Light Guide Ear Thermometer Resolves Standoff Distance Trade-off
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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 has varying physiology, 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 smaller diameter waveguide to fit alongside earpiece components, and compensates for thermal gradients using regression analysis to improve accuracy across varying ambient temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature sensor is positioned deeper into the ear canal to reduce standoff distance, then measurement precision is improved, but device complexity and ease of operation worsen due to obstruction by earpiece components and difficulty in proper insertion
Solution Approach 1:
A light guide acts as an intermediary optical element, transmitting infrared radiation from the tympanic membrane to the thermopile sensor. This allows the sensor to be positioned away from the eardrum (reducing insertion depth requirements) while maintaining measurement accuracy, as the light guide bridges the gap between the eardrum and sensor positions.
Solution Approach 2:
The patent transitions from direct contact measurement to optical measurement through a light guide, effectively changing the measurement dimension. The sensor can be positioned outside or at the entrance of the ear canal while the light guide extends the measurement capability to the eardrum, resolving the conflict between insertion depth and measurement precision.
2Ease of operation
If the temperature sensor is positioned outside the ear canal to improve ease of operation, then ease of operation is improved, but measurement precision deteriorates due to increased standoff distance
Solution Approach 1:
The light guide serves as an optical intermediary that extends the sensor's field of view to the eardrum. This allows the sensor to be positioned conveniently outside or at the entrance of the ear canal while the light guide transmits infrared radiation from the eardrum to the sensor, maintaining measurement precision despite increased physical distance.
Solution Approach 2:
The patent uses optical transmission through the light guide to overcome the spatial limitation. By transitioning from direct physical contact to optical field transmission, the system allows the sensor to be positioned in a different spatial dimension (outside the ear canal) while maintaining measurement accuracy through the light guide's optical path.
3Measurement precision
If a larger diameter thermopile sensor is used to improve measurement precision, then measurement precision is improved, but device complexity worsens due to difficulty in fitting alongside earpiece components
Solution Approach 1:
The light guide acts as an optical intermediary that decouples the sensor size from the measurement aperture size. A larger thermopile sensor can be used to improve measurement precision and signal strength, while the light guide transmits the infrared radiation from the eardrum to the larger sensor, allowing the sensor to be positioned alongside other earpiece components without requiring a large insertion aperture.
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 body core temperature measurement with reduced error, improving prediction accuracy from approximately 4 degrees C to less than 1 degree C across a range of ambient temperatures by accounting for waveguide and ambient temperature variations.
Implementation Method 1
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
Implementation Method 2
a thermopile sensor, allowing for a smaller diameter waveguide to fit alongside earpiece components
Data Source
AI summary
An apparatus for measuring body core temperature includes a light guide. The light guide can be coupled to an earpiece, or it can be a standalone device. The apparatus also includes a sensor positioned at one end of the light guide, and a processor coupled to the sensor. The sensor is operable to sense infrared radiation from an infrared source at the opposite end of the light guide. The processor is operable to determine a temperature of the infrared source at the opposite end of the light guide via a transfer function that correlates a measurement of the infrared radiation observed by the sensor and an effect of radiation of the light guide.