Optical Particle Sensor Multi-Wavelength Detection
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Solution Overview
Problem
Current optical particle sensors are limited by narrow wavelength sensitivity, making it difficult to use low-cost mass-produced components for detecting particles at multiple wavelengths, which is necessary for accurate particle identification and size measurement, especially for distinguishing between different types of pollen and fungal spores.
Innovation Solution
An optical particle sensor system using at least two light sources of different wavelengths, where a first light source is used for continuous detection and to determine particle position, and a second light source is operated with a high drive signal and short pulse to enhance signal-to-noise ratio, allowing for detection of light emitted from particles using a shared optical detector with improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light sources of different wavelengths are used for particle identification, then particle identification capability is improved, but device cost and complexity increase
Solution Approach 1:
The patent combines multiple light sources (UV LED at 365nm and visible LED at 630nm) into a single optical detection system that shares common optical path and detector resources. This merging approach enables multi-wavelength particle identification while avoiding the need for separate detection systems for each wavelength, thereby reducing overall device complexity and cost.
Solution Approach 2:
The optical detector is designed to universally detect both scattered light from visible illumination and fluorescence from UV illumination. The single detector performs multiple functions: detecting particles illuminated by the visible LED and detecting fluorescent particles illuminated by the UV LED, eliminating the need for wavelength-specific detectors and simplifying the system architecture.
2Measurement precision
If UV light source is operated at high intensity for fluorescence detection, then signal-to-noise ratio is improved, but light source lifespan is reduced
Solution Approach 1:
The UV LED is operated in a pulsed manner rather than continuously. The controller activates the UV LED only during specific time windows when particles are expected to pass through the detection zone, delivering high-intensity pulses that achieve excellent signal-to-noise ratio for fluorescence detection while keeping the average power consumption and thermal stress low, thereby extending LED lifespan.
Solution Approach 2:
The system uses the visible LED to continuously monitor and detect particles before they reach the fluorescence detection zone. When a particle is detected by the visible LED, the controller preliminarily identifies its position and then activates the UV LED at the appropriate moment to illuminate the particle for fluorescence detection, ensuring the UV LED is only active when needed.
3Device complexity
If a single optical detector is used for both wavelengths, then device cost is reduced, but detection sensitivity at non-peak wavelengths is reduced
Solution Approach 1:
The controller dynamically adjusts the drive current of the UV LED to compensate for the detector's lower sensitivity at 365nm compared to its peak sensitivity at 970nm. By increasing the UV LED drive current during fluorescence detection, the system compensates for the wavelength mismatch and maintains high detection sensitivity despite using a single cost-effective detector.
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 enables accurate particle identification and size measurement using low-cost components, improving sensitivity and reducing noise interference, while extending the life of UV light sources through low duty cycle operation.
Implementation Method 1
Each particle is illuminated by a continuous light source and creates a light pulse with a duration determined by the passage time of the particle through the detection volume
Implementation Method 2
The UV illumination can give rise to fluorescence whereas the visible and IR illumination give rise to scattering
Data Source
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AI summary
The invention provides an optical particle sensor which uses light sources of different first and second wavelengths. A first light source is used to detect light scattering and also to determine when a particle reaches a target positional area. In response to the particle being determined to reach the target positional area, a second light source is operated to provide a pulse of light, and light emitted from the particle in response to the pulse of light is detected by the same detector.