Compact Dual-Mode Interferometer for On-Machine Metrology
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Solution Overview
Problem
Existing interferometric systems are not compact enough for on-machine metrology and require multiple instruments to measure both surface shape and roughness, which is inefficient and time-consuming.
Innovation Solution
A compact snapshot dual-mode interferometric system using optical filters to achieve dual working modes in a single, compact configuration, allowing for simultaneous measurement of surface shape and roughness without reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single interferometric system is used to measure both surface shape and roughness, then measurement efficiency is improved, but the system complexity increases
Solution Approach 1:
The patent combines surface shape measurement and surface roughness measurement functions into a single interferometric system. The system integrates two light sources (laser and LED), optical filters, and a polarization-sensitive camera to perform both measurement types simultaneously, eliminating the need for separate instruments and reconfiguration steps.
Solution Approach 2:
The interferometric system is designed with multi-functionality to measure both surface shape (using laser light) and surface roughness (using LED light) without requiring structural changes or reconfiguration. The optical filters and polarization-sensitive camera enable the system to adapt to different measurement modes automatically.
2Measurement precision
If multiple instruments are used to measure surface shape and roughness separately, then measurement accuracy is maintained, but measurement time increases
Solution Approach 1:
The system enables continuous measurement of both surface shape and roughness simultaneously in a single snapshot, eliminating the sequential measurement process. The polarization-sensitive camera captures both types of interference patterns at the same time, ensuring no loss of measurement accuracy while dramatically reducing total measurement time.
3Measurement precision
If conventional interferometric systems are designed for high precision measurement, then measurement accuracy is improved, but the system size increases
Solution Approach 1:
The patent utilizes the polarization dimension to differentiate between surface shape and roughness measurements. By employing a polarization-sensitive camera and optical filters that manipulate light polarization states, the system achieves dual-functionality without requiring physically separate measurement paths, thereby maintaining high precision while minimizing system size.
4Adaptability or versatility
If the interferometric system requires reconfiguration for different measurement modes, then measurement versatility is improved, but ease of operation deteriorates
Solution Approach 1:
The system dynamically switches between measurement modes by electronically controlling the optical filters and light sources rather than requiring physical reconfiguration. The polarization-sensitive camera and filter assembly can rapidly adapt to different measurement requirements through electronic control, maintaining versatility while significantly improving ease of operation.
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
Enables accurate and efficient on-machine measurement of both surface shape and roughness, reducing the need for multiple instruments and minimizing environmental disturbances with snapshot and fast measurements.
Implementation Method 1
The first optical filter is configured to allow the light having the first wavelength or the first range of wavelengths to reflect therefrom, and the light having the second wavelength or the second range of wavelengths to transmit therethrough for illumination of a reference optical element
Implementation Method 2
a quarter wave plate positioned to receive the light having the first polarization in the reference path after reflection from the first optical filter or a reference optical element, and to receive light having the second polarization in the test path after reflection from the object, and to produce oppositely circularly polarized light beams
Implementation Method 3
The oppositely circularly polarized light beams, upon reaching a polarization sensitive camera at an image plane of the interferometric system and formation of a plurality of interferograms, enable measurements of a surface shape or a surface roughness of the object based on interferograms produced from light from the first light source or the second light source
Data Source
AI summary
Systems, devices and methods for measuring surface roughness and surface shape of an optical element using a dual-mode interferometer are disclosed. The devices implement optical filters, with a compact form, that allows measurement of both surface characteristics without rearranging the system components. One example interferometric system includes a laser light source and a low coherence light source that alternatively provide light to a collimator, followed by a polarizer, and a polarizing beam splitter. The system further includes two optical filters, a quarter waveplate, two objectives and a reference optical component. Each light source produces a set of interferograms, where one set of interferograms is used to measure the surface shape and another set of interferograms is used to measure the surface roughness of the optical component.