Photoplethysmography Sensor Optics for Compact Lateral Offset
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Solution Overview
Problem
Existing photoplethysmography sensors require a lateral offset of greater than 2mm between the light source and the light detector, limiting the compactness and miniaturization of these devices.
Innovation Solution
The apparatus employs optics that allow for a lateral offset of less than 2mm between the light source and the light detector by using diffractive structures to redirect light from the source to an offset region, enabling efficient light detection while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lateral offset between light source and light detector is reduced to less than 2mm, then the device compactness is improved, but the optical path length may be insufficient for effective light detection
Solution Approach 1:
The patent introduces a vertical dimension to the optical path by positioning the light source above the light detector with a lateral offset of less than 2mm. The light travels vertically through the tissue and is detected by the detector below, enabling compact lateral spacing while maintaining sufficient optical path length through vertical arrangement. This dimensional change resolves the contradiction between compactness and adequate optical path length.
Solution Approach 2:
The patent employs an optical waveguide or light guide structure as an intermediary element between the light source and light detector. This intermediary component channels and directs the light path, allowing the light to travel a sufficient distance through the tissue even when the source and detector are laterally close together. The waveguide mediates the optical path to achieve both compactness and adequate detection path length.
2Length of stationary object
If the lateral offset between light source and light detector is greater than 2mm, then the optical path length is sufficient for effective light detection, but the device size increases
Solution Approach 1:
The patent transitions from a horizontal optical path arrangement to a vertical arrangement, where the light source is positioned above the light detector with minimal lateral offset. This vertical configuration allows the optical path to extend through the tissue depth rather than laterally, achieving sufficient detection path length while minimizing device footprint and overall size.
Solution Approach 2:
The patent merges the light source and light detector into a closely integrated configuration with lateral offset less than 2mm, combining these components in a compact arrangement. By integrating the source and detector vertically aligned with minimal separation, the device achieves space efficiency while maintaining functional effectiveness through the vertical optical path through tissue.
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 configuration allows for a more compact and potentially smaller scale photoplethysmography sensor, while maintaining the necessary optical path length for effective light detection and signal processing.
Implementation Method 1
The apparatus employs optics that allow for a lateral offset of less than 2mm between the light source and the light detector by using diffractive structures to redirect light from the source to an offset region
Data Source
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AI summary
An apparatus comprising: a light detector; a light source, laterally offset from the light detector by a first lateral offset; optics configured to receive light emitted by the light source and output the received light, wherein a majority of the light output is directed towards an offset region laterally offset from the light detector by at least a second lateral offset different from the first lateral offset.