Rain Sensor Optical Inversion for Windshield Reflection Noise
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Solution Overview
Problem
Conventional rain sensors face challenges such as complex optical systems, degraded signal-to-noise ratio due to windshield reflection, narrow sensing areas, and interference from ambient light and wiper motion, limiting their effectiveness in accurately determining rainfall levels.
Innovation Solution
A rain sensor with a simplified optical system featuring a lattice-like arrangement of infrared LEDs and sensors inclined relative to the windshield, using a modulated light source and infrared filter to minimize ambient light effects and exclude noise from windshield reflections, allowing for efficient raindrop detection over a wide area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light source and light receiving element are arranged on opposite sides of the windshield to use internal light guiding phenomenon, then the rain sensing function is achieved, but the optical system becomes complicated and mounting becomes difficult
Solution Approach 1:
Instead of transmitting light through the windshield from one side to the other (conventional method), the patent inverts the approach by placing both the light source and light receiving element on the same side of the windshield. The light source emits light that reflects off raindrops on the windshield surface, and the light receiving element detects this reflected light. This inversion eliminates the need for complex optical coupling and precise angle maintenance while achieving reliable rain sensing.
2Reliability
If the light receiving element is installed on the opposite side of the light source to detect reflected light from raindrops, then the rain sensing is achieved, but the signal-to-noise ratio is degraded due to windshield surface reflection
Solution Approach 1:
The patent applies local quality by configuring the light receiving element with a specific directional sensitivity that matches the reflection angle of raindrops. The light source and light receiving element are positioned at specific angles relative to the windshield surface, creating a localized sensing zone where only light reflected from raindrops at specific angles can reach the sensor. This directional configuration filters out ambient light and windshield surface reflections, significantly improving the signal-to-noise ratio.
3Measurement precision
If light sources and light receiving elements are serially arranged to reduce ambient light interference, then the sensing precision is improved, but the sensing area becomes narrow and small
Solution Approach 1:
The patent transitions from a one-dimensional serial arrangement to a two-dimensional array configuration. Multiple light source and light receiving element sets are arranged in a grid pattern on the windshield, with each set covering a specific local area. This dimensional expansion allows the system to maintain high sensing precision locally while achieving wide-area coverage globally, solving the contradiction between precision and coverage.
4Area of stationary object
If multiple light source and light receiving element sets are arranged to cover a wide area, then the sensing area is expanded, but the device complexity and mounting difficulty increase
Solution Approach 1:
The patent divides the windshield into multiple sensing zones, each covered by a separate light source and light receiving element set. Each set operates independently as a modular unit, and the overall sensing coverage is achieved by combining these segmented zones. This segmentation allows for flexible configuration, easier mounting, and simplified replacement or maintenance of individual units while maintaining wide-area coverage.
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 enhances raindrop sensing efficiency by reducing noise from windshield reflections and ambient light, enabling precise control of wiper operation and improving reliability by focusing on reflected light from raindrops alone.
Implementation Method 1
receiving the amount of the light reflected towards the light source from the raindrops fallen on the windshield
Implementation Method 2
infrared filter installed in the opening formed at the one side of the housing (1) of the rain sensor
Implementation Method 3
a receiver (9) excluding noise components caused by the reflection from the surface of the windshield (2) and extracting only the modulated frequency component of the optical signal
Data Source
AI summary
During rain, including a light source (5) for radiating light such that the light is transmitted through a vehicle window (2), a light receiving element (6) for sensing an optical signal when the light radiated from the light source (5) is reflected from the raindrop fallen on the vehicle window (2) and performing a photoelectric transduction, and a receiver (9) for receiving the photoelectrically transduced signal from the light receiving element (6) and judging the level of rainfall. The light source (5) and the light receiving element (6) are inclined with respect to the surface of the vehicle window (2) such that the light of the light source (5) directly reflected from the vehicle window (2) exits to the outside of the light receiving element (6) and the light reflected from a raindrop (8) on the vehicle window (2) is received by the light receiving element (6) to operate a vehicle wiper.