal to the non-inverting operational amplifier circuits. The non-inverting operational amplifier circuits are configured to use the common-mode signal to generate voltage-divided feedback signals used to generate the plurality of amplified signals.

Abstract: An illustrative optical measurement system includes a signal generator configured to generate a signal and a processing unit configured to direct the signal generator to apply the signal to a TDC included in the optical measurement system and generate, based on timestamp symbols recorded by the TDC in response to the signal, characterization data representative of a nonlinearity of the TDC.

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 receive a first input voltage that is a temperature-dependent voltage. The control circuit is further configured to receive a second input voltage that is a temperature-invariant voltage. The control circuit is further configured to output, based on a combination of the first input voltage and the second input voltage, a bias voltage for the photodetector, wherein the combination of the first and second input voltages is configured to cause the bias voltage to vary based on temperature.

Abstract: An optical measurement system includes a detector configured to detect signal photons included in a light pulse after the signal photons enter a body of a user and are scattered by a target within the body and reference photons included in the light pulse, the reference photons being diverted to the detector without entering the body. The optical measurement system further includes a processing unit configured to determine a temporal distribution of the signal photons detected by the detector, determine a temporal distribution of the reference photons detected by the detector, and generate measurement data based on the temporal distribution of the signal photons and the temporal distribution of the reference photons.

Abstract: An exemplary optical measurement system described herein includes a control circuit configured to output a global bias voltage and a module communicatively coupled to the control circuit. The module includes a light source configured to emit light directed at a target. The module further includes a plurality of detectors configured to detect arrival times for photons of the light after the light is scattered by the target. The module further includes a module control circuit configured to receive the global bias voltage and output a plurality of detector bias voltages based on the global bias voltage. The plurality of detector bias voltages include a respective detector bias voltage for each detector of the plurality of detectors.

Abstract: An illustrative calibration member made from a material that scatters light may be used to perform a calibration operation with respect to an optical measurement device having a plurality of light sources and a plurality of detectors distributed among a plurality of modules. The calibration member may form an exterior surface configured to support the optical measurement device and scatter photons of light emitted by the optical measurement device. The calibration operation may be performed based on arrival times of the scattered photons detected by the optical measurement device.

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.

Abstract: A wearable module for use in an optical measurement system includes a housing and a plurality of light-receiving members. The housing includes a target-side surface configured to face a surface of a body of a user when the wearable module is worn by the user. The plurality of light-receiving members protrude from the target-side surface of the housing and are configured to receive photons scattered by a target within the body of the user and guide the received photons toward a photodetector. An extent to which each of the plurality of light-receiving members protrudes from the target-side surface is adjustable such that, when the wearable module is worn by the user, each of the plurality of light-receiving members is in physical contact with the surface of the body.

Abstract: A wearable module for use in an optical measurement system includes a light guide configured to receive a light pulse from a light source and guide signal photons included in the light pulse toward a target within a body of a user, and a light diverter configured to divert reference photons included in the light pulse toward at least one detector configured to detect the reference photons.