Scattered Light Measurement with Incident Angle Limiting for Motion Noise
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Solution Overview
Problem
Existing laser Doppler blood flow meters are susceptible to noise due to changes in relative velocity and position between the sensor and the observation target, caused by body motion, which affects measurement accuracy.
Innovation Solution
A scattered light signal measurement apparatus that utilizes a laser Doppler phenomenon to measure particle velocity and flow rate while minimizing noise by stabilizing the sensor relative to the observation target, using techniques such as low-pass filtering and acceleration sensing to correct for body motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser Doppler blood flow meter is used to measure blood flow velocity, then it is possible to measure the velocity of particles in blood by detecting scattered light, but body motion causes position shift or relative velocity between the living body and the sensor, generating noise in the measurement result
Solution Approach 1:
The patent introduces a reference light path that serves as an intermediary to measure the Doppler shift caused by body motion separately. This reference path does not interact with the blood flow but captures the motion-induced Doppler shift, which then serves as a basis for correcting the measurement signal from the blood flow path.
Solution Approach 2:
The system uses the Doppler shift measured from the reference light path as feedback to correct the measurement signal. The control unit calculates the body motion component from the reference signal and subtracts it from the blood flow measurement signal, creating a closed-loop correction mechanism that continuously compensates for motion artifacts.
2Ease of operation
If the sensor is made portable for ease of operation, then it can be attached to the living body, but body motion causes changes in relative velocity and position that affect measurement accuracy
Solution Approach 1:
The reference light path acts as an intermediary measurement channel that specifically isolates and measures the body motion component. This allows the portable sensor to maintain ease of operation while the reference path provides the necessary motion data for correction, enabling accurate measurements despite the sensor's mobility.
Solution Approach 2:
The patent extracts the body motion component from the overall measurement signal by using a separate reference light path. This extracted motion component is then removed from the blood flow measurement signal, allowing the portable sensor to function accurately despite motion artifacts that would otherwise contaminate the measurement.
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 accurate measurement of particle velocity and flow rate by reducing noise from body motion, ensuring precise results in blood flow velocity measurements.
Implementation Method 1
Scattering by particles such as red blood cells that move in a blood flow causes a shift (Doppler shift) of a wavelength due to the Doppler effect as compared to scattering by other tissues that do not move.
Implementation Method 2
The laser light is scattered by biological tissues. Scattering by particles such as red blood cells that move in a blood flow causes a shift (Doppler shift) of a wavelength
Implementation Method 3
an incident angle limiting unit configured to limit the incident angle of scattered light incident on a single point of the light receiving element
Data Source
Figure 1(a)~1(c)
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AI summary
An apparatus is provided. The apparatus includes a coherent light source configured to emit coherent light to a part of a body containing scatterers. Further, the apparatus includes an irradiation light control unit including a plurality of lenses and configured to magnify and collimate the coherent light from the coherent light source. The apparatus additionally includes a light receiving element and an incident angle limiting unit including at least one lens and configured to limit an incident angle of scattered light. The scattered light is light scattered by the scatterers.