Multi-Spot Raman Metrology for High-SNR Damage-Free Inspection
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Solution Overview
Problem
Optical metrology methods face challenges in achieving high signal-to-noise ratio (SNR) without damaging the workpiece, as high energy flux can cause overheating, while low energy flux requires long acquisition times, making them unreliable for fast, accurate, and damage-free quality inspection of large-scale industrial workpieces.
Innovation Solution
The use of a multi-spot-array configuration with multiple low-flux light spots, allowing for efficient heat dissipation and improved spatial resolution, reducing energy density and preventing damage to the workpiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high energy flux is used for optical metrology inspection, then signal-to-noise ratio is improved, but the workpiece is damaged due to overheating
Solution Approach 1:
The patent divides the illumination into multiple separate spots (e.g., 3-9 spots) arranged in an array pattern, where each spot delivers low enough flux to avoid damage while the collective array provides sufficient total signal. This segmentation of energy delivery is the core mechanism for resolving the contradiction between signal strength and damage prevention.
Solution Approach 2:
The patent transitions from single-spot illumination to multi-spot array illumination, adding spatial dimensionality to the energy distribution. By distributing energy across multiple spatial locations rather than concentrating it at one point, the system achieves both adequate signal levels and damage-free inspection.
2Object-affected harmful factors
If low energy flux is used to avoid damaging the workpiece, then damage is prevented, but acquisition time increases significantly
Solution Approach 1:
By segmenting the total energy flux into multiple spots, the system can use lower flux at each spot (preventing damage) while maintaining adequate total signal through the array of spots, thereby reducing acquisition time compared to single-spot low-flux methods.
Solution Approach 2:
The patent combines multiple low-flux spots into a unified illumination array that collectively provides sufficient signal strength for fast acquisition while each individual spot remains at damage-free flux levels.
3Measurement precision
If single-spot illumination is used, then spatial resolution is maintained, but heat dissipation is insufficient causing potential damage
Solution Approach 1:
The patent segments the illumination into multiple spatially separated spots, which improves heat dissipation by distributing thermal load across multiple locations while maintaining spatial resolution through the controlled arrangement and sizing of each spot in the array.
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 fast, accurate, and reliable quality inspection by preventing overheating and damage, while maintaining high SNR and spatial resolution, suitable for large-scale industrial applications.
Implementation Method 1
an optical subsystem configured and arranged to form at least one multi-spot-array, from light emanating from the at least one light source, over a test area of the tested workpiece
Implementation Method 2
at least one spectrometry device having at least one aperture, positioned at a specific relative-position in respect to the test area of the tested workpiece, wherein the optical subsystem is further arranged and configured to direct light emanating from the multi-spot-array, onto the at least one aperture of the spectrometry device, for detecting spectral characteristics of one or more spots of the multi-spot-array
Data Source
AI summary
A method for measuring characteristics of a workpiece. The method includes holding a workpiece to be tested at a specific measuring-position; forming a multi-spot-array over a test area of the workpiece, wherein said forming comprises manipulating light from at least one light source with an optical subsystem comprising a multi-spot generator; directing light emanating from the multi-spot-array towards at least one spectrometry device having an aperture; detecting Raman spectral characteristics of a plurality of spots of the multi-spot-array; and determining one or more properties of the test area of the workpiece based on the detected Raman spectral characteristics. Distribution of energy density of the multi-spot-array over the test area is configured to prevent affecting the workpiece during measurement.