Coaxial Optical Interferometry for Real-Time Defect Visualization
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Solution Overview
Problem
Current optical interferometry techniques for non-destructive testing and vibration analysis, such as TV holography and electronic shearography, require complex alignment and separate monitoring, making it difficult for operators to accurately identify and interact with defects on objects, especially when surface gradients and motions are involved.
Innovation Solution
A method and system that uses optical interferometry to determine surface position, gradient, or motion, and projects an image onto the object based on this information, allowing real-time feedback and alignment without the need for complex transformations, using a co-axial projection system with a common objective lens and light-directing component to ensure accurate alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical interferometry is used to determine surface position, gradient, or motion, then measurement precision is improved, but device complexity increases due to complex alignment requirements
Solution Approach 1:
The patent combines the interferometry measurement system with an image projection system sharing a common optical path and objective lens. The projection system and interferometry system are merged into a single integrated apparatus, eliminating the need for separate monitoring displays and reducing alignment complexity between independent systems.
Solution Approach 2:
The common objective lens serves dual functions: it collects light for interferometry measurement and projects images onto the object surface. This multi-functional design reduces the number of optical components and simplifies the overall system architecture while maintaining measurement precision.
2Loss of information
If interferometry analysis data is displayed on a separate computer monitor, then information is provided to operators, but ease of operation deteriorates due to difficulty in identifying exact defect locations on the object
Solution Approach 1:
Instead of displaying defect information on a separate monitor, the patent projects an optical image directly onto the object surface that visually represents the interferometry analysis data. This optical copy of the defect information is superimposed on the actual object, allowing operators to see both the object and defect locations simultaneously without looking away at a separate display.
Solution Approach 2:
The projected image uses color or intensity variations to encode defect information, such as different colors representing different defect types or severity levels. This visual encoding allows operators to quickly identify and locate defects on the object surface through color cues rather than interpreting monochrome interferometry patterns.
3Productivity
If real-time projection is implemented, then productivity is improved through immediate feedback, but device complexity increases due to simultaneous operation requirements
Solution Approach 1:
The system operates continuously with the interferometry measurement and image projection occurring simultaneously in real-time. The projection system continuously updates the defect information on the object surface as new measurement data becomes available, eliminating interruptions and maintaining continuous productive action throughout the inspection process.
Solution Approach 2:
The projected image provides immediate visual feedback to operators about defect locations and characteristics directly on the object surface. This real-time feedback loop allows operators to instantly identify and respond to defects without waiting for separate analysis or interpretation of interferometry data, significantly improving inspection productivity.
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 operators to directly visualize and interact with defects on the object, providing immediate feedback and overcoming challenges in aligning interferometry analysis data with the object's surface, especially on uneven surfaces, by projecting relevant information directly onto the object, enhancing defect identification and interaction.
Implementation Method 1
uses an electronic image sensor to record successive frames of an interference pattern created by (i) a reference beam from a coherent light source like a laser and (ii) coherent light that has been scattered by an object
Implementation Method 2
a reference beam from a coherent light source like a laser
Implementation Method 3
coherent light that has been scattered by an object, which may be vibrating or otherwise changing shape
Data Source
AI summary
An optical interferometer (1) is used to determine information about the position, gradient or motion of a surface of an object (2) at each of a plurality of points on the surface. An image is projected onto the surface of the object (2), such that, for each of the plurality of points, the intensity or spectrum of the projected image at that point depends on the determined information about the position, gradient or motion of the surface at that point.