Retro-reflective surface treatment for interferometric deformation measurement
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Solution Overview
Problem
Conventional holographic or speckle testing (HOST) systems require high power illumination lasers and are restricted to short distances due to low illumination efficiency caused by the angular mismatch between diffuse reflection and receiving optics, limiting their effectiveness in measuring surface deformations of arbitrarily shaped objects.
Innovation Solution
The implementation of a retro-reflective surface treatment on the object under test, using elements like cube corners and dielectric spheres, which retro-reflect light within a controlled angle, enhancing the optical signal received by the interferometer and allowing for more efficient measurement without the need for high power lasers or short distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If diffuse reflection is used for holographic or speckle testing, then the object surface has no predetermined shape restriction, but the illumination efficiency is very low due to angular mismatch between scattered light and receiving optics
Solution Approach 1:
A retro-reflective surface treatment is introduced as an intermediary between the object surface and the receiving optics. This treatment includes retro-reflective elements (such as cube corners or dielectric spheres) that redirect light back toward the source direction, effectively bridging the angular mismatch between diffuse reflection and the receiving optics, thereby significantly improving illumination efficiency while maintaining surface shape flexibility
Solution Approach 2:
The optical properties of the object surface are modified by applying a retro-reflective surface treatment. This changes the light scattering characteristics from purely diffuse reflection to a combination of diffuse reflection and retro-reflection, altering the angular distribution of reflected light to better match the receiving optics and improve illumination efficiency
2Adaptability or versatility
If conventional HOST systems use diffuse reflection, then they can measure arbitrarily shaped objects, but they require high power illumination lasers and are restricted to short distances
Solution Approach 1:
The retro-reflective surface treatment acts as an intermediary that enhances the optical signal return to the interferometer. By redirecting light back toward the source direction, it compensates for the energy loss over distance, enabling accurate measurements at longer distances without requiring high power lasers
Solution Approach 2:
The patent replaces the need for high power illumination lasers with a retro-reflective surface treatment that passively enhances the optical signal. Instead of increasing the source power mechanically, the system uses optical geometry (retro-reflection) to improve signal return, thereby enabling long-distance measurements with standard laser power levels
3Illumination intensity
If retro-reflective surface treatment is applied, then the optical signal received by the interferometer is significantly increased, but the surface treatment adds complexity to the object
Solution Approach 1:
The retro-reflective surface treatment is applied locally to the object surface rather than requiring modification of the entire object. The retro-reflective elements (cube corners, dielectric spheres, or other retro-reflective materials) are applied only to the measurement areas, providing localized enhancement of optical signal intensity without adding complexity to the rest of the object
Solution Approach 2:
The retro-reflective surface treatment can be applied using simple, inexpensive materials such as retro-reflective tape, spray-applied retro-reflective coatings, or adhesive-mounted retro-reflective elements. These treatments are designed to be easily applied and removed without permanent modification to the object, reducing the complexity and cost of the measurement system
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 approach significantly increases the optical signal received by the interferometer, enabling accurate and efficient measurement of surface deformations over longer distances without the need for high power lasers, thus overcoming the limitations of conventional HOST systems.
Implementation Method 1
a surface treatment disposed on the surface of the object for providing a retro-reflective patina... The retro-reflective patina is configured to substantially retro-reflect the illumination from the surface of the object
Implementation Method 2
An objective lens is disposed between the interferometer and the surface treatment for producing a speckle image of at least a portion of the surface of the object... The grainy appearance is an interference phenomenon know as speckle
Data Source
AI summary
A system for measuring deformation of at least one surface of an object including an interferometer for receiving illumination reflected from the surface of the object, and a surface treatment disposed on the surface of the object for providing a retro-reflective patina. The retro-reflective patina is configured to reflect the illumination from the surface of the object. The retro-reflective patina is attached to the surface of the object and may include a plurality of cube corners, or a plurality of dielectric spheres, or a combination of cube corners and dielectric spheres. Impinging light onto the object is provided by an optical source that may be separate from or integral to the interferometer. The impinging light may be directed toward the object through an objective lens, which is also used for receiving the illumination from the object. Alternatively, the impinging light may be directed toward the object by first bypassing the objective lens.