Phase-Based Displacement Detection for Minute Motion Sensing

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Solution Overview

Problem

Existing methods for detecting minute displacements, such as heartbeat or breaths, face challenges in accuracy due to noise interference and resolution limits, especially when using ultrasonic waves.

Innovation Solution

A displacement detection device utilizing a thermophone to transmit and receive chirp waves, which calculates phase differences between successive frames to accurately detect minute displacements by analyzing the phase information of the received signals, rather than relying solely on envelope analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If ultrasonic high-frequency signals are transmitted and phase difference tracking method is used, then minute displacement detection capability is improved, but measurement precision deteriorates due to noise interference and resolution limits

Engineering Contradiction:

Improveminute displacement detection capabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the detection parameter from envelope amplitude to phase information of the received signal. By extracting phase differences between transmitted and received chirp signals, the system achieves higher measurement precision for minute displacements while maintaining reliability through correlation-based phase extraction that is less susceptible to noise interference.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional envelope detection method with a signal processing approach using correlation analysis and phase extraction. This substitution of detection mechanism allows for more accurate phase difference measurement, thereby improving measurement precision without being as vulnerable to noise and resolution limits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If envelope analysis method is used for displacement detection, then device complexity is reduced, but measurement precision deteriorates due to noise and air current interference

Engineering Contradiction:

Improvedetection method simplicityVSAvoiddisplacement detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from envelope amplitude to phase information. By using correlation analysis to extract phase differences between transmitted and received signals, the system achieves higher measurement precision while the overall device complexity remains manageable through efficient signal processing algorithms.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces correlation analysis as an intermediary processing step between signal reception and displacement calculation. This intermediary operation extracts phase information in a noise-resistant manner, improving measurement precision without requiring complex additional hardware.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables precise detection of minute displacements without physical contact, reducing errors from noise and air current interference, and improving resolution beyond conventional methods.

Implementation Method 1

transmitter transmits to an object, a modulated wave including a plurality of frequencies

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 2

receiver receives a reflection wave from the object

Methodology Applied

Scientific EffectAcoustic reflection: Reflection

Implementation Method 3

receiver receives a reflection wave from the object and generates a reception signal indicating a reception result

Methodology Applied

Scientific EffectAcoustic-to-electrical energy conversion:

Implementation Method 4

extract, based on the first transmission signal and the first reception signal, first phase information indicating a phase defined in a correlation between the first transmission signal and the first reception signal

Methodology Applied

Scientific EffectPhase difference measurement:

Implementation Method 5

detect a displacement of the object between the first and second measurement periods, depending on a difference between the first phase information and the second phase information

Methodology Applied

Scientific EffectTime delay measurement: Time of Flight

Data Source

PatentUS12585013B2Displacement detection device and method

Publication Date: 2026.03.24 MURATA MFG CO LTD

AI summary

A displacement detection device includes a transmitter, a receiver, and a controller configured or programmed to output a first transmission signal to the transmitter to transmit a modulated wave and acquire a responsive first reception signal in a first measurement period, extract first phase information indicating a phase defined in a correlation between a first transmission signal and a reception signal, output a second transmission signal to the transmitter and acquire a responsive second reception signal in a second measurement period after the first measurement period, extract second phase information indicating a phase defined in a correlation between the second transmission signal and reception signal, and detect a displacement of an object between the first and second measurement periods, depending on a difference between the first and second phase information.