Optical Rain Sensor Using Y-Pattern LEDs and Triangular Photodiodes
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Solution Overview
Problem
Conventional optical rain sensors have limited sensitivity and are capable of detecting moisture at only six discrete sensing areas, which restricts their effectiveness in accurately determining the presence of rain on an automobile windshield.
Innovation Solution
The optical rain sensor employs a configuration of four light emitting elements arranged in a 'Y' pattern and three light detecting elements in a concentric, rotationally offset triangular pattern on a printed circuit board, alternating between modes of operation to emit light beams towards the detecting elements, allowing for detection of moisture at nine evenly distributed sensing areas, thereby enhancing sensitivity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical rain sensors use six light emitting elements and one light detecting element, then the sensor can detect moisture at six discrete sensing areas, but the sensitivity and measurement precision are limited
Solution Approach 1:
The patent combines multiple light detecting elements (three photodiodes arranged in a triangular pattern) to receive light from multiple light emitting elements (four LEDs in a Y-pattern). This merging of detection capabilities allows the sensor to monitor nine sensing areas simultaneously, improving measurement precision without proportionally increasing device complexity. The shared light path and integrated detector array enable efficient use of optical components.
Solution Approach 2:
The patent transitions from a conventional linear or grid arrangement to a triangular geometric configuration for both light emitting and detecting elements. The light detecting elements are positioned at corners of an imaginary equilateral triangle, creating three-dimensional spatial distribution that enables detection at nine discrete sensing areas. This dimensional reorganization improves coverage and sensitivity without requiring a proportional increase in component count.
2Measurement precision
If the sensor uses more light emitting and detecting elements to increase sensing areas, then measurement precision improves, but manufacturing cost and device complexity increase
Solution Approach 1:
The light detecting elements serve multiple functions: each photodiode receives light from multiple light emitting elements and contributes to detection across multiple sensing areas. The three light detecting elements collectively monitor all nine sensing areas by receiving reflected light from different paths. This multi-functionality allows the sensor to achieve enhanced sensing coverage without requiring a separate detector for each sensing area, thereby controlling manufacturing costs.
Solution Approach 2:
The sensor employs alternating activation of light emitting elements in groups, where different combinations of LEDs are activated at different times. This dynamic operation allows the same physical components to sequentially cover different sensing areas, effectively multiplying the sensing capacity without adding permanent hardware. The controller alternates between different light emitting element configurations to achieve comprehensive monitoring.
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 configuration enables the rain sensor to detect moisture at nine discrete sensing areas, providing greater sensitivity and efficiency while maintaining a similar cost and form factor to conventional sensors, effectively influencing the operation of automobile systems like windshield wipers.
Implementation Method 1
six light emitting elements 12a-f (e.g., light emitting diodes) disposed about a periphery of the rain sensor 10
Implementation Method 2
a portion of collimated light that strikes the sensing area will be refracted into the water instead of being reflected to a respective focusing lens
Implementation Method 3
If water (e.g., rain) is present at one of the six sensing areas 15a-f on the exterior of the windshield, a portion of collimated light that strikes the sensing area will be refracted into the water instead of being reflected to a respective focusing lens
Implementation Method 4
a light detecting element 17 (e.g., a photodiode) located at the center of the rain sensor 10 that is adapted to receive the focused light from the focusing lenses 16a-f and to convert the received light into an electrical output signal
Data Source
AI summary
An optical rain sensor including a plurality of light detecting elements and a plurality of peripheral light emitting elements disposed on a printed circuit board (PCB) and surrounding a central light emitting element disposed on the PCB, wherein, in a first mode of operation, the central light emitting element is configured to emit light beams toward the plurality of light detecting elements, and wherein, in a second mode of operation, each of the peripheral light emitting elements is configured to emit light beams toward the plurality of light detecting elements.