Optical Alignment Using Damped Least Squares and Dynamic Pixel Windows
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Solution Overview
Problem
Optical systems, particularly off-axis systems, face challenges in aligning large field of view (FOV) due to the complexity of measuring reference wavefront phase changes and determining optimal field point distribution, leading to issues with local minima in multivariate solution spaces during image quality calibration.
Innovation Solution
A method utilizing a multi-degree-of-freedom (DOF) compensator, such as a hexapod, with a damped least squares (DLS) optimization algorithm and dynamically sized pixel windows, measures ensquared energy (ES) as a merit function to iteratively align the optical system, avoiding local minima and achieving global optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of field points are measured to align large FOV optical systems, then measurement completeness is improved, but measurement complexity and time consumption increase
Solution Approach 1:
The patent segments the field of view into multiple discrete field points (e.g., on-axis and off-axis points) and measures them independently. This allows the large FOV alignment problem to be broken down into manageable measurements at specific locations, achieving comprehensive coverage without measuring every possible point uniformly.
Solution Approach 2:
The patent applies different measurement strategies to different regions of the field. Off-axis field points are measured with specific attention to aberration characterization, while on-axis points provide reference wavefront phase. This localized approach ensures appropriate measurement density and type for each region's specific alignment requirements.
2Ease of operation
If only one on-axis field point is measured, then measurement simplicity is improved, but alignment accuracy deteriorates due to insufficient information
Solution Approach 1:
The patent transitions from measuring only one dimension (on-axis point) to measuring multiple dimensions by incorporating off-axis field points. This dimensional expansion provides additional information about wavefront aberrations and compensator performance, enabling accurate alignment characterization without excessive measurement complexity.
Solution Approach 2:
The patent makes the field point measurement system multi-functional by using the same measurement infrastructure to characterize both on-axis wavefront phase and off-axis aberrations. This universal approach allows a single measurement system to provide comprehensive alignment information across the entire field of view.
3Ease of operation
If compensator motion changes only wavefront focus in on-axis systems, then measurement simplicity is improved, but measurement completeness deteriorates for off-axis systems with additional aberrations
Solution Approach 1:
The patent implements a feedback mechanism where measured wavefront phase and aberration data are used to characterize compensator performance across different field points. This feedback loop allows the system to account for the complex interactions between compensator motion and wavefront changes, accurately characterizing off-axis aberrations while maintaining measurement feasibility.
Data Source
AI summary
A method and a system for optimizing the alignment of an optical system, such as a telescope, using a multi-degree-of freedom (DOF) actuator/hexapod and star field images. The method iteratively adjusts the hexapod in all DOFs using the damped least squares (DLS) optimization algorithm and dynamically changes the size of pixel windows to measure ensquared energy (ES) as a closed loop feedback.