Wavefront Aberration Correction in Optical Inspection
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Solution Overview
Problem
In optical inspection systems, measuring wavefront aberrations in disjoint subregions of an image field leads to measurement errors due to incorrect sensor positioning, causing constant offset errors that complicate the determination of suitable adjustment processes for the imaging optical unit.
Innovation Solution
A method that approximates measurement values using a smooth function and subregion functions to correct for individual measurement errors in each subregion, allowing for the reproduction of measurement errors and the suppression of constant offset errors, thereby providing accurate and reliable correction of wavefront aberrations across the image field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If measurement is carried out in disjoint subregions of the parameter range, then measurement costs and device complexity are reduced, but measurement precision deteriorates due to constant offset errors in individual subregions
Solution Approach 1:
The patent divides the image field into multiple disjoint subregions and assigns separate subregion functions to each, allowing independent correction of offset errors in each subregion while maintaining overall measurement accuracy
Solution Approach 2:
The patent applies different types of functions to different parts of the parameter range: smooth functions for the overall variable course and subregion functions for local offset error correction, making each part serve its specific purpose
2Measurement precision
If measurement is carried out in the entire parameter range, then measurement precision is improved, but measurement costs and device complexity increase
Solution Approach 1:
The patent segments the measurement process into two stages: first measuring in disjoint subregions with simplified device setup, then correcting the measurements mathematically using smooth and subregion functions, avoiding the need for complex full-range measurement hardware
3Loss of time
If sensor positioning is performed in disjoint subregions, then measurement time is reduced, but reliability deteriorates due to incorrect positioning errors
Solution Approach 1:
The patent performs preliminary correction calculations using smooth functions and subregion functions to eliminate the effects of incorrect sensor positioning, allowing fast subregion measurements to yield reliable full-range results
Solution Approach 2:
The patent uses the measured values from subregions, combined with smooth and subregion functions, to calculate corrected values that compensate for positioning errors, creating a feedback mechanism that improves reliability
Data Source
AI summary
A method for determining a corrected variable, which depends on at least one parameter, in a parameter range of the parameter, includes carrying out a measurement, measurement values of the variable being made available in a plurality of separate and non-overlapping subranges of the parameter range; correcting measurement values of the variable using an approximation, in which measurement values of the variable are approximated with a smooth function and with subrange functions of the subranges of the parameter range. The smooth function allows reproduction of the progression of the variable over the parameter range. The subrange functions permit an individual change of the variable in the subranges. Also disclosed are methods for adjusting imaging optics of an optical system, devices for determining a corrected variable, which depends on at least one parameter in a parameter range, and methods for determining a plurality of corrected wavefront errors in an image field.