Geometric Phase Plate Beam Steering for Shearography Motion Compensation
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Solution Overview
Problem
Shearography from a moving platform faces challenges in motion compensation, leading to errors due to the movement of the transmission assembly and receiver, which current mechanical and mathematical solutions often increase the size, weight, and cost of systems while introducing optical distortion.
Innovation Solution
The use of transmissive geometric phase plate pairs in a laser transmission assembly for beam steering, allowing for compact and adjustable systems that maintain beam coherence and reduce parallax errors, replacing Risley prism pairs and movable mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical solutions such as movable mirrors or Risley prisms are used for motion compensation, then beam steering capability is improved, but device complexity and system size increase
Solution Approach 1:
The patent replaces mechanical beam steering components (movable mirrors, Risley prisms) with an optical phase modulation system using geometric phase plates. This substitution eliminates moving parts while achieving the same beam steering function through optical phase manipulation, directly resolving the contradiction between beam steering capability and device complexity
Solution Approach 2:
The patent changes the operational parameter from mechanical position adjustment to optical phase modulation. By controlling the phase distribution across the beam profile using geometric phase plates, the system achieves beam steering without mechanical movement, reducing complexity while maintaining steering adaptability
2Adaptability or versatility
If mechanical components such as reflective beam splitters are used for motion compensation, then beam direction control is improved, but laser output power is reduced
Solution Approach 1:
The patent replaces reflective beam splitters with transmissive geometric phase plates. This substitution eliminates the need for reflective components that absorb or scatter laser energy, thereby maintaining higher laser output power while achieving the same beam direction control function
Solution Approach 2:
The patent applies local phase modulation across different regions of the beam profile using geometric phase plates. Each region of the plate imparts a specific phase shift to steer the beam in the desired direction, achieving precise directional control without the energy losses associated with reflective components
3Adaptability or versatility
If Risley prisms are used for beam steering, then steering angle is improved, but system size and weight increase
Solution Approach 1:
The patent replaces heavy mechanical Risley prisms with lightweight geometric phase plates. The phase plates achieve the same beam steering function through optical phase manipulation rather than mechanical rotation of heavy prism assemblies, dramatically reducing system weight while maintaining full steering angle capability
Solution Approach 2:
The patent transitions from mechanical rotation in three-dimensional space to two-dimensional phase modulation across the beam profile. This dimensional change allows the same steering functionality to be achieved with planar phase plates instead of volumetric rotating prisms, reducing weight while preserving steering angles
4Adaptability or versatility
If movable mirrors are used for motion compensation, then beam steering flexibility is improved, but measurement precision is reduced due to parallax errors
Solution Approach 1:
The patent replaces movable mirrors with fixed geometric phase plates that modulate the beam phase optically. This substitution eliminates mechanical movement entirely, preventing the introduction of parallax errors that occur when mirrors are repositioned, while maintaining full beam steering flexibility through phase control
Solution Approach 2:
The patent applies the desired phase modulation in advance using static geometric phase plates before the beam enters the measurement area. By pre-steering the beam through phase manipulation rather than moving components during measurement, the system maintains measurement precision while achieving steering flexibility
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 solution provides a compact, adjustable, and cost-effective method for motion compensation in shearography, maintaining beam coherence and reducing errors associated with platform motion, while enabling precise control of illumination patterns.
Implementation Method 1
at least one pair of geometric phase (GP) plates; wherein the at least one pair of GP plates are operable to steer the first laser beam pulse away from a midline axis of the transmission assembly in a first direction and to steer the second laser beam pulse away from the midline axis of the transmission assembly in a second direction
Implementation Method 2
a polarizing beam splitter operable to direct a first laser beam pulse and a subsequent second laser beam pulse through a series of optical components within the transmission assembly
Data Source
AI summary
A laser transmission assembly for shearography and related systems utilizing transmissive geometric phase plate pairs in place of Risley prism pairs or movable mirrors therein. Transmissive geometric phase plates provide for a system that is more compact than systems utilizing mirrors or Risley prism pairs while maintaining or improving the adjustability of the system and further offering beamshaping to provide desired illumination patterns.