Double-Mirror Shear Interferometer for Compact Optical Measurement
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Solution Overview
Problem
Existing shearography measurement systems are complex, expensive, sensitive to environmental influences, and inflexible, requiring high-powered lasers and complex stabilization, making them unsuitable for industrial applications.
Innovation Solution
A measuring arrangement using a diaphragm and a double-mirror setup where the light beam is split directly into two partial beams by a partially transparent and a full mirror, allowing interference in a camera without beam splitters, enabling spatial phase shifting and reducing the optical path, thus minimizing shadowing and using low-powered lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Mach-Zehnder interferometer with beam splitters is used, then interferometry can be achieved, but the construction becomes complex and expensive
Solution Approach 1:
The patent removes the beam splitter components from the traditional Mach-Zehnder interferometer setup. Instead of using beam splitters to divide and recombine light paths, the invention uses a direct reflection setup where light is split into two paths by reflecting off two separate mirrors, eliminating the need for complex beam splitter assemblies and reducing overall system complexity while maintaining interferometric functionality.
Solution Approach 2:
The patent combines the light splitting and recombination functions into a simpler mirror arrangement. The two mirrors are positioned to reflect light paths that naturally converge on the camera sensor, merging the functions of multiple separate optical components (beam splitters, mirrors, and recombination elements) into a more compact and simpler dual-mirror configuration.
2Measurement precision
If traditional shearography systems are used, then measurement sensitivity can be achieved, but sensitivity to environmental influences increases
Solution Approach 1:
The patent replaces complex mechanical stabilization systems with a simpler optical design that is inherently less sensitive to environmental factors. By eliminating the need for vibration-insulated tables and complex alignment mechanisms, the system achieves measurement stability through its simplified optical path and direct reflection geometry, which are less susceptible to environmental disturbances.
3Measurement precision
If powerful lasers are used, then measurement capability is sufficient, but laser safety requirements and costs increase
Solution Approach 1:
The patent changes the optical parameters of the system to improve efficiency and reduce light loss. By optimizing the mirror reflectivity, reducing the number of optical interfaces, and improving the overall optical path efficiency, the system achieves sufficient measurement capability with lower-powered lasers, thereby reducing laser safety requirements and costs while maintaining measurement precision.
4Reliability
If slow-working measuring devices are used, then environmental stabilization can be achieved, but measurement time increases
Solution Approach 1:
The patent employs a dynamic phase-shifting technique where the phase difference between the two light paths is intentionally introduced and varied. This allows the system to rapidly acquire multiple phase information points by dynamically adjusting the optical path difference, enabling fast measurement acquisition without requiring slow, stabilization-intensive procedures, thus reducing measurement time while maintaining reliability.
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 solution provides a cost-effective, robust, and mobile measurement system capable of handling harsh industrial environments with improved measurement area and reduced laser safety concerns, while maintaining high measurement accuracy and reliability.
Implementation Method 1
The incoming light beam passes through the diaphragm and is diffracted before it hits the mirror arrangement, where it is split into two partial beams
Implementation Method 2
Each part is directed onto a separate mirror and reflected there. One mirror is tilted by an angle β from the 45° position, which creates the desired 'shear' required for shearography.
Implementation Method 3
The two parts are then merged again in a second beam splitter, resulting in the desired interferometry. This is imaged in the camera
Data Source
AI summary
A measuring arrangement for non-destructive measurement of an object surface by interferometric measuring methods, wherein light strikes the measuring arrangement as a light beam reflected from the surface, including a diaphragm with an aperture; mirror arrangement with two mirrors having mirror surfaces; a camera lens and camera; wherein the incoming light beam passes the diaphragm and diffracts before hitting the mirror arrangement and splits and deflects into two partial beams, which reach and interfere in the camera; wherein the light beam passes the camera lens in front of the camera in beam direction; and wherein one mirror of the mirror arrangement is rotatable relative to the other; and wherein the camera includes a camera chip with a local sampling frequency and the diaphragm diffracts the incoming light beam as it passes through such that its spatial frequency corresponds at most to the maximum camera chip local sampling frequency during detection.