Glass Laser Machining With Interlaced Raster Scanning
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Solution Overview
Problem
Traditional machining methods for glass materials, such as grinding and precision moulding, are limited in shaping capabilities and thermal-driven processes face challenges with thermal accumulation, leading to rough surfaces and inefficiencies in producing high-quality aspheric and freeform optics.
Innovation Solution
The implementation of an interlaced raster scanning technique in laser-based machining, using ultrashort pulsed lasers with overlapping scan lines and a subsequent CO2 laser polishing step, allows for increased machining depth and surface quality while mitigating thermal accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional thermal-driven machining methods are used on glass materials, then material removal is achieved, but thermal accumulation occurs leading to rough surfaces and reduced machining quality
Solution Approach 1:
The patent employs periodic pulsed laser action instead of continuous thermal processing. The laser delivers energy in discrete pulses with controlled duration and intervals, allowing thermal diffusion between pulses and preventing heat accumulation. This periodic energy delivery enables precise material removal while maintaining surface quality and avoiding thermal damage to the glass substrate.
2Productivity
If conventional laser machining with sequential raster scanning is used, then material is removed efficiently, but thermal accumulation along the scan path degrades surface quality
Solution Approach 1:
The patent implements periodic pulsed laser operation during raster scanning, where the laser is activated in periodic pulses rather than continuously. This allows thermal diffusion between pulses even during scanning, preventing heat accumulation along the scan path while maintaining high material removal rates and surface quality.
Solution Approach 2:
The patent applies preliminary action by performing multiple passes with decreasing step sizes. Initial passes remove the bulk material with larger step sizes, followed by subsequent passes with finer steps to refine the surface. This staged approach achieves both high productivity in early passes and high surface quality in final passes.
3Productivity
If aggressive material removal rates are used to increase productivity, then machining speed improves, but surface roughness increases and additional polishing is required
Solution Approach 1:
The patent applies preliminary action by performing multiple passes with decreasing step sizes. Initial passes remove the bulk material with larger step sizes, followed by subsequent passes with finer steps to refine the surface. This staged approach achieves both high productivity in early passes and high surface quality in final passes, reducing or eliminating the need for additional polishing.
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 enhances machining efficiency, surface smoothness, and depth control, achieving surface roughness in the range of 0.4 µm to 100 nm, suitable for high-quality optical elements without the need for tooling or mask writing.
Implementation Method 1
Laser based direct write techniques using COz, excimer and ultrashort laser pulses have all been used to machine fused silica glass substrates
Implementation Method 2
a subsequent CO2 laser polishing step, allows for increased machining depth and surface quality while mitigating thermal accumulation
Data Source
Figure 1~2
Figure 3
Figure 4(a)~6(b)
AI summary
A direct write laser based machining process wherein a laser beam is controlled to machine a glass material in an interlaced raster scan pattern. An embodiment of machining a glass substrate to form an optical element is described. An ultrashort pulsed laser is used for machining and smoothing fused silica, followed by CO2 laser polishing. High speed and high quality machining is possible using this approach, which allows efficient use of high laser repetition rates.