Optical Raindrop Detection Device for Immediate Small Rainfall Sensitivity

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Solution Overview

Problem

Conventional raindrop detection methods, such as tipping bucket rain gauges and droplet sensors, face challenges in accurately detecting small amounts of rainfall and delayed detection of rainfall onset.

Innovation Solution

A raindrop detection device comprising a light source unit, a light receiving unit, a raindrop detection unit, and a control unit, which detects raindrops based on the change in light reception due to passing raindrops, allowing for accurate detection of small rainfall amounts from the start of rainfall.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a tipping bucket rain gauge is used, then rainfall measurement is continuous and accurate for large rainfall values, but small amounts of rainfall (less than 0.5 mm) cannot be detected and detection is delayed

Engineering Contradiction:

Improvedetection sensitivityVSAvoiddetection delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical tipping bucket system with an optical detection system consisting of a light source, light receiving unit, and raindrop detection unit. This optical system detects individual raindrops by measuring light blockage, enabling continuous detection from the moment rain begins without the 0.5 mm threshold limitation of mechanical systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from mechanical bucket tipping (requiring 0.5 mm accumulation) to optical light blockage measurement. By detecting the presence of raindrops through light attenuation rather than accumulated volume, the system achieves immediate detection sensitivity for small rainfall amounts while maintaining continuous measurement capability.

Inventive Principle:

Principle #35Parameter changes

2Loss of time

If a droplet sensor is used, then detection response is fast from the start of rainfall, but accurate measurement of rainfall amount is difficult

Engineering Contradiction:

Improvedetection speedVSAvoidrainfall amount measurement accuracy

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The patent uses an optical measurement system rather than mechanical or simple optical sensors. By quantifying the degree of light blockage caused by raindrops and integrating this data, the system achieves both fast detection response and accurate rainfall amount measurement, resolving the trade-off between speed and precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system continuously monitors light blockage changes and processes this feedback signal to detect raindrops in real-time. The control unit processes the optical signals to determine both the presence of raindrops and the total rainfall amount, enabling simultaneous achievement of fast detection and accurate measurement through continuous feedback processing.

Inventive Principle:

Principle #23Feedback

3Illumination intensity

If ambient light is present during optical detection, then the light receiving unit receives additional light, but this interferes with accurate raindrop detection

Engineering Contradiction:

Improvelight reception levelVSAvoiddetection accuracy

Core Design Contradiction:

Illumination intensityVSMeasurement precision

Solution Approach 1:

The light source unit operates in a periodic on-off pattern rather than continuously. By alternating between light emission and darkness, the system creates distinct temporal signatures that allow the control unit to differentiate between light caused by the light source and ambient light, eliminating interference while maintaining detection capability.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The control unit performs preliminary processing by storing reference data about light reception patterns during light source operation. This baseline information is used to distinguish actual raindrop-induced light blockage from variations caused by ambient lighting conditions, ensuring accurate detection regardless of environmental light levels.

Inventive Principle:

Principle #10Preliminary action

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 device enables accurate detection of even small amounts of rainfall from the beginning of rainfall, improving upon the limitations of conventional methods by enhancing sensitivity and detection speed.

Implementation Method 1

detects raindrops that have passed through a raindrop detection area according to a change in an amount of received light

Methodology Applied

Scientific EffectLight blockage: Absorption (EM radiation)

Data Source

PatentUS12292546B2Raindrop detection device, raindrop detection method, and raindrop detection program

Publication Date: 2025.05.06 OMRON CORP

AI summary

A raindrop detection device 10 includes an LED 11, a photodiode 14, a microprocessor 20, and an LED flashing circuit 22. The LED 11 emits light in a specific direction. The photodiode 14 is disposed at a position opposite the LED 11 and receives light emitted from the LED 11. The microprocessor 20 detects raindrops that have passed between the LED 11 and the photodiode 14, according to the change in the amount of light received by the photodiode 14. The LED flashing circuit 22 controls the on and off switching of light emitted from the LED 11.