Shearogram Generation for Moving Platforms
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Solution Overview
Problem
Current shearography systems are inefficient in resolving the phase of acousto-seismic signals and require high power laser sources, making them impractical for aircraft and fast-moving platforms that need large area coverage rates for detecting buried objects or subsurface anomalies.
Innovation Solution
A method and system that generate phase-resolved shearograms by high-pass filtering and co-registering specklegram images, using a processing unit to align speckle patterns and produce shearogram images for detecting surface changes, which can be used to detect buried objects or subsurface structures from moving platforms like aircraft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If non-phase resolved shearography is used, then high power laser sources can be employed, but the system cannot resolve the phase of acousto-seismic signals and is impractical for fast moving platforms
Solution Approach 1:
The system performs preliminary co-registration of speckle patterns from multiple specklegrams before generating shearograms. This pre-alignment step enables the system to process data from fast-moving platforms by compensating for motion effects in advance, allowing phase resolution to be achieved without sacrificing area coverage rate
Solution Approach 2:
The invention implements a dynamic co-registration process that adapts to the motion characteristics of fast-moving platforms. The speckle pattern alignment algorithm dynamically adjusts to platform movement, enabling continuous phase measurement while maintaining high area coverage rates that would be impossible with static shearography systems
2Measurement precision
If traditional shearography is used, then surface deformation can be measured, but the system is inefficient for remote sensing of small-scale acousto-seismic vibrations
Solution Approach 1:
The system creates multiple copies of the speckle pattern from different specklegrams and co-registers them to reconstruct phase information. By copying and aligning speckle patterns from multiple temporal instances, the system enhances vibration detection capability while managing complexity through algorithmic processing rather than additional hardware
Solution Approach 2:
The invention segments the complex task of vibration detection into distinct processing steps: specklegram acquisition, high-pass filtering, co-registration, and shearogram generation. This segmentation allows each step to be optimized independently, improving small-scale vibration detection while keeping overall system complexity manageable
3Measurement precision
If specklegram images are co-registered to align speckle patterns, then phase resolved shearograms can be generated, but processing time and computational complexity increase
Solution Approach 1:
High-pass filtering is applied to specklegram images before co-registration to remove low-frequency background variations. This preliminary filtering step simplifies the subsequent co-registration process by focusing computational effort on aligning the high-frequency speckle patterns, thereby reducing overall processing time while maintaining phase information accuracy
Solution Approach 2:
The co-registration process focuses specifically on aligning speckle patterns in regions of interest rather than processing entire images uniformly. This partial action approach concentrates computational resources where they are most needed for phase measurement, reducing unnecessary processing time while preserving measurement precision
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 remote sensing of full phase and amplitude information of small-scale acousto-seismic vibrations, improving detection capabilities for buried objects and subsurface structures with enhanced area coverage rates and safety, even from moving platforms.
Implementation Method 1
high pass filtering the specklegram images
Implementation Method 2
co-registering the specklegram images to produce a co-registered specklegram set such that speckle patterns in the plurality of co-registered specklegram images are aligned with one another
Implementation Method 3
a shearing interferometer is able to detect extremely small (sub-micrometer) changes in surface out-of-plane deformation
Implementation Method 4
Shearography is an optical, Non-Destructive Testing (NDT) technique that provides fast and accurate indications about internal material discontinuities or anomalies
Data Source
AI summary
A system and method are presented for generating shearograms from raw specklegram images which may, for example, be collected from airborne or other mobile shearography equipment. The system and method is used to detect and characterize buried mines, improvised explosive devices (IEDs), and underground tunnels, bunkers, and other structures. Amongst other purposes, the system and method may also be used for rapid scanning of ship hulls and aircraft for hidden structural defects, rapid pipeline inspection, and non-contact acoustic sensing for in-water and underground sources.