UV Index Sensor Using Segmented Photosensors
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Solution Overview
Problem
Current UV index measuring sensors are expensive and difficult to accurately set spectral responses to the McKinlay-Diffey erythemal action spectrum curve, making them costly and inefficient.
Innovation Solution
The use of three photosensors with specific spectral responses in different wavelength sections (250-298 nm, 298-328 nm, and 328-400 nm) calibrated using reference solar light to calculate the UV index, with each photosensor being an ultraviolet light emitting diode (UV LED), and a processor to amplify and adjust signals for accurate measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UV photodiode with multiple thin film coating is used to match the McKinlay-Diffey erythemal action spectrum curve, then measurement accuracy is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent divides the UV spectrum into three wavelength sections (250-298 nm, 298-328 nm, and 328-400 nm) and uses separate photosensors for each section. This segmentation allows each photosensor to be optimized for its specific wavelength range, eliminating the need for complex multi-layer coatings while achieving accurate spectral response matching.
Solution Approach 2:
The patent changes the approach from using a single photodiode with adjusted coating parameters to using multiple photosensors with different spectral response characteristics. By selecting photosensors with naturally different wavelength sensitivities and combining them with appropriate weighting factors, the system achieves accurate spectral matching without complex manufacturing processes.
2Measurement precision
If special thin film coating is applied to the UV photodiode to achieve McKinlay-Diffey spectral response, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the UV measurement function across three separate photosensors, each responding to different wavelength sections. This eliminates the need for expensive special coating processes on a single photodiode, as standard photosensors can be used and combined through software weighting to achieve the desired spectral response.
Solution Approach 2:
Instead of modifying a single photodiode with complex coatings to copy the McKinlay-Diffey spectral response, the patent creates a computational copy of the spectral response by combining three photosensors with different spectral characteristics and applying appropriate weighting factors in the calculation.
3Device complexity
If a single UV photodiode is used with adjusted spectral response, then device simplicity is maintained, but accuracy in matching the McKinlay-Diffey curve becomes difficult to achieve
Solution Approach 1:
The patent segments the spectral response requirement into three separate photosensors, each optimized for a specific wavelength section. This segmentation enables high measurement precision while keeping each individual sensor simple, as each photosensor only needs to respond to its designated wavelength range rather than requiring complex spectral shaping.
Solution Approach 2:
The patent merges the outputs of three simple photosensors with different spectral responses through a computational combination using weighting factors. This merging process integrates their individual spectral characteristics to produce an overall response that accurately matches the McKinlay-Diffey curve, achieving both simplicity and accuracy.
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 provides a low-cost, accurate method for measuring the UV index by calibrating and summing the signals from the UV LEDs, ensuring alignment with the McKinlay-Diffey erythemal action spectrum curve, thus effectively addressing the cost and accuracy issues of existing sensors.
Implementation Method 1
measuring first photocurrent of the first photosensor, second photocurrent of the second photosensor, and third photocurrent of the third photosensor
Data Source
AI summary
An ultraviolet index measuring method and apparatus includes preparing a first photosensor having spectral response only in a first section of a wavelength between 250 nm and 298 nm, a second photosensor having spectral response only in a second section of a wavelength between 298 nm and 328 nm, and a third photosensor having spectral response only in a third section of a wavelength between 328 nm and 400 nm. An output signal of the first photosensor, an output signal of the second photosensor, and an output signal of the third photosensor are calibrated using spectral irradiance of reference solar light. First photocurrent of the first photosensor, second photocurrent of the second photosensor, and third photocurrent of the third photosensor are measured under a measurement environment. An ultraviolet index is calculated using the first photocurrent, the second photocurrent, and the third photocurrent under the measurement environment.