Retroreflector Light Collection for Wearable Sensors
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Solution Overview
Problem
Existing electronic devices face challenges in effectively collecting and redirecting reflected and scattered light for accurate sensor signal measurement, particularly in biological tissues, due to light scattering and interference with electromagnetic and capacitive signals.
Innovation Solution
Incorporating a retroreflector within the electronic device, such as a wristwatch, with a substrate having a reflective surface configured to redirect reflected and/or scattered light back towards the body tissue, enhancing signal collection and minimizing light scattering, using geometric elements like corner cubes, cat's eyes, or hemispheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metallic surfaces are used to reflect and redirect light to improve sensor performance, then light collection efficiency is improved, but electromagnetic and capacitive signal detection is interfered with
Solution Approach 1:
The patent changes the material parameter from metallic to non-metallic (such as white paint or other non-conductive reflective materials) while maintaining the reflective function. This parameter change eliminates electromagnetic and capacitive interference while preserving light reflection capabilities, thus resolving the contradiction between improved sensor signal detection and reduced signal interference.
2Measurement precision
If light emitter intensity is increased to improve signal collection, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent converts scattered light, which was previously considered wasted or harmful, into useful signal by implementing retroreflectors that redirect scattered light back toward the photodetector. This converts the harmful scattering effect into a beneficial signal enhancement, improving measurement precision without increasing light emitter intensity or energy consumption.
3Measurement precision
If retroreflectors are added to redirect scattered light, then light collection efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges the retroreflector function with existing device components such as the back crystal or housing surfaces. By integrating the retroreflective functionality into already-present structural elements rather than adding separate components, the patent improves light collection efficiency while minimizing increases in device complexity.
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
Improves the detection of physiological signals and proximity measurements, while also potentially saving battery life by optimizing light collection and reducing the need for increased light emitter intensity.
Implementation Method 1
a retroreflector capable of redirecting reflected and/or scattered light out of the device toward body tissue and configured to minimize light scattering. As used herein, the term 'retroreflector' refers to a component capable of reflecting light back along a direction that is parallel or nearly parallel to but opposite in direction from the light source irrespective of the angle of incidence
Implementation Method 2
For example, photoplethysmographic (PPG) sensors may consist of infrared or green light-emitting diodes (LEDs) and photodetectors for measuring heart rate, oxygen saturation (SpO2), etc.
Implementation Method 3
Sensors for measuring various types of signals, including physiological signals, often illuminate an individual's tissue with light from a light source and then measure the light that is reflected back onto a detector
Data Source
AI summary
The present disclosure relates generally to electronic devices and methods for sensor signal collection. The electronic devices may include retroreflectors for redirecting scattered light back to the photodetector. The retroreflectors may be positioned at various locations on or in the electronic device, and may employ various geometric elements having retroreflective capability.