Optical System for Surface Shape Change Measurement
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Solution Overview
Problem
Conventional methods face challenges in accurately measuring shape changes on large, complex surfaces due to limitations in light collection efficiency and measurement accuracy, particularly when dealing with surfaces that are optically diffusive or scattering.
Innovation Solution
An optical system utilizing dual radiation sources with adjustable spectral and geometrical parameters, combined with a radiation detector and optical-wavefront-multiplier system, performs Fourier Transforms on sheared speckle patterns to determine surface shape changes by analyzing the interference of modified radiation wavefronts, allowing for improved light collection and accuracy through multiple measurements under varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used on large, complex surfaces, then the measurement process is simpler, but measurement accuracy deteriorates due to limitations in light collection efficiency
Solution Approach 1:
The patent segments the measurement process by dividing the complex surface into multiple measurement zones and using multiple radiation sources positioned at different locations. Each source measures a specific portion of the surface, and the results are combined to achieve complete surface coverage with high accuracy while maintaining efficient light collection for each segment.
Solution Approach 2:
The patent introduces temporal dimension by capturing multiple images at different time points and performing Fourier transforms on the temporal sequences. This temporal dimension allows extraction of shape information that is not accessible in single static measurements, improving measurement accuracy without requiring additional spatial light collection.
2Measurement precision
If conventional methods are used for measuring optically diffusive surfaces, then the measurement setup is simpler, but measurement accuracy deteriorates
Solution Approach 1:
The patent changes multiple parameters including radiation wavelength, incidence angle, and polarization state to optimize measurements on optically diffusive surfaces. By varying these parameters across multiple measurements and combining the results, the system achieves high measurement accuracy for challenging surfaces while managing system complexity through systematic parameter variation.
Solution Approach 2:
The patent creates multiple virtual copies of the measurement process by using Fourier transform techniques to generate synthetic views and measurements from the captured image sequences. These computational copies allow extraction of shape information that would require complex physical measurement setups, thereby improving accuracy without proportionally increasing physical system complexity.
3Measurement precision
If multiple measurements under varying conditions are performed, then measurement accuracy improves, but measurement time increases
Solution Approach 1:
The patent employs periodic modulation of radiation sources and synchronized capture of image sequences at regular time intervals. This periodic action allows efficient temporal sampling that captures all necessary information for accurate shape measurement within a compact time frame, avoiding redundant measurements while maintaining high accuracy through the periodic variation of measurement conditions.
Solution Approach 2:
The patent performs preliminary calibration and parameter optimization before the actual measurement sequence. By pre-configuring the optimal measurement conditions and preparing the data processing pipelines in advance, the system minimizes the time required during the actual measurement phase while ensuring high measurement accuracy is achieved through the pre-planned varying conditions.
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 precise measurement of in-plane and out-of-plane surface changes across complex surfaces with enhanced accuracy, reducing measurement errors and improving light collection efficiency, suitable for assessing deformations in semiconductor wafers and 3D printed parts.
Implementation Method 1
configured to determine a change of an object's shape, based on a determination of Fourier Transforms of only respectively-corresponding subportions of the first and second images formed by/at the detector
Implementation Method 2
to form at least first and second radiation wavefronts by duplicating the input radiation front, and to direct the at least first and second radiation wavefronts onto the radiation detector
Data Source
AI summary
Surface changes are estimated using multiple speckle interferograms acquired using beams incident at different angles. Beam irradiation conditions can be changed to increase signal to noise ratio with averaging, such as weighted averaging. Irradiation conditions can be varied with a tilt plate, a wedge, or by changing beam wavelengths.