Windshield Camera Heating Laminate With Low Optical Distortion
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Solution Overview
Problem
The existing laminated automotive glazing systems experience thermal distortion due to the shift in the index of refraction of the polymer interlayer during heating, which delays the clearing of snow and ice from the camera field of view, affecting the performance and safety of camera-based safety systems.
Innovation Solution
Replacing the polymer interlayer in the camera field of view with a temperature-stable interlayer that maintains a stable index of refraction within the operating temperature range of the heated circuit, reducing distortion and facilitating faster vehicle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polymer interlayer is used in the camera field of view, then the laminate provides adequate bonding and flexibility, but the index of refraction shifts during heating causing thermal distortion
Solution Approach 1:
The patent applies different interlayer materials to different regions of the windshield. Specifically, a first interlayer material is used in the camera field of view area where index of refraction stability is critical, while a second interlayer material may be used in other areas. This local differentiation resolves the contradiction by providing thermal stability where needed without compromising overall laminate performance.
Solution Approach 2:
The patent employs composite interlayer structures, combining materials with different properties. The first interlayer material in the camera field of view is selected specifically for its thermal stability and consistent index of refraction, while other materials may be used in non-critical areas. This composite approach allows the system to achieve both bonding flexibility and optical stability simultaneously.
2Productivity
If the heating circuit power density is increased to clear snow and ice rapidly, then the clearing speed improves, but the thermal distortion increases due to polymer interlayer heating
Solution Approach 1:
The patent localizes the thermal stability property to the camera field of view region by using a first interlayer material specifically in that area. This allows the rest of the windshield to be heated at higher temperatures for rapid clearing, while the camera region maintains optical stability even during high-power heating operations.
Solution Approach 2:
The patent changes the material parameter (index of refraction temperature coefficient) in the camera field of view area by selecting a first interlayer material with superior thermal stability. This parameter change enables the system to operate at higher heating power densities without experiencing distortion in the critical camera region, thus improving clearing speed without sacrificing optical quality.
3Power
If embedded wire heating circuits are used with small separation distance, then the heating efficiency improves, but the camera field of view must be small to avoid encroachment
Solution Approach 1:
The patent applies a specific interlayer material with optimized optical and thermal properties in the camera field of view area. This local quality enhancement allows the use of high-power heating circuits with small separation distances without compromising the camera's ability to capture a wide field of view, as the heated area can extend closer to the camera while maintaining optical clarity.
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 solution reduces thermal distortion, enables shorter drive-away times, and supports higher-resolution camera systems while being fabricated using standard automotive glass processes and equipment.
Implementation Method 1
resistive heating circuit that is formed by embedding fine wires into the plastic bonding layer
Implementation Method 2
The wires are embedded using an oscillating sinusoidal like pattern to reduce glare that can occur under certain lighting conditions
Data Source
AI summary
The use of camera-based safety systems is growing at a rapid rate in automobiles where they are used to provide lane departure warning, collision avoidance, adaptive cruise control and other functions. As the industry moves towards full autonomous capability, the number of cameras and the resolution are increasing. For proper operation, the cameras require a clear undistorted field of view. Keeping the camera area free of snow and ice has been a problem. A resistive heating circuit is typically used to keep the area clear. For rapid clearing the circuit needs to operate at a high-power level. Due to the temperature dependent index of refraction of the plastic interlayer, severe distortion can result from the non-isothermal heating resulting from the spacing of the circuit elements. The laminate of the invention reduces distortion by removing the interlayer in the camera field of view and replacing with a plastic having a more temperature stable index of refraction.