Optical Sensor With Wavelength Filters For Heart Rate And Blood Oxygen
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Solution Overview
Problem
Existing optical sensors that capture heart rate and blood oxygen content are limited in their ability to simultaneously and efficiently measure both parameters with high accuracy and energy efficiency.
Innovation Solution
An optical sensor utilizing a light source with a light-emitting semiconductor chip emitting electromagnetic radiation in three different wavelength ranges (green, red, and infrared) and three light detectors with specific filters, combined with a conversion phosphor made of narrowband quantum dots, allowing for simultaneous measurement of heart rate and blood oxygen content with reduced energy consumption and stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single light source emits multiple wavelength ranges to enable simultaneous measurement of heart rate and blood oxygen content, then measurement functionality is improved, but stray light and measurement precision deteriorate
Solution Approach 1:
The patent divides the light detection function into three separate light detectors, each equipped with a specific wavelength filter (green, red, or infrared). This segmentation allows each detector to measure only its designated wavelength range, preventing stray light from other wavelengths from interfering with the measurement, while still enabling simultaneous measurement of all three parameters (heart rate via green, blood oxygen via red and infrared)
Solution Approach 2:
The patent introduces wavelength-selective filters as intermediary components between the light source and the photodetector. These filters act as mediators that selectively transmit only the desired wavelength range to each photodetector while blocking other wavelengths, thereby eliminating stray light interference and improving measurement precision
2Measurement precision
If multiple separate light sources are used for different wavelength ranges, then measurement precision is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent combines three separate light sources (green LED, red LED, infrared LED) into a single integrated light source module with three separate light-emitting semiconductor chips. This merging reduces structural complexity and the number of components while maintaining the precision of wavelength-separated measurement through the use of individual filters for each detector
3Measurement precision
If continuous light emission is used for accurate measurement, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent employs periodic pulsed light emission instead of continuous illumination. The control unit activates each light-emitting semiconductor chip in alternating pulses (green, red, infrared sequentially), and the photodetectors measure the reflected light during these pulses. This periodic action maintains sufficient signal quality for accurate measurement while significantly reducing overall energy consumption compared to continuous emission
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
Enables accurate and efficient simultaneous measurement of heart rate and blood oxygen content with reduced energy usage and minimal stray light, improving the sensor's accuracy and skin friendliness.
Implementation Method 1
the light source includes a conversion phosphor, the conversion phosphor converts the light of the semiconductor chip into electromagnetic radiation with the first wavelength range, the second wavelength range and the third wavelength range
Implementation Method 2
a first filter is transmissive for light of the first wavelength range and non-transmissive for light of the second wavelength range and the infrared radiation of the third wavelength range
Implementation Method 3
the intensity of the scattered light can be measured using a photodetector... the intensity of the scattered light also varies with the heart rate. This changing intensity can be detected by the photodetector
Implementation Method 4
the light is scattered by tissue below the skin and the intensity of the scattered light can be measured using a photodetector
Implementation Method 5
Some of the radiated-in light is absorbed by hemoglobin molecules in the blood... More of the light of the light-emitting diode, or less, is absorbed by the hemoglobin
Data Source
AI summary
An optical sensor that captures a heart rate and/or a blood oxygen content includes a light source including a light emitter that emits electromagnetic radiation with a first wavelength range including green light, a second wavelength range including red light and a third wavelength range including infrared radiation, and three light detectors, each including a filter for electromagnetic radiation, wherein a first filter is transmissive for light of the first wavelength range and non-transmissive for light of the second wavelength range and the infrared radiation of the third wavelength range, a second filter is transmissive for light of the second wavelength range and non-transmissive for light of the first wavelength range and the infrared radiation of the third wavelength range and a third filter is transmissive for the infrared radiation of the third wavelength range and non-transmissive for light of the first and the second wavelength range.