On-axis interferometry vacuum chamber reference surface
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Solution Overview
Problem
Current interferometry systems face limitations due to optical path deflections caused by vacuum chamber windows, ambient humidity, and registration errors when switching between processing and metrology setups, leading to measurement instability and reduced throughput in optics figuring.
Innovation Solution
Implementing a dynamic on-axis interferometry system with a wavelength-shifting on-axis interferometer and a vacuum chamber that includes a reference surface between the vacuum chamber window and the surface under testing, allowing for in-situ metrology and three-surface test under vacuum to subtract optical path aberrations, thereby reducing measurement errors and environmental impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum chamber window is inserted into the measurement system to enable in-situ measurement, then measurement stability is improved by eliminating humidity effects, but optical path aberrations are introduced causing measurement errors
Solution Approach 1:
A reference surface is introduced as an intermediary element within the vacuum chamber to enable accurate measurement through the vacuum window. The reference surface serves as a mediator that allows the interferometer to measure the test surface while compensating for the optical path aberrations introduced by the vacuum window, thus maintaining both measurement stability and precision simultaneously
Solution Approach 2:
The system performs measurements at multiple wavelengths and uses computational processing to separate and remove the aberration signature of the vacuum window from the measurement data. By changing the measurement parameter (wavelength) and processing the data differently, the system can extract accurate surface figure information despite the presence of vacuum window aberrations
2Ease of manufacture
If separate processing and metrology stations are used, then figure correction can be performed, but registration errors accumulate and throughput is limited by transfer time
Solution Approach 1:
The patent combines the processing and metrology functions into a single integrated system where both the ion-beam figuring apparatus and the interferometer share the same vacuum chamber. This merging eliminates the need to transfer mirrors between separate stations, removing registration errors and increasing throughput while maintaining figure correction capability
Solution Approach 2:
The vacuum chamber is designed to serve multiple functions: it provides the vacuum environment needed for ion-beam processing while simultaneously allowing optical access for interferometric measurement. This multi-functionality enables both processing and metrology to occur in the same environment without requiring separate stations
3Ease of manufacture
If separate processing and metrology stations are used, then figure correction can be performed, but dwell time is needed for the optic to adjust to new ambient conditions
Solution Approach 1:
By combining processing and metrology in the same vacuum chamber environment, the optic remains in a stable vacuum environment throughout the entire process. This eliminates the time-consuming adjustment period needed when transferring optics between separate vacuum and ambient environment stations, as there is no environmental transition required
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 approach enables accurate, real-time surface figuring with reduced environmental influences, increased throughput, and the ability to work with reactive materials by minimizing optical path deflections and humidity effects, while maintaining the sample in a vacuum environment.
Implementation Method 1
Fizeau interferometers are one device used for such measurement applications. However, current interferometers suffer from several deficiencies.
Implementation Method 2
Insertion of extra optical surfaces into the measurement system (such as a vacuum window) will create aberrations to this wavefront.
Data Source
AI summary
Methods and related equipment for dynamic on-axis in-situ interferometry where the reference surface is positioned in an vacuum chamber. The systems use a wavelength shifting, or a phase shifting interferometer that allows the freedom to eliminate the need to step the cavity length physically with the reference surface, allowing the reference surface to be placed inside the vacuum chamber.