Ear Thermometer Light Guide for Core Temperature Measurement
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Solution Overview
Problem
Existing body core temperature measurement methods through the tympanic membrane face challenges when the ear canal is obstructed or the subject's physiology is different, making it difficult for temperature sensors to obtain reliable readings due to increased standoff distance, which requires an optical design that allows the sensor to be positioned less deeply or outside the ear canal while maintaining a clear field of view.
Innovation Solution
A device using a light guide and optional lens system, where the light guide is a hollow reflective tube or optic fiber that guides long-wave infrared radiation from the tympanic membrane to a thermopile sensor, allowing for a larger sensor size while fitting within the ear canal, and compensates for thermal gradients using regression analysis and additional temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature sensor is positioned deeper into the ear canal to obtain a reliable reading, then the measurement precision is improved, but the device complexity and difficulty of operation increase due to obstruction by other components and physiological variations
Solution Approach 1:
The patent transitions from direct optical path measurement to indirect measurement through a light guide. The sensor is positioned at the end of the light guide where it can detect infrared radiation that has traveled through the ear canal via the light guide's internal reflections, effectively measuring temperature from a different spatial dimension without requiring the sensor to be deeply inserted into the ear canal
Solution Approach 2:
The light guide acts as an intermediary between the tympanic membrane and the temperature sensor. It captures and guides infrared radiation from the eardrum to the sensor, eliminating the need for direct line-of-sight measurement and allowing the sensor to be positioned outside or at the entrance of the ear canal while still obtaining accurate temperature readings
2Ease of operation
If the sensor is positioned outside the ear canal to simplify operation, then the ease of operation is improved, but the measurement precision deteriorates due to increased standoff distance
Solution Approach 1:
The light guide serves as a mediator that extends the sensor's effective reach into the ear canal. By positioning the sensor at the external end of the light guide, the system maintains ease of operation while the light guide transmits infrared radiation from the distant tympanic membrane to the sensor, effectively bridging the standoff distance gap
Solution Approach 2:
The system changes the measurement dimension by using the light guide's internal reflective surface to redirect infrared radiation. Instead of requiring the sensor to be physically close to the eardrum, the light guide captures radiation at one dimension (ear canal entrance) and delivers it to the sensor at another dimension (external position), maintaining precision while improving accessibility
3Difficulty of detecting and measuring
If a larger sensor is used to improve detection capability, then the detection sensitivity is improved, but the device complexity increases due to space constraints in the ear canal
Solution Approach 1:
The light guide acts as an intermediary optical system that decouples sensor size from measurement capability. A larger sensor can be positioned at the external end of the light guide where space is abundant, while the light guide's narrow internal diameter accommodates the spatial constraints within the ear canal, allowing the sensor to be substantially filled by the tympanic membrane's field of view without requiring deep insertion
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 solution enables accurate body core temperature measurement with reduced error, improving prediction accuracy from approximately 4 degrees C to less than 1 degree C across varying ambient temperatures by minimizing waveguide radiation interference and accounting for thermal gradients.
Implementation Method 1
The light guide is highly reflective to the long wave infrared (LWIR) radiation from the tympanic membrane, and guides the LWIR to the thermopile sensor
Implementation Method 2
a thermopile sensor (or other detector)... senses the infrared radiation
Data Source
AI summary
A device for measuring body core temperature includes a light guide. The light guide is coupled to an earpiece. A first sensor is positioned at a first end of the light guide, and a second sensor is positioned at a second end of the light guide. A processor is coupled to the first sensor and the second sensor. The first sensor senses infrared radiation from an infrared source at the second end of the light guide, and the second sensor measures a temperature of the light guide at the second end of the light guide. The processor determines a temperature of the infrared source at the second end of the light guide by compensating for infrared radiation due to a thermal gradient of the light guide via a regression analysis across a range of ambient temperatures of the light guide.