Sealed Laser Machining Optics for Contamination-Resistant Imaging
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Solution Overview
Problem
Laser machining systems face issues with optical elements being sensitive to contamination, leading to heating, damage, and imaging errors due to materials like quartz glass and zinc sulfide, which are either prone to damage or cause forward scattering and birefringence.
Innovation Solution
A composite optical system with transparent protective glasses and an optical element, where the optical element is housed in an airtight interior space, minimizing exposure to contamination and using materials like quartz glass and calcium fluoride for low thermal conductivity, and sapphire or zinc sulfide for protective glasses with high thermal conductivity to prevent forward scattering and birefringence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quartz glass optical elements are used for high-power laser machining, then the optical element has good imaging properties and low cost, but it is very sensitive to dirt and contamination leading to heating and damage
Solution Approach 1:
The optical system is segmented into two functional parts: a protective optical element (window) that shields the sensitive optical element from contamination, and the sensitive optical element (lens) that performs imaging but remains protected within a sealed housing. This segmentation allows each component to fulfill its specific function without being compromised by the other's weaknesses.
Solution Approach 2:
A protective optical element (window) acts as an intermediary between the contaminated environment and the sensitive optical element. This window is positioned in the beam path before the sensitive lens, intercepting contaminants and preventing them from reaching the lens surface, thereby protecting the lens from heating and damage while allowing laser energy to pass through.
2Temperature
If zinc sulfide (ZnS) is used for optical elements, then it has good thermal conductivity, but it causes forward scattering of 2-3% of laser power heating the surroundings
Solution Approach 1:
The protective window made of ZnS serves as an intermediary component that handles the thermal management function separately from the imaging function. By placing this scattering-prone material in a non-imaging position (as a protective window rather than a focusing lens), the harmful forward scattering is directed away from the workpiece and surrounding areas, while the main imaging is performed by the protected optical element.
Solution Approach 2:
Different parts of the optical system are assigned different material properties based on their specific functions: the protective window uses ZnS for thermal conductivity, while the imaging lens uses a material with low scattering properties. This local optimization allows each component to have the ideal properties for its specific role without compromising the overall system performance.
3Reliability
If sapphire is used for optical elements, then it has acceptable thermal conductivity and less scattering than ZnS, but it is expensive and difficult to process due to high hardness
Solution Approach 1:
The optical system segments the protective function from the imaging function, allowing the use of different materials optimized for each purpose. The protective window can be made from readily available, easier-to-process materials, while the imaging lens uses precision-optical materials that require high manufacturing quality but are protected from harsh environmental conditions.
Solution Approach 2:
The protective optical element (window) is designed as a replaceable, relatively inexpensive component that can be easily replaced if contaminated or damaged. This allows the use of simpler, cheaper materials for the protective window rather than requiring expensive, difficult-to-process materials like sapphire, while the expensive imaging lens remains protected and reusable.
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 solution effectively protects optical elements from surface contamination, preventing damage and maintaining imaging quality even in high-power laser applications, while reducing forward scattering and birefringence, thus ensuring reliable and efficient laser machining.
Implementation Method 1
two protective glasses (14) that are transparent for the laser beam, the outer edges of which are enclosed in an airtight manner by a holder (16) in such a way that they form an interior space (17) with the holder (16), the optical element (12) being arranged in the interior space (17)
Implementation Method 2
optical imaging is understood to mean that the laser beam is guided onto the workpiece, for example by refraction, reflection, diffraction and/or beam shaping
Implementation Method 3
optical imaging is understood to mean that the laser beam is guided onto the workpiece, for example by refraction, reflection, diffraction and/or beam shaping
Implementation Method 4
optical imaging is understood to mean that the laser beam is guided onto the workpiece, for example by refraction, reflection, diffraction and/or beam shaping
Implementation Method 5
ZnS has good thermal conductivity... sapphire has acceptable thermal conductivity
Data Source
AI summary
An optical unit fora laser beam for laser machining of a workpiece is disclosed. With particular application to a laser beam, the optical unit may be applied to a high-power laser beam and comprise an optical element for the optical imaging of the laser beam, and two protective glasses that are transparent for the laser beam, the outer edges of which protective glasses being enclosed in an airtight manner by a holder in such a way that they form an interior space with the holder, the optical element also being arranged in the interior space. A laser machining device is also disclosed.