Optical Sensor PCB Cavity Design for Noise Reduction
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Solution Overview
Problem
Photoplethysmography (PPG) systems are sensitive to noise and struggle to distinguish between heart rate, breath rate, and body motion, affecting blood flow measurements.
Innovation Solution
An optical sensing system with a compact design that includes a sensor connected to a printed circuit board (PCB) and a secondary optical lens filling gaps between the PCB and the sensor, enhancing accuracy and sensitivity by reducing form factor and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PPG systems use traditional optical sensing design, then the system can measure blood flow, but the system is sensitive to noise and cannot distinguish between heart rate, breath rate and body motion
Solution Approach 1:
The optical sensing system is divided into multiple independent optical paths with separate light sources and detectors. Each optical path targets specific tissue layers or measurement zones, allowing the system to segment different physiological signals (heart rate, breath rate, motion) into distinct measurement channels that can be processed and distinguished independently
Solution Approach 2:
The patent introduces optical coupling elements and positioning structures as intermediaries between the light sources and detectors. These intermediaries optimize light transmission paths, reduce stray light interference, and minimize cross-talk between different optical channels, thereby reducing noise and improving signal discrimination capability
2Volume of moving object
If the optical sensing system uses a compact design with secondary optical lens, then the form factor is reduced and noise interference is minimized, but the manufacturing complexity increases
Solution Approach 1:
The patent combines multiple optical components (primary optical lens, secondary optical lens, light sources, detectors) into a single integrated sensor module. The secondary optical lens is formed as part of the packaging structure rather than a separate component, merging optical functionality with mechanical housing to reduce overall form factor while streamlining manufacturing through fewer assembly steps
Solution Approach 2:
The packaging structure serves multiple functions: it provides mechanical support, optical coupling, noise isolation, and structural positioning. The secondary optical lens formed from packaging material simultaneously acts as an optical element and structural component, reducing the need for separate parts and simplifying the manufacturing process despite the compact design
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 system improves measurement accuracy and sensitivity by minimizing noise and motion artifacts, allowing for precise monitoring of heart rate and other physiological parameters.
Implementation Method 1
measuring the return signal (either through an extremity such as a finger or from reflections of the body)
Implementation Method 2
a secondary optical lens is formed on a material filling and encompassing gaps between the PCB cavity and the sensor
Data Source
AI summary
An optical sensing system is disclosed. The optical sensing system includes a printed circuit board (PCB), a supporter and an optical sensor. The PCB includes a top surface, a bottom surface and a through cavity, wherein the through cavity extends downwardly from the top surface to the bottom surface. The supporter has a top surface and a bottom surface. The optical sensor is bonded and coupled to the top surface of the supporter, wherein the optical sensor includes a primary optic structure. Wherein the supporter is flipped over and bonded to the PCB with the top surface facing the through cavity, so that the optical sensor is coupled to the PCB and at least partially extends to the through cavity. Associated electronic devices are also disclosed.