Self-Mixing Interferometry Sensor Contamination Detection

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Solution Overview

Problem

Existing particulate matter sensors face inaccuracies in particle velocity and concentration estimation due to contamination and obstructions, which can lead to false detection and significant errors in air quality monitoring.

Innovation Solution

A portable electronic device equipped with a self-mixing interferometry sensor that emits coherent light, detects reflections or backscatters, and uses a processor to determine particle velocity and concentration, while also operating in an absolute distance mode to identify and account for contamination and obstructions within the sensing volume, ensuring accurate data by discarding or re-determining measurements when obstructions are present.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If self-mixing interferometry is used to measure particle velocity and concentration, then measurement capability is provided, but contamination and obstructions cause inaccurate measurements

Engineering Contradiction:

Improveparticle velocity and concentration measurement accuracyVSAvoidmeasurement reliability under contamination and obstruction conditions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system performs preliminary actions by measuring absolute distance and detecting contamination/obstruction before attempting to measure particle velocity and concentration. This preliminary detection prevents inaccurate measurements from being recorded, resolving the contradiction by ensuring measurement reliability is established before precision measurements are taken.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously monitoring absolute distance measurements and using this information to determine whether contamination or obstructions are present. This feedback loop allows the system to adjust its measurement process by discarding or re-determining measurements when obstructions are detected, thereby maintaining both measurement precision and reliability.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If absolute distance measurement is performed to detect contamination and obstructions, then measurement accuracy is improved, but additional measurement steps increase time consumption

Engineering Contradiction:

Improvecontamination and obstruction detection accuracyVSAvoidtime for multiple measurement steps

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system merges multiple measurement functions into a unified process by using the self-mixing interferometry sensor to simultaneously perform absolute distance measurement, contamination detection, obstruction detection, and particle velocity/concentration measurement. This combination reduces the overall time required compared to using separate sensors or methods for each function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system applies partial action by selectively performing additional measurement steps only when necessary. Absolute distance measurement and contamination/obstruction detection are performed as needed to validate particle measurements, rather than continuously, thereby reducing time loss while maintaining measurement precision when required.

Inventive Principle:

Principle #16Partial or excessive action

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 approach prevents the reporting of inaccurate particle velocity and concentration data by identifying and addressing contamination and obstructions, ensuring reliable air quality monitoring and measurement accuracy.

Implementation Method 1

a self-mixing interferometry sensor configured to emit a beam of coherent light from an optical resonant cavity, receive a reflection or backscatter of the beam into the optical resonant cavity, and produce a self-mixing signal resulting from self-mixing of the coherent light within the optical resonant cavity

Methodology Applied

Scientific EffectSelf-mixing interferometry: Interference

Implementation Method 2

emit a beam of coherent light from an optical resonant cavity, receive a reflection or backscatter of the beam into the optical resonant cavity

Methodology Applied

Scientific EffectOptical resonance: Resonance

Data Source

PatentUS11680788B2Handling obstructions and transmission element contamination for self-mixing particulate matter sensors

Publication Date: 2023.06.20 APPLE INC

AI summary

A portable electronic device is operable in a particulate matter concentration mode where the portable electronic device uses a self-mixing interferometry sensor to emit a beam of coherent light from an optical resonant cavity, receive a reflection or backscatter of the beam into the optical resonant cavity, produce a self-mixing signal resulting from a reflection or backscatter of the beam of coherent light, and determine a particle velocity and/or particulate matter concentration using the self-mixing signal. The portable electronic device is also operable in an absolute distance mode where the portable electronic device determines whether or not an absolute distance determined using the self-mixing signal is outside or within a particulate sensing volume associated with the beam of coherent light. If not, the portable electronic device may determine a contamination and/or obstruction is present that may result in inaccurate particle velocity and/or particulate matter concentration determination.