Infrared Heart Rate Sensor for Dark Skin Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fitbit-type devices inaccurately measure heart rates, particularly for individuals with darker skin tones, due to melanin absorption of green light, leading to insufficient photon penetration and unreliable data.
Innovation Solution
The use of infrared radiation directed parallel to and just under the skin surface, with a collimated beam, to maximize blood volume variation measurement, avoiding deep penetration and leveraging deeper skin blood supply changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If green light is used for heart rate measurement, then measurement capability is achieved, but measurement precision deteriorates for darker skin tones due to melanin absorption
Solution Approach 1:
The patent changes the wavelength parameter of the light source from green (typically 520-560nm) to red (610-680nm) or infrared (700-1000nm). This parameter change allows the light to penetrate melanin more effectively while still being absorbed by hemoglobin, thereby resolving the contradiction between achieving measurement capability and maintaining precision across different skin tones.
2Reliability
If light penetrates deep into the skin, then blood volume measurement is enhanced, but measurement reliability decreases due to insufficient photon return
Solution Approach 1:
The patent optimizes the wavelength parameter to find the optimal balance point where light penetrates sufficiently deep to capture blood volume variations during cardiac cycles, yet maintains enough photon return for reliable detection. Red and infrared wavelengths provide this optimal balance by experiencing less absorption from melanin while still interacting with hemoglobin at appropriate depths.
3Adaptability or versatility
If existing fitbit devices are used on darker skin, then device compatibility is maintained, but measurement accuracy deteriorates significantly
Solution Approach 1:
The patent modifies the optical parameter (wavelength) of the light source to create a version of the fitbit device that is adapted for darker skin tones. By using red or infrared light instead of green light, the device maintains its wearability and functionality while achieving accurate heart rate measurements across all skin tones, thus resolving the contradiction between device compatibility and measurement precision.
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 approach significantly improves heart rate measurement accuracy for both darker and lighter skin tones by maximizing blood volume variation detection just below the skin surface, enhancing the reliability of heart rate data acquisition.
Implementation Method 1
The use of infrared radiation directed parallel to and just under the skin surface, with a collimated beam, to maximize blood volume variation measurement
Implementation Method 2
due to melanin absorption of green light, leading to insufficient photon penetration and unreliable data
Data Source
AI summary
A device and a means to measure the periodic change in blood supply volume, from which the heart rate can be inferred. The device is useful for equipment intended to track the physical activity of animals, including humans, particularly if they are engaging in some sort of physical activity designed to improve the physical performance of the animal. One possible application is to improve the accuracy of the fitbit devices used by dark skinned humans.