Semiconductor Laser Particle Sizing Using Inhomogeneous Intensity
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Solution Overview
Problem
Existing methods for determining particle distributions, such as PM1, PM2.5, and PM10, face challenges in accurately measuring particle sizes due to varying signal strengths from particles passing through laser beams, especially for small particles, leading to inaccuracies in particle distribution analysis.
Innovation Solution
A method using a laser apparatus with a semiconductor laser emitting light with an inhomogeneous intensity profile to evaluate frequency distributions of signal strengths, applying diameter and frequency corrections based on the laser's sensitivity, and storing the corrected data for precise particle diameter determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a particle passes through an edge region of the laser beam, then the detection time increases and detection amplitude increases, but the signal strength becomes very weak
Solution Approach 1:
The patent applies parameter changes by using an inhomogeneous intensity profile of the laser beam instead of a uniform one. This creates a spatially varying intensity distribution that allows particles at different positions to generate distinguishable signal patterns, enabling accurate particle diameter determination even for particles passing through edge regions where the intensity gradient provides position-encoded information in the signal waveform.
2Illumination intensity
If a particle penetrates the focus of the laser beam, then a reflection with high light intensity is generated, but the signal-to-noise ratio becomes imbalanced due to strong signals
Solution Approach 1:
The patent inverts the conventional approach by intentionally creating an inhomogeneous intensity profile with regions of varying intensity rather than trying to achieve uniform illumination. This inversion allows the system to encode particle position information in the signal waveform's shape and amplitude characteristics, transforming what would be a problem (position-dependent signal variation) into a solution (position-encoded signal patterns that enable accurate diameter measurement).
3Device complexity
If the wavelength of laser light is constant or varies within a narrow band, then the device complexity is reduced, but the accuracy of particle diameter determination decreases due to wavelength-dependent backscatter
Solution Approach 1:
The patent compensates for wavelength-dependent backscatter effects by applying diameter corrections based on the known wavelength characteristics of the laser. The evaluation unit uses the inhomogeneous intensity profile information combined with wavelength-specific backscatter models to calculate accurate particle diameters, thereby maintaining measurement precision without requiring complex wavelength-tuning mechanisms.
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 a more accurate assessment of particle number and size distribution by correcting for wavelength-dependent backscatter and signal-to-noise ratios, improving the precision of particle diameter measurements, especially for small particles.
Implementation Method 1
a laser apparatus (12) having a semiconductor laser (14) which emits a laser light (16) having an inhomogeneous intensity profile
Implementation Method 2
receiving a light reflection (20) of the laser light (16) generated at particles (18) of the particle stream (10)
Implementation Method 3
the backscatter of the laser light depends on the wavelength of the laser light and the particle diameters
Data Source
AI summary
A method for determining a particle distribution in a particle stream (10) using a laser apparatus (12) which has a semiconductor laser (14) that emits a laser light (16) having an inhomogeneous intensity profile (30), characterised byreceiving a light reflection (20) of the laser light (16) generated at particles (18) of the particle stream (10),an evaluation unit (22) connected to the laser apparatus (12) evaluating a reflection signal generated by the light reflection (20) in respect of a frequency distribution of signal strength values which is generated on the basis of the intensity profile (30) when the particles (18) penetrate the laser light (16),a processor unit determining the particle diameters of the individual particles on the basis of the signal strength values,carrying out a diameter correction of at least some of the determined particle diameters on the basis of the sensitivity of the laser apparatus,creating a diameter list of the frequency distribution of the particle diameters,carrying out a frequency correction of the diameter list using a correction list,storing the corrected diameter list on a storage medium.