Optical Rain Sensor Minimal Drop Radius Detection
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Solution Overview
Problem
Existing rain sensors are not sufficiently accurate in determining driver visibility during rainfall, and they often lack robustness and economic viability for effective control of windshield wipers.
Innovation Solution
A rain sensor system comprising multiple emitters and rain-sensitive areas arranged in a linear or quadratic array, utilizing radiation focusing and optical coupling to efficiently detect minimal rain drop sizes by analyzing changes in optical signals, with equations derived from geometric relationships to calculate the minimal rain drop radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional rain sensors use total internal reflection with a single emitter and receiver, then the device structure is simple, but the measurement precision for minimal rain drop sizes is insufficient
Solution Approach 1:
The patent divides the sensing area into multiple rain-sensitive areas (first, second, third areas) arranged in a linear or quadratic pattern. Each area is illuminated by emitters at specific angles, allowing the system to detect raindrops of different sizes by analyzing which areas are affected. This segmentation enables precise measurement of minimal rain drop sizes while maintaining a manageable device structure.
Solution Approach 2:
The patent introduces angular dimension by positioning emitters at different angles (e.g., 45°, 60°) relative to the pane surface. This angular arrangement creates multiple illumination paths that intersect the pane at different locations, enabling the system to differentiate raindrop sizes based on which angular paths are blocked. This adds a dimensional aspect to detection without significantly complicating the overall device structure.
2Measurement precision
If multiple emitters and rain-sensitive areas are used to improve detection accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent designs the system so that multiple emitters and rain-sensitive areas serve multiple functions simultaneously. The same emitters illuminate multiple different rain-sensitive areas at different angles, and each rain-sensitive area can detect raindrops of various sizes depending on the illumination angle. This multi-functionality allows accurate driver visibility determination without proportionally increasing device complexity.
Solution Approach 2:
The patent combines multiple detection functions into a unified system where emitters, panes, and receivers work together as an integrated whole. The linear or quadratic arrangement of rain-sensitive areas allows the system to process information from multiple angles and locations simultaneously, merging what would otherwise be separate detection systems into a single coherent device with improved precision.
3Reliability
If traditional sensors detect rain intensity based on signal loss, then the detection method is simple, but the reliability for assessing driver visibility is insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the receiver detects optical signals from multiple emitters illuminating multiple rain-sensitive areas, and this information is fed back to an evaluation device. The evaluation device uses predetermined evaluation criteria based on the pattern of signal losses across different areas and angles to reliably assess driver visibility. This feedback loop transforms simple signal detection into a reliable visibility assessment system.
Solution Approach 2:
The patent changes the detection parameter from simple signal loss magnitude to the spatial pattern of signal loss across multiple rain-sensitive areas. By analyzing which specific areas (first, second, third areas) experience signal loss and at what angles, the system can distinguish between raindrops of different sizes and their impact on driver visibility. This parameter transformation significantly improves reliability without requiring overly complex evaluation systems.
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 system provides enhanced accuracy and robustness in determining driver visibility by precisely measuring minimal rain drop sizes, improving the control of windshield wipers and being economically viable.
Implementation Method 1
utilizing radiation focusing and optical coupling to efficiently detect minimal rain drop sizes
Implementation Method 2
The rain sensor further comprises a radiation focusing means for guiding the electromagnetic radiation and an optical coupling to be arranged between the pane and the optical focusing means
Data Source
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AI summary
The present invention relates to a rain sensor detecting the size of rain drops (115) based on optical effects. The rain sensor is mounted on a first surface (102) of a pane (100) in order to detect the amount of moisture (115) on an opposing second surface (104) of the pane (100), the rain sensor comprising: at least one emitter (110) for emitting electromagnetic radiation, directed from the first surface (102) to the second surface (104) to form at least two rain-sensitive areas (118) on the second surface (104), at least one receiver (112) for sensing radiation emitted by the emitter and that has been internally reflected at the rain-sensitive areas (118), and for generating an output signal indicative of an amount of moisture (115) on the rain-sensitive area (118), and a control unit (120) that calculates a minimal droplet size based on the output signal.