Sub-Nanometer Coordinate Measuring Machine With Six-DOF Tracking
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Solution Overview
Problem
Existing areal surface interferometry methods for measuring optical surfaces suffer from errors due to retrace errors, non-ideal phase shifting, environmental gradients, and uncertainties in probe location, leading to measurement inaccuracies of about 100 nanometers.
Innovation Solution
A sub-nanometer coordinate measuring machine (SNCMM) with precise angular and positional orientation determination of a displacement-measuring probe, allowing for accurate topography measurement by scanning in sub-apertures and stitching overlapping regions, while minimizing environmental and structural distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If areal surface interferometry is used to measure optical surfaces, then measurement speed and accuracy are improved, but errors from retrace errors, non-ideal phase shifting, and environmental gradients increase
Solution Approach 1:
The patent replaces the mechanical interferometry system with an optical probe system that uses non-contact optical measurement. The probe measures displacement at each location using optical methods, eliminating mechanical retrace errors and phase shifting issues inherent in areal interferometry. This substitution of measurement methodology resolves the contradiction by maintaining high precision while improving reliability through elimination of systematic errors.
Solution Approach 2:
The patent divides the large optical surface into multiple sub-apertures that are measured sequentially. Each sub-aperture is measured independently using the optical probe, and the results are stitched together to form the complete topographic map. This segmentation approach reduces the impact of environmental gradients and measurement errors by localizing measurements to smaller, more stable regions, thereby improving overall measurement reliability while maintaining precision.
2Area of stationary object
If a coordinate measuring machine scans a probe across a large surface, then complete topographic coverage is achieved, but probe location uncertainties and environmental variations increase measurement errors to about 100 nanometers
Solution Approach 1:
The patent replaces the mechanical probe scanning system with an optical measurement system. The optical probe measures displacement using non-contact optical methods, eliminating mechanical positioning errors. By substituting mechanical measurement with optical measurement, the system achieves complete surface coverage while maintaining sub-nanometer precision, resolving the contradiction between coverage area and measurement precision.
Solution Approach 2:
The patent employs a monitoring system that continuously tracks the position and orientation of the optical probe during scanning. This feedback information is used to correct for any deviations from the intended measurement path, ensuring accurate location knowledge throughout the entire scan. The feedback mechanism allows the system to maintain high precision across large surfaces by compensating for real-time positioning variations.
3Area of stationary object
If the test piece is repositioned to measure different portions of the surface, then complete surface coverage is achieved, but gravity-induced shape changes occur
Solution Approach 1:
The patent replaces the mechanical repositioning approach with an optical measurement system that can measure the entire surface from a fixed position. The optical probe scans across the surface without requiring physical contact or repositioning of the test piece, eliminating gravity-induced shape changes. This substitution allows complete surface coverage while maintaining shape stability, resolving the contradiction between coverage and shape stability.
4Device complexity
If environmental conditions are not controlled, then device complexity is reduced, but temperature, pressure, and humidity gradients cause measurement errors
Solution Approach 1:
The patent replaces the mechanical interferometry system with an optical measurement system that is inherently less sensitive to environmental conditions. The optical probe measures displacement using light, which is not affected by temperature, pressure, or humidity gradients in the same way mechanical interferometry is. This substitution allows measurements to be made without complex environmental control, resolving the contradiction between device complexity and measurement precision.
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 topography measurement with sub-nanometer accuracy by compensating for environmental and structural uncertainties, ensuring precise angular and positional orientation of the probe, and generating a complete topographic map without significant shape changes in the test piece.
Implementation Method 1
Areal surface interferometry, including areal phase-measuring interferometry, has been used to measure the shape or form of optical surfaces
Implementation Method 2
The translation system is configured to move a platform coupled to the measurement probe within one or more prescribed translation areas over the target surface
Implementation Method 3
The monitoring system is configured to obtain measurements of the platform with respect to six degrees of freedom for each of the measurements of the target surface
Implementation Method 4
generate one or more portions of a topographic map of the target surface of the object based at least on the measurements of the target surface of an object from the measurement probe and corresponding ones of the measurements of the platform
Data Source
AI summary
A system includes: a measurement probe that obtains measurements of a surface of an object; a translator that moves a platform coupled to the probe within areas over the surface; a monitoring system that obtains measurements of the platform with respect to six degrees of freedom for each of the measurements of the surface by the probe; and a processing system that comprises a processor executing instructions stored in the memory to: control the translator to move the platform and the probe within each of the areas; initiate capture of each of the measurements during the movement of the platform and the measurement probe within each of the areas; and generate portions of a map of the surface based at least on the measurements of the surface and corresponding measurements of the platform with respect to six degrees of freedom for measurements of the surface in each of the areas.