VCSEL Laser Sensor Module with Electro-Optical Modulator for False-Positive Reduction
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Solution Overview
Problem
Laser sensor modules for particle detection are sensitive to macroscopic objects, leading to false-positive particle counts, which interfere with the accurate detection of small particles and particle density.
Innovation Solution
Integration of an electro-optical modulator in the laser sensor module that applies a high-frequency tuning voltage to adjust the optical resonator's refractive index, reducing the detection signal from macroscopic objects and enhancing the module's insensitivity to reflections, thereby improving the accuracy of particle detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the laser sensor module is made sensitive to detect particles at close distances, then particle detection capability is improved, but sensitivity to macroscopic objects increases causing false-positive counts
Solution Approach 1:
The patent applies dynamic tuning of the optical resonator's resonance frequency through an integrated electro-optical modulator. By dynamically adjusting the resonance frequency to track the laser frequency, the system maintains high sensitivity for particle detection while using frequency modulation to distinguish particle signals from macroscopic object reflections, thereby reducing false-positive counts
Solution Approach 2:
The system changes the operational parameters of the optical resonator by applying tuning voltages to the electro-optical modulator. This adjusts the resonance frequency of the cavities to match the laser frequency, enabling selective enhancement of particle detection signals while suppressing unwanted reflections from macroscopic objects through parameter optimization
2Length of stationary object
If the detection range is extended to cover larger distances, then detection coverage is improved, but interference from macroscopic objects increases
Solution Approach 1:
The dynamic frequency tracking mechanism allows the system to extend detection range by adjusting the resonance frequency according to the distance to the target. The electro-optical modulator enables real-time frequency adaptation, maintaining optimal detection conditions across varying distances while using frequency discrimination to filter out macroscopic object interference
Solution Approach 2:
The electro-optical modulator acts as an intermediary between the laser and the optical resonator, mediating the frequency matching process. It enables the system to extend detection range by facilitating resonance conditions at different distances while simultaneously suppressing harmful reflections through controlled frequency offset
3Measurement precision
If the optical resonator is tuned to maximize particle detection signal, then measurement sensitivity is improved, but susceptibility to reflections from macroscopic objects increases
Solution Approach 1:
The system employs periodic modulation of the laser frequency and corresponding tuning of the optical resonator through the electro-optical modulator. This periodic action creates distinct frequency signatures for particle scattering events versus macroscopic object reflections, enabling the system to maximize particle detection sensitivity while filtering out reflection interference through frequency-domain discrimination
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 significantly reduces false-positive particle counts by minimizing the detection signal from macroscopic objects, allowing for reliable measurement of small particle densities and concentrations, while maintaining a high count rate for particles at closer distances.
Implementation Method 1
The electro-optical modulator is arranged to tune a resonance frequency of the optical resonator by means of an electrical tuning voltage applied to the electro-optical modulator
Implementation Method 2
The VCSEL is arranged to emit laser light during operation of the VCSEL upon providing an electrical drive current above a threshold current of the VCSEL
Implementation Method 3
the light detector is arranged to detect an optical response in reaction to the laser light emitted by the VCSEL
Implementation Method 4
The optical response comprises an interference and especially a self-mixing interference signal
Data Source
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AI summary
The invention relates to a laser sensor module for interference based particle detection comprising a Vertical Cavity Surface Emitting Laser (100), an electro-optical modulator (250) and a light detector (200), wherein the Vertical Cavity Surface Emitting Laser (100) comprises a first electrical contact (105), a second electrical contact (135) and an optical resonator, wherein the optical resonator comprises a first distributed Bragg reflector (115), a second distributed Bragg reflector (130) and an active layer (120) arranged between the first distributed Bragg reflector (115) and the second distributed Bragg reflector (130), wherein the Vertical Cavity Surface Emitting Laser (100) is arranged to emit laser light (315) during operation of the Vertical Cavity Surface Emitting Laser (100), wherein the electro- optical modulator (250) is integrated in the optical resonator, wherein the electro-optical modulator (250) is arranged to tune a resonance frequency of the optical resonator by means of an electrical tuning voltage applied to the electro-optical modulator (250), wherein the light detector (200) is arranged to detect an optical response in reaction to the laser light (315) emitted by the Vertical Cavity Surface Emitting Laser (100) and scattered or reflected back into the Vertical Cavity Surface Emitting Laser (100), wherein the tuning voltage is arranged such that a detection signal received by the light detector (200), which is caused by a macroscopic object (25) positioned in a range between a threshold distance and a detection range of the particle sensor module, is reduced, when the tuning voltage is provided, in comparison to a detection signal caused by the macroscopic object (25) at the same position, when the tuning voltage is not provided. The invention further relates to a corresponding laser sensor (300), a particle detector comprising such a laser sensor (300), a mobile communication device comprising such a particle detector or laser sensor (300) and a corresponding method of particle detection.