Optical Sensor with Rear Photodetector for Temperature Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical sensors used for measuring skin absorbance, such as those employing LEDs, face errors due to changes in light quantity caused by skin temperature, which can reduce accuracy in applications like blood glucose level estimation.
Innovation Solution
An optical sensor system with light sources and photodetectors arranged to account for temperature variations, using wavelength adjusters and direction adjusters to stabilize light emission and detection, and a processor to calculate absorbance based on light quantities from both front and rear surfaces of the light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LED light sources are used to measure skin absorbance, then the measurement process is simple and cost-effective, but the light quantity changes due to skin temperature effects, reducing measurement accuracy
Solution Approach 1:
The patent employs feedback by using a photodiode to continuously monitor the light output from the LED and using this information to adjust the measurement calculations. The system measures the actual light quantity emitted by the LED at each moment and uses this feedback to compensate for temperature-induced variations, thereby maintaining measurement accuracy without requiring complex temperature control hardware
Solution Approach 2:
The system performs self-characterization by automatically measuring its own LED light output characteristics under different temperature conditions during normal operation. The microcontroller captures the LED's light quantity data using the photodiode and stores this self-acquired information to correct subsequent measurements, eliminating the need for external calibration equipment or separate characterization procedures
2Measurement precision
If temperature compensation mechanisms are added to stabilize LED light output, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent introduces a photodiode as an intermediary component that indirectly measures the LED light output without requiring direct temperature sensing or control of the LED. This intermediary approach allows the system to compensate for temperature effects by measuring light quantity changes rather than directly controlling temperature, simplifying the overall system architecture while maintaining measurement accuracy
Solution Approach 2:
The patent replaces potential mechanical or thermal temperature control mechanisms with an optical measurement and computational approach. Instead of using active cooling/heating systems or temperature-controlled housings, the system uses optical detection (photodiode) combined with microcontroller-based calculations to compensate for temperature effects, significantly reducing mechanical complexity
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 stabilizes light sources and improves the accuracy of absorbance measurements by accounting for temperature-induced changes, enhancing the reliability of skin absorbance analysis.
Implementation Method 1
a photodiode chip becoming the light quantity monitor of light emitted from the light emitting diode chip
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An optical sensor (300) includes light sources (311-315) configured to emit light, a substrate (320) on which the light sources (311-315) are mounted, the substrate (320) comprising holes (321-325) in regions on which the light sources (311-315) are mounted, and a first photodetector (330) configured to receive a first light emitted from a front surface of each of the light sources (311-315), the first light being reflected or scattered from an object (OBJ). The optical sensor (300) further includes at least one second photodetector (341-345) configured to receive a second light emitted from a rear surface of each of the light sources (311-315), the second light passing through the holes (321-325) corresponding to the light sources (311-315).