PPG and Laser Sensor Layout for Wrist-Worn Crosstalk Control
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Solution Overview
Problem
The challenge of miniaturizing electronic devices that incorporate multiple optical sensors with different optical characteristics is exacerbated by light crosstalk, limiting their effective arrangement within a confined space, particularly when worn on the user's wrist.
Innovation Solution
The electronic device incorporates a housing with a window and printed circuit board configuration that positions a PPG sensor and a laser sensor with specific beam angles, where the laser sensor is surrounded by the PPG sensor, utilizing an index layer and barrier to optimize sensor performance within a limited space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple optical sensors with different optical characteristics are disposed adjacent to each other, then the device can be miniaturized, but light crosstalk occurs and sensor performance deteriorates
Solution Approach 1:
The patent applies nesting by placing the laser sensor within the peripheral region defined by the PPG sensor, creating a nested arrangement where sensors are positioned one within another's coverage area. This allows maximum space utilization while maintaining optical isolation through the window structure.
Solution Approach 2:
The patent implements local quality by creating distinct optical zones through the window structure, where different regions of the window correspond to different sensor types. The window's first region and second region are positioned to selectively transmit light to appropriate sensors, ensuring each sensor receives optimized light quality without crosstalk.
2Reliability
If multiple optical sensors are disposed in different areas to optimize performance, then sensor performance is maintained, but the device cannot be miniaturized
Solution Approach 1:
The patent transitions from two-dimensional planar arrangement to three-dimensional spatial arrangement by utilizing the window structure that extends in multiple dimensions. Sensors are positioned at different depths and angles, with the window providing multi-regional light transmission paths, effectively using dimensional space to resolve the contradiction between performance and miniaturization.
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 arrangement allows the device to securely arrange and maintain the performance of both PPG and laser sensors, enabling the collection of various biometric data from the user.
Implementation Method 1
a PPG sensor that emits light to a part of the human body and receives light reflected from the body
Implementation Method 2
a laser sensor including at least one second emitting portion configured to emit light at a second beam angle smaller than the first beam angle toward the window, and at least one second receiving portion configured to receive light emitted from the at least one second emitting portion and reflected from the part of the user's body
Implementation Method 3
an index layer disposed on the laser sensor
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An electronic device according to one embodiment comprises: a housing; a printed circuit board; a window including a first area parallel to the printed circuit board and a second area connecting an edge of the first area and the housing; a photoplethysmogram (PPG) sensor including at least one first light-emitting unit and at least one first receiving unit configured to receive light, and disposed on the printed circuit board; a laser sensor including at least one second light-emitting unit and at least one second receiving unit configured to receive light that is emitted from the at least one second light-emitting unit and reflected from a body part of a user; and an index layer disposed on the laser sensor, wherein the laser sensor is disposed on the printed circuit board so as to be surrounded by the PPG sensor and overlaps the first area when the window is viewed from the outside of the electronic device.