Reflective Optical Sensor Layout for Higher Blood Signal SNR
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Solution Overview
Problem
Reflective blood measurement techniques suffer from low signal-to-noise ratios (SNR) and alternating current (AC)/direct current (DC) ratios due to light components being reflected from non-perfused tissue layers and the organ surface, leading to poor optical signal quality.
Innovation Solution
The device employs a structured arrangement of light emitters and detectors with specific distances and angles to reflect light components from perfused tissue layers while minimizing reflections from non-perfused layers, enhancing SNR and AC/DC ratios by reducing direct current components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reflective measurement techniques are used to enable measurements on any body part with reduced energy consumption, then adaptability and energy efficiency are improved, but signal-to-noise ratio and AC/DC ratio deteriorate due to light reflection from non-perfused tissue layers and organ surface
Solution Approach 1:
The patent applies local quality by using multiple light sources with different wavelengths (red and infrared) at specific positions relative to the detector. Each wavelength penetrates tissue to different depths, with the red light primarily detecting superficial blood flow and infrared light detecting deeper blood flow. This spatial and spectral differentiation allows selective measurement of blood flow from specific tissue layers, improving signal quality by isolating perfused tissue signals from non-perfused surface reflections
Solution Approach 2:
The patent introduces a new dimension by measuring light absorption at multiple wavelengths rather than a single wavelength. The red light source (630-680 nm) and infrared light source (780-850 nm) provide depth-resolved blood flow information, with shorter wavelengths detecting superficial vessels and longer wavelengths detecting deeper vessels. This multi-wavelength approach transforms the measurement from a single-plane detection to a depth-resolved three-dimensional measurement, improving signal-to-noise ratio by separating blood flow signals from surface reflection noise
2Measurement precision
If light source power is increased to improve signal magnitude, then signal strength is improved, but noise components increase proportionally due to increased baseline DC component
Solution Approach 1:
The patent changes the parameter of light wavelength to differentiate between superficial and deep blood flow detection. By using red light (630-680 nm) for superficial detection and infrared light (780-850 nm) for deep detection, the system optimizes signal extraction from different tissue depths without increasing overall light power. This wavelength-based parameter differentiation allows selective enhancement of AC components from perfused tissue while minimizing DC components from non-perfused surface layers, improving signal-to-noise ratio without proportionally increasing noise
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 configuration significantly improves the SNR and AC/DC ratios of measured optical signals, allowing for accurate measurement of blood properties such as heart rate, oxygen saturation, and analyte concentrations by focusing on light components from perfused tissue layers.
Implementation Method 1
reflective measurement techniques use a light source and a light detector which are on the same side of a tissue
Implementation Method 2
optical measurement of blood properties... employing reflective measurement techniques... light detection of the light wave signals reflected from (capillary) blood vessels
Data Source
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Figure 3a
AI summary
A device, a substrate including a connection port. The substrate includes traces to enable a circuit of the substrate. The circuit is connected to the connection port. A light sensor mechanically and electrically attached respectfully to a first planar surface of the substrate and the circuit. A light source is mechanically and electrically attached respectively to the first planar surface and the circuit. The light source is located lateral to the light sensor at a first distance. A light signal of the light source emanates from the light source at an angle perpendicular to the first planar surface and a reflector mechanically attached to the first planar surface and located between the light sensor and the light source. The light signal is substantially reflected by the reflector away from the light sensor.