Fresnel Membrane Through-Hole Shielding for Wearable Optical Crosstalk
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Solution Overview
Problem
Existing Fresnel membranes in wearable devices suffer from optical crosstalk between optical emit and receive regions, leading to reduced sensitivity and accuracy in detecting bio-optical signals such as heart rate and blood oxygen saturation.
Innovation Solution
A Fresnel membrane design featuring a through-hole with light-shielding ink that separates the optical emit and receive regions, preventing direct light reflection between these areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ink is provided on surfaces of the Fresnel membrane to separate optical emit and receive regions, then optical separation is achieved, but optical crosstalk still occurs between the regions
Solution Approach 1:
The patent introduces a light-shielding layer as an intermediary element positioned between the optical emit region and optical receive region. This light-shielding layer acts as a mediator that blocks stray light and prevents direct optical coupling between the two regions, thereby eliminating optical crosstalk that cannot be fully prevented by surface ink alone. The light-shielding layer serves as a physical barrier that enforces optical separation more effectively than surface markings.
Solution Approach 2:
The patent transitions from two-dimensional surface ink patterns to a three-dimensional structure by adding a light-shielding layer with specific thickness and positioning. This dimensional change allows for more effective optical isolation, as the light-shielding layer can block light paths that would otherwise bypass surface ink through the bulk of the Fresnel membrane material.
2Ease of manufacture
If the Fresnel membrane structure is simplified without light-shielding layer, then manufacturing is easier, but sensitivity of optical detection is reduced
Solution Approach 1:
The patent segments the Fresnel membrane into distinct functional regions: optical emit region, optical receive region, and light-shielding layer. This segmentation allows each component to be optimized independently - the Fresnel teeth structure for light manipulation and the light-shielding layer for optical isolation - while maintaining overall manufacturing feasibility through integrated fabrication processes.
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 sensitivity and accuracy of bio-optical signal detection by eliminating optical crosstalk, thereby improving the performance of wearable devices in monitoring heart rate and blood oxygen.
Implementation Method 1
light-shielding ink that is stuffed in the through-hole, and the light-shielding ink divides the Fresnel membrane into two regions that are spaced apart from each other
Implementation Method 2
Fresnel teeth located on a surface of the substrate
Data Source
AI summary
This application provides example Fresnel membranes. One example Fresnel membrane includes a substrate and Fresnel teeth located on a surface of the substrate. The Fresnel membrane further includes a through-hole that is provided in a thickness direction of the Fresnel membrane and runs through the substrate and the Fresnel teeth. The through-hole extends to form a closed circle. The Fresnel membrane further includes light-shielding ink that is stuffed in the through-hole. The light-shielding ink divides the Fresnel membrane into two regions that are spaced apart from each other.