Optical Particle Sensor Backscattering Geometry for Noise Reduction
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Solution Overview
Problem
Current optical particle sensors have limited sensitivity, particularly for detecting small particles, which are often harmful to health and environment, due to glare from unscattered light rays that overwhelm the photodetectors.
Innovation Solution
The sensor design focuses on collecting primarily backscattered light rays, reducing glare by positioning the emission and detection faces to receive only light rays backscattered by particles, thereby enhancing the signal-to-noise ratio and improving sensitivity for detecting both small and larger particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the sensor collects all scattered light rays including unscattered light, then the total light signal is strong, but the photodetector is dazzled by unscattered light causing high background noise that prevents detection of small particles
Solution Approach 1:
The patent extracts only the useful backscattered light rays from the total light field by positioning the detection face to receive light solely from the backscatter direction. This separates the useful signal (backscattered light carrying particle information) from the harmful unscattered light, eliminating the dazzle effect while maintaining sufficient signal intensity for detecting small particles.
Solution Approach 2:
Instead of detecting light in the forward scattering direction (conventional approach), the patent inverts the detection geometry to collect light from the backscatter direction (opposite to the incident light direction). This inversion allows the detection face to be positioned on the same side as the emission face, receiving only backscattered light and rejecting unscattered light that continues in the forward direction.
2Measurement precision
If the sensor is designed to detect only backscattered light rays, then the signal-to-noise ratio is improved for small particle detection, but the device complexity increases due to specific geometric positioning requirements
Solution Approach 1:
The patent merges the emission face and detection face onto the same side of the sensor, both facing the same direction. This consolidation simplifies the overall device structure compared to conventional designs requiring opposite-side positioning, while still achieving the goal of detecting only backscattered light through the specific angular geometry of the configuration.
3Reliability
If the emission and detection faces are positioned on the same side facing the same direction, then only backscattered light is received improving sensitivity, but the geometric configuration becomes more constrained
Solution Approach 1:
The patent applies local quality by making the photodetector's reception face selectively responsive only to light from the backscatter direction. This directional selectivity at the local level (at the photodetector surface) ensures that only backscattered light carrying particle information is detected, while light from other directions (unscattered light) is automatically rejected, improving detection reliability without requiring complex mechanical constraints.
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 significantly reduces background noise, allowing for more accurate detection of small particles and larger ones, with a weighting favoring the detection of small particles, thus enhancing the sensor's sensitivity and reliability.
Implementation Method 1
If particles are present in the illuminated area, they will absorb part of the light coming from the source and will scatter another part of this light away from the main direction of propagation, according to the diffusion phenomenon.
Implementation Method 2
the at least one source has an emission face facing one side of the sensor and the at least one photodetector has a reception face facing the same side of the sensor, so that the light rays received by the at least one photodetector are light rays backscattered by the at least one particle, for at least 90% of them.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
The invention provides for an optical particle sensor (1) comprising: - at least one light source (2, 2r, 2g, 2b) configured to emit light rays (20), - at least one channel (3) for receiving a fluid carrying at least one particle (30), and for receiving at least part of the light rays (20) emitted by at least one source (2, 2r, 2g, 2b), such that said light rays (20) are partially scattered by at least one particle (30), - at least one photodetector (4) capable of receiving said scattered light rays (20), said sensor (1) being characterized in that at least one source (2, 2r, 2g, 2b) has an emitting face (21) facing one side (D) of the sensor and in that at least one photodetector (4) has a receiving face (41) facing the same side (D) of the sensor (1), such that the light rays received by at least one photodetector are backscattered light rays (20b) by at least one particle (30),for at least 90% of them.