Optoelectronic Biosensor Refractive Index Light Guidance
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Solution Overview
Problem
Optical biosensors face challenges in improving the signal-to-noise ratio due to strong scattering and absorption of light by tissue layers, leading to a significant DC component that worsens the signal/noise ratio and limits their effectiveness in measuring physiological parameters like heart rate.
Innovation Solution
The biosensor employs a transparent contact surface with a first optical fiber element that guides light at an angle dependent on the refractive indices, allowing light from deeper tissue layers to be reflected back while scattering from surface layers is refracted out, thereby reducing DC components and enhancing the signal-to-noise ratio. This is achieved through the use of materials with different refractive indices for the optical fiber and surrounding elements, allowing for effective suppression of stray light even at small distances between the emitter and detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is emitted toward tissue layers for detection, then physiological parameters can be measured, but strong scattering by surface tissue layers creates a large DC component that worsens the signal-to-noise ratio
Solution Approach 1:
The patent segments the detected light into two distinct components: modulated light from deeper perfused tissue layers and non-modulated DC light from surface layers. By using separate optical paths and detection mechanisms, the system processes these segments differently, extracting the useful modulated signal while rejecting the harmful DC component from surface scattering.
Solution Approach 2:
The patent extracts and removes the harmful DC component from the total detected light signal. Through optical filtering and selective detection, the system separates the useful modulated light signal from the unwanted non-modulated DC light, effectively taking out the harmful factor that degrades measurement precision.
2Volume of moving object
If the distance between emitter and detector is reduced for compact design, then device size decreases, but light scattering from surface layers increases relative to useful signal
Solution Approach 1:
The patent applies local quality by giving different regions of the biosensor different optical properties. The emitter and detector are positioned with specific geometric relationships, and selective optical elements are placed in specific locations to enhance collection of useful light while suppressing surface scattering. This localized optimization allows compact design without sacrificing measurement precision.
Solution Approach 2:
The patent transitions from considering only the vertical distance between emitter and detector to incorporating angular and spatial dimensions. By optimizing the angular acceptance of the detector and the spatial arrangement of optical elements, the system can maintain compact size while selectively collecting light from deeper tissue layers and rejecting surface scattering through directional control.
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 approach improves the signal-to-noise ratio by selectively guiding useful light signals from deeper tissue layers while reducing noise from surface scattering, enabling smaller biosensor designs suitable for applications like fingertip or ear canal measurements, with increased penetration depth and accuracy in detecting physiological parameters.
Implementation Method 1
a first optical fiber element is arranged between the detector device and the supporting surface. This is designed to guide light at an angle smaller than a predetermined angle to a perpendicular to the support surface in the direction of the detector device. The predetermined angle depends at least on a difference of the refractive indices at an interface between the optical fiber element and a material surrounding the optical light guide element.
Implementation Method 2
light which strikes the contact surface at a relatively steep angle, i.e. a small angle with respect to a perpendicular, originates primarily from deeper tissue layers. This light component contains, among other things, a particularly high proportion of light which interacted with hemoglobin or blood. On the other hand, light from the non-perfused tissue layers near the surface strikes the respective contact surface at a particularly large angle to the perpendicular.
Data Source
AI summary
An optoelectronic biosensor includes a housing with a transparent support surface. The optoelectronic biosensor also includes an emitter device in a first region of the housing adapted to generate and emit light toward the support surface. The optoelectronic biosensor further includes a detector device in a second region of the housing. The optoelectronic biosensor additionally includes a first optical fiber element between the detector device and the support surface. The first optical fiber element is configured to guide light incident on the support surface at an angle less than a predetermined angle to a normal to the detector device. The predetermined angle depends at least on a difference in refractive indices at an interface between the optical fiber element and a material surrounding the optical light guide element. A material of the first region surrounding the emitter device is the same as the material surrounding the first optical fiber element.