Laser Physiological Sensing Module With Time-Gated Side-Light Rejection

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Solution Overview

Problem

Medical and wearable devices using optical emitters and detectors face limitations in measuring physiological information beyond 1-2 mm from the skin due to light scattering and side light saturation, restricting their form factor compatibility and operational range.

Innovation Solution

The use of laser emitters and detectors in a chip-scale module with passive optical components and side light blocking mechanisms allows for the extraction of physiological information from greater distances, enabling more versatile form factors and improved signal detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If optical detectors are moved away from the skin to enable greater measurement distance, then the operational range is improved, but side light saturation occurs causing measurement precision to deteriorate

Engineering Contradiction:

Improvemeasurement distanceVSAvoidsignal detection accuracy

Core Design Contradiction:

Length of stationary objectVSMeasurement precision

Solution Approach 1:

A time gate is introduced as an intermediary mechanism between the optical detector and the incoming light signals. The time gate selectively accepts photons within a specific time window that corresponds to the expected arrival time of reflected light from the skin, while rejecting photons arriving outside this window (side light). This temporal filtering enables the detector to operate at greater distances without saturation from side light.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system employs periodic pulsed illumination rather than continuous light emission. By emitting light in controlled pulses and using a time gate synchronized to these pulses, the system creates periodic measurement windows. This periodic action allows the detector to distinguish between valid reflected signals (arriving within the expected time window after each pulse) and side light (arriving at different times), thereby maintaining measurement precision at greater distances.

Inventive Principle:

Principle #19Periodic action

2Device complexity

If light emitting diodes are used as optical emitters, then device complexity is reduced, but the operational range is limited to 1-2 mm from the skin

Engineering Contradiction:

Improveemitter structure simplicityVSAvoidmeasurement distance

Core Design Contradiction:

Device complexityVSLength of stationary object

Solution Approach 1:

The patent changes the temporal parameters of light emission by using pulsed illumination instead of continuous emission. This parameter change allows the system to achieve greater measurement distances because the pulsed nature enables time-gated detection, which separates the desired reflected signal from side light based on arrival time. The LED structure itself remains simple, but its operational mode is transformed to achieve extended range.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If optical emitters and detectors are physically separated to prevent side light saturation, then measurement precision is improved, but device area increases

Engineering Contradiction:

Improvesignal detection accuracyVSAvoidmodule surface area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

A time gate serves as an intermediary that eliminates the need for large physical separation between emitter and detector. Instead of using spatial separation to prevent side light saturation, the time gate provides temporal separation, allowing the emitter and detector to be positioned close together while still achieving precise measurements by filtering signals based on their arrival time.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transitions from solving the side light problem in the spatial dimension (physical separation) to solving it in the temporal dimension (time-gated detection). By adding the time dimension as a filtering mechanism, the system achieves measurement precision without requiring large spatial separation, thereby reducing the module's surface area.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution enables the extraction of physiological data from up to 7 mm away, facilitating the use of devices in various form factors like glasses, watches, and jewelry while minimizing module size and preventing side light saturation, allowing for accurate measurement of heart rate, blood alcohol content, and other parameters.

Implementation Method 1

laser emitters...optical detector is provided to detect a change in optical power absorption

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

A lenslet collimates and directs the light beams from the one or more laser emitters at one or more different angles

Methodology Applied

Scientific EffectLight collimation and refraction: Lens

Implementation Method 3

optical detector is provided to detect a change in optical power absorption

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Data Source

PatentUS11883167B2Device to extract physiological information and method therefor

Publication Date: 2024.01.30 SCHIE DAVID

AI summary

A device to extract physiological information has at least one laser emitter. At least one optical detector is used to detect a change in optical power absorption. The laser emitter and optical detector are wire bonded into a chip scale module.