Multi-Spot Scanning Defect Detection via Acousto-Optic Interference
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Solution Overview
Problem
Current microscopy techniques, such as DIC microscopy and traveling lens acousto-optic devices, face challenges in efficiently assessing samples with topographic differences, as they struggle to maintain consistent image contrast and accurately detect defects due to variations in refractive index and surface elevation.
Innovation Solution
A system utilizing a radiation source, traveling lens optics with an acousto-optic Bragg cell and acoustic transducer to generate and scan multiple spots on a sample surface, creating a pattern of interference fringes that remains stationary despite topographic changes, allowing for robust defect detection by varying the phase and amplitude of the spots and calculating near-field radiation phase and amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DIC microscopy or traveling lens acousto-optic devices are used to observe phase variations, then features such as thin filaments and sharp interfaces can be highlighted, but consistent image contrast cannot be maintained due to topographic differences and variations in refractive index
Solution Approach 1:
The patent divides the illumination into multiple discrete spots (first, second, and third spots) that are scanned across the sample surface. This segmentation allows independent phase control of each spot, enabling the system to maintain consistent interference fringe patterns despite topographic variations in different regions of the sample.
Solution Approach 2:
The patent dynamically adjusts the phase and amplitude parameters of the acoustic pulses generated by the transducer. By varying these parameters, the system controls the relative phase and amplitude of the multiple spots, ensuring that interference fringes remain stationary and consistent across samples with different topographies and refractive indices.
2Productivity
If multiple spots are scanned over the sample surface to improve defect detection, then assessment efficiency is enhanced, but system complexity increases due to the need for precise phase and amplitude control
Solution Approach 1:
The traveling lens acousto-optic device serves multiple functions: it generates multiple spots, scans them across the sample, and controls their phase and amplitude relationships. This multi-functionality allows the system to achieve improved defect detection efficiency without requiring separate complex control systems for each function.
Solution Approach 2:
The acoustic pulses in the acousto-optic Bragg cell act as an intermediary mechanism that enables precise control of spot phase and amplitude. By modulating the acoustic pulses, the system indirectly controls the optical properties of the multiple spots, simplifying the overall control architecture while maintaining 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
This system enhances defect detection by maintaining consistent interference fringe patterns across different sample topographies, improving the accuracy and robustness of defect classification and surface assessment compared to traditional phase contrast methods.
Implementation Method 1
An acoustic transducer is coupled to one end of an acousto-optic Bragg cell. The acoustic transducer generates frequency-modulated acoustic pulses in the Bragg cell, which travel from one end of the cell to the other. The resulting spatial frequency variation of the traveling acoustic pulse causes a laser beam that passes through the pulse area to be focused onto an image plane.
Implementation Method 2
As the acoustic pulse travels from one end of the Bragg cell to the other, it acts as a traveling lens, causing the focused laser spot to be scanned across the image plane.
Implementation Method 3
collection optics, positioned to collect the radiation scattered from the first, second and third spots and to focus the collected radiation so as to generate a pattern of interference fringes
Data Source
AI summary
A system that may include a radiation source to generate a beam of coherent radiation; traveling lens optics to focus the beam to generate multiple spots on a surface of a sample and to scan the spots together over the surface; collection optics to collect the radiation scattered from the multiple spots and to focus the collected radiation to generate a pattern of interference fringes; and a detection unit to detect changes in the pattern of interference fringes.