Laser-Chain Alignment Using Diffraction Patterns
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Solution Overview
Problem
Existing methods for aligning high energy, large-aperture laser chains are limited by the need for alignment references to be placed at specific object planes, restricting the placement and inspection locations, and are less accurate when spatial filters are used, leading to potential beam loss and damage.
Innovation Solution
The use of diffraction patterns from alignment references placed upstream and downstream of optical components allows for flexible alignment by monitoring and adjusting the position and orientation of optical components to achieve alignment, independent of image relaying requirements, using features like target windows and orthogonal elements to assess symmetry and centring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment references are placed at object planes of beam diagnostic systems, then sharp images can be obtained for alignment monitoring, but the placement locations are restricted and the system becomes complex
Solution Approach 1:
The patent replaces the mechanical/optical imaging system with a diffraction-based monitoring system. Instead of requiring alignment references to be at object planes of diagnostic systems with cameras and lenses, the invention uses diffraction patterns that can be observed directly in the beam path, eliminating the need for complex image relaying systems and enabling flexible placement anywhere in the beam path.
Solution Approach 2:
The patent introduces diffraction patterns as an intermediary between the alignment references and the monitoring process. The diffraction patterns serve as a mediator that can be observed directly without requiring the references to be at specific object planes, thus enabling flexible placement while maintaining monitoring capability.
2Measurement precision
If crosshair alignment references are used with spatial filters, then alignment can be monitored, but the images become blurred and alignment accuracy decreases
Solution Approach 1:
The patent replaces the crosshair imaging system that is sensitive to spatial filter blurring with a diffraction pattern system. The diffraction patterns are generated by the alignment references themselves and can be observed directly without being degraded by spatial filters, thereby maintaining alignment accuracy even in systems with spatial filters.
3Reliability
If multiple alignment references are placed at different locations, then alignment can be monitored at multiple points, but the system complexity and number of components increases
Solution Approach 1:
The patent makes the diffraction-based alignment reference system universal and applicable at any location in the beam path without requiring different systems for different locations. The same diffraction pattern monitoring approach can be used anywhere, reducing overall system complexity while maintaining reliable alignment monitoring throughout the laser chain.
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 method increases the flexibility in placing alignment references and improves alignment accuracy by analyzing the symmetry and centring of diffraction patterns, reducing beam loss and damage risks, and maintaining alignment even in systems with spatial filters.
Implementation Method 1
The alignment references are illuminated by the laser beam and form diffraction patterns. The diffraction patterns are monitored in order to assess the alignment of the optical component.
Data Source
AI summary
A method of aligning an optical component in a laser system using diffraction patterns of alignment references includes: placing a first alignment reference in the path of a laser beam upstream of an optical component, the first alignment reference having first reference features forming a first diffraction pattern when illuminated by the laser beam; placing a second alignment reference in the path of the laser beam downstream of the first alignment reference and the optical component, the second alignment reference having second reference features forming a second diffraction pattern when illuminated by the laser beam; illuminating the alignment references and optical component with the laser beam; monitoring the combined diffraction pattern of the reference features of the alignment references downstream of the second alignment reference; and adjusting the relative position and/or orientation of the optical component towards the combined diffraction pattern indicating alignment of the optical component to the laser beam. There is also disclosed a system of diffraction-based alignment references for aligning an optical component in a laser system.