LADAR-Based Optical Alignment for Aspherical VUV and EUV Elements
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Solution Overview
Problem
Traditional optical alignment methods, such as interferometry, are inadequate for accurately aligning and characterizing aspherical optical elements in VUV and EUV systems due to their high precision requirements and inability to measure non-flat wavefronts.
Innovation Solution
A LADAR-based system that uses a laser source, optical coupling assembly, and detector to measure relative distances and misalignments between optical surfaces, and a beam splitter to form interference patterns for characterizing reflective optical elements, enabling precise alignment and shape determination of arbitrarily shaped optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional interferometry is used for optical alignment, then measurement capability is available for flat wavefronts, but it cannot measure aspherical optical elements with high precision
Solution Approach 1:
The patent changes the fundamental measurement parameter from interferometric phase measurement (which requires flat wavefronts) to LADAR time-of-flight or phase-shift distance measurement, which can handle arbitrary wavefront shapes. This parameter change enables measurement of aspherical elements while maintaining high precision alignment capability.
Solution Approach 2:
The patent replaces the traditional interferometric optical measurement system with a LADAR-based system that uses laser ranging technology. This substitution eliminates the requirement for flat reference wavefronts while achieving comparable or superior measurement precision for alignment and surface profiling.
2Productivity
If traditional interferometry is used, then optical alignment can be performed, but real-time monitoring and feedback control are not achievable
Solution Approach 1:
The patent implements a closed-loop feedback system where the LADAR continuously measures distances between optical surfaces, the controller compares these measurements to target values, and actuators adjust the optical elements in real-time. This feedback mechanism enables dynamic monitoring and automatic correction of alignment errors, achieving both high productivity and minimal time loss.
Solution Approach 2:
The LADAR system enables continuous real-time measurement of optical surface positions and distances, allowing the alignment process to be continuously monitored and adjusted rather than requiring discrete, time-consuming measurement cycles. This continuity eliminates idle time and accelerates the alignment process.
3Manufacturing precision
If high accuracy alignment is required for VUV and EUV optics, then image acquisition quality improves, but the complexity of alignment procedures increases
Solution Approach 1:
The LADAR-based alignment system serves multiple functions: it measures distances between optical surfaces, profiles optical element shapes, monitors alignment in real-time, and provides feedback for automatic adjustment. This multi-functionality consolidates what would otherwise require multiple separate measurement and adjustment systems, reducing overall complexity while maintaining high precision.
Solution Approach 2:
The system incorporates automatic feedback control where the controller autonomously processes LADAR measurements and commands actuators to adjust optical elements without requiring manual intervention. This self-service capability simplifies the alignment procedure by eliminating complex manual adjustment steps while achieving the required high accuracy.
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 LADAR-based system provides high-precision alignment and characterization of optical elements, including aspherical ones, with real-time monitoring and feedback control, overcoming the limitations of traditional methods by measuring distances and shapes with high accuracy.
Implementation Method 1
the measurement beam and the reference beam form an interference pattern at the surface of the scattering target
Implementation Method 2
A LADAR-based system that uses a laser source, optical coupling assembly, and detector to measure relative distances and misalignments between optical surfaces
Implementation Method 3
a beam splitter configured to split the probe beam into a reference beam and a measurement beam
Implementation Method 4
the illumination from the interference pattern is scattered by the surface of the scattering target
Data Source
AI summary
An optical alignment system includes a LADAR sub-system including: a laser source and a probe configured to deliver probe illumination from the laser source to a first optical surface of the optical system and an additional optical surface of the optical system. The probe is further configured to receive a first measurement signal from the first optical surface and an additional measurement signal from the additional optical surface of the optical system. The system also includes a detector configured to receive a first combined signal and an additional combined signal from an optical coupling assembly. The system further include a controller configured to determine a relative distance between the first optical surface and the additional optical surface based on the first combined signal or the additional combined signal.