Laser Ablation Spot Layout to Reduce Optical Diffraction
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Solution Overview
Problem
Laser ablation processes often result in undesirable diffraction patterns on transparent and reflective surfaces due to regular patterns of laser spots, which can be visible under magnification and affect the optical properties of the workpiece, making them unsuitable for applications where invisibility or specific optical performance is required.
Innovation Solution
Modifying the laser ablation process by adjusting scan speed, increasing laser pulse frequency, using a defocused beam, and employing non-Gaussian or flat energy profiles, along with non-parallel raster lines and index-matching fluids, to reduce the appearance of diffraction gratings and patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a regular pattern of laser spots is used for ablation, then material removal efficiency is improved, but diffraction patterns become visible on transparent and reflective surfaces
Solution Approach 1:
The patent applies asymmetry by using non-parallel raster lines at different angles for subsequent laser passes. Instead of repeating the same parallel scan pattern, the invention varies the angle and spacing of raster lines to create irregular spot distributions that eliminate regular diffraction patterns while maintaining effective material removal.
Solution Approach 2:
The invention implements dynamics by adjusting laser process parameters (scan speed, pulse frequency, spot spacing) between different passes. The raster line configuration is dynamically changed from pass to pass, with varying angles and spacings, allowing the process to adapt and prevent formation of static diffraction patterns while maintaining productivity.
2Object-affected harmful factors
If laser parameters are adjusted to reduce diffraction patterns, then optical properties are improved, but processing time increases
Solution Approach 1:
The patent applies partial action by performing multiple passes with progressively refined parameters. The first pass removes the bulk material with standard parameters, while subsequent passes use modified parameters (different angles, reduced spot spacing) to eliminate diffraction patterns. This partial application of refined parameters to specific passes balances optical quality improvement with processing time constraints.
Solution Approach 2:
The laser ablation process is segmented into multiple distinct passes, each with optimized parameters for its specific purpose. The first pass focuses on material removal, while subsequent passes focus on surface quality and diffraction pattern elimination. This segmentation allows each pass to be optimized independently, preventing the need to slow down the entire process.
3Object-affected harmful factors
If multiple laser passes with different parameters are used, then diffraction patterns are reduced, but process complexity increases
Solution Approach 1:
The invention systematically changes key laser parameters between passes: raster line angle, spot spacing, scan speed, and pulse frequency. By methodically varying these parameters according to a defined pattern (non-parallel raster lines at different angles), the process reduces diffraction patterns while maintaining manageable complexity through structured parameter variation rather than random adjustments.
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
These modifications effectively reduce the visibility and intensity of diffraction patterns by increasing overlap and irregularity in the laser spot spacing, minimizing residual material and substrate alteration, thereby enhancing the optical properties of the ablated surfaces.
Implementation Method 1
laser ablation is a process that has been used to remove material or layers of materials from workpieces
Implementation Method 2
Laser ablation processes often result in undesirable diffraction patterns on transparent and reflective surfaces due to regular patterns of laser spots
Data Source
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AI summary
A laser ablation process can be configured to reduce the appearance of or eliminate a potentially objectionable diffraction effect that can occur when a workpiece or product that has been subjected to the ablation process interacts with light. The diffraction effect can be reduced by introducing irregularity into the arrangement of overlapping laser spots during the process. Other process parameters may be modified to reduce the diffraction effect, such as laser scan speed, laser pulse frequency, the position of the focal plane of the laser, the configuration of raster lines, or the energy profile of the laser beam, for example. The process modifications and configurations are particularly useful with products including an ablated surface that is intended to reflect light or to allow light to pass therethrough as part of its function.