Auto-focusing LIBS System with PSF-Based Focus Prediction
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Solution Overview
Problem
Existing LIBS analysis systems require multiple measurements and laser ablation events at each sampling region to achieve optimal focus, leading to increased analysis time and potential errors due to the uneven surface of samples.
Innovation Solution
A LIBS analysis system with a controller that uses a mathematical transform to calculate the optimum focus position based on measured data from other regions, reducing the need for multiple measurements and laser ablation events by correlating detector output with sample surface locations, allowing for auto-focusing without ablation at the analysis region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements and laser ablation events are performed at each sampling region to achieve optimal focus, then measurement precision is improved, but analysis time increases and productivity decreases
Solution Approach 1:
The system performs preliminary focus characterization by measuring the point spread function (PSF) at representative locations before actual analysis. This pre-acquired optical information is stored and reused to predict optimal focus positions, eliminating the need for repeated measurements at each sampling region and thereby resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The system creates a computational model (copy) of the optical system's focus characteristics through initial measurements. This model is then applied to predict focus positions at different sampling regions without requiring physical repeated measurements, thus maintaining precision while improving productivity
2Measurement precision
If multiple laser ablation events are performed at each sampling region to establish optimal focus, then measurement precision is improved, but the sample is damaged and reliability decreases
Solution Approach 1:
The system performs preliminary focus characterization at limited locations to build an optical model, then uses this model to guide subsequent analysis with minimal additional ablation. This reduces cumulative sample damage while maintaining focus precision through computational prediction rather than repeated physical probing
Solution Approach 2:
The system replaces repeated mechanical laser ablation probing with computational prediction based on pre-acquired optical data. Instead of using the laser to physically probe and damage the sample at each point to determine focus, the system calculates optimal focus positions using stored PSF data and geometric relationships
3Measurement precision
If the laser is repeatedly re-focused on uneven sample surfaces to analyze different regions, then measurement precision is maintained, but analysis time increases and productivity decreases
Solution Approach 1:
The system pre-characterizes the optical system's focus properties and stores this information for rapid retrieval. When analyzing different regions of the sample, the controller quickly calculates the appropriate focus adjustment based on the stored model and the new target location, eliminating the need for time-consuming iterative refocusing at each region 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 approach significantly reduces the number of non-analysis measurements and laser ablation events, improving analysis efficiency and accuracy by calculating the optimum focus position for each sampling region, thereby minimizing errors and analysis time.
Implementation Method 1
a high powered laser that sufficiently heats a portion of the sample to produce a plasma
Implementation Method 2
a laser configured to propagate a laser beam in a direction along an optical path through the focusing lens to be focused at the focal plane
Implementation Method 3
As the plasma cools, eventually the electrons return to their ground states. In the process, photons are emitted at wavelengths unique to the specific elements comprising the sample
Implementation Method 4
photons are emitted at wavelengths unique to the specific elements comprising the sample
Implementation Method 5
a detector having an output proportional to an intensity of incident electromagnetic radiation
Data Source
AI summary
A LIBS analysis system comprises a focusing lens arrangement having a focal plane; a laser for propagating a laser beam through the focusing lens arrangement to be focused at the focal plane; a detector for generating an output that is proportional to an intensity of incident electromagnetic radiation that is incident on the detector; a translation mechanism configured to cause a relative movement of the sample holder and the focusing lens arrangement to vary a position of the focal plane along the optical path with respect to the sample holder; and a controller configured to automatically control the translation mechanism to cause the relative movement of the sample holder and the focusing lens arrangement to achieve an optimum position at which the focal plane and an analysis region of the upper surface intersecting the optical path are at or are close to coincidence.