Optical Metrology Transfer Function Alignment
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Solution Overview
Problem
Existing methods for approximating imaging properties of optical production systems to those of optical measurement systems focus on minimizing wavefront differences, which is not effective in improving accuracy, especially when considering illumination settings, leading to suboptimal results in emulating 3D aerial images.
Innovation Solution
The method involves minimizing the deviation of transfer functions between the optical production and measurement systems, taking into account the illumination setting, allowing for object-independent adjustments of components to achieve desired imaging properties, and using adjustable components with multiple degrees of freedom to optimize the approximation, including the use of lookup tables for various illumination settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wavefront difference minimization is used to approximate imaging properties, then the approximation process is simple, but the accuracy of imaging property approximation deteriorates
Solution Approach 1:
The patent changes the optimization parameter from wavefront difference to transfer function deviation. The transfer function incorporates both wavefront information and illumination setting (illumination angle distribution), thereby improving approximation accuracy while maintaining a systematic approach to the optimization process
Solution Approach 2:
The patent adds the illumination setting dimension to the approximation process. By incorporating illumination angle distribution into the transfer function, the method moves beyond single-parameter wavefront optimization to a multi-dimensional optimization that includes both wavefront and illumination characteristics, resolving the accuracy-simplicity contradiction
2Measurement precision
If illumination setting is taken into account in the approximation method, then the imaging property approximation accuracy improves, but the complexity of the approximation process increases
Solution Approach 1:
The patent creates a universal approximation method that works for different object types (real objects and weak objects) by using object-independent transfer function optimization. The transfer function-based approach with illumination setting consideration provides a multi-functional framework that handles various imaging scenarios without requiring separate optimization procedures for each object type
Solution Approach 2:
The patent replaces complex iterative imaging simulations with a direct transfer function optimization approach. By formulating the approximation as a transfer function deviation minimization problem that incorporates illumination settings, the method substitutes cumbersome computational mechanics with a more efficient mathematical optimization framework
3Adaptability or versatility
If object-independent approximation is used, then the adjustment position leads to desired approximation for all objects of a class, but the approximation cannot capture object-specific imaging variations
Solution Approach 1:
The patent introduces dynamic adaptability by allowing the illumination setting to be adjusted according to different object classes while maintaining object-independent transfer function optimization. The method dynamically adapts to different imaging scenarios through illumination parameter selection rather than requiring complete re-optimization for each object, balancing universality with precision
Data Source
AI summary
For approximating imaging properties of an optical production system which images an object to imaging properties of an optical measurement system when imaging the object, which imaging properties arise from an adjustment displacement of at least one component (Mi) of the optical measurement system, the following procedure is carried out: A production transfer function of the imaging is determined by the production system as a target transfer function. The production transfer function depends on an illumination setting for an object illumination. This determination is implemented for a target illumination setting. Furthermore, a measurement transfer function of the imaging is determined by the measurement system as an actual transfer function. The measurement transfer function likewise depends on the illumination setting for the object illumination. This determination is also implemented for the target illumination setting. An adjustment position ({right arrow over (a)}) of the at least one adjustment component (Mi) of the measurement system is varied. This is implemented for minimizing a deviation of the production transfer function from the measurement transfer function. This results in an improvement of an accuracy of an approximation of imaging properties of the optical production system to properties of the optical measurement system, which can be part of a metrology system, in particular.