Tunable Optoelectronic Blood Pressure Sensor
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Solution Overview
Problem
Photoplethysmography-based sensors face challenges in accurately determining blood pressure due to low resolution with respect to vascular tissue depth and noise artifacts from user movements, limiting their application beyond pulse oximeters.
Innovation Solution
A tunable optoelectronic device comprising an array of avalanche photodiodes and a tunable optical filter, coupled with a microcontroller and processor, allows for flexible selection of wavelengths and improved signal processing to enhance blood pressure estimation by distinguishing arterial from venous signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single wavelength light source is used, then the device complexity is reduced, but the depth resolution and ability to distinguish different vascular layers is insufficient
Solution Approach 1:
The patent implements a tunable optical filter that can dynamically adjust the wavelength of light in real-time, allowing the system to switch between different wavelengths as needed. This dynamic capability enables depth-resolved measurements without requiring multiple fixed wavelength sources, thus improving measurement precision while keeping device complexity manageable
Solution Approach 2:
The system changes the wavelength parameter of the light source to probe different depths of vascular tissue. By varying the wavelength, the system can selectively target superficial versus deeper vascular layers, achieving depth resolution through parameter modulation rather than through complex multi-source architecture
2Measurement precision
If multiple photodetectors spaced apart are used, then depth resolution is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent segments the measurement process in the spectral domain rather than using spatially separated detectors. By dividing the spectrum into different wavelength bands and measuring absorption at each band, the system achieves depth-resolved information from a single photodetector position, avoiding the complexity of multiple detectors
Solution Approach 2:
Instead of resolving depth through spatial separation (one dimension), the patent transitions to resolving depth through wavelength separation (another dimension). This dimensional transformation allows a single photodetector to capture depth information by analyzing spectral characteristics of light absorption at different wavelengths
3Reliability
If conventional photodetectors are used, then the device is cost-effective, but noise artifacts from user movements significantly degrade signal quality
Solution Approach 1:
The system uses feedback mechanisms where the detected signal quality informs adjustments in measurement parameters. By monitoring the strength and quality of returned signals at different wavelengths, the system can adaptively select optimal wavelengths that provide stronger arterial signals relative to noise, thereby improving signal quality and reducing the impact of motion artifacts
Solution Approach 2:
The patent applies local quality by selecting specific wavelengths that are optimally sensitive to arterial blood absorption characteristics. Rather than using a broad spectrum uniformly, the system identifies and focuses on wavelength regions where arterial signals are strongest, thereby improving signal-to-noise ratio locally in the spectral domain
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
The solution provides precise blood pressure estimation by improving depth resolution and reducing noise, enabling more accurate determination of systolic blood pressure and increasing the flexibility of the system for optimal wavelength selection.
Implementation Method 1
an array of avalanche photodiodes... configured to receive a light beam reflected from a vascularized tissue
Implementation Method 2
a tunable optical filter... configured to receive a light beam reflected from a vascularized tissue
Implementation Method 3
the variations in light intensity detected by the photodetector are a function of the changes in volume affecting all the blood vessels through which the light passes
Data Source
AI summary
In various embodiments, the present disclosure provides devices and systems for detecting the blood pressure of a user. In one embodiment, an optoelectronic device includes an array of avalanche photodiodes operating in Geiger mode. A tunable optical filter is optically coupled to the array and receives a light beam reflected from a vascularized tissue of the user, in response to the vascularized tissue being illuminated by an optical source.