Pulse-Multiplexed Optical Inspection for Low-Damage Imaging
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Solution Overview
Problem
Existing optical inspection systems using short-duration, high-intensity light sources risk damaging samples due to potential damage from high-intensity pulses, and they struggle with speckle contrast issues during inspections.
Innovation Solution
The use of pulse multiplexing techniques with optical couplers and delay loops to generate multiple low-intensity light pulses at uniform intervals, combined with optical path multiplication systems to reduce speckle contrast, ensuring efficient and safe sample inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If short-duration, high-intensity light sources are used for optical inspection, then inspection speed and accuracy are improved, but sample damage risk increases
Solution Approach 1:
The patent divides a single high-intensity light pulse into multiple lower-intensity pulses using optical couplers and delay loops. Each optical coupler splits the light into multiple paths with different time delays, creating a sequence of pulses that maintain total energy while reducing peak intensity, thereby preventing sample damage while preserving inspection effectiveness
Solution Approach 2:
The patent employs periodic pulsed illumination with carefully controlled time intervals between pulses. The delay loops create specific time spacing between pulses, allowing the sample to recover between exposures while maintaining high overall inspection throughput through rapid sequential scanning
2Measurement precision
If short-duration, high-intensity light sources are used for optical inspection, then inspection accuracy is improved, but speckle contrast increases
Solution Approach 1:
The patent segments the coherent light pulse into multiple temporal modes using delay loops, creating several lower-intensity pulses with different time delays. This temporal segmentation reduces speckle contrast by averaging multiple independent speckle patterns while maintaining the total photon flux needed for high-precision measurement
Solution Approach 2:
The patent introduces temporal dynamics by creating a sequence of time-spaced pulses rather than a single static pulse. The varying time delays create dynamic speckle patterns that can be averaged or processed to reduce contrast, while the rapid succession maintains inspection speed and accuracy
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 allows for fast and accurate sample inspection without damaging the samples, while effectively reducing speckle contrast, thereby improving the reliability and precision of optical inspections in manufacturing processes.
Implementation Method 1
an illumination subsystem to illuminate a sample, the illumination subsystem having a pulsed light source to generate a plurality of source light pulses
Implementation Method 2
each of the plurality of optical loops deploying an optical coupler that directs a first portion of a light interacting with the optical coupler on an optical path to a sample
Implementation Method 3
provides a second portion of the light interacting with the optical coupler as an input into a next optical loop
Data Source
AI summary
Implementations disclosed describe, among other things, a sample inspection system that includes an illumination subsystem to illuminate a sample with a plurality of time-spaced light pulses generated, using a pulse multiplexing system, from a source light pulse. The pulse multiplexing system includes a plurality of optical loops, each deploying an optical coupler that outputs a first portion of incident light to a sample and provides a second portion of incident light as an input into the next optical loop. The sample inspection system further includes a collection subsystem to collect a portion of light generated upon interaction of the plurality of time-spaced light pulses with the sample, and a light detection subsystem to detect the collected portion of light.