Shearography Device Spatial Phase Shifting
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Solution Overview
Problem
Conventional interferometric methods for non-destructive material testing using spatial phase shifting require high-power lasers and result in low-quality interferograms due to low light intensity registration, making them inefficient and unreliable for detecting defects, especially under dynamic loading conditions.
Innovation Solution
A shearography device with a modified optical structure that includes a diffraction device and a shear element with fewer than four refractive interfaces, allowing for spatial phase shifting and improved light intensity registration, enabling the separation of background intensity from phase information and reducing the number of required recordings, thus enhancing measurement robustness and simplifying the setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interferometric methods with classic interferometers are used for spatial phase shifting, then interferograms can be obtained, but high-power lasers are required and light intensity registration is low
Solution Approach 1:
The patent changes the optical configuration from classic interferometers (Michelson or Mach-Zehnder) to a shear element-based spatial phase shifting system. This parameter change in the optical path enables more efficient light utilization, allowing high-quality interferograms to be obtained with low-power laser sources by optimizing the interference pattern formation process
Solution Approach 2:
The patent extracts and removes the complex interferometer components (beam splitters, mirrors, phase shifters) from the optical system, replacing them with a simpler shear element configuration. This extraction simplifies the system while maintaining or improving interferogram quality and reducing light loss
2Ease of operation
If classic interferometers with multiple refractions are used, then spatial phase shifting is achieved, but light intensity is significantly reduced
Solution Approach 1:
The patent replaces the mechanical/optical complex system of classic interferometers with a shear element that achieves spatial phase shifting through a simpler optical mechanism. This substitution reduces the number of refractions from multiple interfaces to fewer than four, minimizing light loss while maintaining the spatial phase shifting function
Solution Approach 2:
Instead of using multiple beam splittings and recombining as in classic interferometers, the patent inverts the approach by using a single shear element to create the interference pattern directly, thereby reducing light loss through multiple refractions and improving overall light intensity at the detector
3Measurement precision
If temporal phase shifting methods are used, then material testing can be performed, but at least six recordings are required which reduces productivity
Solution Approach 1:
The patent employs periodic modulation of the shear amount to enable temporal phase shifting with only two recordings instead of six. By periodically varying the shear parameter and capturing images at specific phases of this periodic variation, the system achieves the necessary phase information with reduced measurements, thereby improving productivity
Solution Approach 2:
The patent performs preliminary spatial phase shifting using the shear element before temporal phase shifting is needed. This preliminary action creates an interferogram with embedded phase information that can be extracted more efficiently, reducing the total number of recordings required from six to two while maintaining measurement accuracy
4Measurement precision
If conventional measurement setups are used, then interferograms can be obtained, but the setup is complex and susceptible to interference
Solution Approach 1:
The patent extracts and removes complex components from the conventional interferometer setup, including beam splitters, multiple mirrors, and active phase shifters. The remaining simplified optical path using a shear element maintains interferogram obtainability while significantly reducing device complexity and susceptibility to environmental interference
Solution Approach 2:
The patent merges the functions of multiple separate optical components into a single shear element. This element simultaneously performs beam splitting, beam displacement, and interference pattern creation, thereby simplifying the overall optical structure while maintaining the capability to obtain high-quality interferograms
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
The shearography device achieves high-quality interferograms with low-power laser sources, allowing for real-time acquisition and evaluation of material properties, enabling efficient non-destructive testing and vibration analysis, even under dynamic loading conditions, with increased light yield and reduced susceptibility to interference.
Implementation Method 1
The diffraction device makes it possible to diffract the radiation emitted by the radiation source and reflected via the measurement object
Implementation Method 2
the radiation reflected by the object is refracted on an optical wedge at fewer than four boundary surfaces
Implementation Method 3
Due to the coherent beam source, the beams are superimposed to form an interferogram
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention relates to a shearography device (2) comprising a coherent beam source (6), an optical diffracting unit (12) for diffracting the radiation (8) emitted by the beam source (6) and reflected by a test object (4), and a recording unit (18) for capturing the beam source radiation transmitted by the diffracting unit, a shearing element (14) being positioned between the diffracting unit (12) and the recording unit (18) such that at least one first part of the radiation of the beam source (6) transmitted by the diffracting unit (12) and captured by the recording unit (18) is refracted at fewer than four boundary surfaces of the shearing element (14).