Microlens Array Optical Lens for PPG Light Reflection Reduction
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Solution Overview
Problem
Light emitted from a light-transmitting cover plate in devices such as photoplethysmographs is reflected and dispersed due to different refractive indexes, leading to reduced light efficiency, energy, and maximum intensity, affecting user experience and detection accuracy.
Innovation Solution
An optical lens with a microlens array is introduced, comprising a light-transmitting substrate and microlens assemblies that converge light beams to reduce reflection and dispersion, enhancing light efficiency and intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a light-transmitting cover plate is used to protect the light emitter, then the light emitter is protected from water, dust, and scratches, but light reflection occurs at the cover plate surfaces, reducing light emitting efficiency and energy
Solution Approach 1:
An optical lens is introduced as an intermediary component between the light emitter and the cover plate. The lens converges light beams before they reach the cover plate, reducing the incident angle and subsequent reflection at the cover plate surfaces. This mediator resolves the contradiction by maintaining the protective function of the cover plate while minimizing light loss through optical intervention.
2Strength
If light passes through the cover plate, then the cover plate provides protection, but the light emitting angle becomes large, reducing the maximum intensity of emitted light
Solution Approach 1:
The optical lens performs preliminary action by converging light beams before they reach the cover plate. This pre-convergence reduces the light emitting angle and increases the maximum intensity of light that will eventually pass through the cover plate, while the cover plate maintains its protective function.
3Loss of energy
If a microlens array is added to reduce reflection and improve light efficiency, then light emitting efficiency and intensity are improved, but the device structure becomes more complex
Solution Approach 1:
The optical lens employs a microlens array that segments the optical function into multiple small lenses arranged in an array. Each microlens handles a portion of the light beam, collectively achieving the desired light convergence and reflection reduction. This segmentation approach improves light efficiency while keeping each individual microlens simple in structure.
4Loss of energy
If the microlens array occupies more height to improve light convergence, then light emitting efficiency is improved, but the space available for installation in the electronic device is reduced
Solution Approach 1:
The microlens array utilizes parameter changes in the micro-scale domain. By reducing the size and curvature parameters of individual microlenses while maintaining their converging function, the overall height of the optical lens is minimized. This allows effective light convergence to be achieved within a compact height suitable for electronic device installation.
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 microlens array improves light emitting efficiency, increases light energy and maximum intensity, and enhances measurement accuracy and perfusion index by reducing reflection and dispersion at the cover plate.
Implementation Method 1
light beams emitted by the light emitter may be converged by using the first microlens and the second microlens
Implementation Method 2
a light emitting angle of light emitted from the cover plate can be reduced
Data Source
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AI summary
This application provides an optical lens, a photoplethysmograph, and an electronic device, relating to the technical field of electronic devices, to solve the problem of how to reduce reflectivity of light at a cover plate, reduce a light emitting angle of light emitted from the cover plate, increase light energy and a maximum intensity of light entering a human body, and improve measurement accuracy and a perfusion index. The optical lens includes a light-transmitting substrate and a microlens array. The light-transmitting substrate has a first surface and a second surface opposite to each other. The microlens array is arranged on the first surface, and the microlens array includes a first microlens assembly and a plurality of second microlens assembly arrays. Each of the second microlens assembly arrays includes a plurality of second microlens assemblies arranged around the first microlens assembly in an array. The first microlens assembly and the second microlens assembly each include a first microlens unit and a second microlens array. The second microlens array includes a plurality of second microlenses arranged around the first microlens unit in an array. The optical lens provided in this application is used to reduce a light emitting angle.