Optical Rain Sensor Layout for Total Internal Reflection
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Solution Overview
Problem
Conventional optical rain sensors in automobiles face inefficiency and reduced sensitivity due to small form factors, leading to a short distance between light emitting and detecting elements and a small angle of incidence, resulting in light refraction rather than reflection, even when the windshield is dry, which affects their accuracy and sensitivity.
Innovation Solution
The optical rain sensor is configured with a hexagram arrangement of light emitting and receiving elements, allowing for a greater distance between activated and deactivated elements, increasing the angle of incidence beyond the critical angle, enabling total internal reflection and improving sensitivity and accuracy by maintaining the same footprint as conventional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rain sensor uses a small form factor to meet size constraints, then the sensor can be compact and easy to install, but the distance between light emitting and detecting elements becomes short and the angle of incidence becomes small, causing light refraction instead of reflection and reducing sensing accuracy
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional hexagram configuration, positioning light emitting and detecting elements at vertices of a hexagonal prism. This spatial arrangement increases the effective distance and angle of incidence while maintaining a compact footprint, enabling total internal reflection and improving measurement precision without increasing overall sensor volume.
Solution Approach 2:
The patent implements dynamic control of the optical configuration by selectively activating different groups of light emitting elements and their corresponding detecting elements. The controller alternates between multiple groups, dynamically adjusting which optical paths are active. This dynamic operation enables the sensor to maintain high measurement precision through optimal path selection while keeping the physical form factor compact.
2Length of moving object
If the angle of incidence is small due to short distance between elements, then the sensor maintains a compact form, but light is refracted into the exterior air instead of being totally reflected, reducing sensing efficiency
Solution Approach 1:
By arranging elements in a three-dimensional hexagram configuration rather than a flat plane, the patent achieves a longer effective optical path length and greater angle of incidence within the same physical footprint. This dimensional transition enables total internal reflection by exceeding the critical angle requirement, thereby reducing energy loss through refraction and improving light reflection efficiency.
Solution Approach 2:
The patent changes the geometric parameters of the optical path by increasing the angle of incidence through the hexagram configuration. This parameter change transforms the optical interaction from refraction-dominant (at small angles) to total internal reflection (at angles exceeding the critical angle), significantly improving light reflection efficiency and reducing energy loss.
3Area of stationary object
If the sensing area is small due to short distance between elements, then the sensor remains compact, but the sensitivity and accuracy of rain detection are reduced
Solution Approach 1:
The hexagram configuration distributes sensing areas across multiple vertices in three-dimensional space, effectively increasing the total sensing area coverage on the windshield. This spatial distribution allows each detecting element to monitor a larger effective area while maintaining compact sensor dimensions, thereby improving both sensitivity and accuracy of rain detection.
Solution Approach 2:
The patent divides the sensing function into multiple segments, with each light emitting-detecting pair monitoring a specific sensing area. The controller integrates signals from multiple segments to achieve comprehensive rain detection. This segmentation allows the sensor to cover a larger total sensing area while maintaining a compact form factor, improving overall measurement precision through multi-point 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 enhances the efficiency and sensitivity of the rain sensor by ensuring total internal reflection and larger sensing areas, allowing for more accurate detection of rain and improved operation of associated automobile systems.
Implementation Method 1
light emitting elements 12a-f (e.g., light emitting diodes) disposed about a periphery of the rain sensor 10
Implementation Method 2
collimating lenses 14a-f adapted to collimate light emitted by the light emitting elements 12a-f
Implementation Method 3
the amount of collimated light that is reflected off of the sensing area of the windshield and received by the light detecting element
Implementation Method 4
focusing lenses 16a-f adapted to receive the collimated light that is reflected off of the windshield and to focus the light
Implementation Method 5
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
Implementation Method 6
If water (e.g., rain) is present at one of the 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 7
increasing the angle of incidence beyond the critical angle, enabling total internal reflection and improving sensitivity and accuracy
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C
AI summary
An optical rain sensor for detecting rainfall on a transparent substrate, the optical rain sensor including a housing disposed on a surface of the transparent substrate, a plurality of photo elements disposed within the housing, each photo element capable of being selectively activated to emit light and deactivated to receive light, and a controller operatively connected to the plurality of photo elements and configured to alternatingly drive the plurality of photo elements between a first mode of operation and a second mode of operation, wherein, in the first mode of operation, at least a first photo element is activated and at least a second photo element is deactivated and, in the second mode of operation, at least the second photo element is activated and at least the first photo element is deactivated.