Optical Sensor Self-Calibration for Thermal Drift in Bio-Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical sensors face accuracy issues due to changes in light source spectrum or intensity caused by heat generation, temperature fluctuations, and varying thermal characteristics, making it difficult to calibrate multiple light sources effectively.
Innovation Solution
The optical sensor employs an internal light source and detector arrangement with a partition wall and reflective surface, along with a processor that performs initial and additional calibrations using spectral transmission constants and lock-in detection techniques to maintain accuracy, adjusting for environmental changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate scattering reflector is used to measure light source spectrum for calibration, then calibration can be performed, but the system becomes complex and difficult to implement
Solution Approach 1:
The patent extracts the calibration function from a separate scattering reflector system and integrates it into the optical sensor itself by using the skin as the reflector. This eliminates the need for external calibration components while maintaining calibration capability, thereby reducing system complexity.
Solution Approach 2:
The optical sensor uses the subject's skin to perform self-calibration by measuring the spectrum reflected from the skin. The skin serves dual purposes: as the target for bio-information measurement and as the scattering reflector for calibration, eliminating the need for separate calibration hardware.
2Adaptability or versatility
If multiple light sources are used to improve measurement capability, then measurement versatility increases, but calibration becomes difficult due to different thermal characteristics
Solution Approach 1:
The patent makes the skin serve multiple functions: it acts as both the target for bio-information measurement and the scattering reflector for calibration. This universal approach allows the same interface to handle both measurement and calibration tasks, eliminating calibration difficulties associated with multiple light sources.
Solution Approach 2:
The skin acts as an intermediary element that mediates between the light sources and the detector. By measuring the skin's reflected spectrum, the system can calibrate for each light source individually through their thermal characteristics while maintaining overall measurement versatility.
3Measurement precision
If calibration is performed frequently to maintain accuracy, then measurement precision is maintained, but time loss increases
Solution Approach 1:
The patent performs calibration automatically and continuously in the background during normal operation, rather than requiring separate calibration steps. The optical sensor continuously measures the skin's reflected spectrum to track and compensate for thermal drift, eliminating the need for manual calibration interruptions.
Solution Approach 2:
The calibration process continues uninterrupted during normal bio-information measurement operations. The system continuously monitors and adjusts for thermal changes in real-time, maintaining measurement precision without requiring separate calibration time slots.
4Measurement precision
If the optical sensor contacts skin for measurement, then bio-information can be measured, but temperature change from skin contact affects light source performance
Solution Approach 1:
The patent uses the skin's reflected spectrum as feedback to monitor thermal changes in the light source. By continuously measuring the skin's optical properties, the system detects temperature-induced shifts in light source performance and automatically compensates through calibration adjustments.
Solution Approach 2:
The skin serves as an intermediary thermal buffer between the light source and the measurement system. The skin's thermal mass and heat transfer properties moderate temperature changes from skin contact, protecting the light source from direct thermal effects while still enabling accurate measurement.
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 enhances the accuracy of bio-information estimation by compensating for environmental variations, ensuring reliable and precise bio-information measurements.
Implementation Method 1
an optical sensor uses a separate scattering reflector to measure a spectrum of a light source before measuring spectrum of human skin
Implementation Method 2
one of the detectors is arranged to detect a portion of the light emitted by the light sources, and the other detector is arranged to detect a portion of the light diffusely reflected by the sample and a reference standard
Implementation Method 3
An absorbance of the sample is calculated based on the detected light signals
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method of calibrating an optical sensor (110) may include acquiring a first characteristic for an external light source through a detector (25) of an optical sensor while an internal light source (24) of the optical sensor is turned off; driving the internal light source (24); acquiring a second characteristic for the internal light source and the external light source through the detector (24), based on driving the internal light source; and acquiring a reference characteristic of the internal light source, for calculation of an absorbance of an object, based on the first characteristic and the second characteristic.