Adaptive Grid Width for Excimer Laser Shot Density
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Solution Overview
Problem
Existing dithering algorithms for refractive excimer lasers produce artefacts in low-density and high-density regions due to inadequate grid width selection, leading to deviations from the desired ablation profile during laser treatment.
Innovation Solution
Optimizing the grid width based on the calculated shot density of the desired ablation profile, using a dither algorithm to determine the appropriate grid width for precise placement of laser shots, ensuring a minimum of 4% and maximum of 96% occupied grid positions, and splitting high-contrast profiles into sub-profiles for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed grid width is used in dithering algorithms, then calculation speed is improved, but artefacts are produced in low-density and high-density regions
Solution Approach 1:
The patent applies dynamics by making the grid width adaptive rather than fixed. The grid width automatically adjusts based on the local shot density characteristics of the ablation profile, allowing the system to maintain high calculation speed while avoiding artefacts in different density regions. This is achieved through algorithms that calculate optimal grid widths dynamically for different portions of the treatment area.
Solution Approach 2:
The patent implements local quality by applying different grid widths to different regions of the ablation profile based on their specific shot density characteristics. Low-density regions receive larger grid widths to prevent artefacts, while high-density regions use smaller grid widths to maintain precision. This localized adaptation ensures optimal performance across the entire treatment area without compromising overall calculation efficiency.
2Manufacturing precision
If the grid width is reduced to improve profile accuracy, then artefacts are minimized, but calculation time increases
Solution Approach 1:
The system dynamically determines appropriate grid widths based on local shot density requirements rather than using a uniformly small grid width. This dynamic adaptation allows the calculation to maintain high precision where needed while using larger grid widths in other regions to reduce overall calculation time.
Solution Approach 2:
The patent changes the grid width parameter adaptively based on the shot density distribution of the ablation profile. By modifying this critical parameter locally rather than globally, the system achieves high profile accuracy in critical regions without the computational cost of using small grid widths throughout the entire treatment area.
3Loss of time
If a coarse grid is used to speed up calculation, then processing time is reduced, but shot placement precision deteriorates
Solution Approach 1:
The patent applies different grid resolutions to different regions based on their shot density characteristics. Regions requiring high shot placement precision use finer grids, while other regions use coarser grids to maintain processing speed. This localized quality approach ensures precision is maintained where critical without sacrificing overall processing efficiency.
Solution Approach 2:
The grid resolution is determined dynamically based on the specific requirements of each region of the ablation profile. The system calculates optimal grid parameters adaptively, allowing finer resolution where shot placement precision is critical and coarser resolution where it is less demanding, thereby balancing precision and processing time optimally.
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
The optimized grid width significantly reduces artefacts, ensuring a closer match between the planned and achieved ablation profiles, enhancing the precision and accuracy of laser treatments for refractive corrections like myopia and hyperopia.
Implementation Method 1
an excimer laser system for correction of vision... providing a relatively large spot size which provides a relatively large coverage of treatment area per shot
Data Source
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Figure 1C
AI summary
The invention relates to a method and apparatus for calculating a laser shot file for use in a refractive excimer laser comprising the steps of providing information with respect to a desired ablation profile, calculating the shot density of the desired ablation profile, determining a grid width of a grid being used for placing laser shots of the excimer laser on grid positions wherein the grid width is determined based on the calculated shot density of the desired ablation profile.