Laser Sensor Module Soiling Detection via Mechanical Excitation
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Solution Overview
Problem
Laser sensor modules face reduced reliability and accuracy in measuring particle densities due to soiling of the emission window, which causes transmission losses and scattering of laser light, making it difficult to detect soiling using interference or self-mixing interference signals.
Innovation Solution
A laser sensor module with a mechanically decoupled emission window that generates an indication signal based on self-mixing interference signals during mechanical excitation, allowing for the detection and quantification of soiling, enabling correction of measured particle densities and providing a user indication of the module's readiness for use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the emission window is fixed and integrated with the laser and detector, then the device structure is simple, but soiling of the window cannot be detected
Solution Approach 1:
The emission window is mechanically decoupled from the laser and detector assembly, separating it into an independently movable component. This segmentation allows the window to be excited mechanically while the laser and detector remain stationary, enabling detection of soiling through relative movement-induced interference signal changes.
Solution Approach 2:
The emission window is subjected to mechanical excitation (vibration) to induce relative movement between the window and the laser/detector assembly. This mechanical vibration causes the interference signal to modulate when soiling is present on the window, providing a detectable indication of soiling condition.
2Measurement precision
If interference signals are used to detect soiling, then soiling detection is enabled, but the detection accuracy is reduced due to scattering of laser light
Solution Approach 1:
The patent replaces direct optical detection of soiling (which is affected by light scattering) with a mechanical excitation approach. By mechanically vibrating the emission window and detecting changes in the interference signal caused by this mechanical movement, the system bypasses the limitations of direct optical scattering detection and achieves more accurate soiling detection.
Solution Approach 2:
The mechanical excitation of the emission window serves as an intermediary mechanism to translate the presence of soiling into detectable interference signal changes. Instead of directly detecting scattered light, the system uses mechanical vibration to modulate the optical path, with the interference signal acting as an intermediary that reveals soiling information more accurately.
3Reliability
If the emission window is mechanically excited, then soiling can be detected through interference signal changes, but the device requires additional mechanical components
Solution Approach 1:
The emission window serves multiple functions: it protects the internal optical components, transmits laser light for particle detection, and acts as a mechanically excitable element for soiling detection. This multi-functionality reduces the need for separate dedicated soiling detection components, thereby limiting the increase in device 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
The solution effectively detects and quantifies soiling of the emission window, allowing for accurate correction of particle density measurements and informing users of the module's reliability, thereby maintaining the sensor's effectiveness in measuring particle densities.
Implementation Method 1
The detector is arranged to determine an interference signal. The interference signal is preferably a self-mixing interference signal of an optical wave within a laser cavity of the laser.
Implementation Method 2
an optical arrangement for focusing the laser beam to a focus region
Implementation Method 3
The interference signal or self-mixing interference signal may be generated by laser light of the laser beam reflected by at least one of the particles.
Implementation Method 4
soiling of the emission window, which causes transmission losses and scattering of laser light
Data Source
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Figure 3~4
AI summary
The invention describes a laser sensor module (100) for measuring a particle density of particles (10) with a size of less than 20 μ m, preferably less than 10 μ m in a fluid, wherein the laser sensor module (100) comprises a laser (111), a detector (121) and an optical arrangement (140) for focusing the laser beam to a focus region, wherein the laser (111) is arranged to emit a laser beam (112) through the optical arrangement (140) to the focus region, wherein the optical arrangement comprises an emission window, wherein the detector (121) is arranged to determine an interference signal, wherein the laser sensor module (100) is arranged to provide an indication signal of a soiling of the emission window (145) based on an interference signal determined during a mechanical excitation of the emission window (145), a corresponding method of testing a soiling of the emission window, and computer program product.