Polarized PPG Biosensors for Scattering Noise Reduction
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Solution Overview
Problem
Existing optical biosensors face challenges such as optical noise, scattering/reflection, sensor location variability, skin tone differences, motion artifacts, and low perfusion, which affect the accuracy and reliability of physiological parameter measurements.
Innovation Solution
A compact PPG sensor system utilizing on-chip polarization and multispectral sensor characteristics, incorporating a polarization controlled light source and detector with passive or active polarization optics, enabling simultaneous measurement of multiple polarization states and spectral information to improve signal-to-background ratio and angle-dependent field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical biosensors are used without polarization control, then the device structure is simple, but optical noise and scattering/reflection affect measurement accuracy
Solution Approach 1:
The patent introduces polarization optics (polarizers, wave plates) as intermediary components between the light source and detector. These intermediaries manipulate the polarization state of light to selectively transmit desired signals while blocking scattered light and reflections, thereby improving measurement accuracy without requiring fundamental changes to the sensor architecture
Solution Approach 2:
The patent changes the polarization parameter of the light beam by incorporating wave plates that rotate or modify polarization states. This parameter change allows the system to distinguish between different light paths (direct vs. scattered) based on their polarization characteristics, enhancing measurement precision while maintaining a relatively simple device structure
2Reliability
If polarization optics are added to improve signal-to-background ratio, then measurement reliability improves, but device complexity increases
Solution Approach 1:
The patent designs the polarization optics system to serve multiple functions simultaneously: wave plates both rotate polarization for signal enhancement and act as reference elements for calibration, while polarizers simultaneously reject scattered light and define the detection geometry. This multi-functionality improves measurement reliability without proportionally increasing device complexity
3Measurement precision
If on-chip polarization filters are used to remove direct reflection, then biosignal measurement accuracy improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent designs the on-chip polarization filters with symmetric integration around the light path, creating an equipotential optical configuration where misalignment errors in opposite directions cancel each other out. This symmetric design reduces the impact of manufacturing precision variations on the overall system performance while maintaining the ability to remove direct reflections
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
Enhances the accuracy and reliability of physiological parameter measurements by reducing angle-dependency and background noise, allowing for precise detection of polarization-sensitive targets and molecules, including cardiovascular and respiratory information.
Implementation Method 1
a polarization optical element configured to polarize the electromagnetic spectral emission
Implementation Method 2
a collimation optical element configured to focus or collimate the electromagnetic spectral emission into a narrow or tight beam to reduce diffusion
Implementation Method 3
a diffractive optical element configured to separate the electromagnetic spectral emission into a predetermined arrangement
Data Source
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AI summary
An electronic device including a light source and a detector are provided. The light source includes an electromagnetic spectral emission source configured to output an electromagnetic spectral emission, a polarization optical element configured to polarize the electromagnetic spectral emission, a collimation optical element configured to focus or collimate the electromagnetic spectral emission into narrow or tight beam to reduce diffusion, and a diffractive optical element configured to separate the electromagnetic spectral emission into a predetermined arrangement.