Heatable Glazing Inspection via Shadowgraph Imaging
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Solution Overview
Problem
Current methods for inspecting heatable laminated glazings, such as vehicle windshields with embedded heater wires, face challenges in achieving high spatial resolution and efficiently detecting defective or missing wires, leading to time-consuming raster scanning and inadequate detection of individual wire functionality.
Innovation Solution
A method involving illumination with a light source to produce a shadowgraph image and passing a sufficient electrical current through the heater array to make the wires observable, allowing for rapid inspection and differentiation between active and reference images to identify defects and wire spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal imaging camera is used to inspect heater grid, then temperature distribution can be obtained, but spatial resolution is insufficient and individual heater wires cannot be resolved
Solution Approach 1:
The patent changes the inspection parameter from thermal imaging to optical shadowgraph imaging. By using visible light instead of thermal radiation detection, the system achieves much higher spatial resolution that can resolve individual heater wires embedded in the laminated glazing, directly addressing the resolution limitation of thermal cameras
2Measurement precision
If raster scanning is used to map the entire heated area, then complete coverage is achieved, but inspection time becomes excessively long
Solution Approach 1:
The patent transitions from sequential 1D line-by-line scanning to simultaneous 2D planar imaging. The shadowgraph technique captures the entire heater array pattern in a single optical snapshot, eliminating the time-consuming raster scanning process while maintaining complete inspection coverage
Solution Approach 2:
The patent creates an optical shadow copy of the heater wire pattern that can be captured instantly. This shadowgraph image serves as a permanent record that can be analyzed without re-scanning, replacing the need for repeated mechanical scanning operations
3Use of energy by stationary object
If heater wires are inspected without electrical current, then no power is consumed, but defective or missing wires cannot be distinguished from functional ones
Solution Approach 1:
The patent utilizes optical contrast changes in shadowgraph imaging when electrical current is applied. Functional heater wires that conduct current create visible shadowgraph patterns due to refractive index changes from heating, while defective or missing wires do not produce these patterns, enabling clear differentiation without requiring complex electrical measurements
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
Enables rapid and accurate inspection of heatable glazings by clearly visualizing heater wires in shadowgraph images, reducing the impact of optical effects and allowing for the detection of non-functioning wires and uniform spacing, thereby ensuring effective heating performance.
Implementation Method 1
illuminating the heatable glazing with a light source to produce a shadowgraph image of the heatable glazing
Implementation Method 2
passing a sufficiently high electrical current through the heater array such that the heater wire is observable in the shadowgraph image
Data Source
AI summary
A method of inspecting a heatable glazing is disclosed. A heatable glazing comprises a heater array having at least one heater wire. The method comprises the steps of (i) illuminating the heatable glazing with a light source to produce a shadowgraph image of the heatable glazing; (ii) passing a sufficiently high electrical current through the heater array such that the heater wire is observable in the shadowgraph image of the heatable glazing, such a shadowgraph image of the heatable glazing being referred to as an active shadowgraph image of the heatable glazing; and (iii) capturing the active shadowgraph image of the heatable glazing with an imaging sensor. Apparatus for carrying out the method is also disclosed.